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Chicago White Sox
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The Chicago White Sox are an American professional baseball team based in Chicago. The White Sox compete in Major League Baseball (MLB) as a member club of the American League (AL) Central Division. The club plays its home games at Rate Field, which is located on Chicago's South Side. They are one of two MLB teams based in Chicago, alongside the National League (NL)’s Chicago Cubs.
The White Sox originated in the Western League, founded as the Sioux City Cornhuskers in 1894, moving to Saint Paul, Minnesota, as the St. Paul Saints, and ultimately relocating to Chicago in 1900. The Chicago White Stockings were one of the American League's eight charter franchises when the AL asserted major league status in 1901. The team, which shortened its name to the White Sox in 1904, originally played their home games at South Side Park before moving to Comiskey Park in 1910, where they played until
1990. They moved into their current home, which was originally also known as Comiskey Park like its predecessor and later carried sponsorship from U.S. Cellular, for the 1991 season.
The White Sox won their first World Series, the 1906 World Series against the Cubs, with a defense-oriented team dubbed "the Hitless Wonders", and later won the 1917 World Series against the New York Giants. Their next appearance, the 1919 World Series, was marred by the Black Sox Scandal in which eight members of the White Sox were found to have conspired with gamblers to fix games and lose the World Series to the Cincinnati Reds. In response, the new Commissioner of Baseball, Kenesaw Mountain Landis, banned the players from the league for life. The White Sox have only made two World Series appearances since the scandal. The first came in , where they lost to the Los Angeles Dodgers, before they finally won their third championship in against the Houston Astros. The 88 seasons it took the White Sox to win the World Series stands as the longest MLB championship drought in the American League, and the second longest in both leagues, to the Cubs' 108 seasons.
From 1901 to 2024, the White Sox have an overall win-loss record of ().
==History==
The White Sox originated as the Sioux City Cornhuskers of the Western League, a minor league under the parameters of the National Agreement with the National League. In 1894, Charles Comiskey bought the Cornhuskers and moved them to St. Paul, Minnesota, where they became the St. Paul Saints. In 1900, with the approval of Western League president Ban Johnson, Charles Comiskey moved the Saints into his hometown neighborhood of Armour Square, where they became the Chicago White Stockings, the former name of Chicago's National League team, the Orphans (now the Chicago Cubs).
In 1901, the Western League broke the National Agreement and became the new major league American League. The first season in the AL ended with a White Stockings championship. However, that would be the end of the season, as the World Series did not begin until 1903. The franchise, now known as the Chicago White Sox, made its first World Series appearance in 1906, beating the crosstown Cubs in six games.
The White Sox won a third pennant and a second World Series in 1917, beating the New York Giants in six games with help from stars Eddie Cicotte and "Shoeless" Joe Jackson. The Sox were heavily favored in the 1919 World Series, but lost to the Cincinnati Reds in eight games. Huge bets on the Reds fueled speculation that the series had been fixed. A criminal investigation went on in the 1920 season, and although all players were acquitted, commissioner Kenesaw Mountain Landis banned eight of them for life, in what was known as the Black Sox Scandal. This set the franchise back, as they did not win another pennant for 40 years.
The White Sox did not finish in the upper half of the American League again until after founder Charles Comiskey died and passed ownership of the club to his son, J. Louis Comiskey. They finished in the upper half most years between 1936 and 1946, under the leadership of manager Jimmy Dykes, with star shortstop Luke Appling (known as "Ol' Aches and Pains") and pitcher Ted Lyons, who both had their numbers 4 and 16 retired.
After J. Louis Comiskey died in 1939, ownership of the club was passed down to his widow, Grace Comiskey. The club was later passed down to Grace's children Dorothy and Chuck in 1956, with Dorothy selling a majority share to a group led by Bill Veeck after the 1958 season. Veeck was notorious for his promotional stunts, attracting fans to Comiskey Park with the new "exploding scoreboard" and outfield shower. In 1961, Arthur Allyn, Jr. briefly owned the club before selling to his brother John Allyn.
From 1951 to 1967, the White Sox had their longest period of sustained success, scoring a winning record for 17 straight seasons. Known as the "Go-Go White Sox" for their tendency to focus on speed and getting on base versus power hitting, they featured stars such as Minnie Miñoso, Nellie Fox, Luis Aparicio, Billy Pierce, and Sherm Lollar. From 1957 to 1965, the Sox were managed by Al López. The Sox finished in the upper half of the American League in eight of his nine seasons, including six years in the top two of the league. In 1959, the White Sox ended the New York Yankees' dominance over the American League, and won their first pennant since the ill-fated 1919 campaign. Despite winning game one of the 1959 World Series 11–0, they fell to the Los Angeles Dodgers in six games.
During the late 1960s and 1970s, the White Sox struggled to win games and attract fans. The team played a total of 20 home games at Milwaukee County Stadium in the 1968 and 1969 seasons. Allyn and Bud Selig agreed to a handshake deal that would give Selig control of the club and move them to Milwaukee, but it was blocked by the American League. Selig instead bought the Seattle Pilots and moved them to Milwaukee, where they would become the Milwaukee Brewers, putting enormous pressure on the American League to place a team in Seattle. A plan was in place for the Sox to move to Seattle and for Charlie Finley to move his Oakland A's to Chicago. However, the city had a renewed interest in the Sox after the 1972 season, and the American League instead added the expansion Seattle Mariners. The 1972 White Sox had the lone successful season of this era, as Dick Allen wound up winning the American League MVP award. Bill Veeck returned as owner of the Sox in 1975, and despite not having much money, they managed to win 90 games in 1977, with a team known as the "South Side Hitmen".
However, the team's fortunes plummeted afterwards, plagued by 90-loss teams and scarred by the notorious 1979 Disco Demolition Night promotion. Veeck was forced to sell the team, rejecting offers from ownership groups intent on moving the club to Denver and eventually agreeing to sell it to Ed DeBartolo, the only prospective owner who promised to keep the White Sox in Chicago. However, DeBartolo was rejected by the owners, and the club was then sold to a group headed by Jerry Reinsdorf and Eddie Einhorn. The Reinsdorf era started off well, with the team winning their first division title in 1983, led by manager Tony La Russa and stars Carlton Fisk, Tom Paciorek, Ron Kittle, Harold Baines, and LaMarr Hoyt. During the 1986 season, La Russa was fired by announcer-turned-general manager Ken Harrelson. La Russa went on to manage in six World Series (winning three) with the Oakland A's and St. Louis Cardinals, ending up in the Hall of Fame as the second-winningest manager of all time.
The White Sox struggled for the rest of the 1980s, as Chicago fought to keep them in town. Reinsdorf wanted to replace the aging Comiskey Park, and sought public funds to do so. When talks stalled, a strong offer was made to move the team to St. Petersburg, Florida. Funding for a new ballpark was approved in an 11th-hour deal by the Illinois State Legislature on June 30, 1988, with the stipulation that it had to be built on the corner of 35th and Shields, across the street from the old ballpark, as opposed to the suburban ballpark the owners had designed. The new ballpark opened in 1991 under the name new Comiskey Park. The park, renamed in 2003 as U.S. Cellular Field and in 2016 as Guaranteed Rate Field, underwent many renovations in the early 2000s to give it a more retro feel. In December 2024, it was renamed Rate Field when Guaranteed Rate rebranded as Rate.
The White Sox were fairly successful in the 1990s and early 2000s, with 12 winning seasons from 1990 to 2005. First baseman Frank Thomas became the face of the franchise, ending his career as the White Sox's all-time leader in runs, doubles, home runs, total bases, and walks. Other major players included Robin Ventura, Ozzie Guillén, Jack McDowell, and Bobby Thigpen. The Sox won the West division in 1993, and were in first place in 1994, when the season was canceled due to the 1994 MLB Strike.
In 2004, Ozzie Guillén was hired as manager of his former team. After finishing second in 2004, the Sox won 99 games and the Central Division title in 2005, behind the work of stars Paul Konerko, Mark Buehrle, A. J. Pierzynski, Joe Crede, and Orlando Hernández. They started the playoffs by sweeping the defending champion Boston Red Sox in the ALDS, and beat the Angels in five games to win their first pennant in 46 years, due to four complete games by the White Sox rotation. The White Sox went on to sweep the Houston Astros in the 2005 World Series, giving them their first World Championship in 88 years.
Guillén had marginal success during the rest of his tenure, with the Sox winning the Central Division title in 2008 after a one-game playoff with the Minnesota Twins. Guillén left the White Sox after the 2011 season and was replaced by former teammate Robin Ventura. The White Sox finished the 2015 season, their 115th in Chicago, with a 76–86 record, a three-game improvement over 2014. The White Sox recorded their 9,000th win in franchise history by the score of 3–2 against the Detroit Tigers on September 21, 2015. Ventura returned in 2016, with a young core featuring José Abreu, Adam Eaton, José Quintana, and Chris Sale. Ventura resigned after the 2016 season, in which the White Sox finished 78–84. Rick Renteria, the 2016 White Sox bench coach, was promoted to the role of manager.
Prior to the start of the 2017 season, the White Sox traded Sale to the Boston Red Sox and Eaton to the Washington Nationals for prospects including Yoán Moncada, Lucas Giolito and Michael Kopech, signaling the beginning of a rebuilding period. During the 2017 season, the White Sox continued their rebuild when they made a blockbuster trade with their crosstown rival, the Chicago Cubs, in a swap that featured the Sox sending pitcher José Quintana to the Cubs in exchange for four prospects headlined by outfielder Eloy Jiménez and pitcher Dylan Cease. This was the first trade between the White Sox and Cubs since the 2006 season.
During the 2018 season, relief pitcher Danny Farquhar suffered a brain hemorrhage while he was in the dugout between innings. Farquhar remained out of action for the rest of the season and just recently got medically cleared to return to baseball, despite some doctors doubting that he would make a full recovery. Also occurring during the 2018 season, the White Sox announced that the club would be the first Major League Baseball team to entirely discontinue use of plastic straws, in ordinance with the "Shedd the Straw" campaign by Shedd Aquarium. The White Sox broke an MLB record during their 100-loss campaign of 2018, but broke the single-season strikeout record in only a year after the Milwaukee Brewers broke the record in the 2017 season. On December 3, 2018, head trainer Herm Schneider retired after 40 seasons with the team; his new role will be as an advisor on medical issues pertaining to free agency, the amateur draft and player acquisition. Schneider will also continue to be a resource for the White Sox training department, including both the major and minor league levels.
On August 25, 2020, Lucas Giolito recorded the 19th no-hitter in White Sox history, and the first since Philip Humber's Perfect Game in 2012. Giolito struck out 13 and threw 74 of 101 pitches for strikes. He only allowed one baserunner, which was a walk to Erik González in the fourth inning. In 2020, the White Sox clinched a playoff berth for the first time since 2008, with a record 35–25 in the pandemic-shortened season, but lost to the Oakland Athletics in three games during the Wild Card Series. The White Sox also made MLB history by being the first team to go undefeated against left-handed pitching, with a 14–0 record. At the end of the season, Renteria and longtime pitching coach Don Cooper were both fired. Jose Abreu became the 4th different White Sox player to win the AL MVP joining Dick Allen, Nellie Fox, and Frank Thomas. During the 2021 offseason, the White Sox brought back Tony La Russa as their manager for 2021. At the age of 76 when hired, La Russa became the oldest active manager in MLB.
On April 14, 2021, pitching against the Cleveland Indians, Carlos Rodon recorded the team's 20th no-hitter. Rodon retired the first 25 batters he faced and was saved by an incredible play at first base by first baseman Jose Abreu to get the first out in the 9th before hitting Roberto Pérez which was the only baserunner Rodon allowed. Rodon struck out seven and threw 75 of 114 pitches for strikes. On June 6, 2021, the White Sox beat the Detroit Tigers 3–0. This also had Tony La Russa winning his 2,764th game as manager passing John McGraw for 2nd on the all-time managerial wins list. On August 12, 2021, the White Sox faced New York Yankees in the first ever Field of Dreams game in Dyersville, Iowa. The White Sox won the game 9–8 on a walk-off two-run Home Run by Tim Anderson. The homer was the 15th walk-off home run against the Yankees in White Sox history; the first being Shoeless Joe Jackson on July 20, 1919, whose character featured in the movie Field of Dreams. On September 23, 2021, the White Sox clinched the American League Central Division for the first time since 2008 against the Cleveland Indians.
In 2024, the White Sox tied a 14-game losing streak, then proceeded to have a 21-game losing streak from July 10 to August 5. They became the 7th team all time, and the first since the 1988 Baltimore Orioles to lose 20 consecutive games. On September 1, the White Sox set a new franchise record for losses at 107 following a 2–0 loss to the New York Mets. They are also the first team since the 1965 Mets to have 3 separate 10 or more game losing streaks in one season. On September 27, the White Sox lost their 121st game of the season, surpassing the 1962 Mets for the most losses in modern MLB history.
==Ballparks==
In the late 1980s, the franchise threatened to relocate to Tampa Bay (as did the San Francisco Giants), but frantic lobbying on the part of the Illinois governor James R. Thompson and state legislature resulted in approval (by one vote) of public funding for a new stadium. Designed primarily as a baseball stadium (as opposed to a "multipurpose" stadium), the new Comiskey Park (redubbed U.S. Cellular Field, often nicknamed "The Cell", in 2003 and Guaranteed Rate Field in 2016 (later renamed to Rate Field following a rebrand in 2024), after mortgage company Guaranteed Rate) was built in a 1960s style, similar to Dodger Stadium and Kauffman Stadium. There were ideas for other stadium designs submitted to bring a more neighborhood feel, but ultimately they were not selected. The park opened in 1991 to positive reaction, with many praising its wide-open concourses, excellent sight lines, and natural grass (unlike other stadiums of the era, such as Rogers Centre in Toronto). The park's inaugural season drew 2,934,154 fans — at the time, an all-time attendance record for any Chicago baseball team.
In recent years, money accrued from the sale of naming rights to the field has been allocated for renovations to make the park more aesthetically appealing and fan-friendly. Notable renovations of early phases included reorientation of the bullpens parallel to the field of play (thus decreasing slightly the formerly symmetrical dimensions of the outfield); filling seats in up to and shortening the outfield wall; ballooning foul-line seat sections out toward the field of play; creating a new multitiered batter's eye, allowing fans to see out through one-way screens from the center-field vantage point, and complete with concession stand and bar-style seating on its "fan deck"; and renovating all concourse areas with brick, historic murals, and new concession stand ornaments to establish a more friendly feel. The stadium's steel and concrete were repainted dark gray and black. In 2016, the scoreboard jumbotron was replaced with a new Mitsubishi Diamondvision HDTV screen.
The top quarter of the upper deck was removed in 2004, and a black wrought-metal roof was placed over it, covering all but the first eight rows of seats. This decreased seating capacity from 47,098 to 40,615; 2005 also had the introduction of the Scout Seats, redesignating (and reupholstering) 200 lower-deck seats behind home plate as an exclusive area, with seat-side waitstaff and a complete restaurant located underneath the concourse. The most significant structural addition besides the new roof was 2005's FUNdamentals Deck, a multitiered structure on the left-field concourse containing batting cages, a small Tee Ball field, speed pitch, and several other children's activities intended to entertain and educate young fans with the help of coaching staff from the Chicago Bulls/Sox Training Academy. This structure was used during the 2005 American League playoffs by ESPN and the Fox Broadcasting Company as a broadcasting platform.
Designed as a seven-phase plan, the renovations were completed before the 2007 season with the seventh and final phase. The most visible renovation in this final phase was replacing the original blue seats with green seats. The upper deck already had new green seats put in before the beginning of the 2006 season. Beginning with the 2007 season, a new luxury-seating section was added in the former press box. This section has amenities similar to those of the Scout Seats section. After the 2007 season, the ballpark continued renovation projects despite the phases being complete. In July 2019, the White Sox extended the netting to the foul pole.
===Previous ballparks===
The St. Paul Saints first played their games at Lexington Park. When they moved to Chicago's Armour Square neighborhood, they began play at the South Side Park. Previously a cricket ground, the park was located on the north side of 39th Street (now called Pershing Road) between South Wentworth and South Princeton Avenues. Its massive dimensions yielded few home runs, which was to the advantage of the White Sox's Hitless Wonders teams of the early 20th century.
After the 1909 season, the Sox moved five blocks to the north to play in the new Comiskey Park, while the 39th Street grounds became the home of the Chicago American Giants of the Negro leagues. Billed as the Baseball Palace of the World, it originally held 28,000 seats and eventually grew to hold over 50,000. It became known for its many odd features, such as the outdoor shower and the exploding scoreboard. When it closed after the 1990 season, it was the oldest ballpark still in Major League Baseball.
===Spring-training ballparks===
The White Sox have held spring training in:
Excelsior Springs, Missouri (1901–1902)
Mobile, Alabama (1903);
Marlin Springs, Texas (1904)
New Orleans (1905–1906)
Mexico City, Mexico (1907)
Los Angeles (1908)
San Francisco (Recreation Park, 1909–1910)
Mineral Wells, Texas (1911, 1916–1919)
Waco, Texas (1912, 1920);
Paso Robles, California (1913–1915)
Waxahachie, Texas (1921)
Seguin, Texas (1922–1923)
Winter Haven, Florida. (1924)
Shreveport, Louisiana (1925–1928)
Dallas (1929)
San Antonio (1930–1932)
Pasadena, California (1933–1942, 1946–1950)
French Lick, Indiana (1943–1944)
Terre Haute, Indiana (1945)
Palm Springs, California (Palm Springs Stadium, 1951)
El Centro, California (1952–1953);
Tampa, Florida (1954–1959, Plant Field, 1954, Al Lopez Field 1955–1959)
Sarasota, Florida (1960–1997; Payne Park Ed Smith Stadium 1989–97).
Tucson, Arizona (Tucson Electric Park, 1998–2008, Cactus League, shared with Arizona Diamondbacks)
Phoenix, Arizona (Camelback Ranch, 2009–present)
On November 19, 2007, the cities of Glendale and Phoenix, Arizona, broke ground on a new Cactus League spring-training facility. Camelback Ranch, the $76 million, two-team facility, is the home of both the White Sox and the Los Angeles Dodgers for their spring training, featuring state-of-the-art baseball facilities and an over 10,000-seat stadium. The facility is also home to amenities such as 118,000 sq ft. of clubhouse space, 13 full fields, citrus groves, and a large lake and river system stocked with fish running throughout the complex.
==Logos and uniforms==
Over the years, the White Sox have become noted for many of their uniform innovations and changes. In 1960, they became the first team in the major sports to put players' last names on jerseys for identification purposes.
In 1912, the White Sox debuted a large "S" in a Roman-style font, with a small "O" inside the top loop of the "S" and a small "X" inside the bottom loop. This is the logo associated with the 1917 World Series championship team and the 1919 Black Sox. With a couple of brief interruptions, the dark-blue logo with the large "S" lasted through 1938 (but continued in a modified block style into the 1940s). Through the 1940s, the White Sox team colors were primarily navy blue trimmed with red.
The White Sox logo in the 1950s and 1960s (actually beginning in the 1949 season) was the word "SOX" in Gothic script, diagonally arranged, with the "S" larger than the other two letters. From 1949 through 1963, the primary color was black (trimmed with red after 1951). This is the logo associated with the Go-Go Sox era.
In 1964, the primary color went back to navy blue, and the road uniforms changed from gray to pale blue. In 1971, the team's primary color changed from royal blue to red, with the color of their pinstripes and caps changing to red. The 1971–1975 uniform included red socks.
In 1976, the team's uniforms changed again. The team's primary color changed back from red to navy. The team based their uniforms on a style worn in the early days of the franchise, with white jerseys worn at home, and blue on the road. The team brought back white socks for the last time in team history. The socks featured a different stripe pattern every year. The team also had the option to wear blue or white pants with either jersey. Additionally, the team's "SOX" logo was changed to a modern-looking "SOX" in a bold font, with "CHICAGO" written across the jersey. Finally, the team's logo featured a silhouette of a batter over the words "SOX".
The new uniforms also featured collars and were designed to be worn untucked — both unprecedented. Yet by far, the most unusual wrinkle was the option to wear shorts, which the White Sox did for the first game of a doubleheader against the Kansas City Royals in 1976. The Hollywood Stars of the Pacific Coast League had previously tried the same concept, but it was also poorly received. Apart from aesthetic issues, as a practical matter, shorts are not conducive to sliding, due to the likelihood of significant abrasions.
Upon taking over the team in 1980, new owners Eddie Einhorn and Jerry Reinsdorf announced a contest where fans were invited to create new uniforms for the White Sox. The winning entries, submitted by a fan, had the word "SOX" written across the front of the jersey in the same font as the cap, inside of a large blue stripe trimmed with red. The red and blue stripes were also on the sleeves, and the road jerseys were gray to the home whites. In those jerseys, the White Sox won 99 games and the AL West championship in 1983, the best record in the majors.
After five years, those uniforms were retired and replaced with a more basic uniform that had "White Sox" written across the front in script, with "Chicago" on the front of the road jersey. The cap logo was also changed to a cursive "C", although the batter logo was retained for several years.
For a midseason 1990 game at Comiskey Park, the White Sox appeared once in a uniform based on that of the 1917 White Sox. They then switched their regular uniform style once more. In September, for the final series at the old Comiskey Park, the White Sox rolled out a new logo, a simplified version of the 1949–63 Gothic "SOX" logo. They also introduced a uniform with black pinstripes, also similar to the Go-Go Sox era uniform. The team's primary color changed back to black, this time with silver trim. The team also introduced a new sock logo—a white silhouette of a sock centered inside a white outline of a baseball diamond—which appeared as a sleeve patch on the away uniform until 2010 (switched to the "SOX" logo in 2011), and on the alternate black uniform since 1993. With minor modifications (i.e., occasionally wearing vests, black game jerseys), the White Sox have used this style ever since.
During the 2012 and 2013 seasons, the White Sox wore their throwback uniforms at home every Sunday, starting with the 1972 red-pinstriped throwback jerseys worn during the 2012 season, followed by the 1982–86 uniforms the next season. In the 2014 season, the "Winning Ugly" throwbacks were promoted to full-time alternate status, and are now worn at home on Sundays. In one game during the 2014 season, the Sox paired their throwbacks with a cap featuring the batter logo instead of the wordmark "SOX"; this is currently their batting-practice cap prior to games in the throwback uniforms. After the 2023 season, the Sunday throwback uniforms were quietly taken off the team's uniform rotation.
In 2021, to commemorate the Field of Dreams game, the White Sox wore special uniforms honoring the 1919 team. That same year, the White Sox wore "City Connect" alternate uniforms introduced by Nike, featuring an all-black design with silver pinstripes, and "Southside" wordmark in front.
==Awards and accolades==
===World Series championships===
===American League championships===
Note: American League Championship Series began in 1969
Source:
==Culture==
===Nicknames===
The White Sox were originally known as the White Stockings, a reference to the original name of the Chicago Cubs. To fit the name in headlines, local newspapers such as the Chicago Tribune abbreviated the name alternatively to Stox and Sox. Charles Comiskey would officially adopt the White Sox nickname in the club's first years, making them the first team to officially use the "Sox" name. The Chicago White Sox are most prominently nicknamed "the South Siders", based on their particular district within Chicago. Other nicknames include the synonymous "Pale Hose"; "the ChiSox", a combination of "Chicago" and "Sox", used mostly by the national media to differentiate them between the Boston Red Sox (BoSox); and "the Good Guys", a reference to the team's one-time motto "Good guys wear black", coined by broadcaster Ken Harrelson. Most fans and Chicago media refer to the team as simply "the Sox". The Spanish language media sometimes refer to the team as Medias Blancas for "White Socks."
Several individual White Sox teams have received nicknames over the years:
The 1906 team was known as the Hitless Wonders due to their .230 batting average, worst in the American League. Despite their hitting woes, the Sox would beat the crosstown Cubs for their first world title.
The 1919 White Sox are known as the Black Sox after eight players were banned from baseball for fixing the 1919 World Series.
The 1959 White Sox were referred to as the Go-Go White Sox due to their speed-based offense. The period from 1951 to 1967, in which the White Sox had 17 consecutive winning seasons, is sometimes referred to as the Go-Go era.
The 1977 team was known as the South Side Hitmen as they contended for the division title after finishing last the year before.
The 1983 White Sox became known as the Winning Ugly White Sox in response to Texas Rangers manager Doug Rader's derisive comments that the White Sox "...weren't playing well. They're winning ugly." The Sox went on to win the 1983 American League West division on September 17.
===Mascots===
From 1961 until 1991, lifelong Chicago resident Andrew Rozdilsky performed as the unofficial yet popular mascot "Andy the Clown" for the White Sox at the original Comiskey Park. Known for his elongated "Come on you White Sox" battle cry, Andy got his start after a group of friends invited him to a Sox game in 1960, where he decided to wear his clown costume and entertain fans in his section. That response was so positive that when he won free 1961 season tickets, he decided to wear his costume to all games. Comiskey Park ushers eventually offered free admission to Rozdilsky. Starting in 1981, the new ownership group led by Jerry Reinsdorf introduced a twosome, called Ribbie and Roobarb, as the official team mascots, and banned Rozdilsky from performing in the lower seating level. Ribbie and Roobarb were very unpopular, as they were seen as an attempt to get rid of the beloved Andy the Clown.
In 1988, the Sox got rid of Ribbie and Roobarb; Andy the Clown was not permitted to perform in the new Comiskey Park when it opened in 1991. In the early 1990s, the White Sox had a cartoon mascot named Waldo the White Sox Wolf that advertised the "Silver and Black Pack", the team's kids' club at the time. The team's current mascot, SouthPaw, was introduced in 2004 to attract young fans.
===Fight and theme songs===
Nancy Faust became the White Sox organist in 1970, a position she held for 40 years. She was one of the first ballpark organists to play pop music, and became known for her songs playing on the names of opposing players (such as Iron Butterfly's "In-A-Gadda-Da-Vida" for Pete Incaviglia). Her many years with the White Sox established her as one of the last great stadium organists. Since 2011, Lori Moreland has served as the White Sox organist.
Similar to the Boston Red Sox with "Sweet Caroline" (and two songs named "Tessie"), and the New York Yankees with "Theme from New York, New York", several songs have become associated with the White Sox over the years. They include:
"Let's Go Go Go White Sox" by Captain Stubby and the Buccaneers – A tribute to the "Go-Go White Sox" of the late 1950s, this song serves as the unofficial fight song of the White Sox. In 2005, scoreboard operator Jeff Szynal found a record of the song and played it for a "Turn Back the Clock" game against the Los Angeles Dodgers, whom the Sox played in the 1959 World Series. After catcher A. J. Pierzynski hit a walk-off home run, they kept the song around, as the White Sox went on to win the 2005 World Series.
"Na Na Hey Hey Kiss Him Goodbye" by Steam – Organist Nancy Faust played this song during the 1977 pennant race when a Kansas City Royals pitcher was pulled, and it became an immediate hit with White Sox fans.
"Sweet Home Chicago" – The Blues Brothers version of this Robert Johnson blues standard is played after White Sox games conclude.
"Thunderstruck" by AC/DC – One of the most prominent songs for the White Sox player introductions, the team formed a bond with AC/DC's hit song in 2005 and it has since become a staple at White Sox home games. The White Sox front office has tried replacing the song several times in an attempt to "shake things up", but White Sox fans have always showed their displeasure with new songs and have successfully gotten the front office to keep the fan-favorite song.
"Don't Stop Believin'" by Journey – During the 2005 season, the White Sox adopted the 1981 Journey song as their rally song after catcher A.J. Pierzynski suggested it be played through U.S. Cellular Field's speakers. During the 2005 World Series, the White Sox invited Journey's lead singer, Steve Perry, to Houston and allowed him to celebrate with the team on the field after the series-clinching sweep of the Houston Astros. Perry also performed the song with members of the team during the team's victory parade in Chicago.
"Don't Stop the Party" by Pitbull – After every White Sox home run at Rate Field, Pitbull's "Don't Stop the Party" played over the loudspeakers.
==Rivalries==
=== Crosstown Classic ===
The Chicago Cubs are the crosstown rivals of the White Sox, a rivalry that some made fun of prior to the White Sox's 2005 title because both of them had extremely long championship droughts. The nature of the rivalry is unique; with the exception of the 1906 World Series, in which the White Sox upset the favored Cubs, the teams never met in an official game until 1997, when interleague play was introduced. In the intervening time, the two teams sometimes met for exhibition games. The White Sox currently led the regular-season series 48–39, winning the last four consecutive seasons. The BP Crosstown Cup was introduced in 2010 and the White Sox won the first three seasons (2010–2012) until the Cubs first won the Cup in 2013 by sweeping the season series. The White Sox won the Cup the next season and retained the Cup the following two years (series was a tie - Cup remains with defending team in the event of a tie). The Cubs took back the Cup in 2017. Two series sweeps have occurred since interleague play began, both by the Cubs in 1998 and 2013.
An example of this volatile rivalry is the game played between the White Sox and the Cubs at U.S. Cellular Field on May 20, 2006. White Sox catcher A. J. Pierzynski was running home on a sacrifice fly by center fielder Brian Anderson and smashed into Cubs catcher Michael Barrett, who was blocking home plate. Pierzynski lost his helmet in the collision, and slapped the plate as he rose. Barrett stopped him, and after exchanging a few words, punched Pierzynski in the face, causing a melee to ensue. Brian Anderson and Cubs first baseman John Mabry got involved in a separate confrontation, although Mabry was later determined to be attempting to be a peacemaker. After 10 minutes of conferring following the fight, the umpires ejected Pierzynski, Barrett, Anderson, and Mabry. As Pierzynski entered his dugout, he pumped his arms, causing the sold-out crowd at U.S. Cellular Field to erupt in cheers. When play resumed, White Sox second baseman Tadahito Iguchi blasted a grand slam to put the White Sox up 5–0 on their way to a 7–0 win over their crosstown rivals. While other major league cities and metropolitan areas have two teams co-exist, all of the others feature at least one team that began playing there in 1961 or later, whereas the White Sox and Cubs have been competing for their city's fans since 1901.
=== Historical ===
A historical regional rival was the St. Louis Browns. Through the 1953 season, the two teams were located fairly close to each other (including the 1901 season when the Browns were the Milwaukee Brewers), and could have been seen as the American League equivalent of the Cardinals–Cubs rivalry, being that Chicago and St. Louis have for years been connected by the same highway (U.S. Route 66 and now Interstate 55). The rivalry has been somewhat revived at times in the past, involving the Browns' current identity, the Baltimore Orioles, most notably in 1983.
The current Milwaukee Brewers franchise were arguably the White Sox's main and biggest rival, due to the proximity of the two cities (resulting in large numbers of White Sox fans who would regularly be in attendance at the Brewers' former home, Milwaukee County Stadium), and with the teams competing in the same American League division for the 1970 and 1971 seasons and then again from 1994 to 1997. The rivalry has since cooled off, however, when the Brewers moved to the National League in 1998. However, with the start of the 2023 season, all teams will play each other at least once a year, leading to the Brewers-White Sox series to return on a yearly basis.
=== Divisional ===
====Minnesota Twins====
The rivalry between the White Sox and Minnesota Twins developed during the 2000s, as the two teams consistently battled for the AL Central Crown. The Twins won the division in 2002, 2003, 2004, 2006, and 2009, with the Sox winning in 2000, 2005, and 2008, many of those years their rival was the division runner-up. The teams met in the 2008 American League Central tie-breaker game, which was necessitated by the two clubs finishing the season with identical records. The White Sox won this game 1–0 on a Jim Thome home run. The rivalry re-emerged in the 2020s, with the Twins winning the AL Central in 2020 by a single game over the White Sox and Cleveland Indians, and the Sox and Twins have continued to compete for the division title since that point.
====Detroit Tigers====
The series between the White Sox and Detroit Tigers is one of the oldest active rivalries in the league today. Both teams joined the American League in 1901 after being charter members of the original Western League. Both have actively played one another annually for over 120 seasons. As is often the case between professional sports teams located Chicago or Detroit; there usually exists a rivalry as such with the Bulls-Pistons rivalry of the NBA. Despite playing one another for over 2,200 games; both teams have yet to meet in the postseason in their 122-year series.
===Community Outreach===
In 1990, then new White Sox owners Eddie Einhorn and Jerry Reinsdorf began Chicago White Sox Charities, a 501(c) (3) charitable organization that is the team's philanthropic arm, donating over $27 million over time to a plethora of Chicago organizations. White Sox Charities began centering on early childhood literacy programs, then expanded to focusing on encouraging high school graduation and college matriculation so the team can monitor its success. It also supports children at risk as well as promotes wellness and health.
==Home attendance==
===Comiskey Park===
===U.S. Cellular Field===
===Rate Field===
==Broadcasting==
===Radio===
The White Sox did not sell exclusive rights for radio broadcasts from radio's inception until 1944, instead having local stations share rights for games, and after WGN (720) was forced to abdicate their rights to the team in the 1943 after 16 seasons due to children's programming commitments from their network, Mutual. The White Sox first granted exclusive rights in 1944, and bounced between stations until 1952, when they started having all games broadcast on WCFL (1000). Throughout this period of instability, one thing remained constant, the White Sox play-by-play announcer, Bob Elson. Known as the "Commander", Elson was the voice of the Sox from 1929 until his departure from the club in 1970. In 1979, he was the recipient of the Ford Frick Award, and his profile is permanently on display in the National Baseball Hall of Fame.
After the 1966 season, radio rights shifted from WCFL to WMAQ (670). An NBC-owned and -operated station until 1988 when Westinghouse Broadcasting purchased it after NBC's withdrawal from radio, it was the home of the Sox until the 1996 season, outside of a team nadir in the early '70s, where it was forced to broker time on suburban La Grange's WTAQ (1300) and Evanston's WEAW-FM (105.1) to have their play-by-play air in some form (though WEAW transmitted from the John Hancock Center, FM radio was not established as a band for sports play-by-play at the time), Caray often broadcast from the stands, sitting at a table set up amid the bleachers. It became a badge of honor among Sox fans to "Buy Harry a beer..." By game's end, one would see a large stack of empty beer cups beside his microphone. This only endeared him to fans that much more. In fact, he started his tradition of leading the fans in the singing of "Take Me Out To The Ballgame" with the Sox. Caray, alongside color analyst Jimmy Piersall, was never afraid to criticize the Sox, which angered numerous Sox managers and players, notably Bill Melton and Chuck Tanner. He left to succeed Jack Brickhouse as the voice of the Cubs in 1981, where he became a national icon.
The White Sox shifted through several announcers in the 1980s, before hiring John Rooney as play-by-play announcer in 1989. In 1992, he was paired with color announcer Ed Farmer. In 14 seasons together, the duo became a highly celebrated announcing team, even being ranked by USA Today as the top broadcasting team in the American League. Starting with Rooney and Farmer's fifth season together, Sox games returned to the 1000 AM frequency for the first time in 30 years. By then, it had become the ESPN owned and operated WMVP. The last game on WMVP was game 4 of the 2005 World Series, with the White Sox clinching their first World Series title in 88 years. That also was Rooney's last game with the Sox, as he left to join the radio broadcast team of the St. Louis Cardinals.
In 2006, radio broadcasts returned to 670 AM, this time on the sports radio station WSCR owned by CBS Radio (WSCR took over the 670 frequency in August 2000 as part of a number of shifts among CBS Radio properties to meet market ownership caps). Ed Farmer became the play-by-play man after Rooney left, joined in the booth by Chris Singleton from 2006 to 2007 and then Steve Stone in 2008. In 2009, Darrin Jackson became the color announcer for White Sox radio, where he remains today. Farmer and Jackson were joined by pregame/postgame host Chris Rogney.
The Chicago White Sox Radio Network currently has 18 affiliates in three states. As of recently, White Sox games are also broadcast in Spanish with play-by-play announcer Hector Molina joined in the booth by Billy Russo. Formerly broadcasting on ESPN Deportes Radio via WNUA, games are now broadcast in Spanish on WRTO (1200).
In the 2016 season, the play-by-play rights shifted to Cumulus Media's WLS (890) under a five-year deal, when WSCR acquired the rights to Cubs games after a one-year period on WBBM. However, by all counts, the deal was a disaster for the White Sox, as WLS's declining conservative talk format, associated ratings, and management/personnel issues (including said hosts barely promoting the team and its games), and a signal that is weak in the northern suburbs and into Wisconsin, was not a good fit for the team. Cumulus also had voluminous financial issues, and by the start of 2018, looked to both file Chapter 11 bankruptcy and restructure their play-by-play deals or depart them, both with local teams and nationally through their Westwood One/NFL deal. Ed Farmer died suddenly on April 1, 2020, a long-term battle with polycystic kidney disease, but the team waited to announce his successor due to the COVID-19 pandemic and the uncertainty of the 2020 season going forward. On June 30 with the season's structure announced, Masur was confirmed as Farmer's successor for the season.
Under Nexstar's new management, WGN decided to pursue a thriftier programming direction, and made no moves to renew the deal at the end of the 2020 season. The team thus returned to WMVP (now managed by Good Karma Brands, which also owns Brewers flagship WTMJ) for a multi-year agreement to start with the 2021 season. In a surprising turn of events, WMVP and the team announced on December 4, 2020, that Len Kasper, the longtime television play-by-play voice of the Cubs, would move to the South Side and become the radio play-by-play voice of the White Sox. The agreement has flexibility which allows Kasper to do some television games on NBC Sports Chicago on days when Jason Benetti has other national commitments.
===Television===
White Sox games appeared sporadically on television throughout the first half of the 20th century, most commonly announced by Jack Brickhouse on WGN-TV (channel 9). Starting in 1968, Jack Drees took play-by-play duties as the Sox were broadcast on WFLD (channel 32). After 1972, Harry Caray (joined by Jimmy Piersall in 1977) began double duty as a TV and radio announcer for the Sox, as broadcasts were moved to channel 44, WSNS-TV, from 1972 to 1980, followed by one year on WGN-TV.
Don Drysdale became the play-by-play announcer in 1982, as the White Sox began splitting their broadcasts between WFLD and the new regional cable television network, Sportsvision. Ahead of its time, Sportsvision had a chance to gain huge profits for the Sox. However, few people would subscribe to the channel after being used to free-to-air broadcasts for many years, along with Sportsvision being stunted by the city of Chicago's wiring for cable television taking much longer than many markets because of it being an area where over-the-air subscription services were still more popular, resulting in the franchise losing around $300,000 a month. While this was going on, every Cubs game was on WGN, with Harry Caray becoming the national icon he never was with the White Sox. The relatively easy near-national access to Cubs games versus Sox games in this era, combined with the popularity of Caray and the Cubs being owned by the Tribune Company, is said by some to be the main cause of the Cubs' advantage in popularity over the Sox.
Three major changes to White Sox broadcasting occurred in 1989-1991: in 1989, with the city finally fully wired for cable service, Sportsvision was replaced by SportsChannel Chicago (itself eventually turning into Fox Sports Net Chicago), which varied over its early years as a premium sports service and basic cable channel. In 1990, over-the-air broadcasts shifted back to WGN. And in 1991, Ken Harrelson became the play-by-play announcer of the White Sox. One of the most polarizing figures in baseball, "Hawk" has been both adored and scorned for his emotive announcing style. His history of calling out umpires has earned him reprimands from the MLB commissioner's office, and he has been said to be the most biased announcer in baseball. However, Harrelson has said that he is proud of being "the biggest homer in baseball", saying that he is a White Sox fan like his viewers. The team moved from FSN Chicago to the newly launched NBC Sports Chicago in March 2005, as Jerry Reinsdorf looked to control the rights for his team rather than sell rights to another party; Reinsdorf holds a 40% interest in the network, with 20% of that interest directly owned by the White Sox corporation.
Previously, White Sox local television broadcasts were split between two channels: the majority of games were broadcast on cable by NBC Sports Chicago, and remaining games were produced by WGN Sports and were broadcast locally on WGN-TV. WGN games were also occasionally picked up by local stations in Illinois, Iowa, and Indiana. In the past, WGN games were broadcast nationally on the WGN America superstation, but those broadcasts ended after the 2014 season as WGN America began its transition to a standard cable network. WGN Sports-produced White Sox games not carried by WGN-TV were carried by WCIU-TV (channel 26) until the 2015 season, when they moved to MyNetworkTV station WPWR (channel 50). That arrangement ended on September 1, 2016, when WGN became an independent station.
Prior to 2016, the announcers were the same no matter where the games were broadcast: Harrelson provided play-by-play, and Steve Stone provided color analysis since 2009. Games that are broadcast on NBC Sports Chicago feature pregame and postgame shows, hosted by Chuck Garfein with analysis from Bill Melton and occasionally Frank Thomas. In 2016, the team announced an official split of the play-by-play duties, with Harrelson calling road games and the Crosstown Series and Jason Benetti calling home games. In 2017, the team announced that the 2018 season will be Harrelson's final in the booth. He will call 20 games over the course of the season, after which Benetti will take over full-time play-by-play duties.
On January 2, 2019, the White Sox (along with the Chicago Bulls and Chicago Blackhawks) agreed to an exclusive multiyear deal with NBC Sports Chicago, ending the team's broadcasts on WGN-TV following the 2019 season.
Prior to the 2024 season, the White Sox named John Schriffen as its new lead television play-by-play announcer, after Benetti departed to join the Detroit Tigers broadcast team.
==Minor league affiliates==
The Chicago White Sox farm system consists of six minor league affiliates.
==Silver Chalice subsidiary==
Silver Chalice is a digital and media investment subsidiary of the White Sox with Brooks Boyer as CEO.
Silver Chalice was co-founded by Jerry Reinsdorf, White Sox executive Brooks Boyer, Jason Coyle and John Burris in 2009. The company first invested in 120 Sports, a digital sports channel, that launched in June 2014.
In May 2023, Sinclair sold its controlling interest in Stadium to Silver Chalice.
|
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] |
5,946 |
Casuistry
|
Casuistry ( ) is a process of reasoning that seeks to resolve moral problems by extracting or extending abstract rules from a particular case, and reapplying those rules to new instances. This method occurs in applied ethics and jurisprudence. The term is also used pejoratively to criticise the use of clever but unsound reasoning, especially in relation to ethical questions (as in sophistry). It has been defined as follows:
Study of cases of conscience and a method of solving conflicts of obligations by applying general principles of ethics, religion, and moral theology to particular and concrete cases of human conduct. This frequently demands an extensive knowledge of natural law and equity, civil law, ecclesiastical precepts, and an exceptional skill in interpreting these various norms of conduct....
It remains a common method in applied ethics.
==Etymology==
According to the Online Etymological Dictionary, the term and its agent noun "casuist", appearing from about 1600, derive from the Latin noun , meaning "case", especially as referring to a "case of conscience". The same source says, "Even in the earliest printed uses the sense was pejorative".
==History==
Casuistry dates from at least Aristotle (384–322 BC), yet the peak of casuistry was from 1550 to 1650, when the Society of Jesus (commonly known as the Jesuits) used case-based reasoning, particularly in administering the Sacrament of Penance (or "confession"). The term became pejorative following Blaise Pascal's attack on the misuse of the method in his Provincial Letters (1656–57). The French mathematician, religious philosopher and Jansenist sympathiser attacked priests who used casuistic reasoning in confession to pacify wealthy church donors. Pascal charged that "remorseful" aristocrats could confess a sin one day, re-commit it the next, then generously donate to the church and return to re-confess their sin, confident that they were being assigned a penance in name only. These criticisms darkened casuistry's reputation in the following centuries. For example, the Oxford English Dictionary quotes a 1738 essay by Henry St. John, 1st Viscount Bolingbroke to the effect that casuistry "destroys, by distinctions and exceptions, all morality, and effaces the essential difference between right and wrong, good and evil".
The 20th century saw a revival of interest in casuistry. In their book The Abuse of Casuistry: A History of Moral Reasoning (1988), Albert Jonsen and Stephen Toulmin argue that it is not casuistry but its abuse that has been a problem; that, properly used, casuistry is powerful reasoning. Jonsen and Toulmin offer casuistry as a method for compromising the contradictory principles of moral absolutism and moral relativism. In addition, the ethical philosophies of utilitarianism (especially preference utilitarianism) and pragmatism have been identified as employing casuistic reasoning.
===Early modernity===
The casuistic method was popular among Catholic thinkers in the early modern period. Casuistic authors include Antonio Escobar y Mendoza, whose Summula casuum conscientiae (1627) enjoyed great success, Thomas Sanchez, Vincenzo Filliucci (Jesuit and penitentiary at St Peter's), Antonino Diana, Paul Laymann (Theologia Moralis, 1625), John Azor (Institutiones Morales, 1600), Etienne Bauny, Louis Cellot, Valerius Reginaldus, and Hermann Busembaum (d. 1668).
The progress of casuistry was interrupted toward the middle of the 17th century by the controversy which arose concerning the doctrine of probabilism, which effectively stated that one could choose to follow a "probable opinion"that is, an opinion supported by a theologian or anothereven if it contradicted a more probable opinion or a quotation from one of the Fathers of the Church.
Certain kinds of casuistry were criticised by early Protestant theologians, because it was used to justify many of the abuses that they sought to reform. It was famously attacked by the Catholic and Jansenist philosopher Blaise Pascal during the formulary controversy against the Jesuits, in his Provincial Letters, as the use of rhetorics to justify moral laxity, which became identified by the public with Jesuitism; hence the everyday use of the term to mean complex and sophistic reasoning to justify moral laxity. By the mid-18th century, "casuistry" had become a synonym for attractive-sounding, but ultimately false, moral reasoning.
In 1679 Pope Innocent XI publicly condemned sixty-five of the more radical propositions (stricti mentalis), taken chiefly from the writings of Escobar, Suarez and other casuists as propositiones laxorum moralistarum and forbade anyone to teach them under penalty of excommunication. Despite this condemnation by a pope, both Catholicism and Protestantism permit the use of ambiguous statements in specific circumstances.
===Later modernity===
G. E. Moore dealt with casuistry in chapter 1.4 of his Principia Ethica, in which he claimed that "the defects of casuistry are not defects of principle; no objection can be taken to its aim and object. It has failed only because it is far too difficult a subject to be treated adequately in our present state of knowledge". Furthermore, he asserted that "casuistry is the goal of ethical investigation. It cannot be safely attempted at the beginning of our studies, but only at the end".
Since the 1960s, applied ethics has revived the ideas of casuistry in applying moral reasoning to particular cases in law, bioethics, and business ethics. Its facility for dealing with situations where rules or values conflict with each other has made it a useful approach in professional ethics, and casuistry's reputation has improved somewhat as a result.
Pope Francis, a Jesuit, has criticized casuistry as "the practice of setting general laws on the basis of exceptional cases" in instances where a more holistic approach would be preferred.
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5,948 |
Chinese input method
|
Several input methods allow the use of Chinese characters with computers. Most allow selection of characters based either on their pronunciation or their graphical shape. Phonetic input methods are easier to learn but are less efficient, while graphical methods allow faster input, but have a steep learning curve.
Other methods allow users to write characters directly via touchscreens, such as those found on mobile phones and tablet computers.
== History ==
Chinese input methods predate the computer. One of the early attempts was an electro-mechanical Chinese typewriter Mingkwai () which was invented by Lin Yutang, a prominent Chinese writer, in the 1940s. It assigned thirty base shapes or strokes to different keys and adopted a new way of categorizing Chinese characters. But the typewriter was not produced commercially and Lin soon found himself deeply in debt.
Before the 1980s, Chinese publishers hired teams of workers and selected a few thousand type pieces from an enormous Chinese character set. Chinese government agencies entered characters using a long, complicated list of Chinese telegraph codes, which assigned different numbers to each character. During the early computer era, Chinese characters were categorized by their radicals or Pinyin romanization, but results were less than satisfactory.
In the 1970s to 1980s, large keyboards with thousands of keys were used to input Chinese. Each key was mapped to several Chinese characters. To type a character, one pressed the character key and then a selection key. There were also experimental "radical keyboards" with dozens to several hundreds keys. Chinese characters were decomposed into "radicals", each of which was represented by a key.
Chu Bong-Foo invented a common input method in 1976 with his Cangjie input method, which assigns different "roots" to each key on a standard computer keyboard. With this method, for example, the character is assigned to the A key, and 月 is assigned to B. Typing them together will result in the character ("bright").
Despite its steeper learning curve, this method remains popular in Chinese communities that use traditional Chinese characters, such as Hong Kong and Taiwan; the method allows very precise input, thus allowing users to type more efficiently and quickly, provided they are familiar with the fairly complicated rules of the method. It was the first method that allowed users to enter more than a hundred Chinese characters per minute. Its popularity is also helped by its omnipresence on traditional Chinese computer systems, since Chu has given up its patent in 1982, stating that it should be part of the cultural asset. Developers of Chinese systems can adopt it freely, and users do not have the hassle of it being absent on devices with Chinese support. Cangjie input programs supporting a large CJK character set have been developed.
All methods have their strengths and weaknesses. The pinyin method can be learned rapidly but its maximum input rate is limited. The Wubi method takes longer to learn, but expert typists can enter text much more rapidly with it than with phonetic methods. However, Wubi is proprietary, and a version of it has become freely available only after its inventor lost a patent lawsuit in 1997.
Due to these complexities, there is no "standard" method.
By 1989, bopomofo and pinyin were available for the IBM PC. In mainland China, pinyin methods such as Sogou Pinyin and Google Pinyin are the most popular. In Taiwan, use of Cangjie, Dayi, Boshiamy, and bopomofo predominate; and in Hong Kong and Macau, the Cangjie is most often taught in schools, while a few schools teach CKC Chinese Input System.
Other methods include handwriting recognition, OCR and speech recognition. The computer itself must first be "trained" before the first or second of these methods are used; that is, the new user enters the system in a special "learning mode" so that the system can learn to identify their handwriting or speech patterns. The latter two methods are used less frequently than keyboard-based input methods and suffer from relatively high error rates, especially when used without proper "training", though higher error rates are an acceptable trade-off to many users.
== Categories ==
=== Phonetic-based ===
The user enters pronunciations that are converted into relevant Chinese characters. The user must select the desired character from homophones, which are common in Chinese. Modern systems, such as Sogou Pinyin and Google Pinyin, predict the desired characters based on context and user preferences. For example, if one enters the sounds jicheng, the software will type (to inherit), but if jichengche is entered, (taxi) will appear.
Various Chinese dialects complicate the system. Phonetic methods are mainly based on standard pinyin, Zhuyin/Bopomofo, and Jyutping in China, Taiwan, and Hong Kong, respectively. Input methods based on other varieties of Chinese, like Hakka or Minnan, also exist.
While the phonetic system is easy to learn, choosing appropriate Chinese characters slows typing speed. Most users report a typing speed of fifty characters per minute, though some reach over one hundred per minute. With some phonetic IMEs (Input Method Editors), in addition to predictive input based on previous conversions, it is possible for users to create custom dictionary entries for frequently used characters and phrases, potentially lowering the number of characters required to evoke it.
==== Shuangpin ====
Shuangpin (; ), literally dual spell, is a stenographical phonetic input method based on hanyu pinyin that reduces the number of keystrokes for one Chinese character to two by distributing every vowel and consonant composed of more than one letter to a specific key. In most Shuangpin layout schemes such as Xiaohe, Microsoft 2003 and Ziranma, the most frequently used vowels are placed on the middle layer, reducing the risk of repetitive strain injury.
Shuangpin is supported by a large number of pinyin input software including QQ, Microsoft Bing Pinyin, Sogou Pinyin and Google Pinyin.
=== Shape-based ===
Cangjie input method
Simplified Cangjie
Dayi method
Array input method ()
Four-corner method
Stroke count method
Wubi method
Zhengma method
Biaoxingma method
ZYQ method ()
=== Others ===
Chinese telegraph code ()
=== Examples of keyboard layouts ===
Image:Keyboard layout Zhuyin.svg|A typical keyboard layout for zhuyin on computers, which can be used as an input method
Image:Wubi keyboard.png|A keyboard using the Wubi method
Image:Keyboard layout cangjie.png|A typical keyboard layout for the Cangjie method, which is based on the U.S. keyboard layout. Note the non-standard use of Z as the collision key.
Image:Keyboard layout Dayi.svg|A typical keyboard layout for the Dayi method
Image:Keyboard layout Chinese Traditional.png|Chinese (traditional) keyboard layout, a US keyboard with Zhuyin, Cangjie and Dayi key labels, which can all be used to input Chinese characters into a computer
== Software ==
Microsoft IME
Sogou Pinyin
Google Pinyin
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5,950 |
Columbus, Ohio
|
{{Infobox settlement
| name = Columbus
| settlement_type = State capital city
| image_skyline =
| image_flag = Flag of Columbus, Ohio.svg
| flag_size = 100px
| flag_link = Flag of Columbus, Ohio
| image_seal = Columbus seal.pngclass=skin-invert
| image_blank_emblem = Columbus wordmark.svg
| blank_emblem_size = 150px
| blank_emblem_type = Wordmark
| nicknames =
| image_map =
| map_caption = Interactive map of Columbus
| pushpin_map = Ohio#USA
| pushpin_relief = yes
| coordinates =
| subdivision_type = Country
| subdivision_name = United States
| subdivision_type1 = State
| subdivision_type2 = Counties
| subdivision_name1 = Ohio
| subdivision_name2 =
| established_title = Settled
| established_date =
| named_for = Christopher Columbus
| established_title2 =
| established_date2 =
| government_type = Mayor–council
| governing_body = Columbus City Council
| leader_title = Mayor
| leader_name = Andrew Ginther
| leader_party = D
| leader_title1 = Council members
| leader_name1 =
| unit_pref = Imperial
| area_footnotes =
| area_total_sq_mi = 226.26
| area_total_km2 = 586.00
| area_land_sq_mi = 220.40
| area_land_km2 = 570.82
| area_water_sq_mi = 5.86
| area_water_km2 = 15.18
| elevation_ft = 791
| elevation_footnotes =
| population_metro = 2138926 (US: 32nd)
| population_est = 913175
| pop_est_as_of = 2023
| pop_est_footnotes =
| population_demonym = Columbusite
| demographics_type2 = GDP
| demographics2_footnotes =
| demographics2_title1 = Metro
| demographics2_info1 = $182.088 billion (2023)
| postal_code_type = ZIP Codes
| postal_code =
| area_code_type = Area codes
| area_code = 614 and 380
| website =
| footnotes =
| timezone = EST
| utc_offset = −5
| timezone_DST = EDT
| utc_offset_DST = −4
| blank_name = FIPS code
| blank_info = 39-18000
| blank1_name = GNIS feature ID
| blank1_info = 1086101
| established_title1 = Incorporated
| established_date1 = it is the 14th-most populous city in the U.S., the second-most populous city in the Midwest (after Chicago), and the third-most populous U.S. state capital (after Phoenix, Arizona, and Austin, Texas). Columbus is the county seat of Franklin County; it also extends into Delaware and Fairfield counties. It is the core city of the Columbus metropolitan area, which encompasses ten counties in central Ohio. It had a population of 2.139 million in 2020, making it the largest metropolitan area entirely in Ohio and 32nd-largest metro area in the U.S.
Columbus originated as numerous Native American settlements on the banks of the Scioto River. Franklinton, now a city neighborhood, was the first European settlement, laid out in 1797. The city was founded in 1812 at the confluence of the Scioto and Olentangy rivers, and laid out to become the state capital. The city was named for Italian explorer Christopher Columbus. Although no reliable history exists as to why Columbus, who had no connection to the city or state of Ohio before the city's founding, was chosen as the name for the city, the book Columbus: The Story of a City indicates a state lawmaker and local resident admired the explorer enough to persuade other lawmakers to name the settlement Columbus. Efforts to remove symbols related to the explorer in the city date to the 1990s. Amid the George Floyd protests in 2020, several petitions pushed for the city to be renamed.
Nicknames for the city have included "the Discovery City", "Arch City", "Cap City", "Cowtown", "The Biggest Small Town in America" and "Cbus."
==History==
===Ancient and early history===
Between 1000 B.C. and 1700 A.D., the Columbus metropolitan area was a center to indigenous cultures known as the Mound Builders, including the Adena, Hopewell and Fort Ancient peoples. Remaining physical evidence of the cultures are their burial mounds and what they contained. Most of Central Ohio's remaining mounds are located outside of Columbus city boundaries, though the Shrum Mound is maintained, now as part of a public park and historic site. The city's Mound Street derives its name from a mound that existed by the intersection of Mound and High Streets. The mound's clay was used in bricks for most of the city's initial brick buildings; many were subsequently used in the Ohio Statehouse. The city's Ohio History Center maintains a collection of artifacts from these cultures.
===18th century===
The area including present-day Columbus once comprised the Ohio Country, under the nominal control of the French colonial empire through the Viceroyalty of New France from 1663 until 1763.
In the 18th century, European traders flocked to the area, attracted by the fur trade. The area was often caught between warring factions, including American Indian and European interests. In the 1740s, Pennsylvania traders overran the territory until the French forcibly evicted them. Fighting for control of the territory in the French and Indian War (1754–1763) became part of the international Seven Years' War (1756–1763). During this period, the region routinely suffered turmoil, massacres and battles. The 1763 Treaty of Paris ceded the Ohio Country to the British Empire.
Up until the American Revolution, Central Ohio had continuously been the home of numerous indigenous villages. A Mingo village was located at the forks of the Scioto and Olentangy rivers, with Shawnee villages to the south and Wyandot and Delaware villages to the north. Colonial militiamen burned down the Mingo village in 1774 during a raid.
====Virginia Military District====
After the American Revolution, the Virginia Military District became part of the Ohio Country as a territory of Virginia. Colonists from the East Coast moved in, but rather than finding an empty frontier, they encountered people of the Miami, Delaware, Wyandot, Shawnee and Mingo nations, as well as European traders. The tribes resisted expansion by the fledgling United States, leading to years of bitter conflict. The decisive Battle of Fallen Timbers resulted in the Treaty of Greenville in 1795, which finally opened the way for new settlements. By 1797, a young surveyor from Virginia named Lucas Sullivant had founded a permanent settlement on the west bank of the forks of the Scioto and Olentangy rivers. An admirer of Benjamin Franklin, Sullivant chose to name his frontier village "Franklinton." The location was desirable for its proximity to the navigable rivers – but Sullivant was initially foiled when, in 1798, a large flood wiped out the new settlement. He persevered, and the village was rebuilt, though somewhat more inland.
After the Revolution, land comprising parts of Franklin and adjacent counties was set aside by the United States Congress for settlement by Canadians and Nova Scotians who were sympathetic to the colonial cause and had their land and possessions seized by the British government. The Refugee Tract, consisting of , was long and wide, and was claimed by 67 eligible men. The Ohio Statehouse sits on land once contained in the Refugee Tract.
===19th century===
After Ohio achieved statehood in 1803, political infighting among prominent Ohio leaders led to the state capital moving from Chillicothe to Zanesville and back again. Desiring to settle on a location, the state legislature considered Franklinton, Dublin, Worthington and Delaware before compromising on a plan to build a new city in the state's center, near major transportation routes, primarily rivers. As well, Franklinton landowners had donated two plots in an effort to convince the state to move its capital there. The two spaces were set to become Capitol Square, including for the Ohio Statehouse and the Ohio Penitentiary. Named in honor of Christopher Columbus, the city was founded on February 14, 1812, on the "High Banks opposite Franklinton at the Forks of the Scioto most known as Wolf's Ridge." At the time, this area was a dense forestland, used only as a hunting ground.
The city was incorporated as a borough on February 10, 1816. Between 1816 and 1817, Jarvis W. Pike served as the first appointed mayor. Although the recent War of 1812 had brought prosperity to the area, the subsequent recession and conflicting claims to the land threatened the new town's success. Early conditions were abysmal, with frequent bouts of fevers, attributed to malaria from the flooding rivers, and an outbreak of cholera in 1833. It led Columbus to create the Board of Health, now part of the Columbus Public Health department. The outbreak, which remained in the city from July to September 1833, killed 100 people.
Columbus was without direct river or trail connections to other Ohio cities, leading to slow initial growth. The National Road reached Columbus from Baltimore in 1831, which complemented the city's new link to the Ohio and Erie Canal, both of which facilitated a population boom.
With a population of 3,500, Columbus was officially chartered as a city on March 3, 1834. On that day, the legislature carried out a special act, which granted legislative authority to the city council and judicial authority to the mayor. Elections were held in April of that year, with voters choosing John Brooks as the first popularly elected mayor. Columbus annexed the then-separate city of Franklinton in 1837.
In 1850, the Columbus and Xenia Railroad became the first railroad into the city, followed by the Cleveland, Columbus and Cincinnati Railroad in 1851. The two railroads built a joint Union Station on the east side of High Street just north of Naghten (then called North Public Lane). Rail traffic into Columbus increased: by 1875, eight railroads served Columbus, and the rail companies built a new, more elaborate station. Another cholera outbreak hit Columbus in 1849, prompting the opening of the city's Green Lawn Cemetery. On January 7, 1857, the Ohio Statehouse finally opened after 18 years of construction.
Before the abolition of slavery in the Southern United States in 1863, the Underground Railroad was active in Columbus and was led, in part, by James Preston Poindexter. Poindexter arrived in Columbus in the 1830s and became a Baptist preacher and leader in the city's African-American community until the turn of the century.
During the Civil War, Columbus was a major base for the volunteer Union Army. It housed 26,000 troops and held up to 9,000 Confederate prisoners of war at Camp Chase, at what is now the Hilltop neighborhood of west Columbus. Over 2,000 Confederate soldiers remain buried at the site, making it one of the North's largest Confederate cemeteries.
By virtue of the Morrill Act of 1862, the Ohio Agricultural and Mechanical College – which eventually became the Ohio State University – was founded in 1870 on the former estate of William and Hannah Neil.
By the end of the 19th century, Columbus was home to several major manufacturing businesses. The Jeffrey Manufacturing Company was a major supplier of coal mining equipment. The city became known as the "Buggy Capital of the World," thanks to the two dozen buggy factories – notably the Columbus Buggy Company, founded in 1875 by C.D. Firestone. The Columbus Consolidated Brewing Company also rose to prominence during this time and might have achieved even greater success were it not for the Anti-Saloon League in neighboring Westerville.
In the steel industry, a forward-thinking man named Samuel P. Bush presided over the Buckeye Steel Castings Company. Columbus was also a popular location for labor organizations. In 1886, Samuel Gompers founded the American Federation of Labor in Druid's Hall on South Fourth Street, and in 1890, the United Mine Workers of America was founded at the old City Hall.
===20th century===
Columbus earned one of its nicknames, "The Arch City," because of the dozens of wooden arches that spanned High Street at the turn of the 20th century. The arches illuminated the thoroughfare and eventually became the means by which electric power was provided to the new streetcars. The city tore down the arches and replaced them with cluster lights in 1914 but reconstructed them from metal in the Short North neighborhood in 2002 for their unique historical interest.
On March 25, 1913, the Great Flood of 1913 devastated the neighborhood of Franklinton, leaving over 90 people dead and thousands of West Side residents homeless. To prevent flooding, the Army Corps of Engineers recommended widening the Scioto River through downtown, constructing new bridges and building a retaining wall along its banks. With the strength of the post-World War I economy, a construction boom occurred in the 1920s, resulting in a new civic center, the Ohio Theatre, the American Insurance Union Citadel and to the north, a massive new Ohio Stadium. Although the American Professional Football Association was founded in Canton in 1920, its head offices moved to Columbus in 1921 to the New Hayden Building and remained in the city until 1941.
In 1922, the association's name was changed to the National Football League. Nearly a decade later, in 1931, at a convention in the city, the Jehovah's Witnesses took that name by which they are known today.
The effects of the Great Depression were less severe in Columbus, as the city's diversified economy helped it fare better than its Rust Belt neighbors. World War II brought many new jobs and another population surge. This time, most new arrivals were migrants from the "extraordinarily depressed rural areas" of Appalachia, who would soon account for more than a third of Columbus's growing population. In 1948, the Town and Country Shopping Center opened in suburban Whitehall, and it is now regarded as one of the first modern shopping centers in the United States.
The construction of the Interstate Highway System signaled the arrival of rapid suburb development in central Ohio. To protect the city's tax base from this suburbanization, Columbus adopted a policy of linking sewer and water hookups to annexation to the city. By the early 1990s, Columbus had grown to become Ohio's largest city in land area and in population.
Efforts to revitalize downtown Columbus have had some success in recent decades, though like most major American cities, some architectural heritage was lost in the process. In the 1970s, landmarks such as Union Station and the Neil House hotel were razed to construct high-rise offices and big retail space. The PNC Bank building was constructed in 1977, as well as the Nationwide Plaza buildings and other towers that sprouted during this period. The construction of the Greater Columbus Convention Center has brought major conventions and trade shows to the city.
===21st century===
The Scioto Mile began development along the riverfront, an area that already had the Miranova Corporate Center and The Condominiums at North Bank Park.
The 2010 United States foreclosure crisis forced the city to purchase numerous foreclosed, vacant properties to renovate or demolish them – at a cost of tens of millions of dollars. In February 2011, Columbus had 6,117 vacant properties, according to city officials.
Since 2010, Columbus has been growing in population and economy; from 2010 to 2017, the city added 164,000 jobs, which ranked second in the United States. In February and March 2020, Columbus reported its first official cases of COVID-19 and declared a state of emergency, with all nonessential businesses closed statewide. There were 69,244 cases of the disease across the city, . Later in 2020, protests over the murder of George Floyd took place in the city from May 28 into August. Columbus and its metro area have experienced growth in the high-tech manufacturing sector, with Intel announcing plans to construct a $20 billion factory and Honda expanding its presence along with LG Energy Solutions with a $4.4 billion battery manufactory facility in Fayette County.
The COVID-19 pandemic muted activity in Columbus, especially in its downtown core, from 2020 to 2022. By late 2022, foot traffic in Downtown Columbus began to exceed pre-pandemic rates; one of the quickest downtown areas to recover in the United States.
On June 23, 2023, ten people were injured in a mass shooting in the city's Short North district.
==== Ransomware attack ====
In July 2024, Columbus was subject to a ransomware attack, for which the hacker group Rhysidia took credit. In August 2024, Columbus Mayor Andrew Ginther claimed that the files obtained by Rhysidia were "unusable" to the thieves due to being either encrypted or corrupted. Ginther's assertion was subsequently shown to be false by security researcher David Leroy Ross (who goes by the alias Connor Goodwolf), who revealed that the files were intact and contained data including names from domestic violence cases and Social Security numbers of crime victims. Columbus then sued Ross for alleged criminal acts, negligence, and civil conversion, as well as taking out a restraining order against Ross, both of which actions were later defended by City Attorney Zach Klein. In response, a number of prominent cybersecurity researchers called on the city to drop the lawsuit.
==== Neo-Nazi march ====
On Saturday, November 19th, 2024, about a dozen masked men dressed in black carried red swastika flags in Columbus chanting racial slurs and using pepper spray. The group identified themselves as "Hate Club". Oren Segal, ADL vice-president, said that this might related to the hate group Blood Tribe. "Blood Tribe views itself as the main white supremacist group in Ohio, so ... (the) 'Hate Club' march appears to have been an intentional effort to antagonize them."
==Geography==
The confluence of the Scioto and Olentangy rivers is just northwest of Downtown Columbus. Several smaller tributaries course through the Columbus metropolitan area, including Alum Creek, Big Walnut Creek and Darby Creek. Columbus is considered to have relatively flat topography thanks to a large glacier that covered most of Ohio during the Wisconsin Ice Age. However, there are sizable differences in elevation through the area, with the high point of Franklin County being above sea level near New Albany, and the low point being where the Scioto River leaves the county near Lockbourne.
Several ravines near the rivers and creeks also add variety to the landscape. Tributaries to Alum Creek and the Olentangy River cut through shale, while tributaries to the Scioto River cut through limestone. The numerous rivers and streams beside low-lying areas in Central Ohio contribute to a history of flooding in the region; the most significant was the Great Flood of 1913 in Columbus, Ohio.
The city has a total area of , of which is land and is water. Columbus currently has the largest land area of any Ohio city; this is due to Jim Rhodes's tactic to annex suburbs while serving as mayor. As surrounding communities grew or were constructed, they came to require access to waterlines, which was under the sole control of the municipal water system. Rhodes told these communities that if they wanted water, they would have to submit to assimilation into Columbus.
===Neighborhoods===
Columbus has a wide diversity of neighborhoods with different characters, and is thus sometimes known as a "city of neighborhoods." Some of the most prominent neighborhoods include the Arena District, the Brewery District, Clintonville, Franklinton, German Village, The Short North and Victorian Village. The lowest recorded temperature was , occurring on January 19, 1994. Floods, blizzards and ice storms can also occur from time to time.
==Demographics==
=== 2010 census ===
In the 2010 United States census, there were 787,033 people, 331,602 households and 176,037 families residing in the city. The population density was . There were 370,965 housing units at an average density of .
The racial makeup of the city included 815,985 races tallied, as some residents recognized multiple races. The racial makeup was 61.9% White, 29.1% Black or African American, 1% Native American or Alaska Native, 4.6% Asian, 0.2% Native Hawaiian or Pacific Islander, and 3.2% from other races. Hispanic or Latino of any race were 5.9% of the population.
===Population makeup===
Columbus historically had a significant population of white people. In 1900, whites made up 93.4% of the population. Although European immigration has declined, the Columbus metropolitan area has recently experienced increases in African, Asian and Latin American immigration, including groups from Mexico, India, Nepal, Bhutan, Somalia and China. While the Asian population is diverse, the city's Hispanic community is mainly made up of Mexican Americans, although there is a notable Puerto Rican population. Many other countries of origin are represented in lesser numbers, largely due to the international draw of Ohio State University. 2008 estimates indicate that roughly 116,000 of the city's residents are foreign-born, accounting for 82% of the new residents between 2000 and 2006 at a rate of 105 per week. The city had the second-largest Somali and Somali American population in the country, as of 2004, as well as the largest expatriate Bhutanese-Nepali population in the world, as of 2018.
Due to its demographics, which include a mix of races and a wide range of incomes, as well as urban, suburban and nearby rural areas, Columbus is considered a "typical" American city, leading retail and restaurant chains to use it as a test market for new products. For similar reasons, the city was chosen as the launch city for the QUBE cable television service.
Columbus has maintained a steady population growth since its establishment. Its slowest growth, from 1850 to 1860, is primarily attributed to the city's cholera epidemic in the 1850s.
According to the 2017 Japanese Direct Investment Survey by the Consulate-General of Japan, Detroit, 838 Japanese nationals lived in Columbus, making it the municipality with the state's second-largest Japanese national population, after Dublin.
Columbus is home to a proportional LGBT community, with an estimated 34,952 gay, lesbian or bisexual residents. The 2018 American Community Survey (ACS) reported an estimated 366,034 households, 32,276 of which were held by unmarried partners. 1,395 of these were female householder and female-partner households, and 1,456 were male householder and male-partner households. Columbus has been rated as one of the best cities in the country for gays and lesbians to live, and also as the most underrated gay city in the country. In July 2012, three years prior to legal same-sex marriage in the United States, the Columbus City Council unanimously passed a domestic partnership registry.
====Italian-American community and symbols====
Columbus has numerous Italian Americans, with groups including the Columbus Italian Club, Columbus Piave Club and the Abruzzi Club. Italian Village, a neighborhood near Downtown Columbus, has had a prominent Italian American community since the 1890s.
The community has helped promote the influence Christopher Columbus had in drawing European attention to the Americas. The Italian explorer, erroneously credited with the lands' discovery, has been posthumously criticized by historians for initiating colonization and for abuse, enslavement and subjugation of natives. The city's Discovery District and Discovery Bridge are named in reference to Columbus's "discovery" of the Americas; the bridge includes artistic bronze medallions featuring symbols of the explorer. Genoa Park, downtown, is named after Genoa, the birthplace of Christopher Columbus and one of Columbus's sister cities.
The Christopher Columbus Quincentennial Jubilee, celebrating the 500th anniversary of Columbus's first voyage, was held in the city in 1992. Its organizers spent $95 million on it, creating the horticultural exhibition AmeriFlora '92. The organizers also planned to create a replica Native American village, among other attractions. Local and national native leaders protested the event with a day of mourning, followed by protests and fasts at City Hall. The protests prevented the native village from being exhibited, and annual fasts continued until 1997. A protest also took place during the dedication of the Santa Maria replica, an event held in late 1991 on the day before Columbus Day and in time for the jubilee.
The city has three outdoor statues of the explorer; the statue at City Hall was acquired, delivered and dedicated with the assistance of the Italian American community. Protests in 2017 aimed for this statue to be removed, followed by the city in 2018 ceasing to recognize Columbus Day as a city holiday. During the 2020 George Floyd protests, petitions were created to remove all three statues and rename the city of Columbus.
===Religion===
According to the 2019 American Values Atlas, 26% of Columbus metropolitan area residents are unaffiliated with a religious tradition. 17% of area residents identify as White evangelical Protestants, 14% as White mainline Protestants, 11% as Black Protestants, 11% as White Catholics, 5% as Hispanic Catholics, 3% as other nonwhite Catholics, 2% as other nonwhite Protestants and 2% as Mormons. Hindus, Buddhists, Jews and Latino Protestants each made up 1% of the population, while Jehovah's Witnesses, Orthodox Christians, Muslims, Unitarians, and members of New Age or other religions each made up under 0.5% of the population.
Places of worship include Baptist, Evangelical, Greek Orthodox, Latter-day Saints, Lutheran, Presbyterian, Quaker, Roman Catholic, and Unitarian Universalist churches. Columbus also hosts several Islamic mosques, Jewish synagogues, Buddhist centers, Hindu temples and a branch of the International Society for Krishna Consciousness. Religious teaching institutions include the Pontifical College Josephinum and several private schools led by Christian organizations.
==Economy==
Columbus has a generally strong and diverse economy based on education, insurance, banking, fashion, defense, aviation, food, logistics, steel, energy, medical research, health care, hospitality, retail and technology. In 2010, it was one of the 10 best big cities in the country, according to Relocate America, a real estate research firm.
According to the Federal Reserve Bank of St. Louis, the GDP of Columbus in 2019 was $134 billion (~$ in ).
During the Great Recession between 2007 and 2009, Columbus's economy was not impacted as much as the rest of the country, due to decades of diversification work by long-time corporate residents, business leaders and political leaders. The administration of former mayor Michael B. Coleman continued this work, although the city faced financial turmoil and had to increase taxes, allegedly due in part to fiscal mismanagement. Because Columbus is the state capital, there is a large government presence in the city. Including city, county, state and federal employers, government jobs provide the largest single source of employment within Columbus.
In 2019, the city had six corporations named to the U.S. Fortune 500 list: Alliance Data, Nationwide Mutual Insurance Company, American Electric Power, L Brands, Huntington Bancshares and Cardinal Health in suburban Dublin. Other major employers include schools (e.g., Ohio State University) and hospitals (among others, Wexner Medical Center and Nationwide Children's Hospital, which are among the teaching hospitals of the Ohio State University College of Medicine), high-tech research and development such as the Battelle Memorial Institute, information/library companies such as OCLC and Chemical Abstracts Service, steel processing and pressure cylinder manufacturer Worthington Industries, financial institutions such as JPMorgan Chase and Huntington Bancshares, as well as Owens Corning. Fast-food chains Wendy's and White Castle are also headquartered in the Columbus area. Major foreign corporations operating or with divisions in the city include Germany-based Siemens and Roxane Laboratories, Finland-based Vaisala, Tomasco Mulciber Inc., A Y Manufacturing, as well as Switzerland-based ABB and Mettler Toledo. The city also has a significant fashion and retail presence, home to companies such as Big Lots, L Brands, Abercrombie & Fitch, DSW and Express.
===Food and beverage industry===
North Market, a public market and food hall, is located downtown near the Short North. It is the only remaining public market of Columbus's original four marketplaces.
Numerous restaurant chains are based in the Columbus area, including Charleys Philly Steaks, Bibibop Asian Grill, Steak Escape, White Castle, Cameron Mitchell Restaurants, Bob Evans Restaurants, Max & Erma's, Damon's Grill, Donatos Pizza and Wendy's. Wendy's, the world's third-largest hamburger fast-food chain, operated its first store downtown as both a museum and a restaurant until March 2007, when the establishment was closed due to low revenue. The company is presently headquartered outside the city in nearby Dublin. Budweiser has a major brewery located on the north side, just south of I-270 and Worthington. Columbus is also home to many local micro breweries and pubs. Asian frozen food manufacturer Kahiki Foods was located on the east side of Columbus, created during the operation of the Kahiki Supper Club restaurant in Columbus. The food company now operates in the suburb of Gahanna and has been owned by the South Korean-based company CJ CheilJedang since 2018. Wasserstrom Company, a major supplier of equipment and supplies for restaurants, is located on the north side.
==Arts and culture==
===Landmarks===
Columbus has over 170 notable buildings listed on the National Register of Historic Places; it also maintains its own register, the Columbus Register of Historic Properties, with 82 entries. The city also maintains four historic districts not listed on its register: German Village, Italian Village, Victorian Village, and the Brewery District.
Construction of the Ohio Statehouse began in 1839 on a plot of land donated by four prominent Columbus landowners. This plot formed Capitol Square, which was not part of the city's original layout. Built of Columbus limestone from the Marble Cliff Quarry Co., the Statehouse stands on foundations deep that were laid by prison labor gangs rumored to have been composed largely of masons jailed for minor infractions.
====Demolitions and redevelopment====
Demolition has been a common trend in Columbus for a long period of time, and continues into the present day. Preservationists and the public have sometimes run into conflict with developers hoping to revitalize an area, and historically with the city and state government, which led programs of urban renewal in the 20th century.
===Museums and public art===
Columbus has a wide variety of museums and galleries. Its primary art museum is the Columbus Museum of Art, which operates its main location as well as the Pizzuti Collection, featuring contemporary art. The museum, founded in 1878, focuses on European and American art up to early modernism that includes extraordinary examples of Impressionism, German Expressionism and Cubism. Another prominent art museum in the city is the Wexner Center for the Arts, a contemporary art gallery and research facility operated by the Ohio State University.
The Ohio History Connection is headquartered in Columbus, with its flagship museum, the Ohio History Center, north of downtown. Adjacent to the museum is Ohio Village, a replica of a village around the time of the American Civil War. The Columbus Historical Society also features historical exhibits, which focus more closely on life in Columbus.
COSI is a large science and children's museum in downtown Columbus. The present building, the former Central High School, was completed in November 1999, opposite downtown on the west bank of the Scioto River. In 2009, Parents magazine named COSI one of the 10 best science centers for families in the country. Other science museums include the Orton Geological Museum and the Museum of Biological Diversity, which are both part of Ohio State University.
The Franklin Park Conservatory is the city's botanical garden, which opened in 1895. It features over 400 species of plants in a large Victorian-style glass greenhouse building that includes rain forest, desert and Himalayan mountain biomes. The conservatory is located just east of Downtown in Franklin Park
Biographical museums include the Thurber House (documenting the life of cartoonist James Thurber), the Jack Nicklaus Museum (documenting the golfer's career, located on the OSU campus) and the Kelton House Museum and Garden, the latter of which being a historic house museum memorializing three generations of the Kelton family, the house's use as a documented station on the Underground Railroad, and overall Victorian life.
The National Veterans Memorial and Museum, which opened in 2018, focuses on the personal stories of military veterans throughout U.S. history. The museum replaced the Franklin County Veterans Memorial, which opened in 1955.
Other notable museums in the city include the Central Ohio Fire Museum, Billy Ireland Cartoon Library & Museum and the Ohio Craft Museum.
===Performing arts===
Columbus is the home of many performing arts institutions including the Columbus Symphony Orchestra, Opera Columbus, BalletMet Columbus, the ProMusica Chamber Orchestra, CATCO, Columbus Children's Theatre, Shadowbox Live, and the Columbus Jazz Orchestra. Throughout the summer, the Actors' Theatre of Columbus offers free performances of Shakespearean plays in an open-air amphitheater in Schiller Park in historic German Village.
The Columbus Youth Ballet Academy was founded in the 1980s by ballerina and artistic director Shir Lee Wu, a discovery of Martha Graham. Wu was the long-time artistic director of the Columbus City Ballet School and taught classes there until her death in 2021.
Columbus has several large concert venues, including the Nationwide Arena, Value City Arena, Express Live!, Mershon Auditorium and the Newport Music Hall.
In May 2009, the Lincoln Theatre, formerly a center for Black culture in Columbus, reopened after an extensive restoration. Not far from the Lincoln Theatre is the King Arts Complex, which hosts a variety of cultural events. The city also has several theaters downtown, including the historic Palace Theatre, the Ohio Theatre and the Southern Theatre. Broadway Across America often presents touring Broadway musicals in these larger venues. The Vern Riffe Center for Government and the Arts houses the Capitol Theatre and three smaller studio theaters, providing a home for resident performing arts companies.
====Film====
Movies filmed in the Columbus metropolitan area include Teachers in 1984, Tango & Cash in 1989, Little Man Tate in 1991, Air Force One in 1997, Traffic in 2000, Speak in 2004, Bubble in 2005, Liberal Arts in 2012, Parker in 2013, and I Am Wrath in 2016, Aftermath in 2017, They/Them/Us in 2021, and Bones and All in 2022. The 2018 film Ready Player One is set in Columbus, though not filmed in the city.
==Sports==
===Professional teams===
Columbus hosts two major league professional sports teams: the Columbus Blue Jackets of the National Hockey League (NHL), which play at Nationwide Arena, and the Columbus Crew of Major League Soccer (MLS), which play at Lower.com Field. The Crew previously played at Historic Crew Stadium, the first soccer-specific stadium built in the United States for a Major League Soccer team. The Crew were one of the original members of MLS and won their first MLS Cup in 2008, a second title in 2020, and a third title in 2023. The Columbus Crew moved into Lower.com Field in the summer of 2021, which will also feature a mixed-use development site named Confluence Village.
The Columbus Clippers, the International League affiliate of the Cleveland Guardians, play in Huntington Park, which opened in 2009.
The city was home to the Panhandles/Tigers football team from 1901 to 1926; they are credited with playing in the first NFL game against another NFL opponent. In the late 1990s, the Columbus Quest won the only two championships during American Basketball League's two-and-a-half season existence.
The Ohio Aviators were based in Obetz, Ohio, and began play in the only PRO Rugby season before the league folded.
Since 2023, Columbus has been home to the Columbus Fury women's professional volleyball team, one of seven teams to launch with the Pro Volleyball Federation. The team plays home games at Nationwide Arena.
===Ohio State Buckeyes===
Columbus is home to one of the nation's most competitive intercollegiate programs, the Ohio State Buckeyes of Ohio State University. The program has placed in the top 10 final standings of the Director's Cup five times since 2000–2001, including No. 3 for the 2002–2003 season and No. 4 for the 2003–2004 season. The university funds 36 varsity teams, consisting of 17 male, 16 female and three co-educational teams. In 2007–2008 and 2008–2009, the program generated the second-most revenue for college programs behind the Texas Longhorns of The University of Texas at Austin.
The Ohio State Buckeyes are a member of the NCAA's Big Ten Conference, and their football team plays home games at Ohio Stadium. The Ohio State–Michigan football game (known colloquially as "The Game") is the final game of the regular season and is played in November each year, alternating between Columbus and Ann Arbor, Michigan. In 2000, ESPN ranked the Ohio State–Michigan game as the greatest rivalry in North American sports. Moreover, "Buckeye fever" permeates Columbus culture year-round and forms a major part of Columbus's cultural identity. Former New York Yankees owner George Steinbrenner, an Ohio native who received a master's degree from Ohio State and coached in Columbus, was an Ohio State football fan and major donor to the university who contributed to the construction of the band facility at the renovated Ohio Stadium, which bears his family's name.
During the winter months, the Buckeyes basketball and hockey teams are also major sporting attractions.
===Other sports===
Columbus has a long history in motorsports, hosting the world's first 24-hour car race at the Columbus Driving Park in 1905, which was organized by the Columbus Auto Club. The Columbus Motor Speedway was built in 1945 and held its first motorcycle race in 1946. In 2010, the Ohio State University student-built Buckeye Bullet 2, a fuel-cell vehicle, set an FIA world speed record for electric vehicles in reaching 303.025 mph, eclipsing the previous record of 302.877 mph.
The annual All American Quarter Horse Congress, the world's largest single-breed horse show, attracts approximately 500,000 visitors to the Ohio Expo Center each October.
Columbus hosts the annual Arnold Sports Festival. Hosted by Arnold Schwarzenegger, the event has grown to eight Olympic sports and 22,000 athletes competing in 80 events.
Westside Barbell, a world-renowned powerlifting gym, is located in Columbus. Its founder, Louie Simmons, is known for his popularization of the "Conjugate Method," while he is also credited with inventing training machines for reverse hyper-extensions and belt squats. Westside Barbell is known for producing multiple world record holders in powerlifting.
The Columbus Bullies were two-time champions of the American Football League (1940–1941). The Columbus Thunderbolts were formed in 1991 for the Arena Football League, and then relocated to Cleveland as the Cleveland Thunderbolts; the Columbus Destroyers were the next team of the AFL, playing from 2004 until the league's demise in 2008 and returned for single season in 2019 until the league folded a second time.
Ohio Roller Derby (formerly Ohio Roller Girls) was founded in Columbus in 2005 and still competes internationally in Women's Flat Track Derby Association play. The team is regularly ranked in the top 60 internationally.
==Parks and attractions==
Columbus's Recreation and Parks Department oversees about 370 city parks. Also in the area are 19 regional parks and the Metro Parks, which are part of the Columbus and Franklin County Metropolitan Park District.
These parks include Clintonville's Whetstone Park and the Columbus Park of Roses, a rose garden. The Chadwick Arboretum on Ohio State's campus features a large and varied collection of plants, while its Olentangy River Wetland Research Park is an experimental wetland open to the public. Downtown, the painting A Sunday Afternoon on the Island of La Grande Jatte is represented in topiary at Columbus's Topiary Park. Also near downtown, the Scioto Audubon Metro Park on the Whittier Peninsula opened in 2009 and includes a large Audubon nature center focused on the birdwatching the area is known for.
The Columbus Zoo and Aquarium's collections include lowland gorillas, polar bears, manatees, Siberian tigers, cheetahs and kangaroos. Also in the zoo complex is the Zoombezi Bay water park and amusement park.
===Fairs and festivals===
Annual festivities in Columbus include the Ohio State Fair – one of the largest state fairs in the country – as well as the Columbus Arts Festival and the Jazz & Rib Fest, both of which occur on the downtown riverfront.
In mid-May from 2007 to 2018, Columbus was home to Rock on the Range, which was held at Historic Crew Stadium and marketed as America's biggest rock festival. The festival, which took place on a Friday, Saturday and Sunday, has hosted Metallica, Red Hot Chili Peppers, Slipknot and other notable bands. In May 2019, it was officially replaced by the Sonic Temple Art & Music Festival.
During the first weekend in June, the bars of Columbus's North Market District host the Park Street Festival, which attracts thousands of visitors to a massive party in bars and on the street. June's second-to-last weekend sees one of the Midwest's largest gay pride parades, Columbus Pride, reflecting the city's sizable gay population. During the last weekend of June, Goodale Park hosts ComFest (short for "Community Festival"), an immense three-day music festival marketed as the largest non-commercial festival in the U.S., with art vendors, live music on multiple stages, hundreds of local social and political organizations, body painting and beer.
The city's largest dining event, Restaurant Week Columbus, is held twice a year in mid-January and mid-July. In 2010, more than 40,000 diners went to 40 participating restaurants, and $5,000 (~$ in ) was donated the Mid-Ohio Foodbank on behalf of sponsors and participating restaurants.
Around the Fourth of July, Columbus hosts Red, White & Boom! on the Scioto riverfront downtown, attracting crowds of over 500,000 people and featuring the largest fireworks display in Ohio.
The Short North is host to the monthly Gallery Hop, which attracts hundreds to the neighborhood's art galleries (which all open their doors to the public until late at night) and street musicians. The Hilltop Bean Dinner is an annual event held on Columbus's West Side that celebrates the city's Civil War heritage near the historic Camp Chase Cemetery. At the end of September, German Village throws an annual Oktoberfest celebration that features German food, beer, music and crafts.
Columbus also hosts many conventions in the Greater Columbus Convention Center, a large convention center on the north edge of downtown. Completed in 1993, the convention center was designed by architect Peter Eisenman, who also designed the Wexner Center.
===Shopping===
Both of the metropolitan area's major shopping centers are located in Columbus: Easton Town Center and Polaris Fashion Place.
Developer Richard E. Jacobs built the area's first three major shopping malls in the 1960s: Westland, Northland and Eastland. Near Northland Mall was The Continent, an open-air mall in the Northland area, mostly vacant and pending redevelopment. Columbus City Center was built downtown in 1988, alongside the first location of Lazarus; this mall closed in 2009 and was demolished in 2011. Easton Town Center was built in 1999 and Polaris Fashion Place in 2001.
==Environment==
The City of Columbus has focused on reducing its environmental impact and carbon footprint. In 2020, a citywide ballot measure was approved, giving Columbus an electricity aggregation plan which will supply it with 100% renewable energy by the start of 2023. Its vendor, AEP Energy, plans to construct new wind and solar farms in Ohio to help supply the electricity.
The largest sources of pollution in the county, as of 2019, are Ohio State University's McCracken Power Plant, the landfill operated by the Solid Waste Authority of Central Ohio (SWACO) and the Anheuser-Busch Columbus Brewery. Anheuser-Busch has a company-wide goal of reducing emissions by 25% by 2025. Ohio State plans to construct a new heat and power plant, also powered by fossil fuels, but set to reduce emissions by about 30%. SWACO manages to capture 75% of its methane emissions to use in producing energy, and is looking to reduce emissions further.
==Government==
===Mayor and city council===
The city is administered by a mayor and a nine-member unicameral council elected in two classes every two years to four-year terms at large. Columbus is the largest city in the United States that elects its city council at large as opposed to districts. The mayor appoints the director of safety and the director of public service. The people elect the auditor, municipal court clerk, municipal court judges and city attorney. A charter commission, elected in 1913, submitted a new charter in May 1914, offering a modified federal form, with a number of progressive features, such as nonpartisan ballot, preferential voting, recall of elected officials, the referendum and a small council elected at large. The charter was adopted, effective January 1, 1916. Andrew Ginther has been the mayor of Columbus since 2016.
===Government offices===
As Ohio's capital and the county seat, Columbus hosts numerous federal, state, county and city government offices and courts.
Federal offices include the Joseph P. Kinneary U.S. Courthouse, one of several courts for the District Court for the Southern District of Ohio, after moving from 121 E. State St. in 1934. Another federal office, the John W. Bricker Federal Building, has offices for U.S. Senator Sherrod Brown, as well as for the Internal Revenue Service, the Social Security Administration and the Departments of Housing & Urban Development and Agriculture.
The State of Ohio's capitol building, the Ohio Statehouse, is located in the center of downtown on Capitol Square. It houses the Ohio House of Representatives and Ohio Senate. It also contains the ceremonial offices of the governor, and state auditor. The Supreme Court, Court of Claims and Judicial Conference are located in the Thomas J. Moyer Ohio Judicial Center downtown by the Scioto River. The building, built in 1933 to house 10 state agencies along with the State Library of Ohio, became the Supreme Court after extensive renovations from 2001 to 2004.
Franklin County operates the Franklin County Government Center, a complex at the southern end of downtown Columbus. The center includes the county's municipal court, common pleas court, correctional center, juvenile detention center and sheriff's office.
Near City Hall, the Michael B. Coleman Government Center holds offices for the departments of building and zoning services, public service, development and public utilities. Also nearby is 77 North Front Street, which holds Columbus's city attorney office, income-tax division, public safety, human resources, civil service and purchasing departments. The structure, built in 1929, was the police headquarters until 1991, and was then dormant until it was given a $34 million renovation from 2011 to 2013.
===Emergency services and homeland security===
Municipal police duties are performed by the Columbus Division of Police, while emergency medical services (EMS) and fire protection are through the Columbus Division of Fire.
Ohio Homeland Security operates the Strategic Analysis and Information Center (SAIC) fusion center in Columbus's Hilltop neighborhood. The facility is the state's primary public intelligence hub and one of the few in the country that uses state, local, federal and private resources.
===Social services and homelessness===
Columbus has a history of governmental and nonprofit support for low-income residents and the homeless. Nevertheless, the homelessness rate has steadily risen since at least 2007. Poverty and differences in quality of life have grown, as well; Columbus was noted as the second-most economically segregated large metropolitan area in 2015, in a study by the University of Toronto. It also ranked 45th of the 50 largest metropolitan areas in terms of social mobility, according to a 2015 Harvard University study.
==Education==
===Colleges and universities===
Columbus is the home of two public colleges: the Ohio State University, one of the largest college campuses in the United States, and Columbus State Community College. In 2009, Ohio State University was ranked No. 19 in the country by U.S. News & World Report on its list of best public universities, and No. 56 overall, scoring in the first tier of schools nationally. Some of Ohio State's graduate school programs placed in the top 5, including No. 5 for both best veterinary programs and best pharmacy programs. The specialty graduate programs of social psychology was ranked No. 2, dispute resolution was No. 5, vocational education was No. 2, and elementary education, secondary teacher education, administration/supervision was No. 5.
Private institutions in Columbus include Capital University Law School, the Columbus College of Art and Design, Fortis College, DeVry University, Ohio Business College, Miami-Jacobs Career College, Ohio Institute of Health Careers, Bradford School and Franklin University, as well as the religious schools Bexley Hall Episcopal Seminary, Mount Carmel College of Nursing, Ohio Dominican University, Pontifical College Josephinum and Trinity Lutheran Seminary. Three major suburban schools also have an influence on Columbus's educational landscape: Bexley's Capital University, Westerville's Otterbein University and Delaware's Ohio Wesleyan University.
===Primary and secondary schools===
Columbus City Schools (CCS) is the largest district in Ohio, with 55,000 pupils. CCS operates 142 elementary, middle and high schools, including a number of magnet schools (which are referred to as alternative schools within the school system).
The suburbs operate their own districts, typically serving students in one or more townships, with districts sometimes crossing municipal boundaries. The Roman Catholic Diocese of Columbus also operates several parochial elementary and high schools. The area's second-largest school district is South-Western City Schools, which encompasses southwestern Franklin County, including a slice of Columbus itself. Other portions of Columbus are zoned to the Dublin, Hilliard, New Albany-Plain, Westerville and Worthington school districts.
There are also several private schools in the area, such as St. Paul's Lutheran School, a K-8 Christian school of the Wisconsin Evangelical Lutheran Synod in Columbus.
Some sources determine that the first kindergarten in the United States was established here by Louisa Frankenberg, a former student of Friedrich Fröbel.
In addition, Indianola Junior High School (now the Graham Elementary and Middle School) became the nation's first junior high school in 1909, helping to bridge the difficult transition from elementary to high school at a time when only 48% of students continued their education after the ninth grade.
===Libraries===
The Columbus Metropolitan Library (CML) has served central Ohio residents since 1873. The system has 23 locations throughout Central Ohio, with a total collection of 3 million items. This library is one of the country's most-used library systems and is consistently among the top-ranked large city libraries according to Hennen's American Public Library Ratings. CML was rated the No. 1 library system in the nation in 1999, 2005 and 2008. It has been in the top four every year since 1999, when the rankings were first published in the American Libraries magazine, often challenging upstate neighbor Cuyahoga County Public Library for the top spot.
===Weekend education===
The classes of the Columbus Japanese Language School, a weekend Japanese school, are held in a facility from the school district in Marysville, while the school office is in Worthington. Previously it held classes at facilities in the city of Columbus.
==Media==
Several weekly and daily newspapers serve Columbus and Central Ohio. The major daily newspaper in Columbus is The Columbus Dispatch. There are also neighborhood- or suburb-specific papers, such as the Dispatch Printing Company's ThisWeek Community News, the Columbus Messenger, the Clintonville Spotlight and the Short North Gazette. The Lantern and 1870 serve the Ohio State University community. Alternative arts, culture or politics-oriented papers include ALIVE (formerly the independent Columbus Alive and now owned by the Columbus Dispatch), Columbus Free Press and Columbus Underground (digital-only). The Columbus Magazine, CityScene, 614 Magazine and Columbus Monthly are the city's magazines.
Columbus is the base for 12 television stations and is the 32nd-largest television market as of September 24, 2016. Columbus is also home to the 36th-largest radio market.
==Infrastructure==
===Healthcare===
Numerous medical systems operate in Columbus and Central Ohio. These include OhioHealth, which has three hospitals in the city proper: Grant Medical Center, Riverside Methodist Hospital, and Doctors Hospital; Mount Carmel Health System, which has one hospital among other facilities; the Ohio State University Wexner Medical Center, which has a primary hospital complex and an east campus in Columbus; and Nationwide Children's Hospital, which is an independently operated hospital for pediatric health care. Hospitals in Central Ohio are ranked favorably by the U.S. News & World Report, where numerous hospitals are ranked as among the best in particular fields in the United States. Nationwide Children's is regarded as among the top 10 children's hospitals in the country, according to the report.
===Utilities===
Numerous utility companies operate in Central Ohio. Within Columbus, power is sourced from Columbus Southern Power, an American Electric Power subsidiary. Natural gas is provided by Columbia Gas of Ohio, while water is sourced from the City of Columbus Division of Water.
===Transportation===
====Local roads, grid and address system====
The city's two main corridors since its founding are Broad and High Streets. They both traverse beyond the extent of the city; High Street is the longest in Columbus, running (23.4 across the county), while Broad Street is longer across the county, at .
The city's street plan originates downtown and extends into the old-growth neighborhoods, following a grid pattern with the intersection of High Street (running north–south) and Broad Street (running east–west) at its center. North–south streets run 12 degrees west of due north, parallel to High Street; the avenues (vis. Fifth Avenue, Sixth Avenue, Seventh Avenue, and so on) run 12 degrees off from east–west.
The address system begins its numbering at the intersection of Broad and High, with numbers increasing in magnitude with distance from Broad or High, as well as cardinal directions used alongside street names. Numbered avenues begin with First Avenue, about north of Broad Street, and increase in number as one progresses northward. Numbered streets begin with Second Street, which is two blocks west of High Street, and Third Street, which is a block east of High Street, then progress eastward from there. Even-numbered addresses are on the north and east sides of streets, putting odd addresses on the south and west sides of streets. A difference of 700 house numbers means a distance of about (along the same street). The Main Street Bridge opened on July 30, 2010. The bridge has three lanes for vehicular traffic (one westbound and two eastbound) and another separated lane for pedestrians and bikes. The Rich Street Bridge opened in July 2012 adjacent to the Main Street Bridge, connecting Rich Street on the east side of the river with Town Street on the west. The Lane Avenue Bridge is a cable-stayed bridge that opened on November 14, 2003, in the University District. The bridge spans the Olentangy River with three lanes of traffic each way.
====Airports====
The city's primary airport, John Glenn Columbus International Airport, is on the city's east side. Formerly known as Port Columbus, John Glenn provides service to Toronto, Ontario, Canada, and Cancun, Mexico (on a seasonal basis), as well as to most domestic destinations, including all the major hubs along with San Francisco, Salt Lake City and Seattle. The airport was a hub for discount carrier Skybus Airlines and continues to be home to NetJets, the world's largest fractional ownership air carrier. According to a 2005 market survey, John Glenn Columbus International Airport attracts about 50% of its passengers from outside of its radius primary service region. It is the 52nd-busiest airport in the United States by total passenger boardings.
Rickenbacker International Airport, in southern Franklin County, is a major cargo facility that is used by the Ohio Air National Guard. Allegiant Air offers nonstop service from Rickenbacker to Florida destinations. Ohio State University Don Scott Airport and Bolton Field are other large general-aviation facilities in the Columbus area.
=====Aviation history=====
In 1907, 14-year-old Cromwell Dixon built the SkyCycle, a pedal-powered blimp, which he flew at Driving Park. Three years later, one of the Wright brothers' exhibition pilots, Phillip Parmalee, conducted the world's first commercial cargo flight when he flew two packages containing 88 kilograms of silk from Dayton to Columbus in a Wright Model B.
Military aviators from Columbus distinguished themselves during World War I. Six Columbus pilots, led by top ace Eddie Rickenbacker, achieved 42 "kills" – a full 10% of all US aerial victories in the war, and more than the aviators of any other American city.
After the war, Port Columbus Airport (now known as John Glenn Columbus International Airport) became the axis of a coordinated rail-to-air transcontinental system that moved passengers from the East Coast to the West. TAT, which later became TWA, provided commercial service, following Charles Lindbergh's promotion of Columbus to the nation for such a hub. Following the failure of a bond levy in 1927 to build the airport, Lindbergh campaigned in the city in 1928, and the next bond levy passed that year.
====Public transit====
Columbus maintains a widespread municipal bus service called the Central Ohio Transit Authority (COTA). The service operates 41 routes with a fleet of 440 buses, serving approximately 19 million passengers per year. COTA operates 23 regular fixed-service routes, 14 express services, a bus rapid transit route, a free downtown circulator, night service, an airport connector and other services. LinkUS, an initiative between COTA, the city, and the Mid-Ohio Regional Planning Commission, is planning to add more rapid transit to Columbus, with three proposed corridors operating by 2030, and potentially a total of five by 2050.
Intercity bus service is provided at the Columbus Bus Station by Greyhound, Barons Bus Lines, Miller Transportation, GoBus and other carriers.
Columbus does not have passenger rail service. The city's major train station, Union Station, was a stop along Amtrak's National Limited train service until 1977 and was razed in 1979, and the Greater Columbus Convention Center now stands in its place. Until Amtrak's founding in 1971, the Penn Central ran the Cincinnati Limited to Cincinnati to the southwest (in prior years the train continued to New York City to the east); the Ohio State Limited between Cincinnati and Cleveland, with Union Station serving as a major intermediate stop (the train going unnamed between 1967 and 1971); and the Spirit of St. Louis, which ran between St. Louis and New York City until 1971. The station was also a stop along the Pennsylvania Railroad, the New York Central Railroad, the Chesapeake and Ohio Railway, the Baltimore and Ohio Railroad, the Norfolk and Western Railway, the Cleveland, Columbus and Cincinnati Railroad, and the Pittsburgh, Cincinnati, Chicago and St. Louis Railroad. As the city lacks local, commuter or intercity trains, Columbus is now the largest city and metropolitan area in the U.S. without any passenger rail service. Numerous proposals to return rail service have been introduced; currently Amtrak plans to restore service to Columbus by 2035.
====Cycling network====
Cycling as transportation is steadily increasing in Columbus with its relatively flat terrain, intact urban neighborhoods, large student population and off-road bike paths. The city has put forth the 2012 Bicentennial Bikeways Plan, as well as a move toward a Complete Streets policy. Grassroots efforts such as Bike to Work Week, Consider Biking, Yay Bikes, Third Hand Bicycle Co-op, Franklinton Cycleworks and Cranksters, a local radio program focused on urban cycling, have contributed to cycling as transportation.
Columbus also hosts urban cycling "off-shots" with messenger-style "alleycat" races, as well as unorganized group rides, a monthly Critical Mass ride, bicycle polo, art showings, movie nights and a variety of bicycle-friendly businesses and events throughout the year. All this activity occurs despite Columbus's frequently inclement weather.
The Main Street Bridge, opened in 2010, features a dedicated bike and pedestrian lane separated from traffic.
The city has its own public bicycle system. CoGo Bike Share has a network of about 600 bicycles and 80 docking stations. PBSC Urban Solutions, a company based in Canada, supplies technology and equipment. Bird electric scooters have also been introduced.
====Modal share====
The city of Columbus has a higher-than-average percentage of households without a car. In 2015, 9.8% of Columbus households lacked a car, a number that fell slightly to 9.4% in 2016. The national average was 8.7% in 2016. Columbus averaged 1.55 cars per household in 2016, compared to a national average of 1.8.
==Notable people==
==Sister cities==
Columbus has 10 sister cities as designated by Sister Cities International. Columbus established its first sister city relationship in 1955 with Genoa, Italy. To commemorate this relationship, Columbus received as a gift from the people of Genoa, a bronze statue of Christopher Columbus. The statue overlooked Broad Street in front of Columbus City Hall from 1955 to 2020; it was removed during the George Floyd protests.
List of sister cities:
|
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] |
5,951 |
Cleveland
|
Cleveland is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located along the southern shore of Lake Erie, it is situated across the Canada–United States maritime border and lies approximately west of Pennsylvania. Cleveland is the most populous city on Lake Erie, the second-most populous city in Ohio, and the 53rd-most populous city in the U.S. with a population of 372,624 in 2020. The city anchors the Cleveland metropolitan area, the 33rd-largest in the U.S. at 2.18 million residents, as well as the larger Cleveland–Akron–Canton combined statistical area with 3.63 million residents.
Cleveland was founded in 1796 near the mouth of the Cuyahoga River as part of the Connecticut Western Reserve in modern-day Northeast Ohio by General Moses Cleaveland, after whom the city was named. The city's location on the river and the lake shore allowed it to grow into a major commercial and industrial metropolis by the late 19th century, attracting large numbers of immigrants and migrants. It was among the top 10 largest U.S. cities by population for much of the 20th century, a period that saw the development of the city's cultural institutions. By the 1960s, Cleveland's economy began to slow down as manufacturing declined and suburbanization occurred.
Cleveland is a port city, connected to the Atlantic Ocean via the Saint Lawrence Seaway. Its economy relies on diverse sectors that include higher education, manufacturing, financial services, healthcare, and biomedicals. The city serves as the headquarters of the Federal Reserve Bank of Cleveland, as well as several major companies. The GDP for the Greater Cleveland MSA was US$138.3 billion in 2022.
Designated as a global city by the Globalization and World Cities Research Network, Cleveland is home to several major cultural institutions, including the Cleveland Museum of Art, the Cleveland Museum of Natural History, the Cleveland Orchestra, the Cleveland Public Library, Playhouse Square, and the Rock and Roll Hall of Fame, as well as Case Western Reserve University. Known as "The Forest City" among many other nicknames, Cleveland serves as the center of the Cleveland Metroparks nature reserve system. Cleaveland oversaw the New England–style design of the plan for what would become the modern downtown area, centered on Public Square, before returning to Connecticut, never again to visit Ohio.
The first permanent European settler in Cleveland was Lorenzo Carter, who built a cabin on the banks of the Cuyahoga River. The emerging community served as an important supply post for the U.S. during the Battle of Lake Erie in the War of 1812. Locals adopted Commodore Oliver Hazard Perry as a civic hero and erected a monument in his honor decades later. Largely through the efforts of the settlement's first lawyer Alfred Kelley, the village of Cleveland was incorporated on December 23, 1814.
Despite the nearby swampy lowlands and harsh winters, the town's waterfront location proved advantageous, giving it access to Great Lakes trade. It grew rapidly after the 1832 completion of the Ohio and Erie Canal. This key link between the Ohio River and the Great Lakes connected Cleveland to the Atlantic Ocean via the Erie Canal and Hudson River, and later via the Saint Lawrence Seaway. That same year, it nearly erupted into open warfare with neighboring Ohio City over a bridge connecting the two communities. Ohio City remained an independent municipality until its annexation by Cleveland in 1854. Cleveland (code-named "Station Hope") was a major stop on the Underground Railroad for escaped African American slaves en route to Canada. The city also served as an important center for the Union during the American Civil War. Decades later, in July 1894, the wartime contributions of those serving the Union from Cleveland and Cuyahoga County would be honored with the Soldiers' and Sailors' Monument on Public Square.
=== Growth and expansion ===
The Civil War vaulted Cleveland into the first rank of American manufacturing cities and fueled unprecedented growth. Its prime geographic location as a transportation hub on the Great Lakes played an important role in its development as an industrial and commercial center. In 1870, John D. Rockefeller founded Standard Oil in Cleveland, and in 1885, he moved its headquarters to New York City, which had become a center of finance and business.
Cleveland's economic growth and industrial jobs attracted large waves of immigrants from Southern and Eastern Europe as well as Ireland. The Cleveland Streetcar Strike of 1899 was one of the more violent instances of labor strife in the city during this period.
By 1910, Cleveland had become known as the "Sixth City" due to its status at the time as the sixth-largest U.S. city. Its automotive companies included Peerless, Chandler, and Winton, maker of the first car driven across the U.S. Other manufacturing industries in Cleveland included steam cars produced by White and electric cars produced by Baker. The city counted major Progressive Era politicians among its leaders, most prominently the populist Mayor Tom L. Johnson, who was responsible for the development of the Cleveland Mall Plan. The era of the City Beautiful movement in Cleveland architecture saw wealthy patrons support the establishment of the city's major cultural institutions. The most prominent among them were the Cleveland Museum of Art, which opened in 1916, and the Cleveland Orchestra, established in 1918.
In addition to the large immigrant population, African American migrants from the rural South arrived in Cleveland (among other Northeastern and Midwestern cities) as part of the Great Migration for jobs, constitutional rights, and relief from racial discrimination. By 1920, the year in which the Cleveland Indians won their first World Series championship, Cleveland had grown into a densely-populated metropolis of 796,841, making it the fifth-largest city in the nation,
At this time, Cleveland saw the rise of radical labor movements, most prominently the Industrial Workers of the World (IWW), in response to the conditions of the largely immigrant and migrant workers. In 1919, the city attracted national attention amid the First Red Scare for the Cleveland May Day Riots, in which local socialist and IWW demonstrators clashed with anti-socialists. The riots occurred during the broader strike wave that swept the U.S. that year.
Cleveland's population continued to grow throughout the Roaring Twenties. The decade saw the establishment of the city's Playhouse Square, and the rise of the risqué Short Vincent. The Bal-Masque balls of the avant-garde Kokoon Arts Club scandalized the city. Jazz came to prominence in Cleveland during this period. Prohibition first took effect in Ohio in May 1919 (although it was not well-enforced in Cleveland), became law with the Volstead Act in 1920, and was eventually repealed nationally by Congress in 1933. The ban on alcohol led to the rise of speakeasies throughout the city and organized crime gangs, such as the Mayfield Road Mob, who smuggled bootleg liquor across Lake Erie from Canada into Cleveland.
The era of the flapper marked the beginning of the golden age in Downtown Cleveland retail, centered on major department stores Higbee's, Bailey's, the May Company, Taylor's, Halle's, and Sterling Lindner Davis, which collectively represented one of the largest and most fashionable shopping districts in the country, often compared to New York's Fifth Avenue. In 1929, Cleveland hosted the first of many National Air Races, and Amelia Earhart flew to the city from Santa Monica, California in the Women's Air Derby. The Van Sweringen brothers commenced construction of the Terminal Tower skyscraper in 1926 and oversaw it to completion in 1927. By the time the building was dedicated as part of Cleveland Union Terminal in 1930, the city had a population of over 900,000.
On December 7, 1941, Imperial Japan attacked Pearl Harbor and declared war on the U.S. Two of the victims of the attack were Cleveland natives – Rear Admiral Isaac C. Kidd and ensign William Halloran. The attack signaled America's entry into World War II. A major hub of the "Arsenal of Democracy", Cleveland under Mayor Frank Lausche contributed massively to the U.S. war effort as the fifth largest manufacturing center in the nation. During his tenure, Lausche also oversaw the establishment of the Cleveland Transit System, the predecessor to the Greater Cleveland Regional Transit Authority.
=== Late 20th and early 21st centuries ===
After the war, Cleveland initially experienced an economic boom, and businesses declared the city to be the "best location in the nation". In 1949, the city was named an All-America City for the first time, and in 1950, its population reached 914,808. Additionally, the 1950s saw the rising popularity of a new music genre that local WJW (AM) disc jockey Alan Freed dubbed "rock and roll".
However, by the 1960s, Cleveland's economy began to slow down, and residents increasingly sought new housing in the suburbs, reflecting the national trends of suburban growth following federally subsidized highways. Industrial restructuring, particularly in the steel and automotive industries, resulted in the loss of numerous jobs in Cleveland and the region, and the city suffered economically. The burning of the Cuyahoga River in June 1969 brought national attention to the issue of industrial pollution in Cleveland and served as a catalyst for the American environmental movement.
Housing discrimination and redlining against African Americans led to racial unrest in Cleveland and numerous other Northern U.S. cities. In Cleveland, the Hough riots erupted from July 18 to 24, 1966, and the Glenville Shootout took place on July 23, 1968. In November 1967, Cleveland became the first major American city to elect an African American mayor, Carl B. Stokes, who served from 1968 to 1971 and played an instrumental role in restoring the Cuyahoga River.
During the 1970s, Cleveland became known as "Bomb City U.S.A." due to several bombings that shook the city, mostly due to organized crime rivalries. In December 1978, during the turbulent tenure of Dennis Kucinich as mayor, Cleveland became the first major American city since the Great Depression to enter into a financial default on federal loans. The national recession of the early 1980s "further eroded the city's traditional economic base." While unemployment during the period peaked in 1983, Cleveland's rate of 13.8% was higher than the national average due to the closure of several steel production centers.
The city began a gradual economic recovery under Mayor George V. Voinovich in the 1980s. Downtown saw the construction of the Key Tower and 200 Public Square skyscrapers, as well as the development of the Gateway Sports and Entertainment Complex – consisting of Progressive Field and Rocket Arena – and North Coast Harbor, including the Rock and Roll Hall of Fame, Cleveland Browns Stadium, and the Great Lakes Science Center. Although the city emerged from default in 1987,
Nevertheless, by the turn of the 21st century, Cleveland succeeded in developing a more diversified economy and gained a national reputation as a center for healthcare and the arts. The city's downtown and several neighborhoods have experienced significant population growth since 2010, while overall population decline has slowed. Challenges remain for the city, with improvement of city schools, economic development of neighborhoods, and continued efforts to tackle poverty, homelessness, and urban blight being top municipal priorities.
== Geography ==
According to the U.S. Census Bureau, the city has a total area of , of which is land and is water. The shore of Lake Erie is above sea level; however, the city lies on a series of irregular bluffs lying roughly parallel to the lake. In Cleveland these bluffs are cut principally by the Cuyahoga River, Big Creek, and Euclid Creek.
The land rises quickly from the lake shore elevation of 569 feet. Public Square, less than inland, sits at an elevation of , and Hopkins Airport, inland from the lake, is at an elevation of .
Cleveland borders several inner-ring and streetcar suburbs.
Completed in 1927 and dedicated in 1930 as part of the Cleveland Union Terminal complex, the Terminal Tower was the tallest building in North America outside New York City until 1964 and the tallest in the city until 1991. It is a prototypical Beaux-Arts skyscraper. The two other major skyscrapers on Public Square, Key Tower (the tallest building in Ohio) and 200 Public Square, combine elements of Art Deco architecture with postmodern designs.
Running east from Public Square through University Circle is Euclid Avenue, which was known as "Millionaires' Row" for its prestige and elegance as a residential street. In the late 1880s, writer Bayard Taylor described it as "the most beautiful street in the world".
Nicknamed Cleveland's "Crystal Palace", the five-story Cleveland Arcade (also known as the Old Arcade) was built in 1890 and renovated in 2001 as a Hyatt Regency Hotel. Another major architectural landmark, the Cleveland Trust Company Building, was completed in 1907 and renovated in 2015 as a downtown Heinen's supermarket. Cleveland's historic ecclesiastical architecture includes the Presbyterian Old Stone Church, the onion domed St. Theodosius Russian Orthodox Cathedral, and the Roman Catholic Cathedral of St. John the Evangelist along with several other ethnically inspired Catholic churches.
File:Arcade (48249762776).jpg|Cleveland Arcade, 1890
File:Cleveland Trust Company Building, Euclid Avenue and East 9th Street, Cleveland, OH.jpg|Cleveland Trust Company Building, 1907
File:Palace lobby.jpg|Connor Palace Theatre, 1922
File:Cleveland Skyline (26381354620).jpg|Terminal Tower from Euclid Avenue
File:Grand Foyer, Severance Hall, University Circle, Cleveland, OH - 52992001701.jpg|Grand foyer of Severance Hall, 1931
=== Neighborhoods ===
The Cleveland City Planning Commission has officially designated 34 neighborhoods in Cleveland. Centered on Public Square, Downtown Cleveland is the city's central business district, encompassing a wide range of subdistricts, such as the Nine-Twelve District, the Campus District, the Civic Center, East 4th Street, and Playhouse Square. It also historically included the lively Short Vincent entertainment district. Mixed-use areas, such as the Warehouse District and the Superior Arts District, are occupied by industrial and office buildings as well as restaurants, cafes, and bars.
Clevelanders geographically define themselves in terms of whether they live on the east or west side of the Cuyahoga River. The East Side includes the neighborhoods of Buckeye–Shaker, Buckeye–Woodhill, Central, Collinwood (including Nottingham), Euclid–Green, Fairfax, Glenville, Goodrich–Kirtland Park (including Asiatown), Hough, Kinsman, Lee–Miles (including Lee–Harvard and Lee–Seville), Mount Pleasant, St. Clair–Superior, Union–Miles Park, and University Circle (including Little Italy). The West Side includes the neighborhoods of Brooklyn Centre, Clark–Fulton, Cudell, Detroit–Shoreway, Edgewater, Ohio City, Old Brooklyn, Stockyards, Tremont (including Duck Island), West Boulevard, and the four neighborhoods colloquially known as West Park: Kamm's Corners, Jefferson, Bellaire–Puritas, and Hopkins. The Cuyahoga Valley neighborhood (including Whiskey Island and the Flats) is situated between the East and West Sides, while Broadway–Slavic Village is sometimes referred to as the South Side.
Several neighborhoods have begun to attract the return of the middle class that left the city for the suburbs in the 1960s and 1970s. These neighborhoods are on both the West Side (Ohio City, Tremont, Detroit–Shoreway, and Edgewater) and the East Side (Collinwood, Hough, Fairfax, and Little Italy). Much of the growth has been spurred on by attracting creative class members, which has facilitated new residential development and the transformation of old industrial buildings into loft spaces for artists.
=== Climate ===
Typical of the Great Lakes region, Cleveland exhibits a continental climate with four distinct seasons, which lies in the humid continental (Köppen Dfa) zone. The climate is transitional with the Cfa humid subtropical climate. Summers are hot and humid, while winters are cold and snowy. East of the mouth of the Cuyahoga, the land elevation rises rapidly in the south. Together with the prevailing winds off Lake Erie, this feature is the principal contributor to the lake-effect snow that is typical in Cleveland (especially on the city's East Side) from mid-November until the surface of the lake freezes, usually in late January or early February. The lake effect causes a relative differential in geographical snowfall totals across the city. On the city's far West Side, the Hopkins neighborhood only reached of snowfall in a season three times since record-keeping for snow began in 1893. By contrast, seasonal totals approaching or exceeding are not uncommon as the city ascends into the Heights on the east, where the region known as the "Snow Belt" begins. Extending from the city's East Side and its suburbs, the Snow Belt reaches up the Lake Erie shore as far as Buffalo.
The all-time record high in Cleveland of was established on June 25, 1988, and the all-time record low of was set on January 19, 1994. On average, July is the warmest month with a mean temperature of , and January, with a mean temperature of , is the coldest. Normal yearly precipitation based on the 30-year average from 1991 to 2020 is . The least precipitation occurs on the western side and directly along the lake, and the most occurs in the eastern suburbs. Parts of Geauga County to the east receive over of liquid precipitation annually.
Minor League
The Cleveland Guardians – known as the Indians from 1915 to 2021 – won the World Series in 1920 and 1948. They also won the American League pennant, making the World Series in the 1954, 1995, 1997, and 2016 seasons. Between 1995 and 2001, Jacobs Field (now known as Progressive Field) sold out 455 consecutive games, a Major League Baseball record until it was broken in 2008.
Historically, the Browns have been among the most successful franchises in American football history, winning eight titles during a short period of time – 1946, 1947, 1948, 1949, 1950, 1954, 1955, and 1964. The Browns have never played in a Super Bowl, getting close five times by making it to the NFL/AFC Championship Game in 1968, 1969, 1986, 1987, and 1989. Former owner Art Modell's relocation of the Browns after the 1995 season (to Baltimore creating the Ravens), caused tremendous heartbreak and resentment among local fans. Cleveland mayor Michael R. White worked with the NFL and Commissioner Paul Tagliabue to bring back the Browns beginning in the 1999 season, retaining all team history. In Cleveland's earlier football history, the Cleveland Bulldogs won the NFL Championship in 1924, and the Cleveland Rams won the NFL Championship in 1945 before relocating to Los Angeles.
The Cavaliers won the Eastern Conference in 2007, 2015, 2016, 2017 and 2018 but were defeated in the NBA Finals by the San Antonio Spurs and then by the Golden State Warriors, respectively. The Cavs won the Conference again in 2016 and won their first NBA Championship coming back from a 3–1 deficit, finally defeating the Golden State Warriors. Afterwards, over 1.3 million people attended a parade held in the Cavs' honor on June 22, 2016, in downtown Cleveland. Previously, the Cleveland Rosenblums dominated the original American Basketball League, and the Cleveland Pipers, owned by George Steinbrenner, won the American Basketball League championship in 1962.
The Cleveland Monsters of the American Hockey League won the 2016 Calder Cup. They were the first Cleveland AHL team to do so since the 1964 Barons.
=== College ===
Collegiately, NCAA Division I Cleveland State Vikings have 19 varsity sports, nationally known for their Cleveland State Vikings men's basketball team. NCAA Division III Case Western Reserve Spartans have 17 varsity sports, most known for their Case Western Reserve Spartans football team. The headquarters of the Mid-American Conference (MAC) are in Cleveland. The conference stages both its men's and women's basketball tournaments at Rocket Arena.
=== Annual and special events ===
The Cleveland Marathon has been hosted annually since 1978, and a monument commemorating one of Cleveland's most prominent track and field athletes, Jesse Owens, stands at the city's Fort Huntington Park. The second American Chess Congress, a predecessor to the U.S. Championship, was held in Cleveland in 1871, and won by George Henry Mackenzie. The 1921 and 1957 U.S. Open Chess Championships took place in the city, and were won by Edward Lasker and Bobby Fischer, respectively. The Cleveland Open is held annually. In 2014, Cleveland hosted the ninth official Gay Games ceremony. In July 2024, the city hosted the Pan American Masters Games.
== Parks and recreation ==
Known locally as the "Emerald Necklace", the Olmsted-inspired Cleveland Metroparks encircle Cleveland and Cuyahoga County. The city proper encompasses the Metroparks' Brookside and Lakefront Reservations, as well as significant parts of the Rocky River, Washington, and Euclid Creek Reservations. The Lakefront Reservation, which provides public access to Lake Erie, consists of four parks: Edgewater Park, Whiskey Island–Wendy Park, East 55th Street Marina, and Gordon Park.
Three more parks fall under the jurisdiction of the Euclid Creek Reservation: Euclid Beach, Villa Angela, and Wildwood Marina. Further south, bike and hiking trails in the Brecksville and Bedford Reservations, along with Garfield Park, provide access to trails in the Cuyahoga Valley National Park. Also included in the Metroparks system is the Cleveland Metroparks Zoo, established in 1882. Located in Big Creek Valley, the zoo has one of the largest collections of primates in North America.
In addition to the Metroparks, the Cleveland Public Parks District oversees the city's neighborhood parks, the largest of which is the historic Rockefeller Park. The latter is notable for its late 19th century landmark bridges, the Rockefeller Park Greenhouse, and the Cleveland Cultural Gardens, which celebrate the city's ethnic diversity. In addition, the Greater Cleveland Aquarium, located in the historic FirstEnergy Powerhouse in the Flats, is the only independent, free-standing aquarium in the state of Ohio.
== Government and politics ==
=== Government and courts ===
Cleveland operates on a mayor–council (strong mayor) form of government, in which the mayor is the chief executive and the city council serves as the legislative branch. City council members are elected from 17 wards to four-year terms. From 1924 to 1931, the city briefly experimented with a council–manager government under William R. Hopkins and Daniel E. Morgan before returning to the mayor–council system.
Cleveland is served by Cleveland Municipal Court, the first municipal court in the state. The city also anchors the U.S. District Court for the Northern District of Ohio, based at the Carl B. Stokes U.S. Courthouse and the historic Howard M. Metzenbaum U.S. Courthouse. The Chief Judge for the Northern District is Sara Elizabeth Lioi and the Clerk of Court is Sandy Opacich. The U.S. Attorney is Carol Skutnik and the U.S. Marshal is Peter Elliott.
=== Politics ===
The office of the mayor has been held by Justin Bibb since 2022. Previous mayors include progressive Democrat Tom L. Johnson, World War I-era War Secretary and BakerHostetler founder Newton D. Baker, U.S. Supreme Court Justice Harold Hitz Burton, two-term Ohio Governor and Senator Frank J. Lausche, former U.S. Health, Education, and Welfare Secretary Anthony J. Celebrezze, two-term Ohio Governor and Senator George V. Voinovich, former U.S. Congressman Dennis Kucinich, and Carl B. Stokes, the first African American mayor of a major U.S. city. Frank G. Jackson was the city's longest-serving mayor.
The President of Cleveland City Council is Blaine Griffin, the council Majority Leader is Kerry McCormack, and the Majority Whip is Jasmin Santana. Patricia Britt serves as the Clerk of Council.
Historically, from the Civil War era to the 1940s, Cleveland had been dominated by the Republican Party, with the notable exceptions of the Johnson and Baker mayoral administrations.
Today Cleveland is a major stronghold for the Democratic Party in Ohio. Although local elections are nonpartisan, Democrats still dominate every level of government.
Cleveland has hosted three Republican national conventions, in 1924, 1936, and 2016. Additionally, the city hosted the Radical Republican convention of 1864. Although Cleveland has not hosted a national convention for the Democrats, it has hosted several national election debates, including the second 1980 U.S. presidential debate, the 2004 U.S. vice presidential debate, one 2008 Democratic primary debate, and the first 2020 U.S. presidential debate. Founded in 1912, the City Club of Cleveland provides a platform for national and local debates and discussions. Known as Cleveland's "Citadel of Free Speech", it is one of the oldest continuous independent free speech and debate forums in the country.
== Public safety ==
=== Police and law enforcement ===
Like in other major American cities, crime in Cleveland is concentrated in areas with higher rates of poverty and lower access to jobs. In recent decades, the rate of crime in the city, although higher than the national average, experienced a significant decline, following a nationwide trend in falling crime rates. However, as in other major U.S. cities, crime in Cleveland saw an abrupt rise in 2020–21.
Cleveland's law enforcement agency is the Cleveland Division of Police, established in 1866. The division had roughly 1,100 sworn officers as of 2024, covering five police districts. The district system was introduced in the 1930s by Cleveland Public Safety Director Eliot Ness (of the Untouchables), who later ran for mayor of Cleveland in 1947. The Chief of Police is Dorothy A. Todd. In addition, the Cuyahoga County Sheriff's Office is based in Downtown Cleveland at the Justice Center Complex.
=== Fire department ===
Cleveland is served by the firefighters of the Cleveland Division of Fire, established in 1863. The fire department operates out of 22 active fire stations throughout the city in five battalions. Each Battalion is commanded by a Battalion Chief, who reports to an on-duty Assistant Chief.
The Division of Fire operates a fire apparatus fleet of twenty-two engine companies, eight ladder companies, three tower companies, two task force rescue squad companies, hazardous materials ("haz-mat") unit, and numerous other special, support, and reserve units. The Chief of Department is Anthony Luke.
=== Emergency medical services ===
Cleveland EMS is operated by the city as its own municipal third-service EMS division. Cleveland EMS is the primary provider of Advanced Life Support and ambulance transport within the city of Cleveland, while Cleveland Fire assists by providing fire response medical care. Although a merger between the fire and EMS departments was proposed in the past, the idea was subsequently abandoned.
=== Military ===
Cleveland serves as headquarters to Coast Guard District 9 and is responsible for all U.S. Coast Guard operations on the five Great Lakes, the Saint Lawrence Seaway, and surrounding states accumulating 6,700 miles of shoreline and 1,500 miles of international shoreline with Canada. It reports up through the U.S. Department of Homeland Security. Station Cleveland Harbor, located in North Coast Harbor, has a responsibility covering about 550 square miles of the federally navigable waters of Lake Erie, including the Cuyahoga and Rocky rivers, as well as a number of their tributaries.
== Education ==
=== Primary and secondary ===
Cleveland is served by the Cleveland Metropolitan School District. It is the only K–12 district in Ohio under the direct control of the mayor, who appoints a school board. Approximately of Cleveland's Buckeye–Shaker neighborhood is part of the Shaker Heights City School District. The area, which has been a part of the Shaker school district since the 1920s, permits these Cleveland residents to pay the same school taxes as the Shaker residents, as well as vote in the Shaker school board elections.
There are several private and parochial schools in Cleveland. These include Benedictine High School, Cleveland Central Catholic High School, Eleanor Gerson School, St. Ignatius High School, St. Joseph Academy, Villa Angela-St. Joseph High School, and St. Martin de Porres.
=== Colleges and universities ===
Cleveland is home to a number of colleges and universities. Most prominent among them is Case Western Reserve University (CWRU), a widely recognized research and teaching institution based in University Circle with several major graduate programs.
University Circle also contains the Cleveland Institute of Art and the Cleveland Institute of Music. Downtown Cleveland is home to Cleveland State University, a public research university with eight constituent colleges, and the metropolitan campus of Cuyahoga Community College. Cleveland's suburban universities and colleges include Baldwin Wallace University in Berea, John Carroll University in University Heights, and Ursuline College in Pepper Pike. It holds the Northeast Ohio Broadcast Archives, and the John G. White Special Collection, with the largest chess library in the world and a rare collection of folklore and books on the Middle East and Eurasia. The library's main building was designed by Walker and Weeks and dedicated in 1925, under head librarian Linda Eastman, the first woman to lead a major library system in the U.S. Between 1904 and 1920, 15 libraries built with funds from Andrew Carnegie were opened in the city. Known as the "People's University", the library presently maintains 27 branches. It serves as the headquarters for the CLEVNET library consortium, which includes 47 public library systems in Northeast Ohio.
== Media ==
=== Print ===
Cleveland's primary daily newspaper is The Plain Dealer and its associated online publication, Cleveland.com. Defunct major newspapers include the Cleveland Press and the Cleveland News. Additional publications include Cleveland Magazine, a regional culture magazine published monthly; Crain's Cleveland Business, a weekly business newspaper; and Cleveland Scene, a free alternative weekly paper which absorbed its competitor, the Cleveland Free Times, in 2008. The digital Belt Magazine was founded in Cleveland in 2013. Time magazine was published in Cleveland from 1925 to 1927.
Several ethnic publications are based in Cleveland. These include the Call and Post, a weekly newspaper that primarily serves the city's African American community; the Cleveland Jewish News, a weekly Jewish newspaper; the bi-weekly Russian-language Cleveland Russian Magazine; the Mandarin Erie Chinese Journal; La Gazzetta Italiana in English and Italian; the Ohio Irish American News; and the Spanish language Vocero Latino News.
=== TV ===
The Cleveland-area television market is served by 11 full power stations, including WKYC (NBC), WEWS-TV (ABC), WJW (Fox), WDLI-TV (Bounce), WOIO (CBS), WVPX-TV (Ion), WVIZ (PBS), WUAB (CW/RESN), WRLM (TCT), WBNX-TV (independent), and WQHS-DT (Univision). the market, which includes the Akron and Canton areas, was the 19th-largest in the country, as measured by Nielsen Media Research.
The Mike Douglas Show, a nationally syndicated daytime talk show, began in Cleveland in 1961 on KYW-TV (now WKYC), while The Morning Exchange on WEWS-TV served as the model for Good Morning America. Tim Conway and Ernie Anderson first established themselves in Cleveland while working together at KYW-TV and later WJW-TV (now WJW). Anderson both created and performed as the immensely popular Cleveland horror host Ghoulardi on WJW-TV's Shock Theater, and was later succeeded by the long-running late night duo Big Chuck and Lil' John. Another Anderson protégé – Ron Sweed – would become a popular Cleveland late night movie host in his own right as "The Ghoul".
=== Radio ===
Cleveland is directly served by 29 full power AM and FM radio stations, 21 of which are licensed to the city. Music stations – which are frequently the highest-rated in the market – include WQAL (hot adult contemporary), WDOK (adult contemporary), WKLV-FM (Christian contemporary - K-Love), WAKS (contemporary hits), WHLK (adult hits), WMJI (classic hits), WMMS (active rock/hot talk), WNCX (classic rock), WNWV (alternative rock), WGAR-FM (country), WZAK (urban adult contemporary), WENZ (mainstream urban), WCLV (classical), and WJMO (Spanish/Tropical). WMMS also serves as the FM flagship for the Cleveland Cavaliers and the Cleveland Guardians, while WNCX is an FM flagship for the Cleveland Browns.
News/talk stations include WHK, WTAM, and WERE. During the Golden Age of Radio, WHK was the first radio station to broadcast in Ohio, and one of the first in the country. WTAM is the AM flagship for both the Cleveland Cavaliers and the Cleveland Guardians. Sports stations include WKNR (ESPN), WARF (Fox) and WKRK-FM (Infinity), with WKNR and WKRK-FM serving as co-flagship stations for the Cleveland Browns, and WARF airing the Cleveland Monsters and – though primarily an English language station – Spanish broadcasts of Cleveland Guardians home games. Religious stations include WCCD, WHKW, WCCR, and WCRF.
As the regional NPR affiliate, WKSU serves all of Northeast Ohio (including both the Cleveland and Akron markets). College stations include WBWC (Baldwin Wallace), WCSB (Cleveland State), WJCU (John Carroll), and WRUW-FM (Case Western Reserve). In 1968, Cleveland became the first city in the nation to have a direct rail transit connection linking the city's downtown to its major airport. Like other major cities, the urban density of Cleveland reduces the need for private vehicle ownership. In 2016, 23.7% of Cleveland households lacked a car, while the national average was 8.7%. Cleveland averaged 1.19 cars per household in 2016, compared to a national average of 1.8.
=== Roads ===
Cleveland's road system consists of numbered streets running roughly north–south, and named avenues, which run roughly east–west. The numbered streets are designated "east" or "west", depending on where they lie in relation to Ontario Street, which bisects Public Square. The two downtown avenues which span the Cuyahoga change names on the west side of the river. Superior Avenue becomes Detroit Avenue on the West Side, and Carnegie Avenue becomes Lorain Avenue. The bridges that make these connections are the Hope Memorial (Lorain–Carnegie) Bridge and the Veterans Memorial (Detroit–Superior) Bridge.
=== Freeways ===
Cleveland is served by three two-digit interstate highways – Interstate 71, Interstate 77, and Interstate 90 – and by two three-digit interstates – Interstate 480 and Interstate 490. Running due east–west through the West Side suburbs, I-90 turns northeast at the junction with I-490, and is known as the Cleveland Inner Belt. The Cleveland Memorial Shoreway carries Ohio State Route 2 along its length, and at varying points carries US 6, US 20 and I-90. At the junction with the Shoreway, I-90 makes a 90-degree turn in the area known as Dead Man's Curve, then continues northeast. The Jennings Freeway (State Route 176) connects I-71 just south of I-90 to I-480.
=== Airports ===
Cleveland is a major North American air market, serving 4.93 million people. Cleveland Hopkins is a significant regional air freight hub hosting FedEx Express, UPS Airlines, U.S. Postal Service, and major commercial freight carriers. In addition to Hopkins, Cleveland is served by Burke Lakefront Airport, on the north shore of downtown between Lake Erie and the Shoreway. Burke is primarily a commuter and business airport.
=== Seaport ===
The Port of Cleveland, at the Cuyahoga River's mouth, is a major bulk freight and container terminal on Lake Erie, receiving much of the raw materials used by the region's manufacturing industries. The Port of Cleveland is the only container port on the Great Lakes with bi-weekly container service between Cleveland and the Port of Antwerp in Belgium on a Dutch service called the Cleveland-Europe Express. In addition to freight, the Port of Cleveland welcomes regional and international tourists who pass through the city on Great Lakes cruises.
=== Intercity rail and bus ===
Cleveland has a long history as a major railroad hub in North America. Today, Amtrak provides service to Cleveland, via the Capitol Limited and Lake Shore Limited routes, which stop at Cleveland Lakefront Station. Additionally, Cleveland hosts several inter-modal freight railroad terminals, for Norfolk Southern, CSX and several smaller companies.
National intercity bus service is provided by Greyhound. Akron Metro, Brunswick Transit Alternative, Laketran, Lorain County Transit, and Medina County Transit provide connecting bus service to the Greater Cleveland Regional Transit Authority. Geauga County Transit and Portage Area Regional Transportation Authority (PARTA) also offer connecting bus service in their neighboring areas.
== International relations ==
Cleveland maintains cultural, economic, and educational ties with 28 sister cities around the world. It concluded its first sister city partnership with Lima, Peru, in 1964. In addition, Cleveland hosts the Consulate General of the Republic of Slovenia, which, until Slovene independence in 1991, served as an official consulate for Tito's Yugoslavia. The Cleveland Clinic operates the Cleveland Clinic Abu Dhabi hospital, two outpatient clinics in Toronto, and a hospital campus in London. The Cleveland Council on World Affairs was established in 1923.
Historically, Cleveland industrialist Cyrus S. Eaton, an apprentice of John D. Rockefeller, played a significant role in promoting dialogue between the U.S. and the Soviet Union during the Cold War. In October 1915 at Cleveland's Bohemian National Hall, Czech American and Slovak American representatives signed the Cleveland Agreement, calling for the formation of a joint Czech and Slovak state.
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"the Flats",
"Halle Brothers Co.",
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"Socialist Federal Republic of Yugoslavia",
"gypsy jazz",
"Oliver Hazard Perry",
"Grammy Award for Best Rap Performance by a Duo or Group",
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"television market",
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"List of diplomatic missions of Slovenia",
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"Andrew Carnegie",
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"WJW (TV)",
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"Romanian American",
"subprime mortgage crisis",
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"Slavery in the United States",
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"Cleveland Crunch",
"DiSanto Field",
"Leader Building",
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"Tema",
"art museum",
"Superman (2025 film)",
"The Kid from Cleveland",
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"The Next Iron Chef",
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"urban rail transit",
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"lost film",
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"socialism",
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"precipitation (meteorology)",
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"Off-Off-Broadway",
"Edith Anisfield Wolf",
"2016 Republican National Convention",
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"chess libraries",
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"Alfred Kelley",
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"Franklin D. Roosevelt",
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"The Fate of the Furious",
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"musical theatre",
"Kill the Irishman",
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"amphitheater",
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"vaudeville",
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"Largest cities in the United States by population by decade",
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"Cyrus S. Eaton",
"1995 World Series",
"Beaux-Arts architecture",
"Dominican Republic",
"Brecksville",
"Default (finance)",
"Lent",
"Czechoslovakia",
"Burke Lakefront Airport",
"National Park Service",
"Bone Thugs-n-Harmony",
"Samuel Andrews (chemist)",
"Cleveland Scene",
"Django Reinhardt",
"2001 MLB season",
"Volgograd",
"Buckeye–Woodhill",
"Glenville High School",
"NFL Championship",
"1948 Cleveland Indians season",
"Carl B. Stokes United States Courthouse",
"Travel Centers of America",
"RTA Rapid Transit",
"Greater Cleveland Film Commission",
"Serbian language",
"2016–17 NBA season",
"Jasmin Santana",
"Hyatt",
"George Steinbrenner",
"Hungarian language",
"Pre-Code Hollywood",
"Fox Broadcasting Company",
"James Gunn",
"United States District Court for the Northern District of Ohio",
"Cuyahoga Community College",
"Interstate Highway System",
"silent film",
"NCAA Division III",
"Cleveland Pops Orchestra",
"Shaker Heights, Ohio",
"Asian Americans",
"Cleveland City Hall",
"Cleveland Museum of Natural History",
"Greek-American cuisine",
"Heidenheim an der Brenz",
"WUAB",
"council–manager government",
"Tri-State Christian Television",
"Cleveland Heights, Ohio",
"Novi Sad",
"kielbasa",
"US Chess Championship",
"United States Census Bureau",
"American Basketball League (1961–63)",
"Cleveland-Cliffs",
"Streetcar strikes in the United States",
"Polka Hall of Fame",
"Rail transportation in the United States",
"NFL",
"Greater Cleveland",
"Rouen",
"Harlan Ellison",
"Cleveland Botanical Garden",
"Cleveland Cultural Gardens",
"West Park, Cleveland"
] |
5,954 |
Callisto
|
Callisto most commonly refers to:
Callisto (mythology), a nymph
Callisto (moon), a moon of Jupiter
Callisto may also refer to:
== Art and entertainment ==
Callisto series, a sequence of novels by Lin Carter
Callisto, a novel by Torsten Krol
Callisto (comics), a fictional mutant in X-Men
Callisto (Xena), a character on Xena: Warrior Princess
"Callisto" (Xena: Warrior Princess episode)
Callisto family, a fictional family in the Miles from Tomorrowland TV series
Callisto, a toy in the Mattel Major Matt Mason series
Callisto (band), a band from Turku, Finland
==People with the name==
Callisto Cosulich (1922–2015), Italian film critic, author, journalist and screenwriter
Callisto Pasuwa, Zimbabwean soccer coach
Callisto Piazza (1500–1561), Italian painter
== Other uses ==
Callisto (moth), a genus of moths in the family Gracillariidae
CALLISTO, a reusable test rocket
Callisto Corporation, a software development company
Callisto, a release of version 3.2 of Eclipse
Callisto, an AMD Phenom II processor core
Callisto (organization), a non-profit organization
|
[
"Callisto (mythology)",
"Kallisto (disambiguation)",
"Phenom II",
"Callisto (moon)",
"Callistus (disambiguation)",
"CALLISTO",
"Castillo (disambiguation)",
"Callisto Cosulich",
"Callisto Piazza",
"Callista (disambiguation)",
"Eclipse (software)",
"Callisto (Xena: Warrior Princess episode)",
"Torsten Krol",
"Callisto (organization)",
"Major Matt Mason",
"Miles from Tomorrowland",
"Callisto Corporation",
"Calisto (disambiguation)",
"Callisto (comics)",
"Callisto Pasuwa",
"Callisto (moth)",
"Callisto series",
"Callisto (band)",
"Callisto (Xena)"
] |
5,955 |
Church of England
|
The Church of England (C of E) is the established Christian church in England and the Crown Dependencies. It is the mother church of the Anglican tradition, with foundational doctrines being contained in the Thirty-nine Articles and The Books of Homilies. The Church traces its history to the Christian hierarchy recorded as existing in the Roman province of Britain by the 3rd century and to the 6th-century Gregorian mission to Kent led by Augustine of Canterbury. Its members are called Anglicans.
In 1534, the Church of England renounced the authority of the Papacy under the direction of Henry VIII, beginning the English Reformation. The guiding theologian that shaped Anglican doctrine was the Reformer Thomas Cranmer, who developed the Church of England's liturgical text, the Book of Common Prayer.
In the earlier phase of the English Reformation there were both Catholic and Protestant martyrs. This continued into the later phases, which saw the Penal Laws punish Catholics and nonconforming Protestants. Various factions continued to challenge the leadership and doctrine of the church into the 17th century, which under Charles I veered towards a more Catholic interpretation of the Elizabethan Settlement, especially under Archbishop Laud. Following the victory of the Roundheads in the English Civil War, the Puritan faction dominated and the Book of Common Prayer and episcopacy were abolished. These would be restored under the Stuart Restoration in 1660.
Since the English Reformation, the Church of England has used the English language in the liturgy. As a broad church, the Church of England contains several doctrinal strands: the main traditions are known as Anglo-Catholic, high church, central church, and low church, the last producing a growing evangelical wing that includes Reformed Anglicanism, with a smaller number of Arminian Anglicans. Tensions between theological conservatives and liberals find expression in debates over the ordination of women and same-sex marriage. The British monarch (currently Charles III) is the supreme governor and the archbishop of Canterbury (vacant since 7 January 2025, after the resignation of Justin Welby) is the most senior cleric. The governing structure of the Church is based on dioceses, each presided over by a bishop. Within each diocese are local parishes. The General Synod of the Church of England is the legislative body for the church and comprises bishops, other clergy and laity. Its measures must be approved by the Parliament of the United Kingdom.
==History==
===Middle Ages===
There is evidence for Christianity in Roman Britain as early as the 3rd century. After the fall of the Roman Empire, England was conquered by the Anglo-Saxons, who were pagans, and the Celtic church was confined to Cornwall and Wales. In 597, Pope Gregory I sent missionaries to England to Christianise the Anglo-Saxons. This mission was led by Augustine, who became the first archbishop of Canterbury. The Church of England considers 597 the start of its formal history.
In Northumbria, Celtic missionaries competed with their Roman counterparts. The Celtic and Roman churches disagreed over the date of Easter, baptismal customs, and the style of tonsure worn by monks. King Oswiu of Northumbria summoned the Synod of Whitby in 664. The king decided Northumbria would follow the Roman tradition because Saint Peter and his successors, the bishops of Rome, hold the keys of the kingdom of heaven.
By the late Middle Ages, Catholicism was an essential part of English life and culture. The 9,000 parishes covering all of England were overseen by a hierarchy of deaneries, archdeaconries, dioceses led by bishops, and ultimately the pope who presided over the Catholic Church from Rome. Catholicism taught that the contrite person could cooperate with God towards their salvation by performing good works (see synergism). God's grace was given through the seven sacraments. In the Mass, a priest consecrated bread and wine to become the body and blood of Christ through transubstantiation. The church taught that, in the name of the congregation, the priest offered to God the same sacrifice of Christ on the cross that provided atonement for the sins of humanity. The Mass was also an offering of prayer by which the living could help souls in purgatory. While penance removed the guilt attached to sin, Catholicism taught that a penalty still remained. It was believed that most people would end their lives with these penalties unsatisfied and would have to spend time in purgatory. Time in purgatory could be lessened through indulgences and prayers for the dead, which were made possible by the communion of saints.
===Reformation===
In 1527, Henry VIII was desperate for a male heir and asked Pope Clement VII to annul his marriage to Catherine of Aragon. When the pope refused, Henry used Parliament to assert royal authority over the English church. In 1533, Parliament passed the Act in Restraint of Appeals, barring legal cases from being appealed outside England. This allowed the Archbishop of Canterbury to annul the marriage without reference to Rome. In November 1534, the Act of Supremacy formally abolished papal authority and declared Henry Supreme Head of the Church of England.
Henry's religious beliefs remained aligned to traditional Catholicism throughout his reign, albeit with reformist aspects in the tradition of Erasmus and firm commitment to royal supremacy. In order to secure royal supremacy over the church, however, Henry allied himself with Protestants, who until that time had been treated as heretics. The main doctrine of the Protestant Reformation was justification by faith alone rather than by good works. The logical outcome of this belief is that the Mass, sacraments, charitable acts, prayers to saints, prayers for the dead, pilgrimage, and the veneration of relics do not mediate divine favour. To believe they can would be superstition at best and idolatry at worst.
Between 1536 and 1540, Henry engaged in the dissolution of the monasteries, which controlled much of the richest land. He disbanded religious houses, appropriated their income, disposed of their assets, and provided pensions for the former residents. The properties were sold to pay for the wars. Historian George W. Bernard argues:
In the reign of Edward VI (1547–1553), the Church of England underwent an extensive theological reformation. Justification by faith was made a central teaching. Government-sanctioned iconoclasm led to the destruction of images and relics. Stained glass, shrines, statues, and roods were defaced or destroyed. Church walls were whitewashed and covered with biblical texts condemning idolatry. The most significant reform in Edward's reign was the adoption of an English liturgy to replace the old Latin rites. Written by the Protestant Reformer Archbishop Thomas Cranmer, the 1549 Book of Common Prayer implicitly taught justification by faith, and rejected the Catholic doctrines of transubstantiation and the sacrifice of the Mass. This was followed by a greatly revised 1552 Book of Common Prayer, which propounded a Reformed view of the Lord's Supper (cf. Lord's Supper in Reformed theology). Along with The Book of Common Prayer, The Thirty-nine Articles and The Books of Homilies, assembled through the efforts of the Reformer Thomas Cranmer, became the basis of Anglican doctrine after the English Reformation. Notably, the Act of Settlement 1701, which remains in force today, stipulates that the monarch (who serves as the Supreme Governor of the Church of England) be a Protestant, maintain the Protestant succession, and "join in communion with the Church of England as by law established." The Coronation Oath Act 1688 (reiterated in the Act of Settlement 1701) requires the rising Sovereign to take an oath to maintain "the true Profession of the Gospel and the Protestant Reformed Religion Established by Law" in the United Kingdom. In order to secure his political position, William III of England ended these discussions and the Tudor ideal of encompassing all the people of England in one religious organisation was abandoned. The religious landscape of England assumed its present form, with the Anglican established church occupying the middle ground and Nonconformists continuing their existence outside. One result of the Restoration was the ousting of 2,000 parish ministers who had not been ordained by bishops in the apostolic succession or who had been ordained by ministers in presbyter's orders. Official suspicion and legal restrictions continued well into the 19th century. Roman Catholics, perhaps 5% of the English population (down from 20% in 1600) were grudgingly tolerated, having had little or no official representation after the Pope's excommunication of Queen Elizabeth in 1570, though the Stuarts were sympathetic to them. By the end of 18th century they had dwindled to 1% of the population, mostly amongst upper middle-class gentry, their tenants, and extended families.
===Union with the Church of Ireland===
By the Fifth Article of the Union with Ireland 1800, the Church of England and Church of Ireland were united into "one Protestant Episcopal church, to be called, the United Church of England and Ireland". Although "the continuance and preservation of the said united church ... [was] deemed and taken to be an essential and fundamental part of the union", the Irish Church Act 1869 separated the Irish part of the church again and disestablished it, the Act coming into effect on 1 January 1871.
===Overseas developments===
As the English Empire (after the 1707 union of the Kingdom of England with the Kingdom of Scotland to form the Kingdom of Great Britain, the British Empire) expanded, English (after 1707, British) colonists and colonial administrators took the established church doctrines and practices together with ordained ministry and formed overseas branches of the Church of England.
The Diocese of Nova Scotia was created on 11 August 1787 by Letters Patent of George III which "erected the Province of Nova Scotia into a bishop's see" and these also named Charles Inglis as first bishop of the see. The diocese was the first Church of England see created outside England and Wales (i.e. the first colonial diocese). At this point, the see covered present-day New Brunswick, Newfoundland, Nova Scotia, Prince Edward Island and Quebec. From 1825 to 1839, it included the nine parishes of Bermuda, subsequently transferred to the Diocese of Newfoundland.
As they developed, beginning with the United States of America, or became sovereign or independent states, many of their churches became separate organisationally, but remained linked to the Church of England through the Anglican Communion. In the provinces that made up Canada, the church operated as the "Church of England in Canada" until 1955 when it became the Anglican Church of Canada.
In Bermuda, the oldest remaining British overseas possession, the first Church of England services were performed by the Reverend Richard Buck, one of the survivors of the 1609 wreck of the Sea Venture which initiated Bermuda's permanent settlement. The nine parishes of the Church of England in Bermuda, each with its own church and glebe land, rarely had more than a pair of ordained ministers to share between them until the 19th century. From 1825 to 1839, Bermuda's parishes were attached to the See of Nova Scotia. Bermuda was then grouped into the new Diocese of Newfoundland and Bermuda from 1839. In 1879, the Synod of the Church of England in Bermuda was formed. At the same time, a Diocese of Bermuda became separate from the Diocese of Newfoundland, but both continued to be grouped under the Bishop of Newfoundland and Bermuda until 1919, when Newfoundland and Bermuda each received its own bishop. The Church of England in Bermuda was renamed in 1978 as the Anglican Church of Bermuda, which is an extra-provincial diocese, with both metropolitan and primatial authority coming directly from the Archbishop of Canterbury. Among its parish churches is St Peter's Church in the UNESCO World Heritage Site of St George's Town, which is the oldest Anglican church outside of the British Isles, and the oldest Protestant church in the New World.
The Church of India, Burma and Ceylon was established in Colonial India, with its first diocese being erected in 1813, the Diocese of Calcutta. Indian bishops were present at the first Lambeth Conference.
The first Anglican missionaries arrived in Nigeria in 1842 and the first Anglican Nigerian was consecrated a bishop in 1864. However, the arrival of a rival group of Anglican missionaries in 1887 led to infighting that slowed the Church's growth. In this large African colony, by 1900 there were only 35,000 Anglicans, about 0.2% of the population. However, by the late 20th century the Church of Nigeria was the fastest growing of all Anglican churches, reaching about 18 percent of the local population by 2000.
====Continued decline in attendance and church response====
Bishop Sarah Mullally has insisted that declining numbers at services should not necessarily be a cause of despair for churches, because people may still encounter God without attending a service in a church; for example hearing the Christian message through social media sites or in a café run as a community project. The Church of England estimates that 35 - 50 million people visit its churches as tourists annually. Additionally, 9.7 million people visit at least one of its churches every year and 1 million students are educated at Church of England schools (which number 4,700). In 2019, an estimated 10 million people visited a cathedral and an additional "1.3 million people visited Westminster Abbey, where 99% of visitors paid / donated for entry". In 2022, the church reported than an estimated 5.7 million people visited a cathedral and 6.8 million visited Westminster Abbey. Nevertheless, the archbishops of Canterbury and York warned in January 2015 that the Church of England would no longer be able to carry on in its current form unless the downward spiral in membership were somehow to be reversed, as typical Sunday attendance had halved to 800,000 in the previous 40 years:
Between 1969 and 2010, almost 1,800 church buildings, roughly 11% of the stock, were closed (so-called "redundant churches"); the majority (70%) in the first half of the period; only 514 being closed between 1990 and 2010. Some active use was being made of about half of the closed churches. By 2019 the rate of closure had steadied at around 20 to 25 per year (0.2%); some being replaced by new places of worship. Additionally, in 2018 the church announced a £27 million growth programme to create 100 new churches.
====Low salaries====
In 2015 the Church of England admitted that it was embarrassed to be paying staff under the living wage. The Church of England had previously campaigned for all employers to pay this minimum amount. The archbishop of Canterbury acknowledged it was not the only area where the church "fell short of its standards".
=== Impact of COVID-19 pandemic ===
The COVID-19 pandemic had a sizeable effect on church attendance, with attendance in 2020 and 2021 well below that of 2019. By 2022, the first full year without substantial restrictions related to the pandemic, numbers were still notably down on pre-pandemic participation. According to the 2022 release of "Statistics for Mission" by the church, the median size of each church's worshipping community (those who attend in person or online at least once a month) stood at 37 people, with average weekly attendance having declined from 34 to 25; while Easter and Christmas services had seen falls from 51 to 38 and 80 to 56 individuals respectively.
Examples of wider declines across the whole church include: The canon law of the Church of England identifies the Christian scriptures as the source of its doctrine. In addition, doctrine is also derived from the teachings of the Church Fathers and ecumenical councils (as well as the ecumenical creeds) in so far as these agree with scripture. This doctrine is expressed in the Thirty-Nine Articles of Religion, the Book of Common Prayer, and the Ordinal containing the rites for the ordination of deacons, priests, and the consecration of bishops. Richard Hooker's appeal to scripture as the primary source of Christian doctrine, informed by church tradition, and reason, has been influential in hermeneutics.
The Church of England's doctrinal character today is largely the result of the Elizabethan Settlement. The historical development of Anglicanism saw itself as navigating a via media between two forms of Protestantism—Lutheranism and Reformed Christianity—though leaning closer to the latter than the former. The Church of England affirms the protestant reformation principle that scripture contains all things necessary to salvation and is the final arbiter in doctrinal matters. The Thirty-nine Articles are the church's only official confessional statement. The Church of England did retain three orders of ministry and the apostolic succession of bishops, as with the Scandinavian Lutheran Churches (such as the Church of Sweden) and Roman Catholicism. Its identity has thus been described as Reformed and Catholic. This tolerance has allowed Anglicans who emphasise the catholic tradition and others who emphasise the reformed tradition to coexist. The three schools of thought (or parties) in the Church of England are sometimes called high church (or Anglo-Catholic), low church (or evangelical Anglican) and broad church (or liberal). The high church party places importance on the Church of England's continuity with the pre-Reformation Catholic Church, adherence to ancient liturgical usages and the sacerdotal nature of the priesthood. As their name suggests, Anglo-Catholics maintain many traditional catholic practices and liturgical forms. The Catholic tradition, strengthened and reshaped from the 1830s by the Oxford movement, has stressed the importance of the visible Church and its sacraments and the belief that the ministry of bishops, priests and deacons is a sign and instrument of the Church of England's Catholic and apostolic identity. The low church party is more Protestant in both ceremony and theology. It has emphasized the significance of the Protestant aspects of the Church of England's identity, stressing the importance of the authority of Scripture, preaching, justification by faith and personal conversion. The liberal broad church tradition has emphasized the importance of the use of reason in theological exploration. It has stressed the need to develop Christian belief and practice in order to respond creatively to wider advances in human knowledge and understanding and the importance of social and political action in forwarding God's kingdom.
===Worship and liturgy===
In 1604, James I ordered an English language translation of the Bible known as the King James Version, which was published in 1611 and authorised for use in parishes, although it was not an "official" version per se. The Church of England's official book of liturgy as established in English Law is the 1662 version of the Book of Common Prayer (BCP). In the year 2000, the General Synod approved a modern liturgical book, Common Worship, which can be used as an alternative to the BCP. Like its predecessor, the 1980 Alternative Service Book, it differs from the Book of Common Prayer in providing a range of alternative services, mostly in modern language, although it does include some BCP-based forms as well, for example Order Two for Holy Communion. (This is a revision of the BCP service, altering some words and allowing the insertion of some other liturgical texts such as the Agnus Dei before communion.) The Order One rite follows the pattern of more modern liturgical scholarship.
The liturgies are organised according to the traditional liturgical year and the calendar of saints. The sacraments of baptism and the eucharist are generally thought necessary to salvation. Infant baptism is practised. At a later age, individuals baptised as infants receive confirmation by a bishop, at which time they reaffirm the baptismal promises made by their parents or sponsors. The eucharist, consecrated by a thanksgiving prayer including Christ's Words of Institution, is believed to be "a memorial of Christ's once-for-all redemptive acts in which Christ is objectively present and effectually received in faith".
The use of hymns and music in the Church of England has changed dramatically over the centuries. Traditional Choral evensong is a staple of most cathedrals. The style of psalm chanting harks back to the Church of England's pre-reformation roots. During the 18th century, clergy such as Charles Wesley introduced their own styles of worship with poetic hymns.
In the latter half of the 20th century, the influence of the Charismatic Movement significantly altered the worship traditions of numerous Church of England parishes, primarily affecting those of evangelical persuasion. These churches now adopt a contemporary worship form of service, with minimal liturgical or ritual elements, and incorporating contemporary worship music.
Just as the Church of England has a large conservative or "traditionalist" wing, it also has many liberal members and clergy. Approximately one third of clergy "doubt or disbelieve in the physical resurrection". Others, such as Giles Fraser, a contributor to The Guardian, have argued for an allegorical interpretation of the virgin birth of Jesus. The Independent reported in 2014 that, according to a YouGov survey of Church of England clergy, "as many as 16 per cent are unclear about God and two per cent think it is no more than a human construct." Moreover, many congregations are seeker-friendly environments. For example, one report from the Church Mission Society suggested that the church open up "a pagan church where Christianity [is] very much in the centre" to reach out to spiritual people.
The Church of England is launching a project on "gendered language" in Spring 2023 in efforts to "study the ways in which God is referred to and addressed in liturgy and worship".
=== Women's ministry ===
Women were appointed as deaconesses from 1861, but they could not function fully as deacons and were not considered ordained clergy. Women have historically been able to serve as lay readers. During the First World War, some women were appointed as lay readers, known as "bishop's messengers", who also led missions and ran churches in the absence of men. After the war, no women were appointed as lay readers until 1969.
Legislation authorising the ordination of women as deacons was passed in 1986 and they were first ordained in 1987. The ordination of women as priests was approved by the General Synod in 1992 and began in 1994. In 2010, for the first time in the history of the Church of England, more women than men were ordained as priests (290 women and 273 men), but in the next two years, ordinations of men again exceeded those of women.
In July 2005, the synod voted to "set in train" the process of allowing the consecration of women as bishops. In February 2006, the synod voted overwhelmingly for the "further exploration" of possible arrangements for parishes that did not want to be directly under the authority of a bishop who is a woman. On 7 July 2008, the synod voted to approve the ordination of women as bishops and rejected moves for alternative episcopal oversight for those who do not accept the ministry of bishops who are women. Actual ordinations of women to the episcopate required further legislation, which was narrowly rejected in a General Synod vote in November 2012. On 20 November 2013, the General Synod voted overwhelmingly in support of a plan to allow the ordination of women as bishops, with 378 in favour, 8 against and 25 abstentions.
On 14 July 2014, the General Synod approved the ordination of women as bishops. The House of Bishops recorded 37 votes in favour, two against with one abstention. The House of Clergy had 162 in favour, 25 against and four abstentions. The House of Laity voted 152 for, 45 against with five abstentions. This legislation had to be approved by the Ecclesiastical Committee of the Parliament before it could be finally implemented at the November 2014 synod. In December 2014, Libby Lane was announced as the first woman to become a bishop in the Church of England. She was consecrated as a bishop in January 2015. In July 2015, Rachel Treweek was the first woman to become a diocesan bishop in the Church of England when she became the Bishop of Gloucester. She and Sarah Mullally, Bishop of Crediton, were the first women to be ordained as bishops at Canterbury Cathedral.
In May 2018, the Diocese of London consecrated Dame Sarah Mullally as the first woman to serve as the Bishop of London. Bishop Sarah Mullally occupies the third most senior position in the Church of England. Mullally has described herself as a feminist and will ordain both men and women to the priesthood. She is also considered by some to be a theological liberal. On women's reproductive rights, Mullally describes herself as pro-choice while also being personally pro-life. On marriage, she supports the current stance of the Church of England that marriage is between a man and a woman, but also said that: "It is a time for us to reflect on our tradition and scripture, and together say how we can offer a response that is about it being inclusive love."
=== Same-sex unions and LGBT clergy ===
The Church of England has been discussing same-sex marriages and LGBT clergy. The church holds that marriage is a union of one man with one woman. The church does not allow clergy to perform same-sex marriages, but in February 2023 approved of blessings for same-sex couples following a civil marriage or civil partnership. The church teaches "Same-sex relationships often embody genuine mutuality and fidelity." In January 2023, the Bishops approved "prayers of thanksgiving, dedication and for God's blessing for same-sex couples." The commended prayers of blessing for same-sex couples, known as "Prayers of Love and Faith," may be used during ordinary church services, and in November 2023 General Synod voted to authorise "standalone" blessings for same-sex couples on a trial basis, while permanent authorisation will require additional steps. The church also officially supports celibate civil partnerships; "We believe that Civil Partnerships still have a place, including for some Christian LGBTI couples who see them as a way of gaining legal recognition of their relationship."
Civil partnerships for clergy have been allowed since 2005, so long as they remain sexually abstinent, and the church extends pensions to clergy in same-sex civil partnerships. In a missive to clergy, the church communicated that "there was a need for committed same-sex couples to be given recognition and 'compassionate attention' from the Church, including special prayers." "There is no prohibition on prayers being said in church or there being a 'service'" after a civil union. After same-sex marriage was legalised, the church sought continued availability of civil unions, saying "The Church of England recognises that same-sex relationships often embody fidelity and mutuality. Civil partnerships enable these Christian virtues to be recognised socially and legally in a proper framework." In 2024, the General Synod voted in support of eventually permitting clergy to enter into civil same-sex marriages.
In 2014, the bishops released guidelines that permit "more informal kind of prayer" for couples. In the guidelines, "gay couples who get married will be able to ask for special prayers in the Church of England after their wedding, the bishops have agreed." The church had decided in 2013 that gay clergy in civil partnerships so long as they remain sexually abstinent could become bishops. "The House [of Bishops] has confirmed that clergy in civil partnerships, and living in accordance with the teaching of the church on human sexuality, can be considered as candidates for the episcopate."
In 2017, the House of Clergy voted against the motion to "take note" of the bishops' report defining marriage as between a man and a woman. Due to passage in all three houses being required, the motion was rejected. After General Synod rejected the motion, the archbishops of Canterbury and York called for "radical new Christian inclusion" that is "based on good, healthy, flourishing relationships, and in a proper 21st century understanding of being human and of being sexual." The church officially opposes "conversion therapy", a practice which attempts to change a gay or lesbian person's sexual orientation, calling it unethical and supports the banning of "conversion therapy" in the UK. The Diocese of Hereford approved a motion calling for the church "to create a set of formal services and prayers to bless those who have had a same-sex marriage or civil partnership." In 2022, "The House [of Bishops] also agreed to the formation of a Pastoral Consultative Group to support and advise dioceses on pastoral responses to circumstances that arise concerning LGBTI+ clergy, ordinands, lay leaders and the lay people in their care."
Regarding transgender issues, the 2017 General Synod voted in favour of a motion saying that transgender people should be "welcomed and affirmed in their parish church". The motion also asked the bishops "to look into special services for transgender people." The bishops initially said "the House notes that the Affirmation of Baptismal Faith, found in Common Worship, is an ideal liturgical rite which trans people can use to mark this moment of personal renewal." The Bishops also authorised services of celebration to mark a gender transition that will be included in formal liturgy. Transgender people may marry in the Church of England after legally making a transition. "Since the Gender Recognition Act 2004, trans people legally confirmed in their gender identity under its provisions are able to marry someone of the opposite sex in their parish church." The church further decided that same-gender couples may remain married when one spouse experiences gender transition provided that the spouses identified as opposite genders at the time of the marriage. Since 2000, the church has allowed priests to undergo gender transition and remain in office. The church has ordained openly transgender clergy since 2005. The Church of England ordained the church's first openly non-binary priest in 2022. In 2023, the Church of England appointed Rachel Mann as the church's first openly trans Archdeacon.
In January 2023, a meeting of the Bishops of the Church of England rejected demands for clergy to conduct same-sex marriages. However, proposals would be put to the General Synod that clergy should be able to hold church blessings for same-sex civil marriages, albeit on a voluntary basis for individual clergy. This comes as the Church continued to be split on same-sex marriages.
In February 2023, ten archbishops of the Global South Fellowship of Anglican Churches released a statement stating that they had broken communion and no longer recognised Justin Welby as "the first among equals" or "primus inter pares" in the Anglican Communion in response to the General Synod's decision to approve the blessing of same-sex couples following a civil marriage or partnership, leading to questions as to the status of the Church of England as the mother church of the international Anglican Communion.
In November 2023, the General Synod narrowly voted to allow church blessings for same-sex couples on a trial basis. In December 2023, the first blessings of same-sex couples began in the Church of England. In 2024, the General Synod voted to support moving forward with "stand-alone" services of blessing for same-sex couples after a civil marriage or civil partnership.
===Bioethics issues===
The Church of England is generally opposed to abortion but believes "there can be strictly limited conditions under which abortion may be morally preferable to any available alternative". The church also opposes euthanasia. Its official stance is that "While acknowledging the complexity of the issues involved in assisted dying/suicide and voluntary euthanasia, the Church of England is opposed to any change in the law or in medical practice that would make assisted dying/suicide or voluntary euthanasia permissible in law or acceptable in practice." It also states that "Equally, the Church shares the desire to alleviate physical and psychological suffering, but believes that assisted dying/suicide and voluntary euthanasia are not acceptable means of achieving these laudable goals." In 2014, George Carey, a former archbishop of Canterbury, announced that he had changed his stance on euthanasia and now advocated legalising "assisted dying". On embryonic stem-cell research, the church has announced "cautious acceptance to the proposal to produce cytoplasmic hybrid embryos for research".
In the 19th century, English law required the burial of people who had died by suicide to occur only between the hours of 9 p.m. and midnight and without religious rites. The Church of England permitted the use of alternative burial services for people who had died by suicide. In 2017, the Church of England changed its rules to permit the full, standard Christian burial service regardless of whether a person had died by suicide.
==Social work==
===Church Urban Fund===
The Church of England set up the Church Urban Fund in the 1980s to tackle poverty and deprivation. It sees poverty as trapping individuals and communities with some people in urgent need, leading to dependency, homelessness, hunger, isolation, low income, mental health problems, social exclusion and violence. They feel that poverty reduces confidence and life expectancy and that people born in poor conditions have difficulty escaping their disadvantaged circumstances.
====Child poverty====
In parts of Liverpool, Manchester and Newcastle two-thirds of babies are born to poverty and have poorer life chances, also a life expectancy 15 years lower than babies born in the best-off fortunate communities.
===Action on hunger===
Many prominent people in the Church of England have spoken out against poverty and welfare cuts in the United Kingdom. Twenty-seven bishops are among 43 Christian leaders who signed a letter which urged David Cameron to make sure people have enough to eat.
Thousands of UK citizens use food banks. The church's campaign to end hunger considers this "truly shocking" and called for a national day of fasting on 4 April 2014. This number has remained consistent since 2001 and was cited again in 2013 and 2014. In 2010, the government estimated that there were 24,841,000 baptised members of the Church of England. In 2018, the British Social Attitudes Survey found that 14% of Britons, or about 10 million people, self-identified as members of the Church of England; this was called an "unrelenting decline" by a spokesperson for the survey. According to David Voas, conducting research in 2001 at the University of Sheffield, the number of baptised members was expected to decline at a rate of 1 million every five years; their number was reported to have fallen to 20 million in 2022.
Due to the Church of England's status as the established church, in general, anyone may be married, have their children baptised or their funeral held in their local parish church, regardless of whether they are baptised or regular churchgoers.
Between 1890 and 2001, churchgoing in the United Kingdom declined steadily. In the years 1968 to 1999, Anglican Sunday church attendances almost halved, from 3.5 percent of the population to 1.9 per cent. By 2014, Sunday church attendances had declined further to 1.4 per cent of the population. One study published in 2008 suggested that if current trends continued, Sunday attendances could fall to 350,000 in 2030 and 87,800 in 2050. The Church of England releases an annual publication, Statistics for Mission, detailing numerous criteria relating to participation with the church. Below is a snapshot of several key metrics from every five years since 2001 (2022 has been used in place of 2021 to avoid the impact of Covid restrictions). Since 2021, Sunday church attendance has increased, although not to pre-pandemic levels.
== Personnel ==
In 2020, there were almost 20,000 active clergy serving in the Church of England, including 7,200 retired clergy who continued to serve. In that year, 580 were ordained (330 in stipendiary posts and 250 in self-supporting parochial posts) and a further 580 ordinands began their training. In that year, 33% of those in ordained ministry were female, an increase from the 26% reported in 2016.}}
The British monarch has the constitutional title of Supreme Governor of the Church of England. The canon law of the Church of England states, "We acknowledge that the King's most excellent Majesty, acting according to the laws of the realm, is the highest power under God in this kingdom, and has supreme authority over all persons in all causes, as well ecclesiastical as civil." In practice this power is often exercised through Parliament and on the advice of the Prime Minister.
The Church of Ireland and the Church in Wales separated from the Church of England in 1869 and 1920 respectively and are autonomous churches in the Anglican Communion; Scotland's national church, the Church of Scotland, is Presbyterian, but the Scottish Episcopal Church is part of the Anglican Communion.
In addition to England, the jurisdiction of the Church of England extends to the Isle of Man, the Channel Islands and a few parishes in Flintshire, Monmouthshire and Powys in Wales which voted to remain with the Church of England rather than joining the Church in Wales. Expatriate congregations on the continent of Europe have become the Diocese of Gibraltar in Europe.
The church is structured as follows (from the lowest level upwards):
Parish is the most local level, often consisting of one church building (a parish church) and community, although many parishes are joining forces in a variety of ways for financial reasons. The parish is looked after by a parish priest who for historical or legal reasons may be called by one of the following offices: vicar, rector, priest in charge, team rector, team vicar. The first, second, fourth and fifth of these may also be known as the 'incumbent'. The running of the parish is the joint responsibility of the incumbent and the parochial church council (PCC), which consists of the parish clergy and elected representatives from the congregation. The Diocese of Gibraltar in Europe is not formally divided into parishes.
There are a number of local churches that do not have a parish. In urban areas there are a number of proprietary chapels (mostly built in the 19th century to cope with urbanisation and growth in population). Also in more recent years there are increasingly church plants and fresh expressions of church, whereby new congregations are planted in locations such as schools or pubs to spread the Gospel of Christ in non-traditional ways.
Deanery, e.g., Lewisham or Runnymede. This is the area for which a Rural Dean (or area dean) is responsible. It consists of a number of parishes in a particular district. The rural dean is usually the incumbent of one of the constituent parishes. The parishes each elect lay (non-ordained) representatives to the deanery synod. Deanery synod members each have a vote in the election of representatives to the diocesan synod.
Archdeaconry, e.g., the seven in the Diocese of Gibraltar in Europe. This is the area under the jurisdiction of an archdeacon. It consists of a number of deaneries.
Diocese, e.g., Diocese of Durham, Diocese of Guildford, Diocese of St Albans. This is the area under the jurisdiction of a diocesan bishop, e.g., the bishops of Durham, Guildford and St Albans, and will have a cathedral. There may be one or more suffragan bishops within the diocese who assist the diocesan bishop in his ministry, e.g., in Guildford diocese, the Bishop of Dorking. In some very large dioceses a legal measure has been enacted to create "episcopal areas", where the diocesan bishop runs one such area himself and appoints "area bishops" to run the other areas as mini-dioceses, legally delegating many of his powers to the area bishops. Dioceses with episcopal areas include London, Chelmsford, Oxford, Chichester, Southwark, and Lichfield. The bishops work with an elected body of lay and ordained representatives, known as the Diocesan Synod, to run the diocese. A diocese is subdivided into a number of archdeaconries.
Province, i.e., Canterbury or York. This is the area under the jurisdiction of an archbishop, i.e. the Archbishops of Canterbury and York. Decision-making within the province is the responsibility of the General Synod (see also above). A province is subdivided into dioceses.
Primacy, i.e., Church of England. The Archbishop of York's title of "Primate of England" is essentially honorific and carries with it no powers beyond those inherent in being Archbishop and Metropolitan of the Province of York. The Archbishop of Canterbury, on the other hand, the "Primate of All England", has powers that extend over the whole of England, and also Wales—for example, through his Faculty Office he may grant a "special marriage licence" permitting the parties to marry otherwise than in a church: for example, in a school, college or university chapel; or anywhere, if one of the parties to the intended marriage is in danger of imminent death.{{efn|The powers to grant special marriage licences, to appoint notaries public, and to grant Lambeth degrees, are derived from the so called "legatine powers" which were held by the Pope's Legate to England prior to the Reformation, and were transferred to the Archbishop of Canterbury by the Ecclesiastical Licences Act 1533. Thus they are not, strictly speaking, derived from the status of the Archbishop of Canterbury as "Primate of All England". For this reason, they extend also to Wales.
The second most senior bishop is the Archbishop of York, who is the metropolitan of the northern province of England, the Province of York. For historical reasons (relating to the time of York's control by the Danes) he is referred to as the Primate of England. Stephen Cottrell became Archbishop of York in 2020. The Bishop of London, the Bishop of Durham and the Bishop of Winchester are ranked in the next three positions, insofar as the holders of those sees automatically become members of the House of Lords.
===Diocesan bishops===
The process of appointing diocesan bishops is complex, due to historical reasons balancing hierarchy against democracy, and is handled by the Crown Nominations Committee which submits names to the Prime Minister (acting on behalf of the Crown) for consideration.
===Representative bodies===
The Church of England has a legislative body, General Synod. This can create two types of legislation, measures and canons. Measures have to be approved but cannot be amended by the British Parliament before receiving royal assent and becoming part of the law of England. Although it is the established church in England only, its measures must be approved by both Houses of Parliament including the non-English members. Canons require Royal Licence and Royal Assent, but form the law of the church, rather than the law of the land.
Another assembly is the Convocation of the English Clergy, which is older than the General Synod and its predecessor the Church Assembly. By the Synodical Government Measure 1969 almost all of the Convocations' functions were transferred to the General Synod. Additionally, there are Diocesan Synods and deanery synods, which are the governing bodies of the divisions of the Church.
===House of Lords===
Of the 42 diocesan archbishops and bishops in the Church of England, 26 are permitted to sit in the House of Lords. The Archbishops of Canterbury and York automatically have seats, as do the bishops of London, Durham and Winchester. The remaining 21 seats are filled in order of seniority by date of consecration. It may take a diocesan bishop a number of years to reach the House of Lords, at which point he or she becomes a Lord Spiritual. The Bishop of Sodor and Man and the Bishop of Gibraltar in Europe are not eligible to sit in the House of Lords as their dioceses lie outside the United Kingdom.
===Crown Dependencies===
Although they are not part of England or the United Kingdom, the Church of England is also the established church in the Crown Dependencies of the Isle of Man, the Bailiwick of Jersey and the Bailiwick of Guernsey. The Isle of Man has its own diocese of Sodor and Man, and the Bishop of Sodor and Man is an ex officio member of the legislative council of the Tynwald on the island. Historically the Channel Islands have been under the authority of the Bishop of Winchester, but this authority has temporarily been delegated to the Bishop of Dover since 2015. In Jersey the Dean of Jersey is a non-voting member of the States of Jersey. In Guernsey the Church of England is the established church, although the Dean of Guernsey is not a member of the States of Guernsey.
==Sex abuse==
The 2020 report from the Independent Inquiry into Child Sexual Abuse found several cases of sexual abuse within the Church of England, and concluded that the Church did not protect children from sexual abuse, and allowed abusers to hide. The Church spent more effort defending alleged abusers than supporting victims or protecting children and young people. Bishop Peter Ball was convicted in October 2015 on several charges of indecent assault against young adult men.
In June 2023, the Archbishops' Council dismissed the three board members of the Independent Safeguarding Board, which was set up in 2021 "to hold the Church to account, publicly if needs be, for any failings which are preventing good safeguarding from happening". A statement issued by the Archbishops of Canterbury and York referred to there being "no prospect of resolving the disagreement and that it is getting in the way of the vital work of serving victims and survivors". Jasvinder Sanghera and Steve Reeves, the two independent members of the board, had complained about interference with their work by the Church. The Bishop of Birkenhead, Julie Conalty, speaking to BBC Radio 4 in connection with the dismissals, said: "I think culturally we are resistant as a church to accountability, to criticism. And therefore I don't entirely trust the church, even though I'm a key part of it and a leader within it, because I see the way the wind blows is always in a particular direction."
On 20 July 2023, it was announced that the archbishops of Canterbury and York had appointed Alexis Jay to provide proposals for an independent system of safeguarding for the Church of England.
In February 2025, the General Synod voted not to make safeguarding the responsibiity of an independent body, to the dismay of many.
In February 2025, the Church of England announced it would take forward the clergy disciplinary measure process against 10 clergy, following the Makin Review of the serial abuser John Smyth.
==Funding and finances==
Although an established church, the Church of England does not receive any direct government support, except some funding for building work. Donations comprise its largest source of income, and it also relies heavily on the income from its various historic endowments. In 2005, the Church of England had estimated total outgoings of around £900 million.
The Church of England manages an investment portfolio which is worth more than £8 billion.
==Online church directories==
The Church of England runs A Church Near You, an online directory of churches. A user-edited resource, it currently lists more than 16,000 churches and has 20,000 editors in 42 dioceses. The directory enables parishes to maintain accurate location, contact and event information, which is shared with other websites and mobile apps. The site allows the public to find their local worshipping community, and offers churches free resources, such as hymns, videos and social media graphics.
The Church Heritage Record includes information on over 16,000 church buildings, including architectural history, archaeology, art history, and the surrounding natural environment. It can be searched by elements including church name, diocese, date of construction, footprint size, listing grade, and church type. The types of church identified include:
Major Parish Church: "some of the most special, significant and well-loved places of worship in England", having "most of all" of the characteristics of being large (over 1,000msq), listed (generally grade I or II*), having "exceptional significance and/or issues necessitating a conservation management plan" and having a local role beyond that of an average parish church. there are 312 such churches in the database. These churches are eligible to join the Major Churches Network.
Festival Church: a church not used for weekly services but used for occasional services and other events. These churches are eligible to join the Association of Festival Churches. there are 19 such churches in the database.
CCT Church: a church under the care of the Churches Conservation Trust. there are 345 such churches in the database.
Friendless Church: there are 24 such churches in the database; the Friends of Friendless Churches cares for 60 churches across England and Wales.
|
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5,956 |
Circe
|
Circe (; ) is an enchantress and a minor goddess in ancient Greek mythology and religion. In most accounts, Circe is described as the daughter of the sun god Helios and the Oceanid nymph Perse. Circe was renowned for her vast knowledge of potions and herbs. Through the use of these and a magic wand or staff, she would transform her enemies, or those who offended her, into animals.
The best known of her legends is told in Homer's Odyssey when Odysseus visits her island of Aeaea on the way back from the Trojan War and she changes most of his crew into swine. He manages to persuade her to return them to human shape, lives with her for a year and has sons by her, including Latinus and Telegonus. Her ability to change others into animals is further highlighted by the story of Picus, an Italian king whom she turns into a woodpecker for resisting her advances. Another story tells of her falling in love with the sea-god Glaucus, who prefers the nymph Scylla to her. In revenge, Circe poisoned the water where her rival bathed and turned her into a dreadful monster.
Depictions, even in Classical times, diverged from the detail in Homer's narrative, which was later to be reinterpreted morally as a cautionary story against drunkenness. Early philosophical questions were also raised about whether the change from being a human endowed with reason to being an unreasoning beast might not be preferable after all, and the resulting debate was to have a powerful impact during the Renaissance. Circe was also taken as the archetype of the predatory female. In the eyes of those from a later age, this behaviour made her notorious both as a magician and as a type of sexually free woman. She has been frequently depicted as such in all the arts from the Renaissance down to modern times.
Western paintings established a visual iconography for the figure, but also went for inspiration to other stories concerning Circe that appear in Ovid's Metamorphoses. The episodes of Scylla and Picus added the vice of violent jealousy to her bad qualities and made her a figure of fear as well as of desire.
== Classical literature ==
=== Family and attributes ===
By most accounts, she was the daughter of the sun god Helios and Perse, one of the three thousand Oceanid nymphs. In Orphic Argonautica, her mother is called Asterope instead. Her brothers were Aeëtes, keeper of the Golden Fleece and father of Medea, and Perses. Her sister was Pasiphaë, the wife of King Minos and mother of the Minotaur. Other accounts make her and her niece Medea the daughters of Hecate, the goddess of witchcraft by Aeëtes, usually said to be her brother instead. She was often confused with Calypso, due to her shifts in behavior and personality, and the association that both of them had with Odysseus.
According to Greek legend, Circe lived on the island of Aeaea. Although Homer is vague when it comes to the island's whereabouts, the early 3rd BC author Apollonius of Rhodes's epic poem Argonautica locates Aeaea somewhere south of Aethalia (Elba), within view of the Tyrrhenian shore (that is, the western coast of Italy). In the same poem, Circe's brother Aeëtes describes how Circe was transferred to Aeaea: "I noted it once after taking a ride in my father Helios' chariot, when he was taking my sister Circe to the western land and we came to the coast of the Tyrrhenian mainland, where she dwells to this day, very far from the Colchian land." A scholiast on Apollonius Rhodius claims that Apollonius is following Hesiod's tradition in making Circe arrive in Aeaea on Helios' chariot, while Valerius Flaccus writes that Circe was borne away by winged dragons. Roman poets associated her with the most ancient traditions of Latium, and made her home to be on the promontory of Circeo.
Homer describes Circe as "a dreadful goddess with lovely hair and human speech". Apollonius writes that she (just like every other descendant of Helios) had flashing golden eyes that shot out rays of light, with the author of Argonautica Orphica noting that she had hair like fiery rays. Ovid's The Cure for Love implies that Circe might have been taught the knowledge of herbs and potions from her mother Perse, who seems to have had similar skills.
=== Pre-Odyssey ===
In the Argonautica, Apollonius relates that Circe purified the Argonauts for the murder of Medea's brother Absyrtus, possibly reflecting an early tradition. In this poem, the Argonauts find Circe bathing in salt water; the animals that surround her are not former lovers transformed but primeval "beasts, not resembling the beasts of the wild, nor yet like men in body, but with a medley of limbs." Circe invites Jason, Medea and their crew into her mansion; uttering no words, they show her the still bloody sword they used to cut Absyrtus down, and Circe immediately realizes they have visited her to be purified of murder. She purifies them by slitting the throat of a suckling pig and letting the blood drip on them. Afterwards, Medea tells Circe their tale in great detail, albeit omitting the part of Absyrtus' murder; nevertheless Circe is not fooled, and greatly disapproves of their actions. However, out of pity for the girl, and on account of their kinship, she promises not to be an obstacle on their way, and orders Jason and Medea to leave her island immediately.
The sea-god Glaucus was in love with a beautiful maiden, Scylla, but she spurned his affections no matter how he tried to win her heart. Glaucus went to Circe, and asked her for a magic potion to make Scylla fall in love with him too. But Circe was smitten by Glaucus herself, and fell in love with him. Glaucus did not love her back, and turned down her offer of marriage. Enraged, Circe used her knowledge of herbs and plants to take her revenge; she found the spot where Scylla usually took her bath, and poisoned the water. When Scylla went down to it to bathe, dogs sprang from her thighs and she was transformed into the familiar monster from the Odyssey. In another, similar story, Picus was a Latian king whom Circe turned into a woodpecker. He was the son of Saturn, and a king of Latium. He fell in love and married a nymph, Canens, to whom he was utterly devoted. One day as he was hunting boars, he came upon Circe, who was gathering herbs in the woods. Circe fell immediately in love with him; but Picus, just like Glaucus before him, spurned her and declared that he would remain forever faithful to Canens. Circe, furious, turned Picus into a woodpecker. His wife Canens eventually wasted away in her mourning.
During the war between the gods and the giants, one of the giants, Picolous, fled the battle against the gods and came to Aeaea, Circe's island. He attempted to chase Circe away, only to be killed by Helios, Circe's ally and father. From the blood of the slain giant, a herb came into existence; moly, named thus from the battle (malos) and with a white-coloured flower, either for the white Sun who had killed Picolous or the terrified Circe who turned white; the very plant, which mortals are unable to pluck from the ground, that Hermes would later give to Odysseus in order to defeat Circe.
=== Homer's Odyssey ===
In Homer's Odyssey, an 8th-century BC sequel to his Trojan War epic Iliad, Circe is initially described as a beautiful goddess living in a palace isolated in the midst of a dense wood on her island of Aeaea. Around her home prowl strangely docile lions and wolves. She lures any who land on the island to her home with her lovely singing while weaving on an enormous loom, but later drugs them so that they change shape. One of her Homeric epithets is polypharmakos, "knowing many drugs or charms".
Circe invites the hero Odysseus' crew to a feast of familiar food, a pottage of cheese and meal, sweetened with honey and laced with wine, but also mixed with one of her magical potions that turns them into swine. Only Eurylochus, who suspects treachery, does not go in. He escapes to warn Odysseus and the others who have remained with the ship. Before Odysseus reaches Circe's palace, Hermes, the messenger god sent by the goddess of wisdom Athena, intercepts him and reveals how he might defeat Circe in order to free his crew from their enchantment. Hermes provides Odysseus with moly to protect him from Circe's magic. He also tells Odysseus that he must then draw his sword and act as if he were going to attack her. From there, as Hermes foretold, Circe would ask Odysseus to bed, but Hermes advises caution, for the treacherous goddess could still "unman" him unless he has her swear by the names of the gods that she will not take any further action against him. Following this advice, Odysseus is able to free his men.
After they have all remained on the island for a year, Circe advises Odysseus that he must first visit the Underworld, something a mortal has never yet done, in order to gain knowledge about how to appease the gods, return home safely and recover his kingdom. Circe also advises him on how this might be achieved and furnishes him with the protections he will need and the means to communicate with the dead. On his return, she further advises him about two possible routes home, warning him, however, that both carry great danger.
=== Post-Odyssey ===
Towards the end of Hesiod's Theogony (c. 700 BC), it is stated that Circe bore Odysseus three sons: Agrius (otherwise unknown); Latinus; and Telegonus, who ruled over the Tyrsenoi, that is the Etruscans. The Telegony, an epic now lost, relates the later history of the last of these. Circe eventually informed her son who his absent father was and, when he set out to find Odysseus, gave him a poisoned spear. When Telegonus arrived in Ithaca, Odysseus was away in Thesprotia, fighting the Brygi. Telegonus began to ravage the island; Odysseus came to defend his land. With the weapon Circe gave him, Telegonus killed his father unknowingly. Telegonus then brought back his father's corpse to Aeaea, together with Penelope and Odysseus' son by her, Telemachus. After burying Odysseus, Circe made the other three immortal.
Circe married Telemachus, and Telegonus married Penelope by the advice of Athena. According to an alternative version depicted in Lycophron's 3rd-century BC poem Alexandra (and John Tzetzes' scholia on it), Circe used magical herbs to bring Odysseus back to life after he had been killed by Telegonus. Odysseus then gave Telemachus to Circe's daughter Cassiphone in marriage. Sometime later, Telemachus had a quarrel with his mother-in-law and killed her; Cassiphone then killed Telemachus to avenge her mother's death. On hearing of this, Odysseus died of grief.
Dionysius of Halicarnassus (1.72.5) cites Xenagoras, the 2nd-century BC historian, as claiming that Odysseus and Circe had three different sons: Rhomos, Anteias, and Ardeias, who respectively founded three cities called by their names: Rome, Antium, and Ardea. In the later 5th-century CE epic Dionysiaca, its author Nonnus mentions Phaunus, Circe's son by the sea god Poseidon.
=== Other works ===
Three ancient plays about Circe have been lost: the work of the tragedian Aeschylus and of the 4th-century BC comic dramatists Ephippus of Athens and Anaxilas. The first told the story of Odysseus' encounter with Circe. Vase paintings from the period suggest that Odysseus' half-transformed animal-men formed the chorus in place of the usual Satyrs. Fragments of Anaxilas also mention the transformation and one of the characters complains of the impossibility of scratching his face now that he is a pig.
The theme of Circe turning men into a variety of animals was elaborated by later writers. In his episodic work The Sorrows of Love (first century BC), Parthenius of Nicaea interpolated another episode into the time that Odysseus was staying with Circe. Pestered by the amorous attentions of King Calchus the Daunian, the sorceress invited him to a drugged dinner that turned him into a pig and then shut him up in her sties. He was only released when his army came searching for him on the condition that he would never set foot on her island again.
Among Latin treatments, Virgil's Aeneid relates how Aeneas skirts the Italian island where Circe dwells and hears the cries of her many male victims, who now number more than the pigs of earlier accounts: The roars of lions that refuse the chain, / The grunts of bristled boars, and groans of bears, / And herds of howling wolves that stun the sailors' ears. In Ovid's 1st-century poem Metamorphoses, the fourth episode covers Circe's encounter with Ulysses (the Roman name of Odysseus), whereas book 14 covers the stories of Picus and Glaucus.
Plutarch took up the theme in a lively dialogue that was later to have several imitators. Contained in his 1st-century Moralia is the Gryllus episode in which Circe allows Odysseus to interview a fellow Greek turned into a pig. After his interlocutor informs Odysseus that his present existence is preferable to the human, they engage in a philosophical dialogue in which every human value is questioned and beasts are proved to be of superior wisdom and virtue.
== Ancient cult ==
Strabo writes that a tomb-shrine of Circe was attended in one of the Pharmacussae islands, off the coast of Attica, typical for hero-worship. Circe was also venerated in Mount Circeo, in the Italian peninsula, which took its name after her according to ancient legend. Strabo says that Circe had a shrine in the small town, and that the people there kept a bowl they claimed belonged to Odysseus. The promontory is occupied by ruins of a platform attributed with great probability to a temple of Venus or Circe.
== Later literature ==
Giovanni Boccaccio provided a digest of what was known of Circe during the Middle Ages in his De mulieribus claris (Famous Women, 1361–1362). While following the tradition that she lived in Italy, he comments wryly that there are now many more temptresses like her to lead men astray.
There is a very different interpretation of the encounter with Circe in John Gower's long didactic poem Confessio Amantis (1380). Ulysses is depicted as deeper in sorcery and readier of tongue than Circe and through this means he leaves her pregnant with Telegonus. Most of the account deals with the son's later quest for and accidental killing of his father, drawing the moral that only evil can come of the use of sorcery.
The story of Ulysses and Circe was retold as an episode in Georg Rollenhagen's German verse epic, Froschmeuseler (The Frogs and Mice, Magdeburg, 1595). In this 600-page expansion of the pseudo-Homeric Batrachomyomachia, it is related at the court of the mice and takes up sections 5–8 of the first part.
In Lope de Vega's miscellany La Circe – con otras rimas y prosas (1624), the story of her encounter with Ulysses appears as a verse epic in three cantos. This takes its beginning from Homer's account, but it is then embroidered; in particular, Circe's love for Ulysses remains unrequited.
As "Circe's Palace", Nathaniel Hawthorne retold the Homeric account as the third section in his collection of stories from Greek mythology, Tanglewood Tales (1853). The transformed Picus continually appears in this, trying to warn Ulysses, and then Eurylochus, of the danger to be found in the palace, and is rewarded at the end by being given back his human shape. In most accounts Ulysses only demands this for his own men.
In her survey of the Transformations of Circe, Judith Yarnall comments of this figure, who started out as a comparatively minor goddess of unclear origin, that "What we know for certain – what Western literature attests to – is her remarkable staying power…These different versions of Circe's myth can be seen as mirrors, sometimes clouded and sometimes clear, of the fantasies and assumptions of the cultures that produced them." After appearing as just one of the characters that Odysseus encounters on his wandering, "Circe herself, in the twists and turns of her story through the centuries, has gone through far more metamorphoses than those she inflicted on Odysseus's companions."
===Reasoning beasts===
One of the most enduring literary themes connected with the figure of Circe was her ability to change men into animals. There was much speculation concerning how this could be, whether the human consciousness changed at the same time, and even whether it was a change for the better. The Gryllus dialogue was taken up by another Italian writer, Giovan Battista Gelli, in his La Circe (1549). This is a series of ten philosophical and moral dialogues between Ulysses and the humans transformed into various animals, ranging from an oyster to an elephant, in which Circe sometimes joins. Most argue against changing back; only the last animal, a philosopher in its former existence, wants to. The work was translated into English soon after in 1557 by Henry Iden. Later the English poet Edmund Spenser also made reference to Plutarch's dialogue in the section of his Faerie Queene (1590) based on the Circe episode which appears at the end of Book II. Sir Guyon changes back the victims of Acrasia's erotic frenzy in the Bower of Bliss, most of whom are abashed at their fall from chivalric grace, But one above the rest in speciall, / That had an hog beene late, hight Grille by name, / Repined greatly, and did him miscall, / That had from hoggish forme him brought to naturall.
Two other Italians wrote rather different works that centre on the animal within the human. One was Niccolò Machiavelli in his unfinished long poem, L'asino d'oro (The Golden Ass, 1516). The author meets a beautiful herdswoman surrounded by Circe's herd of beasts. After spending a night of love with him, she explains the characteristics of the animals in her charge: the lions are the brave, the bears are the violent, the wolves are those forever dissatisfied, and so on (Canto 6). In Canto 7 he is introduced to those who experience frustration: a cat that has allowed its prey to escape; an agitated dragon; a fox constantly on the look-out for traps; a dog that bays the moon; Aesop's lion in love that allowed himself to be deprived of his teeth and claws. There are also emblematic satirical portraits of various Florentine personalities. In the eighth and last canto he has a conversation with a pig that, like the Gryllus of Plutarch, does not want to be changed back and condemns human greed, cruelty and conceit.
The other Italian author was the esoteric philosopher Giordano Bruno, who wrote in Latin. His Cantus Circaeus (The Incantation of Circe) was the fourth work on memory and the association of ideas by him to be published in 1582. It contains a series of poetic dialogues, in the first of which, after a long series of incantations to the seven planets of the Hermetic tradition, most humans appear changed into different creatures in the scrying bowl. The sorceress Circe is then asked by her handmaiden Moeris about the type of behaviour with which each is associated. According to Circe, for instance, fireflies are the learned, wise, and illustrious amidst idiots, asses, and obscure men (Question 32). In later sections different characters discuss the use of images in the imagination in order to facilitate use of the art of memory, which is the real aim of the work.
French writers were to take their lead from Gelli in the following century. Antoine Jacob wrote a one-act social comedy in rhyme, Les Bestes raisonnables (The Reasoning Beasts, 1661) which allowed him to satirise contemporary manners. On the isle of Circe, Ulysses encounters an ass that was once a doctor, a lion that had been a valet, a female doe and a horse, all of whom denounce the decadence of the times. The ass sees human asses everywhere, Asses in the town square, asses in the suburbs, / Asses in the provinces, asses proud at court, / Asses browsing in the meadows, military asses trooping, / Asses tripping it at balls, asses in the theatre stalls. To drive the point home, in the end it is only the horse, formerly a courtesan, who wants to return to her former state.
The same theme occupies La Fontaine's late fable, "The Companions of Ulysses" (XII.1, 1690), which also echoes Plutarch and Gelli. Once transformed, every animal (which includes a lion, a bear, a wolf and a mole) protests that their lot is better and refuses to be restored to human shape. Charles Dennis shifted this fable to stand at the head of his translation of La Fontaine, Select Fables (1754), but provides his own conclusion that When Mortals from the path of Honour stray, / And the strong passions over reason sway, / What are they then but Brutes? / 'Tis vice alone that constitutes / Th'enchanting wand and magic bowl, The exterior form of Man they wear, / But are in fact both Wolf and Bear, / The transformation's in the Soul.
Louis Fuzelier and Marc-Antoine Legrand titled their comic opera of 1718 Les animaux raisonnables. It had more or less the same scenario transposed into another medium and set to music by Jacques Aubert. Circe, wishing to be rid of the company of Ulysses, agrees to change back his companions, but only the dolphin is willing. The others, who were formerly a corrupt judge (now a wolf), a financier (a pig), an abused wife (a hen), a deceived husband (a bull) and a flibbertigibbet (a linnet), find their present existence more agreeable.
The Venetian Gasparo Gozzi was another Italian who returned to Gelli for inspiration in the 14 prose Dialoghi dell'isola di Circe (Dialogues from Circe's Island) published as journalistic pieces between 1760 and 1764. In this moral work, the aim of Ulysses in talking to the beasts is to learn more of the human condition. It includes figures from fable (The fox and the crow, XIII) and from myth to illustrate its vision of society at variance. Far from needing the intervention of Circe, the victims find their natural condition as soon as they set foot on the island. The philosopher here is not Gelli's elephant but the bat that retreats from human contact into the darkness, like Bruno's fireflies (VI). The only one who wishes to change in Gozzi's work is the bear, a satirist who had dared to criticize Circe and had been changed as a punishment (IX).
There were two more satirical dramas in later centuries. One modelled on the Gryllus episode in Plutarch occurs as a chapter of Thomas Love Peacock's late novel, Gryll Grange (1861), under the title "Aristophanes in London". Half Greek comedy, half Elizabethan masque, it is acted at the Grange by the novel's characters as a Christmas entertainment. In it Spiritualist mediums raise Circe and Gryllus and try to convince the latter of the superiority of modern times, which he rejects as intellectually and materially regressive. An Italian work drawing on the transformation theme was the comedy by Ettore Romagnoli, La figlia del Sole (The Daughter of the Sun, 1919). Hercules arrives on the island of Circe with his servant Cercopo and has to be rescued by the latter when he too is changed into a pig. But, since the naturally innocent other animals had become corrupted by imitating human vices, the others who had been changed were refused when they begged to be rescued.
Also in England, Austin Dobson engaged more seriously with Homer's account of the transformation of Odysseus' companions when, though Head, face and members bristle into swine, / Still cursed with sense, their mind remains alone. Dobson's "The Prayer of the Swine to Circe" (1640) depicts the horror of being imprisoned in an animal body in this way with the human consciousness unchanged. There appears to be no relief, for only in the final line is it revealed that Odysseus has arrived to free them. But in Matthew Arnold's dramatic poem "The Strayed Reveller" (1849), in which Circe is one of the characters, the power of her potion is differently interpreted. The inner tendencies unlocked by it are not the choice between animal nature and reason but between two types of impersonality, between divine clarity and the poet's participatory and tragic vision of life. In the poem, Circe discovers a youth laid asleep in the portico of her temple by a draught of her ivy-wreathed bowl. On awaking from possession by the poetic frenzy it has induced, he craves for it to be continued.
===Sexual politics===
With the Renaissance there began to be a reinterpretation of what it was that changed the men, if it was not simply magic. For Socrates, in Classical times, it had been gluttony overcoming their self-control. But for the influential emblematist Andrea Alciato, it was unchastity. In the second edition of his Emblemata (1546), therefore, Circe became the type of the prostitute. His Emblem 76 is titled Cavendum a meretricibus; its accompanying Latin verses mention Picus, Scylla and the companions of Ulysses, and concludes that "Circe with her famous name indicates a whore and any who loves such a one loses his reason". His English imitator Geoffrey Whitney used a variation of Alciato's illustration in his own Choice of Emblemes (1586) but gave it the new title of Homines voluptatibus transformantur, men are transformed by their passions. This explains her appearance in the Nighttown section named after her in James Joyce's novel Ulysses. Written in the form of a stage script, it makes of Circe the brothel madam, Bella Cohen. Bloom, the book's protagonist, fantasizes that she turns into a cruel man-tamer named Mr Bello who makes him get down on all fours and rides him like a horse.
By the 19th century, Circe was ceasing to be a mythical figure. Poets treated her either as an individual or at least as the type of a certain kind of woman. The French poet Albert Glatigny addresses "Circé" in his (1857) and makes of her a voluptuous opium dream, the magnet of masochistic fantasies. Louis-Nicolas Ménard's sonnet in (1876) describes her as enchanting all with her virginal look, but appearance belies the accursed reality. Poets in English were not far behind in this lurid portrayal. Lord de Tabley's "Circe" (1895) is a thing of decadent perversity likened to a tulip, A flaunting bloom, naked and undivine... / With freckled cheeks and splotch'd side serpentine, / A gipsy among flowers.
That central image is echoed by the blood-striped flower of T.S.Eliot's student poem "Circe's Palace" (1909) in the Harvard Advocate. Circe herself does not appear, her character is suggested by what is in the grounds and the beasts in the forest beyond: panthers, pythons, and peacocks that look at us with the eyes of men whom we knew long ago. Rather than a temptress, she has become an emasculatory threat.
Several female poets make Circe stand up for herself, using the soliloquy form to voice the woman's position. The 19th-century English poet Augusta Webster, much of whose writing explored the female condition, has a dramatic monologue in blank verse titled "Circe" in her volume Portraits (1870). There the sorceress anticipates her meeting with Ulysses and his men and insists that she does not turn men into pigs—she merely takes away the disguise that makes them seem human. But any draught, pure water, natural wine, / out of my cup, revealed them to themselves / and to each other. Change? there was no change; / only disguise gone from them unawares. The mythological character of the speaker contributes at a safe remove to the Victorian discourse on women's sexuality by expressing female desire and criticizing the subordinate role given to women in heterosexual politics.
Two American poets also explored feminine psychology in poems ostensibly about the enchantress. Leigh Gordon Giltner's "Circe" was included in her collection The Path of Dreams (1900), the first stanza of which relates the usual story of men turned into swine by her spell. But then a second stanza presents a sensuous portrait of an unnamed woman, very much in the French vein; once more, it concludes, "A Circe's spells transform men into swine". This is no passive victim of male projections but a woman conscious of her sexual power. So too is H.D.'s "Circe", from her collection Hymen (1921). In her soliloquy she reviews the conquests with which she has grown bored, then mourns the one instance when she failed. In not naming Ulysses himself, Doolittle universalises an emotion with which all women might identify. At the end of the century, British poet Carol Ann Duffy wrote a monologue entitled Circe which pictures the goddess addressing an audience of "nereids and nymphs". In this outspoken episode in the war between the sexes, Circe describes the various ways in which all parts of a pig could and should be cooked.
Another indication of the progression in interpreting the Circe figure is given by two poems a century apart, both of which engage with paintings of her. The first is the sonnet that Dante Gabriel Rossetti wrote in response to Edward Burne-Jones' "The Wine of Circe" in his volume Poems (1870). It gives a faithful depiction of the painting's Pre-Raphaelite mannerism but its description of Circe's potion as "distilled of death and shame" also accords with the contemporary (male) identification of Circe with perversity. This is further underlined by his statement (in a letter) that the black panthers there are "images of ruined passion" and by his anticipation at the end of the poem of passion's tide-strown shore / Where the disheveled seaweed hates the sea. The Australian A. D. Hope's "Circe – after the painting by Dosso Dossi", on the other hand, frankly admits humanity's animal inheritance as natural and something in which even Circe shares. In the poem, he links the fading rationality and speech of her lovers to her own animal cries in the act of love.
There remain some poems that bear her name that have more to do with their writers' private preoccupations than with reinterpreting her myth. The link with it in Margaret Atwood's "Circe/Mud Poems", first published in You Are Happy (1974), is more a matter of allusion and is nowhere overtly stated beyond the title. It is a reflection on contemporary gender politics that scarcely needs the disguises of Augusta Webster's. With two other poems by male writers it is much the same: Louis Macneice's, for example, whose "Circe" appeared in his first volume, Poems (London, 1935); or Robert Lowell's, whose "Ulysses and Circe" appeared in his last, Day by Day (New York, 1977). Both poets have appropriated the myth to make a personal statement about their broken relationships.
===Parallels and sequels===
Several Renaissance epics of the 16th century include lascivious sorceresses based on the Circe figure. These generally live in an isolated spot devoted to pleasure, to which lovers are lured and later changed into beasts. They include the following:
Alcina in the Orlando Furioso (Mad Roland, 1516, 1532) of Ludovico Ariosto, set at the time of Charlemagne. Among its many sub-plots is the episode in which the Saracen champion Ruggiero is taken captive by the sorceress and has to be freed from her magic island.
The lovers of Filidia in Il Tancredi (1632) by Ascanio Grandi (1567–1647) have been changed into monsters and are liberated by the virtuous Tancred.
Armida in Torquato Tasso's La Gerusalemme liberata (Jerusalem Delivered, 1566–1575, published 1580) is a Saracen sorceress sent by the infernal senate to sow discord among the Crusaders camped before Jerusalem, where she succeeds in changing a party of them into animals. Planning to assassinate the hero, Rinaldo, she falls in love with him instead and creates an enchanted garden where she holds him a lovesick prisoner who has forgotten his former identity.
Acrasia in Edmund Spenser's Faerie Queene, mentioned above, is a seductress of knights and holds them enchanted in her Bower of Bliss.
Later scholarship has identified elements from the character of both Circe and especially her fellow enchantress Medea as contributing to the development of the mediaeval legend of Morgan le Fay. In addition, it has been argued that the fairy Titania in William Shakespeare's A Midsummer Night's Dream (1600) is an inversion of Circe. Titania (daughter of the Titans) was a title by which the sorceress was known in Classical times. In this case the tables are turned on the character, who is queen of the fairies. She is made to love an ass after, rather than before, he is transformed into his true animal likeness.
It has further been suggested that John Milton's Mask Presented at Ludlow Castle (1634) is a sequel to Tempe Restored, a masque in which Circe had figured two years earlier, and that the situation presented there is a reversal of the Greek myth. At the start of the masque, the character Comus is described as the son of Circe by Bacchus, god of wine, and the equal of his mother in enchantment. He too changes travelers into beastly forms that "roll with pleasure in a sensual sty". Having waylaid the heroine and immobilized her on an enchanted chair, he stands over her, wand in hand, and presses on her a magical cup (representing sexual pleasure and intemperance), which she repeatedly refuses, arguing for the virtuousness of temperance and chastity. The picture presented is a mirror image of the Classical story. In place of the witch who easily seduces the men she meets, a male enchanter is resisted by female virtue.
In the 20th century, the Circe episode was to be re-evaluated in two poetic sequels to the Odyssey. In the first of these, Giovanni Pascoli's (The Last Voyage, 1906), the aging hero sets out to rediscover the emotions of his youth by retracing his journey from Troy, only to discover that the island of Eea is deserted. What in his dream of love he had taken for the roaring of lions and Circe's song was now no more than the sound of the sea-wind in autumnal oaks (Cantos 16–17).
This melancholy dispelling of illusion is echoed in The Odyssey: A Modern Sequel (1938) by Nikos Kazantzakis. The fresh voyage in search of new meaning to life recorded there grows out of the hero's initial rejection of his past experiences in the first two sections. The Circe episode is viewed by him as a narrow escape from death of the spirit: With twisted hands and thighs we rolled on burning sands, / a hanging mess of hissing vipers glued in sun!... / Farewell the brilliant voyage, ended! Prow and soul / moored in the muddy port of the contented beast! / O prodigal, much-traveled soul, is this your country? His escape from this mire of sensuality comes one day when the sight of some fishermen, a mother and her baby enjoying the simple comforts of food and drink, recalls him to life, its duties and delights. Where the attempt by Pascoli's hero to recapture the past ended in failure, Kazantzakis' Odysseus, already realising the emptiness of his experiences, journeys into what he hopes will be a fuller future.
==Visual representations==
===Ancient art===
Scenes from the Odyssey are common on Greek pottery, the Circe episode among them. The two most common representations have Circe surrounded by the transformed sailors and Odysseus threatening the sorceress with his sword. In the case of the former, the animals are not always boars but also include, for instance, the ram, dog and lion on the 6th-century BC Boston kylix. Often the transformation is only partial, involving the head and perhaps a sprouting tail, while the rest of the body is human. In describing an otherwise obscure 5th-century Greek bronze in the Walters Art Museum that takes the form of a man on all fours with the foreparts of a pig, the commentator asks in what other way could an artist depict someone bewitched other than as a man with an animal head. In these scenes Circe is shown almost invariably stirring the potion with her wand, although the incident as described in Homer has her use the wand only to bewitch the sailors after they have refreshed themselves. One exception is the Berlin amphora on which the seated Circe holds the wand towards a half transformed man.
In the second scene, Odysseus threatens the sorceress with a drawn sword, as Homer describes it. However, he is sometimes depicted carrying spears as well, as in the Athens lekythos, while Homer reports that it was a bow he had slung over his shoulder. In this episode Circe is generally shown in flight, and on the Erlangen lekythos can clearly be seen dropping the bowl and wand behind her. Two curiously primitive wine bowls incorporate the Homeric detail of Circe's handloom, at which the men approaching her palace could hear her singing sweetly as she worked. In the 5th-century skyphos from Boeotia an apparently crippled Odysseus leans on a crutch while a woman with African features holds out a disproportionately large bowl. In the other, a pot-bellied hero brandishes a sword while Circe stirs her potion. Both these may depict the scene as represented in one or other of the comic satyr plays which deal with their encounter. Little remains of these now beyond a few lines by Aeschylus, Ephippus of Athens and Anaxilas. Other vase paintings from the period suggest that Odysseus' half-transformed animal-men formed the chorus in place of the usual satyrs. The reason that it should be a subject of such plays is that wine drinking was often central to their plot. Later writers were to follow Socrates in interpreting the episode as illustrating the dangers of drunkenness.
Other artefacts depicting the story include the chest of Cypselus described in the travelogue by Pausanias. Among its many carvings "there is a grotto and in it a woman sleeping with a man upon a couch. I was of opinion that they were Odysseus and Circe, basing my view upon the number of the handmaidens in front of the grotto and upon what they are doing. For the women are four, and they are engaged on the tasks which Homer mentions in his poetry". The passage in question describes how one of them "threw linen covers over the chairs and spread fine purple fabrics on top. Another drew silver tables up to the chairs, and laid out golden dishes, while a third mixed sweet honeyed wine in a silver bowl, and served it in golden cups. The fourth fetched water and lit a roaring fire beneath a huge cauldron". This suggests a work of considerable detail, while the Etruscan coffin preserved in Orvieto's archaeological museum has only four figures. At the centre Odysseus threatens Circe with drawn sword while an animal headed figure stands on either side, one of them laying his hand familiarly on the hero's shoulder. A bronze mirror relief in the Fitzwilliam Museum is also Etruscan and is inscribed with the names of the characters. There a pig is depicted at Circe's feet, while Odysseus and Elpenor approach her, swords drawn.
===Portraits in character===
During the 18th century painters began to portray individual actors in scenes from named plays. There was also a tradition of private performances, with a variety of illustrated works to help with stage properties and costumes. Among these was Thomas Jefferys' A Collection of the Dresses of Different Nations, Antient and Modern (1757–1772) which included a copperplate engraving of a crowned Circe in loose dress, holding a goblet aloft in her right hand and a long wand in her left. Evidence of such performances during the following decades is provided by several portraits in character, of which one of the earliest was the pastel by Daniel Gardner (1750–1805) of "Miss Elliot as Circe". The artist had been a pupil of both George Romney and Joshua Reynolds, who themselves were soon to follow his example. On the 1778 engraving based on Gardner's portrait appear the lines from Milton's Comus: The daughter of the Sun, whose charmed cup / Whoever tasted, lost his upright shape / And downward fell into a grovelling swine, in compliment to the charm of this marriageable daughter of a country house. As in the Jefferys' plate, she wears a silver coronet over tumbled dark hair, with a wand in the right hand and a goblet in the left. In hindsight the frank eyes that look directly at the viewer and the rosebud mouth are too innocent for the role Miss Elliot is playing.
The subjects of later paintings impersonating Circe have a history of sexual experience behind them, starting with "Mary Spencer in the character of Circe" by William Caddick, which was exhibited at the Royal Academy in 1780. The subject here was the mistress of the painter George Stubbs. A portrait of "Mrs Nesbitt as Circe" by Reynolds followed in 1781. Though this lady's past was ambiguous, she had connections with those in power and was used by the Government as a secret agent. In the painting she is seated sideways, wearing a white, loose-fitting dress, with a wand in her right hand and a gilded goblet near her left. A monkey is crouching above her in the branches of a tree and a panther fraternizes with the kitten on her knee. While the painting undoubtedly alludes to her reputation, it also places itself within the tradition of dressing up in character.
Soon afterwards, the notorious Emma Hamilton was to raise this to an art form, partly by the aid of George Romney's many paintings of her impersonations. Romney's preliminary study of Emma's head and shoulders, at present in the Tate Gallery, with its piled hair, expressive eyes and mouth, is reminiscent of Samuel Gardener's portrait of Miss Elliot. In the full-length "Lady Hamilton as Circe" at Waddesdon Manor, she is placed in a wooded landscape with wolves snarling to her left, although the tiger originally there has now been painted out. Her left arm is raised to cast a spell while the wand points downward in her right. After Emma moved to Naples and joined Lord Hamilton, she developed what she called her "Attitudes" into a more public entertainment. Specially designed, loose-fitting tunics were paired with large shawls or veils as she posed in such a way as to evoke figures from Classical mythology. These developed from mere poses, with the audience guessing the names of the classical characters and scenes that she portrayed, into small, wordless charades.
The tradition of dressing up in character continued into the following centuries. One of the photographic series by Julia Margaret Cameron, a pupil of the painter George Frederic Watts, was of mythical characters, for whom she used the children of friends and servants as models. Young Kate Keown sat for the head of "Circe" in about 1865 and is pictured wearing a grape and vineleaf headdress to suggest the character's use of wine to bring a change in personality. The society portrait photographer Yevonde Middleton, also known as Madame Yevonde, was to use a 1935 aristocratic charity ball as the foundation for her own series of mythological portraits in colour. Its participants were invited to her studio afterwards to pose in their costumes. There Baroness Dacre is pictured as Circe with a leafy headdress about golden ringlets and clasping a large Baroque porcelain goblet.
A decade earlier, the illustrator Charles Edmund Brock extended into the 20th century what is almost a pastiche of the 18th-century conversation piece in his "Circe and the Sirens" (1925). In this the Honourable Edith Chaplin (1878–1959), Marchioness of Londonderry, and her three youngest daughters are pictured in a garden setting grouped about a large pet goat. Three women painters also produced portraits using the convention of the sitter in character. The earliest was Beatrice Offor (1864–1920), whose sitter's part in her 1911 painting of Circe is suggested by the vine-leaf crown in her long dark hair, the snake-twined goblet she carries and the snake bracelet on her left arm. Mary Cecil Allen was of Australian origin but was living in the United States at the time "Miss Audrey Stevenson as Circe" was painted (1930). Though only a head and shoulders sketch, its colouring and execution suggest the sitter's lively personality. Rosemary Valodon (born 1947), from the same country, painted a series of Australian personalities in her goddess series. "Margarita Georgiadis as Circe" (1991) is a triptych, the central panel of which portrays an updated, naked femme fatale reclining in tropical vegetation next to a pig's head.
One painting at least depicts an actress playing the part of Circe. This is Franz von Stuck's striking portrait of Tilla Durieux as Circe (1913). She played this part in a Viennese revival of Calderon's play in 1912 and there is a publicity still of her by Isidor Hirsch in which she is draped across a sofa and wearing an elaborate crown. Her enticing expression and the turn of her head there is almost exactly that of Van Stuck's enchantress as she holds out the poisoned bowl. It suggests the use of certain posed publicity photos in creating the same iconic effect as had paintings in the past. A nearly contemporary example was the 1907 photo of Mme Geneviève Vix as Circe in the light opera by Lucien Hillenacher at the Opéra-Comique in Paris. The posing of the actress and the cropping of the image so as to highlight her luxurious costume demonstrates its ambition to create an effect that goes beyond the merely theatrical. A later example is the still of Silvana Mangano in her part as Circe in the 1954 film Ulysses, which is as cunningly posed for effect.
==Musical treatments==
===Cantata and song===
Beside the verse dramas, with their lyrical interludes, on which many operas were based, there were poetic texts which were set as secular cantatas. One of the earliest was Alessandro Stradella's La Circe, in a setting for three voices that bordered on the operatic. It was first performed at Frascati in 1667 to honour Cardinal Leopoldo de Medici and contained references to its surroundings. In the opening recitative, Circe explains that it was her son Telegonus who founded Frascati. The other characters with whom she enters into dialogue are the south wind (Zeffiro) and the local river Algido. In the following century, Antonio Vivaldi's cantata (In the shadow of doubt, RV 678) is set for a single voice and depicts Circe addressing Ulysses. The countertenor part is accompanied by flute, harpsichord, cello, and theorbo and features two recitatives and two arias. The piece is famous for the dialogue created between flute and voice, conjuring the moment of flirtation before the two become lovers.
The most successful treatment of the Ulysses episode in French was Jean-Baptiste Rousseau's poem Circé (1703), that was specifically written to be a cantata. The different verse forms employed allow the piece to be divided by the musicians that set it in order to express a variety of emotions. The poem opens with the abandoned Circe sitting on a high mountain and mourning the departure of Ulysses. The sorceress then calls on the infernal gods and makes a terrible sacrifice: A myriad vapours obscure the light, / The stars of the night interrupt their course, / Astonished rivers retreat to their source / And even Death's god trembles in the dark. But though the earth is shaken to its core, Love is not to be commanded in this way and the wintery fields come back to life.
The earliest setting was by Jean-Baptiste Morin in 1706 and was popular for most of the rest of the century. One of its final moralising minuets, (Love won't be forced) was often performed independently and the score reprinted in many song collections. The flautist Michel Blavet arranged the music for this and the poem's final stanza, (In the fields that Winter wastes), for two flutes in 1720. The new setting of the cantata three years later by Francois Collin de Blamont was equally successful and made the name of its nineteen-year-old composer. Originally for voice and bass continuo, it was expanded and considerably revised in 1729, with parts for flute, violin and viol added. Towards the end of the century, the choral setting by Georges Granges de Fontenelle (1769–1819) was equally to bring its young composer fame.
Rousseau's poem was also familiar to composers of other nationalities. Set for mezzo-soprano and full orchestra, it was given almost operatic treatment by the court composer Luigi Cherubini in 1789. Franz Seydelmann set it for soprano and full orchestra in Dresden in 1787 at the request of the Russian ambassador to the Saxon Court, Prince Alexander Belosselsky, who spoke highly of Seydelmann's work. A later setting by Austrian composer Sigismond von Neukomm for soprano and full orchestra (Op. 4, 1810) was judged favorably by French musicologist Jacques Chailley in his 1966 article for the journal .
Recent treatments of the Circe theme include the Irish composer Gerard Victory's radio cantata Circe 1991 (1973–1975), David Gribble's A Threepenny Odyssey, a fifteen-minute cantata for young people which includes the episode on Circe's Isle, and Malcolm Hayes' Odysseus remembers (2003–04), which includes parts for Circe, Anticleia and Tiresias. Gerald Humel's song cycle Circe (1998) grew out of his work on his 1993 ballet with Thomas Höft. The latter subsequently wrote seven poems in German featuring Circe's role as seductress in a new light: here it is to freedom and enlightenment that she tempts her hearers. Another cycle of Seven Songs for High Voice and Piano (2008) by the American composer Martin Hennessey includes the poem "Circe's Power" from Louise Glück's Meadowlands (1997).
There have also been treatments of Circe in popular music, in particular the relation of the Odysseus episode in Friedrich Holländer's song of 1958. In addition, text in Homeric Greek is included in the "Circe's Island" episode in David Bedford's The Odyssey (1976). This was the ancestor of several later electronic suites that reference the Odysseus legend, with "Circe" titles among them, having little other programmatic connection with the myth itself.
===Classical ballet and programmatic music===
After classical ballet separated from theatrical spectacle into a wordless form in which the story is expressed solely through movement, the subject of Circe was rarely visited. It figured as the first episode of three with mythological themes in (New Shows), staged by Sieur Duplessis le cadet in 1734, but the work was taken off after its third performance and not revived. The choreographer Antoine Pitrot also staged , describing it as a ballet sérieux, heroï-pantomime in 1764. Thereafter there seems to be nothing until the revival of ballet in the 20th century.
In 1963, the American choreographer Martha Graham created her Circe with a score by Alan Hovhaness. Its theme is psychological, representing the battle with animal instincts. The beasts portrayed extend beyond swine and include a goat, a snake, a lion and a deer. The theme has been described as one of "highly charged erotic action", although set in "a world where sexual frustration is rampant". In that same decade Rudolf Brucci composed his Kirka (1967) in Croatia.
There is a Circe episode in John Harbison's Ulysses (Act 1, scene 2, 1983) in which the song of the enchantress is represented by ondes Martenot and tuned percussion. After the sailors of Ullyses are transformed into animals by her spell, a battle of wills follows between Circe and the hero. Though the men are changed back, Ulysses is charmed by her in his turn. In 1993, a full scale treatment of the story followed in Gerald Humel's two-act Circe und Odysseus. Also psychological in intent, it represents Circe's seduction of the restless hero as ultimately unsuccessful. The part played by the geometrical set in its Berlin production was particularly notable.
While operas on the subject of Circe did not cease, they were overtaken for a while by the new musical concept of the symphonic poem which, whilst it does not use a sung text, similarly seeks a union of music and drama. A number of purely musical works fall into this category from the late 19th century onwards, of which one of the first was Heinrich von Herzogenberg's Odysseus (Op.16, 1873). A Wagnerian symphony for large orchestra, dealing with the hero's return from the Trojan war, its third section is titled "Circe's Gardens" (Die Gärten der Circe).
In the 20th century, 's cycle Aus Odysseus Fahrten (From Odysseus' Voyage, Op. 6, 1903) was equally programmatic and included the visit to Circe's Isle (Die Insel der Circe) as its second long section. After a depiction of the sea voyage, a bass clarinet passage introduces an ensemble of flute, harp and solo violin over a lightly orchestrated accompaniment, suggesting Circe's seductive attempt to hold Odysseus back from traveling further. Alan Hovhaness' Circe Symphony (No.18, Op. 204a, 1963) is a late example of such programmatic writing. It is, in fact, only a slightly changed version of his ballet music of that year, with the addition of more strings, a second timpanist and celesta.
With the exception of Willem Frederik Bon's prelude for orchestra (1972), most later works have been for a restricted number of instruments. They include Hendrik de Regt's Circe (Op. 44, 1975) for clarinet, violin and piano; Christian Manen's Les Enchantements De Circe (Op. 96, 1975) for bassoon and piano; and Jacques Lenot's Cir(c)é (1986) for oboe d'amore. The German experimental musician Dieter Schnebel's Circe (1988) is a work for harp, the various sections of which are titled Signale (signals), Säuseln (whispers), Verlockungen (enticements), Pein (pain), Schläge (strokes) and Umgarnen (snare), which give some idea of their programmatic intent.
Thea Musgrave's "Circe" for three flutes (1996) was eventually to become the fourth piece in her six-part Voices from the Ancient World for various combinations of flute and percussion (1998). Her note on these explains that their purpose is to "describe some of the personages of ancient Greece" and that Circe was "the enchantress who changed men into beasts". A recent reference is the harpsichordist Fernando De Luca's Sonata II for viola da gamba titled "Circe's Cave" (L'antro della maga Circe).
=== Opera ===
La Circe by Pietro Andrea Ziani, first performed for the birthday of the Holy Roman Emperor Leopold I in Vienna in 1665.
Circe, an opera composed by Henri Desmarets in 1694.
La Circe, a 1779 opera seria by Josef Mysliveček.
Rolf Riehm's 2014 opera Sirenen is based on Homer's account as well as several modern texts related to the meeting of Odysseus and Circe.
==Scientific interpretations==
In later Christian opinion, Circe was an abominable witch using miraculous powers to evil ends. When the existence of witches came to be questioned, she was reinterpreted as a depressive suffering from delusions.
In botany, the Circaea are plants belonging to the enchanter's nightshade genus. The name was given by botanists in the late 16th century in the belief that this was the herb used by Circe to charm Odysseus' companions. Medical historians have speculated that the transformation to pigs was not intended literally but refers to anticholinergic intoxication with the plant Datura stramonium. Symptoms include amnesia, hallucinations, and delusions. The description of "moly" fits the snowdrop, a flower that contains galantamine, which is a long lasting anticholinesterase and can therefore counteract anticholinergics that are introduced to the body after it has been consumed. – claimed descent from Mamilia, a granddaughter of Odysseus and Circe through Telegonus. One of the most well known of them was Octavius Mamilius (died 498 BC), princeps of Tusculum and son-in-law of Lucius Tarquinius Superbus the seventh and last king of Rome.
Linnaeus named a genus of the Venus clams (Veneridae) after Circe in 1778 (species Circe scripta (Linnaeus, 1758) and others).
Her name has been given to 34 Circe, a large, dark main-belt asteroid first sighted in 1855.
There are a variety of chess variants named Circe in which captured pieces are reborn on their starting positions. The rules for this were formulated in 1968.
The Circe effect, coined by the enzymologist William Jencks, refers to a scenario where an enzyme lures its substrate towards it through electrostatic forces exhibited by the enzyme molecule before transforming it into a product. Where this takes place, the catalytic velocity (rate of reaction) of the enzyme may be significantly faster than that of others.
== In popular culture ==
== Genealogy ==
|
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"A. D. Hope",
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"Remedia Amoris",
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"Carl Linnaeus",
"Fitzwilliam Museum",
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"Perses (brother of Aeetes)",
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"Fernando De Luca",
"Elba",
"LSJ",
"William Shakespeare",
"aria",
"Saracen",
"The Fox and the Crow (Aesop)",
"anticholinesterase",
"Thomas Love Peacock",
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"Satyr",
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"Lycophron",
"Troy",
"Classical antiquity",
"Louis Fuzelier",
"Anaxilas (comic poet)",
"princeps",
"swine",
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"Moly (herb)",
"ondes Martenot",
"Rudolf Brucci",
"Etruscan civilization",
"Dionysiaca",
"Diodorus Siculus",
"George Romney (painter)",
"Circe Offering the Cup to Ulysses",
"Livy",
"Ulysses (1954 film)",
"Calypso (mythology)",
"Hyperion (Titan)",
"Giovanni Pascoli",
"Dictionary of Greek and Roman Biography and Mythology",
"Mary Cecil Allen",
"Metamorphoses",
"Ardea, Lazio",
"Mount Circeo",
"Jane Lightfoot",
"Cassiphone",
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"Thomas Jefferys",
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"Greek mythology",
"John G. Demaray",
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"Rome",
"Thea Musgrave",
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"countertenor",
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"Louis-Nicolas Ménard",
"Michel Blavet",
"Shapeshifting",
"Titan (mythology)",
"La Fontaine's Fables",
"De Natura Deorum",
"Ab Urbe Condita Libri",
"Franz von Stuck",
"Saturn (mythology)",
"Walters Art Museum",
"Merriam-Webster",
"Circe and Her Lovers in a Landscape",
"Minotaur",
"harpsichord",
"Ludovico Ariosto",
"kylix (drinking cup)",
"Absyrtus",
"Geographica",
"Tanglewood Tales",
"Ephippus of Athens",
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"William Smith (lexicographer)",
"Iliad",
"Perses of Colchis",
"Harvard Advocate",
"delusion",
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"Picolous",
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"Josef Mysliveček",
"Emma Hamilton",
"Hermes",
"Geneviève Vix",
"Die Deutsche Bühne",
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"Medea",
"Sigismond von Neukomm",
"conversation piece",
"Daunians",
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"Hercules",
"Joseph Albert Alexandre Glatigny",
"Edmund Spenser",
"Baroque",
"Niccolò Machiavelli",
"Friedrich Holländer",
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"Theogony",
"Cypselus",
"Gryll Grange",
"Daniel Gardner",
"masque",
"Yevonde Middleton",
"Eurylochus (mythology)",
"Jacques Lenot",
"Elpenor",
"Tusculum",
"Glaucus",
"Marc-Antoine Legrand",
"Homer",
"Telemachus",
"Comus (John Milton)",
"Geoffrey Whitney",
"Circé (Desmarets)",
"scholia",
"34 Circe",
"Miasma (Greek mythology)",
"Heinrich von Herzogenberg",
"Victorian morality",
"amnesia",
"Helios",
"Xenagoras (historian)",
"Henri Desmarets",
"Apollonius Rhodius",
"Luigi Cherubini",
"Aeëtes",
"amphora",
"Opéra-Comique",
"Jean-Baptiste Rousseau",
"George Frederic Watts",
"Circe chess",
"Perimede (mythology)",
"Nostalgie de la boue",
"recitative",
"Odysseus",
"John Gower",
"king of Rome",
"Nonnus",
"T.S.Eliot",
"Datura stramonium",
"Jerusalem Delivered",
"Martha Graham",
"Golden Fleece",
"Giordano Bruno",
"Matthew Arnold",
"Canens (mythology)",
"Gaius Valerius Flaccus (poet)",
"Hermeticism",
"Pietro Andrea Ziani",
"Morgan le Fay",
"art of memory",
"Rolf Riehm",
"William Jencks",
"Edward Burne-Jones",
"Alan Hovhaness",
"Italy",
"symphonic poem",
"flute",
"cello",
"Dionysus",
"Catalogue of Women",
"Nikos Kazantzakis",
"Ptolemaeus Chennus",
"Uranus (mythology)",
"Ardeias",
"Aloeus",
"Urganda",
"Pasiphaë",
"minuet",
"Joshua Reynolds",
"Latin",
"Minos",
"Lope de Vega",
"James Joyce",
"Gerard Victory",
"Ancient Greek religion",
"Telegonus (son of Odysseus)",
"enchanter's nightshade",
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"Spiritualism (movement)",
"skyphos",
"Gaius Julius Hyginus",
"Magician (paranormal)",
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"Giovan Battista Gelli",
"snowdrop",
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"A Midsummer Night's Dream",
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"Christian Manen",
"Etruscans"
] |
5,958 |
CPR (disambiguation)
|
Cardiopulmonary resuscitation (CPR) is an emergency procedure to assist someone who has suffered cardiac arrest.
CPR may also refer to:
==Science and technology==
Candidate phyla radiation, bacteria precursors.
Certificate Problem Report, a notice to certificate authorities informing them of a reasonable cause to revoke a digital certificate.
Classification of Pharmaco-Therapeutic Referrals, a taxonomy to define situations requiring a referral from pharmacists to physicians
COM port redirection in computing
Competent Persons Report, in Oil and Gas; see Lancaster oilfield
Continuous Plankton Recorder, marine biological monitoring program
Curved planar reconstruction, in computed tomography
Cubase Project Files, work files used in Steinberg Cubase
Cursor Position Report, an ANSI X3.64 escape sequence
Cytochrome P450 reductase, an enzyme
==Organizations==
American Bar Association Model Code of Professional Responsibility
Center for Performance Research
Centre for Policy Research, a think tank in New Delhi, India
Chicago Project Room, former art gallery in Chicago and Los Angeles
Communist Party of Réunion, in the French département of Réunion
Communist Party of Russia (disambiguation), various meanings
Congress for the Republic, a Tunisian political party
Conservatives for Patients' Rights, a pressure group founded and funded by Rick Scott that argues for private insurance methods to pay for healthcare
Det Centrale Personregister (Civil Registration System), Denmark's nationwide civil registry
==Transportation==
Canadian Pacific Railway, which served major cities in Canada and the northeastern US between 1881 and 2023
Car plate recognition, or automatic number plate recognition
Casper–Natrona County International Airport (IATA Code), in Casper, Wyoming, US
Cornelius Pass Road, in Oregon, US
Compact Position Reporting, a method of encoding an aircraft's latitude and longitude in ADS-B position messages
==Entertainment and music==
Chicago Public Radio, former name of WBEZ
Club Penguin Rewritten, 2017 fangame
Colorado Public Radio
CPR (band) or Crosby, Pevar & Raymond, a former rock/jazz band
CPR (album)
Corporate Punishment Records, a record label
CPR (EP), a 2003 EP by Dolour
"CPR", a song by CupcakKe from the album Queen Elizabitch
==Other uses==
Calendar of the Patent Rolls, a book series translating and summarising the medieval Patent Rolls documents
Challenge Prince Rainier III, top division association football league in Monaco
Chinese People's Republic, another alternate official name for China (UNDP country code CPR)
Civil Procedure Rules, a civil court procedure rules for England and Wales
Common-pool resource, a type of good, including a resource system
Common property regime
Concrete Pavement Restoration, a method used by the International Grooving & Grinding Association
Conditional Prepayment Rate, a measurement for Prepayment of loan
Condominium Property Regime, a type of condominium conversion common in Hawai'i
Construction Products Regulation, Regulation (EU) No. 305/2011
Critique of Pure Reason, a 1781 philosophical work by Immanuel Kant
Corporate political responsibility, a corporate responsibility concept
|
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"Chinese People's Republic",
"CPR (band)",
"Common-pool resource",
"Lancaster oilfield",
"CPR (EP)",
"ANSI CPR",
"certificate revocation",
"Patent Rolls",
"International Grooving & Grinding Association",
"Car plate recognition",
"Communist Party of Réunion",
"Centre for Policy Research",
"Chicago Public Radio",
"Canadian Pacific Railway",
"condominium conversion",
"Det Centrale Personregister",
"CPR-1000",
"Conservatives for Patients' Rights",
"CT scan",
"Chicago Project Room",
"Corporate political responsibility",
"Classification of Pharmaco-Therapeutic Referrals",
"Colorado Public Radio",
"CPR (album)",
"Cytochrome P450 reductase",
"Queen Elizabitch",
"Communist Party of Russia (disambiguation)",
"Central Pacific Railroad",
"Candidate phyla radiation",
"American Bar Association Model Code of Professional Responsibility",
"Critique of Pure Reason",
"Center for Performance Research",
"Prepayment of loan",
"Regulation (EU) No. 305/2011",
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"Corporate Punishment Records",
"Steinberg Cubase",
"Civil Procedure Rules",
"Continuous Plankton Recorder",
"Challenge Prince Rainier III",
"certificate authority",
"Commons",
"Cornelius Pass Road",
"ADS-B",
"digital certificate",
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"COM port redirection",
"Carolwood Pacific Railroad"
] |
5,959 |
Canadian Pacific Railway
|
The Canadian Pacific Railway () , also known simply as CPR or Canadian Pacific and formerly as CP Rail (1968–1996), is a Canadian Class I railway incorporated in 1881. The railway is owned by Canadian Pacific Kansas City Limited, known until 2023 as Canadian Pacific Railway Limited, which began operations as legal owner in a corporate restructuring in 2001.
The railway is headquartered in Calgary, Alberta. In 2023, the railway owned approximately of track in seven provinces of Canada and into the United States, also served Minneapolis–St. Paul, Milwaukee, Detroit, Chicago, and Albany, New York, in the United States.
The railway was first built between eastern Canada and British Columbia between 1875 and 1885 (connecting with Ottawa Valley and Georgian Bay area lines built earlier), fulfilling a commitment extended to British Columbia when it entered Confederation in 1871; the CPR was Canada's first transcontinental railway. Primarily a freight railway, the CPR was for decades the only practical means of long-distance passenger transport in most regions of Canada and was instrumental in the colonization and development of Western Canada. The CPR became one of the largest and most powerful companies in Canada, a position it held as late as 1975. The company acquired two American lines in 2009: the Dakota, Minnesota and Eastern Railroad (DM&E) and the Iowa, Chicago and Eastern Railroad (IC&E). Also, the company owns the Indiana Harbor Belt Railroad, a Hammond, Indiana-based terminal railroad along with Conrail Shared Assets Operations. CPR purchased the Kansas City Southern Railway in December 2021 for . On April 14, 2023, KCS became a wholly owned subsidiary of CPR, and both CPR and its subsidiaries began doing business under the name of its parent company, CPKC.
The CPR is publicly traded on both the Toronto Stock Exchange and the New York Stock Exchange under the ticker CP. Its U.S. headquarters are in Minneapolis. As of March 30, 2023, the largest shareholder of Canadian Pacific stock exchange is TCI Fund Management Limited, a London-based hedge fund that owns 6% of the company.
==History==
The creation of the Canadian Pacific Railway was undertaken as the National Dream by the Conservative government of John A. Macdonald, together with mining magnate Alexander Tilloch Galt. As a condition for joining the Canadian Confederation, British Columbia had insisted on a transport link to the East, with the rest of the Confederation. In 1873, Macdonald, among other high-ranking politicians, bribed in the Pacific Scandal, granted contracts to the Canada Pacific Railway Company, which was unrelated to the current company, as opposed to the Inter-Ocean Railway Company, which was thought to have connections to the Northern Pacific Railway Company in the United States. After this scandal, the Conservatives were removed from power, and Alexander Mackenzie, the new Liberal prime minister, ordered construction of the railway under the supervision of the Department of Public Works.
Enabled by the CPR Act of 1874, work began in 1875 on the Lake Superior to Manitoba section of the CPR. The ceremonial sod-turning at Westfort on June 1, 1875, was prominently reported in the June 10 edition of the Toronto Globe. It noted that a crowd of "upwards of 500 ladies and gentlemen" gathered to celebrate the event on the left bank of the Kaministiquia River in the District of Thunder Bay, about four miles upriver from Fort William. Once completed in 1882 with a last spike at Feist Lake, near Vermilion Bay, Ontario, the line was turned over to the newly-minted private Canadian Pacific Railway company. In 1883, the first wheat shipment from Manitoba was transported over this line to the Lakehead (Fort William and Port Arthur) on Lake Superior.
Macdonald would later return as prime minister and adopt a more aggressive construction policy; bonds were floated in London and called for tenders to complete sections of the railway in British Columbia. American contractor Andrew Onderdonk was selected, and his men began construction on May 15, 1880.
In October 1880, a new consortium signed a contract with the Macdonald government, agreeing to build the railway for $25 million in credit and of land. In addition, the government defrayed surveying costs and exempted the railway from property taxes for 20 years.
A beaver was chosen as the railway's logo in honour of Donald Smith, 1st Baron Strathcona and Mount Royal, who had risen from factor to governor of the Hudson's Bay Company over a lengthy career in the beaver fur trade.
===Building the railway, 1881–1886===
Building the railway took over four years. The Canadian Pacific Railway began its westward expansion from Bonfield, Ontario, where the first spike was driven into a sunken railway tie. That was the point where the Canada Central Railway (CCR) extension ended. The CCR started in Brockville and extended to Pembroke. It then followed a westward route along the Ottawa River and continued to Mattawa at the confluence of the Mattawa and Ottawa rivers. It then proceeded to Bonfield.
It was presumed that the railway would travel through the rich "fertile belt" of the North Saskatchewan River Valley and cross the Rocky Mountains via the Yellowhead Pass. However, a more southerly route across the arid Palliser's Triangle in Saskatchewan and via Kicking Horse Pass and down the Field Hill to the Rocky Mountain Trench was chosen.
In 1881, construction progressed at a pace too slow for the railway's officials who, in 1882, hired the renowned railway executive William Cornelius Van Horne to oversee construction. Van Horne stated that he would have of main line built in 1882. Floods delayed the start of the construction season, but over of main line, as well as sidings and branch lines, were built that year.
The Thunder Bay branch (west from Fort William) was completed in June 1882 by the Department of Railways and Canals and turned over to the company in May 1883. By the end of 1883, the railway had reached the Rocky Mountains, just east of Kicking Horse Pass. The treacherous of railway west of Fort William was completed by Purcell & Company, headed by "Canada's wealthiest and greatest railroad contractor," industrialist Hugh Ryan.
Many thousands of navvies worked on the railway. Many were European immigrants. An unknown number of Stoney Nakoda also assisted in track laying and construction work in the Kicking Horse Pass region. In British Columbia, government contractors eventually hired 17,000 workers from China, known as "coolies". After months of hard labour, they could net as little as $16 ($ in adjusted for inflation) Chinese labourers in British Columbia made only between 75 cents and $1.25 a day, paid in rice mats, and not including expenses, leaving barely anything to send home. They did the most dangerous construction jobs, such as working with explosives to clear tunnels through rock. The exact number of Chinese workers who died is unknown, but historians estimate the number is between 600 and 800.
By 1883, railway construction was progressing rapidly, but the CPR was in danger of running out of funds. In response, on January 31, 1884, the government passed the Railway Relief Bill, providing a further $22.5 million in loans to the CPR. The bill received royal assent on March 6, 1884.
In March 1885, the North-West Rebellion broke out in the District of Saskatchewan. Van Horne, in Ottawa at the time, suggested to the government that the CPR could transport troops to Qu'Appelle in the District of Assiniboia in 10 days. Some sections of track were incomplete or had not been used before, but the trip to Winnipeg was made in nine days and the rebellion quickly suppressed. Controversially, the government subsequently reorganized the CPR's debt and provided a further $5 million loan. This money was desperately needed by the CPR. Even with Van Horne's support with moving troops to Qu'Appelle, the government still delayed in giving its support to CPR, due to Macdonald pressuring George Stephen for additional benefits.
On November 7, 1885, the last spike was driven at Craigellachie, British Columbia. Four days earlier, the last spike of the Lake Superior section was driven in just west of Jackfish, Ontario. While the railway was completed four years after the original 1881 deadline, it was completed more than five years ahead of the new date of 1891 that Macdonald gave in 1881.
In Eastern Canada, the CPR had created a network of lines reaching from Quebec City to St. Thomas, Ontario, by 1885 mainly by buying the Quebec, Montreal, Ottawa & Occidental Railway from the Quebec government and by creating a new railway company, the Ontario and Quebec Railway (O&Q). It also launched a fleet of Great Lakes ships to link its terminals. Through the O&Q, the CPR had effected purchases and long-term leases of several railways, and built a line between Perth, Ontario, and Toronto (completed on May 5, 1884) to connect these acquisitions. The CPR obtained a 999-year lease on the O&Q on January 4, 1884. In 1895, it acquired a minority interest in the Toronto, Hamilton and Buffalo Railway, giving it a link to New York and the Northeast United States.
===1886–1900===
The last spike in the CPR was driven on November 7, 1885, by one of its directors, Donald Smith.
By that time, however, the CPR had decided to move its western terminus from Port Moody to Granville, which was renamed "Vancouver" later that year. The first official train destined for Vancouver arrived on May 23, 1887, although the line had already been in use for three months. The CPR quickly became profitable, and all loans from the federal government were repaid years ahead of time. In 1888, a branch line was opened between Sudbury and Sault Ste. Marie where the CPR connected with the American railway system and its own steamships. That same year, work was started on a line from London, Ontario, to the Canada–US border at Windsor, Ontario. That line opened on June 12, 1890.
The CPR also leased the New Brunswick Railway in 1891 for 991 years, and built the International Railway of Maine, connecting Montreal with Saint John, New Brunswick, in 1889. The connection with Saint John on the Atlantic coast made the CPR the first truly transcontinental railway company in Canada and permitted trans-Atlantic cargo and passenger services to continue year-round when sea ice in the Gulf of St. Lawrence closed the port of Montreal during the winter months. By 1896, competition with the Great Northern Railway for traffic in southern British Columbia forced the CPR to construct a second line across the province, south of the original line. Van Horne, now president of the CPR, asked for government aid, and the government agreed to provide around $3.6 million to construct a railway from Lethbridge, Alberta, through Crowsnest Pass to the south shore of Kootenay Lake, in exchange for the CPR agreeing to reduce freight rates in perpetuity for key commodities shipped in Western Canada.
The controversial Crowsnest Pass Agreement effectively locked the eastbound rate on grain products and westbound rates on certain "settlers' effects" at the 1897 level. Although temporarily suspended during the First World War, it was not until 1983 that the "Crow Rate" was permanently replaced by the Western Grain Transportation Act, which allowed the gradual increase of grain shipping prices. The Crowsnest Pass line opened on June 18, 1898, and followed a complicated route through the maze of valleys and passes in southern British Columbia, rejoining the original mainline at Hope after crossing the Cascade Mountains via Coquihalla Pass.
The Southern Mainline, generally known as the Kettle Valley Railway in British Columbia, was built in response to the booming mining and smelting economy in southern British Columbia, and the tendency of the local geography to encourage and enable easier access from neighbouring US states than from Vancouver or the rest of Canada, which was viewed to be as much of a threat to national security as it was to the province's control of its own resources. The local passenger service was re-routed to this new southerly line, which connected numerous emergent small cities across the region. Independent railways and subsidiaries that were eventually merged into the CPR in connection with this route were the Shuswap and Okanagan Railway, the Kaslo and Slocan Railway, the Columbia and Kootenay Railway, the Columbia and Western Railway and various others. To transport immigrants, Canadian Pacific developed a fleet of over a thousand Colonist cars, low-budget sleeper cars designed to transport immigrant families from eastern Canadian seaports to the west.
===1901–1914===
During the first decade of the 20th century, the CPR continued to build more lines. In 1908, the CPR opened a line connecting Toronto with Sudbury. Several operational improvements were also made to the railway in Western Canada.
On November 3, 1909, the Lethbridge Viaduct over the Oldman River valley at Lethbridge, Alberta, was opened. It is long and, at its maximum, high, making it one of the longest railway bridges in Canada. In 1916, the CPR replaced its line through Rogers Pass, which was prone to avalanches (the most serious of which killed 62 men in 1910) with the Connaught Tunnel, an eight-kilometre-long (5-mile) tunnel under Mount Macdonald that was, at the time of its opening, the longest railway tunnel in the Western Hemisphere.
On January 21, 1910, a passenger train derailed on the CPR line at the Spanish River bridge at Nairn, Ontario (near Sudbury), killing at least 43.
On January 3, 1912, the CPR acquired the Dominion Atlantic Railway, a railway that ran in western Nova Scotia. This acquisition gave the CPR a connection to Halifax, a significant port on the Atlantic Ocean. The CPR acquired the Quebec Central Railway on December 14, 1912.
===First World War===
During the First World War, CPR put the entire resources of the "world's greatest travel system" at the disposal of the British Empire, not only trains and tracks, but also its ships, shops, hotels, telegraphs and, above all, its people. Aiding the war effort meant transporting and billeting troops; building and supplying arms and munitions; arming, lending and selling ships. Fifty-two CPR ships were pressed into service during World War I, carrying more than a million troops and passengers and four million tons of cargo. Twenty seven survived and returned to CPR. CPR also helped the war effort with money and jobs. CPR made loans and guarantees to the Allies of some $100 million. As a lasting tribute, CPR commissioned three statues and 23 memorial tablets to commemorate the efforts of those who fought and those who died in the war. After the war, the Federal government created Canadian National Railways (CNR, later CN) out of several bankrupt railways that fell into government hands during and after the war. CNR would become the main competitor to the CPR in Canada. In 1923, Henry Worth Thornton replaced David Blyth Hanna becoming the second president of the CNR, and his competition spurred Edward Wentworth Beatty, the first Canadian-born president of the CPR, to action. During this time the railway land grants were formalized.
===Great Depression and the Second World War, 1929–1945===
The Great Depression, which lasted from 1929 until 1939, hit many companies heavily. While the CPR was affected, it was not affected to the extent of its rival CNR because it, unlike the CNR, was debt-free. The CPR scaled back on some of its passenger and freight services and stopped issuing dividends to its shareholders after 1932. Hard times led to the creation of new political parties such as the Social Credit movement and the Cooperative Commonwealth Federation, as well as popular protest in the form of the On-to-Ottawa Trek.
One highlight of the late 1930s, both for the railway and for Canada, was the visit of King George VI and Queen Elizabeth during their 1939 royal tour of Canada, the first time that the reigning monarch had visited the country. The CPR and the CNR shared the honours of pulling the royal train across the country, with the CPR undertaking the westbound journey from Quebec City to Vancouver. Later that year, the Second World War began. As it had done in World War I, the CPR devoted much of its resources to the war effort. It retooled its Angus Shops in Montreal to produce Valentine tanks and other armoured vehicles, and transported troops and resources across the country. Additionally, 22 of the CPR's ships went to war, 12 of which were sunk.
===1946–1978===
After the Second World War, the transportation industry in Canada changed. Where railways had previously provided almost universal freight and passenger services, cars, trucks and airplanes started to take traffic away from railways. This naturally helped the CPR's air and trucking operations, and the railway's freight operations continued to thrive hauling resource traffic and bulk commodities. However, passenger trains quickly became unprofitable. During the 1950s, the railway introduced new innovations in passenger service. In 1955, it introduced The Canadian, a new luxury transcontinental train. However, in the 1960s, the company started to pull out of passenger services, ending services on many of its branch lines. It also discontinued its secondary transcontinental train The Dominion in 1966, and in 1970, unsuccessfully applied to discontinue The Canadian. For the next eight years, it continued to apply to discontinue the service, and service on The Canadian declined markedly. On October 29, 1978, CP Rail transferred its passenger services to Via Rail, a new federal Crown corporation that is responsible for managing all intercity passenger service formerly handled by both CP Rail and CN. Via eventually took almost all of its passenger trains, including The Canadian, off CP's lines.
In 1968, as part of a corporate reorganization, each of the major operations, including its rail operations, were organized as separate subsidiaries. The name of the railway was changed to CP Rail, and the parent company changed its name to Canadian Pacific Limited in 1971. Its air, express, telecommunications, hotel and real estate holdings were spun off, and ownership of all of the companies transferred to Canadian Pacific Investments. The slogan was: "TO THE FOUR CORNERS OF THE WORLD". The company discarded its beaver logo, adopting the new Multimark (which, when mirrored by an adjacent "multi-mark" creates a diamond appearance on a globe) that was used – with a different colour background – for each of its operations.
===1979–2001===
==== The 1979 Mississauga train derailment ====
On November 10, 1979, a derailment of a hazardous materials train in Mississauga, Ontario, led to the evacuation of 200,000 people; there were no fatalities. Mississauga Mayor Hazel McCallion threatened to sue Canadian Pacific for the derailment. Part of the compromise was to accept GO Transit commuter rail service along the Galt Subdivision corridor up to Milton, Ontario. Limited trains ran along the Milton line on weekdays only. Expansions to Cambridge, Ontario may be coming in the future.
In 1984, CP Rail commenced construction of the Mount Macdonald Tunnel to augment the Connaught Tunnel under the Selkirk Mountains. The first revenue train passed through the tunnel in 1988. At 14.7 km (nine miles), it is the longest tunnel in the Americas. During the 1980s, the Soo Line Railroad, in which CP Rail still owned a controlling interest, underwent several changes. It acquired the Minneapolis, Northfield and Southern Railway in 1982. Then on February 21, 1985, the Soo Line obtained a controlling interest in the bankrupt Milwaukee Road, merging it into its system on January 1, 1986. Also in 1980, Canadian Pacific bought out the controlling interests of the Toronto, Hamilton and Buffalo Railway (TH&B) from Conrail and molded it into the Canadian Pacific System, dissolving the TH&B's name from the books in 1985. In 1987, most of CPR's trackage in the Great Lakes region, including much of the original Soo Line, were spun off into a new railway, the Wisconsin Central, which was subsequently purchased by CN. Influenced by the Canada-U.S. Free Trade Agreement of 1989, which liberalized trade between the two nations, the CPR's expansion continued during the early 1990s: CP Rail gained full control of the Soo Line in 1990, adding the "System" to the former's name, and bought the Delaware and Hudson Railway in 1991. These two acquisitions gave CP Rail routes to the major American cities of Chicago (via the Soo Line and Milwaukee Road as part of its historically logical route) and New York City (via the D&H).
During the 1990s, both CP Rail and CN attempted unsuccessfully to buy out the eastern assets of the other, so as to permit further rationalization. In 1996, CP Rail moved its head office from Windsor Station in Montreal to Gulf Canada Square in Calgary and changed its name back to Canadian Pacific Railway.
A new subsidiary company, the St. Lawrence and Hudson Railway, was created to operate its money-losing lines in eastern North America, covering Quebec, Southern and Eastern Ontario, trackage rights to Chicago, Illinois, (on Norfolk Southern lines from Detroit) as well as the Delaware and Hudson Railway in the northeastern United States. However, the new subsidiary, threatened with being sold off and free to innovate, quickly spun off money-losing track to short lines, instituted scheduled freight service, and produced an unexpected turn-around in profitability. On 1 January 2001 the StL&H was formally amalgamated with the CP Rail system.
===2001 to 2023===
In 2001, the CPR's parent company, Canadian Pacific Limited, spun off its five subsidiaries, including the CPR, into independent companies. In September 2007, CPR announced it was acquiring the Dakota, Minnesota and Eastern Railroad from London-based Electra Private Equity. The merger was completed as of October 31, 2008.
Canadian Pacific Railway Ltd. trains resumed regular operations on June 1, 2012, after a nine-day strike by some 4,800 locomotive engineers, conductors and traffic controllers who walked off the job on May 23, stalling Canadian freight traffic and costing the economy an estimated (). The strike ended with a government back-to-work bill forcing both sides to come to a binding agreement.
On July 6, 2013, a unit train of crude oil which CP had subcontracted to short-line operator Montreal, Maine and Atlantic Railway derailed in Lac-Mégantic, killing 47. On August 14, 2013, the Quebec government added the CPR, along with lessor World Fuel Services (WFS), to the list of corporate entities from which it seeks reimbursement for the environmental cleanup of the Lac-Mégantic derailment.
On October 12, 2014, it was reported that Canadian Pacific had tried to enter into a merger with American railway CSX, but was unsuccessful.
In 2015–16 Canadian Pacific sought to merge with American railway Norfolk Southern. and wanted to have a shareholder vote on it. CP ultimately terminated its efforts to merge on April 11, 2016.
On February 4, 2019, a loaded grain train ran away from the siding at Partridge just above the Upper Spiral Tunnel in Kicking Horse Pass. The 112-car grain train with three locomotives derailed into the Kicking Horse River just after the Trans Canada Highway overpass. The three crew members on the lead locomotive were killed. The Canadian Pacific Police Service (CPPS) investigated the fatal derailment. It later came to light that, although Creel said that the RCMP "retain jurisdiction" over the investigation, the RCMP wrote that "it never had jurisdiction because the crash happened on CP property". On January 26, 2020, Canadian current affairs program The Fifth Estate broadcast an episode on the derailment, and the next day the Canadian Transportation Safety Board (TSB) called for the RCMP to investigate as lead investigator Don Crawford said, "There is enough to suspect there's negligence here and it needs to be investigated by the proper authority".
On February 4, 2020, the TSB demoted its lead investigator in the crash probe after his superiors decided these comments were "completely inappropriate". The TSB stated that it "does not share the view of the lead safety investigator". The CPPS say they did a thorough investigation into the actions of the crew, which is now closed and resulted in no charges, while the Alberta Federation of Labour and the Teamsters Canada Rail Conference called for an independent police probe.
On November 20, 2019, it was announced that Canadian Pacific would purchase the Central Maine and Quebec Railway from Fortress Transportation and Infrastructure Investors. The line has had a series of different owners since being spun off of the Canadian Pacific in 1995. The first operator was the Canadian American Railroad a division of Iron Road Railways. In 2002 the Montreal, Maine & Atlantic took over operations after CDAC declared bankruptcy. The Central, Maine and Quebec Railway started operations in 2014 after the MMA declared bankruptcy due to the Lac-Mégantic derailment. On this new acquisition, CP CEO Keith Creel remarked that this gives CP a true coast-to-coast network across Canada and an increased presence in New England. On June 4, 2020; Canadian Pacific bought the Central Maine and Quebec.
==== Merger with Kansas City Southern (2021–2023) ====
On March 21, 2021, CP announced that it was planning to purchase the Kansas City Southern Railway (KCS) for US$29 billion. The US Surface Transportation Board (STB) would first have to approve the purchase, which was expected to be completed by the middle of 2022.
However, a competing cash and stock offer was later made by Canadian National Railway (CN) on April 20 at $33.7 billion. On 13 May, KCS announced that they planned to accept the merger offer from CN, but would give CP until May 21 to come up with a higher bid. On May 21, KCS and CN agreed to a merger. However, CN's merger attempt was blocked by a STB ruling in August that the company could not use a voting trust to assume control of KCS, due to concerns about potentially reduced competition in the railroad industry.
On September 12, KCS accepted a new $31 billion offer from CP. Though CP's offer was lower than the offer made by CN, the STB permitted CP to use a voting trust to take control of KCS. That approval came on March 15, 2023, which permitted the railroads to merge as soon as April 14. On April 14, 2023, KCS officially became a subsidiary of CPR, and CPR with its subsidiaries began conducting business under the name of its parent company, Canadian Pacific Kansas City (CPKC).
==Freight trains==
Over half of CP's freight traffic is in grain (24% of 2016 freight revenue), intermodal freight (22%), and coal (10%) and the vast majority of its profits are made in western Canada. A major shift in trade from the Atlantic to the Pacific has caused serious drops in CPR's wheat shipments through Thunder Bay. It also ships chemicals and plastics (12% of 2016 revenue), automotive parts and assembled automobiles (6%), potash (6%), sulphur and other fertilizers (5%), forest products (5%), and various other products (11%). The busiest part of its railway network is along its main line between Calgary and Vancouver. Since 1970, coal has become a major commodity hauled by CPR. Coal is shipped in unit trains from coal mines in the mountains, including Sparwood, British Columbia, to terminals at Roberts Bank and North Vancouver, from where it is then shipped to Japan.
Grain is hauled by the CPR from the prairies to ports at Thunder Bay (the former cities of Fort William and Port Arthur), Quebec City and Vancouver, where it is then shipped overseas. The traditional winter export port was Saint John, New Brunswick, when ice closed the St. Lawrence River. Grain has always been a significant commodity hauled by the CPR; between 1905 and 1909, the CPR double-tracked its section of track between Fort William, Ontario (part of present-day Thunder Bay) and Winnipeg to facilitate grain shipments. For several decades this was the only long stretch of double-track mainline outside of urban areas on the CPR. Today, though the Thunder Bay-Winnipeg section is now single tracked, the CPR still has two long distance double track lines serving rural areas, including a stretch between Kent, British Columbia, and Vancouver which follows the Fraser River into the Coast Mountains, as well as the Canadian Pacific Winchester Sub, a stretch of double track mainline which runs from Smiths Falls, Ontario, through downtown Montreal which runs through many rural farming communities. However, CPR was, as of 2020, partially dismantling the stretch of double track mainline on the Winchester Sub.
==Passenger trains==
The train was the primary mode of long-distance transport in Canada until the 1960s. Among the many types of people who rode CPR trains were new immigrants heading for the prairies, military troops (especially during the two world wars) and upper class tourists. It also custom-built many of its passenger cars at its CPR Angus Shops to be able to meet the demands of the upper class.
The CPR also had a line of Great Lakes ships integrated into its transcontinental service. From 1884 until 1912, these ships linked Owen Sound on Georgian Bay to Fort William. Following a major fire in December 1911 that destroyed the grain elevator, operations were relocated to a new, larger port created by the CPR at Port McNicoll opening in May 1912. Five ships allowed daily service, and included the S.S. Assiniboia and S.S. Keewatin built in 1907 which remained in use until the end of service. Travellers went by train from Toronto to that Georgian Bay port, then travelled by ship to link with another train at the Lakehead. After World War II, the trains and ships carried automobiles as well as passengers. This service featured what was to become the last boat train in North America. The Steam Boat was a fast, direct connecting train between Toronto and Port McNicoll. The passenger service was discontinued at the end of season in 1965 with one ship, the Assiniboia, carrying on in freight service for two more years before being sold. Planned to be a floating restaurant, "Assiniboia" caught fire during renovations in 1969 and was subsequently scrapped. Meanwhile "Keewatin" which was laid up in 1966 and scheduled to be scrapped, was purchased by RJ and Diane Peterson in 1967 and towed to their marina in Douglas, Michigan to serve as a marine museum. Forty-five years later Skyline International CEO Gil Blutrich purchased "Keewatin" and engaged former crewman Eric Conroy to repatriate "Keewatin" to Port McNicoll and operate her as an historical attraction, which he did in 2012 through 2019. "Keewatin" was closed to visitors in 2020 as a result of the COVID-19 pandemic and did not reopen in Port McNicoll. In 2023 "Keewatin" was donated by Skyline to the Marine Museum of the Great Lakes at Kingston, and towed to Hamilton shipyards for restoration before proceeding to Kingston, where it reopened to visitors in 2024.
After the Second World War, passenger traffic declined as automobiles and airplanes became more common, but the CPR continued to innovate in an attempt to keep passenger numbers up. Beginning November 9, 1953, the CPR introduced Budd Rail Diesel Cars (RDCs) on many of its lines. Officially called "Dayliners" by the CPR, they were always referred to as Budd Cars by employees. Greatly reduced travel times and reduced costs resulted, which saved service on many lines for a number of years. The CPR went on to acquire the second largest fleet of RDCs totalling 52 cars. Only the Boston and Maine Railroad had more. This CPR fleet also included the rare model RDC-4 (which consisted of a mail section at one end and a baggage section at the other end with no formal passenger section). On April 24, 1955, the CPR introduced a new luxury transcontinental passenger train, The Canadian. The train provided service between Vancouver and Toronto or Montreal (east of Sudbury; the train was in two sections). The train, which operated on an expedited schedule, was pulled by diesel locomotives, and used new, streamlined, stainless steel rolling stock. This service was initially heavily promoted by the company and many images of the train, especially as it traversed the Canadian Rockies, were captured by CPR's official photographer Nicholas Morant. Featured in numerous advertising promotions worldwide, several such images have gained iconic status.
Starting in the 1960s, however, the railway started to discontinue much of its passenger service, particularly on its branch lines. For example, passenger service ended on its line through southern British Columbia and Crowsnest Pass in January 1964, and on its Quebec Central in April 1967, and the transcontinental train The Dominion was dropped in January 1966. On October 29, 1978, CP Rail transferred its passenger services to Via Rail, a new federal Crown corporation that was now responsible for intercity passenger services in Canada. Canadian Prime Minister Brian Mulroney presided over major cuts in Via Rail service on January 15, 1990. This ended service by The Canadian over CPR rails, and the train was rerouted on the former Super Continental route via Canadian National without a change of name. Where both trains had been daily prior to January 15, 1990, cuts, the surviving Canadian was only a three-times-weekly operation. In October 2012, The Canadian was reduced to twice-weekly for the six-month off-season period, and operates three-times-weekly for only six months a year. In addition to inter-city passenger services, the CPR also provided commuter rail services in Montreal. CP Rail introduced Canada's first bi-level passenger cars here in 1970. On October 1, 1982, the Montreal Urban Community Transit Commission (STCUM) assumed responsibility for the commuter services previously provided by CP Rail. It continues under the Metropolitan Transportation Agency (AMT).
Canadian Pacific Railway operates two commuter services under contract. GO Transit contracts CPR to operate 10 return trips between Milton and central Toronto in Ontario. In Montreal, 59 daily commuter trains run on CPR lines from Lucien-L'Allier Station to Candiac, Hudson and Blainville–Saint-Jérôme on behalf of the AMT. CP no longer operates Vancouver's West Coast Express on behalf of TransLink, a regional transit authority. Bombardier Transportation assumed control of train operations on May 5, 2014. Although CP Rail no longer owns the track nor operates the commuter trains, it handles dispatching of Metra trains on the Milwaukee District/North and Milwaukee District/West Lines in Chicago, on which the CP also provides freight service via trackage rights.
===Sleeping, Dining and Parlour Car Department===
Sleeping cars were operated by a separate department of the railway that included the dining and parlour cars and aptly named as the Sleeping, Dining and Parlour Car Department. The CPR decided from the very beginning that it would operate its own sleeping cars, unlike railways in the United States that depended upon independent companies that specialized in providing cars and porters, including building the cars themselves. Pullman was long a famous name in this regard; its Pullman porters were legendary. Other early companies included the Wagner Palace Car Company. Bigger-sized berths and more comfortable surroundings were built by order of the CPR's General Manager, William Van Horne, who was a large man himself. Providing and operating their own cars allowed better control of the service provided as well as keeping all of the revenue received, although dining-car services were never profitable. But railway managers realized that those who could afford to travel great distances expected such facilities, and their favourable opinion would bode well to attracting others to Canada and the CPR's trains.
==Express==
W. C. Van Horne decided from the very beginning that the CPR would retain as much revenue from its various operations as it could. This translated into keeping express, telegraph, sleeping car and other lines of business for themselves, creating separate departments or companies as necessary. This was necessary as the fledgling railway would need all the income it could get, and in addition, he saw some of these ancillary operations such as express and telegraph as being quite profitable. Others such as sleeping and dining cars were kept in order to provide better control over the quality of service being provided to passengers. Hotels were likewise crucial to the CPR's growth by attracting travellers.
Dominion Express Company was formed independently in 1873 before the CPR itself, although train service did not begin until the summer of 1882 at which time it operated over some of track from Rat Portage (Kenora) Ontario west to Winnipeg, Manitoba. It was soon absorbed into the CPR and expanded everywhere the CPR went. It was renamed Canadian Pacific Express Company on September 1, 1926, and the headquarters moved from Winnipeg, to Toronto, and the company also handled the establishment of the first money order system in Canada. It was operated as a separate company with the railway charging them to haul express cars on trains, and was initially highly profitable.
Express operations consisted of separate cars included on existing Canadian Pacific routes, were typically charged on a less-than-carload basis, and transported a wide range of goods, including fresh goods like dairy or flowers, refrigerated goods such as fish, transport of cash and jewellery, livestock with handlers and in some cases goods that took an entire carload, such as automobiles.
The company later expanded to shipping by transport truck. The company eventually became unprofitable, possibly due to competition from trucking companies, was purchased by an employee buyout in 1994 and renamed itself Interlink Systems.
==Special trains==
===Silk trains===
Between the 1890s and 1933, the CPR transported raw silk from Vancouver, where it had been shipped from the Orient, to silk mills in New York and New Jersey. A silk train could carry several million dollars' worth of silk, so they had their own armed guards. To avoid train robberies and so minimize insurance costs, they travelled quickly and stopped only to change locomotives and crews, which was often done in under five minutes. The silk trains had right over all other trains; even passenger trains (including the royal train of 1939) would be put in sidings to make the silk trains' trip faster. At the end of World War II, the invention of nylon made silk less valuable, so the silk trains died out.
===Funeral trains===
Funeral trains would carry the remains of important people, such as prime ministers. As the train would pass, mourners would be at certain spots to show respect. Two of the CPR's funeral trains are particularly well-known. On June 10, 1891, the funeral train of Prime Minister Sir John A. Macdonald ran from Ottawa to Kingston, Ontario. The train consisted of five heavily draped passenger cars and was pulled by 4-4-0 No. 283. On September 14, 1915, the funeral train of former CPR president Sir William Cornelius Van Horne ran from Montreal to Joliet, Illinois, pulled by 4-6-2 No. 2213.
===Royal trains===
The CPR ran a number of trains that transported members of the Canadian royal family when they toured the country, taking them through Canada's scenery, forests, and small towns, and enabling people to see and greet them. Their trains were elegantly decorated; some had amenities such as a post office and barber shop. The CPR's most notable royal train was in 1939, when the CPR and the CNR had the honour of carrying King George VI and Queen Elizabeth during their coast-to-coast-and-back tour of Canada; one company took the royal couple from Quebec City to Vancouver and the other company took them on the return journey to Halifax. This was the first tour of Canada by its reigning monarch. The steam locomotives used to pull the train included CPR 2850, a Hudson (4-6-4) built by Montreal Locomotive Works in 1938, CNR 6400, a U-4-a Northern (4-8-4) and CNR 6028 a U-1-b Mountain (4-8-2) type. They were specially painted royal blue, with the exception of CNR 6028 which was not painted, with silver trim as was the entire train. The locomotives ran across Canada, through 25 changes of crew, without engine failure. The King, somewhat of a railbuff, rode in the cab when possible. After the tour, King George gave the CPR permission to use the term "Royal Hudson" for the CPR locomotives and to display Royal Crowns on their running boards. This applied only to the semi-streamlined locomotives (2820–2864), not the "standard" Hudsons (2800–2819).
===Better Farming Train===
CPR provided the rolling stock for the Better Farming Train which toured rural Saskatchewan between 1914 and 1922 to promote the latest information on agricultural research. It was staffed by the University of Saskatchewan and operating expenses were covered by the Department of Agriculture.
===School cars===
Between 1927 and the early 1950s, the CPR ran a school car to reach children who lived in Northern Ontario, far from schools. A teacher would travel in a specially designed car to remote areas and would stay to teach in one area for two to three days, then leave for another area. Each car had a blackboard and a few sets of chairs and desks. They also contained miniature libraries and accommodation for the teacher.
===Silver Streak===
Major shooting for the 1976 film Silver Streak, a fictional comedy tale of a murder-ridden train trip from Los Angeles to Chicago, was done on the CPR, mainly in the Alberta area with station footage at Toronto's Union Station. The train set was so lightly disguised as the fictional "AMRoad" that the locomotives and cars still carried their original names and numbers, along with the easily identifiable CP Rail red-striped paint scheme. Most of the cars are still in revenue service on Via Rail Canada; the lead locomotive (CP 4070) and the second unit (CP 4067) were sold to Via Rail and CTCUM respectively.
===Holiday Train===
Starting in 1999, CP runs a Holiday Train along its main line during the months of November and December. The Holiday Train celebrates the holiday season and collects donations for community food banks and hunger issues. The Holiday Train also provides publicity for CP and a few of its customers. Each train has a box car stage for entertainers who are travelling along with the train.
The train is a freight train, but also pulls vintage passenger cars which are used as lodging/transportation for the crew and entertainers. Only entertainers and CP employees are allowed to board the train aside from a coach car that takes employees and their families from one stop to the next. All donations collected in a community remain in that community for distribution.
There are two Holiday Trains that cover 150 stops in Canada and the United States Northeast and Midwest. Each train is roughly in length with brightly decorated railway cars, including a modified box car that has been turned into a travelling stage for performers. They are each decorated with hundred of thousands of LED Christmas lights. In 2013 to celebrate the program's 15th year, three signature events were held in Hamilton, Ontario, Calgary, Alberta, and Cottage Grove, Minnesota, to further raise awareness for hunger issues.
The trains feature different entertainers each year; in 2016, one train featured Dallas Smith and the Odds, while the other featured Colin James and Kelly Prescott. After its 20th anniversary tour in 2018, which hosted Terri Clark, Sam Roberts Band, The Trews and Willy Porter, the tour reported to have raised more than and collected more than of food since 1999.
===Royal Canadian Pacific===
On June 7, 2000, the CPR inaugurated the Royal Canadian Pacific, a luxury excursion service that operates between the months of June and September. It operates along a route from Calgary, through the Columbia Valley in British Columbia, and returning to Calgary via Crowsnest Pass. The trip takes six days and five nights. The train consists of up to eight luxury passenger cars built between 1916 and 1931 and is powered by first-generation diesel locomotives.
===Steam train===
In 1998, the CPR repatriated one of its former passenger steam locomotives that had been on static display in the United States following its sale in January 1964, long after the close of the steam era. CPR Hudson 2816 was re-designated Empress 2816 following a 30-month restoration that cost in excess of $1 million. It was subsequently returned to service to promote public relations. It has operated across much of the CPR system, including lines in the U.S. and been used for various charitable purposes; 100% of the money raised goes to the nationwide charity Breakfast for Learning — the CPR bears all of the expenses associated with the operation of the train. 2816 is the subject of Rocky Mountain Express, a 2011 IMAX film which follows the locomotive on an eastbound journey beginning in Vancouver, and which tells the story of the building of the CPR. 2816 has been stored indefinitely since 2012 after CEO E. Hunter Harrison discontinued the steam program.
The locomotive was fired up on November 13, 2020, for a steam test and moved around the Ogden campus yard. At the time, CP had plans to utilize the locomotive only for a special Holiday Train at Home broadcast, after which it was put in storage. However, in mid-2021, CEO Keith Creel announced intentions to bring 2816 back to full operational status, for a tour from their Calgary headquarters to Mexico City, if the merger with Kansas City Southern Railway was approved by the Surface Transportation Board in the United States. Work on the needed overhaul began in earnest in late 2021 for a planned date in 2023. On April 24, 2024, No. 2816 began its Final Spike Steam Tour for the Canadian Pacific Kansas City, running from Calgary to Mexico City.
===Spirit Train===
In 2008, Canadian Pacific partnered with the 2010 Olympic and Paralympic Winter Games to present a "Spirit Train" tour that featured Olympic-themed events at various stops. Colin James was a headline entertainer. Several stops were met by protesters who argued that the games were slated to take place on stolen indigenous land.
=== CP Canada 150 Train ===
In 2017, CP ran the CP Canada 150 Train from Port Moody to Ottawa to celebrate Canada's 150th year since Confederation. The train stopped in 13 cities along its 3-week summer tour, offering a free block party and concert from Dean Brody, Kelly Prescott and Dallas Arcand. The heritage train drew out thousands to sign the special "Spirit of Tomorrow" car, where children were invited to write their wishes for the future of Canada and send them to Ottawa. Prime Minister Justin Trudeau and daughter Ella-Grace Trudeau also visited the train and rode it from Revelstoke to Calgary.
==Non-railway services==
Historically, Canadian Pacific operated several non-railway businesses. In 1971, these businesses were split off into the separate company Canadian Pacific Limited, and in 2001, that company was further split into five companies. CP no longer provides any of these services.
===Canadian Pacific Telegraphs===
The original charter of the CPR granted in 1881 provided for the right to create an electric telegraph and telephone service including charging for it. The telephone had barely been invented but telegraph was well established as a means of communicating quickly across great distances. Being allowed to sell this service meant the railway could offset the costs of constructing and maintaining a pole line along its tracks across vast distances for its own purposes which were largely for dispatching trains. It began doing so in 1882 as the separate Telegraph Department. It would go on to provide a link between the cables under the Atlantic and Pacific oceans when they were completed. Before the CPR line, messages to the west could be sent only via the United States.
Paid for by the word, the telegram was an expensive way to send messages, but they were vital to businesses. An individual receiving a personal telegram was seen as being someone important except for those that transmitted sorrow in the form of death notices. Messengers on bicycles delivered telegrams and picked up a reply in cities. In smaller locations, the local railway station agent would handle this on a commission basis. To speed things, at the local end messages would first be telephoned. In 1931, it became the Communications Department in recognition of the expanding services provided which included telephones lines, news wire, ticker quotations for capital stocks and eventually teleprinters. All were faster than mail and very important to business and the public alike for many decades before mobile phones and computers came along. It was the coming of these newer technologies especially cellular telephones that eventually resulted in the demise of these services even after formation in 1967 of CN-CP Telecommunications in an effort to effect efficiencies through consolidation rather than competition. Deregulation in the 1980s, brought about mergers and the sale of remaining services and facilities.
===Canadian Pacific Radio===
On January 17, 1930, the CPR applied for licences to operate radio stations in 11 cities from coast-to-coast for the purpose of organising its own radio network in order to compete with the CNR Radio service. The CNR had built a radio network with the aim of promoting itself as well as entertaining its passengers during their travels. The onset of the Great Depression hurt the CPR's financial plan for a rival project and in April they withdrew their applications for stations in all but Toronto, Montreal and Winnipeg. CPR did not end up pursuing these applications but instead operated a phantom station in Toronto known as "CPRY," with initials standing for "Canadian Pacific Royal York" which operated out of studios at CP's Royal York Hotel and leased time on CFRB and CKGW. A network of affiliates carried the CPR radio network's broadcasts in the first half of the 1930s, but the takeover of CNR's Radio service by the new Canadian Radio Broadcasting Commission removed CPR's need to have a network for competitive reasons and CPR's radio service was discontinued in 1935.
CPR programming included a series of concert broadcasts from Montreal with an orchestra conducted by Douglas Clarke and a series called Concert Orchestra broadcast from the Royal York Hotel featuring conductor Rex Battle, and another series of concerts, this time sponsored by Imperial Oil and featuring conductor Reginald Stewart with a 55-piece orchestra and some of the leading soloists of the day, also performing at the Royal York.
===Canadian Pacific Steamships===
Steamships played an important part in the history of CP from the very earliest days. During construction of the line in British Columbia even before the private CPR took over from the government contractor, ships were used to bring supplies to the construction sites. Similarly, to reach the isolated area of Superior in northern Ontario ships were used to bring in supplies to the construction work. While this work was going on there was already regular passenger service to the West. Trains operated from Toronto to Owen Sound where CPR steamships connected to Fort William where trains once again operated to reach Winnipeg. Before the CPR was completed the only way to reach the West was through the United States via St. Paul and Winnipeg. This Great Lakes steam ship service continued as an alternative route for many years and was always operated by the railway. Canadian Pacific passenger service on the lakes ended in 1965.
Once the railway was completed to British Columbia, the CPR chartered and soon bought their own passenger steamships as a link to the Orient. These sleek steamships were of the latest design and christened with "Empress" names (e. g., RMS Empress of Britain, Empress of Canada, Empress of Australia, and so forth). Travel to and from the Orient and cargo, especially imported tea and silk, were an important source of revenue, aided by Royal Mail contracts. This was an important part of the All-Red Route linking the various parts of the British Empire.
The other ocean part was the Atlantic service to and from the United Kingdom, which began with acquisition of two existing lines, Beaver Line, owned by Elder Dempster and Allan Lines. These two segments became Canadian Pacific Ocean Services (later, Canadian Pacific Steamships) and operated separately from the various lake services operated in Canada, which were considered to be a direct part of the railway's operations. These trans-ocean routes made it possible to travel from Britain to Hong Kong using only the CPR's ships, trains and hotels. CP's 'Empress' ships became world-famous for their luxury and speed. They had a practical role, too, in transporting immigrants from much of Europe to Canada, especially to populate the vast prairies. They also played an important role in both world wars with many of them being lost to enemy action, including Empress of Britain.
There were also a number of rail ferries operated over the years as well including, between Windsor, Ontario, and Detroit from 1890 until 1915. This began with two paddle-wheelers capable of carrying 16 cars. Passenger cars were carried as well as freight. This service ended in 1915 when the CPR made an agreement with the Michigan Central to use their Detroit River tunnel opened in 1910. Pennsylvania-Ontario Transportation Company was formed jointly with the PRR in 1906 to operate a ferry across Lake Erie between Ashtabula, Ohio, and Port Burwell, Ontario, to carry freight cars, mostly of coal, much of it to be burned in CPR steam locomotives. Only one ferry boat was ever operated, Ashtabula, a large vessel which eventually sank in a harbour collision in Ashtabula on September 18, 1958, thus ending the service.
====British Columbia Coast Steamships====
The Canadian Pacific Railway Coast Service (British Columbia Coast Steamships or BCCS) was established when the CPR acquired in 1901 Canadian Pacific Navigation Company (no relation) and its large fleet of ships that served 72 ports along the coast of British Columbia including on Vancouver Island. Service included the Vancouver-Victoria-Seattle Triangle Route, Gulf Islands, Powell River, as well as Vancouver-Alaska service. BCCS operated a fleet of 14 passenger ships made up of a number of Princess ships, pocket versions of the famous oceangoing Empress ships along with a freighter, three tugs and five railway car barges. Popular with tourists, the Princess ships were famous in their own right especially Princess Marguerite (II) which operated from 1949 until 1985 and was the last coastal liner in operation. The most notorious of the princess ships, however, is Princess Sophia, which sank with no survivors after striking the Vanderbilt Reef in Alaska's Lynn Canal, constituting the largest maritime disaster in the history of the Pacific Northwest. These services continued for many years until changing conditions in the late 1950s brought about their decline and eventual demise at the end of season in 1974. Princess Marguerite was acquired by the province's British Columbia Steamship (1975) Ltd. and continued to operate for a number of years. In 1977 although BCCSS was the legal name, it was rebranded as Coastal Marine Operations (CMO). By 1998 the company was bought by the Washington Marine Group which after purchase was renamed Seaspan Coastal Intermodal Company and then subsequently rebranded in 2011 as Seaspan Ferries Corporation. Passenger service ended in 1981.
====British Columbia Lake and River Service====
The Canadian Pacific Railway Lake and River Service (British Columbia Lake and River Service) developed slowly and in spurts of growth. CP began a long history of service in the Kootenays region of southern British Columbia beginning with the purchase in 1897 of the Columbia and Kootenay Steam Navigation Company which operated a fleet of steamers and barges on the Arrow Lakes and was merged into the CPR as the CPR Lake and River Service which also served the Arrow Lakes and Columbia River, Kootenay Lake and Kootenai River, Lake Okanagan and Skaha Lake, Slocan Lake, Trout Lake, and Shuswap Lake and the Thompson River/Kamloops Lake.
===Canadian Pacific Hotels===
To promote tourism and passenger ridership the Canadian Pacific established a series of first class hotels. These hotels became landmarks famous in their own right. They include the Algonquin in St. Andrews, Château Frontenac in Quebec, Royal York in Toronto, Minaki Lodge in Minaki Ontario, Hotel Vancouver, Empress Hotel in Victoria and the Banff Springs Hotel and Chateau Lake Louise in the Canadian Rockies. Several signature hotels were acquired from its competitor Canadian National during the 1980s, including the Jasper Park Lodge. The hotels retain their Canadian Pacific heritage, but are no longer operated by the railway. In 1998, Canadian Pacific Hotels acquired Fairmont Hotels, an American company, becoming Fairmont Hotels and Resorts; the combined corporation operated the historic Canadian properties as well as the Fairmont's U.S. properties until merged with Raffles Hotels and Resorts and Swissôtel in 2006.
===Canadian Pacific Air Lines===
Canadian Pacific Airlines, also called CP Air, operated from 1942 to 1987 and was the main competitor of Canadian government-owned Air Canada. Based at Vancouver International Airport, it served Canadian and international routes until it was purchased by Pacific Western Airlines which merged PWA and CP Air to create Canadian Airlines.
==Locomotives==
===Steam locomotives===
In the CPR's early years, it made extensive use of American-type 4-4-0 steam locomotives, and such examples of this are the Countess of Dufferin or No. 29. Later, considerable use was also made of the 4-6-0 type for passenger and 2-8-0 type for freight. Starting in the 20th century, the CPR bought and built hundreds of Ten-Wheeler-type 4-6-0s for passenger and freight service and similar quantities of 2-8-0s and 2-10-2s for freight. 2-10-2s were also used in passenger service on mountain routes. The CPR bought hundreds of 4-6-2 Pacifics between 1906 and 1948 with later versions being true dual-purpose passenger and fast-freight locomotives.
The CPR built hundreds of its own locomotives at its shops in Montreal, first at the "New Shops", as the DeLorimer shops were commonly referred to, and at the massive Angus Shops that replaced them in 1904. Some of the CPR's best-known locomotives were the 4-6-4 Hudsons. First built in 1929, they began a new era of modern locomotives with capabilities that changed how transcontinental passenger trains ran, eliminating frequent changes en route. The 2800s, as the Hudson type was known, ran from Toronto to Fort William, a distance of , while another lengthy engine district was from Winnipeg to Calgary .
Especially notable were the semi-streamlined H1 class Royal Hudsons, locomotives that were given their name because one of their class hauled the royal train carrying King George VI and Queen Elizabeth on the 1939 royal tour across Canada without change or failure. That locomotive, No. 2850, is preserved in the Exporail exhibit hall of the Canadian Railway Museum in Saint-Constant, Quebec. One of the class, No. 2860, was restored by the British Columbia government and used in excursion service on the British Columbia Railway between 1974 and 1999.
The CPR also made many of their older 2-8-0s, built in the turn of the century, into 2-8-2s.
In 1929, the CPR received its first 2-10-4 Selkirk locomotives, the largest steam locomotives to run in Canada and the British Empire. Named after the Selkirk Mountains where they served, these locomotives were well suited for steep grades. They were regularly used in passenger and freight service. The CPR would own 37 of these locomotives, including number 8000, an experimental high pressure engine. The last steam locomotives that the CPR received, in 1949, were Selkirks, numbered 5930–5935.
===Diesel locomotives===
In 1937, the CPR acquired its first diesel-electric locomotive, a custom-built one-of-a-kind switcher numbered 7000. This locomotive was not successful and was not repeated. Production-model diesels were imported from American Locomotive Company (Alco) starting with five model S-2 yard switchers in 1943 and followed by further orders. In 1949, operations on lines in Vermont were dieselized with Alco FA1 road locomotives (eight A and four B units), five ALCO RS-2 road switchers, three Alco S-2 switchers and three EMD E8 passenger locomotives. In 1948 Montreal Locomotive Works began production of ALCO designs.
In 1949, the CPR acquired 13 Baldwin-designed locomotives from the Canadian Locomotive Company for its isolated Esquimalt and Nanaimo Railway and Vancouver Island was quickly dieselized. Following that successful experiment, the CPR started to dieselize its main network. Dieselization was completed 11 years later, with its last steam locomotive running on 6 November 1960. The CPR's first-generation locomotives were mostly made by General Motors Diesel and Montreal Locomotive Works (American Locomotive Company designs), with some made by the Canadian Locomotive Company to Baldwin and Fairbanks Morse designs.
CP was the first railway in North America to pioneer alternating current (AC) traction diesel-electric locomotives in 1984. In 1995, CP turned to GE Transportation for the first production AC traction locomotives in Canada, and now has the highest percentage of AC locomotives in service of all North American Class I railways.
On September 16, 2019, Progress Rail rolled out two SD70ACU rebuilds in Canadian Pacific heritage paint schemes; 7010 wears a Tuscan red and grey paint scheme with script writing, and the 7015 wears a similar paint scheme with block lettering.
On November 11, 2019, five SD70ACU units with commemorative military themes were unveiled during CPR's Remembrance Day ceremony. These units are numbered 7020–7023, with 7024 being renumbered to 6644 to commemorate the date of D-Day: June 6, 1944.
In 2021, Canadian Pacific repainted two locomotives orange: ES44AC 8757 which was unveiled for National Day for Truth and Reconciliation in September 2021, and ES44AC 8781 to commemorate shipper Hapag-Lloyd.
The fleet includes these types:
====Final diesel roster====
====Retired diesel roster====
==Corporate structure==
Canadian Pacific Railway Limited ( ) is a Canadian railway transportation company that operates the Canadian Pacific Railway. It was created in 2001 when the CPR's former parent company, Canadian Pacific Limited, spun off its railway operations. On October 3, 2001, the company's shares began to trade on the New York Stock Exchange and the Toronto Stock Exchange under the "CP" symbol. During 2003, the company earned in freight revenue. In October 2008, Canadian Pacific Railway Ltd was named one of "Canada's Top 100 Employers" by Mediacorp Canada Inc., and was featured in Maclean's. Later that month, CPR was named one of Alberta's Top Employers, which was reported in both the Calgary Herald and the Edmonton Journal.
===Presidents===
==Major facilities==
Canadian Pacific owned a large number of large yards and repair shops across their system, which were used for many operations ranging from intermodal terminals to classification yards. Below are some examples of these.
===Hump yards===
Hump yards work by using a small hill over which cars are pushed, before being released down a slope and switched automatically into cuts of cars, ready to be made into outbound trains. Many of these yards were closed in 2012 and 2013 under Hunter Harrison's company-wide restructuring; only the St. Paul Yard hump remains open.
Calgary, Alberta – Alyth Yard; handles 2,200 cars daily (closed)
Franklin Park, Illinois – Bensenville Yard (closed)
Montreal, Quebec – St. Luc Yard; active since 1950. Flat switching since the mid-1980s. (closed)
St. Paul, Minnesota – Pig's Eye Yard / St. Paul Yard
Toronto, Ontario – Toronto Yard (also known as "Toronto Freight Yard or Agincourt Yard") (closed)
Winnipeg, Manitoba – Rugby Yard (also known as "Weston Yard") (closed)
==Aircraft==
As of February 2023, Transport Canada lists the following aircraft in its database and operate as ICAO airline designator CRR, and telephony RAILCAR.
1 - Cessna Citation Sovereign (Cessna 680)
1 - Bombardier CL-600
==Joint partnership==
Toronto Terminal Railways – management team for Toronto's Union Station with Canadian National Railway.
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"nylon",
"teleprinter",
"American Locomotive Company",
"Thompson River",
"Kootenay Lake",
"4-8-4",
"Dean Brody",
"Greater Sudbury",
"Canadian social credit movement",
"steam locomotive",
"Royal Hudson",
"Hugh Ryan (railway magnate)",
"London",
"Sam Roberts Band",
"FM H-24-66",
"District of Assiniboia",
"Henry Worth Thornton",
"Canadian Pacific Building (New York City)",
"CFRB",
"Vanderbilt Reef",
"colonization",
"British Columbia Coast Steamships",
"Cooperative Commonwealth Federation",
"Canadian Pacific Railway Upper Lake Service",
"Dalhousie Station (Montreal)",
"1910 Rogers Pass avalanche",
"Dakota, Minnesota and Eastern Railroad",
"Railway Gazette International",
"Progress Rail",
"Air Canada",
"grain trade",
"Bombardier Challenger 600 series",
"Wisconsin Central Ltd.",
"Fraser River",
"Calgary",
"Last Spike (Canadian Pacific Railway)",
"Milwaukee",
"British Empire",
"explosive material",
"Fortress Transportation and Infrastructure Investors",
"Field, British Columbia",
"Skaha Lake",
"EMD GP35",
"Franklin Park, Illinois",
"Vermont",
"share capital",
"British Columbia",
"Kansas City Southern Railway",
"Richard White (historian)",
"TransLink (Vancouver)",
"Château Frontenac",
"Canadian Pacific Kansas City",
"EMD SD60",
"ALCO S-2 and S-4",
"Agence métropolitaine de transport",
"Steamboat",
"RMS Empress of Canada (1920)",
"Penticton",
"Lethbridge, Alberta",
"William Van Horne",
"Sir William Cornelius Van Horne",
"stock ticker machine",
"Semi-trailer truck",
"Windsor, Ontario",
"Odds (band)",
"Hazel McCallion",
"Vaudreuil-Hudson Line",
"CPR Alyth Yard",
"Nashotah, Wisconsin",
"EMD F9",
"Campbellville, Ontario",
"Digby, Nova Scotia",
"Quebec Central",
"CP Ships",
"Chateau Lake Louise",
"News agency",
"Canada's Top 100 Employers",
"Thunder Bay",
"Ashtabula (ferry)",
"EMD GP7",
"New York City",
"Alberta",
"Gulf of St. Lawrence",
"EMD SD70ACU",
"Oldman River",
"Edward Wentworth Beatty",
"Saint-Constant, Quebec",
"Public company",
"Prescott, Ontario",
"Teamsters Canada",
"passenger train",
"Imperial Oil",
"Valentine tank",
"EMD SD90MAC",
"Cambridge, Ontario",
"4-6-2",
"Ottawa Valley",
"Lucien-L'Allier (AMT)",
"GE Transportation",
"Funeral train",
"Crowsnest Pass",
"Alexander Tilloch Galt",
"The Fifth Estate (TV program)",
"Saskatchewan",
"Hapag-Lloyd",
"FM H-16-44",
"Deregulation",
"railbuff",
"Alberta's Top Employers",
"Minaki Lodge",
"passenger car (rail)",
"EMD GP38AC",
"On-to-Ottawa Trek",
"Sturtevant, Wisconsin",
"boat train",
"Reginald Stewart (conductor)",
"ALCO FA",
"Vancouver Island",
"2-10-4",
"Lac-Mégantic derailment",
"Field Hill",
"Montreal, Maine and Atlantic Railway",
"Bilevel car",
"Detroit",
"2-10-2",
"Trout Lake (British Columbia)",
"Ontario and Quebec Railway",
"Palliser's Triangle",
"Milton, Ontario",
"Orient",
"MLW RS-18",
"Ottawa",
"Delaware and Hudson Railway",
"List of subsidiary railways of the Canadian Pacific Railway",
"Sault Ste. Marie, Ontario",
"ALCO S-1 and S-3",
"National Day for Truth and Reconciliation",
"Great Northern Railway (U.S.)",
"Thunder Bay, Ontario",
"Ashtabula, Ohio",
"binding agreement",
"Société de transport de Montréal",
"Canadian Pacific Building (Toronto)",
"chairman",
"Milwaukee District/North Line",
"CBLA",
"ALCO RS-3",
"Lynn Canal",
"William W. Stinson",
"ALCO Century 424",
"Iowa, Chicago and Eastern Railroad",
"streamliner",
"Coquihalla Pass",
"Kicking Horse Pass",
"Saint-Jérôme line",
"Canadian Pacific 29",
"ALCO Century 636",
"John A. Macdonald",
"Queen Elizabeth The Queen Mother",
"4-4-0",
"sea ice",
"Train ferry",
"Hope, British Columbia",
"Canada Central Railway",
"North Vancouver (city)",
"Kaslo and Slocan Railway",
"Perth, Ontario",
"Connaught Tunnel (British Columbia)",
"silk mill",
"Canadians",
"Yellowhead Pass",
"avalanche",
"Budd Rail Diesel Car",
"CPR Lake and River Service",
"Saint John, New Brunswick",
"New Jersey",
"Conrail",
"British Columbia Railway",
"The Empress (Hotel)",
"Colonist car",
"Pacific Western Airlines",
"World Fuel Services",
"phantom station",
"The Trews",
"Spanish River (Ontario)",
"EMD GP20C-ECO",
"Kettle Valley Railway",
"Brian Mulroney",
"Banff Springs Hotel",
"Stoney Nakoda First Nation",
"Wagner Palace Car Company",
"Europe",
"raw silk",
"2010 Winter Olympics",
"freight",
"Bonfield, Ontario",
"Saint Paul, Minnesota",
"Quebec, Montreal, Ottawa & Occidental Railway",
"orchestra",
"William Cornelius Van Horne",
"Canadian Pacific 2816",
"Monarchy of Canada",
"Remembrance Day",
"airplane",
"Canadian American Railroad",
"Selkirk locomotive",
"Railpower GG20B",
"Jackfish, Ontario",
"Electra Private Equity",
"MLW RS-10",
"Vancouver",
"diesel locomotives",
"Mount Macdonald Tunnel",
"Kingston, Ontario",
"CEO",
"History of Chinese immigration to Canada",
"EMD SD30C-ECO",
"4-6-0",
"alternating current",
"Lethbridge",
"food bank",
"United States",
"Trains (magazine)",
"RMS Empress of Britain (1905)",
"ES44AC",
"Kennecott Utah Copper",
"4-8-2",
"Bombardier Transportation",
"Canadian Locomotive Company",
"International Railway of Maine",
"Eastern Ontario",
"North-West Rebellion",
"Hudson's Bay Company",
"EMD SD40",
"Rogers Pass (British Columbia)",
"Western Grain Transportation Act",
"Robert J. Ritchie (railroad executive)",
"EMD SW900",
"Lake Erie",
"Mount Macdonald",
"Toronto Stock Exchange",
"sulphur",
"CPR Angus Shops",
"CPR Toronto Yard",
"Maclean's",
"Minneapolis–St. Paul",
"Buck Crump",
"George Stephen, 1st Baron Mount Stephen",
"Naramata",
"Royal Canadian Pacific",
"the Algonquin",
"Steamboats of the Arrow Lakes",
"Victoria, British Columbia",
"GO Transit",
"The Dominion (train)",
"Canadian Pacific 283",
"navvy",
"Calgary Herald",
"economic development",
"E. Hunter Harrison",
"Minneapolis, St. Paul and Sault Ste. Marie Railroad",
"crude oil",
"ALCO Century 630",
"unit train",
"Conrail Shared Assets Operations",
"Canadian Pacific Hotels",
"RCMP",
"Sparwood, British Columbia",
"Chicago",
"1939 royal tour of Canada",
"Rocky Mountain Express",
"Ogdensburg, New York",
"president (corporate title)",
"Andrew Onderdonk",
"Lethbridge Viaduct",
"Sir John A. Macdonald",
"Sleeping car",
"Alexander Mackenzie (politician)",
"Cascade Mountains",
"Cessna Citation Sovereign",
"CNR Radio",
"Donald Smith, 1st Baron Strathcona and Mount Royal",
"Soo Line Railroad",
"Minneapolis, Northfield and Southern Railway",
"London, Ontario",
"Multimark",
"prairie",
"Employee stock ownership",
"British Columbia Lake and River Service",
"Columbia and Western Railway",
"IMAX",
"Minneapolis",
"CSX",
"St. Andrews, New Brunswick",
"Granville, British Columbia",
"Hotel Vancouver",
"Canada-U.S. Free Trade Agreement",
"Thomas George Shaughnessy, 1st Baron Shaughnessy",
"Silver Streak (film)",
"Colin James",
"The Dominion (passenger train)",
"Canadian Pacific Air Lines Flight 402",
"Crown corporation",
"TTX Company",
"District of Saskatchewan",
"Shuswap and Okanagan Railway",
"Iron Road Railways",
"Toronto, Hamilton and Buffalo Railway",
"Crow Rate",
"Canadian National Railway",
"GE AC4400CWM",
"Historica Canada",
"Port Moody",
"Metra",
"Montreal",
"1979 Mississauga train derailment",
"Spanish River derailment",
"Winnipeg",
"Nairn, Ontario",
"Bolton, Ontario",
"Nova Scotia",
"Milwaukee Road",
"Norfolk Southern",
"Quebec City",
"Canadian Confederation",
"EMD GP39-2",
"GE Evolution Series",
"Central Maine and Quebec Railway",
"Port Arthur, Ontario",
"Canadian Pacific Railway Lake and River Service",
"Liberal Party of Canada",
"beaver",
"Toronto",
"Transportation Safety Board of Canada",
"Western Hemisphere",
"Arrow Lakes",
"RMS Empress of Australia (1919)",
"CNCP Telecommunications",
"Port Burwell, Ontario",
"coolies",
"The Canadian",
"Canadian National Railways",
"Northern Pacific Railway Company",
"Vancouver International Airport",
"Kent, British Columbia",
"Ian David Sinclair",
"Delson-Candiac Line (AMT)",
"General Motors Diesel",
"Baldwin DS-4-4-1000",
"EMD SW8",
"Contiguous United States",
"Classification yard",
"MLW RS-23",
"ALCO RS-2",
"Angus Shops",
"Albany, New York",
"Lake Okanagan",
"Rail transport",
"Conservative Party of Canada (historical)",
"Kamloops Lake",
"EMD F7",
"Columbia and Kootenay Railway",
"Bay of Fundy",
"Sicamous (sternwheeler)",
"Canadian Radio Broadcasting Commission",
"CPR Festivals",
"Canadian Pacific Air Lines Flight 21",
"intermodal freight transport",
"Canadian Pacific Railway Coast Service",
"Edmonton",
"electric telegraph",
"Super Continental",
"Vermilion Bay, Ontario",
"Canadian Pacific Navigation Company",
"EMD SD40-2",
"Baldwin DRS-4-4-1000",
"Canadian Pacific Limited",
"Milwaukee District/West Line",
"Canadian Railway Museum",
"Southern Railway of Vancouver Island",
"Calgary, Alberta",
"Nicholas Morant",
"Baron Strathcona and Mount Royal",
"Baldwin Locomotive Works",
"Terri Clark",
"CPKC",
"ALCO RSD-15",
"West Coast Express",
"EMD SD40-2F",
"Princess Sophia (steamer)",
"Steamboats of Lake Okanagan",
"Union Station (Toronto)",
"transcontinental railroad",
"Hammond, Indiana",
"Fort William, Ontario",
"Countess of Dufferin",
"GE AC4400CW",
"Willy Porter",
"Edmonton Journal",
"Columbia Valley",
"Roberts Bank Superport",
"Fairbanks Morse",
"Surface Transportation Board",
"Rocky Mountain Trench",
"North Saskatchewan River",
"EMD GP30",
"classification yard",
"Rocky Mountains",
"FM Consolidated line",
"Chesterton, Indiana",
"St. Lawrence and Hudson Railway",
"Elgin County Railway Museum",
"EMD FP7",
"Airline codes",
"Hamilton, Ontario",
"Class I railway",
"diesel-electric locomotive",
"Cottage Grove, Minnesota",
"Montreal Locomotive Works",
"Moyie (sternwheeler)",
"Glacier National Park (Canada)",
"EMD E8",
"Pacific Scandal",
"mobile phone",
"EMD GP9",
"George VI",
"University of Saskatchewan",
"Tuscan red",
"Mexico City"
] |
5,961 |
Cognitive psychology
|
Cognitive psychology is the scientific study of human mental processes such as attention, language use, memory, perception, problem solving, creativity, and reasoning.
Cognitive psychology originated in the 1960s in a break from behaviorism, which held from the 1920s to 1950s that unobservable mental processes were outside the realm of empirical science. This break came as researchers in linguistics and cybernetics, as well as applied psychology, used models of mental processing to explain human behavior.
Work derived from cognitive psychology was integrated into other branches of psychology and various other modern disciplines like cognitive science, linguistics, and economics.
==History==
Philosophically, ruminations on the human mind and its processes have been around since the times of the ancient Greeks. In 387 BCE, Plato had suggested that the brain was the seat of the mental processes. In 1637, René Descartes posited that humans are born with innate ideas and forwarded the idea of mind-body dualism, which would come to be known as substance dualism (essentially the idea that the mind and the body are two separate substances). From that time, major debates ensued through the 19th century regarding whether human thought was solely experiential (empiricism), or included innate knowledge (nativism). Some of those involved in this debate included George Berkeley and John Locke on the side of empiricism, and Immanuel Kant on the side of nativism.
With the philosophical debate continuing, the mid to late 19th century was a critical time in the development of psychology as a scientific discipline. Two discoveries that would later play substantial roles in cognitive psychology were Paul Broca's discovery of the area of the brain largely responsible for language production, Both areas were subsequently formally named for their founders, and disruptions of an individual's language production or comprehension due to trauma or malformation in these areas have come to commonly be known as Broca's aphasia and Wernicke's aphasia.
From the 1920s to the 1950s, the main approach to psychology was behaviorism. Initially, its adherents viewed mental events such as thoughts, ideas, attention, and consciousness as unobservable, hence outside the realm of a science of psychology. One early pioneer of cognitive psychology, whose work predated much of behaviorist literature, was Carl Jung. Jung introduced the hypothesis of cognitive functions in his 1921 book Psychological Types. Another pioneer of cognitive psychology, who worked outside the boundaries (both intellectual and geographical) of behaviorism, was Jean Piaget. From 1926 to the 1950s and into the 1980s, he studied the thoughts, language, and intelligence of children and adults.
In the mid-20th century, four main influences arose that would inspire and shape cognitive psychology as a formal school of thought:
With the development of new warfare technology during WWII, the need for a greater understanding of human performance came to prominence. Problems such as how to best train soldiers to use new technology and how to deal with matters of attention while under duress became areas of need for military personnel. Behaviorism provided little if any insight into these matters and it was the work of Donald Broadbent, integrating concepts from human performance research and the recently developed information theory, that forged the way in this area. of behaviorism, and empiricism more generally, initiated what would come to be known as the "cognitive revolution". Inside psychology, in criticism of behaviorism, J. S. Bruner, J. J. Goodnow & G. A. Austin wrote "a study of thinking" in 1956. In 1960, G. A. Miller, E. Galanter and K. Pribram wrote their famous "Plans and the Structure of Behavior". The same year, Bruner and Miller founded the Harvard Center for Cognitive Studies, which institutionalized the revolution and launched the field of cognitive science.
Formal recognition of the field involved the establishment of research institutions such as George Mandler's Center for Human Information Processing in 1964. Mandler described the origins of cognitive psychology in a 2002 article in the Journal of the History of the Behavioral Sciences.
Ulric Neisser put the term "cognitive psychology" into common use through his book Cognitive Psychology, published in 1967. Neisser's definition of "cognition" illustrates the then-progressive concept of cognitive processes:
The term "cognition" refers to all processes by which the sensory input is transformed, reduced, elaborated, stored, recovered, and used. It is concerned with these processes even when they operate in the absence of relevant stimulation, as in images and hallucinations. ... Given such a sweeping definition, it is apparent that cognition is involved in everything a human being might possibly do; that every psychological phenomenon is a cognitive phenomenon. But although cognitive psychology is concerned with all human activity rather than some fraction of it, the concern is from a particular point of view. Other viewpoints are equally legitimate and necessary. Dynamic psychology, which begins with motives rather than with sensory input, is a case in point. Instead of asking how a man's actions and experiences result from what he saw, remembered, or believed, the dynamic psychologist asks how they follow from the subject's goals, needs, or instincts. A key function of attention is to identify irrelevant data and filter it out, enabling significant data to be distributed to the other mental processes. Exogenous control works in a bottom-up manner and is responsible for orienting reflex, and pop-out effects. However, while deep processing does not occur, early sensory processing does. Subjects did notice if the pitch of the unattended message changed or if it ceased altogether, and some even oriented to the unattended message if their name was mentioned.
====Working memory====
Though working memory is often thought of as just short-term memory, it is more clearly defined as the ability to process and maintain temporary information in a wide range of everyday activities in the face of distraction. The famously known capacity of memory of 7 plus or minus 2 is a combination of both memories in working memory and long-term memory.
One of the classic experiments is by Ebbinghaus, who found the serial position effect where information from the beginning and end of the list of random words were better recalled than those in the center. This primacy and recency effect varies in intensity based on list length.
Procedural memory is memory for the performance of particular types of action. It is often activated on a subconscious level, or at most requires a minimal amount of conscious effort. Procedural memory includes stimulus-response-type information, which is activated through association with particular tasks, routines, etc. A person is using procedural knowledge when they seemingly "automatically" respond in a particular manner to a particular situation or process. Early psychologists like Edward B. Titchener began to work with perception in their structuralist approach to psychology. Structuralism dealt heavily with trying to reduce human thought (or "consciousness", as Titchener would have called it) into its most basic elements by gaining an understanding of how an individual perceives particular stimuli.
Current perspectives on perception within cognitive psychology tend to focus on particular ways in which the human mind interprets stimuli from the senses and how these interpretations affect behavior. An example of the way in which modern psychologists approach the study of perception is the research being done at the Center for Ecological Study of Perception and Action at the University of Connecticut (CESPA). One study at CESPA concerns ways in which individuals perceive their physical environment and how that influences their navigation through that environment.
===Language===
Psychologists have had an interest in the cognitive processes involved with language that dates back to the 1870s, when Carl Wernicke proposed a model for the mental processing of language. Current work on language within the field of cognitive psychology varies widely. Cognitive psychologists may study language acquisition, individual components of language formation (like phonemes), how language use is involved in mood, or numerous other related areas.
Significant work has focused on understanding the timing of language acquisition and how it can be used to determine if a child has, or is at risk of, developing a learning disability. A study from 2012 showed that, while this can be an effective strategy, it is important that those making evaluations include all relevant information when making their assessments. Factors such as individual variability, socioeconomic status, short-term and long-term memory capacity, and others must be included in order to make valid assessments.
Much of the current study regarding metacognition within the field of cognitive psychology deals with its application within the area of education. Being able to increase a student's metacognitive abilities has been shown to have a significant impact on their learning and study habits. One key aspect of this concept is the improvement of students' ability to set goals and self-regulate effectively to meet those goals. As a part of this process, it is also important to ensure that students are realistically evaluating their personal degree of knowledge and setting realistic goals (another metacognitive task).
Common phenomena related to metacognition include:
Déjà Vu: feeling of a repeated experience.
Cryptomnesia: generating thought believing it is unique but it is actually a memory of a past experience; also known as unconscious plagiarism.
False Fame Effect: non-famous names can be made to be famous.
Validity effect: statements seem more valid upon repeated exposure.
Imagination inflation: imagining an event that did not occur and having increased confidence that it did occur.
==Modern perspectives==
Modern perspectives on cognitive psychology generally address cognition as a dual process theory, expounded upon by Daniel Kahneman in 2011. Kahneman differentiated the two styles of processing more, calling them intuition and reasoning. Intuition (or system 1), similar to associative reasoning, was determined to be fast and automatic, usually with strong emotional bonds included in the reasoning process. Kahneman said that this kind of reasoning was based on formed habits and very difficult to change or manipulate. Reasoning (or system 2) was slower and much more volatile, being subject to conscious judgments and attitudes. His work in the areas of recognition and treatment of depression has gained worldwide recognition. In his 1987 book titled Cognitive Therapy of Depression, Beck puts forth three salient points with regard to his reasoning for the treatment of depression by means of therapy or therapy and antidepressants versus using a pharmacological-only approach:
1. Despite the prevalent use of antidepressants, the fact remains that not all patients respond to them. Beck cites (in 1987) that only 60 to 65% of patients respond to antidepressants, and recent meta-analyses (a statistical breakdown of multiple studies) show very similar numbers.2. Many of those who do respond to antidepressants end up not taking their medications, for various reasons. They may develop side-effects or have some form of personal objection to taking the drugs.3. Beck posits that the use of psychotropic drugs may lead to an eventual breakdown in the individual's coping mechanisms. His theory is that the person essentially becomes reliant on the medication as a means of improving mood and fails to practice those coping techniques typically practiced by healthy individuals to alleviate the effects of depressive symptoms. By failing to do so, once the patient is weaned off of the antidepressants, they often are unable to cope with normal levels of depressed mood and feel driven to reinstate use of the antidepressants.
===Social psychology===
Many facets of modern social psychology have roots in research done within the field of cognitive psychology. Social cognition is a specific sub-set of social psychology that concentrates on processes that have been of particular focus within cognitive psychology, specifically applied to human interactions. Gordon B. Moskowitz defines social cognition as "... the study of the mental processes involved in perceiving, attending to, remembering, thinking about, and making sense of the people in our social world".
The development of multiple social information processing (SIP) models has been influential in studies involving aggressive and anti-social behavior. Kenneth Dodge's SIP model is one of, if not the most, empirically supported models relating to aggression. Among his research, Dodge posits that children who possess a greater ability to process social information more often display higher levels of socially acceptable behavior; that the type of social interaction that children have affects their relationships. His model asserts that there are five steps that an individual proceeds through when evaluating interactions with other individuals and that how the person interprets cues is key to their reactionary process.
===Developmental psychology===
Many of the prominent names in the field of developmental psychology base their understanding of development on cognitive models. One of the major paradigms of developmental psychology, the Theory of Mind (ToM), deals specifically with the ability of an individual to effectively understand and attribute cognition to those around them. This concept typically becomes fully apparent in children between the ages of 4 and 6. Essentially, before the child develops ToM, they are unable to understand that those around them can have different thoughts, ideas, or feelings than themselves. The development of ToM is a matter of metacognition, or thinking about one's thoughts. The child must be able to recognize that they have their own thoughts and in turn, that others possess thoughts of their own.
One of the foremost minds with regard to developmental psychology, Jean Piaget, focused much of his attention on cognitive development from birth through adulthood. Though there have been considerable challenges to parts of his stages of cognitive development, they remain a staple in the realm of education. Piaget's concepts and ideas predated the cognitive revolution but inspired a wealth of research in the field of cognitive psychology and many of his principles have been blended with modern theory to synthesize the predominant views of today.
===Educational psychology===
Modern theories of education have applied many concepts that are focal points of cognitive psychology. Some of the most prominent concepts include:
Metacognition: Metacognition is a broad concept encompassing all manners of one's thoughts and knowledge about their own thinking. A key area of educational focus in this realm is related to self-monitoring, which relates highly to how well students are able to evaluate their personal knowledge and apply strategies to improve knowledge in areas in which they are lacking.
Declarative knowledge and procedural knowledge: Declarative knowledge is a person's 'encyclopedic' knowledge base, whereas procedural knowledge is specific knowledge relating to performing particular tasks. The application of these cognitive paradigms to education attempts to augment a student's ability to integrate declarative knowledge into newly learned procedures in an effort to facilitate accelerated learning.
==Relationship to cognitive science==
Cognitive psychology is considered a core aspect of cognitive science, the interdisciplinary study of mind and mental function, including how such functions implemented in brains and machines. Cognitive science, as a unitary field, integrates knowledge, theory and methodology from psychology, neuroscience, linguistics, philosophy, artificial intelligence, and anthropology.
It has been argued that cognitive science has been largely consumed by cognitive psychology, with some scholars even using the terms interchangeably for an example). This largely results from early difficulties integrating the different fields of cognitive science (e.g. psychology and artificial intelligence), with the resulting divergence of terminology, methodology and theoretical approach over time rendering efforts at cohering the disciplines challenging.
There is however disagreement between neuropsychologists and cognitive psychologists. Cognitive psychology has produced models of cognition which are not supported by modern brain science. It is often the case that the advocates of different cognitive models form a dialectic relationship with one another thus affecting empirical research, with researchers siding with their favorite theory. For example, advocates of mental model theory have attempted to find evidence that deductive reasoning is based on image thinking, while the advocates of mental logic theory have tried to prove that it is based on verbal thinking, leading to a disorderly picture of the findings from brain imaging and brain lesion studies. When theoretical claims are put aside, the evidence shows that interaction depends on the type of task tested, whether of visuospatial or linguistical orientation; but that there is also an aspect of reasoning which is not covered by either theory.
Similarly, neurolinguistics has found that it is easier to make sense of brain imaging studies when the theories are left aside. In the field of language cognition research, generative grammar has taken the position that language resides within its private cognitive module, while 'Cognitive Linguistics' goes to the opposite extreme by claiming that language is not an independent function, but operates on general cognitive capacities such as visual processing and motor skills. Consensus in neuropsychology however takes the middle position that, while language is a specialized function, it overlaps or interacts with visual processing. Nonetheless, much of the research in language cognition continues to be divided along the lines of generative grammar and Cognitive Linguistics; and this, again, affects adjacent research fields including language development and language acquisition.
==Major research areas==
Categorization
Induction and acquisition
Judgement and classification
Representation and structure
Similarity
Knowledge representation
Dual-coding theories
Media psychology
Mental imagery
Numerical cognition
Propositional encoding
Language
Language acquisition
Language processing
Memory
Aging and memory
Autobiographical memory
Childhood memory
Constructive memory
Emotion and memory
Episodic memory
Eyewitness memory
False memories
Flashbulb memory
List of memory biases
Long-term memory
Semantic memory
Short-term memory
Source-monitoring error
Spaced repetition
Working memory
Perception
Attention
Pattern recognition
Visual perception
Form perception
Object recognition
Psychophysics
Time sensation
Thinking
Choice (Glasser's theory)
Concept formation
Decision-making
Logic
Psychology of reasoning
Problem solving
Executive functions
==Influential cognitive psychologists==
John R. Anderson
Alan Baddeley
David Ausubel
Albert Bandura
Frederic Bartlett
Elizabeth Bates
Aaron T. Beck
Robert Bjork
Paul Bloom
Gordon H. Bower
Donald Broadbent
Jerome Bruner
Susan Carey
Noam Chomsky
Fergus Craik
Antonio Damasio
Hermann Ebbinghaus
Albert Ellis
K. Anders Ericsson
William Estes
Eugene Galanter
Vittorio Gallese
Michael Gazzaniga
Dedre Gentner
Vittorio Guidano
Philip Johnson-Laird
Daniel Kahneman
Nancy Kanwisher
Eric Lenneberg
Alan Leslie
Willem Levelt
Elizabeth Loftus
Alexander Luria
Brian MacWhinney
George Mandler
Jean Matter Mandler
Ellen Markman
James McClelland
George Armitage Miller
Ulrich Neisser
Allen Newell
Allan Paivio
Seymour Papert
Jean Piaget
Steven Pinker
Michael Posner
Karl H. Pribram
Giacomo Rizzolatti
Henry L. Roediger III
Eleanor Rosch
David Rumelhart
Eleanor Saffran
Daniel Schacter
Otto Selz
Roger Shepard
Richard Shiffrin
Herbert A. Simon
George Sperling
Robert Sternberg
Larry Squire
Saul Sternberg
Anne Treisman
Endel Tulving
Amos Tversky
Lev Vygotsky
|
[
"dialectic",
"Cognitive neuropsychology",
"Decision-making",
"Susan Carey",
"Herbert A. Simon",
"Vittorio Gallese",
"Fuzzy-trace theory",
"Dualism (philosophy of mind)",
"Neuropsychology",
"Source-monitoring error",
"Paul Bloom (psychologist)",
"James McClelland (psychologist)",
"Psychological adaptation",
"Declarative knowledge",
"Language processing",
"Eleanor Rosch",
"Jerome Bruner",
"mental processes",
"language acquisition",
"Media psychology",
"Cognitive robotics",
"Executive functions",
"Social cognition",
"Allan Paivio",
"George Sperling",
"Cognitive poetics",
"Richard Shiffrin",
"Daniel Kahneman",
"consciousness",
"Psychodynamics",
"Robert Sternberg",
"Flashbulb memory",
"Touch",
"Vittorio Guidano",
"Mental image",
"Aaron T. Beck",
"Endel Tulving",
"innate",
"decay theory",
"Semantic memory",
"Structuralism (psychology)",
"Ancient Greece",
"Autobiographical memory",
"cybernetics",
"Genetic epistemology",
"Theory of Mind",
"phoneme",
"Perceptual control theory",
"Choice",
"information theory",
"Cognitive development",
"Models of abnormality",
"Scholarpedia",
"Frederic Bartlett",
"Immanuel Kant",
"Antonio Damasio",
"Brian MacWhinney",
"Attention",
"Plato",
"Seymour Papert",
"Baddeley's model of working memory",
"cognitive therapy",
"Albert Ellis",
"Donald Broadbent",
"Behaviorism",
"Short-term memory",
"Imagination inflation",
"Albert Bandura",
"Working memory",
"Visual object recognition (animal test)",
"proprioception",
"brain science",
"Metacognition",
"procedural knowledge",
"neurolinguistics",
"Language",
"Knowledge organization",
"interference theory",
"deductive reasoning",
"reason",
"Robert Bjork",
"Philip Johnson-Laird",
"empirical science",
"Computationalism",
"Otto Selz",
"Situated cognition",
"George Mandler",
"K. Anders Ericsson",
"Auditory system",
"Categorization",
"Jean Piaget",
"George Berkeley",
"Jean Matter Mandler",
"Artificial intelligence",
"List of memory biases",
"Psychological nativism",
"artificial intelligence",
"Expressive aphasia",
"Sense of time",
"Knowledge representation",
"cocktail party effect",
"Propositional encoding",
"Dedre Gentner",
"Grammar",
"working memory",
"Alan Baddeley",
"Piaget's theory of cognitive development",
"orienting reflex",
"Water-level task",
"René Descartes",
"olfactory",
"Numerical cognition",
"Cognition",
"Nancy Kanwisher",
"motor skills",
"Personal information management",
"metacognition",
"Glasser's choice theory",
"cognitive capacities",
"brain imaging",
"Concept formation",
"Dual-coding theories",
"Eyewitness memory",
"Neurocognitive",
"Noam Chomsky",
"taste",
"Ecological psychology",
"memory",
"cognitive science",
"Ulric Neisser",
"Roger Shepard",
"Spaced repetition",
"Problem solving",
"Ulrich Neisser",
"Hierarchy",
"language development",
"Psychotropic",
"empiricism",
"Saul Sternberg",
"visual",
"serial position effect",
"Similarity (psychology)",
"cognitive neuroscience",
"Constructive memory",
"Cryptomnesia",
"Procedural memory",
"hallucinations",
"Giacomo Rizzolatti",
"Elizabeth Loftus",
"perception",
"Mood (psychology)",
"Willem Levelt",
"The Magical Number Seven, Plus or Minus Two",
"mental process",
"conscious",
"John Robert Anderson (psychologist)",
"Aging and memory",
"semantic memory",
"socioeconomic status",
"Linguistics",
"Elizabeth Bates",
"Concept learning",
"Phonetics",
"linguistics",
"Meta-analysis",
"Thinking",
"dual process theory",
"Visual thinking",
"Form perception",
"Psychophysics",
"Cognitive style",
"Rubicon model (psychology)",
"illusory truth effect",
"World War II",
"Allen Newell",
"Déjà Vu",
"Language acquisition",
"Connectionism",
"social information processing (theory)",
"Coping (psychology)",
"Childhood memory",
"George Armitage Miller",
"Von Restorff effect",
"Information processing (psychology)",
"Psychology of reasoning",
"Cognitive interventions",
"Eric Lenneberg",
"Intertrial priming",
"generative grammar",
"Visual perception",
"Henry L. Roediger III",
"Gordon Moskowitz",
"Karl H. Pribram",
"Memory",
"brain lesion",
"visual processing",
"Lev Vygotsky",
"language",
"Cognitive module",
"Paul Broca",
"Ellen Markman",
"realm",
"Michael Gazzaniga",
"Larry Squire",
"Daniel Schacter",
"Psychological Types",
"Cognitive biology",
"creativity",
"Jungian cognitive functions",
"Perception",
"learning disability",
"Long-term memory",
"Phonology",
"Logic",
"Alan Leslie",
"Evolutionary psychology",
"Receptive aphasia",
"Carl Jung",
"Anne Treisman",
"David Ausubel",
"Amos Tversky",
"behaviorism",
"Steven Pinker",
"Cognitive description",
"Michael Posner (psychologist)",
"Pattern recognition",
"Eleanor Saffran",
"long-term memory",
"Gordon H. Bower",
"Naturalistic decision-making",
"Discursive psychology",
"cognitive revolution",
"economics",
"Cognitive linguistics",
"Episodic memory",
"Stimulus-response model",
"David Rumelhart",
"William Kaye Estes",
"Cognitivism (psychology)",
"cognitive module",
"Cognitive bias",
"Hermann Ebbinghaus",
"applied psychology",
"Eugene Galanter",
"cognitive behavior therapy",
"John Locke",
"subconscious",
"Emotion and memory",
"Alexander Luria",
"False memories",
"attention",
"Verbal reasoning",
"Behavioral Sciences",
"Eiffel Tower",
"Carl Wernicke",
"Edward Titchener",
"Fergus Craik"
] |
5,962 |
Comet
|
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and sometimes a tail of gas and dust gas blown out from the coma. These phenomena are due to the effects of solar radiation and the outstreaming solar wind plasma acting upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust, and small rocky particles. The coma may be up to 15 times Earth's diameter, while the tail may stretch beyond one astronomical unit. If sufficiently close and bright, a comet may be seen from Earth without the aid of a telescope and can subtend an arc of up to 30° (60 Moons) across the sky. Comets have been observed and recorded since ancient times by many cultures and religions.
Comets usually have highly eccentric elliptical orbits, and they have a wide range of orbital periods, ranging from several years to potentially several millions of years. Short-period comets originate in the Kuiper belt or its associated scattered disc, which lie beyond the orbit of Neptune. Long-period comets are thought to originate in the Oort cloud, a spherical cloud of icy bodies extending from outside the Kuiper belt to halfway to the nearest star. Long-period comets are set in motion towards the Sun by gravitational perturbations from passing stars and the galactic tide. Hyperbolic comets may pass once through the inner Solar System before being flung to interstellar space. The appearance of a comet is called an apparition.
Extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids. Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System. However, the discovery of main-belt comets and active centaur minor planets has blurred the distinction between asteroids and comets. In the early 21st century, the discovery of some minor bodies with long-period comet orbits, but characteristics of inner solar system asteroids, were called Manx comets. They are still classified as comets, such as C/2014 S3 (PANSTARRS). Twenty-seven Manx comets were found from 2013 to 2017.
, there are 4,584 known comets. However, this represents a very small fraction of the total potential comet population, as the reservoir of comet-like bodies in the outer Solar System (in the Oort cloud) is about one trillion. Roughly one comet per year is visible to the naked eye, though many of those are faint and unspectacular. Particularly bright examples are called "great comets". Comets have been visited by uncrewed probes such as NASA's Deep Impact, which blasted a crater on Comet Tempel 1 to study its interior, and the European Space Agency's Rosetta, which became the first to land a robotic spacecraft on a comet.
== Etymology ==
The word comet derives from the Old English from the Latin or . That, in turn, is a romanization of the Greek 'wearing long hair', and the Oxford English Dictionary notes that the term () already meant 'long-haired star, comet' in Greek. was derived from () 'to wear the hair long', which was itself derived from () 'the hair of the head' and was used to mean 'the tail of a comet'.
The astronomical symbol for comets (represented in Unicode) is , consisting of a small disc with three hairlike extensions.
== Physical characteristics ==
=== Nucleus ===
The solid, core structure of a comet is known as the nucleus. Cometary nuclei are composed of an amalgamation of rock, dust, water ice, and frozen carbon dioxide, carbon monoxide, methane, and ammonia. As such, they are popularly described as "dirty snowballs" after Fred Whipple's model. Comets with a higher dust content have been called "icy dirtballs". The term "icy dirtballs" arose after observation of Comet 9P/Tempel 1 collision with an "impactor" probe sent by NASA Deep Impact mission in July 2005. Research conducted in 2014 suggests that comets are like "deep fried ice cream", in that their surfaces are formed of dense crystalline ice mixed with organic compounds, while the interior ice is colder and less dense. In 2009, it was confirmed that the amino acid glycine had been found in the comet dust recovered by NASA's Stardust mission. In August 2011, a report, based on NASA studies of meteorites found on Earth, was published suggesting DNA and RNA components (adenine, guanine, and related organic molecules) may have been formed on asteroids and comets.
The outer surfaces of cometary nuclei have a very low albedo, making them among the least reflective objects found in the Solar System. The Giotto space probe found that the nucleus of Halley's Comet (1P/Halley) reflects about four percent of the light that falls on it, and Deep Space 1 discovered that Comet Borrelly's surface reflects less than 3.0%;
Comet nuclei with radii of up to have been observed, but ascertaining their exact size is difficult. The nucleus of 322P/SOHO is probably only in diameter. A lack of smaller comets being detected despite the increased sensitivity of instruments has led some to suggest that there is a real lack of comets smaller than across. Known comets have been estimated to have an average density of . Because of their low mass, comet nuclei do not become spherical under their own gravity and therefore have irregular shapes.
Roughly six percent of the near-Earth asteroids are thought to be the extinct nuclei of comets that no longer experience outgassing, including 14827 Hypnos and 3552 Don Quixote.
Results from the Rosetta and Philae spacecraft show that the nucleus of 67P/Churyumov–Gerasimenko has no magnetic field, which suggests that magnetism may not have played a role in the early formation of planetesimals. Further, the ALICE spectrograph on Rosetta determined that electrons (within above the comet nucleus) produced from photoionization of water molecules by solar radiation, and not photons from the Sun as thought earlier, are responsible for the degradation of water and carbon dioxide molecules released from the comet nucleus into its coma. Instruments on the Philae lander found at least sixteen organic compounds at the comet's surface, four of which (acetamide, acetone, methyl isocyanate and propionaldehyde) have been detected for the first time on a comet.
=== Coma ===
The streams of dust and gas thus released form a huge and extremely thin atmosphere around the comet called the "coma". The force exerted on the coma by the Sun's radiation pressure and solar wind cause an enormous "tail" to form pointing away from the Sun.
The coma is generally made of water and dust, with water making up to 90% of the volatiles that outflow from the nucleus when the comet is within 3 to 4 astronomical units (450,000,000 to 600,000,000 km; 280,000,000 to 370,000,000 mi) of the Sun. The parent molecule is destroyed primarily through photodissociation and to a much smaller extent photoionization, with the solar wind playing a minor role in the destruction of water compared to photochemistry.
Although the solid nucleus of comets is generally less than across, the coma may be thousands or millions of kilometers across, sometimes becoming larger than the Sun. For example, about a month after an outburst in October 2007, comet 17P/Holmes briefly had a tenuous dust atmosphere larger than the Sun. The Great Comet of 1811 had a coma roughly the diameter of the Sun. Even though the coma can become quite large, its size can decrease about the time it crosses the orbit of Mars around from the Sun. Most comets are too faint to be visible without the aid of a telescope, but a few each decade become bright enough to be visible to the naked eye. Occasionally a comet may experience a huge and sudden outburst of gas and dust, during which the size of the coma greatly increases for a period of time. This happened in 2007 to Comet Holmes.
In 1996, comets were found to emit X-rays. This greatly surprised astronomers because X-ray emission is usually associated with very high-temperature bodies. The X-rays are generated by the interaction between comets and the solar wind: when highly charged solar wind ions fly through a cometary atmosphere, they collide with cometary atoms and molecules, "stealing" one or more electrons from the atom in a process called "charge exchange". This exchange or transfer of an electron to the solar wind ion is followed by its de-excitation into the ground state of the ion by the emission of X-rays and far ultraviolet photons.
===Bow shock===
Bow shocks form as a result of the interaction between the solar wind and the cometary ionosphere, which is created by the ionization of gases in the coma. As the comet approaches the Sun, increasing outgassing rates cause the coma to expand, and the sunlight ionizes gases in the coma. When the solar wind passes through this ion coma, the bow shock appears.
The first observations were made in the 1980s and 1990s as several spacecraft flew by comets 21P/Giacobini–Zinner, 1P/Halley, and 26P/Grigg–Skjellerup. It was then found that the bow shocks at comets are wider and more gradual than the sharp planetary bow shocks seen at, for example, Earth. These observations were all made near perihelion when the bow shocks already were fully developed.
The Rosetta spacecraft observed the bow shock at comet 67P/Churyumov–Gerasimenko at an early stage of bow shock development when the outgassing increased during the comet's journey toward the Sun. This young bow shock was called the "infant bow shock". The infant bow shock is asymmetric and, relative to the distance to the nucleus, wider than fully developed bow shocks.
=== Tails ===
In the outer Solar System, comets remain frozen and inactive and are extremely difficult or impossible to detect from Earth due to their small size. Statistical detections of inactive comet nuclei in the Kuiper belt have been reported from observations by the Hubble Space Telescope but these detections have been questioned. As a comet approaches the inner Solar System, solar radiation causes the volatile materials within the comet to vaporize and stream out of the nucleus, carrying dust away with them.
The streams of dust and gas each form their own distinct tail, pointing in slightly different directions. The tail of dust is left behind in the comet's orbit in such a manner that it often forms a curved tail called the type II or dust tail. On occasions—such as when Earth passes through a comet's orbital plane, the antitail, pointing in the opposite direction to the ion and dust tails, may be seen.
The observation of antitails contributed significantly to the discovery of solar wind. The ion tail is formed as a result of the ionization by solar ultra-violet radiation of particles in the coma. Once the particles have been ionized, they attain a net positive electrical charge, which in turn gives rise to an "induced magnetosphere" around the comet. The comet and its induced magnetic field form an obstacle to outward flowing solar wind particles. Because the relative orbital speed of the comet and the solar wind is supersonic, a bow shock is formed upstream of the comet in the flow direction of the solar wind. In this bow shock, large concentrations of cometary ions (called "pick-up ions") congregate and act to "load" the solar magnetic field with plasma, such that the field lines "drape" around the comet forming the ion tail.
If the ion tail loading is sufficient, the magnetic field lines are squeezed together to the point where, at some distance along the ion tail, magnetic reconnection occurs. This leads to a "tail disconnection event".
In 2013, ESA scientists reported that the ionosphere of the planet Venus streams outwards in a manner similar to the ion tail seen streaming from a comet under similar conditions."
=== Jets ===
Uneven heating can cause newly generated gases to break out of a weak spot on the surface of comet's nucleus, like a geyser. These streams of gas and dust can cause the nucleus to spin, and even split apart. Infrared imaging of Hartley 2 shows such jets exiting and carrying with it dust grains into the coma.
== Orbital characteristics ==
Most comets are small Solar System bodies with elongated elliptical orbits that take them close to the Sun for a part of their orbit and then out into the further reaches of the Solar System for the remainder. Comets are often classified according to the length of their orbital periods: The longer the period the more elongated the ellipse.
=== Short period ===
Periodic comets or short-period comets are generally defined as those having orbital periods of less than 200 years. They usually orbit more-or-less in the ecliptic plane in the same direction as the planets. Their orbits typically take them out to the region of the outer planets (Jupiter and beyond) at aphelion; for example, the aphelion of Halley's Comet is a little beyond the orbit of Neptune. Comets whose aphelia are near a major planet's orbit are called its "family". Such families are thought to arise from the planet capturing formerly long-period comets into shorter orbits.
At the shorter orbital period extreme, Encke's Comet has an orbit that does not reach the orbit of Jupiter, and is known as an Encke-type comet. Short-period comets with orbital periods less than 20 years and low inclinations (up to 30 degrees) to the ecliptic are called traditional Jupiter-family comets (JFCs). Those like Halley, with orbital periods of between 20 and 200 years and inclinations extending from zero to more than 90 degrees, are called Halley-type comets (HTCs). there are 73 known Encke-type comets (six of which are classified as Near-earth objects (NEOs)), 106 HTCs (36 of which are NEOs), and 815 JFCs (153 of which are NEOs).
Recently discovered main-belt comets form a distinct class, orbiting in more circular orbits within the asteroid belt.
Because their elliptical orbits frequently take them close to the giant planets, comets are subject to further gravitational perturbations. Short-period comets have a tendency for their aphelia to coincide with a giant planet's semi-major axis, with the JFCs being the largest group.
Based on their orbital characteristics, short-period comets are thought to originate from the centaurs and the Kuiper belt/scattered disc —a disk of objects in the trans-Neptunian region—whereas the source of long-period comets is thought to be the far more distant spherical Oort cloud (after the Dutch astronomer Jan Hendrik Oort who hypothesized its existence). Vast swarms of comet-like bodies are thought to orbit the Sun in these distant regions in roughly circular orbits. Occasionally the gravitational influence of the outer planets (in the case of Kuiper belt objects) or nearby stars (in the case of Oort cloud objects) may throw one of these bodies into an elliptical orbit that takes it inwards toward the Sun to form a visible comet. Unlike the return of periodic comets, whose orbits have been established by previous observations, the appearance of new comets by this mechanism is unpredictable. When flung into the orbit of the sun, and being continuously dragged towards it, tons of matter are stripped from the comets which greatly influence their lifetime; the more stripped, the shorter they live and vice versa.
=== Long period ===
Long-period comets have highly eccentric orbits and periods ranging from 200 years to thousands or even millions of years. For example, Comet McNaught had a heliocentric osculating eccentricity of 1.000019 near its perihelion passage epoch in January 2007 but is bound to the Sun with roughly a 92,600-year orbit because the eccentricity drops below 1 as it moves farther from the Sun. The future orbit of a long-period comet is properly obtained when the osculating orbit is computed at an epoch after leaving the planetary region and is calculated with respect to the center of mass of the Solar System. By definition long-period comets remain gravitationally bound to the Sun; those comets that are ejected from the Solar System due to close passes by major planets are no longer properly considered as having "periods". The orbits of long-period comets take them far beyond the outer planets at aphelia, and the plane of their orbits need not lie near the ecliptic. Long-period comets such as C/1999 F1 and C/2017 T2 (PANSTARRS) can have aphelion distances of nearly with orbital periods estimated around 6 million years.
Single-apparition or non-periodic comets are similar to long-period comets because they have parabolic or slightly hyperbolic trajectories when near perihelion in the inner Solar System. However, gravitational perturbations from giant planets cause their orbits to change. Single-apparition comets have a hyperbolic or parabolic osculating orbit which allows them to permanently exit the Solar System after a single pass of the Sun. The Sun's Hill sphere has an unstable maximum boundary of . Only a few hundred comets have been seen to reach a hyperbolic orbit (e > 1) when near perihelion that using a heliocentric unperturbed two-body best-fit suggests they may escape the Solar System.
, only two objects have been discovered with an eccentricity significantly greater than one: 1I/ʻOumuamua and 2I/Borisov, indicating an origin outside the Solar System. While ʻOumuamua, with an eccentricity of about 1.2, showed no optical signs of cometary activity during its passage through the inner Solar System in October 2017, changes to its trajectory—which suggests outgassing—indicate that it is probably a comet. On the other hand, 2I/Borisov, with an estimated eccentricity of about 3.36, has been observed to have the coma feature of comets, and is considered the first detected interstellar comet. Comet C/1980 E1 had an orbital period of roughly 7.1 million years before the 1982 perihelion passage, but a 1980 encounter with Jupiter accelerated the comet giving it the largest eccentricity (1.057) of any known solar comet with a reasonable observation arc. Comets not expected to return to the inner Solar System include C/1980 E1, C/2000 U5, C/2001 Q4 (NEAT), C/2009 R1, C/1956 R1, and C/2007 F1 (LONEOS).
Some authorities use the term "periodic comet" to refer to any comet with a periodic orbit (that is, all short-period comets plus all long-period comets), whereas others use it to mean exclusively short-period comets.
=== Oort cloud and Hills cloud ===
The Oort cloud is thought to occupy a vast space starting from between to as far as Some estimates place the outer edge at between . The outer cloud is only weakly bound to the Sun and supplies the long-period (and possibly Halley-type) comets that fall to inside the orbit of Neptune. it is seen as a possible source of new comets that resupply the relatively tenuous outer cloud as the latter's numbers are gradually depleted. The Hills cloud explains the continued existence of the Oort cloud after billions of years.
=== Exocomets ===
Exocomets beyond the Solar System have been detected and may be common in the Milky Way. The first exocomet system detected was around Beta Pictoris, a very young A-type main-sequence star, in 1987. A total of 11 such exocomet systems have been identified , using the absorption spectrum caused by the large clouds of gas emitted by comets when passing close to their star. After Kepler Space Telescope retired in October 2018, a new telescope called TESS Telescope has taken over Kepler's mission. Since the launch of TESS, astronomers have discovered the transits of comets around the star Beta Pictoris using a light curve from TESS. Since TESS has taken over, astronomers have since been able to better distinguish exocomets with the spectroscopic method. New planets are detected by the white light curve method which is viewed as a symmetrical dip in the charts readings when a planet overshadows its parent star. However, after further evaluation of these light curves, it has been discovered that the asymmetrical patterns of the dips presented are caused by the tail of a comet or of hundreds of comets.
== Effects of comets ==
=== Connection to meteor showers ===
As a comet is heated during close passes to the Sun, outgassing of its icy components releases solid debris too large to be swept away by radiation pressure and the solar wind. If Earth's orbit sends it through that trail of debris, which is composed mostly of fine grains of rocky material, there is likely to be a meteor shower as Earth passes through. Denser trails of debris produce quick but intense meteor showers and less dense trails create longer but less intense showers. Typically, the density of the debris trail is related to how long ago the parent comet released the material. The Perseid meteor shower, for example, occurs every year between 9 and 13 August, when Earth passes through the orbit of Comet Swift–Tuttle. Halley's Comet is the source of the Orionid shower in October.
=== Comets and impact on life ===
Many comets and asteroids collided with Earth in its early stages. Many scientists think that comets bombarding the young Earth about 4 billion years ago brought the vast quantities of water that now fill Earth's oceans, or at least a significant portion of it. Others have cast doubt on this idea. The detection of organic molecules, including polycyclic aromatic hydrocarbons, in significant quantities in comets has led to speculation that comets or meteorites may have brought the precursors of life—or even life itself—to Earth. In 2013 it was suggested that impacts between rocky and icy surfaces, such as comets, had the potential to create the amino acids that make up proteins through shock synthesis. The speed at which the comets entered the atmosphere, combined with the magnitude of energy created after initial contact, allowed smaller molecules to condense into the larger macro-molecules that served as the foundation for life. In 2015, scientists found significant amounts of molecular oxygen in the outgassings of comet 67P, suggesting that the molecule may occur more often than had been thought, and thus less an indicator of life as has been supposed.
It is suspected that comet impacts have, over long timescales, delivered significant quantities of water to Earth's Moon, some of which may have survived as lunar ice. Comet and meteoroid impacts are thought to be responsible for the existence of tektites and australites.
===Fear of comets===
Fear of comets as acts of God and signs of impending doom was highest in Europe from AD 1200 to 1650. The year after the Great Comet of 1618, for example, Gotthard Arthusius published a pamphlet stating that it was a sign that the Day of Judgment was near. He listed ten pages of comet-related disasters, including "earthquakes, floods, changes in river courses, hail storms, hot and dry weather, poor harvests, epidemics, war and treason and high prices".
By 1700 most scholars concluded that such events occurred whether a comet was seen or not. Using Edmond Halley's records of comet sightings, however, William Whiston in 1711 wrote that the Great Comet of 1680 had a periodicity of 574 years and was responsible for the worldwide flood in the Book of Genesis, by pouring water on Earth. His announcement revived for another century fear of comets, now as direct threats to the world instead of signs of disasters. Spectroscopic analysis in 1910 found the toxic gas cyanogen in the tail of Halley's Comet, causing panicked buying of gas masks and quack "anti-comet pills" and "anti-comet umbrellas" by the public.
== Fate of comets ==
=== Departure (ejection) from Solar System ===
If a comet is traveling fast enough, it may leave the Solar System. Such comets follow the open path of a hyperbola, and as such, they are called hyperbolic comets. Solar comets are only known to be ejected by interacting with another object in the Solar System, such as Jupiter. An example of this is Comet C/1980 E1, which was shifted from an orbit of 7.1 million years around the Sun, to a hyperbolic trajectory, after a 1980 close pass by the planet Jupiter. Interstellar comets such as 1I/ʻOumuamua and 2I/Borisov never orbited the Sun and therefore do not require a 3rd-body interaction to be ejected from the Solar System.
=== Extinction ===
Jupiter-family comets and long-period comets appear to follow very different fading laws. The JFCs are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages. Some asteroids in elliptical orbits are now identified as extinct comets. Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei. A significant cometary disruption was that of Comet Shoemaker–Levy 9, which was discovered in 1993. A close encounter in July 1992 had broken it into pieces, and over a period of six days in July 1994, these pieces fell into Jupiter's atmosphere—the first time astronomers had observed a collision between two objects in the Solar System. Other splitting comets include 3D/Biela in 1846 and 73P/Schwassmann–Wachmann from 1995 to 2006. Greek historian Ephorus reported that a comet split apart as far back as the winter of 372–373 BC. Comets are suspected of splitting due to thermal stress, internal gas pressure, or impact.
Comets 42P/Neujmin and 53P/Van Biesbroeck appear to be fragments of a parent comet. Numerical integrations have shown that both comets had a rather close approach to Jupiter in January 1850, and that, before 1850, the two orbits were nearly identical. Another group of comets that is the result of fragmentation episodes is the Liller comet family made of C/1988 A1 (Liller), C/1996 Q1 (Tabur), C/2015 F3 (SWAN), C/2019 Y1 (ATLAS), and C/2023 V5 (Leonard).
Some comets have been observed to break up during their perihelion passage, including great comets West and Ikeya–Seki. Biela's Comet was one significant example when it broke into two pieces during its passage through the perihelion in 1846. These two comets were seen separately in 1852, but never again afterward. Instead, spectacular meteor showers were seen in 1872 and 1885 when the comet should have been visible. A minor meteor shower, the Andromedids, occurs annually in November, and it is caused when Earth crosses the orbit of Biela's Comet.
Some comets meet a more spectacular end – either falling into the Sun or colliding with a planet or other body. Collisions between comets and planets or moons were common in the early Solar System: some of the many craters on the Moon, for example, may have been caused by comets. A recent collision of a comet with a planet occurred in July 1994 when Comet Shoemaker–Levy 9 broke up into pieces and collided with Jupiter.
== Nomenclature ==
The names given to comets have followed several different conventions over the past two centuries. Prior to the early 20th century, most comets were referred to by the year when they appeared, sometimes with additional adjectives for particularly bright comets; thus, the "Great Comet of 1680", the "Great Comet of 1882", and the "Great January Comet of 1910".
After Edmond Halley demonstrated that the comets of 1531, 1607, and 1682 were the same body and successfully predicted its return in 1759 by calculating its orbit, that comet became known as Halley's Comet. Similarly, the second and third known periodic comets, Encke's Comet and Biela's Comet, were named after the astronomers who calculated their orbits rather than their original discoverers. Later, periodic comets were usually named after their discoverers, but comets that had appeared only once continued to be referred to by the year of their appearance. For example, in 2019, astronomer Gennadiy Borisov observed a comet that appeared to have originated outside of the solar system; the comet was named 2I/Borisov after him.
== History of study ==
=== Early observations and thought ===
From ancient sources, such as Chinese oracle bones, it is known that comets have been noticed by humans for millennia. Until the sixteenth century, comets were usually considered bad omens of deaths of kings or noble men, or coming catastrophes, or even interpreted as attacks by heavenly beings against terrestrial inhabitants.
Aristotle (384–322 BC) was the first known scientist to use various theories and observational facts to employ a consistent, structured cosmological theory of comets. He believed that comets were atmospheric phenomena, due to the fact that they could appear outside of the zodiac and vary in brightness over the course of a few days. Aristotle's cometary theory arose from his observations and cosmological theory that everything in the cosmos is arranged in a distinct configuration. Part of this configuration was a clear separation between the celestial and terrestrial, believing comets to be strictly associated with the latter. According to Aristotle, comets must be within the sphere of the moon and clearly separated from the heavens. Also in the 4th century BC, Apollonius of Myndus supported the idea that comets moved like the planets. Aristotelian theory on comets continued to be widely accepted throughout the Middle Ages, despite several discoveries from various individuals challenging aspects of it.
In the 1st century AD, Seneca the Younger questioned Aristotle's logic concerning comets. Because of their regular movement and imperviousness to wind, they cannot be atmospheric, and are more permanent than suggested by their brief flashes across the sky. He pointed out that only the tails are transparent and thus cloudlike, and argued that there is no reason to confine their orbits to the zodiac. In criticizing Apollonius of Myndus, Seneca argues, "A comet cuts through the upper regions of the universe and then finally becomes visible when it reaches the lowest point of its orbit." While Seneca did not author a substantial theory of his own, his arguments would spark much debate among Aristotle's critics in the 16th and 17th centuries. Pliny observed comets as "human like", often describing their tails with "long hair" or "long beard". His system for classifying comets according to their color and shape was used for centuries.
There is a claim that an Arab scholar in 1258 noted several recurrent appearances of a comet (or a type of comet), and though it's not clear if he considered it to be a single periodic comet, it might have been a comet with a period of around 63 years.
In 1301, the Italian painter Giotto was the first person to accurately and anatomically portray a comet. In his work Adoration of the Magi, Giotto's depiction of Halley's Comet in the place of the Star of Bethlehem would go unmatched in accuracy until the 19th century and be bested only with the invention of photography.
Astrological interpretations of comets proceeded to take precedence clear into the 15th century, despite the presence of modern scientific astronomy beginning to take root. Comets continued to forewarn of disaster, as seen in the Luzerner Schilling chronicles and in the warnings of Pope Callixtus III.
In the 16th century, Tycho Brahe and Michael Maestlin demonstrated that comets must exist outside of Earth's atmosphere by measuring the parallax of the Great Comet of 1577. Within the precision of the measurements, this implied the comet must be at least four times more distant than from Earth to the Moon. Based on observations in 1664, Giovanni Borelli recorded the longitudes and latitudes of comets that he observed, and suggested that cometary orbits may be parabolic. Despite being a skilled astronomer, in his 1623 book The Assayer, Galileo Galilei rejected Brahe's theories on the parallax of comets and claimed that they may be a mere optical illusion, despite little personal observation.
Isaac Newton, in his Principia Mathematica of 1687, proved that an object moving under the influence of gravity by an inverse square law must trace out an orbit shaped like one of the conic sections, and he demonstrated how to fit a comet's path through the sky to a parabolic orbit, using the comet of 1680 as an example.
He describes comets as compact and durable solid bodies moving in oblique orbit and their tails as thin streams of vapor emitted by their nuclei, ignited or heated by the Sun. He suspected that comets were the origin of the life-supporting component of air. He pointed out that comets usually appear near the Sun, and therefore most likely orbit it. On their luminosity, he stated, "The comets shine by the Sun's light, which they reflect," with their tails illuminated by "the Sun's light reflected by a smoke arising from [the coma]".
In 1705, Edmond Halley (1656–1742) applied Newton's method to 23 cometary apparitions that had occurred between 1337 and 1698. He noted that three of these, the comets of 1531, 1607, and 1682, had very similar orbital elements, and he was further able to account for the slight differences in their orbits in terms of gravitational perturbation caused by Jupiter and Saturn. Confident that these three apparitions had been three appearances of the same comet, he predicted that it would appear again in 1758–59. Halley's predicted return date was later refined by a team of three French mathematicians: Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute, who predicted the date of the comet's 1759 perihelion to within one month's accuracy. When the comet returned as predicted, it became known as Halley's Comet.
As early as the 18th century, some scientists had made correct hypotheses as to comets' physical composition. In 1755, Immanuel Kant hypothesized in his Universal Natural History that comets were condensed from "primitive matter" beyond the known planets, which is "feebly moved" by gravity, then orbit at arbitrary inclinations, and are partially vaporized by the Sun's heat as they near perihelion. In 1836, the German mathematician Friedrich Wilhelm Bessel, after observing streams of vapor during the appearance of Halley's Comet in 1835, proposed that the jet forces of evaporating material could be great enough to significantly alter a comet's orbit, and he argued that the non-gravitational movements of Encke's Comet resulted from this phenomenon.
In the 19th century, the Astronomical Observatory of Padova was an epicenter in the observational study of comets. Led by Giovanni Santini (1787–1877) and followed by Giuseppe Lorenzoni (1843–1914), this observatory was devoted to classical astronomy, mainly to the new comets and planets orbit calculation, with the goal of compiling a catalog of almost ten thousand stars. Situated in the Northern portion of Italy, observations from this observatory were key in establishing important geodetic, geographic, and astronomical calculations, such as the difference of longitude between Milan and Padua as well as Padua to Fiume. Correspondence within the observatory, particularly between Santini and another astronomer Giuseppe Toaldo, mentioned the importance of comet and planetary orbital observations.
In 1950, Fred Lawrence Whipple proposed that rather than being rocky objects containing some ice, comets were icy objects containing some dust and rock. This "dirty snowball" model soon became accepted and appeared to be supported by the observations of an armada of spacecraft (including the European Space Agency's Giotto probe and the Soviet Union's Vega 1 and Vega 2) that flew through the coma of Halley's Comet in 1986, photographed the nucleus, and observed jets of evaporating material.
On 22 January 2014, ESA scientists reported the detection, for the first definitive time, of water vapor on the dwarf planet Ceres, the largest object in the asteroid belt. The detection was made by using the far-infrared abilities of the Herschel Space Observatory. The finding is unexpected because comets, not asteroids, are typically considered to "sprout jets and plumes". According to one of the scientists, "The lines are becoming more and more blurred between comets and asteroids."
=== Spacecraft missions ===
The Halley Armada describes the collection of spacecraft missions that visited and/or made observations of Halley's Comet 1980s perihelion. The space shuttle Challenger was intended to do a study of Halley's Comet in 1986, but exploded shortly after being launched.
Deep Impact. Debate continues about how much ice is in a comet. In 2001, the Deep Space 1 spacecraft obtained high-resolution images of the surface of Comet Borrelly. It was found that the surface of comet Borrelly is hot and dry, with a temperature of between , and extremely dark, suggesting that the ice has been removed by solar heating and maturation, or is hidden by the soot-like material that covers Borrelly. In July 2005, the Deep Impact probe blasted a crater on Comet Tempel 1 to study its interior. The mission yielded results suggesting that the majority of a comet's water ice is below the surface and that these reservoirs feed the jets of vaporized water that form the coma of Tempel 1. Renamed EPOXI, it made a flyby of Comet Hartley 2 on 4 November 2010.
Ulysses. In 2007, the Ulysses probe unexpectedly passed through the tail of the comet C/2006 P1 (McNaught) which was discovered in 2006. Ulysses was launched in 1990 and the intended mission was for Ulysses to orbit around the Sun for further study at all latitudes.
Stardust. Data from the Stardust mission show that materials retrieved from the tail of Wild 2 were crystalline and could only have been "born in fire", at extremely high temperatures of over . Although comets formed in the outer Solar System, radial mixing of material during the early formation of the Solar System is thought to have redistributed material throughout the proto-planetary disk. As a result, comets contain crystalline grains that formed in the early, hot inner Solar System. This is seen in comet spectra as well as in sample return missions. More recent still, the materials retrieved demonstrate that the "comet dust resembles asteroid materials". These new results have forced scientists to rethink the nature of comets and their distinction from asteroids.
Rosetta. The Rosetta probe orbited Comet Churyumov–Gerasimenko. On 12 November 2014, its lander Philae successfully landed on the comet's surface, the first time a spacecraft has ever landed on such an object in history.
== Classification ==
=== Great comets ===
Approximately once a decade, a comet becomes bright enough to be noticed by a casual observer, leading such comets to be designated as great comets. Broadly speaking, if a comet has a large and active nucleus, will pass close to the Sun, and is not obscured by the Sun as seen from Earth when at its brightest, it has a chance of becoming a great comet. However, Comet Kohoutek in 1973 fulfilled all the criteria and was expected to become spectacular but failed to do so. Comet West, which appeared three years later, had much lower expectations but became an extremely impressive comet.
The Great Comet of 1577 is a well-known example of a great comet. It passed near Earth as a non-periodic comet and was seen by many, including well-known astronomers Tycho Brahe and Taqi ad-Din. Observations of this comet led to several significant findings regarding cometary science, especially for Brahe.
The late 20th century saw a lengthy gap without the appearance of any great comets, followed by the arrival of two in quick succession—Comet Hyakutake in 1996, followed by Hale–Bopp, which reached maximum brightness in 1997 having been discovered two years earlier. The first great comet of the 21st century was C/2006 P1 (McNaught), which became visible to naked eye observers in January 2007. It was the brightest in over 40 years.
=== Sungrazing comets ===
A sungrazing comet is a comet that passes extremely close to the Sun at perihelion, generally within a few million kilometers. Although small sungrazers can be completely evaporated during such a close approach to the Sun, larger sungrazers can survive many perihelion passages. However, the strong tidal forces they experience often lead to their fragmentation.
About 90% of the sungrazers observed with SOHO are members of the Kreutz group, which all originate from one giant comet that broke up into many smaller comets during its first passage through the inner Solar System. The remainder contains some sporadic sungrazers, but four other related groups of comets have been identified among them: the Kracht, Kracht 2a, Marsden, and Meyer groups. The Marsden and Kracht groups both appear to be related to Comet 96P/Machholz, which is the parent of two meteor streams, the Quadrantids and the Arietids.
=== Unusual comets ===
Of the thousands of known comets, some exhibit unusual properties. Comet Encke (2P/Encke) orbits from outside the asteroid belt to just inside the orbit of the planet Mercury whereas the Comet 29P/Schwassmann–Wachmann currently travels in a nearly circular orbit entirely between the orbits of Jupiter and Saturn. 2060 Chiron, whose unstable orbit is between Saturn and Uranus, was originally classified as an asteroid until a faint coma was noticed. Similarly, Comet Shoemaker–Levy 2 was originally designated asteroid .
=== Largest ===
The largest known periodic comet is 95P/Chiron at 200 km in diameter that comes to perihelion every 50 years just inside of Saturn's orbit at 8 AU. The largest known Oort cloud comet is suspected of being Comet Bernardinelli-Bernstein at ≈150 km that will not come to perihelion until January 2031 just outside of Saturn's orbit at 11 AU. The Comet of 1729 is estimated to have been ≈100 km in diameter and came to perihelion inside of Jupiter's orbit at 4 AU.
=== Centaurs ===
Centaurs typically behave with characteristics of both asteroids and comets. Centaurs can be classified as comets such as 60558 Echeclus, and 166P/NEAT. 166P/NEAT was discovered while it exhibited a coma, and so is classified as a comet despite its orbit, and 60558 Echeclus was discovered without a coma but later became active, and was then classified as both a comet and an asteroid (174P/Echeclus). One plan for Cassini involved sending it to a centaur, but NASA decided to destroy it instead.
== Observation ==
A comet may be discovered photographically using a wide-field telescope or visually with binoculars. However, even without access to optical equipment, it is still possible for the amateur astronomer to discover a sungrazing comet online by downloading images accumulated by some satellite observatories such as SOHO. SOHO's 2000th comet was discovered by Polish amateur astronomer Michał Kusiak on 26 December 2010 and both discoverers of Hale–Bopp used amateur equipment (although Hale was not an amateur).
=== Lost ===
A number of periodic comets discovered in earlier decades or previous centuries are now lost comets. Their orbits were never known well enough to predict future appearances or the comets have disintegrated. However, occasionally a "new" comet is discovered, and calculation of its orbit shows it to be an old "lost" comet. An example is Comet 11P/Tempel–Swift–LINEAR, discovered in 1869 but unobservable after 1908 because of perturbations by Jupiter. It was not found again until accidentally rediscovered by LINEAR in 2001. There are at least 18 comets that fit this category.
== In popular culture ==
The depiction of comets in popular culture is firmly rooted in the long Western tradition of seeing comets as harbingers of doom and as omens of world-altering change. Halley's Comet alone has caused a slew of sensationalist publications of all sorts at each of its reappearances. It was especially noted that the birth and death of some notable persons coincided with separate appearances of the comet, such as with writers Mark Twain (who correctly speculated that he'd "go out with the comet" in 1910) whereas the appearance of Comet Hale–Bopp in 1997 triggered the mass suicide of the Heaven's Gate cult.
In science fiction, the impact of comets has been depicted as a threat overcome by technology and heroism (as in the 1998 films Deep Impact and Armageddon), or as a trigger of global apocalypse (Lucifer's Hammer, 1979) or zombies (Night of the Comet, 1984).
==In literature==
The long-period comet first recorded by Pons in Florence on 15 July 1825 inspired Lydia Sigourney's humorous poem in which all the celestial bodies argue over the comet's appearance and purpose.
== Gallery ==
File:Comet_C2020F3_NEOWISE_over_California_desert_landscape.png|Comet C/2020 F3 NEOWISE, July 2020
File:Comet P1 McNaught02 - 23-01-07-edited.jpg|Comet C/2006 P1 (McNaught) taken from Victoria, Australia 2007
File:Great Comet of 1882.jpg|The Great Comet of 1882 is a member of the Kreutz group
File:Great Comet 1861.jpg|Austrian astronomer Edmund Weiss sketched the Great Comet of 1861
File:X-rays from Hyakutake.jpg|Comet Hyakutake (X-ray, ROSAT satellite)
File:Asteroid P2013 P5 v2.jpg|"Active asteroid" 311P/PANSTARRS with several tails
File:NASA-14090-Comet-C2013A1-SidingSpring-Hubble-20140311.jpg|Comet Siding Spring (Hubble; 11 March 2014)
File:Comets WISE.jpg|Mosaic of 20 comets discovered by the WISE space telescope
File:PIA22419-Neowise-1stFourYearsDataFromDec2013-20180420.gif|NEOWISE – Comets appear in yellow in Neowise's first four years of collecting data (December 2013 to December 2017)
File:Lovejoy-hi1a srem dec12 14.gif|The STEREO solar observatory filmed Comet Lovejoy moving against the solar wind as it approached the Sun in December 2011
File:ITS Impact.gif|View from Deep Impacts impactor in its last moments before hitting Comet Tempel 1, July 4, 2005
Videos
File:NASA Developing Comet Harpoon for Sample Return.ogv|NASA is developing a comet harpoon for returning samples to Earth
File:Encke tail rip off.ogg|The STEREO solar observatory filmed Comet Encke temporarily losing its tail, April 20, 2007
|
[
"Luzerner Schilling",
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"C/2023 V5 (Leonard)",
"Friedrich Wilhelm Bessel",
"C/2012 F6 (Lemmon)"
] |
5,965 |
Wikipedia:Status of the porting of the CIA World Factbook
|
There is now a 2010 CIA - The World Factbook available online. Most of our entries are from the 2000 edition. Anyone with a lot of time and a sense of purpose is encouraged to update licence article's with the new data. Please state the World Factbook year to which the country has been updated when updating this list (i.e. "updated to 2007" not "finished").
==Pieces of information ported not country-by-country==
Table of historical exchange rates
Abbreviations used in CIA World Factbook (2002 edition; not entirely ported to List of general acronyms)
--------------------------------------------
==Countries==
Please annotate the list below with the current status of the port from the CIA web site to the Wikipedia
__NOTOC__
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z
===A===
Afghanistan (updated to 2007) —Cronholm144 11:37, 15 August 2007 (UTC)
Akrotiri (updated to 2007) —Cronholm144 11:37, 15 August 2007 (UTC)
Albania (updated to 2007) —Cronholm144 15:25, 15 August 2007 (UTC)
Algeria (Updated to 2003) Regulus 11:05, 6 Sep 2003 (UTC)
American Samoa
Andorra
Angola (updated to 2003) Greenman 31 Oct 2003
Anguilla
Antarctica
Antigua and Barbuda
Arctic Ocean
Argentina
Armenia
Aruba
Ashmore and Cartier Islands
Atlantic Ocean
Australia
Austria
Azerbaijan
===B===
Bahamas, The
Bahrain
Baker Island
Bangladesh
Barbados
Belarus
Belgium
Belize
Benin (geography done)
Bermuda (updated all the stats in Economy of Bermuda by Scratchdawg 16:37, 16 February 2007 (UTC))
Bhutan
Bolivia
Bosnia and Herzegovina (partly 2000, partly 2003)
Botswana (updated to 2003) Greenman 2 Nov 2003
Bouvet Island
Brazil
British Indian Ocean Territory
British Virgin Islands (Geography updated to 2004)
Brunei
Bulgaria
Burkina Faso
Burma
Burundi
===C===
Cambodia
Cameroon
Canada
Cape Verde
Cayman Islands
Central African Republic
Chad
Chile
China
Christmas Island
Clipperton Island
Cocos (Keeling) Islands
Colombia
Comoros (just added, Aug. 1 '01)
Congo, Democratic Republic of the (updated to 2003) Greenman 31 Oct 2003
Congo, Republic of the
Cook Islands
Coral Sea Islands
Costa Rica
Ivory Coast
Croatia (updated to 2003)
Cuba
Curacao
Cyprus
Czech Republic
===D===
Denmark
Dhekelia
Djibouti
Dominica
Dominican Republic
===E===
Ecuador
Egypt
El Salvador
Equatorial Guinea
Eritrea (updated to 2006)
Estonia
Ethiopia (updated to 2006)
European Union
===F===
Falkland Islands (Islas Malvinas) (info as CIA factbook of 10 January, 2006, extended)
Faroe Islands
Fiji
Finland
France
French Polynesia
French Southern and Antarctic Lands
===G===
Gabon
Gambia, The
Gaza Strip See also: Palestine
Georgia (Updated to 2004)
Germany
Ghana
Gibraltar
Greece
Greenland
Grenada
Guam
Guatemala
Guernsey
Guinea
Guinea-Bissau
Guyana
===H===
Haiti
Heard Island and McDonald Islands
Holy See (Vatican City)
Honduras
Hong Kong
Howland Island
Hungary
===I===
Iceland
India (updated to 2003 (Transportation/Communication)
Indian Ocean
Indonesia
Iran
Iraq
Ireland
Isle of Man
Israel See also: Palestine
Italy
===J===
Jamaica
Jan Mayen
Japan
Jarvis Island
Jersey
Johnston Atoll
Jordan
===K===
Kazakhstan
Kenya
Kingman Reef
Kiribati
Korea, North
Korea, South
Kosovo
Kuwait
Kyrgyzstan
===L===
Laos
Latvia
Lebanon
Lesotho
Liberia
Libya
Liechtenstein
Lithuania
Luxembourg
===M===
Macau
Macedonia
Madagascar
Malawi
Malaysia
Maldives
Mali
Malta
Marshall Islands
Mauritania
Mauritius
Mayotte
Mexico
Micronesia, Federated States of
Midway Islands
Moldova
Monaco
Mongolia
Montenegro
Montserrat
Morocco
Mozambique (updated to 2003) Greenman 8 Nov 2003
===N===
Namibia (updated to 2003) Greenman 2 Nov 2003
Nauru
Navassa Island
Nepal
Netherlands
New Caledonia
New Zealand (Updated to 2003) RossA 07:07, 11 Dec 2003 (UTC)
Nicaragua
Niger
Nigeria
Niue
Norfolk Island
Northern Mariana Islands
Norway
===O===
Oman
===P===
Pacific Ocean
Pakistan
Palau
Palmyra Atoll
Panama
Papua New Guinea (geography updated)
Paracel Islands
Paraguay
Peru
Philippines
Pitcairn Islands
Poland
Portugal
Puerto Rico
===Q===
Qatar
===R===
Romania
Russia
Rwanda
===S===
Saint Barthelemy
Saint Helena, Ascension, and Tristan da Cunha
Saint Kitts and Nevis
Saint Lucia
Saint Martin
Saint Pierre and Miquelon
Saint Vincent and the Grenadines
Samoa
San Marino
São Tomé and Príncipe
Saudi Arabia
Senegal
Serbia - almost updated to 2003 data; have not done demographics or government) —The preceding unsigned comment was added by Hoshie (talk • contribs) .
Seychelles
Sierra Leone (updated to 2003) Greenman 15 November 2003
Singapore
Sint Maarten
Slovakia
Slovenia
Solomon Islands
Somalia
South Africa
South Georgia and South Sandwich Islands
Southern Ocean
South Sudan
Spain
Spratly Islands
Sri Lanka
Sudan
Suriname
Svalbard
Swaziland (updated to 2003) Greenman 12 Nov 2003
Sweden
Switzerland
Syria
===T===
Taiwan
Tajikistan
Tanzania
Thailand
Timor-Leste
Togo
Tokelau
Tonga
Trinidad and Tobago (updated to 2008) Christianwelsh 25 April 2008
Tunisia
Turkey
Turkmenistan
Turks and Caicos Islands
Tuvalu
===U===
Uganda
Ukraine
United Arab Emirates
United Kingdom
United States
United States Pacific Island Wildlife Refuges
Uruguay
Uzbekistan
===V===
Vanuatu
Venezuela
Vietnam
Virgin Islands (updated all to 2010 Gruepig (talk) 08:02, 22 November 2010 (UTC))
===W===
Wake Island
Wallis and Futuna
West Bank See also: Palestine
Western Sahara
"World" entry under Earth
===Y===
Yemen
===Z===
Zambia (updated to 2003) Greenman 13 Dec 2003
Zimbabwe (updated to 2003) Greenman 13 Nov 2003
----
Naming issues:
East Timor - entry is under Timor-Leste
Myanmar - entry is under Burma
Palestine - separate entries under West Bank and Gaza Strip
Republic of Macedonia - entry is under Macedonia
----
The Department of State info is at http://www.state.gov/r/pa/bgn/ ; I'm going about adding that alphabetically, as well; it's taking some time because not all of the text can be cut and pasted directly, at least not without looking sloppy. Much of it has to be integrated or left unadded, and some of their information, oddly enough, conflicts with the CIA info, esp. in re: economic figures. The status of that is here
See also : CIA World Factbook
|
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"Serbia",
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"New Zealand",
"Democratic Republic of the Congo",
"Guinea-Bissau",
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"Slovenia",
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"Zimbabwe",
"Cocos Islands",
"Chile",
"European Union",
"Vietnam",
"International Tropical Timber Agreement, 1983",
"Ghana",
"Clipperton Island",
"Papua New Guinea",
"Cook Islands",
"Togo",
"Brunei",
"Turkey",
"Indian Ocean",
"Czech Republic",
"India",
"Slovakia",
"United Kingdom",
"Egypt",
"Liberia",
"Svalbard",
"Burma",
"El Salvador",
"Latvia",
"Saint Kitts and Nevis",
"Tokelau",
"Chad",
"Vanuatu",
"Sint Maarten",
"Convention on the Prevention of Marine Pollution by Dumping Wastes and Other Matter",
"Bolivia",
"Trinidad and Tobago",
"Monaco",
"South Georgia and the South Sandwich Islands",
"South Sudan",
"Convention on Fishing and Conservation of Living Resources of the High Seas",
"Liechtenstein",
"Eritrea",
"Andorra",
"Anguilla",
"Libya",
"Mongolia (country)",
"Bhutan",
"Palmyra Atoll",
"Azerbaijan",
"Cayman Islands",
"Republic of the Congo",
"Midway Islands",
"Croatia",
"São Tomé and Príncipe",
"Barbados",
"Belize",
"Tonga",
"Equatorial Guinea",
"Albania",
"Volatile Organic Compounds Protocol",
"Turkmenistan",
"Sulphur Emissions Reduction Protocol",
"United Nations Convention on the Law of the Sea",
"Cape Verde",
"Lithuania",
"American Samoa",
"Panama",
"Bangladesh",
"Tanzania",
"China",
"Lesotho",
"Senegal",
"Mayotte",
"Geography of the British Virgin Islands",
"Jamaica",
"Indonesia",
"Italy",
"Virgin Islands",
"Antarctica",
"Montenegro",
"Kyrgyzstan",
"Malta",
"San Marino",
"Akrotiri",
"Korea, North",
"Ethiopia",
"Isle of Man",
"Nigeria",
"Syria",
"Swaziland",
"Basel Convention",
"Faroe Islands",
"Coral Sea Islands",
"Southern Ocean",
"Switzerland",
"Atlantic Ocean",
"Belarus",
"Falkland Islands",
"Thailand",
"United Arab Emirates",
"Iceland",
"French Polynesia",
"Macau",
"Russia",
"Iraq",
"Dominican Republic",
"Madagascar",
"Spratly Islands",
"Turks and Caicos Islands",
"United Nations Convention to Combat Desertification",
"Costa Rica",
"MARPOL 73/78",
"South Africa",
"Saint Barthelemy",
"Guyana",
"Norfolk Island",
"Haiti",
"Australia",
"Dhekelia",
"Somalia",
"Georgia (country)",
"Montreal Protocol on Substances That Deplete the Ozone Layer",
"Armenia",
"Republic of Ireland",
"Curaçao",
"Malaysia",
"Nepal",
"Grenada",
"Rwanda",
"Suriname",
"Saint Pierre and Miquelon",
"Bahamas",
"Comoros",
"Finland",
"Palestinian territories",
"Guernsey",
"Iran",
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"United Nations Framework Convention on Climate Change",
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"Uruguay",
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"Central African Republic",
"Kuwait",
"New Caledonia",
"Pakistan"
] |
5,966 |
Compost
|
Compost is a mixture of ingredients used as plant fertilizer and to improve soil's physical, chemical, and biological properties. It is commonly prepared by decomposing plant and food waste, recycling organic materials, and manure. The resulting mixture is rich in plant nutrients and beneficial organisms, such as bacteria, protozoa, nematodes, and fungi. Compost improves soil fertility in gardens, landscaping, horticulture, urban agriculture, and organic farming, reducing dependency on commercial chemical fertilizers. The benefits of compost include providing nutrients to crops as fertilizer, acting as a soil conditioner, increasing the humus or humic acid contents of the soil, and introducing beneficial microbes that help to suppress pathogens in the soil and reduce soil-borne diseases.
At the simplest level, composting requires gathering a mix of green waste (nitrogen-rich materials such as leaves, grass, and food scraps) and brown waste (woody materials rich in carbon, such as stalks, paper, and wood chips). Composting can be a multistep, closely monitored process with measured inputs of water, air, and carbon- and nitrogen-rich materials. The decomposition process is aided by shredding the plant matter, adding water, and ensuring proper aeration by regularly turning the mixture in a process using open piles or windrows. Fungi, earthworms, and other detritivores further break up the organic material. Aerobic bacteria and fungi manage the chemical process by converting the inputs into heat, carbon dioxide, and ammonium ions.
Composting is an important part of waste management, since food and other compostable materials make up about 20% of waste in landfills, and due to anaerobic conditions, these materials take longer to biodegrade in the landfill. Composting offers an environmentally superior alternative to using organic material for landfill because composting reduces methane emissions due to anaerobic conditions, and provides economic and environmental co-benefits. For example, compost can also be used for land and stream reclamation, wetland construction, and landfill cover.
== Fundamentals ==
Composting is an aerobic method of decomposing organic solid wastes, so it can be used to recycle organic material. The process involves decomposing organic material into a humus-like material, known as compost, which is a good fertilizer for plants.
Composting organisms require four equally important ingredients to work effectively:
Composting is most efficient with a carbon-to-nitrogen ratio of about 25:1. Hot composting focuses on retaining heat to increase the decomposition rate, thus producing compost more quickly. Rapid composting is favored by having a carbon-to-nitrogen ratio of about 30 carbon units or less. Above 30, the substrate is nitrogen starved. Below 15, it is likely to outgas a portion of nitrogen as ammonia.
Nearly all dead plant and animal materials have both carbon and nitrogen in different amounts. Fresh grass clippings have an average ratio of about 15:1 and dry autumn leaves about 50:1 depending upon species.
Thermophilic bacteria do not reproduce and are not active between , yet are found throughout soil. They activate once the mesophilic bacteria have begun to break down organic matter and increase the temperature to their optimal range. Thermophilic bacteria thrive at higher temperatures, reaching in typical mixes. Large-scale composting operations, such as windrow composting, may exceed this temperature, potentially killing beneficial soil microorganisms but also pasteurizing the waste.
==== Physical decomposers ====
Ants create nests, making the soil more porous and transporting nutrients to different areas of the compost.
Mesophilic phase: The initial, mesophilic phase is when the decomposition is carried out under moderate temperatures by mesophilic microorganisms. 2 to 8 days
Thermophilic phase: As the temperature rises, a second, thermophilic phase starts, in which various thermophilic bacteria carry out the decomposition under higher temperatures (.)
Cooling phase (also called Mesophilic II)
Maturation phase: As the supply of high-energy compounds dwindles, the temperature starts to decrease.
Semicomposting is the degradation process that handles volumes of organic waste lower than that recommended for composting and therefore does not present a thermophilic stage, because mesophilic microorganisms are the only responsible ones, for the degradation of organic matter.
=== Hot and cold composting – impact on timing ===
The time required to compost material relates to the volume of material, the particle size of the inputs (e.g. wood chips break down faster than branches), and the amount of mixing and aeration. Such short processes involve some changes to traditional methods, including smaller, more homogenized particle sizes in the input materials, controlling carbon-to-nitrogen ratio (C:N) at 30:1 or less, and careful monitoring of the moisture level.
Cold composting is a slower process that can take up to a year to complete. It results from smaller piles, including many residential compost piles that receive small amounts of kitchen and garden waste over extended periods. Piles smaller than tend not to reach and maintain high temperatures. Turning is not necessary with cold composting, although a risk exists that parts of the pile may go anaerobic as it becomes compacted or waterlogged.
=== Pathogen removal ===
Composting can destroy some pathogens and seeds, by reaching temperatures above .
Dealing with stabilized compost – i.e. composted material in which microorganisms have finished digesting the organic matter and the temperature has reached between – poses very little risk, as these temperatures kill pathogens and even make oocysts unviable. The temperature at which a pathogen dies depends on the pathogen, how long the temperature is maintained (seconds to weeks), and pH.
Compost products such as compost tea and compost extracts have been found to have an inhibitory effect on Fusarium oxysporum, Rhizoctonia species, and Pythium debaryanum, plant pathogens that can cause crop diseases. Aerated compost teas are more effective than compost extracts. Compost is a good source of biocontrol agents like B. subtilis, B. licheniformis, and P. chrysogenum that fight plant pathogens.
Aspergillosis
Farmer's lung
Histoplasmosis – a fungus that grows in guano and bird droppings
Legionnaires' disease
Paronychia – via infection around the fingernails and toenails
Tetanus – a central nervous system disease
Oocytes are rendered unviable by temperatures over . Composting at home reduces the amount of green waste being hauled to dumps or composting facilities. The reduced volume of materials being picked up by trucks results in fewer trips, which in turn lowers the overall emissions from the waste-management fleet.
== Materials that can be composted ==
Potential sources of compostable materials, or feedstocks, include residential, agricultural, and commercial waste streams. Residential food or yard waste can be composted at home, or collected for inclusion in a large-scale municipal composting facility. In some regions, it could also be included in a local or neighborhood composting project.
=== Organic solid waste ===
The two broad categories of organic solid waste are green and brown. Green waste is generally considered a source of nitrogen and includes pre- and post-consumer food waste, grass clippings, garden trimmings, and fresh leaves.
Brown waste is a carbon source. Typical examples are dried vegetation and woody material such as fallen leaves, straw, woodchips, limbs, logs, pine needles, sawdust, and wood ash, but not charcoal ash. Products derived from wood such as paper and plain cardboard are also considered carbon sources.
=== Human excreta ===
Human excreta, sometimes called "humanure" in the composting context, can be added as an input to the composting process since it is a nutrient-rich organic material. Nitrogen, which serves as a building block for important plant amino acids, is found in solid human waste. Phosphorus, which helps plants convert sunlight into energy in the form of ATP, can be found in liquid human waste.
Solid human waste can be collected directly in composting toilets, or indirectly in the form of sewage sludge after it has undergone treatment in a sewage treatment plant. Both processes require capable design, as potential health risks need to be managed. In the case of home composting, a wide range of microorganisms, including bacteria, viruses, and parasitic worms, can be present in feces, and improper processing can pose significant health risks. In the case of large sewage treatment facilities that collect wastewater from a range of residential, commercial and industrial sources, there are additional considerations. The composted sewage sludge, referred to as biosolids, can be contaminated with a variety of metals and pharmaceutical compounds. Insufficient processing of biosolids can also lead to problems when the material is applied to land.
Urine can be put on compost piles or directly used as fertilizer. Adding urine to compost can increase temperatures, so can increase its ability to destroy pathogens and unwanted seeds. Unlike feces, urine does not attract disease-spreading flies (such as houseflies or blowflies), and it does not contain the most hardy of pathogens, such as parasitic worm eggs.
=== Animal remains ===
Animal carcasses may be composted as a disposal option. Such material is rich in nitrogen.
==== Human bodies ====
== Composting technologies ==
=== Industrial-scale composting ===
==== In-vessel composting ====
==== Aerated static-pile composting ====
==== Windrow composting ====
=== Other systems at household level ===
==== Hügelkultur (raised garden beds or mounds) ====
The practice of making raised garden beds or mounds filled with rotting wood is also called in German. It is in effect creating a nurse log that is covered with soil.
Benefits of Hügelkultur garden beds include water retention and warming of soil. Buried wood acts like a sponge as it decomposes, able to capture water and store it for later use by crops planted on top of the bed.
==== Composting toilets ====
=== Related technologies ===
Vermicompost (also called worm castings, worm humus, worm manure, or worm faeces) is the end product of the breakdown of organic matter by earthworms. These castings have been shown to contain reduced levels of contaminants and a higher saturation of nutrients than the organic materials before vermicomposting.
Black soldier fly (Hermetia illucens) larvae are able to rapidly consume large amounts of organic material and can be used to treat human waste. The resulting compost still contains nutrients and can be used for biogas production, or further traditional composting or vermicomposting
Bokashi is a fermentation process rather than a decomposition process, and so retains the feedstock's energy, nutrient and carbon contents. There must be sufficient carbohydrate for fermentation to complete and therefore the process is typically applied to food waste, including noncompostable items. Carbohydrate is transformed into lactic acid, which dissociates naturally to form lactate, a biological energy carrier. The preserved result is therefore readily consumed by soil microbes and from there by the entire soil food web, leading to a significant increase in soil organic carbon and turbation. The process completes in weeks and returns soil acidity to normal.
Co-composting is a technique that processes organic solid waste together with other input materials such as dewatered fecal sludge or sewage sludge.
== Uses ==
===Agriculture and gardening===
On open ground for growing wheat, corn, soybeans, and similar crops, compost can be broadcast across the top of the soil using spreader trucks or spreaders pulled behind a tractor. It is expected that the spread layer is very thin (approximately ) and worked into the soil prior to planting. Application rates of or more are not unusual when trying to rebuild poor soils or control erosion. Due to the extremely high cost of compost per unit of nutrients in the United States, on-farm use is relatively rare since rates over 4 tons/acre may not be affordable. This results from an over-emphasis on "recycling organic matter" than on "sustainable nutrients." In countries such as Germany, where compost distribution and spreading are partially subsidized in the original waste fees, compost is used more frequently on open ground on the premise of nutrient "sustainability".
In plasticulture, strawberries, tomatoes, peppers, melons, and other fruits and vegetables are grown under plastic to control temperature, retain moisture and control weeds. Compost may be banded (applied in strips along rows) and worked into the soil prior to bedding and planting, be applied at the same time the beds are constructed and plastic laid down, or used as a top dressing.
Many crops are not seeded directly in the field but are started in seed trays in a greenhouse. When the seedlings reach a certain stage of growth, they are transplanted in the field. Compost may be part of the mix used to grow the seedlings, but is not normally used as the only planting substrate. The particular crop and the seeds' sensitivity to nutrients, salts, etc. dictates the ratio of the blend, and maturity is important to insure that oxygen deprivation will not occur or that no lingering phyto-toxins remain.
Compost can be added to soil, coir, or peat, as a tilth improver, supplying humus and nutrients. It provides a rich growing medium as absorbent material. This material contains moisture and soluble minerals, which provide support and nutrients. Although it is rarely used alone, plants can flourish from mixed soil that includes a mix of compost with other additives such as sand, grit, bark chips, vermiculite, perlite, or clay granules to produce loam. Compost can be tilled directly into the soil or growing medium to boost the level of organic matter and the overall fertility of the soil. Compost that is ready to be used as an additive is dark brown or even black with an earthy smell. and the possible tie up of nitrogen by incompletely decomposed lignin. It is very common to see blends of 20–30% compost used for transplanting seedlings.
Compost can be used to increase plant immunity to diseases and pests.
==== Compost tea ====
Compost tea is made up of extracts of fermented water leached from composted materials. Composts can be either aerated or non-aerated depending on its fermentation process. Compost teas are generally produced from adding compost to water in a ratio of 1:4–1:10, occasionally stirring to release microbes. and soil-borne diseases.
=== Other ===
Compost can also be used for land and stream reclamation, wetland construction, and landfill cover.
The temperatures generated by compost can be used to heat greenhouses, such as by being placed around the outside edges.
== Regulations ==
There are process and product guidelines in Europe that date to the early 1980s (Germany, the Netherlands, Switzerland) and only more recently in the UK and the US. In both these countries, private trade associations within the industry have established loose standards, some say as a stop-gap measure to discourage independent government agencies from establishing tougher consumer-friendly standards. Compost is regulated in Canada and Australia as well.
EPA Class A and B guidelines in the United States were developed solely to manage the processing and beneficial reuse of sludge, also now called biosolids, following the US EPA ban of ocean dumping. About 26 American states now require composts to be processed according to these federal protocols for pathogen and vector control, even though the application to non-sludge materials has not been scientifically tested. An example is that green waste composts are used at much higher rates than sludge composts were ever anticipated to be applied at. U.K guidelines also exist regarding compost quality, as well as Canadian, Australian, and the various European states.
In the United States, some compost manufacturers participate in a testing program offered by a private lobbying organization called the U.S. Composting Council. The USCC was originally established in 1991 by Procter & Gamble to promote composting of disposable diapers, following state mandates to ban diapers in landfills, which caused a national uproar. Ultimately the idea of composting diapers was abandoned, partly since it was not proven scientifically to be possible, and mostly because the concept was a marketing stunt in the first place. After this, composting emphasis shifted back to recycling organic wastes previously destined for landfills. There are no bonafide quality standards in America, but the USCC sells a seal called "Seal of Testing Assurance" (also called "STA"). For a considerable fee, the applicant may display the USCC logo on products, agreeing to volunteer to customers a current laboratory analysis that includes parameters such as nutrients, respiration rate, salt content, pH, and limited other indicators.
Many countries such as Wales and some individual cities such as Seattle and San Francisco require food and yard waste to be sorted for composting (San Francisco Mandatory Recycling and Composting Ordinance).
The USA is the only Western country that does not distinguish sludge-source compost from green-composts, and by default 50% of US states expect composts to comply in some manner with the federal EPA 503 rule promulgated in 1984 for sludge products.
There are health risk concerns about PFASs ("forever chemicals") levels in compost derived from sewage sledge sourced biosolids, and EPA has not set health risk standards for this. The Sierra Club recommends that home gardeners avoid the use of sewage sludge-base fertilizer and compost, in part due to potentially high levels of PFASs. The EPA PFAS Strategic Roadmap initiative, running from 2021 to 2024, will consider the full lifecycle of PFAS including health risks of PFAS in wastewater sludge.
== History ==
Composting dates back to at least the early Roman Empire and was mentioned as early as Cato the Elder's 160 BCE piece . Traditionally, composting involved piling organic materials until the next planting season, at which time the materials would have decayed enough to be ready for use in the soil. Methodologies for organic composting were part of traditional agricultural systems around the world.
Composting began to modernize somewhat in the 1920s in Europe as a tool for organic farming. The first industrial station for the transformation of urban organic materials into compost was set up in Wels, Austria, in the year 1921. Early proponents of composting in farming include Rudolf Steiner, founder of a farming method called biodynamics, and Annie Francé-Harrar, who was appointed on behalf of the government in Mexico and supported the country in 1950–1958 to set up a large humus organization in the fight against erosion and soil degradation. Sir Albert Howard, who worked extensively in India on sustainable practices, and Lady Eve Balfour were also major proponents of composting. Modern scientific composting was imported to America by the likes of J. I. Rodale – founder of Rodale, Inc. Organic Gardening, and others involved in the organic farming movement.
|
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"List of composting systems",
"J. I. Rodale",
"Rotifer",
"biodynamic agriculture",
"De Agri Cultura",
"List of environment topics",
"Bark (botany)",
"thermophilic",
"John Innes compost",
"mesophilic",
"garden",
"fertilizer",
"Organic farming",
"urban agriculture",
"sand",
"Rhizoctonia solani",
"Hügelkultur",
"Histoplasmosis",
"India",
"Protozoa",
"wheat",
"Traditional agriculture",
"Aspergillosis",
"food waste",
"pasteurizing",
"manure",
"San Francisco Mandatory Recycling and Composting Ordinance",
"beneficial organism",
"windrow",
"Capsicum",
"List of sustainable agriculture topics",
"phytotoxicity",
"sludge",
"Anaerobic digestion",
"Bokashi (horticulture)",
"perlite",
"Vector (epidemiology)",
"wikt:anaerobic",
"methane",
"strawberries",
"seed",
"Bacillus subtilis",
"Pythium debaryanum",
"List of organic gardening and farming topics",
"Lady Eve Balfour",
"vermiculite",
"Fusarium oxysporum",
"yeast",
"melon",
"oxidation",
"nutrient",
"greenhouse gas",
"Sow bugs",
"fermentation",
"global warming",
"Disposal of human corpses",
"The Guardian",
"Wales",
"microorganism",
"sponge (material)",
"decomposition",
"Escherichia coli",
"Farmer's lung",
"Soil science",
"loam",
"green waste",
"Fly",
"composting toilets",
"Salmonella",
"Humic acids",
"humus",
"Maize",
"Vermicompost",
"ammonium",
"organic matter",
"sewage sludge",
"Mesophile",
"nurse log",
"methane emissions",
"peat",
"Actinomycetota",
"Permaculture",
"Legionnaires' disease",
"Springtail",
"Tetanus",
"brown waste",
"Urine",
"Compost",
"Housefly",
"coir",
"tilth",
"tomato",
"soil conditioner",
"lignin",
"soybean",
"seedlings",
"horticulture",
"parasitic worm",
"wood chips",
"Biocontrol",
"plasticulture",
"landfill",
"Terra preta",
"windrow composting",
"microbiota",
"The New York Times",
"fecal sludge",
"Aerobic bacteria",
"Decomposition",
"slug",
"carbon-to-nitrogen ratio",
"detritivore",
"Oocyte",
"greenhouse",
"mite",
"landfill gas",
"Sir Albert Howard"
] |
5,970 |
Capitol
|
Capitol, capitols or The Capitol may refer to:
==Places and buildings==
===Legislative building===
United States Capitol, in Washington, D.C.
National Capitol of Colombia, in Bogotá
Palacio Federal Legislativo, in Caracas, Venezuela
National Capitol of Cuba, in Havana, Cuba
Capitol of Palau, in Ngerulmud
List of legislative buildings
List of state and territorial capitols in the United States
===United States===
Capitol Technology University, formerly Capitol College, Laurel, Maryland
Capitol Butte, a mountain in Arizona
Capitol Reef National Park, a National Park in Utah
The Capitol (Fayetteville, North Carolina), a department store
Capitol (Williamsburg, Virginia), a historic building that housed the House of Burgesses of the Colony of Virginia 1705–1779
===Elsewhere===
Capitoline Hill, a hill in Rome, Italy
Capitole de Toulouse, a historic building in Toulouse, France
The Capitol (Hong Kong), a private housing estate in China
==Arts, entertainment and media==
Capitol (board game), a Roman-themed board game
Capitol (The Hunger Games trilogy), a fictional city in The Hunger Games novels
Capitol (TV series), a US soap opera
Capitol (short story collection), a book by Orson Scott Card
Capitol Broadcasting Center, Philippine broadcasting company
Capitol Broadcasting Company, American media company
Capitol Records, a US record label
The Capitols, a soul trio based in Detroit, Michigan, US
==Sport==
===United States===
Capitol Wrestling Corporation, a predecessor organization to World Wrestling Entertainment
Bismarck Capitols, a sem-pro ice hockey team in Bismarck, North Dakota, in the Southwest Hockey League
Des Moines Capitols, a minor league professional ice hockey team from Des Moines, Iowa, in the International Hockey League
Harlingen Capitols, a minor league professional baseball team from Harlingen, Texas
Harrisburg Capitols, a minor league American football team from Harrisburg, Pennsylvania, in the Atlantic Coast Football League
Harrisburg Capitols, a professional basketball team from Harrisburg, Pennsylvania, in the Eastern Professional Basketball League; the successor of the Harrisburg Senators
Hartford Capitols, a professional basketball team from Hartford, Connecticut, in the Eastern Professional Basketball League
Indianapolis Capitols, a professional American football team from Indianapolis, Indiana, in the Continental Football League
Lincoln Capitols, an indoor arena football (American gridiron) team from Lincoln, Nebraska, in the Indoor Football League
Madison Capitols, a top-tier junior ice hockey team in Middleton, Wisconsin, in the United States Hockey League
Sacramento Capitols, a professional American football team from Sacramento, California, in the Continental Football League
Springfield Capitols, an ice hockey team from Springfield, Illinois, in the All-American Hockey League
Washington Capitols, a professional ice hockey team from District of Columbia, in the National Hockey League
Wisconsin Capitols, a junior ice hockey team in Madison, Wisconsin, in the United States Hockey League
==Transportation==
Capitol Air, originally Capitol International Airways, a 1946–1984 American airline
Capitol Corridor, a passenger train route in California, US, former name Capitols
Chevrolet Series AA Capitol, an American automobile
==Other uses==
Capitouls or capitols, historic chief magistrates of Toulouse, France
|
[
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"The Capitol (Fayetteville, North Carolina)",
"Capitol Broadcasting Company",
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"Capitol Broadcasting Center",
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"Capitol City (disambiguation)",
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"Capitol Theater (disambiguation)",
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"Indianapolis Capitols",
"National Capitol of Colombia",
"Capitol Hill",
"Capitol Hill (disambiguation)",
"Capitol Reef National Park",
"Capitoline Hill",
"Tallahassee Capitols",
"The Capitols",
"Capitol Center (disambiguation)"
] |
5,973 |
Cinema
|
Cinema may refer to:
==Film==
Film or movie, a series of still images that create the illusion of moving image
Film industry, the technological and commercial institutions of filmmaking
Filmmaking, the process of making a film
Movie theater (US), called a cinema elsewhere, a building in which films are shown
==Music==
===Bands===
Cinema (band), a band formed in 1982 by ex-Yes members Alan White & Chris Squire
The Cinema, an American indie pop band
===Albums===
Cinema (Andrea Bocelli album), released 2015
Cinema (The Cat Empire album), released 2010
Cinema (Elaine Paige album), released 1984
Cinema (Nazareth album), or the title song, released 1986
Cinema, a 2009 album by Brazilian band Cachorro Grande
Cinema, a 1990 album by English musician Ice MC (Ian Campbell), or the title song
Cinema, a 2004 album by Portuguese musician Rodrigo Leão
Cinema, a 2010 album by Karsh Kale
Cinema, a 2021 album by The Marías
===Songs===
"Cinema" (Yes song), 1983
"Cinema" (Benny Benassi song), 2011
"Cinema" (Samuel and Francesca Michielin song), 2021
"Cinema", a song by CIX, 2021
"Cinema", a song by Harry Styles from Harry's House
"Cinema", a song by Stray Kids from Mixtape: Dominate
"Cinéma", a song by Paola del Medico, Swiss entry in the Eurovision Song Contest 1980
"Cinema 1", "Cinema 2" and "Cinema 3" by Brockhampton from Saturation III
"Cinema", a commissioned song produced by Ayase
===Labels===
Cinema (record label), a short-lived electronic record label distributed by Capitol Records
|
[
"Paola del Medico",
"Cinema (band)",
"Filmmaking",
"Cinematography",
"The Cinema",
"Cinema (Samuel and Francesca Michielin song)",
"Cinema (record label)",
"Saturation III",
"Film industry",
"Cinema (Andrea Bocelli album)",
"Capitol Records",
"Harry's House",
"Ayase (music producer)",
"Ice MC",
"Cinema (The Cat Empire album)",
"Cinema (Elaine Paige album)",
"The Marías",
"Rodrigo Leão",
"Cinematograph",
"Cachorro Grande",
"Film",
"Sinema (disambiguation)",
"Karsh Kale",
"Cinema (Nazareth album)",
"Cinema (Benny Benassi song)",
"Mixtape: Dominate",
"Cinema (Yes song)",
"Scinema",
"Movie theater",
"Home cinema",
"CIX (band)"
] |
5,974 |
Corundum
|
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. Corundum has two primary gem varieties: ruby and sapphire. Rubies are red due to the presence of chromium, and sapphires exhibit a range of colors depending on what transition metal is present.
Because of corundum's hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost all other minerals. Emery, a variety of corundum with no value as a gemstone, is commonly used as an abrasive on sandpaper and on large tools used in machining metals, plastics, and wood. It is a black granular form of corundum, in which the mineral is intimately mixed with magnetite, hematite, or hercynite.
==Geology and occurrence==
Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes. It also occurs in low-silica igneous syenite and nepheline syenite intrusives. Other occurrences are as masses adjacent to ultramafic intrusives, associated with lamprophyre dikes and as large crystals in pegmatites. The record has since been surpassed by certain synthetic boules.
Corundum for abrasives is mined in Zimbabwe, Pakistan, Afghanistan, Russia, Sri Lanka, and India. Historically it was mined from deposits associated with dunites in North Carolina, US, and from a nepheline syenite in Craigmont, Ontario.
==Synthetic corundum==
In 1837, Marc Antoine Gaudin made the first synthetic rubies by reacting alumina at a high temperature with a small amount of chromium as a colourant.
In 1847, J. J. Ebelmen made white synthetic sapphires by reacting alumina in boric acid.
In 1877, Frenic and Freil made crystal corundum from which small stones could be cut. Frimy and Auguste Verneuil manufactured artificial ruby by fusing and with a little chromium at temperatures above .
In 1903, Verneuil announced that he could produce synthetic rubies on a commercial scale using this flame fusion process.
The Verneuil process allows the production of flawless single-crystal sapphire and ruby gems of much larger size than normally found in nature. It is also possible to grow gem-quality synthetic corundum by flux-growth and hydrothermal synthesis. Because of the simplicity of the methods involved in corundum synthesis, large quantities of these crystals have become available on the market at a fraction of the cost of natural stones.
Synthetic corundum has a lower environmental impact than natural corundum by avoiding destructive mining and conserving resources. However, its production is energy-intensive, contributing to carbon emissions if fossil fuels are used, and involves chemicals that can pose risks.
Apart from ornamental uses, synthetic corundum is also used to produce mechanical parts (tubes, rods, bearings, and other machined parts), scratch-resistant optics, scratch-resistant watch crystals, instrument windows for satellites and spacecraft (because of its transparency in the ultraviolet to infrared range), and laser components. For example, the KAGRA gravitational wave detector's main mirrors are sapphires, and Advanced LIGO considered sapphire mirrors. Corundum has also found use in the development of ceramic armour thanks to its high hardiness.
==Structure and physical properties==
Corundum crystallizes with trigonal symmetry in the space group hexagonal crystal family#Crystal classes| and has the lattice parameters and at standard conditions. The unit cell contains six formula units.
The toughness of corundum is sensitive to surface roughness and crystallographic orientation. It may be 6–7 MPa·m for synthetic crystals,
In the lattice of corundum, the oxygen atoms form a slightly distorted hexagonal close packing, in which two-thirds of the octahedral sites between the oxygen ions are occupied by aluminium ions. The absence of aluminium ions from one of the three sites breaks the symmetry of the hexagonal close packing, reducing the space group symmetry to and the crystal class to trigonal. The structure of corundum is sometimes described as a pseudohexagonal structure.
The Young's modulus of corundum (sapphire) has been reported by many different sources with values varying between 300 and 500 GPa, but a commonly cited value used for calculations is 345 GPa. The Young's modulus is temperature dependent, and has been reported in the [0001] direction as 435 GPa at 323 K and 386 GPa at 1,273 K. and the bulk modulus is 240 GPa.
The hardness of corundum measured by indentation at low loads of 1-2 N has been reported as 22-23 GPa in major crystallographic planes: (0001) (basal plane), (100) (rhombohedral plane), (110) (prismatic plane), and (102). The hardness can drop significantly under high indentation loads. The drop with respect to load varies with the crystallographic plane due to the difference in crack resistance and propagation between directions. One extreme case is seen in the (0001) plane, where the hardness under high load (~1 kN) is nearly half the value under low load (1-2 N).
===Structure type===
Because of its prevalence, corundum has also become the name of a major structure type (corundum type) found in various binary and ternary compounds.
|
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"carbon",
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"Naxos",
"Oxide mineral",
"marble",
"Gemstone",
"Verneuil process",
"transparency and translucency"
] |
5,976 |
Capoeira
|
Capoeira () is an Afro-Brazilian martial art and game that includes elements of dance, acrobatics, music and spirituality.
It is known for its acrobatic and complex manoeuvres, often involving hands on the ground and inverted kicks. It emphasizes flowing movements rather than fixed stances; the ginga, a rocking step, is usually the focal point of the technique. Though often said to be a martial art disguised as a dance, capoeira served not only as a form of self defense, but also as a way to maintain spirituality and culture.
Capoeira has been practiced among Black Brazilians for centuries. The date of its creation is unknown, but it was first mentioned in a judicial document under the name Capoeiragem in 1789, as "the gravest of crimes". In the 19th century, a street fighting style called capoeira carioca was developed. It was repeatedly outlawed and its performers persecuted, and it was declared totally illegal and banned in 1890. In the early 1930s, Mestre Bimba reformed traditional capoeira and developed the capoeira regional style. The government came to see capoeira as a socially acceptable sport. In 1941, Mestre Pastinha later founded his school where he cultivated the traditional capoeira Angola, distinguishing it from reformed capoeira and the "national sport" approach.
In the late 1970s, trailblazers such as Mestre Acordeon started bringing capoeira to the US and Europe, helping the art become internationally recognized and practiced. On 26 November 2014, capoeira was granted a special protected status as intangible cultural heritage by UNESCO.
Martial arts from the African diaspora similar to capoeira include knocking and kicking from the Sea Islands, and ladya from Martinique, both of which likely originate from Engolo.
== Name ==
In the past, many participants used the name angola or the term brincar de angola ("playing angola") for this art. In a narrower sense, capoeiragem meant a set of fighting skills. The term jogo de capoeira (capoeira game) is used to describe the art in the performative context.
Although debated, the most widely accepted origin of the word capoeira comes from the Tupi words ka'a ("forest") paũ ("round"), referring to the areas of low vegetation in the Brazilian interior where fugitive slaves would hide.
==History==
In the past, some participants used the name angola or the term brincar de angola ("playing angola") for this art. In formal documents, capoeira was known as "capoeiragem", with a practitioner being known as a "capoeira". Gradually, the art became known as capoeira with a practitioner being called a capoeirista. Still, some authors believe there were more ancestors besides engolo. However, at the core of capoeira we find techniques developed in engolo, including crescent kicks, push kicks, sweeps, handstands, cartwheels, evasions and even the iconic Meia lua de compasso, scorpion kick and L-kick.
Modern capoeira comes from Bahia, and was codified by mestre Bimba and mestre Pastinha, in regional and angola style. Despite their significant differences, both mestres introduced major innovations — they moved training and rodas away from the street, instituted the academia, prescribed uniforms, started to teach women and presented capoeira to a broader audiences.
==Techniques==
Capoeira is a fast and versatile martial art that is historically focused on fighting when outnumbered or at a technological disadvantage. The style emphasizes using the lower body to kick, sweep and take down their aggressors, using the upper body to assist those movements and occasionally attack as well. It features a series of complex positions and body postures that are meant to get chained in an uninterrupted flow, to strike, dodge and move without breaking motion, conferring the style with a characteristic unpredictability and versatility.
The ginga (literally "rocking back and forth"; "to swing") is the fundamental movement in capoeira, important both for attacking and defending oneself. It has two main objectives: one is to keep the capoeirista in a state of constant motion, preventing them from being a still and easy target; and the other, using also fakes and feints, is to mislead, fool or trick the opponent, leaving them open to attack.
The attacks in the capoeira should be done when opportunity arises, and though they can be preceded by feints or pokes, they must be precise and decisive, like a direct kick to the head, face or a vital body part, or a strong takedown. Most capoeira attacks are made with the legs, like direct or swirling kicks, rasteiras (leg sweeps), tesouras or knee strikes. Elbow strikes, punches and other forms of takedowns complete the main list. The head strike is a very important counter-attack move.
The defense is based on the principle of non-resistance, meaning avoiding an attack using evasive moves instead of blocking it. Avoids are called esquivas, which depend on the direction of the attack and intention of the defender, and can be done standing or with a hand leaning on the floor. A block should only be made when the esquiva is completely non-viable. This fighting strategy allows quick and unpredictable counterattacks, the ability to focus on more than one adversary and to face empty-handed an armed adversary.
A series of rolls and acrobatics (like the cartwheels called aú or the transitional position called negativa) allows the capoeirista to quickly overcome a takedown or a loss of balance, and to position themselves around the aggressor to lay up for an attack. It is this combination of attacks, defense and mobility that gives capoeira its perceived "fluidity" and choreography-like style.
==Weapons==
Through most of its history in Brazil, capoeira commonly featured weapons and weapon training, given its street fighting nature. Capoeiristas usually carried knives and bladed weapons with them, and the berimbau could be used to conceal those inside, or even to turn itself into a weapon by attaching a blade to its tip. The knife or razor was used in street rodas and/or against openly hostile opponents, and would be drawn quickly to stab or slash. Other hiding places for the weapons included hats and umbrellas.
Mestre Bimba included in his teachings a curso de especialização or "specialization course", in which the pupils would be taught defenses against knives and guns, as well as the usage of knife, straight razor, scythe, club, chanfolo (double-edged dagger), facão (facón or machete) and tira-teima (cane sword).
This weapon training is almost completely absent in current capoeira teachings, but some groups still practice the use of razors for ceremonial usage in the rodas.
==As a game==
In Bantu culture, the Nkhumbi term ochimama encapsulates the overlapping meanings of game, dance, and tradition. This overlap is also found in Afro-Brazilian folklore, where many similar forms of expression are called brincadeiras (games). The game does not focus on knocking down or defeating opponents, but rather on body dialogue and highlighting skills.
===Roda===
The roda (pronounced ) is a circle formed by capoeiristas and capoeira musical instruments, where every participant sings the typical songs and claps their hands following the music. Two capoeiristas enter the roda and play the game according to the style required by the musical rhythm. The game finishes when one of the musicians holding a berimbau determines it, when one of the capoeiristas decides to leave or call the end of the game, or when another capoeirista interrupts the game to start playing, either with one of the current players or with another capoeirista.
In a roda every cultural aspect of capoeira is present, not only the martial side. Aerial acrobatics are common in a presentation roda, while not seen as often in a more serious one. Takedowns, on the other hand, are common in a serious roda but rarely seen in presentations.
===Batizado===
The batizado (lit. baptism) is a ceremonial roda where new students will get recognized as capoeiristas and earn their first graduation. Also more experienced students may go up in rank, depending on their skills and capoeira culture. In Mestre Bimba's Capoeira Regional, batizado was the first time a new student would play capoeira following the sound of the berimbau.
Students enter the roda against a high-ranked capoeirista (such as a teacher or master) and normally the game ends with the student being taken down. In some cases the more experienced capoeirista can judge the takedown unnecessary. Following the batizado the new graduation, generally in the form of a cord, is given.
Traditionally, the batizado is the moment when the new practitioner gets or formalizes their apelido (nickname). This tradition was created back when capoeira practice was considered a crime. To avoid having problems with the law, capoeiristas would present themselves in the capoeira community only by their nicknames.
===Chamada===
Chamada means 'call' and can happen at any time during a roda where the rhythm angola is being played. It happens when one player, usually the more advanced one, calls their opponent to a dance-like ritual. The opponent then approaches the caller and meets them to walk side by side. After it both resume normal play.
While it may seem like a break time or a dance, the chamada is actually both a trap and a test, as the caller is just watching to see if the opponent will let his guard down so she can perform a takedown or a strike. It is a critical situation, because both players are vulnerable due to the close proximity and potential for a surprise attack. It's also a tool for experienced practitioners and masters of the art to test a student's awareness and demonstrate when the student left herself open to attack.
The use of the chamada can result in a highly developed sense of awareness and helps practitioners learn the subtleties of anticipating another person's hidden intentions. The chamada can be very simple, consisting solely of the basic elements, or the ritual can be quite elaborate including a competitive dialogue of trickery, or even theatric embellishments.
==Music==
Music is integral to capoeira. It sets the tempo and style of game that is to be played within the roda. Typically the music is formed by instruments and singing. Rhythms (toques), controlled by a typical instrument called berimbau, differ from very slow to very fast, depending on the style of the roda.
===Instruments===
Capoeira instruments are disposed in a row called bateria. It is traditionally formed by three berimbaus, two pandeiros, three atabaques, one agogô and one ganzá, but this format may vary depending on the capoeira group's traditions or the roda style. (https://draculinho.wordpress.com/tag/brazil/)
The berimbau is the leading instrument, determining the tempo and style of the music and game played. Two low-pitch berimbaus (called berra-boi and médio) form the base and a high-pitch berimbau (called viola) makes variations and improvisations. The other instruments must follow the berimbau's rhythm, free to vary and improvise a little, depending upon the capoeira group's musical style.
As the capoeiristas change their playing style significantly following the toque of the berimbau, which sets the game's speed, style and aggressiveness, it is truly the music that drives a capoeira game.
=== Songs ===
Many of the songs are sung in a call and response format while others are in the form of a narrative. Capoeiristas sing about a wide variety of subjects. Some songs are about history or stories of famous capoeiristas. Other songs attempt to inspire players to play better. Some songs are about what is going on within the roda. Sometimes the songs are about life or love lost. Others have lighthearted and playful lyrics.
There are four basic kinds of songs in capoeira, the Ladaínha, Chula, Corrido and Quadra. The Ladaínha is a narrative solo sung only at the beginning of a roda, often by a mestre (master) or most respected capoeirista present. The solo is followed by a louvação, a call and response pattern that usually thanks God and one's master, among other things. Each call is usually repeated word-for-word by the responders. The Chula is a song where the singer part is much bigger than the chorus response, usually eight singer verses for one chorus response, but the proportion may vary. The Corrido is a song where the singer part and the chorus response are equal, normally two verses by two responses. Finally, the Quadra is a song where the same verse is repeated four times, either three singer verses followed by one chorus response, or one verse and one response.
Capoeira songs can talk about virtually anything, being it about a historical fact, a famous capoeirista, trivial life facts, hidden messages for players, anything. Improvisation is very important also, while singing a song the main singer can change the music's lyrics, telling something that's happening in or outside the roda.
== Philosophy ==
=== Malícia (malice) ===
The basic term of capoeira philosophy is malícia (malice). One aspect of malicia consists of deceiving the opponent into thinking that you are going to execute a certain move when in fact you are going to do something completely different. There is an example of malicia of Besouro who once fell to the ground during a game, crying like a woman and begging for mercy. Mestre João Pequeno claimed that he teaches his students how to play capoeira, but they should learn malícia for themselves since it cannot be taught.
The meaning of malícia in capoeira has expanded over time to cunning, suspicion, alertness, readiness, flexibility, and adaptation. Basically, it is the capacity to understand someone's intentions and making use of this understanding to misdirect someone as to your next move. In the contemporary capoeira, this is done good-naturedly, contrary to what the word may suggest.
A popular Brazilian saying, "Malandro demais se atrapalha" means that when one tries to be too clever or smart, instead of confusing his opponent, he confuses himself.
==Spirituality==
Spirituality in capoeira is shaped under the influence of various African beliefs. Some important concepts of candomblé, such as dendé and axé, which refer to different conceptions of energy, have become common among capoeiristas.
=== Bantu culture ===
Dr Maya Talmon-Chvaicer suggests that capoeira should be explained in Bantu terms. For the African slaves, capoeira was a social expression that incorporated all the basic African elements: circle, dance, music, rituals and symbols. It also contains all the ingredients of a game from the Kongolese perspective: a means to train and prepare for life, providing the experience needed to strengthen the body and the soul.
Within the Bantu culture, the circle carries profound symbolism.
A major means of communication with the ancestors is music. Musical instruments play a pivotal role in bridging the realms of the living, the deceased, and the gods. This explains why African dances customarily commence by paying homage to the primary instrument, often through kneeling or bowing before it. This practice of appeasement and seeking divine assistance from the gods is mirrored in the capoeira tradition of kneeling before the berimbau during the ladainha.
One of the capoeira ritual is performing the "au" at the beginning of the game. This act symbolizes a profound transition in Kongolese religion, where touching the ground with hands while feet are up in the air signifies the player crosses over to other worlds.
Capoeira has been additionally shaped by the cosmic worldview of candomblé, an Afro-Brazilian religion that has engaged with various manifestations of natural energies. The capoeira player in past usually had his orixá or santo (patron saint) as Ogum (the Warrior) or Oxóssi (the Hunter).
=== Mandinga (magic) ===
Capoeira holds a core of mandinga, which can be translated as a magic, sorcery, witchcraft. Mandinga suggests an understanding of fundamental natural forces and their utilization through magic rituals to some extent. In the past, capoeiristas used protective amulets and performed specific rituals to ensure their safety. Same players "do their mandinga" before the game by drawing magical symbols on the ground with their fingers.
Some magic elements in capoeira are clear and familiar, while others have become obscure over time. Folklorist Edison Carneiro noted that the ladainha, sung before entering the capoeira circle, invokes the gods, adding a touch of mysticism to the ritual. Actions like touching the ground symbolize drawing signs in the dust, and gestures such as kissing hands, crossing oneself, and prayer are reminders of long-forgotten traditions, the Bantus' prayer for divine blessings, aid, and bravery in battle.
Mandinga is also a certain esthetic, where the game is expressive and sometimes theatrical, especially in the Angola style. An advanced capoeira player is sometimes referred to as a mandingueiro, someone who embodies mandinga.
The roots of the term mandingueiro would be a person who had the magic ability to avoid harm due to protection from the Orixás. Alternately the word mandinga originates from the name of Mandinka people.
== Styles ==
Determining styles in capoeira is difficult, since there was never a unity in the original capoeira, or a teaching method before the decade of 1920. However, a division between two styles and a sub-style is widely accepted.
The base of capoeira regional is the original capoeira without many of the aspects that were impractical in a real fight, with less subterfuge and more objectivity. Training focuses mainly on attack, dodging and counter-attack, giving high importance to precision and discipline. Bimba also added a few moves from other arts, notably the batuque, an old street fight game invented by his father. Use of jumps or aerial acrobatics stay to a minimum, since one of its foundations is always keeping at least one hand or foot firmly attached to the ground.
Capoeira Regional also introduced the first ranking method in capoeira. Regional had three levels: calouro (freshman), formado (graduated) and formado especializado (specialist). After 1964, when a student completed a course, a special celebration ceremony occurred, ending with the teacher tying a silk scarf around the capoeirista's neck.
The traditions of roda and capoeira game were kept, being used to put into use what was learned during training. The disposition of musical instruments, however, was changed, being made by a single berimbau and two pandeiros.
The Luta Regional Baiana soon became popular, finally changing capoeira's bad image. Mestre Bimba made many presentations of his new style, but the best known was the one made at 1953 to Brazilian president Getúlio Vargas, where the president would say: "A Capoeira é o único esporte verdadeiramente nacional" (Capoeira is the only truly national sport).
=== Capoeira carioca ===
Capoeira carioca was a street fighting version of capoeira that existed in Rio de Janeiro during the 19th century, used by gangs. In capoeira carioca, all available means were used, including various types of weapons, such as knives, straight razors, clubs and machetes. Capoeira from this period is also known as capoeiragem. The widespread violent capoeira practice in Rio led to a nationwide ban on capoeira. After the ban in 1890 and the subsequent mass arrests of capoeira gang members, this version of capoeira is generally extinct.
The main reformators and proponents of this fighting-oriented capoeira were Mestre Sinhozinho and Mestre Zuma.
=== Capoeira Contemporânea ===
Capoeira flourished in the city of São Paulo since the 1960s. Mestre Suassuna was prominent figure throughout this period. Mestre Canjiquinha played important role in shaping the capoeira style that began to emerge in São Paulo during the 1960s. This evolving style, which emerged in the 1960s and 1970s, drew from both Regional and Angola styles while maintaining its distinct characteristics. The majority of modern practitioners affirm to be neither Angola nor Regional, emphasizing that "there is only one capoeira".
This new capoeira incorporated not only berimbaus and pandeiros but also atabaque and agogô into its musical ensemble. In contrast to Bimba's preference for quadras, these modern rodas typically commenced with ladainhas. The games in these rodas often featured a fast and upright style, even though they might start with an Angola toque and a slower game.
Nowadays the label Contemporânea applies to any capoeira group who don't follow Regional or Angola styles, even the ones who mix capoeira with other martial arts. Some notable groups whose style cannot be described as either Angola or Regional but rather "a style of their own", include Senzala de Santos, Cordão de Ouro and Abada. In the case of Cordão de Ouro, the style may be described as "Miudinho", a low and fast-paced game, while in Senzala de Santos the style may described simply as "Senzala de Santos", an elegant, playful combination of Angola and Regional.
== Ranks ==
Because of its origin, capoeira never had unity or a general agreement. Ranking or graduating system follows the same path, as there never existed a ranking system accepted by most of the masters. That means graduation style varies depending on the group's traditions. The most common modern system uses colored ropes, called corda or cordão, tied around the waist. Some masters use different systems, or even no system at all. In a substantial number of groups (mainly of the Angola school) there is no visible ranking system. There can still be several ranks: student, treinel, professor, contra-mestre and mestre, but often no cordas (belts).
There are many entities (leagues, federations and association) with their own graduation system. The most usual is the system of the Confederação Brasileira de Capoeira (Brazilian Capoeira Confederation), which adopts ropes using the colors of the Brazilian flag, green, yellow, blue and white. However, the Confederação Brasileira de Capoeira is not widely accepted as the capoeira's main representative.
=== Brazilian Capoeira Confederation system ===
Source:
==== Children's system (3 to 14 years) ====
1st stage: Iniciante (Beginner) - No color
2nd stage: Batizado (Baptized) - Green/Light Grey
3rd stage: Graduado (Graduated) - Yellow/Light Grey
4th stage: Adaptado (Adept) - Blue/Light Grey
5th stage: Intermediário (Intermediary) - Green/YellowLight Grey
6th stage: Avançado (Advanced) - Green/Blue/Light Grey
7th stage: Estagiário (Trainee) - Yellow/Green/Blue/Light Grey
==== Adult system (above 15) ====
8th stage: Iniciante (Beginner) - No color
9th stage: Batizado (Baptized) - Green
10th stage: Graduado (Graduated) - Yellow
11th stage: Adaptado (Adept) - Blue
12th stage: Intermediário (Intermediary) - Green
13th stage: Avançado (Advanced) - Green/Blue
14th stage: Estagiário (Trainee) - Yellow/Blue
==== Instructors' system ====
15th stage: Formado (Graduated) - Yellow/Green/Blue
16th stage: Monitor (Monitor) - White/Green
17th stage: Instrutor (Instructor) - White/Yellow
18th stage: Contramestre (Foreman) - White/Blue
19th stage: Mestre (Master) - White
=== ABADÁ - Capoeira system ===
Many Capoeira schools use a system taken from Abadá-Capoeira.
ABADÁ has a graduated cord system using colors that refer symbolically to nature and reflect the level of practice. The cord system does not so much reflect the practitioner's level of skill as much as their progress on their individual path as a member of the ABADÁ community. The cord system as outlined by Arte Capoeira Center – ABADÁ Capoeira is as follows.
=== Adult Graduation System ===
== Related activities ==
Even though those activities are strongly associated with capoeira, they have different meanings and origins.
=== Samba de roda ===
Performed by many capoeira groups, samba de roda is a traditional Brazilian dance and musical form that has been associated with capoeira for many decades. The orchestra is composed by pandeiro, atabaque, berimbau-viola (high pitch berimbau), chocalho, accompanied by singing and clapping. Samba de roda is considered one of the primitive forms of modern Samba.
=== Maculelê ===
Originally the Maculelê is believed to have been an indigenous armed fighting style, using two sticks or a machete. Nowadays it's a folkloric dance practiced with heavy Brazilian percussion. Many capoeira groups include Maculelê in their presentations.
=== Puxada de rede ===
Puxada de Rede is a Brazilian folkloric theatrical play, seen in many capoeira performances. It is based on a traditional Brazilian legend involving the loss of a fisherman in a seafaring accident.
== Combat capoeira and MMA ==
Combat capoeira, often referred to as rough capoeira (capoeira dura), places a primary emphasis on combat. It is commonly observed in ring competitions and street rodas, and sometimes even in graduations within certain groups.
Several capoeira fighters have gained national reputation, including Mestre King Kong from Salvador, Mestre Maurão from São Paulo, and King from Rio de Janeiro (formerly associated with Abadá). They advocate for capoeiristas to be skilled in playing intense games to ensure that the art retains its combat effectiveness.
Capoeira fights have, on occasion, resulted in severe injuries and even fatalities, as seen in Petrópolis in 1996. The most suitable context for combat-focused capoeira appears to be the ring, where predetermined fighting rules provide clarity. In the tradition of Ciriaco, Sinhozinho, Bimba, and Arthur Emídio, contemporary capoeira fighters have expanded their training by incorporating various martial arts disciplines, including ju-jitsu, boxing, and taekwondo.
Even Brazilian mixed martial arts champions like Marco Ruas acknowledge the significance of capoeira in their training. The use of capoeira techniques in free-style competitions shows to what extent the art still provides essential fighting skills.
== Notable practitioners ==
Besouro Mangangá
Anibal Burlamaqui
Mestre Sinhozinho
Mestre Bimba
Mestre Pastinha
Mestre Waldemar
Mestre Gato Preto
Mestre Cobrinha Verde
Mestre João Grande
Mestre João Pereira dos Santos
Mestre Norival Moreira de Oliveira
Mestre Moraes
Mestre Cobra Mansa
Junior dos Santos
Wesley Snipes
Mark Dacascos
Anderson Silva
Lateef Crowder dos Santos
Jose Aldo
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5,980 |
Carbon sink
|
A carbon sink is a natural or artificial carbon sequestration process that "removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere". Soil is an important carbon storage medium. Much of the organic carbon retained in the soil of agricultural areas has been depleted due to intensive farming. Blue carbon designates carbon that is fixed via certain marine ecosystems. Coastal blue carbon includes mangroves, salt marshes and seagrasses. These make up a majority of ocean plant life and store large quantities of carbon. Deep blue carbon is located in international waters and includes carbon contained in "continental shelf waters, deep-sea waters and the sea floor beneath them".
For climate change mitigation purposes, the maintenance and enhancement of natural carbon sinks, mainly soils and forests, is important. In the past, human practices like deforestation and industrial agriculture have depleted natural carbon sinks. This kind of land use change has been one of the causes of climate change.
== Definition ==
In the context of climate change and in particular mitigation, a sink is defined as "Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere".
In the case of non- greenhouse gases, sinks need not store the gas. Instead they can break it down into substances that have a reduced effect on global warming. For example, nitrous oxide can be reduced to harmless N2.
Related terms are "carbon pool, reservoir, sequestration, source and uptake". A carbon pool is all the places where carbon can be stored (for example the atmosphere, oceans, soil, plants, and fossil fuels).
Photosynthesis by terrestrial plants with grass and trees allows them to serve as carbon sinks during growing seasons.
Absorption of carbon dioxide by the oceans via solubility and biological pumps.
Artificial carbon sinks are those that store carbon in building materials or deep underground (geologic carbon sequestration). No major artificial systems remove carbon from the atmosphere on a large scale yet.
Public awareness of the significance of sinks has grown since passage of the 1997 Kyoto Protocol, which promotes their use as a form of carbon offset.
== Natural carbon sinks ==
=== Soils ===
Soils represent a short to long-term carbon storage medium and contain more carbon than all terrestrial vegetation and the atmosphere combined. Plant litter and other biomass including charcoal accumulates as organic matter in soils, and is degraded by chemical weathering and biological degradation. More recalcitrant organic carbon polymers such as cellulose, hemi-cellulose, lignin, aliphatic compounds, waxes and terpenoids are collectively retained as humus.
Organic matter tends to accumulate in litter and soils of colder regions such as the boreal forests of North America and the Taiga of Russia. Leaf litter and humus are rapidly oxidized and poorly retained in sub-tropical and tropical climate conditions due to high temperatures and extensive leaching by rainfall. Areas, where shifting cultivation or slash and burn agriculture are practiced, are generally only fertile for two to three years before they are abandoned. These tropical jungles are similar to coral reefs in that they are highly efficient at conserving and circulating necessary nutrients, which explains their lushness in a nutrient desert.
Grasslands contribute to soil organic matter, stored mainly in their extensive fibrous root mats. Due in part to the climatic conditions of these regions (e.g., cooler temperatures and semi-arid to arid conditions), these soils can accumulate significant quantities of organic matter. This can vary based on rainfall, the length of the winter season, and the frequency of naturally occurring lightning-induced grass-fires. While these fires release carbon dioxide, they improve the quality of the grasslands overall, in turn increasing the amount of carbon retained in the humic material. They also deposit carbon directly into the soil in the form of biochar that does not significantly degrade back to carbon dioxide.
Much organic carbon retained in many agricultural areas worldwide has been severely depleted due to intensive farming practices. Since the 1850s, a large proportion of the world's grasslands have been tilled and converted to croplands, allowing the rapid oxidation of large quantities of soil organic carbon. Methods that significantly enhance carbon sequestration in soil are called carbon farming. They include for example no-till farming, residue mulching, cover cropping, and crop rotation.
=== Forests ===
=== Deep ocean, tidal marshes, mangroves and seagrasses ===
== Enhancing natural carbon sinks ==
===Purpose in the context of climate change===
=== Carbon sequestration techniques in oceans ===
To enhance carbon sequestration processes in oceans the following technologies have been proposed but none have achieved large scale application so far: Seaweed farming, ocean fertilisation, artificial upwelling, basalt storage, mineralization and deep sea sediments, adding bases to neutralize acids. The idea of direct deep-sea carbon dioxide injection has been abandoned.
== Artificial carbon sinks ==
===Geologic carbon sequestration===
=== Wooden buildings ===
Broad-base adoption of mass timber and their role in substituting steel and concrete in new mid-rise construction projects over the next few decades has the potential to turn timber buildings into carbon sinks, as they store the carbon dioxide taken up from the air by trees that are harvested and used as mass timber. This could result in storing between 10 million tons of carbon per year in the lowest scenario and close to 700 million tons in the highest scenario. For this to happen, the harvested forests would need to be sustainably managed and wood from demolished timber buildings would need to be reused or preserved on land in various forms.
|
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5,981 |
Charles Tupper
|
Sir Charles Tupper, 1st Baronet (July 2, 1821 – October 30, 1915) was a Canadian Father of Confederation who served as the sixth prime minister of Canada from May 1 to July 8, 1896. As the premier of Nova Scotia from 1864 to 1867, he led Nova Scotia into Confederation. He briefly served as the Canadian prime minister, from seven days after parliament had been dissolved, until he resigned on July 8, 1896, following his party's loss in the 1896 Canadian federal election. He is the only medical doctor to have ever held the office of prime minister of Canada, and his 69-day tenure as prime minister is the shortest in Canadian history.
Tupper was born in Amherst, Nova Scotia, to the Rev. Charles Tupper and Miriam Lockhart. He was educated at Horton Academy, Wolfville, Nova Scotia, and studied medicine at the University of Edinburgh Medical School, graduating MD in 1843. By the age of 22 he had handled 116 obstetric cases. He practiced medicine periodically throughout his political career (and served as the first president of the Canadian Medical Association). He entered Nova Scotian politics in 1855 as a protégé of James William Johnston. During Johnston's tenure as premier of Nova Scotia in 1857–1859 and 1863–1864, Tupper served as provincial secretary. Tupper replaced Johnston as premier in 1864. As premier, he established public education in Nova Scotia and expanded Nova Scotia's railway network in order to promote industry.
By 1860, Tupper supported a union of all the colonies of British North America. Believing that immediate union of all the colonies was impossible, in 1864, he proposed a Maritime Union. However, representatives of the Province of Canada asked to be allowed to attend the meeting in Charlottetown scheduled to discuss Maritime Union in order to present a proposal for a wider union, and the Charlottetown Conference thus became the first of the three conferences that secured Canadian Confederation. Tupper also represented Nova Scotia at the other two conferences, the Quebec Conference (1864) and the London Conference of 1866. In Nova Scotia, Tupper organized a Confederation Party to combat the activities of the Anti-Confederation Party organized by Joseph Howe and successfully led Nova Scotia into Confederation.
Following the passage of the British North America Act in 1867, Tupper resigned as premier of Nova Scotia and began a career in federal politics. He held multiple cabinet positions under Prime Minister John A. Macdonald, including President of the Queen's Privy Council for Canada (1870–1872), Minister of Inland Revenue (1872–1873), Minister of Customs (1873–1874), Minister of Public Works (1878–1879), and Minister of Railways and Canals (1879–1884). Initially groomed as Macdonald's successor, Tupper had a falling-out with Macdonald, and by the early 1880s, he asked Macdonald to appoint him as Canadian High Commissioner to the United Kingdom. Tupper took up his post in London in 1883, and would remain High Commissioner until 1895, although in 1887–1888, he served as Minister of Finance without relinquishing the High Commissionership.
In 1895, the government of Mackenzie Bowell floundered over the Manitoba Schools Question; as a result, several leading members of the Conservative Party of Canada demanded the return of Tupper to serve as prime minister. Tupper accepted this invitation and returned to Canada, becoming prime minister in May 1896. Just before he was sworn in as prime minister, the 1896 federal election was called, in which his party lost to Wilfrid Laurier and the Liberals. Tupper served as leader of the Opposition from July 1896 until he resigned in February 1901, just months after his second defeat at the polls in 1900. He returned to London, England, where he lived until his death in 1915 and was buried back in Halifax, Nova Scotia. He was the last surviving Canadian father of Confederation. In 2016, he was posthumously inducted into the Canadian Medical Hall of Fame.
==Early life, 1821–1855==
Charles Tupper Jr. was born on July 2, 1821, in Amherst, Nova Scotia, to Charles Tupper Sr. and Miriam Lowe, Lockhart. He was a descendant of Richard Warren, a Mayflower Pilgrim who signed the Mayflower Compact. Charles Tupper Sr. (1794–1881) was the co-pastor of the local Baptist church. He had been ordained as a Baptist minister in 1817, and was editor of Baptist Magazine 1832–1836. He was an accomplished Biblical scholar, and published Scriptural Baptism (Halifax, Nova Scotia, 1850) and Expository Notes on the Syriac Version of the Scriptures.
Beginning in 1837, at age 16, Tupper attended Horton Academy in Wolfville, Nova Scotia, where he learned Latin, Greek, and some French.
In 1883, Tupper convinced William Ewart Gladstone's government to exempt Canadian cattle from the general British ban on importing American cattle by demonstrating that Canadian cattle were free of disease. The Conservatives captured only about half of the seats in English Canada, while Laurier's Liberals won a landslide victory in Quebec, where Tupper's reputation as an ardent imperialist was a major handicap. He was the last of the original Fathers of Confederation to die, and had lived the longest life of any Canadian prime minister, at 94 years, four months.]]
Tupper will be most remembered as a Father of Confederation, and his long career as a federal cabinet minister, rather than his brief time as prime minister. As the Premier of Nova Scotia from 1864 to 1867, he led Nova Scotia into Confederation and persuaded Joseph Howe to join the new federal government, bringing an end to the anti-Confederation movement in Nova Scotia.
In their 1999 study of the Canadian Prime Ministers through Jean Chrétien, J.L. Granatstein and Norman Hillmer included the results of a survey of Canadian historians ranking the Prime Ministers. Tupper ranked No. 16 out of the 20 up to that time, due to his extremely short tenure in which he was unable to accomplish anything of significance. Historians noted that despite Tupper's elderly age, he showed a determination and spirit during his brief time as prime minister that almost beat Laurier in the 1896 election.
Mount Tupper in the Canadian Rockies and the Sir Charles Tupper Building in Ottawa are named for him. The Sir Charles Tupper Medical Building is the central building of the Dalhousie Medical School in Halifax, Nova Scotia.
== Facility naming ==
Sir Charles Tupper Secondary School in Vancouver, British Columbia
Sir Charles Tupper School in Halifax
Sir Charles Tupper Medical Building at the Faculty of Medicine, Dalhousie University
Sir Charles Tupper Building in Ottawa
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"Intercolonial Railway of Canada",
"Governor of Nova Scotia",
"George-Étienne Cartier",
"John Hamilton-Gordon, 1st Marquess of Aberdeen and Temair",
"Vancouver",
"Charles Hibbert Tupper",
"Catholic schools",
"9th Canadian Parliament",
"Provincial Secretary",
"Prince Edward Island",
"1st Canadian Parliament",
"Spain",
"Tupper Baronetcy",
"6th Canadian Ministry",
"Cape Breton (federal electoral district)",
"premier of Nova Scotia",
"Anglican",
"The Right Honourable",
"Nova Scotia House of Assembly",
"protectionism",
"Oxfordshire",
"European continent",
"Mark Carney",
"imperialist",
"Quebec lieutenant",
"Protestants",
"filibuster",
"Mackenzie Bowell",
"Capitalism",
"Richard William Scott",
"Sir William Williams, 1st Baronet, of Kars",
"Canada",
"Maritime Union",
"Richard Graves MacDonnell",
"public education",
"Premier of the Province of Canada",
"Party platform",
"Joseph Howe",
"Annapolis Royal, Nova Scotia",
"Intercolonial Railway",
"Charles James Townshend",
"London Conference of 1866",
"Monarchy of the United Kingdom",
"natural resources",
"J.L. Granatstein",
"President of the Queen's Privy Council for Canada",
"Thomas John Murray",
"John O'Connor (Canadian politician)",
"Manitoba Schools Act",
"Hector-Louis Langevin",
"Alexander Tilloch Galt",
"Baptist church",
"Cumberland (federal electoral district)",
"American Senate",
"Father of Confederation",
"caucus",
"Ancient Greek",
"Pacific Ocean",
"Liberal-Conservative Party",
"Government bond",
"North-West Rebellion",
"Maritimes",
"Imperial unit",
"Colonial and Indian Exhibition",
"Mount Tupper",
"Quebec Conference, 1864",
"Judicial Committee of the Privy Council",
"Conservative Party of Canada (historical)",
"Cumberland County, Nova Scotia",
"Disallowance and reservation in Canada",
"Thomas-Louis Connolly",
"1882 Canadian federal election",
"Charlottetown",
"Nova Scotia Railway",
"6th Canadian Parliament",
"common schools",
"American-Canadian relations",
"Nineteenth Century (periodical)",
"British Empire League",
"Massey Hall",
"James William Johnston",
"unconstitutional",
"Halifax, Nova Scotia",
"Premier of Nova Scotia",
"running rights",
"Welland Canal",
"Saint Lawrence Seaway",
"plenipotentiary",
"iron and steel industry",
"state funeral",
"House of Commons of Canada",
"Treaty of 1818",
"George Stephen, 1st Baron Mount Stephen",
"prime minister of the United Kingdom",
"Manitoba Act",
"Wilfrid Laurier",
"New Brunswick Premier",
"Amherst, Nova Scotia",
"Hiram Blanchard",
"guarantee",
"Province of Canada",
"1900 Canadian federal election",
"St. Lawrence Seaway",
"Conservative Party of Canada (1867–1942)",
"1878 Canadian federal election",
"4th Canadian Parliament",
"Nova Scotia Liberal Party",
"Obstetrics",
"Truro, Nova Scotia",
"Windsor, Nova Scotia",
"British North American",
"Edinburgh",
"Bering Sea Dispute",
"Victor Albert Long",
"free trade",
"Bering Sea",
"1872 Canadian federal election",
"William Johnston Tupper",
"Wolfville, Nova Scotia",
"Quebec",
"St. John's Cemetery, Halifax",
"French Canadian",
"Federalism",
"Pictou (federal electoral district)",
"English Canada",
"Isaac Burpee",
"Union (American Civil War)",
"Companion in The Most Honourable Order of the Bath",
"Dalhousie Medical School",
"Thomas Mayne Daly",
"Baronetage of the United Kingdom",
"Walter Humphries Montague",
"Royal Navy",
"U.S. Secretary of State",
"Physician",
"Orient",
"John Henry Pope",
"David MacKeen",
"Dalhousie College",
"Colony of Newfoundland",
"Adams George Archibald",
"Oxford",
"Canadian federal election",
"List of Canadian High Commissioners to the United Kingdom",
"Dalton McCarthy",
"Imperial Federation League",
"Norman Hillmer",
"immigration to Canada",
"Ottawa",
"London",
"Industrialisation",
"Patrons of Industry",
"Imperial Federation",
"Government budget deficit",
"Sandford Fleming",
"Atlantic Ocean",
"Robert Borden",
"Queen Victoria",
"Charlottetown Conference",
"List of Canadian Ministers of Railways and Canals",
"Alexander Mackenzie (politician)",
"free trade agreement",
"High Commissioner (Commonwealth)",
"1891 Canadian federal election",
"John Sparrow David Thompson",
"Robert Gascoyne-Cecil, 3rd Marquess of Salisbury",
"Fathers of Confederation",
"prime minister of Canada",
"George Eulas Foster",
"Hector Louis Langevin",
"Donald Smith, 1st Baron Strathcona and Mount Royal",
"Latin",
"Pictou Landing, Nova Scotia",
"Benjamin Disraeli",
"William Ewart Gladstone",
"2nd Canadian Ministry",
"8th Canadian Parliament",
"1896 Canadian federal election",
"Minister of Inland Revenue (Canada)",
"fisheries",
"memoirs",
"Arthur Rupert Dickey",
"minority government",
"George Phipps, 2nd Marquess of Normanby",
"seal hunt",
"7th Canadian Ministry",
"Order of St Michael and St George",
"Scotch whisky",
"John A. Macdonald",
"Cowley, Oxfordshire",
"Joseph Chamberlain",
"Anti-Confederation Party",
"British Empire",
"steam ship",
"Bexleyheath",
"Alexander Johnston (Canadian politician)",
"Progressive Conservative Association of Nova Scotia",
"Roman Catholic Archdiocese of Halifax-Yarmouth",
"Confederation Party",
"Governor General of Canada",
"Her Majesty's Most Honourable Privy Council",
"Scotland",
"William Stevens Fielding",
"Treaty of Washington (1871)",
"Pharmacy",
"syndicate",
"Library and Archives Canada",
"confidence vote",
"1st Canadian Ministry",
"William Young (Nova Scotia politician)",
"Minister of Railways and Canals (Canada)",
"Minister of Customs",
"Oxford Military College",
"Grand Trunk Railway",
"British Columbia",
"Minister of Finance (Canada)",
"Canadians",
"Knight Grand Cross of the Order of St Michael and St George",
"John Turner",
"Mayflower Compact",
"cross the floor",
"American Civil War",
"Samuel Leonard Tilley",
"The New York Times",
"Pacific Scandal",
"Jean Chrétien",
"Paris",
"Charles Hastings Doyle",
"Theodore Harding Rand",
"Suffrage",
"John Lambton, 1st Earl of Durham",
"Windsor and Annapolis Railway",
"Red River Rebellion",
"Minister of Public Works (Canada)",
"Saint John, New Brunswick",
"superintendent of education",
"Member of Parliament (Canada)",
"Canadian–American Reciprocity Treaty",
"President of the Privy Council",
"Sir Charles Tupper Secondary School",
"Leader of the Opposition (Canada)",
"Alexander Morris (politician)",
"1887 Canadian federal election"
] |
5,985 |
Canadian Radio-television and Telecommunications Commission
|
The Canadian Radio-television and Telecommunications Commission (CRTC; ) is a public organization in Canada tasked with the mandate as a regulatory agency tribunal for various electronic communications, covering broadcasting and telecommunications. It was created in 1976 when it took over responsibility for regulating telecommunication carriers. Prior to 1976, it was known as the Canadian Radio and Television Commission, which was established in 1968 by the Parliament of Canada to replace the Board of Broadcast Governors. Its headquarters is located in the Central Building (Édifice central) of Les Terrasses de la Chaudière in Gatineau, Quebec.
== History ==
The CRTC was originally known as the Canadian Radio-Television Commission. In 1976, jurisdiction over telecommunications services, most of which were then delivered by monopoly common carriers (for example, telephone companies), was transferred to it from the Canadian Transport Commission although the abbreviation CRTC remained the same.
On the telecom side, the CRTC originally regulated only privately held common carriers:
BC Tel (merged with Telus), which served British Columbia, in which a U.S. company (GTE) held a substantial stake
Bell Canada, which served much of Ontario and Quebec, and the eastern part of the Northwest Territories (now Nunavut)
telephone operations owned by crown corporation Canadian National Railways in Newfoundland (Terra Nova Tel), the Northwest Territories, Yukon and northern B.C. (the latter three being Northwestel).
Other telephone companies, many of which were publicly owned and entirely within a province's borders, were regulated by provincial authorities until court rulings during the 1990s affirmed federal jurisdiction over the sector, which also included some fifty small independent incumbents, most of them in Ontario and Quebec. Notable in this group were:
Newfoundland Telephone
Maritime Telegraph and Telephone
Island Telephone (Island Tel)
New Brunswick Telephone (NBTel)
Manitoba Telephone System (MTS)
SaskTel
Alberta Government Telephones (AGT)
Northern Telephone (Ontario)
Télébec
municipal telephone services in Prince Rupert, B.C. (CityWest) and Thunder Bay (Tbaytel)
== Organisational structure ==
The CRTC is run by up to 13 full-time members (including the chairman, the vice-chairman of broadcasting, and the vice-chairman of telecommunications) appointed by the Cabinet for renewable terms of up to five years. However, unlike the more directly political appointees of the American Federal Communications Commission, the CRTC is an arms-length regulatory body with more autonomous authority over telecommunications. For example, the CRTC's decisions rely more on a judiciary process relying on evidence submitted during public consultations, rather than along party lines as the American FCC is prone to do.
The CRTC Interconnection Steering Committee (CISC) assists in developing information, procedures and guidelines for the CRTC's regulatory activities.
=== Chairs of the CRTC ===
1968–1975 – Pierre Juneau
1975–1977 – Harry J. Boyle
1977–1979 – Pierre Camu
1980–1983 – John Meisel
1983–1989 – André Bureau
1990–1996 – Keith Spicer
1996–2001 – Françoise Bertrand
2001–2002 – David Colville (interim)
2002–2006 – Charles Dalfen
2007–2012 – Konrad von Finckenstein
2012 – Leonard Katz (interim)
2012–2017 – Jean-Pierre Blais
2017–2023 – Ian Scott
2023–present – Vicky Eatrides
=== Related legislation ===
Accurate News and Information Act
Bell Canada Act
Broadcasting Act, 1991
Canadian Radio-television and Telecommunications Commission Act
Public Broadcasting Act of 1967 – USA
Telecommunications Act
Online Streaming Act
== Jurisdiction ==
The CRTC regulates all Canadian broadcasting and telecommunications activities and enforces rules it creates to carry out the policies assigned to it; the best-known of these is probably the Canadian content rules. The CRTC reports to the Parliament of Canada through the Minister of Canadian Heritage, which is responsible for the Broadcasting Act, and has an informal relationship with Industry Canada, which is responsible for the Telecommunications Act. Provisions in these two acts, along with less-formal instructions issued by the federal cabinet known as orders-in-council, represent the bulk of the CRTC's jurisdiction.
In many cases, such as the cabinet-directed prohibition on foreign ownership for broadcasters and the legislated principle of the predominance of Canadian content, these acts and orders often leave the CRTC less room to change policy than critics sometimes suggest, and the result is that the commission is often the lightning rod for policy criticism that could arguably be better directed at the government itself.
Complaints against broadcasters, such as concerns around offensive programming, are dealt with by the Canadian Broadcast Standards Council (CBSC), an independent broadcast industry association, rather than by the CRTC, although CBSC decisions can be appealed to the CRTC if necessary. However, the CRTC is also sometimes erroneously criticized for CBSC decisions — for example, the CRTC was erroneously criticized for the CBSC's decisions pertaining to the airing of Howard Stern's terrestrial radio show in Canada in the late 1990s, as well as the CBSC's controversial ruling on the Dire Straits song "Money for Nothing".
The commission is not fully equivalent to the U.S. Federal Communications Commission, which has additional powers over technical matters, in broadcasting and other aspects of communications, in that country. In Canada, Innovation, Science and Economic Development Canada (formerly Industry Canada) is responsible for allocating frequencies and call signs, managing the broadcast spectrum, and regulating other technical issues such as interference with electronics equipment.
=== Regulation of broadcast distributors ===
The CRTC has in the past regulated the prices cable television broadcast distributors are allowed to charge. In most major markets, however, prices are no longer regulated due to increased competition for broadcast distribution from satellite television.
The CRTC also regulates which channels broadcast distributors must or may offer. Per the Broadcasting Act the commission also gives priority to Canadian signals—many non-Canadian channels which compete with Canadian channels are thus not approved for distribution in Canada. The CRTC argues that allowing free trade in television stations would overwhelm the smaller Canadian market, preventing it from upholding its responsibility to foster a national conversation. Some people, however, consider this tantamount to censorship.
The CRTC's simultaneous substitution rules require that when a Canadian network licenses a television show from a US network and shows it in the same time slot, upon request by the Canadian broadcaster, Canadian broadcast distributors must replace the show on the US channel with the broadcast of the Canadian channel, along with any overlays and commercials.
As Grey's Anatomy is on ABC, but is carried in Canada on CTV at the same time, for instance, the cable, satellite, or other broadcast distributor must send the CTV feed over the signal of the carried ABC affiliate, even where the ABC version is somehow different, particularly commercials. (These rules are not intended to apply in case of differing episodes of the same series; this difference may not always be communicated to distributors, although this is rather rare.) Viewers via home antenna who receive both American and Canadian networks on their personal sets are not affected by sim-sub.
The goal of this policy is to create a market in which Canadian networks can realize revenue through advertising sales in spite of their inability to match the rates that the much larger American networks can afford to pay for syndicated programming. This policy is also why Canadian viewers do not see American advertisements during the Super Bowl, even when tuning into one of the many American networks carried on Canadian televisions.
The CRTC also regulates radio in Canada, including community radio, where the CRTC requires that at least 15% of each station's output must be locally produced spoken word content.
=== Regulation of the Internet ===
In a major May 1999 decision on "New Media", the CRTC held that under the Broadcasting Act the CRTC had jurisdiction over certain content communicated over the Internet including audio and video, but excluding content that is primarily alphanumeric such as emails and most webpages. It also issued an exemption order committing to a policy of non-interference.
In May 2011, in response to the increase presence of Over-the-Top (OTT) programming, the CRTC put a call out to the public to provide input on the impact OTT programming is having on Canadian content and existing broadcasting subscriptions through satellite and cable.
On October 5, 2011, the CRTC released their findings that included consultations with stakeholders from the telecommunication industry, media producers, and cultural leaders among others. The evidence was inconclusive, suggesting that an increased availability of OTT options is not having a negative impact on the availability or diversity of Canadian content, one of the key policy mandates of the CRTC, nor are there signs that there has been a significant decline of television subscriptions through cable or satellite. However, given the rapid progress in the industry they are working on a more in depth study to be concluded in May 2012.
The CRTC does not directly regulate rates, quality of service issues, or business practices for Internet service providers. However, the CRTC does continually monitor the sector and associated trends. To handle complains, the CRTC was ordered by the Government of Canada to create an independent, industry-funded agency to resolve complaints from consumers and small business retail telecom customers. In July 2007, the Commission for Complaints for Telecom-Television Services (CCTS) opened its doors.
Third Party ISP Access refers to a ruling forcing Cable operators (MSO) to offer Internet access to third party resellers.
=== Regulation of telecommunications services ===
The commission currently has some jurisdiction over the provision of local landline telephone service in Canada. This is largely limited to the major incumbent carriers, such as Bell Canada and Telus, for traditional landline service (but not Voice over Internet Protocol (VoIP)). It has begun the gradual deregulation of such services where, in the commission's opinion, a sufficient level of competition exists.
The CRTC is sometimes blamed for the current state of the mobile phone industry in Canada, in which there are only three national mobile network operators – Bell Mobility, Telus Mobility, and Rogers Wireless – as well as a handful of MVNOs operating on these networks. In fact, the commission has very little to do with the regulation of mobile phone service, outside of "undue preference" issues (for example, a carrier offering a superior rate or service to some subscribers and not others without a good reason).
It does not regulate service rates, service quality, or other business practices, and commission approval is not necessary for wireless provider sales or mergers as in the broadcasting industry. Moreover, it does not deal with the availability of spectrum for mobile phone service, which is part of the Industry Canada mandate, nor the maintenance of competition, which is largely the responsibility of The Competition Bureau.
=== Transfers of ownership/foreign ownership ===
Any transfer of more than 30% of the ownership of a broadcasting licence (including cable/satellite distribution licences) requires advance approval of the commission. One condition normally taken into account in such a decision is the level of foreign ownership; federal regulations require that Canadian citizens ultimately own a majority of a broadcast licence. Usually this takes the form of a public process, where interested parties can express their concerns and sometimes including a public hearing, followed by a commission decision.
While landline and mobile telephone providers must also be majority-owned by Canadians under the federal Telecommunications Act, the CRTC is not responsible for enforcement of this provision. In fact, the commission does not require licences at all for telephone companies, and CRTC approval is therefore not generally required for the sale of a telephone company, unless said company also owns a broadcast licence.
== Notable decisions ==
Since 1987, the CRTC has been involved in several notable decisions, some of which led to controversy and debate.
=== Milestone Radio ===
Milestone Radio: In two separate rounds of licence hearings in the 1990s, the CRTC rejected applications by Milestone Radio to launch a radio station in Toronto which would have been Canada's first urban music station; in both cases, the CRTC instead granted licences to stations that duplicated formats already offered by other stations in the Toronto market. The decision has been widely cited as one of the single most significant reasons why Canadian hip hop had difficulty establishing its commercial viability throughout the 1990s. The CRTC finally granted a licence to Milestone in 2000, after a cabinet order-in-council directed the commission to license two new radio stations that reflected the cultural diversity of the Toronto market, and CFXJ-FM launched in 2001. Its competitor applicant, Alberta-based Allarcom, appealed this decision to the House of Commons of Canada. It was overturned and there were questions of whether federal politicians should meddle in CRTC decisions. Because of this the network launch was delayed from September 1, 1988, to July 31, 1989.
=== RAI International ===
RAI International: In Summer 2004, this Italian government-controlled channel was denied permission to broadcast independently in Canada on the grounds that it had acted and was likely to act contrary to established Canadian policies. RAI International's latest politically appointed President (an avowed right wing nationalist and former spokesperson for Giorgio Almirante, the leader of the post-fascist party of Italy) had unilaterally terminated a 20-year-old agreement and stripped all of its 1,500 to 2,000 annual hours of programming from Telelatino (TLN), a Canadian-run channel which had devoted 95% of its prime time schedule to RAI programs for 20 years since TLN was founded.
All Italian-Canadians were denied RAI programming by RAI International's removal of its programming from the Canadian marketplace, a move intended to create a public outcry and a threat that Canadians would resort to using satellite viewing cards obtained via the US in order to watch RAI, even though these cards were either grey market or black market, according to different analyses (see below). Following unprecedented foreign led and domestic political interference with the CRTC's quasi-judicial independent regulatory process, within six months of its original decision, an abrupt CRTC "review" of its policy on third-language foreign services determined to drop virtually all restrictions and adopt a new "open entry" approach to foreign controlled "third language" (non-English, non-French) channels.
=== Al Jazeera ===
Al Jazeera: Was approved by the CRTC in 2004 as an optional cable and satellite offering, but on the condition that any carrier distributing it must edit out any instances of illegal hate speech. Cable companies declared that these restrictions would make it too expensive to carry Al Jazeera. Although no cable company released data as to what such a monitoring service would cost, the end-result was that no cable company elected to carry the station, either, leaving many Arabic-speaking Canadians using free-to-air satellite dishes to watch the station.
The Canadian Jewish Congress has expressed its opinion over possible anti-Semitic incitement on this station and that the restrictions on Al Jazeera are appropriate, while the Canadian B'nai Brith is opposed to any approval of Al Jazeera in Canada. The CRTC ruling applied to Al Jazeera and not to its English-speaking sister network Al Jazeera English, which was launched two years after the ruling.
=== Fox News Channel ===
Fox News Channel: Until 2004, the CRTC's apparent reluctance to grant a digital licence to Fox News Channel under the same policy which made it difficult for RAI to enter the country – same-genre competition from foreign services – had angered many conservative Canadians, who believed the network was deliberately being kept out due to its perceived conservative bias, particularly given the long-standing availability of services such as CNN and BBC World in Canada.
On November 18, 2004, however, the CRTC approved an application by cable companies to offer Fox News Channel on the digital cable tier. Fox commenced broadcasting in Canada shortly thereafter.
=== Satellite radio ===
Satellite radio: In June 2005, the CRTC outraged some Canadian cultural nationalists (such as the Friends of Canadian Broadcasting) and labour unions by licensing two companies, Canadian Satellite Radio and Sirius Canada to offer satellite radio services in Canada. The two companies are in partnership with American firms XM Satellite Radio and Sirius Satellite Radio respectively, and in accordance with the CRTC decision will only need to offer ten percent Canadian content. The CRTC contends that this low level of Canadian content, particularly when compared to the 35% rule on local radio stations, was necessary because unlicensed U.S. receivers were already flooding into the country, so that enforcing a ban on these receivers would be nearly impossible (see below).
This explanation did not satisfy cultural nationalists, who demanded that the federal cabinet overturn the decision and mandate a minimum of 35% Canadian content. Supporters of the decision argue that satellite radio can only be feasibly set up as a continental system, and trying to impose 35% Canadian content across North America is quite unrealistic. They also argue that satellite radio will boost Canadian culture by giving vital exposure to independent artists, instead of concentrating just on the country's stars, and point to the CRTC's successful extraction of promises to program 10% Canadian content on satellite services already operational in the United States as important concessions. Despite popular perception that the CRTC banned Sirius Canada from broadcasting Howard Stern's program, this is not the case. Sirius Canada in fact initially chose not to air Stern based on the possibility of a future issue with the CRTC, although the company reversed its decision and began offering Howard Stern in 2006.
=== 2008 Ottawa radio licence ===
2008 Ottawa radio licences: On November 21, 2008, federal Minister of Canadian Heritage and Official Languages James Moore issued a statement calling on the CRTC to review its approval of two new radio stations, Frank Torres' CIDG-FM and Astral Media's CJOT-FM, which it had licensed in August 2008 to serve the Ottawa-Gatineau radio market. Moore asked the commission to assess whether the francophone population of the Ottawa-Gatineau area was sufficiently well-served by existing French radio services, and to consider licensing one or more of the French language applications, which included a Christian music station, a community radio station and a campus radio station for the Université du Québec en Outaouais, in addition to or instead of the approved stations. The review ultimately identified a viable frequency for a third station, and CJFO-FM launched in 2010.
=== Bell Canada usage-based Internet billing ===
Bell Canada usage-based billing: On October 28, 2010, the CRTC handed down its final decision on how wholesale customers can be billed by large network owners. Under the plan which starts within 90 days, Bell will be able to charge wholesale service providers a flat monthly fee to connect to its network, and for a set monthly usage limit per each ISP customer the ISP has. Beyond that set limit, individual users will be charged per gigabyte, depending on the speed of their connections.
Customers using the fastest connections of five megabits per second, for example, will have a monthly allotment of 60 GB, beyond which Bell will charge $1.12 per GB to a maximum of $22.50. If a customer uses more than 300 GB a month, Bell will also be able to implement an additional charge of 75 cents per gigabyte. In May 2010, the CRTC ruled that Bell could not implement its usage-based billing system until all of its own retail customers had been moved off older, unlimited downloading plans. The requirement would have meant that Bell would have to move its oldest and most loyal customers.
The CRTC also added that Bell would be required to offer to wholesale ISPs the same usage insurance plan it sells to retail customers. Bell appealed both requirements, citing that the rules do not apply to cable companies and that they constituted proactive rate regulation by the CRTC, which goes against government official policy direction that the regulator only intervene in markets after a competitive problem has been proven. In Thursday's decision, the CRTC rescinded both requirements, thereby giving Bell the go-ahead to implement usage-based billing. This ruling according to Teksavvy handcuffs the competitive market. This has been asked by Stephen Harper and Parliament to have the decision reviewed. According to a tweet by Industry Minister Tony Clement, unless the CRTC reverses this decision, the government will use its override power to reverse the decision.
== Reception of non-Canadian services ==
While an exact number has not been determined, thousands of Canadians have purchased and used what they contend to be grey market radio and television services, licensed in the United States but not in Canada. Users of these unlicensed services contend that they are not directly breaking any laws by simply using the equipment. The equipment is usually purchased from an American supplier (although some merchants have attempted to set up shop in Canada) and the services are billed to an American postal address. The advent of online billing and the easy availability of credit card services has made it relatively easy for almost anyone to maintain an account in good standing, regardless of where they actually live.
Sec. 9(1)(c) of the Radiocommunication Act creates a prohibition against all decoding of encrypted programming signals, followed by an exception where authorization is received from the person holding the lawful right in Canada to transmit and authorize decoding of the signal. This means receiving the encrypted programming of DishNetwork or DirecTV, even with a grey market subscription, may be construed as unlawful (this remains an unresolved Constitutional issue).
Notwithstanding, possession of DishNetwork or DirecTV equipment is not unlawful as provided by The Radiocommuncation Act Section 4(1)(b), which states:
"No person shall, except under and in accordance with a radio authorization, install, operate or possess radio apparatus, other than (b)a radio apparatus that is capable only of the reception of broadcasting and that is not a distribution undertaking. (radio apparatus" means a device or combination of devices intended for, or capable of being used for, radiocommunication)."
Satellite radio poses a more complicated problem for the CRTC. While an unlicensed satellite dish can often be identified easily, satellite radio receivers are much more compact and can rarely be easily identified, at least not without flagrantly violating provisions against unreasonable search and seizure in the Canadian Charter of Rights and Freedoms. Some observers argued that this influenced the CRTC's June 2005 decision to ease Canadian content restrictions on satellite radio (see above).
|
[
"CHOI-FM",
"Third Party ISP Access",
"Public Broadcasting Act of 1967",
"Maritime Telegraph and Telephone Company",
"Demographics of Canada",
"Nunavut",
"Internet in Canada",
"SaskTel",
"CityWest",
"Cabinet of Canada",
"BC Tel",
"Quebec City",
"André Bureau",
"Rogers Wireless",
"NorthernTel",
"Canadian Satellite Radio",
"Jean-Pierre Blais",
"Category A services",
"Toronto",
"Sirius Satellite Radio",
"Bell Canada",
"Super Bowl advertising",
"Terrasses de la Chaudière",
"Canadian Broadcast Standards Council",
"Bell Mobility",
"Sirius Canada",
"Harry J. Boyle",
"Astral Media",
"Government of Canada",
"search and seizure",
"Régie des télécommunications du Québec",
"Alberta",
"NBTel",
"labour union",
"Toronto Star",
"Voice over Internet Protocol",
"conservative bias",
"John Meisel",
"Canadian National Railways",
"Gatineau",
"Commission for Complaints for Telecom-television Services",
"Minister of Canadian Heritage",
"Alberta Government Telephones",
"Fox News Channel",
"CJOT-FM",
"Online Streaming Act",
"Howard Stern",
"Category B services",
"Canada",
"The Competition Bureau",
"Island Telephone Company",
"Canadian hip hop",
"Industry Canada",
"United States",
"Parliament of Canada",
"telephone",
"CNN",
"Music of Canada",
"Fee-for-carriage",
"wikt:francophone",
"Canadian Transport Commission",
"Telecommunications Act (Canada)",
"Pascale St-Onge",
"Canadian Jewish Congress",
"GTE",
"Grey's Anatomy",
"Telelatino",
"Telus",
"The Globe and Mail",
"CJFO-FM",
"Yukon",
"credit card",
"International Telecommunication Union",
"Canadian content",
"television antenna",
"American Broadcasting Company",
"Terra Nova Tel",
"House of Commons of Canada",
"CTV Television Network",
"Tony Clement",
"Internet broadcasting",
"Money for Nothing (song)",
"Françoise Bertrand",
"NewTel Communications",
"BBC World",
"Federal Communications Commission",
"CFXJ-FM",
"Ontario",
"Pierre Camu",
"List of telecommunications regulatory bodies",
"The Canadian Encyclopedia",
"Quebec",
"black market",
"Al Jazeera Media Network",
"Charles Dalfen",
"B'nai Brith",
"censorship",
"Twitter",
"Accurate News and Information Act",
"Italy",
"Télébec",
"online billing",
"Ottawa",
"satellite television",
"Christian music",
"Satellite radio",
"free-to-air",
"Ian Scott (Canadian businessman)",
"digital cable",
"Broadcasting Act, 1991",
"Parliament Hill",
"Super Bowl",
"urban music",
"grey market",
"Inter-American Telecommunication Commission",
"Cable television",
"Canadian Charter of Rights and Freedoms",
"community radio",
"Université du Québec en Outaouais",
"Telus Mobility",
"anti-Semitic",
"Konrad von Finckenstein",
"CPAC (TV channel)",
"Department of Canadian Heritage",
"James Moore (Canadian politician)",
"XM Satellite Radio",
"Order in Council",
"Al Jazeera English",
"CIDG-FM",
"campus radio",
"Allarcom",
"CanLII",
"MVNO",
"Canadian Independent Telephone Association",
"Keith Spicer",
"Friends of Canadian Broadcasting",
"Milestone Radio",
"Northwestel",
"Ontario Telecommunications Association",
"Pierre Juneau",
"cable television",
"Northwest Territories",
"Board of Broadcast Governors",
"RAI International",
"all-news",
"British Columbia",
"Bell MTS",
"Tbaytel",
"Electronic Communications Convention",
"mobile phone",
"Dire Straits",
"simultaneous substitution",
"CBC Newsworld",
"Ontario Telephone Service Commission",
"Community radio in Canada",
"Canadian Broadcasting Corporation",
"Historica Canada",
"Over-the-Top",
"Newfoundland",
"Innovation, Science and Economic Development Canada",
"Canadian conservatism"
] |
5,986 |
Con
|
Con or CON may refer to:
==Places==
Commonwealth of Nations, or CON, an association of primarily former British colonies
Concord Municipal Airport (IATA airport code CON), a public-use airport in Merrimack County, New Hampshire, United States
Cornwall, England, Chapman code CON
==Arts, entertainment, and media==
Con (TV series), a television show about confidence trickery
Con Air, a 1997 American action crime film
Naruto: Clash of Ninja, or CON, a 3D cel-shaded fighting game
The Chronicles of Narnia, or CON, a series of seven fantasy novels for children written by C. S. Lewis
==Brands and enterprises==
Consolidated Edison, also called Con Edison or ConEd
Continental Oil
==Language==
Con language
Constructed language
==Other uses==
===Con===
Con (name)
Confidence trick, also known as con, scam, or flim flam; con is also a person who perpetrates a confidence trick
Conn (nautical), also spelled con, the command of movement of a ship at sea
Consider (MUD), the ability to evaluate an opponent in MUDs
Contact lens, in Hong Kong English
Convention (meeting)
Fan convention, e.g. "Comic-Con"
Convict, as in con, a person who has been convicted of a crime, or ex-con, a person who has completed their prison sentence
Convicted felon, a person who has been convicted of a felony crime in a court of law
Con, a musical term meaning "with" borrowed from Italian (see Italian musical terms used in English)
Con, Kakao Friends characters
===CON===
Certificate of Need, or CON
Commander of the Order of the Niger, or CON
Cornwall, county in England, Chapman code
CON, a name not allowed for folders in Microsoft Windows, see List of Easter eggs in Microsoft products#Microsoft Windows.
|
[
"Anti (disambiguation)",
"Cornwall",
"Constructed language",
"Continental Oil",
"Con language",
"Con Air",
"Conrad (name)",
"Con (name)",
"Con (TV series)",
"Pro (disambiguation)",
"Consolidated (disambiguation)",
"Khan (disambiguation)",
"Consider (MUD)",
"Fan convention",
"Confidence trick",
"Conn (disambiguation)",
"The Chronicles of Narnia",
"Certificate of Need",
"Counter (disambiguation)",
"Conservative Party (disambiguation)",
"Naruto: Clash of Ninja",
"Contact lens",
"Convicted felon",
"Convention (meeting)",
"Concord Municipal Airport",
"Consolidated Edison",
"Conn (nautical)",
"Contra (disambiguation)",
"Contrary (disambiguation)",
"Kon (disambiguation)",
"Conning (disambiguation)",
"Consol (disambiguation)",
"Italian musical terms used in English",
"Commander of the Order of the Niger",
"List of Easter eggs in Microsoft products",
"Commonwealth of Nations",
"Constantine (disambiguation)",
"Qon",
"Kakao Friends",
"Consolidation (disambiguation)",
"Convict"
] |
5,987 |
Coal
|
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is a type of fossil fuel, formed when dead plant matter decays into peat which is converted into coal by the heat and pressure of deep burial over millions of years. Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous (Pennsylvanian) and Permian times.
Coal is used primarily as a fuel. While coal has been known and used for thousands of years, its usage was limited until the Industrial Revolution. With the invention of the steam engine, coal consumption increased. In 2020, coal supplied about a quarter of the world's primary energy and over a third of its electricity. Some iron and steel-making and other industrial processes burn coal.
The extraction and burning of coal damages the environment, causing premature death and illness, and it is the largest anthropogenic source of carbon dioxide contributing to climate change. Fourteen billion tonnes of carbon dioxide were emitted by burning coal in 2020, which is 40% of total fossil fuel emissions As part of worldwide energy transition, many countries have reduced or eliminated their use of coal power. The United Nations Secretary General asked governments to stop building new coal plants by 2020.
Global coal use was 8.3 billion tonnes in 2022, and is set to remain at record levels in 2023. To meet the Paris Agreement target of keeping global warming below coal use needs to halve from 2020 to 2030, and "phasing down" coal was agreed upon in the Glasgow Climate Pact.
The largest consumer and importer of coal in 2020 was China, which accounts for almost half the world's annual coal production, followed by India with about a tenth. Indonesia and Australia export the most, followed by Russia.
==Etymology==
The word originally took the form col in Old English, from reconstructed Proto-Germanic *kula(n), from Proto-Indo-European root *g(e)u-lo- "live coal". Germanic cognates include the Old Frisian , Middle Dutch , Dutch , Old High German , German and Old Norse . Irish is also a cognate via the Indo-European root. in low-lying areas. In these wetlands, the process of coalification began when dead plant matter was protected from oxidation, usually by mud or acidic water, and was converted into peat. The resulting peat bogs, which trapped immense amounts of carbon, were eventually deeply buried by sediments. Then, over millions of years, the heat and pressure of deep burial caused the loss of water, methane and carbon dioxide and increased the proportion of carbon. The grade of coal produced depended on the maximum pressure and temperature reached, with lignite (also called "brown coal") produced under relatively mild conditions, and sub-bituminous coal, bituminous coal, or anthracite coal (also called "hard coal" or "black coal") produced in turn with increasing temperature and pressure.
Of the factors involved in coalification, temperature is much more important than either pressure or time of burial. Subbituminous coal can form at temperatures as low as while anthracite requires a temperature of at least .
Although coal is known from most geologic periods, 90% of all coal beds were deposited in the Carboniferous and Permian periods. Paradoxically, this was during the Late Paleozoic icehouse, a time of global glaciation. However, the drop in global sea level accompanying the glaciation exposed continental shelves that had previously been submerged, and to these were added wide river deltas produced by increased erosion due to the drop in base level. These widespread areas of wetlands provided ideal conditions for coal formation. The rapid formation of coal ended with the coal gap in the Permian–Triassic extinction event, where coal is rare.
Favorable geography alone does not explain the extensive Carboniferous coal beds. Other factors contributing to rapid coal deposition were high oxygen levels, above 30%, that promoted intense wildfires and formation of charcoal that was all but indigestible by decomposing organisms; high carbon dioxide levels that promoted plant growth; and the nature of Carboniferous forests, which included lycophyte trees whose determinate growth meant that carbon was not tied up in heartwood of living trees for long periods.
One theory suggested that about 360 million years ago, some plants evolved the ability to produce lignin, a complex polymer that made their cellulose stems much harder and more woody. The ability to produce lignin led to the evolution of the first trees. But bacteria and fungi did not immediately evolve the ability to decompose lignin, so the wood did not fully decay but became buried under sediment, eventually turning into coal. About 300 million years ago, mushrooms and other fungi developed this ability, ending the main coal-formation period of earth's history. Although some authors pointed at some evidence of lignin degradation during the Carboniferous, and suggested that climatic and tectonic factors were a more plausible explanation, reconstruction of ancestral enzymes by phylogenetic analysis corroborated a hypothesis that lignin degrading enzymes appeared in fungi approximately 200 MYa.
One likely tectonic factor was the Central Pangean Mountains, an enormous range running along the equator that reached its greatest elevation near this time. Climate modeling suggests that the Central Pangean Mountains contributed to the deposition of vast quantities of coal in the late Carboniferous. The mountains created an area of year-round heavy precipitation, with no dry season typical of a monsoon climate. This is necessary for the preservation of peat in coal swamps.
Coal is known from Precambrian strata, which predate land plants. This coal is presumed to have originated from residues of algae.
Sometimes coal seams (also known as coal beds) are interbedded with other sediments in a cyclothem. Cyclothems are thought to have their origin in glacial cycles that produced fluctuations in sea level, which alternately exposed and then flooded large areas of continental shelf.
===Chemistry of coalification===
The woody tissue of plants is composed mainly of cellulose, hemicellulose, and lignin. Modern peat is mostly lignin, with a content of cellulose and hemicellulose ranging from 5% to 40%. Various other organic compounds, such as waxes and nitrogen- and sulfur-containing compounds, are also present. Lignin has a weight composition of about 54% carbon, 6% hydrogen, and 30% oxygen, while cellulose has a weight composition of about 44% carbon, 6% hydrogen, and 49% oxygen. Bituminous coal has a composition of about 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis. The low oxygen content of coal shows that coalification removed most of the oxygen and much of the hydrogen a process called carbonization.
Carbonization proceeds primarily by dehydration, decarboxylation, and demethanation. Dehydration removes water molecules from the maturing coal via reactions such as
2 R–OH → R–O–R + H2O
Decarboxylation removes carbon dioxide from the maturing coal: The effect of decarboxylation is to reduce the percentage of oxygen, while demethanation reduces the percentage of hydrogen. Dehydration does both, and (together with demethanation) reduces the saturation of the carbon backbone (increasing the number of double bonds between carbon).
As carbonization proceeds, aliphatic compounds convert to aromatic compounds. Similarly, aromatic rings fuse into polyaromatic compounds (linked rings of carbon atoms). The structure increasingly resembles graphene, the structural element of graphite.
Chemical changes are accompanied by physical changes, such as decrease in average pore size.
===Macerals===
Macerals are coalified plant parts that retain the morphology and some properties of the original plant. In many coals, individual macerals can be identified visually. Some macerals include: Maturation of bituminous coal is characterized by bitumenization, in which part of the coal is converted to bitumen, a hydrocarbon-rich gel. Maturation to anthracite is characterized by debitumenization (from demethanation) and the increasing tendency of the anthracite to break with a conchoidal fracture, similar to the way thick glass breaks.
===Types===
As geological processes apply pressure to dead biotic material over time, under suitable conditions, its metamorphic grade or rank increases successively into:
Peat, a precursor of coal
Lignite, or brown coal, the lowest rank of coal, most harmful to health when burned, The classification of coal is generally based on the content of volatiles. However the most important distinction is between thermal coal (also known as steam coal), which is burnt to generate electricity via steam; and metallurgical coal (also known as coking coal), which is burnt at high temperature to make steel.
Hilt's law is a geological observation that (within a small area) the deeper the coal is found, the higher its rank (or grade). It applies if the thermal gradient is entirely vertical; however, metamorphism may cause lateral changes of rank, irrespective of depth. For example, some of the coal seams of the Madrid, New Mexico coal field were partially converted to anthracite by contact metamorphism from an igneous sill while the remainder of the seams remained as bituminous coal.
==History==
The earliest recognized use is from the Shenyang area of China where by 4000 BC Neolithic inhabitants had begun carving ornaments from black lignite. Coal from the Fushun mine in northeastern China was used to smelt copper as early as 1000 BC. Marco Polo, the Italian who traveled to China in the 13th century, described coal as "black stones ... which burn like logs", and said coal was so plentiful, people could take three hot baths a week. In Europe, the earliest reference to the use of coal as fuel is from the geological treatise On Stones (Lap. 16) by the Greek scientist Theophrastus (c. 371–287 BC):
Outcrop coal was used in Britain during the Bronze Age (3000–2000 BC), where it formed part of funeral pyres. In Roman Britain, with the exception of two modern fields, "the Romans were exploiting coals in all the major coalfields in England and Wales by the end of the second century AD". Evidence of trade in coal, dated to about AD 200, has been found at the Roman settlement at Heronbridge, near Chester; and in the Fenlands of East Anglia, where coal from the Midlands was transported via the Car Dyke for use in drying grain. Coal cinders have been found in the hearths of villas and Roman forts, particularly in Northumberland, dated to around AD 400. In the west of England, contemporary writers described the wonder of a permanent brazier of coal on the altar of Minerva at Aquae Sulis (modern day Bath), although in fact easily accessible surface coal from what became the Somerset coalfield was in common use in quite lowly dwellings locally. Evidence of coal's use for iron-working in the city during the Roman period has been found. In Eschweiler, Rhineland, deposits of bituminous coal were used by the Romans for the smelting of iron ore. Coal came to be referred to as "seacoal" in the 13th century; the wharf where the material arrived in London was known as Seacoal Lane, so identified in a charter of King Henry III granted in 1253. Initially, the name was given because much coal was found on the shore, having fallen from the exposed coal seams on cliffs above or washed out of underwater coal outcrops, In 1257–1259, coal from Newcastle upon Tyne was shipped to London for the smiths and lime-burners building Westminster Abbey.
These easily accessible sources had largely become exhausted (or could not meet the growing demand) by the 13th century, when underground extraction by shaft mining or adits was developed. Historian Ruth Goodman has traced the socioeconomic effects of that switch and its later spread throughout Britain In 1947 there were some 750,000 miners in Britain, but the last deep coal mine in the UK closed in 2015.
A grade between bituminous coal and anthracite was once known as "steam coal" as it was widely used as a fuel for steam locomotives. In this specialized use, it is sometimes known as "sea coal" in the United States. Small "steam coal", also called dry small steam nuts (DSSN), was used as a fuel for domestic water heating.
Coal played an important role in industry in the 19th and 20th century. The predecessor of the European Union, the European Coal and Steel Community, was based on the trading of this commodity.
Coal continues to arrive on beaches around the world from both natural erosion of exposed coal seams and windswept spills from cargo ships. Many homes in such areas gather this coal as a significant, and sometimes primary, source of home heating fuel.
==Composition==
Coal is a mixture of diverse organic compounds and polymers. Several kinds exist, with variable dark colors and composition. Young coals (brown coal, lignite) are not completely black. The two main black coals are bituminous, which is more abundant, and anthracite. The type of coal with the highest percentage of carbon in its chemical composition is anthracite, followed by bituminous, then lignite, and finally brown coal. The fuel value of coal varies in the same order. Some anthracite deposits contain pure carbon in the form of graphite.
For bituminous coal, the elemental composition on a dry, ash-free basis of 84.4% carbon, 5.4% hydrogen, 6.7% oxygen, 1.7% nitrogen, and 1.8% sulfur, on a weight basis.
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Of particular interest is the sulfur content of coal, which can vary from less than 1% to as much as 4%. Most of the sulfur and most of the nitrogen is incorporated into the organic fraction in the form of organosulfur compounds and organonitrogen compounds. This sulfur and nitrogen are strongly bound within the hydrocarbon matrix. These elements are released as SO2 and NOx upon combustion. They cannot be removed, economically at least, otherwise. Some coals contain inorganic sulfur, mainly in the form of iron pyrite (FeS2). Being a dense mineral, it can be removed from coal by mechanical means, e.g. by froth flotation. Some sulfate occurs in coal, especially weathered samples. It is not volatilized and can be removed by washing.
Minor components include:
As minerals, Hg, As, and Se are not problematic to the environment, especially since they are only trace components. They become however mobile (volatile or water-soluble) when these minerals are combusted.
==Uses==
Most coal is used as fuel. 27.6% of world energy was supplied by coal in 2017 and Asia used almost three-quarters of it. Other large-scale applications also exist. The energy density of coal is roughly 24 megajoules per kilogram (approximately 6.7 kilowatt-hours per kg). For a coal power plant with a 40% efficiency, it takes an estimated of coal to power a 100 W lightbulb for one year.
===Electricity generation===
In 2022, 68% of global coal use was used for electricity generation. The furnace heat converts boiler water to steam, which is then used to spin turbines which turn generators and create electricity. The thermodynamic efficiency of this process varies between about 25% and 50% depending on the pre-combustion treatment, turbine technology (e.g. supercritical steam generator) and the age of the plant.
A few integrated gasification combined cycle (IGCC) power plants have been built, which burn coal more efficiently. Instead of pulverizing the coal and burning it directly as fuel in the steam-generating boiler, the coal is gasified to create syngas, which is burned in a gas turbine to produce electricity (just like natural gas is burned in a turbine). Hot exhaust gases from the turbine are used to raise steam in a heat recovery steam generator which powers a supplemental steam turbine. The overall plant efficiency when used to provide combined heat and power can reach as much as 94%. IGCC power plants emit less local pollution than conventional pulverized coal-fueled plants. Other ways to use coal are as coal-water slurry fuel (CWS), which was developed in the Soviet Union, or in an MHD topping cycle. However these are not widely used due to lack of profit.
In 2017 38% of the world's electricity came from coal, the same percentage as 30 years previously. In 2018 global installed capacity was 2TW (of which 1TW is in China) which was 30% of total electricity generation capacity. The most dependent major country is South Africa, with over 80% of its electricity generated by coal; but China alone generates more than half of the world's coal-generated electricity. Efforts around the world to reduce the use of coal have led some regions to switch to natural gas and renewable energy. In 2018 coal-fired power station capacity factor averaged 51%, that is they operated for about half their available operating hours.
===Coke===
Coke is a solid carbonaceous residue that is used in manufacturing steel and other iron-containing products. Coke is made when metallurgical coal (also known as coking coal) is baked in an oven without oxygen at temperatures as high as 1,000 °C, driving off the volatile constituents and fusing together the fixed carbon and residual ash. Metallurgical coke is used as a fuel and as a reducing agent in smelting iron ore in a blast furnace. The carbon monoxide produced by its combustion reduces hematite (an iron oxide) to iron.
Pig iron, which is too rich in dissolved carbon, is also produced.
The coke must be strong enough to resist the weight of overburden in the blast furnace, which is why coking coal is so important in making steel using the conventional route. Coke from coal is grey, hard, and porous and has a heating value of 29.6 MJ/kg. Some coke-making processes produce byproducts, including coal tar, ammonia, light oils, and coal gas.
Petroleum coke (petcoke) is the solid residue obtained in oil refining, which resembles coke but contains too many impurities to be useful in metallurgical applications.
===Production of chemicals===
Chemicals have been produced from coal since the 1950s. Coal can be used as a feedstock in the production of a wide range of chemical fertilizers and other chemical products. The main route to these products was coal gasification to produce syngas. Primary chemicals that are produced directly from the syngas include methanol, hydrogen, and carbon monoxide, which are the chemical building blocks from which a whole spectrum of derivative chemicals are manufactured, including olefins, acetic acid, formaldehyde, ammonia, urea, and others. The versatility of syngas as a precursor to primary chemicals and high-value derivative products provides the option of using coal to produce a wide range of commodities. In the 21st century, however, the use of coal bed methane is becoming more important.
Because the slate of chemical products that can be made via coal gasification can in general also use feedstocks derived from natural gas and petroleum, the chemical industry tends to use whatever feedstocks are most cost-effective. Therefore, interest in using coal tended to increase for higher oil and natural gas prices and during periods of high global economic growth that might have strained oil and gas production.
Coal to chemical processes require substantial quantities of water. Much coal to chemical production is in China where coal dependent provinces such as Shanxi are struggling to control its pollution.
===Liquefaction===
Coal can be converted directly into synthetic fuels equivalent to gasoline or diesel by hydrogenation or carbonization. Coal liquefaction emits more carbon dioxide than liquid fuel production from crude oil. Mixing in biomass and using carbon capture and storage (CCS) would emit slightly less than the oil process but at a high cost. State owned China Energy Investment runs a coal liquefaction plant and plans to build 2 more.
Coal liquefaction may also refer to the cargo hazard when shipping coal.
===Gasification===
Coal gasification, as part of an integrated gasification combined cycle (IGCC) coal-fired power station, is used to produce syngas, a mixture of carbon monoxide (CO) and hydrogen (H2) gas to fire gas turbines to produce electricity. Syngas can also be converted into transportation fuels, such as gasoline and diesel, through the Fischer–Tropsch process; alternatively, syngas can be converted into methanol, which can be blended into fuel directly or converted to gasoline via the methanol to gasoline process. Gasification combined with Fischer–Tropsch technology was used by the Sasol chemical company of South Africa to make chemicals and motor vehicle fuels from coal.
During gasification, the coal is mixed with oxygen and steam while also being heated and pressurized. During the reaction, oxygen and water molecules oxidize the coal into carbon monoxide (CO), while also releasing hydrogen gas (H2). This used to be done in underground coal mines, and also to make town gas, which was piped to customers to burn for illumination, heating, and cooking.
3C (as Coal) + O2 + H2O → H2 + 3CO
If the refiner wants to produce gasoline, the syngas is routed into a Fischer–Tropsch reaction. This is known as indirect coal liquefaction. If hydrogen is the desired end-product, however, the syngas is fed into the water gas shift reaction, where more hydrogen is liberated:
CO + H2O → CO2 + H2
==Coal industry==
===Mining===
About 8,000 Mt of coal are produced annually, about 90% of which is hard coal and 10% lignite. just over half is from underground mines. The coal mining industry employs almost 2.7 million workers. More accidents occur during underground mining than surface mining. Not all countries publish mining accident statistics so worldwide figures are uncertain, but it is thought that most deaths occur in coal mining accidents in China: in 2017 there were 375 coal mining related deaths in China. Most coal mined is thermal coal (also called steam coal as it is used to make steam to generate electricity) but metallurgical coal (also called "metcoal" or "coking coal" as it is used to make coke to make iron) accounts for 10% to 15% of global coal use.
===As a traded commodity===
China mines almost half the world's coal, followed by India with about a tenth. At 471 Mt and a 34% share of global exports, Indonesia was the largest exporter by volume in 2022, followed by Australia with 344 Mt and Russia with 224 Mt. Other major exporters of coal are the United States, South Africa, Colombia, and Canada. and much higher than the price of thermal coal because metallurgical coal must be lower in sulfur and requires more cleaning. Coal futures contracts provide coal producers and the electric power industry an important tool for hedging and risk management.
In some countries, new onshore wind or solar generation already costs less than coal power from existing plants.
However, for China this is forecast for the early 2020s and for southeast Asia not until the late 2020s. In India, building new plants is uneconomic and, despite being subsidized, existing plants are losing market share to renewables.
In many countries in the Global North, there is a move away from the use of coal and former mine sites are being used as a tourist attraction.
===Market trends===
In 2022, China used 4520 Mt of coal, comprising more than half of global coal consumption. India, the European Union, and the United States, were the next largest consumers of coal, using 1162, 461, and 455 Mt respectively. Over the past decade, China has almost always accounted for the lion's share of the global growth in coal demand. Therefore, international market trends depend on Chinese energy policy.
Although the government effort to reduce air pollution in China means that the global long-term trend is to burn less coal, the short and medium term trends may differ, in part due to Chinese financing of new coal-fired power plants in other countries.]]
The use of coal as fuel causes health problems and deaths. The mining and processing of coal causes air and water pollution. Coal-powered plants emit nitrogen oxides, sulfur dioxide, particulate pollution, and heavy metals, which adversely affect human health. mostly in India and China.
Burning coal is a major contributor to sulfur dioxide emissions, which creates PM2.5 particulates, the most dangerous form of air pollution.
Coal smokestack emissions cause asthma, strokes, reduced intelligence, artery blockages, heart attacks, congestive heart failure, cardiac arrhythmias, mercury poisoning, arterial occlusion, and lung cancer.
Annual health costs in Europe from use of coal to generate electricity are estimated at up to €43 billion.
In China, early deaths due to air pollution coal plants have been estimated at 200 per GW-year, however they may be higher around power plants where scrubbers are not used or lower if they are far from cities. Improvements to China's air quality and human health would grow with more stringent climate policies, mainly because the country's energy is so heavily reliant on coal. And there would be a net economic benefit.
A 2017 study in the Economic Journal found that for Britain during the period 1851–1860, "a one standard deviation increase in coal use raised infant mortality by 6–8% and that industrial coal use explains roughly one-third of the urban mortality penalty observed during this period."
Breathing in coal dust causes coalworker's pneumoconiosis or "black lung", so called because the coal dust literally turns the lungs black. In the US alone, it is estimated that 1,500 former employees of the coal industry die every year from the effects of breathing in coal mine dust.
Huge amounts of coal ash and other waste is produced annually. Use of coal generates hundreds of millions of tons of ash and other waste products every year. These include fly ash, bottom ash, and flue-gas desulfurization sludge, that contain mercury, uranium, thorium, arsenic, and other heavy metals, along with non-metals such as selenium.
Around 10% of coal is ash. Coal ash is hazardous and toxic to human beings and some other living things. Coal ash contains the radioactive elements uranium and thorium. Coal ash and other solid combustion byproducts are stored locally and escape in various ways that expose those living near coal plants to radiation and environmental toxics.
==Damage to the environment==
Coal mining, coal combustion wastes, and flue gas are causing major environmental damage.
Water systems are affected by coal mining. For example, the mining of coal affects groundwater and water table levels and acidity. Spills of fly ash, such as the Kingston Fossil Plant coal fly ash slurry spill, can also contaminate land and waterways, and destroy homes. Power stations that burn coal also consume large quantities of water. This can affect the flows of rivers, and has consequential impacts on other land uses. In areas of water scarcity, such as the Thar Desert in Pakistan, coal mining and coal power plants contribute to the depletion of water resources.
One of the earliest known impacts of coal on the water cycle was acid rain. In 2014, approximately 100 Tg/S of sulfur dioxide (SO2) was released, over half of which was from burning coal. After release, the sulfur dioxide is oxidized to H2SO4 which scatters solar radiation, hence its increase in the atmosphere exerts a cooling effect on the climate. This beneficially masks some of the warming caused by increased greenhouse gases. However, the sulfur is precipitated out of the atmosphere as acid rain in a matter of weeks, whereas carbon dioxide remains in the atmosphere for hundreds of years. Release of SO2 also contributes to the widespread acidification of ecosystems.
Disused coal mines can also cause issues. Subsidence can occur above tunnels, causing damage to infrastructure or cropland. Coal mining can also cause long lasting fires, and it has been estimated that thousands of coal seam fires are burning at any given time. For example, Brennender Berg has been burning since 1668, and is still burning in the 21st century.
The production of coke from coal produces ammonia, coal tar, and gaseous compounds as byproducts which if discharged to land, air or waterways can pollute the environment. The Whyalla steelworks is one example of a coke producing facility where liquid ammonia was discharged to the marine environment.
===Climate change===
The largest and most long-term effect of coal use is the release of carbon dioxide, a greenhouse gas that causes climate change. Coal-fired power plants were the single largest contributor to the growth in global CO2 emissions in 2018, 40% of the total fossil fuel emissions, and more than a quarter of total emissions.
In 2016 world gross carbon dioxide emissions from coal usage were 14.5 gigatonnes. For every megawatt-hour generated, coal-fired electric power generation emits around a tonne of carbon dioxide, which is double the approximately 500 kg of carbon dioxide released by a natural gas-fired electric plant. The emission intensity of coal varies with type and generator technology and exceeds 1200 g per kWh in some countries. In 2013, the head of the UN climate agency advised that most of the world's coal reserves should be left in the ground to avoid catastrophic global warming. To keep global warming below 1.5 °C or 2 °C hundreds, or possibly thousands, of coal-fired power plants will need to be retired early.
===Underground fires===
Thousands of coal fires are burning around the world. Those burning underground can be difficult to locate and many cannot be extinguished. Fires can cause the ground above to subside, their combustion gases are dangerous to life, and breaking out to the surface can initiate surface wildfires. Coal seams can be set on fire by spontaneous combustion or contact with a mine fire or surface fire. Lightning strikes are an important source of ignition. The coal continues to burn slowly back into the seam until oxygen (air) can no longer reach the flame front. A grass fire in a coal area can set dozens of coal seams on fire. Coal fires in China burn an estimated 120 million tons of coal a year, emitting 360 million metric tons of CO2, amounting to 2–3% of the annual worldwide production of CO2 from fossil fuels.
==Pollution mitigation and carbon capture==
Systems and technologies exist to mitigate the health and environmental impact of burning coal for energy.
===Precombustion treatment===
Refined coal is the product of a coal-upgrading technology that removes moisture and certain pollutants from lower-rank coals such as sub-bituminous and lignite (brown) coals. It is one form of several precombustion treatments and processes for coal that alter coal's characteristics before it is burned. Thermal efficiency improvements are achievable by improved pre-drying (especially relevant with high-moisture fuel such as lignite or biomass). The goals of precombustion coal technologies are to increase efficiency and reduce emissions when the coal is burned. Precombustion technology can sometimes be used as a supplement to postcombustion technologies to control emissions from coal-fueled boilers.
=== Post combustion approaches ===
Post combustion approaches to mitigate pollution include flue-gas desulfurization, selective catalytic reduction, electrostatic precipitators, and fly ash reduction.
=== Carbon capture and storage ===
Carbon capture and storage (CCS) can be used to capture carbon dioxide from the flue gas of coal power plants and bury it securely in an underground reservoir. Between 1972 and 2017, plans were made to add CCS to enough coal and gas power plants to sequester 161 million tonnes of per year, but by 2021 98% of these plans had failed. Cost, the absence of measures to address long-term liability for stored CO2, and limited social acceptability have all contributed to project cancellations. As of 2024, CCS is in operation at only four coal power plants and one gas power plant worldwide.
=== "Clean coal" and "abated coal" ===
Since the mid-1980s, the term "clean coal" has been widely used with various meanings. Initially, "clean coal technology" referred to scrubbers and catalytic converters that reduced the pollutants that cause acid rain. The scope then expanded to include reduction of other pollutants such as mercury. Without a clear definition, is possible for fossil fuel use to be called "abated" if it uses CCS only in a minimal fashion, such as capturing only 30% of the emissions from a plant.
==Economics==
In 2018 was invested in coal supply but almost all for sustaining production levels rather than opening new mines.
In the long term coal and oil could cost the world trillions of dollars per year. Coal alone may cost Australia billions, whereas costs to some smaller companies or cities could be on the scale of millions of dollars. The economies most damaged by coal (via climate change) may be India and the US as they are the countries with the highest social cost of carbon. Bank loans to finance coal are a risk to the Indian economy. Coal pollution costs the each year. Measures to cut air pollution benefit individuals financially and the economies of countries such as China.
===Subsidies===
Subsidies for coal in 2021 have been estimated at , not including electricity subsidies, and are expected to rise in 2022. G20 countries provide at least but they include in domestic and international public finance, in fiscal support, and in state-owned enterprise (SOE) investments per year. As of 2018, government funding for new coal power plants was supplied by Exim Bank of China, the Japan Bank for International Cooperation and Indian public sector banks. Coal in Kazakhstan was the main recipient of coal consumption subsidies totalling US$2 billion in 2017. Coal in Turkey benefited from substantial subsidies in 2021.
===Stranded assets===
Some coal-fired power stations could become stranded assets, for example China Energy Investment, the world's largest power company, risks losing half its capital. As of 2021 this may be helping to cause a carbon bubble which could cause financial instability if it bursts.
==Politics==
Countries building or financing new coal-fired power stations, such as China, India, Indonesia, Vietnam, Turkey and Bangladesh, face mounting international criticism for obstructing the aims of the Paris Agreement. In 2019, the Pacific Island nations (in particular Vanuatu and Fiji) criticized Australia for failing to cut their emissions at a faster rate than they were, citing concerns about coastal inundation and erosion. In May 2021, the G7 members agreed to end new direct government support for international coal power generation.
==Cultural usage==
Coal is the official state mineral of Kentucky, and the official state rock of Utah and West Virginia. These US states have a historic link to coal mining.
Some cultures hold that children who misbehave will receive only a lump of coal from Santa Claus for Christmas in their stockings instead of presents.
It is also customary and considered lucky in Scotland to give coal as a gift on New Year's Day. This occurs as part of first-footing and represents warmth for the year to come.
|
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5,992 |
Traditional Chinese medicine
|
Traditional Chinese medicine (TCM) is an alternative medical practice drawn from traditional medicine in China. A large share of its claims are pseudoscientific, with the majority of treatments having no robust evidence of effectiveness or logical mechanism of action. In the early twentieth century, Chinese cultural and political modernizers worked to eliminate traditional practices as backward and unscientific. Traditional practitioners then selected elements of philosophy and practice and organized them into what they called "Chinese medicine". In the 1950s, the Chinese government sought to revive traditional medicine (including legalizing previously banned practices) and sponsored the integration of TCM and Western medicine, and in the Cultural Revolution of the 1960s, promoted TCM as inexpensive and popular. The creation of modern TCM was largely spearheaded by Mao Zedong, despite the fact that, according to The Private Life of Chairman Mao, he did not believe in its effectiveness. and Compendium of Materia Medica, a sixteenth-century encyclopedic work, and includes various forms of herbal medicine, acupuncture, cupping therapy, gua sha, massage (tui na), bonesetter (die-da), exercise (qigong), and dietary therapy. TCM is widely used in the Sinosphere. One of the basic tenets is that the body's qi is circulating through channels called meridians having branches connected to bodily organs and functions. The Chinese authorities have engaged in attempts to crack down on illegal TCM-related wildlife smuggling.
== Ancient history ==
Scholars in the history of medicine in China distinguish its doctrines and practice from those of present-day TCM. J. A. Jewell and S. M. Hillier state that the term "Traditional Chinese Medicine" became an established term due to the work of Dr. Kan-Wen Ma, a Western-trained medical doctor who was persecuted during the Cultural Revolution and immigrated to Britain, joining the University of London's Wellcome Institute for the History of Medicine.
The doctrines of Chinese medicine are rooted in books such as the Yellow Emperor's Inner Canon and the Treatise on Cold Damage, as well as in cosmological notions such as yin–yang and the five phases. The Compendium of Materia Medica dates back to around 1,100 BCE when only a few dozen drugs were described. By the end of the 16th century, the number of drugs documented had reached close to 1,900. And by the end of the last century, published records of CMM had reached 12,800 drugs." Starting in the 1950s, these precepts were standardized in the People's Republic of China, including attempts to integrate them with modern notions of anatomy and pathology. In the 1950s, the Chinese government promoted a systematized form of TCM. Though the Shang did not have a concept of "medicine" as distinct from other health practices, their oracular inscriptions on bones and tortoise shells refer to illnesses that affected the Shang royal family: eye disorders, toothaches, bloated abdomen, and such. Shang elites usually attributed them to curses sent by their ancestors. There is currently no evidence that the Shang nobility used herbal remedies. This being said, most historians now make a distinction between medical lancing (or bloodletting) and acupuncture in the narrower sense of using metal needles to attempt to treat illnesses by stimulating points along circulation channels ("meridians") in accordance with beliefs related to the circulation of "Qi". The earliest evidence for acupuncture in this sense dates to the second or first century BCE.
=== Han dynasty ===
The Yellow Emperor's Inner Canon (Huangdi Neijing), the oldest received work of Chinese medical theory, was compiled during the Han dynasty around the first century BCE on the basis of shorter texts from different medical lineages. Written in the form of dialogues between the legendary Yellow Emperor and his ministers, it offers explanations on the relation between humans, their environment, and the cosmos, on the contents of the body, on human vitality and pathology, on the symptoms of illness, and on how to make diagnostic and therapeutic decisions in light of all these factors. it was the first medical work to combine Yinyang and the Five Phases with drug therapy.
Nanjing or "Classic of Difficult Issues", originally called "The Yellow Emperor Eighty-one Nan Jing", ascribed to Bian Que in the eastern Han dynasty. This book was compiled in the form of question-and-answer explanations. A total of 81 questions have been discussed. Therefore, it is also called "Eighty-One Nan". The book is based on basic theory and has also analyzed some disease certificates. Questions one to twenty-two is about pulse study, questions twenty-three to twenty-nine is about meridian study, questions thirty to forty-seven is related to urgent illnesses, questions forty-eight to sixty-one is related to serious diseases, questions sixty-two to sixty-eight is related to acupuncture points, and questions sixty-nine to eighty-one is related to the needlepoint methods. Most of the pharmacological theories and compatibility rules and the proposed "seven emotions and harmony" principle have played a role in the practice of medicine for thousands of years.
=== Post-Han dynasty ===
In the centuries that followed, several shorter books tried to summarize or systematize the contents of the Yellow Emperor's Inner Canon. The Canon of Problems (probably second century CE) tried to reconcile divergent doctrines from the Inner Canon and developed a complete medical system centered on needling therapy.
Prominent medical scholars of the post-Han period included Tao Hongjing (456–536), Sun Simiao of the Sui and Tang dynasties, Zhang Jiegu (–1234), and Li Shizhen (1518–1593).
==Modern history==
===Chinese communities under Colonial rule===
Chinese communities living in colonial port cities were influenced by the diverse cultures they encountered, which also led to evolving understandings of medical practices where Chinese forms of medicine were combined with Western medical knowledge. For example, the Tung Wah Hospital was established in Hong Kong in 1869 based on the widespread rejection of Western medicine for pre-existing medical practices, although Western medicine would still be practiced in the hospital alongside Chinese medicinal practices. The Tung Wah Hospital was likely connected to another Chinese medical institution, the Kwong Wai Shiu Hospital of Singapore, which had previous community links to Tung Wah, was established for similar reasons and also provided both Western and Chinese medical care. By 1935, English-language newspapers in Colonial Singapore already used the term "Traditional Chinese Medicine" to label Chinese ethnic medical practices.
===People's Republic===
In 1950, Chinese Communist Party (CCP) chairman Mao Zedong announced support of traditional Chinese medicine; this was despite the fact that Mao did not personally believe in and did not use TCM, according to his personal physician Li Zhisui.
During the Cultural Revolution (1966–1976) the CCP and the government emphasized modernity, cultural identity and China's social and economic reconstruction and contrasted them to the colonial and feudal past. The government established a grassroots health care system as a step in the search for a new national identity and tried to revitalize traditional medicine and made large investments in traditional medicine to try to develop affordable medical care and public health facilities. The Ministry of Health directed health care throughout China and established primary care units. Chinese physicians trained in Western medicine were required to learn traditional medicine, while traditional healers received training in modern methods. This strategy aimed to integrate modern medical concepts and methods and revitalize appropriate aspects of traditional medicine. Therefore, traditional Chinese medicine was re-created in response to Western medicine. Nathan Sivin's 1987 translation of Revised Outline of Chinese Medicine: For Western-medicine practioners to learn Chinese medicine (; 1972) serves as a good, though outdated, example of this principle in practice.
The State Intellectual Property Office (now known as CNIPA) established a database of patents granted for traditional Chinese medicine.
In the second decade of the twenty-first century, Chinese Communist Party general secretary Xi Jinping strongly supported TCM, calling it a "gem". As of May 2011, in order to promote TCM worldwide, China had signed TCM partnership agreements with over 70 countries. His government pushed to increase its use and the number of TCM-trained doctors and announced that students of TCM would no longer be required to pass examinations in Western medicine. Chinese scientists and researchers, however, expressed concern that TCM training and therapies would receive equal support with Western medicine. They also criticized a reduction in government testing and regulation of the production of TCMs, some of which were toxic. Government censors have removed Internet posts that question TCM. In 2020 Beijing drafted a local regulation outlawing criticism of TCM. According to Caixin, the regulation was later passed with the provision outlawing criticism of TCM removed.
=== Hong Kong ===
At the beginning of Hong Kong's opening up, Western medicine was not yet popular, and Western medicine doctors were mostly foreigners; local residents mostly relied on Chinese medicine practitioners. In 1841, the British government of Hong Kong issued an announcement pledging to govern Hong Kong residents in accordance with all the original rituals, customs and private legal property rights. As traditional Chinese medicine had always been used in China, the use of traditional Chinese medicine was not regulated.
The establishment in 1870 of the Tung Wah Hospital was the first use of Chinese medicine for the treatment in Chinese hospitals providing free medical services. As the promotion of Western medicine by the British government started from 1940, Western medicine started being popular among Hong Kong population. In 1959, Hong Kong had researched the use of traditional Chinese medicine to replace Western medicine.
=== Historiography of Chinese medicine ===
Historians have noted two key aspects of Chinese medical history: understanding conceptual differences when translating the term , and observing the history from the perspective of cosmology rather than biology.
In Chinese classical texts, the term is the closest historical translation to the English word "body" because it sometimes refers to the physical human body in terms of being weighed or measured, but the term is to be understood as an "ensemble of functions" encompassing both the human psyche and emotions. This concept of the human body is opposed to the European duality of a separate mind and body. and that the traditional principles of acupuncture are deeply flawed. "Acupuncture points and meridians are not a reality", the review continued, but "merely the product of an ancient Chinese philosophy". In June 2019, the World Health Organization included traditional Chinese medicine in a global diagnostic compendium, but a spokesman said this was "not an endorsement of the scientific validity of any Traditional Medicine practice or the efficacy of any Traditional Medicine intervention."
A 2012 review of cost-effectiveness research for TCM found that studies had low levels of evidence, with no beneficial outcomes.
There are concerns over a number of potentially toxic plants, animal parts, and mineral Chinese compounds, There are additional concerns over the illegal trade and transport of endangered species including rhinoceroses and tigers, and the welfare of specially farmed animals, including bears.
==Philosophical background==
Traditional Chinese medicine (TCM) is a broad range of medicine practices sharing common concepts which have been developed in China and are based on a tradition of more than 2,000 years, including various forms of herbal medicine, acupuncture, massage (), exercise (), and dietary therapy. It is primarily used as a complementary alternative medicine approach. which was later absorbed by Daoism. Philosophical texts influenced TCM, mostly by being grounded in the same theories of qi, yin-yang and wuxing and microcosm-macrocosm analogies.
===Yin and yang===
Yin and yang are ancient Chinese deductive reasoning concepts used within Chinese medical diagnosis which can be traced back to the Shang dynasty (1600–1100 BCE). They represent two abstract and complementary aspects that every phenomenon in the universe can be divided into. Thus, yin and yang of the body are seen as phenomena whose lack (or over-abundance) comes with characteristic symptom combinations:
Yin vacuity (also termed "vacuity-heat"): heat sensations, possible sweating at night, insomnia, dry pharynx, dry mouth, dark urine, and a "fine" and rapid pulse.
Yang vacuity ("vacuity-cold"): aversion to cold, cold limbs, bright white complexion, long voidings of clear urine, diarrhea, pale and enlarged tongue, and a slightly weak, slow and fine pulse.
| Liver || Heart || Spleen || Lung || Kidney
|-
! Fu Organ
| iris || inner/outer corner of the eye || upper and lower lid || sclera || pupil
|}
Strict rules are identified to apply to the relationships between the Five Phases in terms of sequence, of acting on each other, of counteraction, etc. All these aspects of Five Phases theory constitute the basis of the zàng-fǔ concept, and thus have great influence regarding the TCM model of the body.
==Model of the body==
TCM "holds that the body's vital energy (chi or qi) circulates through channels, called meridians, that have branches connected to bodily organs and functions."
The primary functional entities used by traditional Chinese medicine are qì, xuě, the five zàng organs, the six fǔ organs, and the meridians which extend through the organ systems. These are all theoretically interconnected: each zàng organ is paired with a fǔ organ, which are nourished by the blood and concentrate qi for a particular function, with meridians being extensions of those functional systems throughout the body.
Concepts of the body and of disease used in TCM are pseudoscientific, similar to Mediterranean humoral theory. TCM's model of the body is characterized as full of pseudoscience. Some practitioners no longer consider yin and yang and the idea of an energy flow to apply. Scientific investigation has not found any histological or physiological evidence for traditional Chinese concepts such as qi, meridians, and acupuncture points. It is a generally held belief within the acupuncture community that acupuncture points and meridians structures are special conduits for electrical signals but no research has established any consistent anatomical structure or function for either acupuncture points or meridians. The scientific evidence for the anatomical existence of either meridians or acupuncture points is not compelling. Stephen Barrett of Quackwatch writes that, "TCM theory and practice are not based upon the body of knowledge related to health, disease, and health care that has been widely accepted by the scientific community. TCM practitioners disagree among themselves about how to diagnose patients and which treatments should go with which diagnoses. Even if they could agree, the TCM theories are so nebulous that no amount of scientific study will enable TCM to offer rational care."
===Qi===
Qi is a polysemous word that traditional Chinese medicine distinguishes as being able to transform into many different qualities of qi ().
Actuation () – of all physical processes in the body, especially the circulation of all body fluids such as blood in their vessels. This includes actuation of the functions of the zang-fu organs and meridians.
Warming () – the body, especially the limbs.
Defense () – against Exogenous Pathogenic Factors
Containment () – of body fluids, i.e., keeping blood, sweat, urine, semen, etc. from leakage or excessive emission.
Inter-transformationel () – of food, drink, and breath into qi, xue (blood), and jinye ("fluids"), and/or transformation of all of the latter into each other.
A lack of qi will be characterized especially by pale complexion, lassitude of spirit, lack of strength, spontaneous sweating, laziness to speak, non-digestion of food, shortness of breath (especially on exertion), and a pale and enlarged tongue. The latter is called weiqi (); its main function is defence and it has pronounced yang nature. Its concept is, nevertheless, defined by its functions: nourishing all parts and tissues of the body, safeguarding an adequate degree of moisture, and sustaining and soothing both consciousness and sleep.
===Jinye===
Closely related to xuě are the jinye (, usually translated as "body fluids"), and just like xuě they are considered to be yin in nature, and defined first and foremost by the functions of nurturing and moisturizing the different structures of the body. Their other functions are to harmonize yin and yang, and to help with the secretion of waste products.
Jinye are ultimately extracted from food and drink, and constitute the raw material for the production of xuě; conversely, xuě can also be transformed into jinye.
===Zangfu===
The zangfu () are the collective name of eleven entities (similar to organs) that constitute the centre piece of TCM's systematization of bodily functions. The term zang refers to the five considered to be yin in nature – Heart, Liver, Spleen, Lung, Kidney – while fu refers to the six associated with yang – Small Intestine, Large Intestine, Gallbladder, Urinary Bladder, Stomach and San Jiao. Despite having the names of organs, they are only loosely tied to (rudimentary) anatomical assumptions. Instead, they are primarily understood to be certain "functions" of the body. The fǔ organs' main purpose is merely to transmit and digest () substances such as waste and food.
Since their concept was developed on the basis of Wǔ Xíng philosophy, each zàng is paired with a fǔ, and each zàng-fǔ pair is assigned to one of five elemental qualities (i.e., the Five Elements or Five Phases). These correspondences are stipulated as:
Fire () = Heart () and Small Intestine () (and, secondarily, Sānjiaō [, "Triple Burner"] and Pericardium [])
Earth () = Spleen () and Stomach ()
Metal () = Lung () and Large Intestine ()
Water () = Kidney () and Bladder ()
Wood () = Liver () and Gallbladder ()
The zàng-fǔ are also connected to the twelve standard meridians – each yang meridian is attached to a fǔ organ, and five of the yin meridians are attached to a zàng.
===Jing-luo===
The meridians (, ) are believed to be channels running from the zàng-fǔ in the interior (, ) of the body to the limbs and joints ("the surface" [, ]), transporting qi and xuĕ. TCM identifies 12 "regular" and 8 "extraordinary" meridians; There's also a number of less customary channels branching from the "regular" meridians. In traditional China, as in many other cultures, the health and medicine of female bodies was less understood than that of male bodies. Women's bodies were often secondary to male bodies, since women were thought of as the weaker, sicklier sex.
In clinical encounters, women and men were treated differently. Diagnosing women was not as simple as diagnosing men. First, when a woman fell ill, an appropriate adult man was to call the doctor and remain present during the examination, for the woman could not be left alone with the doctor. The physician would discuss the female's problems and diagnosis only through the male. However, in certain cases, when a woman dealt with complications of pregnancy or birth, older women assumed the role of the formal authority. Men in these situations would not have much power to interfere. being the most challenging. Doctors used a medical doll known as a Doctor's lady, on which female patients could indicate the location of their symptoms.
Cheng Maoxian (b. 1581), who practiced medicine in Yangzhou, described the difficulties doctors had with the norm of female modesty. One of his case studies was that of Fan Jisuo's teenage daughter, who could not be diagnosed because she was unwilling to speak about her symptoms, since the illness involved discharge from her intimate areas. As Cheng describes, there were four standard methods of diagnosis – looking, asking, listening and smelling and touching (for pulse-taking). To maintain some form of modesty, women would often stay hidden behind curtains and screens. The doctor was allowed to touch enough of her body to complete his examination, often just the pulse taking. This would lead to situations where the symptoms and the doctor's diagnosis did not agree and the doctor would have to ask to view more of the patient.
These social and cultural beliefs were often barriers to learning more about female health, with women themselves often being the most formidable barrier. Women were often uncomfortable talking about their illnesses, especially in front of the male chaperones that attended medical examinations. Yin and yang ruled the body, the body being a microcosm of the universe and the earth. In addition, gender in the body was understood as homologous, the two genders operating in synchronization. Yin and yang concepts were applied to the feminine and masculine aspects of all bodies, implying that the differences between men and women begin at the level of this energy flow. According to Bequeathed Writings of Master Chu the male's yang pulse movement follows an ascending path in "compliance [with cosmic direction] so that the cycle of circulation in the body and the Vital Gate are felt...The female's yin pulse movement follows a defending path against the direction of cosmic influences, so that the nadir and the Gate of Life are felt at the inch position of the left hand". In sum, classical medicine marked yin and yang as high and low on bodies which in turn would be labeled normal or abnormal and gendered either male or female.
As in other cultures, fertility and menstruation dominate female health concerns. Women were often silent about suspected pregnancy, which led to many men not knowing that their wife or daughter was pregnant until complications arrived. Complications through the misdiagnosis and the woman's reluctance to speak often led to medically induced abortions. Cheng, Furth wrote, "was unapologetic about endangering a fetus when pregnancy risked a mother's well being". With these tools, the baby was born, cleaned, and swaddled; however, the mother was then immediately the focus of the doctor to replenish her qi. This process was followed up by a month check-in with the physician, a practice known as zuo yuezi.
=== Infertility ===
Infertility, not very well understood, posed serious social and cultural repercussions. The seventh-century scholar Sun Simiao is often quoted: "those who have prescriptions for women's distinctiveness take their differences of pregnancy, childbirth and [internal] bursting injuries as their basis." For example, depending on tongue and pulse conditions, a TCM practitioner might diagnose bleeding from the mouth and nose as: "Liver fire rushes upwards and scorches the Lung, injuring the blood vessels and giving rise to reckless pouring of blood from the mouth and nose." He might then go on to prescribe treatments designed to clear heat or supplement the Lung.
===Disease entities===
In TCM, a disease has two aspects: "bìng" and "zhèng". The former is often translated as "disease entity",
Since therapy will not be chosen according to the disease entity but according to the pattern, two people with the same disease entity but different patterns will receive different therapy. (compare with typical examples of patterns). The concrete pattern identified should account for all the symptoms a person has.
====Six Excesses====
The Six Excesses (, or "Six Pernicious Influences"; or slow pulse. In a concurrent exterior pattern, excess is characterized by the absence of sweating. pattern discrimination can include considerations regarding the disease cause; this is called (, "disease-cause pattern discrimination"). These are grouped into what is known as the "Four pillars" of diagnosis, which are Inspection, Auscultation/ Olfaction, Inquiry, and Palpation ().
Inspection focuses on the face and particularly on the tongue, including analysis of the tongue size, shape, tension, color and coating, and the absence or presence of teeth marks around the edge.
Auscultation refers to listening for particular sounds (such as wheezing).
Olfaction refers to attending to body odor.
Inquiry focuses on the "seven inquiries", which involve asking the person about the regularity, severity, or other characteristics of: chills, fever, perspiration, appetite, thirst, taste, defecation, urination, pain, sleep, menses, leukorrhea.
Palpation which includes feeling the body for tender A-shi points, and the palpation of the wrist pulses as well as various other pulses, and palpation of the abdomen.
===Tongue and pulse===
Examination of the tongue and the pulse are among the principal diagnostic methods in TCM. Details of the tongue, including shape, size, color, texture, cracks, teeth marks, as well as tongue coating are all considered as part of tongue diagnosis. Various regions of the tongue's surface are believed to correspond to the zàng-fŭ organs. For example, redness on the tip of the tongue might indicate heat in the Heart, while redness on the sides of the tongue might indicate heat in the Liver.
Pulse palpation involves measuring the pulse both at a superficial and at a deep level at three different locations on the radial artery (Cun, Guan, Chi, located two fingerbreadths from the wrist crease, one fingerbreadth from the wrist crease, and right at the wrist crease, respectively, usually palpated with the index, middle and ring finger) of each arm, for a total of twelve pulses, all of which are thought to correspond with certain zàng-fŭ. The pulse is examined for several characteristics including rhythm, strength and volume, and described with qualities like "floating, slippery, bolstering-like, feeble, thready and quick"; each of these qualities indicates certain disease patterns. Learning TCM pulse diagnosis can take several years.
==Herbal medicine==
thumb|left|upright|Dried [[seahorses are extensively used in traditional medicine in China and elsewhere. Thus, the term "medicinal" (instead of herb) may be used. A 2019 review of traditional herbal treatments found they are widely used but lacking in scientific evidence, and urged a more rigorous approach by which genuinely useful medicinals might be identified. Plant elements and extracts are by far the most common elements used. In the classic Handbook of Traditional Drugs from 1941, 517 drugs were listed – out of these, 45 were animal parts, and 30 were minerals. hornet nests, leeches, and scorpion. Other examples of animal parts include horn of the antelope or buffalo, deer antlers, testicles and penis bone of the dog, and snake bile.
Some compounds can include the parts of endangered species, including tiger bones and rhinoceros horn
which is used for many ailments (though not as an aphrodisiac as is commonly misunderstood in the West).
The black market in rhinoceros horns (driven not just by TCM but also unrelated status-seeking) has reduced the world's rhino population by more than 90 percent over the past 40 years.
Concerns have also arisen over the use of pangolin scales, turtle plastron, seahorses, and the gill plates of mobula and manta rays.
Poachers hunt restricted or endangered species to supply the black market with TCM products. There is no scientific evidence of efficacy for tiger medicines.
Since TCM recognizes bear bile as a treatment compound, more than 12,000 asiatic black bears are held in bear farms. The bile is extracted through a permanent hole in the abdomen leading to the gall bladder, which can cause severe pain. This can lead to bears trying to kill themselves. As of 2012, approximately 10,000 bears are farmed in China for their bile. As of March 2020 bear bile as ingredient of Tan Re Qing injection remains on the list of remedies recommended for treatment of "severe cases" of COVID-19 by National Health Commission of China and the National Administration of Traditional Chinese Medicine.
The deer penis is believed to have therapeutic benefits according to traditional Chinese medicine. Tiger parts from poached animals include tiger penis, believed to improve virility, and tiger eyes. The illegal trade for tiger parts in China has driven the species to near-extinction because of its popularity in traditional medicine. Shark fin soup is traditionally regarded in Chinese medicine as beneficial for health in East Asia, and its status as an elite dish has led to huge demand with the increase of affluence in China, devastating shark populations. The shark fins have been a part of traditional Chinese medicine for centuries. Shark finning is banned in many countries, but the trade is thriving in Hong Kong and China, where the fins are part of shark fin soup, a dish considered a delicacy, and used in some types of traditional Chinese medicine.
The tortoise (freshwater turtle, guiban) and turtle (Chinese softshell turtle, biejia) species used in traditional Chinese medicine are raised on farms, while restrictions are made on the accumulation and export of other endangered species. However, issues concerning the overexploitation of Asian turtles in China have not been completely solved. Finally, although not an endangered species, sharp rises in exports of donkeys and donkey hide from Africa to China to make the traditional remedy ejiao have prompted export restrictions by some African countries.
====Human body parts====
thumb|right|Dried [[Placenta|human placenta (Ziheche () is used in traditional Chinese medicine.
Human placenta has been used an ingredient in certain traditional Chinese medicines, including using dried human placenta, known as "Ziheche", to treat infertility, impotence and other conditions. The consumption of the human placenta is a potential source of infection.
===Efficacy===
there were not enough good-quality trials of herbal therapies to allow their effectiveness to be determined. A high percentage of relevant studies on traditional Chinese medicine are in Chinese databases. Fifty percent of systematic reviews on TCM did not search Chinese databases, which could lead to a bias in the results. Many systematic reviews of TCM interventions published in Chinese journals are incomplete, some contained errors or were misleading. The herbs recommended by traditional Chinese practitioners in the US are unregulated.
A 2013 review found the data too weak to support use of Chinese herbal medicine (CHM) for benign prostatic hyperplasia.
A 2013 review found the research on the benefit and safety of CHM for idiopathic sudden sensorineural hearing loss is of poor quality and cannot be relied upon to support their use.
A 2013 Cochrane review found inconclusive evidence that CHM reduces the severity of eczema.
The traditional medicine ginger, which has shown anti-inflammatory properties in laboratory experiments, has been used to treat rheumatism, headache and digestive and respiratory issues, though there is no firm evidence supporting these uses.
A 2012 Cochrane review found no difference in mortality rate among 640 SARS patients when Chinese herbs were used alongside Western medicine versus Western medicine exclusively, although they concluded some herbs may have improved symptoms and decreased corticosteroid doses.
A 2012 Cochrane review found insufficient evidence to support the use of TCM for people with adhesive small bowel obstruction.
A 2011 review found low quality evidence that suggests CHM improves the symptoms of Sjögren's syndrome.
A 2011 Cochrane review found inconclusive evidence to support the use of TCM herbal medicines for treatment of hypercholesterolemia.
A 2011 Cochrane review did not find improvement in fasting C-peptide when compared to insulin treatment for latent autoimmune diabetes in adults after 3 months. It is important to highlight that the studies available to be included in this review presented considerable flaws in quality and design.
A 2010 review found TCM seems to be effective for the treatment of fibromyalgia but the findings were of insufficient methodological rigor.
A 2008 Cochrane review found promising evidence for the use of Chinese herbal medicine in relieving painful menstruation, but the trials assessed were of such low methodological quality that no conclusion could be drawn about the remedies' suitability as a recommendable treatment option.
Turmeric has been used in traditional Chinese medicine for centuries to treat various conditions.
A 2005 Cochrane review found insufficient evidence for the use of CHM in HIV-infected people and people with AIDS.
A 2010 Cochrane review found insufficient evidence to support the use of Traditional Chinese Herbal Products (THCP) in the treatment of angina.
A 2010 Cochrane review found no evidence supporting the use of TCHM for stopping bleeding from haemorrhoids. There was some weak evidence of pain relief.
====Drug research====
thumb|upright|[[Artemisia annua, traditionally used to treat fever, has been found to have antimalarial properties.
There had been success in the 1970s, however, with the development of the antimalarial drug artemisinin, which is a processed extract of Artemisia annua, a herb traditionally used as a fever treatment. Artemisia annua has been used by Chinese herbalists in traditional Chinese medicines for 2,000 years. In 1596, Li Shizhen recommended tea made from qinghao specifically to treat malaria symptoms in his Compendium of Materia Medica. Researcher Tu Youyou discovered that a low-temperature extraction process could isolate an effective antimalarial substance from the plant. The extracted substance, once subject to detoxification and purification processes, is a usable antimalarial drug For her work on malaria, Tu received the 2015 Nobel Prize in Physiology or Medicine. Despite global efforts in combating malaria, it remains a large burden for the population.
Also in the 1970s Chinese researcher Zhang TingDong and colleagues investigated the potential use of the traditionally used substance arsenic trioxide to treat acute promyelocytic leukemia (APL). Building on his work, research both in China and the West eventually led to the development of the drug Trisenox, which was approved for leukemia treatment by the FDA in 2000.
Huperzine A, an extract from the herb, Huperzia serrata, is under preliminary research as a possible therapeutic for Alzheimer's disease, but poor methodological quality of the research restricts conclusions about its effectiveness.
Ephedrine in its natural form, known as má huáng () in TCM, has been documented in China since the Han dynasty (206 BCE – 220 CE) as an antiasthmatic and stimulant. In 1885, the chemical synthesis of ephedrine was first accomplished by Japanese organic chemist Nagai Nagayoshi based on his research on Japanese and Chinese traditional herbal medicines
Pien tze huang was first documented in the Ming dynasty.
====Cost-effectiveness====
A 2012 systematic review found there is a lack of available cost-effectiveness evidence in TCM.
===Safety===
From the earliest records regarding the use of compounds to today, the toxicity of certain substances has been described in all Chinese materiae medicae. For most compounds, efficacy and toxicity testing are based on traditional knowledge rather than laboratory analysis. The toxicity in some cases could be confirmed by modern research (i.e., in scorpion); in some cases it could not (i.e., in Curculigo). Botanical misidentification of plants can cause toxic reactions in humans. Traditional herbal medicines are sometimes contaminated with toxic heavy metals, including lead, arsenic, mercury and cadmium, which inflict serious health risks to consumers. Also, adulteration of some herbal medicine preparations with conventional drugs which may cause serious adverse effects, such as corticosteroids, phenylbutazone, phenytoin, and glibenclamide, has been reported.
Substances known to be potentially dangerous include Aconitum, the Chinese beetle (Mylabris phalerata), certain fungi, Aristolochia, and cinnabar. Asbestos ore (Actinolite, Yang Qi Shi, 阳起石) is used to treat impotence in TCM. Due to galena's (litharge, lead(II) oxide) high lead content, it is known to be toxic. Lead, mercury, arsenic, copper, cadmium, and thallium have been detected in TCM products sold in the U.S. and China.
To avoid its toxic adverse effects Xanthium sibiricum must be processed. A 2013 review suggested that although the antimalarial herb Artemisia annua may not cause hepatotoxicity, haematotoxicity, or hyperlipidemia, it should be used cautiously during pregnancy due to a potential risk of embryotoxicity at a high dose.
However, many adverse reactions are due to misuse or abuse of Chinese medicine.
The harvesting of guano from bat caves (yemingsha) brings workers into close contact with these animals, increasing the risk of zoonosis. The Chinese virologist Shi Zhengli has identified dozens of SARS-like coronaviruses in samples of bat droppings.
==Acupuncture and moxibustion==
Acupuncture is the insertion of needles into superficial structures of the body (skin, subcutaneous tissue, muscles) – usually at acupuncture points (acupoints) – and their subsequent manipulation; this aims at influencing the flow of qi. According to TCM it relieves pain and treats (and prevents) various diseases. The US FDA classifies single-use acupuncture needles as Class II medical devices, under CFR 21.
Acupuncture is often accompanied by moxibustion – the Chinese characters for acupuncture () literally meaning "acupuncture-moxibustion" – which involves burning mugwort on or near the skin at an acupuncture point. According to the American Cancer Society, "available scientific evidence does not support claims that moxibustion is effective in preventing or treating cancer or any other disease".
In electroacupuncture, an electric current is applied to the needles once they are inserted, to further stimulate the respective acupuncture points.
A recent historian of Chinese medicine remarked that it is "nicely ironic that the specialty of acupuncture – arguably the most questionable part of their medical heritage for most Chinese at the start of the twentieth century – has become the most marketable aspect of Chinese medicine." She found that acupuncture as we know it today has hardly been in existence for sixty years. Moreover, the fine, filiform needle we think of as the acupuncture needle today was not widely used a century ago. Present day acupuncture was developed in the 1930s and put into wide practice only as late as the 1960s.
===Efficacy===
A 2013 editorial in the American journal Anesthesia and Analgesia stated that acupuncture studies produced inconsistent results, (i.e. acupuncture relieved pain in some conditions but had no effect in other very similar conditions) which suggests the presence of false positive results. These may be caused by factors like biased study design, poor blinding, and the classification of electrified needles (a type of TENS) as a form of acupuncture. The inability to find consistent results despite more than 3,000 studies, the editorial continued, suggests that the treatment seems to be a placebo effect and the existing equivocal positive results are the type of noise one expects to see after a large number of studies are performed on an inert therapy. The editorial concluded that the best controlled studies showed a clear pattern, in which the outcome does not rely upon needle location or even needle insertion, and since "these variables are those that define acupuncture, the only sensible conclusion is that acupuncture does not work."
According to the US NIH National Cancer Institute, a review of 17,922 patients reported that real acupuncture relieved muscle and joint pain, caused by aromatase inhibitors, much better than sham acupuncture. Regarding cancer patients, the review hypothesized that acupuncture may cause physical responses in nerve cells, the pituitary gland, and the brain – releasing proteins, hormones, and chemicals that are proposed to affect blood pressure, body temperature, immune activity, and endorphin release. Commenting on this meta-analysis, both Edzard Ernst and David Colquhoun said the results were of negligible clinical significance.
A 2011 overview of Cochrane reviews found evidence that suggests acupuncture is effective for some but not all kinds of pain. A 2010 systematic review found that there is evidence "that acupuncture provides a short-term clinically relevant effect when compared with a waiting list control or when acupuncture is added to another intervention" in the treatment of chronic low back pain. Two review articles discussing the effectiveness of acupuncture, from 2008 and 2009, have concluded that there is not enough evidence to conclude that it is effective beyond the placebo effect.
Acupuncture is generally safe when administered using Clean Needle Technique (CNT). Severe adverse effects, including very rarely death (five case reports), have been reported.
==Tui na==
Tui na () is a form of massage, based on the assumptions of TCM, from which shiatsu is thought to have evolved. Techniques employed may include thumb presses, rubbing, percussion, and assisted stretching.
== Qigong ==
Qìgōng () is a TCM system of exercise and meditation that combines regulated breathing, slow movement, and focused awareness, purportedly to cultivate and balance qi. One branch of qigong is qigong massage, in which the practitioner combines massage techniques with awareness of the acupuncture channels and points.
Qi is air, breath, energy, or primordial life source that is neither matter or spirit. While Gong is a skillful movement, work, or exercise of the qi.
===Forms===
Neigong: introspective and meditative
Waigong: external energy and motion
Donggong: dynamic or active
Jinggong: tranquil or passive When combined with massage oil, the cups can be slid around the back, offering "reverse-pressure massage".
===Gua sha===
Gua sha () is abrading the skin with pieces of smooth jade, bone, animal tusks or horns or smooth stones; until red spots then bruising cover the area to which it is done. It is believed that this treatment is for almost any ailment. The red spots and bruising take three to ten days to heal, there is often some soreness in the area that has been treated.
=== Die-da ===
Diē-dǎ () or Dit Da, is a traditional Chinese bone-setting technique, usually practiced by martial artists who know aspects of Chinese medicine that apply to the treatment of trauma and injuries such as bone fractures, sprains, and bruises. Some of these specialists may also use or recommend other disciplines of Chinese medical therapies if serious injury is involved. Such practice of bone-setting () is not common in the West.
=== Chinese food therapy ===
The concepts yin and yang are associated with different classes of foods, and tradition considers it important to consume them in a balanced fashion. However, there is no scientific evidence supporting such claims, nor their implied notions.
==Regulations==
Many governments have enacted laws to regulate TCM practice.
=== Australia ===
From 1 July 2012 Chinese medicine practitioners must be registered under the national registration and accreditation scheme with the Chinese Medicine Board of Australia and meet the Board's Registration Standards, to practice in Australia.
=== Canada ===
TCM is regulated in five provinces in Canada: Alberta, British Columbia, Ontario, Quebec, and Newfoundland & Labrador.
=== China (mainland) ===
The National Administration of Traditional Chinese Medicine was created in 1949, which then absorbed existing TCM management in 1986 with major changes in 1998.
China's National People's Congress Standing Committee passed the country's first law on TCM in 2016, which came into effect on 1 July 2017. The new law standardized TCM certifications by requiring TCM practitioners to (i) pass exams administered by provincial-level TCM authorities, and (ii) obtain recommendations from two certified practitioners. TCM products and services can be advertised only with approval from the local TCM authority.
Ready-to-use TCM preparations, also known as Chinese patent medicines, are regulated by the National Medical Products Administration (and its predecessor CFDA) similar to preparations used in modern medicine since 1984. The barrier for entry, however, is much lower than medications based on modern/non-TCM principles; the rules allow for omitting clinical testing in a variety of circumstances. As of 2025, the latest (2020) rules allow a simplified procedure for preparations derived from an approved list of "classic prescriptions".
The government-run healthcare system covers a number of TCM procedures and preparations. In 2021, a total of 7114.5 billion yuan went into healthcare, amounting for 6.59% of the year's national GDP. Of these, 1111.5 billion yuan went into covering costs associated with TCM preparations (0.97% of national GDP), with 592.4 billion yuan covering the actual medications.
===Hong Kong===
During British rule, Chinese medicine practitioners in Hong Kong were not recognized as "medical doctors", which means they could not issue prescription drugs, give injections, etc. However, TCM practitioners could register and operate TCM as "herbalists". The Chinese Medicine Council of Hong Kong was established in 1999. It regulates the compounds and professional standards for TCM practitioners. All TCM practitioners in Hong Kong are required to register with the council. The eligibility for registration includes a recognised 5-year university degree of TCM, a 30-week minimum supervised clinical internship, and passing the licensing exam.
Currently, the approved Chinese medicine institutions are HKU, CUHK and HKBU.
===Macau===
The Portuguese Macau government seldom interfered in the affairs of Chinese society, including with regard to regulations on the practice of TCM. There were a few TCM pharmacies in Macau during the colonial period. In 1994, the Portuguese Macau government published Decree-Law no. 53/94/M that officially started to regulate the TCM market. After the sovereign handover, the Macau S.A.R. government also published regulations on the practice of TCM. In 2000, Macau University of Science and Technology and Nanjing University of Traditional Chinese Medicine established the Macau College of Traditional Chinese Medicine to offer a degree course in Chinese medicine.
In 2022, a new law regulating TCM, Law no. 11/2021, came into effect. The same law also repealed Decree-Law no. 53/94/M.
=== Indonesia ===
All traditional medicines, including TCM, are regulated by Indonesian Minister of Health Regulation of 2013 on traditional medicine. Traditional medicine license (Surat Izin Pengobatan Tradisional – SIPT) is granted to the practitioners whose methods are recognized as safe and may benefit health. The TCM clinics are registered but there is no explicit regulation for it. The only TCM method which is accepted by medical logic and is empirically proofed is acupuncture. The acupuncturists can get SIPT and participate in health care facilities.
=== Korea ===
Under the Medical Service Act (), an oriental medical doctor, whose obligation is to administer oriental medical treatment and provide guidance for health based on oriental medicine, shall be treated in the same manner as a medical doctor or dentist.
The Korea Institute of Oriental Medicine is the top research center of TCM in Korea.
=== Malaysia ===
The Traditional and Complementary Medicine Bill was passed by parliament in 2012 establishing the Traditional and Complementary Medicine Council to register and regulate traditional and complementary medicine practitioners, including TCM practitioners as well as other traditional and complementary medicine practitioners such as those in traditional Malay medicine and traditional Indian medicine.
=== Netherlands ===
There are no specific regulations in the Netherlands on TCM; TCM is neither prohibited nor recognised by the government of the Netherlands. Chinese herbs as well as Chinese herbal products that are used in TCM are classified as foods and food supplements, and these Chinese herbs can be imported into the Netherlands as well as marketed as such without any type registration or notification to the government.
=== New Zealand ===
Although there are no regulatory standards for the practice of TCM in New Zealand, in the year 1990, acupuncture was included in the Governmental Accident Compensation Corporation (ACC) Act. This inclusion granted qualified and professionally registered acupuncturists to provide subsidised care and treatment to citizens, residents, and temporary visitors for work or sports related injuries that occurred within and upon the land of New Zealand. The two bodies for the regulation of acupuncture and attainment of ACC treatment provider status in New Zealand are Acupuncture NZ and The New Zealand Acupuncture Standards Authority.
=== Singapore ===
The TCM Practitioners Act was passed by Parliament in 2000 and the TCM Practitioners Board was established in 2001 as a statutory board under the Ministry of Health, to register and regulate TCM practitioners. The requirements for registration include possession of a diploma or degree from a TCM educational institution/university on a gazetted list, either structured TCM clinical training at an approved local TCM educational institution or foreign TCM registration together with supervised TCM clinical attachment/practice at an approved local TCM clinic, and upon meeting these requirements, passing the Singapore TCM Physicians Registration Examination (STRE) conducted by the TCM Practitioners Board.
In 2024, Nanyang Technological University will offer the four-year Bachelor of Chinese Medicine programme, which is the first local programme accredited by the Ministry of Health.
=== Taiwan ===
In Taiwan, TCM practitioners are physicians and are regulated by the Physicians Act. They possess the authority to independently diagnose medical conditions, issue prescriptions, dispense Traditional Chinese Medicine, and prescribe a variety of diagnostic tests including X-rays, ECG, and blood and urine test.
Under current law, those who wish to qualify for the Chinese medicine exam must have obtained a 7-year university degree in TCM.
The National Research Institute of Chinese Medicine, established in 1963, is the largest Chinese herbal medicine research center in Taiwan.
=== United States ===
As of July 2012, only six states lack legislation to regulate the professional practice of TCM: Alabama, Kansas, North Dakota, South Dakota, Oklahoma, and Wyoming. In 1976, California established an Acupuncture Board and became the first state licensing professional acupuncturists.
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"Polysemy",
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"Huangdi neijing",
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"scientific knowledge",
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"benign prostatic hyperplasia",
"Zhang TingDong",
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"Chinese Ophthalmology",
"pseudoscience",
"Li Shizhen",
"acute liver failure",
"Cochrane review",
"Perspiration"
] |
5,993 |
Chemical bond
|
A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons as in covalent bonds, or some combination of these effects. Chemical bonds are described as having different strengths: there are "strong bonds" or "primary bonds" such as covalent, ionic and metallic bonds, and "weak bonds" or "secondary bonds" such as dipole–dipole interactions, the London dispersion force, and hydrogen bonding.
Since opposite electric charges attract, the negatively charged electrons surrounding the nucleus and the positively charged protons within a nucleus attract each other. Electrons shared between two nuclei will be attracted to both of them. "Constructive quantum mechanical wavefunction interference" stabilizes the paired nuclei (see Theories of chemical bonding). Bonded nuclei maintain an optimal distance (the bond distance) balancing attractive and repulsive effects explained quantitatively by quantum theory.
The atoms in molecules, crystals, metals and other forms of matter are held together by chemical bonds, which determine the structure and properties of matter.
All bonds can be described by quantum theory, but, in practice, simplified rules and other theories allow chemists to predict the strength, directionality, and polarity of bonds. The octet rule and VSEPR theory are examples. More sophisticated theories are valence bond theory, which includes orbital hybridization and resonance, and molecular orbital theory which includes the linear combination of atomic orbitals and ligand field theory. Electrostatics are used to describe bond polarities and the effects they have on chemical substances.
== Overview of main types of chemical bonds ==
A chemical bond is an attraction between atoms. This attraction may be seen as the result of different behaviors of the outermost or valence electrons of atoms. These behaviors merge into each other seamlessly in various circumstances, so that there is no clear line to be drawn between them. However it remains useful and customary to differentiate between different types of bond, which result in different properties of condensed matter.
In the simplest view of a covalent bond, one or more electrons (often a pair of electrons) are drawn into the space between the two atomic nuclei. Energy is released by bond formation. This is not as a result of reduction in potential energy, because the attraction of the two electrons to the two protons is offset by the electron-electron and proton-proton repulsions. Instead, the release of energy (and hence stability of the bond) arises from the reduction in kinetic energy due to the electrons being in a more spatially distributed (i.e. longer de Broglie wavelength) orbital compared with each electron being confined closer to its respective nucleus. These bonds exist between two particular identifiable atoms and have a direction in space, allowing them to be shown as single connecting lines between atoms in drawings, or modeled as sticks between spheres in models.
In a polar covalent bond, one or more electrons are unequally shared between two nuclei. Covalent bonds often result in the formation of small collections of better-connected atoms called molecules, which in solids and liquids are bound to other molecules by forces that are often much weaker than the covalent bonds that hold the molecules internally together. Such weak intermolecular bonds give organic molecular substances, such as waxes and oils, their soft bulk character, and their low melting points (in liquids, molecules must cease most structured or oriented contact with each other). When covalent bonds link long chains of atoms in large molecules, however (as in polymers such as nylon), or when covalent bonds extend in networks through solids that are not composed of discrete molecules (such as diamond or quartz or the silicate minerals in many types of rock) then the structures that result may be both strong and tough, at least in the direction oriented correctly with networks of covalent bonds. Also, the melting points of such covalent polymers and networks increase greatly.
In a simplified view of an ionic bond, the bonding electron is not shared at all, but transferred. In this type of bond, the outer atomic orbital of one atom has a vacancy which allows the addition of one or more electrons. These newly added electrons potentially occupy a lower energy-state (effectively closer to more nuclear charge) than they experience in a different atom. Thus, one nucleus offers a more tightly bound position to an electron than does another nucleus, with the result that one atom may transfer an electron to the other. This transfer causes one atom to assume a net positive charge, and the other to assume a net negative charge. The bond then results from electrostatic attraction between the positive and negatively charged ions. Ionic bonds may be seen as extreme examples of polarization in covalent bonds. Often, such bonds have no particular orientation in space, since they result from equal electrostatic attraction of each ion to all ions around them. Ionic bonds are strong (and thus ionic substances require high temperatures to melt) but also brittle, since the forces between ions are short-range and do not easily bridge cracks and fractures. This type of bond gives rise to the physical characteristics of crystals of classic mineral salts, such as table salt.
A less often mentioned type of bonding is metallic bonding. In this type of bonding, each atom in a metal donates one or more electrons to a "sea" of electrons that reside between many metal atoms. In this sea, each electron is free (by virtue of its wave nature) to be associated with a great many atoms at once. The bond results because the metal atoms become somewhat positively charged due to loss of their electrons while the electrons remain attracted to many atoms, without being part of any given atom. Metallic bonding may be seen as an extreme example of delocalization of electrons over a large system of covalent bonds, in which every atom participates. This type of bonding is often very strong (resulting in the tensile strength of metals). However, metallic bonding is more collective in nature than other types, and so they allow metal crystals to more easily deform, because they are composed of atoms attracted to each other, but not in any particularly-oriented ways. This results in the malleability of metals. The cloud of electrons in metallic bonding causes the characteristically good electrical and thermal conductivity of metals, and also their shiny lustre that reflects most frequencies of white light.
== History ==
Early speculations about the nature of the chemical bond, from as early as the 12th century, supposed that certain types of chemical species were joined by a type of chemical affinity. In 1704, Sir Isaac Newton famously outlined his atomic bonding theory, in "Query 31" of his Opticks, whereby atoms attach to each other by some "force". Specifically, after acknowledging the various popular theories in vogue at the time, of how atoms were reasoned to attach to each other, i.e. "hooked atoms", "glued together by rest", or "stuck together by conspiring motions", Newton states that he would rather infer from their cohesion, that "particles attract one another by some force, which in immediate contact is exceedingly strong, at small distances performs the chemical operations, and reaches not far from the particles with any sensible effect."
In 1819, on the heels of the invention of the voltaic pile, Jöns Jakob Berzelius developed a theory of chemical combination stressing the electronegative and electropositive characters of the combining atoms. By the mid 19th century, Edward Frankland, F.A. Kekulé, A.S. Couper, Alexander Butlerov, and Hermann Kolbe, building on the theory of radicals, developed the theory of valency, originally called "combining power", in which compounds were joined owing to an attraction of positive and negative poles. In 1904, Richard Abegg proposed his rule that the difference between the maximum and minimum valencies of an element is often eight. At this point, valency was still an empirical number based only on chemical properties.
However the nature of the atom became clearer with Ernest Rutherford's 1911 discovery that of an atomic nucleus surrounded by electrons in which he quoted Nagaoka rejected Thomson's model on the grounds that opposite charges are impenetrable. In 1904, Nagaoka proposed an alternative planetary model of the atom in which a positively charged center is surrounded by a number of revolving electrons, in the manner of Saturn and its rings.
Nagaoka's model made two predictions:
a very massive atomic center (in analogy to a very massive planet)
electrons revolving around the nucleus, bound by electrostatic forces (in analogy to the rings revolving around Saturn, bound by gravitational forces.)
Rutherford mentions Nagaoka's model in his 1911 paper in which the atomic nucleus is proposed.
At the 1911 Solvay Conference, in the discussion of what could regulate energy differences between atoms, Max Planck stated: "The intermediaries could be the electrons." These nuclear models suggested that electrons determine chemical behavior.
Next came Niels Bohr's 1913 model of a nuclear atom with electron orbits. In 1916, chemist Gilbert N. Lewis developed the concept of electron-pair bonds, in which two atoms may share one to six electrons, thus forming the single electron bond, a single bond, a double bond, or a triple bond; in Lewis's own words, "An electron may form a part of the shell of two different atoms and cannot be said to belong to either one exclusively."
Also in 1916, Walther Kossel put forward a theory similar to Lewis' only his model assumed complete transfers of electrons between atoms, and was thus a model of ionic bonding. Both Lewis and Kossel structured their bonding models on that of Abegg's rule (1904).
Niels Bohr also proposed a model of the chemical bond in 1913. According to his model for a diatomic molecule, the electrons of the atoms of the molecule form a rotating ring whose plane is perpendicular to the axis of the molecule and equidistant from the atomic nuclei. The dynamic equilibrium of the molecular system is achieved through the balance of forces between the forces of attraction of nuclei to the plane of the ring of electrons and the forces of mutual repulsion of the nuclei. The Bohr model of the chemical bond took into account the Coulomb repulsion – the electrons in the ring are at the maximum distance from each other.
In 1927, the first mathematically complete quantum description of a simple chemical bond, i.e. that produced by one electron in the hydrogen molecular ion, H2+, was derived by the Danish physicist Øyvind Burrau. This work showed that the quantum approach to chemical bonds could be fundamentally and quantitatively correct, but the mathematical methods used could not be extended to molecules containing more than one electron. A more practical, albeit less quantitative, approach was put forward in the same year by Walter Heitler and Fritz London. The Heitler–London method forms the basis of what is now called valence bond theory. In 1929, the linear combination of atomic orbitals molecular orbital method (LCAO) approximation was introduced by Sir John Lennard-Jones, who also suggested methods to derive electronic structures of molecules of F2 (fluorine) and O2 (oxygen) molecules, from basic quantum principles. This molecular orbital theory represented a covalent bond as an orbital formed by combining the quantum mechanical Schrödinger atomic orbitals which had been hypothesized for electrons in single atoms. The equations for bonding electrons in multi-electron atoms could not be solved to mathematical perfection (i.e., analytically), but approximations for them still gave many good qualitative predictions and results. Most quantitative calculations in modern quantum chemistry use either valence bond or molecular orbital theory as a starting point, although a third approach, density functional theory, has become increasingly popular in recent years.
In 1933, H. H. James and A. S. Coolidge carried out a calculation on the dihydrogen molecule that, unlike all previous calculation which used functions only of the distance of the electron from the atomic nucleus, used functions which also explicitly added the distance between the two electrons. With up to 13 adjustable parameters they obtained a result very close to the experimental result for the dissociation energy. Later extensions have used up to 54 parameters and gave excellent agreement with experiments. This calculation convinced the scientific community that quantum theory could give agreement with experiment. However this approach has none of the physical pictures of the valence bond and molecular orbital theories and is difficult to extend to larger molecules.
== Bonds in chemical formulas ==
Because atoms and molecules are three-dimensional, it is difficult to use a single method to indicate orbitals and bonds. In molecular formulas the chemical bonds (binding orbitals) between atoms are indicated in different ways depending on the type of discussion. Sometimes, some details are neglected. For example, in organic chemistry one is sometimes concerned only with the functional group of the molecule. Thus, the molecular formula of ethanol may be written in conformational form, three-dimensional form, full two-dimensional form (indicating every bond with no three-dimensional directions), compressed two-dimensional form (CH3–CH2–OH), by separating the functional group from another part of the molecule (C2H5OH), or by its atomic constituents (C2H6O), according to what is discussed. Sometimes, even the non-bonding valence shell electrons (with the two-dimensional approximate directions) are marked, e.g. for elemental carbon .'C'. Some chemists may also mark the respective orbitals, e.g. the hypothetical ethene−4 anion (\/C=C/\ −4) indicating the possibility of bond formation.
== Strong chemical bonds ==
Strong chemical bonds are the intramolecular forces that hold atoms together in molecules. A strong chemical bond is formed from the transfer or sharing of electrons between atomic centers and relies on the electrostatic attraction between the protons in nuclei and the electrons in the orbitals.
The types of strong bond differ due to the difference in electronegativity of the constituent elements. Electronegativity is the tendency for an atom of a given chemical element to attract shared electrons when forming a chemical bond, where the higher the associated electronegativity then the more it attracts electrons. Electronegativity serves as a simple way to quantitatively estimate the bond energy, which characterizes a bond along the continuous scale from covalent to ionic bonding. A large difference in electronegativity leads to more polar (ionic) character in the bond.
=== Ionic bond ===
Ionic bonding is a type of electrostatic interaction between atoms that have a large electronegativity difference. There is no precise value that distinguishes ionic from covalent bonding, but an electronegativity difference of over 1.7 is likely to be ionic while a difference of less than 1.7 is likely to be covalent. Ionic bonding leads to separate positive and negative ions. Ionic charges are commonly between −3e to +3e. Ionic bonding commonly occurs in metal salts such as sodium chloride (table salt). A typical feature of ionic bonds is that the species form into ionic crystals, in which no ion is specifically paired with any single other ion in a specific directional bond. Rather, each species of ion is surrounded by ions of the opposite charge, and the spacing between it and each of the oppositely charged ions near it is the same for all surrounding atoms of the same type. It is thus no longer possible to associate an ion with any specific other single ionized atom near it. This is a situation unlike that in covalent crystals, where covalent bonds between specific atoms are still discernible from the shorter distances between them, as measured via such techniques as X-ray diffraction.
Ionic crystals may contain a mixture of covalent and ionic species, as for example salts of complex acids such as sodium cyanide, NaCN. X-ray diffraction shows that in NaCN, for example, the bonds between sodium cations (Na+) and the cyanide anions (CN−) are ionic, with no sodium ion associated with any particular cyanide. However, the bonds between the carbon (C) and nitrogen (N) atoms in cyanide are of the covalent type, so that each carbon is strongly bound to just one nitrogen, to which it is physically much closer than it is to other carbons or nitrogens in a sodium cyanide crystal.
When such crystals are melted into liquids, the ionic bonds are broken first because they are non-directional and allow the charged species to move freely. Similarly, when such salts dissolve into water, the ionic bonds are typically broken by the interaction with water but the covalent bonds continue to hold. For example, in solution, the cyanide ions, still bound together as single CN− ions, move independently through the solution, as do sodium ions, as Na+. In water, charged ions move apart because each of them are more strongly attracted to a number of water molecules than to each other. The attraction between ions and water molecules in such solutions is due to a type of weak dipole-dipole type chemical bond. In melted ionic compounds, the ions continue to be attracted to each other, but not in any ordered or crystalline way.
=== Covalent bond ===
Covalent bonding is a common type of bonding in which two or more atoms share valence electrons more or less equally. The simplest and most common type is a single bond in which two atoms share two electrons. Other types include the double bond, the triple bond, one- and three-electron bonds, the three-center two-electron bond and three-center four-electron bond.
In non-polar covalent bonds, the electronegativity difference between the bonded atoms is small, typically 0 to 0.3. Bonds within most organic compounds are described as covalent. The figure shows methane (CH4), in which each hydrogen forms a covalent bond with the carbon. See sigma bonds and pi bonds for LCAO descriptions of such bonding.
Molecules that are formed primarily from non-polar covalent bonds are often immiscible in water or other polar solvents, but much more soluble in non-polar solvents such as hexane.
A polar covalent bond is a covalent bond with a significant ionic character. This means that the two shared electrons are closer to one of the atoms than the other, creating an imbalance of charge. Such bonds occur between two atoms with moderately different electronegativities and give rise to dipole–dipole interactions. The electronegativity difference between the two atoms in these bonds is 0.3 to 1.7.
==== Single and multiple bonds ====
A single bond between two atoms corresponds to the sharing of one pair of electrons. The Hydrogen (H) atom has one valence electron. Two Hydrogen atoms can then form a molecule, held together by the shared pair of electrons. Each H atom now has the noble gas electron configuration of helium (He). The pair of shared electrons forms a single covalent bond. The electron density of these two bonding electrons in the region between the two atoms increases from the density of two non-interacting H atoms.
A double bond has two shared pairs of electrons, one in a sigma bond and one in a pi bond with electron density concentrated on two opposite sides of the internuclear axis. A triple bond consists of three shared electron pairs, forming one sigma and two pi bonds. An example is nitrogen. Quadruple and higher bonds are very rare and occur only between certain transition metal atoms.
====Coordinate covalent bond (dipolar bond)====
A coordinate covalent bond is a covalent bond in which the two shared bonding electrons are from the same one of the atoms involved in the bond. For example, boron trifluoride (BF3) and ammonia (NH3) form an adduct or coordination complex F3B←NH3 with a B–N bond in which a lone pair of electrons on N is shared with an empty atomic orbital on B. BF3 with an empty orbital is described as an electron pair acceptor or Lewis acid, while NH3 with a lone pair that can be shared is described as an electron-pair donor or Lewis base. The electrons are shared roughly equally between the atoms in contrast to ionic bonding. Such bonding is shown by an arrow pointing to the Lewis acid. (In the Figure, solid lines are bonds in the plane of the diagram, wedged bonds point towards the observer, and dashed bonds point away from the observer.)
Transition metal complexes are generally bound by coordinate covalent bonds. For example, the ion Ag+ reacts as a Lewis acid with two molecules of the Lewis base NH3 to form the complex ion Ag(NH3)2+, which has two Ag←N coordinate covalent bonds.
=== Metallic bonding ===
In metallic bonding, bonding electrons are delocalized over a lattice of atoms. By contrast, in ionic compounds, the locations of the binding electrons and their charges are static. The free movement or delocalization of bonding electrons leads to classical metallic properties such as luster (surface light reflectivity), electrical and thermal conductivity, ductility, and high tensile strength.
== Intermolecular bonding ==
There are several types of weak bonds that can be formed between two or more molecules which are not covalently bound. Intermolecular forces cause molecules to attract or repel each other. Often, these forces influence physical characteristics (such as the melting point) of a substance.
Van der Waals forces are interactions between closed-shell molecules. They include both Coulombic interactions between partial charges in polar molecules, and Pauli repulsions between closed electrons shells.
Keesom forces are the forces between the permanent dipoles of two polar molecules. London dispersion forces are the forces between induced dipoles of different molecules. There can also be an interaction between a permanent dipole in one molecule and an induced dipole in another molecule.
Hydrogen bonds of the form A--H•••B occur when A and B are two highly electronegative atoms (usually N, O or F) such that A forms a highly polar covalent bond with H so that H has a partial positive charge, and B has a lone pair of electrons which is attracted to this partial positive charge and forms a hydrogen bond. Hydrogen bonds are responsible for the high boiling points of water and ammonia with respect to their heavier analogues. In some cases a similar halogen bond can be formed by a halogen atom located between two electronegative atoms on different molecules.
At short distances, repulsive forces between atoms also become important.
== Theories of chemical bonding ==
In the (unrealistic) limit of "pure" ionic bonding, electrons are perfectly localized on one of the two atoms in the bond. Such bonds can be understood by classical physics. The force between the atoms depends on isotropic continuum electrostatic potentials. The magnitude of the force is in simple proportion to the product of the two ionic charges according to Coulomb's law.
Covalent bonds are better understood by valence bond (VB) theory or molecular orbital (MO) theory. The properties of the atoms involved can be understood using concepts such as oxidation number, formal charge, and electronegativity. The electron density within a bond is not assigned to individual atoms, but is instead delocalized between atoms. In valence bond theory, bonding is conceptualized as being built up from electron pairs that are localized and shared by two atoms via the overlap of atomic orbitals. The concepts of orbital hybridization and resonance augment this basic notion of the electron pair bond. In molecular orbital theory, bonding is viewed as being delocalized and apportioned in orbitals that extend throughout the molecule and are adapted to its symmetry properties, typically by considering linear combinations of atomic orbitals (LCAO). Valence bond theory is more chemically intuitive by being spatially localized, allowing attention to be focused on the parts of the molecule undergoing chemical change. In contrast, molecular orbitals are more "natural" from a quantum mechanical point of view, with orbital energies being physically significant and directly linked to experimental ionization energies from photoelectron spectroscopy. Consequently, valence bond theory and molecular orbital theory are often viewed as competing but complementary frameworks that offer different insights into chemical systems. As approaches for electronic structure theory, both MO and VB methods can give approximations to any desired level of accuracy, at least in principle. However, at lower levels, the approximations differ, and one approach may be better suited for computations involving a particular system or property than the other.
Unlike the spherically symmetrical Coulombic forces in pure ionic bonds, covalent bonds are generally directed and anisotropic. These are often classified based on their symmetry with respect to a molecular plane as sigma bonds and pi bonds. In the general case, atoms form bonds that are intermediate between ionic and covalent, depending on the relative electronegativity of the atoms involved. Bonds of this type are known as polar covalent bonds.
|
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] |
5,995 |
Cell
|
Cell most often refers to:
Cell (biology), the functional basic unit of life
Cellphone, a phone connected to a cellular network
Clandestine cell, a penetration-resistant form of a secret or outlawed organization
Electrochemical cell, a device used to convert chemical energy to electrical energy
Prison cell, a room used to hold people in prisons
Cell may also refer to:
==Arts, entertainment, and media==
===Fictional entities===
Cell (comics), a Marvel comic book character
Cell (Dragon Ball), a character in the manga series Dragon Ball
===Literature===
Cell (novel), a 2006 horror novel by Stephen King
"Cells", poem, about a hungover soldier in gaol, by Rudyard Kipling
The Cell (play), an Australian play by Robert Wales
===Music===
Cell (music), a small rhythmic and melodic design that can be isolated, or can make up one part of a thematic context
Cell (American band)
Cell (Japanese band)
Cell (album), a 2004 album by Plastic Tree
Cells, a 1998 album by Cex
Cells, a 2012 album by Fake Blood
"Cells", an art song composed by G. F. Cobb and named after the poem by Kipling
"Cells", a song by Bloem de Ligny
"Cells", a song by I Monster from the album Neveroddoreven
"Cells", a song by The Servant
The Cells, an American rock band
"The Cell" (song), a 2006 song by Jandek
===Other arts, entertainment, and media===
The Cell (film), a 2000 psychological thriller film starring Jennifer Lopez
Cell (film), a 2016 film based on the Stephen King novel
Animation cel, a transparent sheet on which objects are drawn or painted for traditional, hand-drawn animation
"The Cell" (The Vampire Diaries), an episode of the TV series The Vampire Diaries
"The Cell" (The Walking Dead), a 2016 television episode of The Walking Dead
The Cell (BBC Four), Adam Rutherford's 3-part documentary series that aired on BBC Four
The Cell, the original title of the TV series Sleeper Cell
==Groups of people==
Cell, a group of people in a cell group, a form of Christian church organization
Cellular organizational structure, such as in business management
==Rooms==
Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery with only a few monks or nuns
==Science, mathematics, and technology==
===Computing and telecommunications===
Cell (EDA), a term used in an electronic circuit design schematics
Cell (microprocessor), a microprocessor architecture developed by Sony, Toshiba, and IBM
Cell, a unit in a database table or spreadsheet, formed by the intersection of a row and a column
Cell, in wireless local area networking standards (including Wi-Fi), a wireless connection within a limited area, referred to as a cell or Basic Service Set
Cell, a fixed-length data frame used in the Asynchronous Transfer Mode protocol
Cell (network), area of radio coverage in a cellular network
Memory cell (computing), the basic unit of (volatile or non-volatile) computer memory
===Mathematics===
Cell (geometry), a three-dimensional element, part of a higher-dimensional object
Cell, an element of an abstract cell complex
Cell, a basic unit of a cellular automaton
Cell, an element of a CW complex
Cell, a k-face of a simplicial complex
===Other uses in science and technology===
Cell (journal), a scientific journal
Fuel cell, a device used to convert chemical energy from a fuel like hydrogen to electricity
Galvanic cell or voltaic cell, a particular kind of electrochemical cell
Photodetector, or photo cell, a sensor which detects light
Solar cell, a component of photovoltaic systems used to convert the energy of light into electricity
Storm cell, the smallest unit of a storm-producing system
|
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"Cellular organizational structure",
"Cell (Dragon Ball)",
"Cell (journal)",
"Fuel cell",
"Cex (musician)",
"Cell (network)"
] |
5,999 |
Climate
|
Climate is the long-term weather pattern in a region, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorological variables that are commonly measured are temperature, humidity, atmospheric pressure, wind, and precipitation. In a broader sense, climate is the state of the components of the climate system, including the atmosphere, hydrosphere, cryosphere, lithosphere and biosphere and the interactions between them.
Climates can be classified according to the average and typical variables, most commonly temperature and precipitation. The most widely used classification scheme is the Köppen climate classification. The Thornthwaite system, in use since 1948, incorporates evapotranspiration along with temperature and precipitation information and is used in studying biological diversity and how climate change affects it. The major classifications in Thornthwaite's climate classification are microthermal, mesothermal, and megathermal. Finally, the Bergeron and Spatial Synoptic Classification systems focus on the origin of air masses that define the climate of a region.
Paleoclimatology is the study of ancient climates. Paleoclimatologists seek to explain climate variations for all parts of the Earth during any given geologic period, beginning with the time of the Earth's formation. Since very few direct observations of climate were available before the 19th century, paleoclimates are inferred from proxy variables. They include non-biotic evidence—such as sediments found in lake beds and ice cores—and biotic evidence—such as tree rings and coral. Climate models are mathematical models of past, present, and future climates. Climate change may occur over long and short timescales due to various factors. Recent warming is discussed in terms of global warming, which results in redistributions of biota. For example, as climate scientist Lesley Ann Hughes has written: "a 3 °C [5 °F] change in mean annual temperature corresponds to a shift in isotherms of approximately in latitude (in the temperate zone) or in elevation. Therefore, species are expected to move upwards in elevation or towards the poles in latitude in response to shifting climate zones."
==Definition==
Climate () is commonly defined as the weather averaged over a long period. The standard averaging period is 30 years, but other periods may be used depending on the purpose. Climate also includes statistics other than the average, such as the magnitudes of day-to-day or year-to-year variations. The Intergovernmental Panel on Climate Change (IPCC) 2001 glossary definition is as follows:
The World Meteorological Organization (WMO) describes "climate normals" as "reference points used by climatologists to compare current climatological trends to that of the past or what is considered typical. A climate normal is defined as the arithmetic average of a climate element (e.g. temperature) over a 30-year period. A 30-year period is used as it is long enough to filter out any interannual variation or anomalies such as El Niño–Southern Oscillation, but also short enough to be able to show longer climatic trends."
The WMO originated from the International Meteorological Organization which set up a technical commission for climatology in 1929. At its 1934 Wiesbaden meeting, the technical commission designated the thirty-year period from 1901 to 1930 as the reference time frame for climatological standard normals. In 1982, the WMO agreed to update climate normals, and these were subsequently completed on the basis of climate data from 1 January 1961 to 31 December 1990. The 1961–1990 climate normals serve as the baseline reference period. The next set of climate normals to be published by WMO is from 1991 to 2010. Aside from collecting from the most common atmospheric variables (air temperature, pressure, precipitation and wind), other variables such as humidity, visibility, cloud amount, solar radiation, soil temperature, pan evaporation rate, days with thunder and days with hail are also collected to measure change in climate conditions.
The difference between climate and weather is usefully summarized by the popular phrase "Climate is what you expect, weather is what you get." Over historical time spans, there are a number of nearly constant variables that determine climate, including latitude, altitude, proportion of land to water, and proximity to oceans and mountains. All of these variables change only over periods of millions of years due to processes such as plate tectonics. Other climate determinants are more dynamic: the thermohaline circulation of the ocean leads to a 5 °C (9 °F) warming of the northern Atlantic Ocean compared to other ocean basins. Other ocean currents redistribute heat between land and water on a more regional scale. The density and type of vegetation coverage affects solar heat absorption, water retention, and rainfall on a regional level. Alterations in the quantity of atmospheric greenhouse gases (particularly carbon dioxide and methane) determines the amount of solar energy retained by the planet, leading to global warming or global cooling. The variables which determine climate are numerous and the interactions complex, but there is general agreement that the broad outlines are understood, at least insofar as the determinants of historical climate change are concerned.
==Climate classification==
Climate classifications are systems that categorize the world's climates. A climate classification may correlate closely with a biome classification, as climate is a major influence on life in a region. One of the most used is the Köppen climate classification scheme first developed in 1899.
There are several ways to classify climates into similar regimes. Originally, climes were defined in Ancient Greece to describe the weather depending upon a location's latitude. Modern climate classification methods can be broadly divided into genetic methods, which focus on the causes of climate, and empiric methods, which focus on the effects of climate. Examples of genetic classification include methods based on the relative frequency of different air mass types or locations within synoptic weather disturbances. Examples of empiric classifications include climate zones defined by plant hardiness, evapotranspiration, or more generally the Köppen climate classification which was originally designed to identify the climates associated with certain biomes. A common shortcoming of these classification schemes is that they produce distinct boundaries between the zones they define, rather than the gradual transition of climate properties more common in nature.
==Record==
===Paleoclimatology===
Paleoclimatology is the study of past climate over a great period of the Earth's history. It uses evidence with different time scales (from decades to millennia) from ice sheets, tree rings, sediments, pollen, coral, and rocks to determine the past state of the climate. It demonstrates periods of stability and periods of change and can indicate whether changes follow patterns such as regular cycles.
===Modern===
Details of the modern climate record are known through the taking of measurements from such weather instruments as thermometers, barometers, and anemometers during the past few centuries. The instruments used to study weather over the modern time scale, their observation frequency, their known error, their immediate environment, and their exposure have changed over the years, which must be considered when studying the climate of centuries past. Long-term modern climate records skew towards population centres and affluent countries. Since the 1960s, the launch of satellites allow records to be gathered on a global scale, including areas with little to no human presence, such as the Arctic region and oceans.
==Climate variability==
Climate variability is the term to describe variations in the mean state and other characteristics of climate (such as chances or possibility of extreme weather, etc.) "on all spatial and temporal scales beyond that of individual weather events." Some of the variability does not appear to be caused systematically and occurs at random times. Such variability is called random variability or noise. On the other hand, periodic variability occurs relatively regularly and in distinct modes of variability or climate patterns.
There are close correlations between Earth's climate oscillations and astronomical factors (barycenter changes, solar variation, cosmic ray flux, cloud albedo feedback, Milankovic cycles), and modes of heat distribution between the ocean-atmosphere climate system. In some cases, current, historical and paleoclimatological natural oscillations may be masked by significant volcanic eruptions, impact events, irregularities in climate proxy data, positive feedback processes or anthropogenic emissions of substances such as greenhouse gases.
Over the years, the definitions of climate variability and the related term climate change have shifted. While the term climate change now implies change that is both long-term and of human causation, in the 1960s the word climate change was used for what we now describe as climate variability, that is, climatic inconsistencies and anomalies.
==Climate change==
Climate change is the variation in global or regional climates over time. It reflects changes in the variability or average state of the atmosphere over time scales ranging from decades to millions of years. These changes can be caused by processes internal to the Earth, external forces (e.g. variations in sunlight intensity) or human activities, as found recently. Scientists have identified Earth's Energy Imbalance (EEI) to be a fundamental metric of the status of global change.
In recent usage, especially in the context of environmental policy, the term "climate change" often refers only to changes in modern climate, including the rise in average surface temperature known as global warming. In some cases, the term is also used with a presumption of human causation, as in the United Nations Framework Convention on Climate Change (UNFCCC). The UNFCCC uses "climate variability" for non-human caused variations.
Earth has undergone periodic climate shifts in the past, including four major ice ages. These consist of glacial periods where conditions are colder than normal, separated by interglacial periods. The accumulation of snow and ice during a glacial period increases the surface albedo, reflecting more of the Sun's energy into space and maintaining a lower atmospheric temperature. Increases in greenhouse gases, such as by volcanic activity, can increase the global temperature and produce an interglacial period. Suggested causes of ice age periods include the positions of the continents, variations in the Earth's orbit, changes in the solar output, and volcanism. However, these naturally caused changes in climate occur on a much slower time scale than the present rate of change which is caused by the emission of greenhouse gases by human activities.
According to the EU's Copernicus Climate Change Service, average global air temperature has passed 1.5C of warming the period from February 2023 to January 2024.
==Climate models==
Climate models use quantitative methods to simulate the interactions and transfer of radiative energy between the atmosphere, oceans, land surface and ice through a series of physics equations. They are used for a variety of purposes, from the study of the dynamics of the weather and climate system to projections of future climate. All climate models balance, or very nearly balance, incoming energy as short wave (including visible) electromagnetic radiation to the Earth with outgoing energy as long wave (infrared) electromagnetic radiation from the Earth. Any imbalance results in a change in the average temperature of the Earth.
Climate models are available on different resolutions ranging from >100 km to 1 km. High resolutions in global climate models require significant computational resources, and so only a few global datasets exist. Global climate models can be dynamically or statistically downscaled to regional climate models to analyze impacts of climate change on a local scale. Examples are ICON or mechanistically downscaled data such as CHELSA (Climatologies at high resolution for the earth's land surface areas).
The most talked-about applications of these models in recent years have been their use to infer the consequences of increasing greenhouse gases in the atmosphere, primarily carbon dioxide (see greenhouse gas). These models predict an upward trend in the global mean surface temperature, with the most rapid increase in temperature being projected for the higher latitudes of the Northern Hemisphere.
Models can range from relatively simple to quite complex. Simple radiant heat transfer models treat the Earth as a single point and average outgoing energy. This can be expanded vertically (as in radiative-convective models), or horizontally. Finally, more complex (coupled) atmosphere–ocean–sea ice global climate models discretise and solve the full equations for mass and energy transfer and radiant exchange.
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6,000 |
History of the Comoros
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The history of the Comoros extends back to about 800–1000 AD when the archipelago was first inhabited. The Comoros have been inhabited by various groups and sultanates throughout this time. France colonised the islands in the 19th century, and they became independent in 1975.
==Early inhabitants==
There is uncertainty about the early population of Comoros. According to one study of early crops, the islands may have been settled first by South East Asian sailors the same way Madagascar was.
This influx of Austronesian sailors, who had earlier settled nearby Madagascar, arrived in the 8th to 13 centuries CE. They are the source for the earliest archeological evidence of farming in the islands. Crops from archeological sites in Sima are predominantly rice strains of both indica and japonica varieties from Southeast Asia, as well as various other Asian crops like mung bean and cotton. Only a minority of the examined crops were African-derived, like finger millet, African sorghum, and cowpea. The Comoros are believed to be the first site of contact and subsequent admixture between African and Asian populations (earlier than Madagascar). Comorians today still display at most 20% Austronesian admixture.
From around the 15th century AD, Shirazi slave traders established trading ports and brought in slaves from the mainland. In the 16th century, social changes on the East African coast probably linked to the arrival of the Portuguese saw the arrival of a number of Arabs of Hadrami who established alliances with the Shirazis and founded several royal clans.
Over the centuries, the Comoros have been settled by a succession of diverse groups from the coast of Africa, the Persian Gulf, Southeast Asia and Madagascar.
===Europeans===
Portuguese explorers first visited the archipelago in 1505.
Apart from a visit by the French Parmentier brothers in 1529, for much of the 16th century the only Europeans to visit the islands were Portuguese. British and Dutch ships began arriving around the start of the 17th century and the island of Ndzwani soon became a major supply point on the route to the East Indies. Ndzwani was generally ruled by a single sultan, who occasionally attempted to extend his authority to Mayotte and Mwali; Ngazidja was more fragmented, on occasion being divided into as many as 12 small kingdoms.
Sir James Lancaster's voyage to the Indian Ocean in 1591 was the first attempt by the English to break into the spice trade, which was dominated by the Portuguese. Only one of his four ships made it back from the Indies on that voyage, and that one with a decimated crew of 5 men and a boy. Lancaster himself was marooned by a cyclone on the Comoros. Many of his crew were speared to death by angry islanders although Lancaster found his way home in 1594. (Dalrymple W. 2019; Bloomsbury Publishing ).
Both the British and the French turned their attention to the Comoros islands in the middle of the 19th century. The French finally acquired the islands through a cunning mixture of strategies, including the policy of "divide and conquer", chequebook politics and a serendipitous affair between a sultana and a French trader that was put to good use by the French, who kept control of the islands, quelling unrest and the occasional uprising.
William Sunley, a planter and British Consul from 1848 to 1866, was an influence on Anjouan.
==French Comoros==
France's presence in the western Indian Ocean dates to the early 17th century. The French established a settlement in southern Madagascar in 1634 and occupied the islands of Réunion and Rodrigues; in 1715 France claimed Mauritius (), and in 1756 Seychelles. Mahore offered a suitable site for port facilities, and its acquisition was justified by de Hell on the grounds that if France did not act, Britain would occupy the island.
Although France had established a foothold in Comoros, the acquisition of the other islands proceeded fitfully.
On September 25, 1942, British forces landed in the Comoros, occupying them until October 13, 1946.
In 1946 the Comoro Islands became an overseas department of France with representation in the French National Assembly. The following year, the islands' administrative ties to Madagascar were severed; Comoros established its own customs regime in 1952. and the mercenaries were given key positions in government.
In two referendums, in December 1974 and February 1976, the population of Mayotte voted against independence from France (by 63.8% and 99.4% respectively). Mayotte thus remains under French administration, and the Comorian Government has effective control over only Grande Comore, Anjouan, and Mohéli.
Later, French settlers, French-owned companies, and Arab merchants established a plantation-based economy that now uses about one-third of the land for export crops.
==Abdallah regime==
In 1978, president Ali Soilih, who had a firm anti-French line, was killed and Ahmed Abdallah came to power. Under the reign of Abdallah, Denard was commander of the Presidential Guard (PG) and de facto ruler of the country. He was trained, supported and funded by the white regimes in South Africa (SA) and Rhodesia (now Zimbabwe) in return for permission to set up a secret listening post on the islands. South-African agents kept an ear on the important ANC bases in Lusaka and Dar es Salaam and watched the war in Mozambique, in which SA played an active role. The Comoros were also used for the evasion of arms sanctions.
When in 1981 François Mitterrand was elected president Denard lost the support of the French intelligence service, but he managed to strengthen the link between SA and the Comoros. Besides the military, Denard established his own company SOGECOM, for both the security and construction, and seemed to profit by the arrangement. Between 1985 and 1987 the relationship of the PG with the local Comorians became worse.
At the end of the 1980s the South Africans did not wish to continue to support the mercenary regime and France was in agreement. Also President Abdallah wanted the mercenaries to leave. Their response was a (third) coup resulting in the death of President Abdallah, in which Denard and his men were probably involved. South Africa and the French government subsequently forced Denard and his mercenaries to leave the islands in 1989.
==1989–1996==
Said Mohamed Djohar became president. His time in office was turbulent, including an impeachment attempt in 1991 and a coup attempt in 1992.
On September 28, 1995 Bob Denard and a group of mercenaries took over the Comoros islands in a coup (named operation Kaskari by the mercenaries) against President Djohar. France immediately and severely denounced the coup, and backed by the 1978 defense agreement with the Comoros, President Jacques Chirac ordered his special forces to retake the island. Bob Denard began to take measures to stop the coming invasion. A new presidential guard was created. Strong points armed with heavy machine guns were set up around the island, particularly around the island's two airports.
On October 3, 1995, 11 p.m., the French deployed 600 men against a force of 33 mercenaries and a 300-man dissident force. Denard however ordered his mercenaries not to fight. Within 7 hours the airports at Iconi and Hahaya and the French Embassy in Moroni were secured. By 3:00 p.m. the next day Bob Denard and his mercenaries had surrendered. This (response) operation, codenamed Azalée, was remarkable, because there were no casualties, and just in seven days, plans were drawn up and soldiers were deployed. Denard was taken to France and jailed. Prime minister Caambi El-Yachourtu became acting president until Djohar returned from exile in January, 1996. In March 1996, following presidential elections, Mohamed Taki Abdoulkarim, a member of the civilian government that Denard had tried to set up in October 1995, became president. On 23 November 1996, Ethiopian Airlines Flight 961 crashed near a beach on the island after it was hijacked and ran out of fuel killing 125 people and leaving 50 survivors.
==Secession of Anjouan and Mohéli==
In 1997, the islands of Anjouan and Mohéli declared their independence from the Comoros. A subsequent attempt by the government to re-establish control over the rebellious islands by force failed, and presently the African Union is brokering negotiations to effect a reconciliation. This process is largely complete, at least in theory. According to some sources, Mohéli did return to government control in 1998. In 1999, Anjouan had internal conflicts and on August 1 of that year, the 80-year-old first president Foundi Abdallah Ibrahim resigned, transferring power to a national coordinator, Said Abeid. The government was overthrown in a coup by army and navy officers on August 9, 2001. Mohamed Bacar soon rose to leadership of the junta that took over and by the end of the month he was the leader of the country. Despite two coup attempts in the following three months, including one by Abeid, Bacar's government remained in power, and was apparently more willing to negotiate with the Comoros. Presidential elections were held for all of the Comoros in 2002, and presidents have been chosen for all three islands as well, which have become a confederation. Most notably, Mohammed Bacar was elected for a 5-year term as president of Anjouan. Grande Comore had experienced troubles of its own in the late 1990s, when President Taki died on November 6, 1998. Colonel Azali Assoumani became president following a military coup in 1999. There have been several coup attempts since, but he gained firm control of the country after stepping down temporarily and winning a presidential election in 2002.
In May 2006, Ahmed Abdallah Sambi was elected from the island of Anjouan to be the president of the Union of the Comoros. He is a Sunni cleric who studied in the Sudan, Iran and Saudi Arabia. He is nicknamed "Ayatollah" due to his time in Iran and his penchant for turbans. Sambi was sentenced to life in imprisonment in the Comoros passport sales scandal.
==2007–2008 Anjouan crisis==
== Azali Assoumani in power since 2016 ==
Azali Assoumani is a former army officer, first came to power in a coup in 1999. Then he won presidency in 2002 election, having power until 2006. After ten years, he was elected again in 2016 election. In March 2019, he was re-elected in the elections opposition claimed to be full of irregularities.
Before the 2019 election president Azali Assoumani had arranged a constitutional referendum in 2018 that approved extending the presidential mandate from one five-year term to two. The opposition had boycotted the referendum.
In January 2020, his party The Convention for the Renewal of the Comoros (CRC) won 20 out of 24 parliamentary seats in the parliamentary election.
On 18 February 2023 the Comoros assumed the presidency of the African Union. In January 2024, President Azali Assoumani was re-elected with 63% of the vote in the disputed presidential election.
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6,001 |
Geography of the Comoros
|
The Comoros archipelago consists of four main islands aligned along a northwest–southeast axis at the north end of the Mozambique Channel, between Mozambique and the island of Madagascar. Still widely known by their French names, the islands officially have been called by their Swahili names by the Comorian government. They are Grande Comore (Njazidja), Mohéli (Mwali), Anjouan (Nzwani), and Mayotte (Mahoré). The islands' distance from each other—Grande Comore is some 200 kilometers from Mayotte, forty kilometers from Mohéli, and eighty kilometers from Anjouan—along with a lack of good harbor facilities, make transportation and communication difficult. Comoros are sunny islands.
==Details==
The islands have a total land area of 2,236 square kilometers (including Mayotte), and claim territorial waters of 320 square kilometers. Mount Karthala (2316 m) on Grande Comore is an active volcano. From April 17 to 19, 2005, the volcano began spewing ash and gas, forcing as many as 10,000 people to flee. Comoros is located within the Somali Plate.
==Grande Comore==
Grande Comore is the largest island, sixty-seven kilometers long and twenty-seven kilometers wide, with a total area of 1,146 square kilometers. The most recently formed of the four islands in the archipelago, it is also of volcanic origin. Two volcanoes form the island's most prominent topographic features: La Grille in the north, with an elevation of 1,000 meters, is extinct and largely eroded; Kartala in the south, rising to a height of 2,361 meters, last erupted in 1977. A plateau averaging 600 to 700 meters high connects the two mountains. Because Grande Comore is geologically a relatively new island, its soil is thin and rocky and cannot hold water. As a result, water from the island's heavy rainfall must be stored in catchment tanks. There are no coral reefs along the coast, and the island lacks a good harbor for ships. One of the largest remnants of the Comoros' once-extensive rain forests is on the slopes of Kartala. The national capital has been at Moroni since 1962.
==Anjouan==
Anjouan, triangular shaped and forty kilometers from apex to base, has an area of 424 square kilometers. Three mountain chains — Sima, Nioumakele, and Jimilime—emanate from a central peak, Mtingui (1,575 m), giving the island its distinctive shape. Older than Grande Comore, Anjouan has deeper soil cover, but overcultivation has caused serious erosion. A coral reef lies close to shore; the island's capital of Mutsamudu is also its main port.
==Mohéli==
Mohéli is thirty kilometers long and twelve kilometers wide, with an area of 290 square kilometers. It is the smallest of the four islands and has a central mountain chain reaching 860 meters at its highest. Like Grande Comore, it retains stands of rain forest. Mohéli's capital is Fomboni.
==Mayotte==
Mayotte, geologically the oldest of the four islands, is thirty-nine kilometers long and twenty-two kilometers wide, totaling 375 square kilometers, and its highest points are between 500 and 600 meters above sea level. Because of greater weathering of the volcanic rock, the soil is relatively rich in some areas. A well-developed coral reef that encircles much of the island ensures protection for ships and a habitat for fish. Dzaoudzi, capital of the Comoros until 1962 and now Mayotte's administrative center, is situated on a rocky outcropping off the east shore of the main island. Dzaoudzi is linked by a causeway to le Pamanzi, which at ten kilometers in area is the largest of several islets adjacent to Mayotte. Islets are also scattered in the coastal waters of Mayotte just as in Grande Comore, Anjouan, and Mohéli.
==Flora and fauna==
Comorian waters are the habitat of the coelacanth, a rare fish with limblike fins and a cartilaginous skeleton, the fossil remains of which date as far back as 400 million years and which was once thought to have become extinct about 70 million years ago. A live specimen was caught in 1938 off southern Africa; other coelacanths have since been found in the vicinity of the Comoro Islands.
Several mammals are unique to the islands themselves. Livingstone's fruit bat, although plentiful when discovered by explorer David Livingstone in 1863, has been reduced to a population of about 120, entirely on Anjouan. The world's largest bat, the jet-black Livingstone fruit bat has a wingspan of nearly two meters. A British preservation group sent an expedition to the Comoros in 1992 to bring some of the bats to Britain to establish a breeding population.
A hybrid of the common brown lemur (Eulemur fulvus) originally from Madagascar, was introduced by humans prior to European colonization and is found on Mayotte. The mongoose lemur (Eulemur mongoz), also introduced from Madagascar by humans, can be found on the islands of Mohéli and Anjouan.
22 species of bird are unique to the archipelago and 17 of these are restricted to the Union of the Comoros. These include the Karthala scops-owl, Anjouan scops-owl and Humblot's flycatcher.
Partly in response to international pressures, Comorians in the 1990s have become more concerned about the environment. Steps are being taken not only to preserve the rare fauna, but also to counteract degradation of the environment, especially on densely populated Anjouan. Specifically, to minimize the cutting down of trees for fuel, kerosene is being subsidized, and efforts are being made to replace the loss of the forest cover caused by ylang-ylang distillation for perfume. The Community Development Support Fund, sponsored by the International Development Association (IDA, a World Bank affiliate) and the Comorian government, is working to improve water supply on the islands as well.
==Climate==
The climate is marine tropical, with two seasons: hot and humid from November to April, the result of the northeastern monsoon, and a cooler, drier season the rest of the year. Average monthly temperatures range from along the coasts. Although the average annual precipitation is , water is a scarce commodity in many parts of the Comoros. Mohéli and Mayotte possess streams and other natural sources of water, but Grande Comore and Anjouan, whose mountainous landscapes retain water poorly, are almost devoid of naturally occurring running water. Cyclones, occurring during the hot and wet season, can cause extensive damage, especially in coastal areas. On the average, at least twice each decade houses, farms, and harbor facilities are devastated by these great storms.
===Tropical cyclones===
Due to their low latitude, the islands are rarely affected by tropical cyclones. However, several cyclones have had damaging and deadly effects. Cyclones in December 1905 and again in December 1906 led to a famine that killed 490 people between August 1905 and January 1906. A tropical cyclone in 1950 killed 585 people while moving through Anjouan and Moheli, injuring 70,000 others. The cyclone left 40,000 people homeless, and also caused ₣3.5 worth of damage to crops and infrastructure.
===Weather===
== Extreme points ==
This is a list of the extreme points of the Comoros, the points that are farther north, south, east or west than any other location. This list excludes the French-administered island of Mayotte which is claimed by the Comorian government.
Northernmost point – unnamed headland north-west of Bangoua Kouni, Grande Comore
Easternmost point – unnamed peninsula east of Domoni, Anjouan
Southernmost point - unnamed headland on Ile Canzouni, Mohéli
Westernmost point - unnamed headland west of Iconi, Grande Comore
== Statistics ==
Area:
2,235 km2
Coastline:
340 km
Climate:
tropical marine; rainy season (November to May)
Terrain:
volcanic islands, interiors vary from steep mountains to low hills
Elevation extremes:
lowest point:
Indian Ocean 0 m
highest point:
Karthala 2,360 m
Natural resources:
fish
Land use:
arable land:
47.29%
permanent crops:
29.55%
other:
23.16% (2012 est.)
Irrigated land:
1.3 km2 (2003)
Total renewable water resources:
1.2 km3 (2011)
Freshwater withdrawal (domestic/industrial/agricultural):
total:
0.01 km3/yr (48%/5%/47%)
per capital:
16.86 m3/yr (1999)
Natural hazards:
cyclones possible during rainy season (December to April); volcanic activity on Grand Comore
Environmental - current issues:
soil degradation and erosion results from crop cultivation on slopes without proper terracing; deforestation
|
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"Madagascar",
"coral reef",
"Iconi",
"deforestation",
"Mount Karthala",
"Swahili language",
"Karthala scops-owl",
"Karthala",
"Mozambique Channel",
"Grande Comore",
"Ile Canzouni",
"Humblot's flycatcher",
"soil erosion",
"Mayotte",
"Anjouan",
"common brown lemur",
"Mozambique",
"Comoros archipelago",
"mongoose lemur",
"soil degradation",
"Somali Plate",
"Mohéli",
"peninsula",
"Mutsamudu",
"Danish Meteorological Institute",
"coelacanth",
"cyclone",
"Indian Ocean",
"Anjouan scops-owl",
"Grand Comore",
"WP:SDNONE",
"kerosene",
"Bangoua Kouni",
"World Meteorological Organization",
"Logistics Cluster",
"Domoni"
] |
6,002 |
Demographics of the Comoros
|
The Comorians () inhabiting Grande Comore, Anjouan, and Mohéli (86% of the population) share African-Arab origins. Islam is the dominant religion, and Quranic schools for children reinforce its influence. Although Islamic culture is firmly established throughout, a small minority are Christian.
The most common language is Comorian, related to Swahili. French and Arabic also are spoken. About 89% of the population is literate.
The Comoros have had eight censuses since World War II:
1951
1956
1958-09-07: 183,133
1966-07-06
Note: in 1974 Mayotte was removed from the Comoros
1980-09-15: 335,150
1991-09-15: 446,817
2003-09-15: 575,660
2017-12-15: 758,316
The latest official estimate (for 1 July 2020) is 897,219.
Population density figures conceal a great disparity between the republic's most crowded island, Nzwani, which had a density of 772 persons per square kilometer in 2017; Njazidja, which had a density of 331 persons per square kilometer in 2017; and Mwali, where the 2017 population density figure was 178 persons per square kilometer.
By comparison, estimates of the population density per square kilometer of the Indian Ocean's other island microstates ranged from 241 (Seychelles) to 690 (Maldives) in 1993. Given the rugged terrain of Njazidja and Nzwani, and the dedication of extensive tracts to agriculture on all three islands, population pressures on the Comoros are becoming increasingly critical.
The age structure of the population of the Comoros is similar to that of many developing countries, in that the republic has a very large proportion of young people. In 1989, 46.4 percent of the population was under fifteen years of age, an above-average proportion even for sub-Saharan Africa. The population's rate of growth was a relatively high 3.5 percent per annum in the mid-1980s, up substantially from 2.0 percent in the mid-1970s and 2.1 percent in the mid-1960s.
In 1983 the Abdallah regime borrowed US$2.85 million from the International Development Association to devise a national family planning program. However, Islamic reservations about contraception made forthright advocacy and implementation of birth control programs politically hazardous, and consequently little was done in the way of public policy.
The Comorian population has become increasingly urbanized in recent years. In 1991 the percentage of Comorians residing in cities and towns of more than 5,000 persons was about 30 percent, up from 25 percent in 1985 and 23 percent in 1980. The Comoros' largest cities were the capital, Moroni, with about 30,000 people, and the port city of Mutsamudu, on the island of Nzwani, with about 20,000 people.
Migration among the various islands is important. Natives of Nzwani have settled in significant numbers on less crowded Mwali, causing some social tensions, and many Nzwani also migrate to Maore. In 1977 Maore expelled peasants from Ngazidja and Nzwani who had recently settled in large numbers on the island. Some were allowed to reenter starting in 1981 but solely as migrant labor.
The number of Comorians living abroad has been estimated at between 80,000 and 100,000; during the colonial period, most of them lived in Tanzania, Madagascar, and other parts of Southeast Africa. The number of Comorians residing in Madagascar was drastically reduced after anti-Comorian rioting in December 1976 in Mahajanga, in which at least 1,400 Comorians were killed. As many as 17,000 Comorians left Madagascar to seek refuge in their native land in 1977 alone. About 100,000 Comorians live in France; many of them had gone there for a university education and never returned. Small numbers of Indians, Malagasy, South Africans, and Europeans (mostly French) live on the islands and play an important role in the economy. Most French left after independence in 1975.
Some Persian Gulf countries started buying Comorian citizenship for their stateless Bedoon residents and deporting them to Comoros.
==Population==
===UN population projections===
==Vital statistics==
Statistics :
===Demographic and Health Surveys===
Total Fertility Rate (TFR) (Wanted Fertility Rate) and Crude Birth Rate (CBR):
Structure of the population (DHS 2012) (Males 11 088, Females 12 284 = 23 373) :
Fertility data as of 2012 (DHS Program):
==Languages==
Arabic (official), French (official), Comorian (official)
==Religion==
Sunni Muslim 98%, other (including Shia Muslim, Roman Catholic, Jehovah's Witness, Protestant) 2%
note: Sunni Islam is the state religion
|
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"literate",
"Malagasy people",
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"urbanisation",
"Islam",
"Grande Comore",
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"International Development Association",
"Southeast Africa",
"fertility rate",
"Arabic language",
"Statelessness",
"Tanzania",
"Mayotte",
"the Comoros",
"Comoros",
"Anjouan",
"Persian Gulf",
"citizenship",
"family planning",
"Mohéli",
"Bedoon",
"French people",
"Mutsamudu",
"contraception",
"Moroni, Comoros",
"Comorian language",
"Mwali",
"birth control",
"Quranic school",
"Demographics of Mayotte",
"TheGuardian.com",
"Islam in the Comoros",
"net reproduction rate",
"Nzwani"
] |
6,003 |
Politics of the Comoros
|
The Politics of the Union of the Comoros take place in a framework of a unitary presidential republic, whereby the President of the Comoros is both head of state and head of government, and of a multi-party system. Executive power is exercised by the government. Legislative power is vested in both the government and parliament. The precolonial legacies of the sultanates linger while the political situation in Comoros has been extremely fluid since the country's independence in 1975, subject to the volatility of coups and political insurrection.
As of 2008, Comoros and Mauritania were considered by US-based organization Freedom House as the only real “electoral democracies” of the Arab World.
==Precolonial and colonial political structures==
Sultanates in the late nineteenth century used a cyclic age system and hierarchical lineage membership to provide the foundation for participation in the political process. In the capital, "the sultan was assisted by his ministers and by a madjelis, an advisory council composed of elders, whom he consulted regularly". Apart from local administration, the age system was used to include the population in decision making, depending on the scope of the decision being made. For example, the elders of the island of Njazidja held considerable influence on the authority of the sultan. French colonial administration was based on a misconception that the sultanates operated as absolute monarchs: district boundaries were the same as the sultanates', multiple new taxes forced men into wage labor on colonial plantations and was reinforced through a compulsory public labor system that had little effect on infrastructure. The political groups previously known simply as the 'green' and 'white' party became the Rassemblement Démocratique du Peuple Comorien (RDPC) and the Union Démocratique des Comores (UDC), headed by Sayyid Muhammad Cheikh and Sayyid Ibrahim. Members from both parties later merged to form OUDZIMA under the leadership of first president Ahmad Abdallah while dissidents from both created UMMA under the leadership of future president Ali Soilih.
Prince Said Ibrahim took power in 1970 but was democratically elected out of office in 1972 in favor of former French senator Ahmed Abdallah. President Abdallah declared independence for all islands, except Mayotte which remained under French administration, in 1975. The threat of renewed socioeconomic marginalization following the transfer of the capital to Ngazidja in 1962, more than social or cultural differences, underlay the island's subsequent rejection of independence.
Before the 2019 election president Azali Assoumani had arranged a constitutional referendum in 2018 that approved extending the presidential mandate from one five-year term to two. The opposition had boycotted the referendum.
In January 2020, his party The Convention for the Renewal of the Comoros (CRC) won 20 out of 24 parliamentary seats in the parliamentary election.
On 18 February 2023 the Comoros assumed the presidency of the African Union. In January 2024, President Azali Assoumani was re-elected with 63% of the vote in the disputed presidential election.
The Comoros Islands have experienced five different constitutions.
== First Constitution: Federal Islamic Republic of the Comoros, 1978-1989 ==
Source:
A referendum took place on May 16, 2009, to decide whether to cut down the government's unwieldy political bureaucracy. 52.7% of those eligible voted, and 93.8% of votes were cast in approval of the referendum. The referendum would cause each island's president to become a governor and the ministers to become councilors.
==Autonomous islands==
The constitution gives Grande Comore, Anjouan and Mohéli the right to govern most of their own affairs with their own presidents, except the activities assigned to the Union of the Comoros like foreign Policy, defense, nationality, banking and others. Comoros considers Mayotte, an overseas department of France, to be part of its territory, with an autonomous status
As of 2011, the three autonomous islands are subdivided into 16 prefectures, 54 communes, and 318 villes or villages.
==Executive branch==
|President
|Azali Assoumani
|
|26 May 2016
|}
The federal presidency is rotated between the islands' presidents.
The Union of the Comoros abolished the position of Prime Minister in 2002. The position of Vice-President of the Comoros was used 2002–2019.
==Legislative branch==
The Assembly of the Union has 33 seats, 24 elected in single seat constituencies and 9 representatives of the regional assemblies.
==Judicial branch==
The Supreme Court or Cour Supreme, has two members appointed by the president, two members elected by the Federal Assembly, one by the Council of each island, and former presidents of the republic.
==Political parties and elections==
==International organization participation==
The Comoros are member of the ACCT, ACP, AfDB, AMF, African Union, FAO, G-77, IBRD, ICAO, ICCt (signatory), ICRM, IDA, IDB, IFAD, IFC, IFRCS, ILO, IMF, InOC, Interpol, IOC, ITU, LAS, NAM, OIC, OPCW (signatory), United Nations, UNCTAD, UNESCO, UNIDO, UPU, WCO, WHO, WMO.
|
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"Comoros Presidential elections, 2002",
"International Finance Corporation",
"UNCTAD",
"League of Arab States",
"Hamada Madi",
"Comoros legislative election, 2004",
"2018 Comorian constitutional referendum",
"republic",
"Sudan",
"consociationalism",
"International Development Association",
"Union of the Comoros",
"Arab Monetary Fund",
"ACP countries",
"OPCW",
"2019 Comorian presidential election",
"Assembly of the Union of the Comoros",
"Saudi Arabia",
"Assemblies of the Autonomous Islands of the Comoros",
"Executive power",
"UNESCO",
"Ayatollah",
"2024 Comorian presidential election",
"Ahmed Abdallah Sambi",
"unitary state",
"United States",
"UPU",
"President of the Comoros",
"Mohamed Djaanfari",
"International Labour Organization",
"Vice-President of the Comoros",
"presidential system",
"Islamist",
"Heads of Government of the Comoros",
"1999 Comorian coup d'état",
"International Telecommunication Union",
"Legislative power",
"Electoral democracy",
"IBRD",
"2016 Comorian presidential election",
"IOC",
"IFAD",
"United Nations Industrial Development Organization",
"Tripartite Commission for National Reconciliation",
"ISO 3166-2:KM",
"1978 Comorian coup d'état",
"African Union",
"Mayotte",
"Anjouan",
"World Health Organization",
"Agence de Coopération Culturelle et Technique",
"Azali Assoumani",
"2020 Comorian legislative election",
"Food and Agriculture Organization",
"Freedom House",
"United Nations",
"Group of 77",
"InOC",
"International Criminal Court",
"Convention for the Renewal of the Comoros",
"2002 Comorian presidential election",
"International Monetary Fund",
"List of Presidents of Comoros",
"Interpol (organization)",
"Mohamed Taki Abdoulkarim",
"head of government",
"Grande Comore",
"Tadjidine Ben Said Massounde",
"ICAO",
"multi-party system",
"Islamic Development Bank",
"Arab World",
"Comoros",
"Organization for African Unity",
"Iran",
"Bainrifi Tarmidi",
"Mohéli",
"IFRCS",
"Non-Aligned Movement",
"WMO",
"Organisation of Islamic Cooperation",
"AfDB",
"head of state",
"overseas department",
"Mauritania",
"Ibrahim Halidi",
"World Customs Organization"
] |
6,005 |
Telecommunications in the Comoros
|
In large part thanks to international aid programs, Moroni has international telecommunications service. Telephone service, however, is largely limited to the islands' few towns.
==Overview==
Telephones – main lines in use:
5,000 (1995)
Telephones – mobile cellular:
0 (1995)
Telephone system:
sparse system of microwave radio relay and HF radiotelephone communication stations
domestic:
HF radiotelephone communications and microwave radio relay
CMDA mobile network (Huri, operated by Comores Telecom)
international:
HF radiotelephone communications to Madagascar and Réunion
Radio broadcast stations:
AM 1, FM 2, shortwave 1 (1998)
Radios:
90,000 (1997)
Television broadcast stations:
0 (1998)
Televisions:
1,000 (1997)
Internet Service Providers (ISPs): 1 (1999)
Country code (Top-level domain): .km
==Special projects==
In October 2011 the State of Qatar launched a special program for the construction of a wireless network to interconnect the three islands of the archipelago, by means of low cost, repeatable technology. The project has been developed by Qatar University and Politecnico di Torino, under the supervision of prof. Mazen Hasna and prof. Daniele Trinchero, with a major participation of local actors (Comorian Government, NRTIC, University of the Comoros). The project has been referred as an example of technology transfer and Sustainable Inclusion in developing countries
|
[
"Madagascar",
"WP:SDNONE",
"Daniele Trinchero",
"wireless network",
"Qatar University",
".km",
"Developing country",
"Broadcasting",
"technology transfer",
"microwave",
"Internet Service Provider",
"Réunion",
"Politecnico di Torino",
"Country codes"
] |
6,006 |
Transport in the Comoros
|
There are a number of systems of transport in the Comoros. The Comoros possesses of road, of which are paved. It has three seaports: Fomboni, Moroni and Moutsamoudou, but does not have a merchant marine, and no longer has any railway network. It has four airports, all with paved runways, one with runways over long, with the others having runways shorter than .
The isolation of the Comoros had made air traffic a major means of transportation. One of President Abdallah's accomplishments was to make the Comoros more accessible by air. During his administration, he negotiated agreements to initiate or enhance commercial air links with Tanzania and Madagascar. The Djohar regime reached an agreement in 1990 to link Moroni and Brussels by air. By the early 1990s, commercial flights connected the Comoros with France, Mauritius, Kenya, South Africa, Tanzania, and Madagascar. The national airline was Air Comores. Daily flights linked the three main islands, and air service was also available to Mahoré; each island had airstrips. In 1986 the republic received a grant from the French government's CCCE to renovate and expand Hahaya airport, near Moroni. Because of the absence of scheduled sea transport between the islands, nearly all interisland passenger traffic is by air.
More than 99% of freight is transported by sea. Both Moroni on Njazidja and Mutsamudu on Nzwani have artificial harbors. There is also a harbor at Fomboni, on Mwali. Despite extensive internationally financed programs to upgrade the harbors at Moroni and Mutsamudu, by the early 1990s only Mutsamudu was operational as a deepwater facility. Its harbor could accommodate vessels of up to eleven meters' draught. At Moroni, ocean-going vessels typically lie offshore and are loaded or unloaded by smaller craft, a costly and sometimes dangerous procedure. Most freight continues to be sent to Tanzania, Kenya, Reunion, or Madagascar for transshipment to the Comoros. Use of Comoran ports is further restricted by the threat of cyclones from December through March. The privately operated Comoran Navigation Company (Société Comorienne de Navigation) is based in Moroni, and provides services to Madagascar.
Roads serve the coastal areas, rather than the interior, and the mountainous terrain makes surface travel difficult.
|
[
"Fomboni",
"History of rail transport in the Comoros",
"WP:SDNONE",
"Moroni, Comoros",
"Moutsamoudou",
"CIA World Factbook",
"Comoros",
"Prince Said Ibrahim International Airport"
] |
6,007 |
Foreign relations of the Comoros
|
In November 1975, Comoros became the 143rd member of the United Nations. The new nation was defined as consisting of the entire archipelago, despite the fact that France maintains control over Mayotte.
== Overview ==
Comoros also is a member of the African Union, the Arab League, the European Development Fund, the World Bank, the International Monetary Fund, the Indian Ocean Commission, and the African Development Bank.
The government fostered close relationships with the more conservative (and oil-rich) Arab states, such as Saudi Arabia and Kuwait.
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|Unknown
|-style="background:#D3D3D3"
|—
| (suspended)
|Unknown
|}
==Bilateral relations==
|
[
"China–Comoros relations",
"Madagascar",
"List of diplomatic missions in Comoros",
"International Monetary Fund",
"Antananarivo",
"Saudi Arabia",
"Comoros–United States relations",
"Belgium",
"European Development Fund",
"League of Arab States",
"France",
"Ministry of Foreign Affairs (Uzbekistan)",
"fisheries",
"South Africa",
"Moheli",
"Kenya",
"Artemisia annua",
"Félix Tshisekedi",
"Yemen",
"primaquine",
"Cairo",
"Arab Bank for Economic Development in Africa",
"Kyiv",
"malaria",
"Grande Comore",
"Comoros–India relations",
"archipelago",
"China",
"Tanzania",
"Nairobi",
"African Union",
"Mayotte",
"Comoros",
"pyrimethamine",
"Anjouan",
"Ahmed Abdallah",
"Réunion",
"Glorioso Islands",
"Indian-Ocean Rim Association",
"Cold War",
"Brussels",
"African Development Bank",
"Arab League",
"World Bank",
"Comoros–North Korea relations",
"France–Comoros relations",
"Ali Soilih",
"Moroni, Comoros",
"Indian Ocean",
"One-China policy",
"Comoros–Qatar relations",
"Indian Ocean Commission",
"Dar es Salaam",
"Mahoré",
"Seychelles",
"Ministry of National Defense of the People's Republic of China",
"Organisation of Islamic Cooperation",
"United Nations",
"Paris",
"WP:SDNONE",
"artemisinin",
"Embassy",
"Japan",
"apartheid",
"democracy",
"Liang Guanglie",
"Said Mohamed Djohar",
"coup",
"Rome",
"Arab Fund for Economic and Social Development",
"Kuwait",
"Pretoria",
"List of diplomatic missions of Comoros",
"Mauritius"
] |
6,008 |
Army of National Development
|
The Comorian Armed Forces (; ) are the national military of the Comoros. The armed forces consist of a small standing army and a 500-member police force, as well as a 500-member defense force. A defense treaty with France provides naval resources for protection of territorial waters, training of Comorian military personnel, and air surveillance. France maintains a small troop presence in the Comoros at government request. France maintains a small Navy base and a Foreign Legion Detachment (DLEM) in Mayotte.
== Structure ==
The AND consists of the following components:
Comorian Ground Defense Force
Comorian National Gendarmerie
National School of the Armed Forces and Gendarmerie
Comorian Air Force
Comorian Presidential Guard
Comorian Military Health Services
Comorian Coast Guard
== Equipment inventory ==
FN FAL battle rifle
AK-47 assault rifle
Type 81 assault rifle
NSV HMG
RPG-7 anti-tank weapon
Mitsubishi L200 pickup truck
==Aircraft==
Note: The last comprehensive aircraft inventory list was from Aviation Week & Space Technology in 2007.
|
[
"Cessna 402",
"Mil Mi-14",
"Trainer aircraft",
"Military ranks of Comoros",
"France",
"NSV machine gun",
"Eurocopter AS350 Écureuil",
"Aérospatiale Corvette",
"Let L-410 Turbolet",
"military",
"French Navy",
"United States",
"Helicopter",
"Mitsubishi Triton",
"President of Comoros",
"Utility helicopter",
"Mayotte",
"Comoros",
"Italy",
"Air transports of heads of state and government",
"Azali Assoumani",
"SIAI-Marchetti SF.260",
"Maritime patrol aircraft",
"Moroni, Comoros",
"French Foreign Legion",
"Military transport aircraft",
"Type 81 assault rifle",
"Czech Republic",
"RPG-7",
"Foreign Legion Detachment in Mayotte",
"Aviation Week & Space Technology",
"FN FAL",
"AK-47",
"Russia"
] |
6,010 |
Computer worm
|
A computer worm is a standalone malware computer program that replicates itself in order to spread to other computers. It often uses a computer network to spread itself, relying on security failures on the target computer to access it. It will use this machine as a host to scan and infect other computers. When these new worm-invaded computers are controlled, the worm will continue to scan and infect other computers using these computers as hosts, and this behaviour will continue. Computer worms use recursive methods to copy themselves without host programs and distribute themselves based on exploiting the advantages of exponential growth, thus controlling and infecting more and more computers in a short time. Worms almost always cause at least some harm to the network, even if only by consuming bandwidth, whereas viruses almost always corrupt or modify files on a targeted computer.
Many worms are designed only to spread, and do not attempt to change the systems they pass through. However, as the Morris worm and Mydoom showed, even these "payload-free" worms can cause major disruption by increasing network traffic and other unintended effects.
==History==
The term "worm" was first used in this sense in John Brunner's 1975 novel, The Shockwave Rider. In the novel, Nichlas Haflinger designs and sets off a data-gathering worm in an act of revenge against the powerful people who run a national electronic information web that induces mass conformity. "You have the biggest-ever worm loose in the net, and it automatically sabotages any attempt to monitor it. There's never been a worm with that tough a head or that long a tail!" "Then the answer dawned on him, and he almost laughed. Fluckner had resorted to one of the oldest tricks in the store and turned loose in the continental net a self-perpetuating tapeworm, probably headed by a denunciation group "borrowed" from a major corporation, which would shunt itself from one nexus to another every time his credit-code was punched into a keyboard. It could take days to kill a worm like that, and sometimes weeks." During the Morris appeal process, the U.S. Court of Appeals estimated the cost of removing the worm from each installation at between $200 and $53,000; this work prompted the formation of the CERT Coordination Center and Phage mailing list. Morris himself became the first person tried and convicted under the 1986 Computer Fraud and Abuse Act.
Conficker, a computer worm discovered in 2008 that primarily targeted Microsoft Windows operating systems, is a worm that employs three different spreading strategies: local probing, neighborhood probing, and global probing. This worm was considered a hybrid epidemic and affected millions of computers. The term "hybrid epidemic" is used because of the three separate methods it employed to spread, which was discovered through code analysis.
== Features ==
Independence
Computer viruses generally require a host program. The virus writes its own code into the host program. When the program runs, the written virus program is executed first, causing infection and damage. A worm does not need a host program, as it is an independent program or code chunk. Therefore, it is not restricted by the host program, but can run independently and actively carry out attacks.
Exploit attacks
Because a worm is not limited by the host program, worms can take advantage of various operating system vulnerabilities to carry out active attacks. For example, the "Nimda" virus exploits vulnerabilities to attack.
Complexity
Some worms are combined with web page scripts, and are hidden in HTML pages using VBScript, ActiveX and other technologies. When a user accesses a webpage containing a virus, the virus automatically resides in memory and waits to be triggered. There are also some worms that are combined with backdoor programs or Trojan horses, such as "Code Red".
Contagiousness
Worms are more infectious than traditional viruses. They not only infect local computers, but also all servers and clients on the network based on the local computer. Worms can easily spread through shared folders, e-mails, malicious web pages, and servers with a large number of vulnerabilities in the network.
==Harm==
Any code designed to do more than spread the worm is typically referred to as the "payload". Typical malicious payloads might delete files on a host system (e.g., the ExploreZip worm), encrypt files in a ransomware attack, or exfiltrate data such as confidential documents or passwords.
Some worms may install a backdoor. This allows the computer to be remotely controlled by the worm author as a "zombie". Networks of such machines are often referred to as botnets and are very commonly used for a range of malicious purposes, including sending spam or performing DoS attacks.
Some special worms attack industrial systems in a targeted manner. Stuxnet was primarily transmitted through LANs and infected thumb-drives, as its targets were never connected to untrusted networks, like the internet. This virus can destroy the core production control computer software used by chemical, power generation and power transmission companies in various countries around the world - in Stuxnet's case, Iran, Indonesia and India were hardest hit - it was used to "issue orders" to other equipment in the factory, and to hide those commands from being detected. Stuxnet used multiple vulnerabilities and four different zero-day exploits (e.g.: ) in Windows systems and Siemens SIMATICWinCC systems to attack the embedded programmable logic controllers of industrial machines. Although these systems operate independently from the network, if the operator inserts a virus-infected drive into the system's USB interface, the virus will be able to gain control of the system without any other operational requirements or prompts.
== Countermeasures ==
Worms spread by exploiting vulnerabilities in operating systems.
Vendors with security problems supply regular security updates (see "Patch Tuesday"), and if these are installed to a machine, then the majority of worms are unable to spread to it. If a vulnerability is disclosed before the security patch released by the vendor, a zero-day attack is possible.
Users need to be wary of opening unexpected emails, and should not run attached files or programs, or visit web sites that are linked to such emails. However, as with the ILOVEYOU worm, and with the increased growth and efficiency of phishing attacks, it remains possible to trick the end-user into running malicious code.
Anti-virus and anti-spyware software are helpful, but must be kept up-to-date with new pattern files at least every few days. The use of a firewall is also recommended.
Users can minimize the threat posed by worms by keeping their computers' operating system and other software up to date, avoiding opening unrecognized or unexpected emails and running firewall and antivirus software.
Mitigation techniques include:
ACLs in routers and switches
Packet-filters
TCP Wrapper/ACL enabled network service daemons
EPP/EDR software
Nullroute
Infections can sometimes be detected by their behavior - typically scanning the Internet randomly, looking for vulnerable hosts to infect. In addition, machine learning techniques can be used to detect new worms, by analyzing the behavior of the suspected computer.
==Helpful worms==
A helpful worm or anti-worm is a worm designed to do something that its author feels is helpful, though not necessarily with the permission of the executing computer's owner. Beginning with the first research into worms at Xerox PARC, there have been attempts to create useful worms. Those worms allowed John Shoch and Jon Hupp to test the Ethernet principles on their network of Xerox Alto computers. Similarly, the Nachi family of worms tried to download and install patches from Microsoft's website to fix vulnerabilities in the host system by exploiting those same vulnerabilities. In practice, although this may have made these systems more secure, it generated considerable network traffic, rebooted the machine in the course of patching it, and did its work without the consent of the computer's owner or user. Regardless of their payload or their writers' intentions, security experts regard all worms as malware. Another example of this approach is Roku OS patching a bug allowing for Roku OS to be rooted via an update to their screensaver channels, which the screensaver would attempt to connect to the telnet and patch the device.
One study proposed the first computer worm that operates on the second layer of the OSI model (Data link Layer), utilizing topology information such as Content-addressable memory (CAM) tables and Spanning Tree information stored in switches to propagate and probe for vulnerable nodes until the enterprise network is covered.
Anti-worms have been used to combat the effects of the Code Red, Blaster, and Santy worms. Welchia is an example of a helpful worm. Utilizing the same deficiencies exploited by the Blaster worm, Welchia infected computers and automatically began downloading Microsoft security updates for Windows without the users' consent. Welchia automatically reboots the computers it infects after installing the updates. One of these updates was the patch that fixed the exploit.
|
[
"ExploreZip",
"The Shockwave Rider",
"Computer virus",
"Recursion (computer science)",
"Bandwidth (computing)",
"Reaper (program)",
"malware",
"Email spam",
"ACL (software)",
"Microsoft Windows",
"XSS worm",
"Blaster worm",
"Nullroute",
"Exploit (computer security)",
"Code Shikara (Worm)",
"Access Control List",
"Content-addressable memory",
"Mydoom",
"Stuxnet",
"CEO",
"Worm memory test",
"botnets",
"Santy",
"Xerox Alto",
"zombie computers",
"exponential growth",
"ransomware",
"Blaster (computer worm)",
"John Shoch",
"Microsoft",
"Ray Tomlinson",
"Network switch",
"Technical support scam",
"ARPANET",
"Robert Tappan Morris",
"computer program",
"HTML",
"CERT Coordination Center",
"Morris worm",
"Self-replicating machine",
"Computer and network surveillance",
"VBScript",
"computer network",
"Conficker",
"SIMATIC WinCC",
"Nimda",
"Timeline of computer viruses and worms",
"Firewall (computing)",
"Antivirus software",
"Xerox PARC",
"TCP Wrapper",
"ActiveX",
"BlueKeep (security vulnerability)",
"daemon (computer software)",
"John Brunner (novelist)",
"Welchia",
"zero-day attack",
"Windows",
"GitHub",
"Endpoint detection and response",
"Cornell University",
"Firewall (networking)",
"Backdoor (computing)",
"Zombie (computer science)",
"Denial-of-service attack",
"Computer security",
"Router (computing)",
"Ethernet",
"Father Christmas (computer worm)",
"shared folder",
"Roku OS",
"Data theft",
"Computer Fraud and Abuse Act",
"phishing",
"Nachi worm",
"ILOVEYOU",
"master status",
"e-mail spam",
"Endpoint protection",
"List of computer worms",
"OSI model",
"Antispyware",
"Patch Tuesday",
"Vulnerability (computing)",
"Code Red (computer worm)",
"Creeper (program)",
"Computer program",
"Email",
"Trojan horse (computing)",
"Botnet",
"Payload (software)",
"Bill Gates"
] |
6,011 |
Chomsky hierarchy
|
The Chomsky hierarchy in the fields of formal language theory, computer science, and linguistics, is a containment hierarchy of classes of formal grammars. A formal grammar describes how to form strings from a language's vocabulary (or alphabet) that are valid according to the language's syntax. The linguist Noam Chomsky theorized that four different classes of formal grammars existed that could generate increasingly complex languages. Each class can also completely generate the language of all inferior classes (set inclusive).
== History ==
The general idea of a hierarchy of grammars was first described by Noam Chomsky in "Three models for the description of language" during the formalization of transformational-generative grammar (TGG). Marcel-Paul Schützenberger also played a role in the development of the theory of formal languages; the paper "The algebraic theory of context free languages" describes the modern hierarchy, including context-free grammars.
Independently, alongside linguists, mathematicians were developing models of computation (via automata). Parsing a sentence in a language is similar to computation, and the grammars described by Chomsky proved to both resemble and be equivalent in computational power to various machine models.
== The hierarchy ==
The following table summarizes each of Chomsky's four types of grammars, the class of language it generates, the type of automaton that recognizes it, and the form its rules must have. The classes are defined by the constraints on the productions rules.
Note that the set of grammars corresponding to recursive languages is not a member of this hierarchy; these would be properly between Type-0 and Type-1.
Every regular language is context-free, every context-free language is context-sensitive, every context-sensitive language is recursive and every recursive language is recursively enumerable. These are all proper inclusions, meaning that there exist recursively enumerable languages that are not context-sensitive, context-sensitive languages that are not context-free and context-free languages that are not regular.
===Regular (Type-3) grammars===
Type-3 grammars generate the regular languages. Such a grammar restricts its rules to a single nonterminal on the left-hand side and a right-hand side consisting of a single terminal, possibly followed by a single nonterminal, in which case the grammar is right regular. Alternatively, all the rules can have their right-hand sides consist of a single terminal, possibly preceded by a single nonterminal (left regular). These generate the same languages. However, if left-regular rules and right-regular rules are combined, the language need no longer be regular. The rule S \rightarrow \varepsilon is also allowed here if S does not appear on the right side of any rule. These languages are exactly all languages that can be decided by a finite-state automaton. Additionally, this family of formal languages can be obtained by regular expressions. Regular languages are commonly used to define search patterns and the lexical structure of programming languages.
For example, the regular language L = \{a^n \mid n > 0\} is generated by the Type-3 grammar G = (\{S\}, \{a, b\}, P, S) with the productions P being the following.
===Context-free (Type-2) grammars===
Type-2 grammars generate the context-free languages. These are defined by rules of the form A \rightarrow \alpha with A being a nonterminal and \alpha being a string of terminals and/or nonterminals. These languages are exactly all languages that can be recognized by a non-deterministic pushdown automaton. Context-free languages—or rather its subset of deterministic context-free languages—are the theoretical basis for the phrase structure of most programming languages, though their syntax also includes context-sensitive name resolution due to declarations and scope. Often a subset of grammars is used to make parsing easier, such as by an LL parser.
For example, the context-free language L = \{a^nb^n \mid n > 0\} is generated by the Type-2 grammar G = (\{S\}, \{a, b\}, P, S) with the productions P being the following.
The language is context-free but not regular (by the pumping lemma for regular languages).
===Context-sensitive (Type-1) grammars===
Type-1 grammars generate context-sensitive languages. These grammars have rules of the form \alpha A\beta \rightarrow \alpha\gamma\beta with A a nonterminal and \alpha, \beta and \gamma strings of terminals and/or nonterminals. The strings \alpha and \beta may be empty, but \gamma must be nonempty. The rule S \rightarrow \epsilon is allowed if S does not appear on the right side of any rule. The languages described by these grammars are exactly all languages that can be recognized by a linear bounded automaton (a nondeterministic Turing machine whose tape is bounded by a constant times the length of the input.)
For example, the context-sensitive language L = \{a^nb^nc^n \mid n > 0\} is generated by the Type-1 grammar G = (\{S,A,B,C,W,Z\}, \{a, b, c\}, P, S) with the productions P being the following.
The language is context-sensitive but not context-free (by the pumping lemma for context-free languages).
A proof that this grammar generates L = \{a^nb^nc^n \mid n > 0\} is sketched in the article on Context-sensitive grammars.
===Recursively enumerable (Type-0) grammars===
Type-0 grammars include all formal grammars. There are no constraints on the productions rules. They generate exactly all languages that can be recognized by a Turing machine, thus any language that is possible to be generated can be generated by a Type-0 grammar. Note that this is different from the recursive languages, which can be decided by an always-halting Turing machine.
|
[
"Finite-state automaton",
"programming language",
"context-sensitive grammar",
"Noam Chomsky",
"Name resolution (programming languages)",
"pumping lemma for context-free languages",
"transformational-generative grammar",
"Hierarchy",
"Terminal symbol",
"pumping lemma for regular languages",
"recursive language",
"formal language",
"computer science",
"deterministic context-free language",
"context-free grammar",
"finite-state automaton",
"context-free language",
"Scope (computer science)",
"Unrestricted grammar",
"recursively enumerable language",
"Chomsky normal form",
"LL parser",
"linear bounded automaton",
"pushdown automaton",
"regular expression",
"Nonterminal symbol",
"automata",
"Linear bounded automaton",
"linguistics",
"Context-sensitive grammar",
"Marcel-Paul Schützenberger",
"Turing machine",
"context-sensitive language",
"regular language",
"formal grammar",
"machine that always halts",
"regular grammar"
] |
6,013 |
CRT
|
CRT or Crt most commonly refers to:
Cathode-ray tube, a display
Critical race theory, an academic framework of analysis
CRT may also refer to:
==Law==
Charitable remainder trust, United States
Civil Resolution Tribunal, Canada
Columbia River Treaty, Canada–US, 1960s
==Science, technology, and mathematics==
===Medicine and biology===
Calreticulin, a protein
Capillary refill time, for blood to refill capillaries
Cardiac resynchronization therapy and CRT defibrillator (CRT-D)
Catheter-related thrombosis, the development of a blood clot related to long-term use of central venous catheters
Certified Respiratory Therapist
Chemoradiotherapy, chemo- and radiotherapy combined
Cognitive Retention Therapy, for dementia
Corneal Refractive Therapy, in optometrics
CRT (genetics), a gene cluster
===Social sciences===
Cognitive reflection test, in psychology
Current reality tree (theory of constraints), in process management
Culturally relevant teaching, in pedagogy
===Technology===
Microsoft C Run-Time library
SecureCRT, formerly CRT, a telnet client
.crt, X.509 Certificate filename extension
===Other uses in science and mathematics===
Chinese remainder theorem, in number theory
Crater (constellation), in astronomy (abbreviated )
==Transport==
Canal & River Trust, England and Wales
Changchun Rail Transit, China
Chongqing Rail Transit, China
Connecticut River Transit, a defunct American bus service
Cross River Tram, a defunct proposal in London, England
CRT Group, an Australian transport company
Chicago Rapid Transit Company, a defunct American rail company
Colchester Rapid Transit, a rapid-transit system in Colchester, England.
==Other uses==
Canadian Railway Troops, WWI
Claiming Rule Teams, in motorcycle racing
Connecticut Repertory Theatre, University of Connecticut
Correctional Emergency Response Team
Iyojwaʼja Chorote, a language in Salta province, Argentina, ISO 639 code
Tochigi Broadcasting, a radio station in Tochigi Prefecture, Japan
|
[
"CRT Group",
"CRT (genetics)",
"Chinese remainder theorem",
"Critical race theory",
"Chemoradiotherapy",
"X.509",
"Central venous catheter",
"Charitable trust",
"Civil Resolution Tribunal",
"Certified Respiratory Therapist",
"Connecticut Repertory Theatre",
"Changchun Rail Transit",
"Columbia River Treaty",
"Claiming Rule Teams",
"Cognitive Retention Therapy",
"Corneal Refractive Therapy",
"Canadian Railway Troops",
"Current reality tree (theory of constraints)",
"Cognitive reflection test",
"SecureCRT",
"Culturally relevant teaching",
"Correctional Emergency Response Team",
"Canal & River Trust",
"Calreticulin",
"Capillary refill",
"Windows library files",
"Iyojwaʼja Chorote",
"Chicago Rapid Transit Company",
"Crater (constellation)",
"Cathode-ray tube",
"Chongqing Rail Transit",
"Cross River Tram",
"Colchester Rapid Transit",
"Connecticut River Transit",
"Tochigi Broadcasting",
"Cardiac resynchronization therapy"
] |
6,014 |
Cathode-ray tube
|
A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a frame of video on an analog television set (TV), digital raster graphics on a computer monitor, or other phenomena like radar targets. A CRT in a TV is commonly called a picture tube. CRTs have also been used as memory devices, in which case the screen is not intended to be visible to an observer. The term cathode ray was used to describe electron beams when they were first discovered, before it was understood that what was emitted from the cathode was a beam of electrons.
In CRT TVs and computer monitors, the entire front area of the tube is scanned repeatedly and systematically in a fixed pattern called a raster. In color devices, an image is produced by controlling the intensity of each of three electron beams, one for each additive primary color (red, green, and blue) with a video signal as a reference. In modern CRT monitors and TVs the beams are bent by magnetic deflection, using a deflection yoke. Electrostatic deflection is commonly used in oscilloscopes. As such, handling a CRT carries the risk of violent implosion that can hurl glass at great velocity. The face is typically made of thick lead glass or special barium-strontium glass to be shatter-resistant and to block most X-ray emissions. This tube makes up most of the weight of CRT TVs and computer monitors.
Since the early 2010s, CRTs have been superseded by flat-panel display technologies such as LCD, plasma display, and OLED displays which are cheaper to manufacture and run, as well as significantly lighter and thinner. Flat-panel displays can also be made in very large sizes whereas was about the largest size of a CRT.
A CRT works by electrically heating a tungsten coil which in turn heats a cathode in the rear of the CRT, causing it to emit electrons which are modulated and focused by electrodes. The electrons are steered by deflection coils or plates, and an anode accelerates them towards the phosphor-coated screen, which generates light when hit by the electrons.
==History==
===Discoveries===
Cathode rays were discovered by Julius Plücker and Johann Wilhelm Hittorf. Hittorf observed that some unknown rays were emitted from the cathode (negative electrode) which could cast shadows on the glowing wall of the tube, indicating the rays were travelling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, and William Crookes showed they could be deflected by magnetic fields. In 1897, J. J. Thomson succeeded in measuring the mass-to-charge ratio of cathode rays, showing that they consisted of negatively charged particles smaller than atoms, the first "subatomic particles", which had already been named electrons by Irish physicist George Johnstone Stoney in 1891.
The earliest version of the CRT was known as the "Braun tube", invented by the German physicist Ferdinand Braun in 1897. It was a cold-cathode diode, a modification of the Crookes tube with a phosphor-coated screen. Braun was the first to conceive the use of a CRT as a display device. The Braun tube became the foundation of 20th century TV.
In 1908, Alan Archibald Campbell-Swinton, fellow of the Royal Society (UK), published a letter in the scientific journal Nature, in which he described how "distant electric vision" could be achieved by using a cathode-ray tube (or "Braun" tube) as both a transmitting and receiving device. He expanded on his vision in a speech given in London in 1911 and reported in The Times and the Journal of the Röntgen Society.
The first cathode-ray tube to use a hot cathode was developed by John Bertrand Johnson (who gave his name to the term Johnson noise) and Harry Weiner Weinhart of Western Electric, and became a commercial product in 1922. The introduction of hot cathodes allowed for lower acceleration anode voltages and higher electron beam currents, since the anode now only accelerated the electrons emitted by the hot cathode, and no longer had to have a very high voltage to induce electron emission from the cold cathode.
===Development===
In 1926, Kenjiro Takayanagi demonstrated a CRT TV receiver with a mechanical video camera that received images with a 40-line resolution. By 1927, he improved the resolution to 100 lines, which was unrivaled until 1931. By 1928, he was the first to transmit human faces in half-tones on a CRT display.
In 1927, Philo Farnsworth created a TV prototype.
The CRT was named in 1929 by inventor Vladimir K. Zworykin.
In the 1930s, Allen B. DuMont made the first CRTs to last 1,000 hours of use, which was one of the factors that led to the widespread adoption of TV.
The first commercially made electronic TV sets with cathode-ray tubes were manufactured by Telefunken in Germany in 1934.
In 1947, the cathode-ray tube amusement device, the earliest known interactive electronic game as well as the first to incorporate a cathode-ray tube screen, was created.
From 1949 to the early 1960s, there was a shift from circular CRTs to rectangular CRTs, although the first rectangular CRTs were made in 1938 by Telefunken. While circular CRTs were the norm, European TV sets often blocked portions of the screen to make it appear somewhat rectangular while American sets often left the entire front of the CRT exposed or only blocked the upper and lower portions of the CRT.
In 1954, RCA produced some of the first color CRTs, the 15GP22 CRTs used in the CT-100, the first color TV set to be mass produced. The first rectangular color CRTs were also made in 1954. However, the first rectangular color CRTs to be offered to the public were made in 1963. One of the challenges that had to be solved to produce the rectangular color CRT was convergence at the corners of the CRT.
The size of CRTs increased over time, from 20 inches in 1938, to 21 inches in 1955, 25 inches by 1974, 30 inches by 1980, 35 inches by 1985, and 43 inches by 1989. The world largest was the Sony KX-45ED1 at 45 inches but only one known working model exists.
In 1960, the Aiken tube was invented. It was a CRT in a flat-panel display format with a single electron gun. Deflection was electrostatic and magnetic, but due to patent problems, it was never put into production. It was also envisioned as a head-up display in aircraft. By the time patent issues were solved, RCA had already invested heavily in conventional CRTs.
1968 marked the release of Sony Trinitron brand with the model KV-1310, which was based on Aperture Grille technology. It was acclaimed to have improved the output brightness. The Trinitron screen was identical with its upright cylindrical shape due to its unique triple cathode single gun construction.
In 1987, flat-screen CRTs were developed by Zenith for computer monitors, reducing reflections and helping increase image contrast and brightness. Such CRTs were expensive, which limited their use to computer monitors. Attempts were made to produce flat-screen CRTs using inexpensive and widely available float glass.
In 1990, the first CRT with HD resolution, the Sony KW-3600HD, was released to the market. It is considered to be "historical material" by Japan's national museum.
The Sony KWP-5500HD, an HD CRT projection TV, was released in 1992.
In the mid-1990s, some 160 million CRTs were made per year.
In the mid-2000s, Canon and Sony presented the surface-conduction electron-emitter display and field-emission displays, respectively. They both were flat-panel displays that had one (SED) or several (FED) electron emitters per subpixel in place of electron guns. The electron emitters were placed on a sheet of glass and the electrons were accelerated to a nearby sheet of glass with phosphors using an anode voltage. The electrons were not focused, making each subpixel essentially a flood beam CRT. They were never put into mass production as LCD technology was significantly cheaper, eliminating the market for such displays.
The last large-scale manufacturer of (in this case, recycled) CRTs, Videocon, ceased in 2015. CRT TVs stopped being made around the same time.
In 2012, Samsung SDI and several other major companies were fined by the European Commission for price fixing of TV cathode-ray tubes.
The same occurred in 2015 in the US and in Canada in 2018.
Worldwide sales of CRT computer monitors peaked in 2000, at 90 million units, while those of CRT TVs peaked in 2005 at 130 million units.
===Decline===
Beginning in the late 1990s to the early 2000s, CRTs began to be replaced with LCDs, starting first with computer monitors smaller than 15 inches in size, largely because of their lower bulk. Among the first manufacturers to stop CRT production was Hitachi in 2001, followed by Sony in Japan in 2004. Flat-panel displays dropped in price and started significantly displacing cathode-ray tubes in the 2000s. LCD monitor sales began exceeding those of CRTs in 2003–2004 and LCD TV sales started exceeding those of CRTs in some markets in 2005. Samsung SDI stopped CRT production in 2012.
Despite being a mainstay of display technology for decades, CRT-based computer monitors and TVs are now obsolete. Demand for CRT screens dropped in the late 2000s. Despite efforts from Samsung and LG to make CRTs competitive with their LCD and plasma counterparts, offering slimmer and cheaper models to compete with similarly sized and more expensive LCDs, CRTs eventually became obsolete and were relegated to developing markets and vintage enthusiasts once LCDs fell in price, with their lower bulk, weight and ability to be wall mounted coming as advantages.
Some industries still use CRTs because it is too much effort, downtime, or cost to replace them, or there is no substitute available; a notable example is the airline industry. Planes such as the Boeing 747-400 and the Airbus A320 used CRT instruments in their glass cockpits instead of mechanical instruments. Airlines such as Lufthansa still use CRT technology, which also uses floppy disks for navigation updates. They are also used in some military equipment for similar reasons. , at least one company manufactures new CRTs for these markets.
A popular consumer usage of CRTs is for retro gaming. Some games are impossible to play without CRT display hardware. Light guns only work on CRTs because they depend on the progressive timing properties of CRTs. Another reason people use CRTs is due to the natural blending of these displays. Some games designed for CRT displays exploit this, which allows them to look more aesthetically pleasing on these displays.
==Constructions==
===Body===
The body of a CRT is usually made up of three parts: A screen/faceplate/panel, a cone/funnel, and a neck. The joined screen, funnel and neck are known as the bulb or envelope. while the funnel and screen are made by pouring and then pressing glass into a mold. The glass, known as CRT glass or TV glass, needs special properties to shield against x-rays while providing adequate light transmission in the screen or being very electrically insulating in the funnel and neck. The formulation that gives the glass its properties is also known as the melt. The glass is of very high quality, being almost contaminant and defect free. Most of the costs associated with glass production come from the energy used to melt the raw materials into glass. Glass furnaces for CRT glass production have several taps to allow molds to be replaced without stopping the furnace, to allow production of CRTs of several sizes. Only the glass used on the screen needs to have precise optical properties.
The optical properties of the glass used on the screen affect color reproduction and purity in color CRTs. Transmittance, or how transparent the glass is, may be adjusted to be more transparent to certain colors (wavelengths) of light. Transmittance is measured at the center of the screen with a 546 nm wavelength light, and a 10.16mm thick screen. Transmittance goes down with increasing thickness. Standard transmittances for Color CRT screens are 86%, 73%, 57%, 46%, 42% and 30%. Lower transmittances are used to improve image contrast but they put more stress on the electron gun, requiring more power on the electron gun for a higher electron beam power to light the phosphors more brightly to compensate for the reduced transmittance. The transmittance must be uniform across the screen to ensure color purity. The radius (curvature) of screens has increased (grown less curved) over time, from 30 to 68 inches, ultimately evolving into completely flat screens, reducing reflections. The thickness of both curved and flat screens gradually increases from the center outwards, and with it, transmittance is gradually reduced. This means that flat-screen CRTs may not be completely flat on the inside.
The glass used in CRTs arrives from the glass factory to the CRT factory as either separate screens and funnels with fused necks, for Color CRTs, or as bulbs made up of a fused screen, funnel and neck. There were several glass formulations for different types of CRTs, that were classified using codes specific to each glass manufacturer. The compositions of the melts were also specific to each manufacturer. Those optimized for high color purity and contrast were doped with Neodymium, while those for monochrome CRTs were tinted to differing levels, depending on the formulation used and had transmittances of 42% or 30%. Purity is ensuring that the correct colors are activated (for example, ensuring that red is displayed uniformly across the screen) while convergence ensures that images are not distorted. Convergence may be modified using a cross hatch pattern.
CRT glass used to be made by dedicated companies such as AGC Inc., O-I Glass, Samsung Corning Precision Materials, Corning Inc., and Nippon Electric Glass; others such as Videocon, Sony for the US market and Thomson made their own glass.
The funnel and the neck are made of leaded potash-soda glass or lead silicate glass The amount of x-rays emitted by a CRT can also lowered by reducing the brightness of the image. while also shielding heavily against x-rays, although some funnels may also contain barium. Another glass formulation uses 2–3% of lead on the screen.
Monochrome CRTs may have a tinted barium-lead glass formulation in both the screen and funnel, with a potash-soda lead glass in the neck; the potash-soda and barium-lead formulations have different thermal expansion coefficients. The glass used in the neck must be an excellent electrical insulator to contain the voltages used in the electron optics of the electron gun, such as focusing lenses. The lead in the glass causes it to brown (darken) with use due to x-rays, usually the CRT cathode wears out due to cathode poisoning before browning becomes apparent. The glass formulation determines the highest possible anode voltage and hence the maximum possible CRT screen size. For color, maximum voltages are often 24–32 kV, while for monochrome it is usually 21 or 24.5 kV, limiting the size of monochrome CRTs to 21 inches, or ~1 kV per inch. The voltage needed depends on the size and type of CRT. Since the formulations are different, they must be compatible with one another, having similar thermal expansion coefficients. or be ground to prevent reflections. CRTs may also have an anti-static coating. and the screen may contain 12% of barium oxide, and 12% of strontium oxide. Before this, CRTs used lead on the faceplate. Early CRTs did not have a dedicated anode cap connection; the funnel was the anode connection, so it was live during operation.
The funnel is coated on the inside and outside with a conductive coating, making the funnel a capacitor, helping stabilize and filter the anode voltage of the CRT, and significantly reducing the amount of time needed to turn on a CRT. The stability provided by the coating solved problems inherent to early power supply designs, as they used vacuum tubes. Because the funnel is used as a capacitor, the glass used in the funnel must be an excellent electrical insulator (dielectric). The inner coating has a positive voltage (the anode voltage that can be several kV) while the outer coating is connected to ground. CRTs powered by more modern power supplies do not need to be connected to ground, due to the more robust design of modern power supplies. The value of the capacitor formed by the funnel is 5–10 nF, although at the voltage the anode is normally supplied with. The capacitor formed by the funnel can also suffer from dielectric absorption, similarly to other types of capacitors. before handling to prevent injury.
The depth of a CRT is related to its screen size. Usual deflection angles were 90° for computer monitor CRTs and small CRTs and 110° which was the standard in larger TV CRTs, with 120 or 125° being used in slim CRTs made since 2001–2005 in an attempt to compete with LCD TVs. Over time, deflection angles increased as they became practical, from 50° in 1938 to 110° in 1959,
File:Cinescopio per televisore a schermo rettangolare, 17 pollici, deflessione 110°, bianco e nero - Museo scienza tecnologia Milano 10081 dia.jpg|A monochrome CRT with 110° deflection
File:Cinescopio per televisore a schermo rettangolare, 13 pollici, deflessione 90°, bianco e nero - Museo scienza tecnologia Milano 10082 dia.jpg|A monochrome CRT with 90° deflection
===Size and weight===
The size of a CRT can be measured by the screen's entire area (or face diagonal) or alternatively by only its viewable area (or diagonal) that is coated by phosphor and surrounded by black edges.
While the viewable area may be rectangular, the edges of the CRT may have a curvature (e.g. black stripe CRTs, first made by Toshiba in 1972) or the viewable area may follow the curvature of the edges of the CRT (with or without black edges or curved edges).
Most of the weight of a CRT comes from the thick glass screen, which comprises 65% of the total weight of a CRT and limits its practical size (see ). The funnel and neck glass comprise the remaining 30% and 5% respectively. The glass in the funnel can vary in thickness, to join the thin neck with the thick screen.
===Anode===
The outer conductive coating is connected to ground while the inner conductive coating is connected using the anode button/cap through a series of capacitors and diodes (a Cockcroft–Walton generator) to the high voltage flyback transformer; the inner coating is the anode of the CRT, which, together with an electrode in the electron gun, is also known as the final anode. The inner coating is connected to the electrode using springs. The electrode forms part of a bipotential lens. The capacitors and diodes serve as a voltage multiplier for the current delivered by the flyback.
For the inner funnel coating, monochrome CRTs use aluminum while color CRTs use aquadag; use aquadag. Aquadag is an electrically conductive graphite-based paint. In color CRTs, the aquadag is sprayed onto the interior of the funnel The connection is insulated by a silicone suction cup, possibly also using silicone grease to prevent corona discharge.
The anode button must be specially shaped to establish a hermetic seal between the button and funnel. X-rays may leak through the anode button, although that may not be the case in newer CRTs starting from the late 1970s to early 1980s, thanks to a new button and clip design. The button may consist of a set of 3 nested cups, with the outermost cup being made of a Nickel–Chromium–Iron alloy containing 40–49% of Nickel and 3–6% of Chromium to make the button easy to fuse to the funnel glass, with a first inner cup made of thick inexpensive iron to shield against x-rays, and with the second innermost cup also being made of iron or any other electrically conductive metal to connect to the clip. The cups must be heat resistant enough and have similar thermal expansion coefficients similar to that of the funnel glass to withstand being fused to the funnel glass. The inner side of the button is connected to the inner conductive coating of the CRT.
The flyback transformer is also known as an IHVT (Integrated High Voltage Transformer) if it includes a voltage multiplier. The flyback uses a ceramic or powdered iron core to enable efficient operation at high frequencies. The flyback contains one primary and many secondary windings that provide several different voltages. The main secondary winding supplies the voltage multiplier with voltage pulses to ultimately supply the CRT with the high anode voltage it uses, while the remaining windings supply the CRT's filament voltage, keying pulses, focus voltage and voltages derived from the scan raster. When the transformer is turned off, the flyback's magnetic field quickly collapses which induces high voltage in its windings. The speed at which the magnetic field collapses determines the voltage that is induced, so the voltage increases alongside its speed. A capacitor (Retrace Timing Capacitor) or series of capacitors (to provide redundancy) is used to slow the collapse of the magnetic field.
The design of the high voltage power supply in a product using a CRT has an influence in the amount of x-rays emitted by the CRT. The amount of emitted x-rays increases with both higher voltages and currents. If the product such as a TV set uses an unregulated high voltage power supply, meaning that anode and focus voltage go down with increasing electron current when displaying a bright image, the amount of emitted x-rays is as its highest when the CRT is displaying a moderately bright images, since when displaying dark or bright images, the higher anode voltage counteracts the lower electron beam current and vice versa respectively. The high voltage regulator and rectifier vacuum tubes in some old CRT TV sets may also emit x-rays.
===Electron gun===
The electron gun emits the electrons that ultimately hit the phosphors on the screen of the CRT. The electron gun contains a heater, which heats a cathode, which generates electrons that, using grids, are focused and ultimately accelerated into the screen of the CRT. The acceleration occurs in conjunction with the inner aluminum or aquadag coating of the CRT. The electron gun is positioned so that it aims at the center of the screen. The electron gun is made separately and then placed inside the neck through a process called "winding", or sealing. The electron gun has a glass wafer that is fused to the neck of the CRT. The connections to the electron gun penetrate the glass wafer. Once the electron gun is inside the neck, its metal parts (grids) are arced between each other using high voltage to smooth any rough edges in a process called spot knocking, to prevent the rough edges in the grids from generating secondary electrons.
====Construction and method of operation====
The electron gun has an indirectly heated hot cathode that is heated by a tungsten filament heating element; the heater may draw 0.5–2 A of current depending on the CRT. The voltage applied to the heater can affect the life of the CRT. Heating the cathode energizes the electrons in it, aiding electron emission, while at the same time current is supplied to the cathode; typically anywhere from 140 mA at 1.5 V to 600 mA at 6.3 V. The cathode creates an electron cloud (emits electrons) whose electrons are extracted, accelerated and focused into an electron beam.
There are several short circuits that can occur in a CRT electron gun. One is a heater-to-cathode short, that causes the cathode to permanently emit electrons which may cause an image with a bright red, green or blue tint with retrace lines, depending on the cathode (s) affected. Alternatively, the cathode may short to the control grid, possibly causing similar effects, or, the control grid and screen grid (G2) can short causing a very dark image or no image at all. The cathode may be surrounded by a shield to prevent sputtering.
The cathode is a layer of barium oxide which is coated on a piece of nickel for electrical and mechanical support. In color CRTs with red, green and blue cathodes, one or more cathodes may be affected independently of the others, causing total or partial loss of one or more colors. In color CRTs, since there are three cathodes, one for red, green and blue, a single or more poisoned cathode may cause the partial or complete loss of one or more colors, tinting the image.
The amount of electrons generated by the cathodes is related to their surface area. A cathode with more surface area creates more electrons, in a larger electron cloud, which makes focusing the electron cloud into an electron beam more difficult. is applied to the first (control) grid (G1) to converge the electrons from the hot cathode, creating an electron beam. G1 in practice is a Wehnelt cylinder. The brightness of the screen is not controlled by varying the anode voltage nor the electron beam current (they are never varied) despite them having an influence on image brightness, rather image brightness is controlled by varying the difference in voltage between the cathode and the G1 control grid. The second (screen) grid of the gun (G2) then accelerates the electrons towards the screen using several hundred DC volts. Then a third grid (G3) electrostatically focuses the electron beam before it is deflected and later accelerated by the anode voltage onto the screen. Electrostatic focusing of the electron beam may be accomplished using an einzel lens energized at up to 600 volts. Before electrostatic focusing, focusing the electron beam required a large, heavy and complex mechanical focusing system placed outside the electron gun. electrode, together with an electrode at the final anode voltage of the CRT, may be used for focusing instead. Such an arrangement is called a bipotential lens, which also offers higher performance than an einzel lens, or, focusing may be accomplished using a magnetic focusing coil together with a high anode voltage of dozens of kilovolts. However, magnetic focusing is expensive to implement, so it is rarely used in practice. Some CRTs may use two grids and lenses to focus the electron beam.
There is a voltage called cutoff voltage which is the voltage that creates black on the screen since it causes the image on the screen created by the electron beam to disappear, the voltage is applied to G1. In a color CRT with three guns, the guns have different cutoff voltages. Many CRTs share grid G1 and G2 across all three guns, increasing image brightness and simplifying adjustment since on such CRTs there is a single cutoff voltage for all three guns (since G1 is shared across all guns). Alternatively, the amplifier may be driven by a video processor that also introduces an OSD (On Screen Display) into the video stream that is fed into the amplifier, using a fast blanking signal. TV sets and computer monitors that incorporate CRTs need a DC restoration circuit to provide a video signal to the CRT with a DC component, restoring the original brightness of different parts of the image.
The electron beam may be affected by the Earth's magnetic field, causing it to normally enter the focusing lens off-center; this can be corrected using astigmation controls. Astigmation controls are both magnetic and electronic (dynamic); magnetic does most of the work while electronic is used for fine adjustments. One of the ends of the electron gun has a glass disk, the edges of which are fused with the edge of the neck of the CRT, possibly using frit; the metal leads that connect the electron gun to the outside pass through the disk.
Some electron guns have a quadrupole lens with dynamic focus to alter the shape and adjust the focus of the electron beam, varying the focus voltage depending on the position of the electron beam to maintain image sharpness across the entire screen, specially at the corners. They may also have a bleeder resistor to derive voltages for the grids from the final anode voltage.
After the CRTs were manufactured, they were aged to allow cathode emission to stabilize.
The electron guns in color CRTs are driven by a video amplifier which takes a signal per color channel and amplifies it to 40–170 V per channel, to be fed into the electron gun's cathodes; The amplifier's capabilities limit the resolution, refresh rate and contrast ratio of the CRT, as the amplifier needs to provide high bandwidth and voltage variations at the same time; higher resolutions and refresh rates need higher bandwidths (speed at which voltage can be varied and thus switching between black and white) and higher contrast ratios need higher voltage variations or amplitude for lower black and higher white levels. 30 MHz of bandwidth can usually provide 720p or 1080i resolution, while 20 MHz usually provides around 600 (horizontal, from top to bottom) lines of resolution, for example.
===Deflection===
There are two types of deflection: magnetic and electrostatic. Magnetic is usually used in TVs and monitors as it allows for higher deflection angles (and hence shallower CRTs) and deflection power (which allows for higher electron beam current and hence brighter images) while avoiding the need for high voltages for deflection of up to 2 kV,
====Magnetic deflection====
Those that use magnetic deflection may use a yoke that has two pairs of deflection coils; one pair for vertical, and another for horizontal deflection. The yoke can be bonded (be integral) or removable. Those that were bonded used glue or a plastic to bond the yoke to the area between the neck and the funnel of the CRT while those with removable yokes are clamped. and monochrome CRTs. The yoke may be connected using a connector, the order in which the deflection coils of the yoke are connected determines the orientation of the image displayed by the CRT. A CRT needs two deflection circuits: a horizontal and a vertical circuit, which are similar except that the horizontal circuit runs at a much higher frequency (a Horizontal scan rate) of 15–240 kHz depending on the refresh rate of the CRT and the number of horizontal lines to be drawn (the vertical resolution of the CRT). The higher frequency makes it more susceptible to interference, so an automatic frequency control (AFC) circuit may be used to lock the phase of the horizontal deflection signal to that of a sync signal, to prevent the image from becoming distorted diagonally. The vertical frequency varies according to the refresh rate of the CRT. So a CRT with a 60 Hz refresh rate has a vertical deflection circuit running at 60 Hz. The horizontal and vertical deflection signals may be generated using two circuits that work differently; the horizontal deflection signal may be generated using a voltage controlled oscillator (VCO) while the vertical signal may be generated using a triggered relaxation oscillator. In many TVs, the frequencies at which the deflection coils run is in part determined by the inductance value of the coils. for a given screen size, but at the cost of more deflection power and lower optical performance.
Higher deflection power means more current is sent to the deflection coils to bend the electron beam at a higher angle, The deflection power is measured in mA per inch. The horizontal deflection coils may also be driven in part by the horizontal output stage of a TV set. The stage contains a capacitor that is in series with the horizontal deflection coils that performs several functions, among them are: shaping the sawtooth deflection signal to match the curvature of the CRT and centering the image by preventing a DC bias from developing on the coil. At the beginning of retrace, the magnetic field of the coil collapses, causing the electron beam to return to the center of the screen, while at the same time the coil returns energy into capacitors, the energy of which is then used to force the electron beam to go to the left of the screen. The voltage on the horizontal deflection coils is negative when the electron beam is on the left side of the screen and positive when the electron beam is on the right side of the screen. The energy required for deflection is dependent on the energy of the electrons. Higher energy (voltage and/or current) electron beams need more energy to be deflected,
===Burn-in===
Burn-in is when images are physically "burned" into the screen of the CRT; this occurs due to degradation of the phosphors due to prolonged electron bombardment of the phosphors, and happens when a fixed image or logo is left for too long on the screen, causing it to appear as a "ghost" image or, in severe cases, also when the CRT is off. To counter this, screensavers were used in computers to minimize burn-in. Burn-in is not exclusive to CRTs, as it also happens to plasma displays and OLED displays.
===Evacuation===
The CRT's partial vacuum of to or less is evacuated or exhausted in a ~375–475 °C oven in a process called baking or bake-out. The evacuation process also outgasses any materials inside the CRT, while decomposing others such as the polyvinyl alcohol used to apply the phosphors. The heating and cooling are done gradually to avoid inducing stress, stiffening and possibly cracking the glass; the oven heats the gases inside the CRT, increasing the speed of the gas molecules which increases the chances of them getting drawn out by the vacuum pump. The temperature of the CRT is kept to below that of the oven, and the oven starts to cool just after the CRT reaches 400 °C, or, the CRT was kept at a temperature higher than 400 °C for up to 15–55 minutes. The CRT was heated during or after evacuation, and the heat may have been used simultaneously to melt the frit in the CRT, joining the screen and funnel. The pump used is a turbomolecular pump or a diffusion pump. Formerly mercury vacuum pumps were also used. After baking, the CRT is disconnected ("sealed or tipped off") from the vacuum pump. The getter is then fired using an RF (induction) coil. The getter is usually in the funnel or in the neck of the CRT. The getter material which is often barium-based, catches any remaining gas particles as it evaporates due to heating induced by the RF coil (that may be combined with exothermic heating within the material); the vapor fills the CRT, trapping any gas molecules that it encounters and condenses on the inside of the CRT forming a layer that contains trapped gas molecules. Hydrogen may be present in the material to help distribute the barium vapor. The material is heated to temperatures above 1000 °C, causing it to evaporate. Partial loss of vacuum in a CRT can result in a hazy image, blue glowing in the neck of the CRT, flashovers, loss of cathode emission or focusing problems. and the last in Europe, RACS, which was located in France, closed in 2013.
===Reactivation===
Also known as rejuvenation, the goal is to temporarily restore the brightness of a worn CRT. This is often done by carefully increasing the voltage on the cathode heater and the current and voltage on the control grids of the electron gun manually. Some rejuvenators can also fix heater-to-cathode shorts by running a capacitive discharge through the short. and some black and white CRT phosphors also contained beryllium in the form of Zinc beryllium silicate, The phosphors adhere to the screen because of Van der Waals and electrostatic forces. Phosphors composed of smaller particles adhere more strongly to the screen. The phosphors together with the carbon used to prevent light bleeding (in color CRTs) can be easily removed by scratching.
Several dozen types of phosphors were available for CRTs. Phosphors were classified according to color, persistence, luminance rise and fall curves, color depending on anode voltage (for phosphors used in penetration CRTs), Intended use, chemical composition, safety, sensitivity to burn-in, and secondary emission properties. Examples of rare earth phosphors are yttrium oxide for red and yttrium silicide for blue in beam index tubes, while examples of earlier phosphors are copper cadmium sulfide for red,
SMPTE-C phosphors have properties defined by the SMPTE-C standard, which defines a color space of the same name. The standard prioritizes accurate color reproduction, which was made difficult by the different phosphors and color spaces used in the NTSC and PAL color systems. PAL TV sets have subjectively better color reproduction due to the use of saturated green phosphors, which have relatively long decay times that are tolerated in PAL since there is more time in PAL for phosphors to decay, due to its lower framerate. SMPTE-C phosphors were used in professional video monitors.
The phosphor coating on monochrome and color CRTs may have an aluminum coating on its rear side used to reflect light forward, provide protection against ions to prevent ion burn by negative ions on the phosphor, manage heat generated by electrons colliding against the phosphor, prevent static build up that could repel electrons from the screen, form part of the anode and collect the secondary electrons generated by the phosphors in the screen after being hit by the electron beam, providing the electrons with a return path. This is known as filming. The lacquer contains solvents that are later evaporated; the lacquer may be chemically roughened to cause an aluminum coating with holes to be created to allow the solvents to escape. For visual observation of brief transient events, a long persistence phosphor may be desirable. For events which are fast and repetitive, or high frequency, a short-persistence phosphor is generally preferable. The phosphor persistence must be low enough to avoid smearing or ghosting artifacts at high refresh rates. Some blooming is unavoidable, which can be seen as bright areas of an image that expand, distorting or pushing aside surrounding darker areas of the same image. Blooming occurs because bright areas have a higher electron beam current from the electron gun, making the beam wider and harder to focus. Poor voltage regulation causes focus and anode voltage to go down with increasing electron beam current. Thermal expansion causes the shadow mask to expand by around 100 microns.
During normal operation, the shadow mask is heated to around 80–90 °C. Bright areas of images heat the shadow mask more than dark areas, leading to uneven heating of the shadow mask and warping (blooming) due to thermal expansion caused by heating by increased electron beam current. The shadow mask is usually made of steel but it can be made of Invar Coatings that dissipate heat may be applied on the shadow mask to limit blooming in a process called blackening.
Bimetal springs may be used in CRTs used in TVs to compensate for warping that occurs as the electron beam heats the shadow mask, causing thermal expansion. or a rail or frame that is fused to the funnel or the screen glass respectively, 80–85%
====High voltage====
Image brightness is related to the anode voltage and to the CRTs size, so higher voltages are needed for both larger screens and higher image brightness. Image brightness is also controlled by the current of the electron beam. since a CRT's exterior is exposed to the full atmospheric pressure, which for instance totals on a 27-inch (400 in2) screen. For example, the large 43-inch Sony PVM-4300 weighs , much heavier than 32-inch CRTs (up to ) and 19-inch CRTs (up to ). Much lighter flat panel TVs are only ~ for 32-inch and for 19-inch.
Size is also limited by anode voltage, as it would require a higher dielectric strength to prevent arcing and the electrical losses and ozone generation it causes, without sacrificing image brightness.
Shadow masks also become more difficult to make with increasing resolution and size. Higher deflection angles in color CRTs directly affect convergence at the corners of the screen which requires additional compensation circuitry to handle electron beam power and shape, leading to higher costs and power consumption. Higher deflection angles allow a CRT of a given size to be slimmer, however they also impose more stress on the CRT envelope, specially on the panel, the seal between the panel and funnel and on the funnel. The funnel needs to be long enough to minimize stress, as a longer funnel can be better shaped to have lower stress.
==Comparison with other technologies==
LCD advantages over CRT: Lower bulk, power consumption and heat generation, higher refresh rates (up to 360 Hz)
CRT advantages over LCD: Better color reproduction, no motion blur, multisyncing available in many monitors, no input lag except for computer monitors.
On CRTs, refresh rate depends on resolution, both of which are ultimately limited by the maximum horizontal scanning frequency of the CRT. Motion blur also depends on the decay time of the phosphors. Phosphors that decay too slowly for a given refresh rate may cause smearing or motion blur on the image. In practice, CRTs are limited to a refresh rate of 160 Hz. LCDs that can compete with OLED (Dual Layer, and mini-LED LCDs) are not available in high refresh rates, although quantum dot LCDs (QLEDs) are available in high refresh rates (up to 144 Hz) and are competitive in color reproduction with OLEDs.
CRT monitors can still outperform LCD and OLED monitors in input lag, as there is no signal processing between the CRT and the display connector of the monitor, since CRT monitors often use VGA which provides an analog signal that can be fed to a CRT directly. Video cards designed for use with CRTs may have a RAMDAC to generate the analog signals needed by the CRT. Due to these reasons, CRTs are often preferred for playing video games made in the early 2000s and prior in spite of their bulk, weight and heat generation, with some pieces of technology requiring a CRT to function due to not being built with the functionality of modern displays in mind.
CRTs tend to be more durable than their flat panel counterparts, or sometimes underscan.
Picture tube CRTs have overscan, meaning the actual edges of the image are not shown; this is deliberate to allow for adjustment variations between CRT TVs, preventing the ragged edges (due to blooming) of the image from being shown on screen. The shadow mask may have grooves that reflect away the electrons that do not hit the screen due to overscan. CRTs are also sometimes called Braun tubes.
===Monochrome CRTs===
If the CRT is a black and white (B&W or monochrome) CRT, there is a single electron gun in the neck and the funnel is coated on the inside with aluminum that has been applied by evaporation; the aluminum is evaporated in a vacuum and allowed to condense on the inside of the CRT. In aluminized monochrome CRTs, Aquadag is used on the outside. There is a single aluminum coating covering the funnel and the screen.
Monochrome CRTs may use ring magnets to adjust the centering of the electron beam and magnets around the deflection yoke to adjust the geometry of the image.
When a monochrome CRT is shut off, the screen itself retracts to a small, white dot in the center, along with the phosphors shutting down, shot by the electron gun; it sometimes takes a while for it to go away.
File:Osziroehre.jpg|Older monochrome CRT without aluminum, only aquadag
File:Monochrome CRT electron gun close up.jpg|The electron gun of a monochrome CRT
===Color CRTs===
Color CRTs use three different phosphors which emit red, green, and blue light respectively. They are packed together in stripes (as in aperture grille designs) or clusters called "triads" (as in shadow mask CRTs).
Color CRTs have three electron guns, one for each primary color, (red, green and blue) arranged either in a straight line (in-line) or in an equilateral triangular configuration (the guns are usually constructed as a single unit). The triangular configuration is often called delta-gun, based on its relation to the shape of the Greek letter delta (Δ). The arrangement of the phosphors is the same as that of the electron guns. A grille or mask absorbs the electrons that would otherwise hit the wrong phosphor.
A shadow mask tube uses a metal plate with tiny holes, typically in a delta configuration, placed so that the electron beam only illuminates the correct phosphors on the face of the tube; so that the electrons that strike the inside of any hole will be reflected back, if they are not absorbed (e.g. due to local charge accumulation), instead of bouncing through the hole to strike a random (wrong) spot on the screen. Another type of color CRT (Trinitron) uses an aperture grille of tensioned vertical wires to achieve the same result.
The three electron guns are in the neck (except for Trinitrons) and the red, green and blue phosphors on the screen may be separated by a black grid or matrix (called black stripe by Toshiba). The aluminum coating protects the phosphor from ions, absorbs secondary electrons, providing them with a return path, preventing them from electrostatically charging the screen which would then repel electrons and reduce image brightness, reflects the light from the phosphors forwards and helps manage heat. It also serves as the anode of the CRT together with the inner aquadag coating. The inner coating is electrically connected to an electrode of the electron gun using springs, forming the final anode.
====Shadow mask====
The shadow mask absorbs or reflects electrons that would otherwise strike the wrong phosphor dots,
Shadow masks were replaced in TVs by slot masks in the 1970s, since slot masks let more electrons through, increasing image brightness. Shadow masks may be connected electrically to the anode of the CRT. Trinitron used a single electron gun with three cathodes instead of three complete guns. CRT PC monitors usually use shadow masks, except for Sony's Trinitron, Mitsubishi's Diamondtron and NEC's Cromaclear; Trinitron and Diamondtron use aperture grilles while Cromaclear uses a slot mask. Some shadow mask CRTs have color phosphors that are smaller in diameter than the electron beams used to light them, with the intention being to cover the entire phosphor, increasing image brightness. Shadow masks may be pressed into a curved shape.
====Screen manufacture====
Early color CRTs did not have a black matrix, which was introduced by Zenith in 1969, and Panasonic in 1970.
The phosphors are applied using photolithography. The inner side of the screen is coated with phosphor particles suspended in PVA photoresist slurry, which is then dried using infrared light, exposed, and developed. The exposure is done using a "lighthouse" that uses an ultraviolet light source with a corrector lens to allow the CRT to achieve color purity. Removable shadow masks with spring-loaded clips are used as photomasks. The process is repeated with all colors. Usually the green phosphor is the first to be applied. After phosphor application, the screen is baked to eliminate any organic chemicals (such as the PVA that was used to deposit the phosphor) that may remain on the screen. Alternatively, the phosphors may be applied in a vacuum chamber by evaporating them and allowing them to condense on the screen, creating a very uniform coating. Poor exposure due to insufficient light leads to poor phosphor adhesion to the screen, which limits the maximum resolution of a CRT, as the smaller phosphor dots required for higher resolutions cannot receive as much light due to their smaller size.
After the screen is coated with phosphor and aluminum and the shadow mask installed onto it the screen is bonded to the funnel using a glass frit that may contain 65–88% of lead oxide by weight. The lead oxide is necessary for the glass frit to have a low melting temperature. Boron oxide (III) may also present to stabilize the frit, with alumina powder as filler powder to control the thermal expansion of the frit. The CRT is then baked in an oven in what is called a Lehr bake, to cure the frit, sealing the funnel and screen together. The frit contains a large quantity of lead, causing color CRTs to contain more lead than their monochrome counterparts. Monochrome CRTs on the other hand do not require frit; the funnel can be fused directly to the glass The Lehr bake consists of several successive steps that heat and then cool the CRT gradually until it reaches a temperature of 435–475 °C After the Lehr bake, the CRT is flushed with air or nitrogen to remove contaminants, the electron gun is inserted and sealed into the neck of the CRT, and a vacuum is formed on the CRT. More specifically, the convergence at the center of the screen (with no deflection field applied by the yoke) is called static convergence, and the convergence over the rest of the screen area (specially at the edges and corners) is called dynamic convergence. These movable weak permanent magnets are usually mounted on the back end of the deflection yoke assembly and are set at the factory to compensate for any static purity and convergence errors that are intrinsic to the unadjusted tube. Typically there are two or three pairs of two magnets in the form of rings made of plastic impregnated with a magnetic material, with their magnetic fields parallel to the planes of the magnets, which are perpendicular to the electron gun axes. Often, one pair of rings has 2 poles, another has 4, and the remaining ring has 6 poles. Each pair of magnetic rings forms a single effective magnet whose field vector can be fully and freely adjusted (in both direction and magnitude). By rotating a pair of magnets relative to each other, their relative field alignment can be varied, adjusting the effective field strength of the pair. (As they rotate relative to each other, each magnet's field can be considered to have two opposing components at right angles, and these four components [two each for two magnets] form two pairs, one pair reinforcing each other and the other pair opposing and canceling each other. Rotating away from alignment, the magnets' mutually reinforcing field components decrease as they are traded for increasing opposed, mutually cancelling components.) By rotating a pair of magnets together, preserving the relative angle between them, the direction of their collective magnetic field can be varied. Overall, adjusting all of the convergence/purity magnets allows a finely tuned slight electron beam deflection or lateral offset to be applied, which compensates for minor static convergence and purity errors intrinsic to the uncalibrated tube. Once set, these magnets are usually glued in place, but normally they can be freed and readjusted in the field (e.g. by a TV repair shop) if necessary.
On some CRTs, additional fixed adjustable magnets are added for dynamic convergence or dynamic purity at specific points on the screen, typically near the corners or edges. Further adjustment of dynamic convergence and purity typically cannot be done passively, but requires active compensation circuits, one to correct convergence horizontally and another to correct it vertically. In this case the deflection yoke contains convergence coils, a set of two per color, wound on the same core, to which the convergence signals are applied. That means 6 convergence coils in groups of 3, with 2 coils per group, with one coil for horizontal convergence correction and another for vertical convergence correction, with each group sharing a core. The groups are separated 120° from one another. Dynamic convergence is necessary because the front of the CRT and the shadow mask are not spherical, compensating for electron beam defocusing and astigmatism. The fact that the CRT screen is not spherical leads to geometry problems which may be corrected using a circuit. The signals used for convergence are parabolic waveforms derived from three signals coming from a vertical output circuit. The parabolic signal is fed into the convergence coils, while the other two are sawtooth signals that, when mixed with the parabolic signals, create the necessary signal for convergence. A resistor and diode are used to lock the convergence signal to the center of the screen to prevent it from being affected by the static convergence. The horizontal and vertical convergence circuits are similar. Each circuit has two resonators, one usually tuned to 15,625 Hz and the other to 31,250 Hz, which set the frequency of the signal sent to the convergence coils. Dynamic convergence may be accomplished using electrostatic quadrupole fields in the electron gun. Dynamic convergence means that the electron beam does not travel in a perfectly straight line between the deflection coils and the screen, since the convergence coils cause it to become curved to conform to the screen.
The convergence signal may instead be a sawtooth signal with a slight sine wave appearance, the sine wave part is created using a capacitor in series with each deflection coil. In this case, the convergence signal is used to drive the deflection coils. The sine wave part of the signal causes the electron beam to move more slowly near the edges of the screen. The capacitors used to create the convergence signal are known as the s-capacitors. This type of convergence is necessary due to the high deflection angles and flat screens of many CRT computer monitors. The value of the s-capacitors must be chosen based on the scan rate of the CRT, so multi-syncing monitors must have different sets of s-capacitors, one for each refresh rate. 90° deflection angle CRTs may use "self-convergence" without dynamic convergence, which together with the in-line triad arrangement, eliminates the need for separate convergence coils and related circuitry, reducing costs. complexity and CRT depth by 10 millimeters. Self-convergence works by means of "nonuniform" magnetic fields. Dynamic convergence is necessary in 110° deflection angle CRTs, and quadrupole windings on the deflection yoke at a certain frequency may also be used for dynamic convergence.
Dynamic color convergence and purity are one of the main reasons why until late in their history, CRTs were long-necked (deep) and had biaxially curved faces; these geometric design characteristics are necessary for intrinsic passive dynamic color convergence and purity. Only starting around the 1990s did sophisticated active dynamic convergence compensation circuits become available that made short-necked and flat-faced CRTs workable. These active compensation circuits use the deflection yoke to finely adjust beam deflection according to the beam target location. The same techniques (and major circuit components) also make possible the adjustment of display image rotation, skew, and other complex raster geometry parameters through electronics under user control. Other CRTs may instead use magnets that are pushed in and out instead of rings. The magnetic shield and shadow mask may be permanently magnetized by the earth's magnetic field, adversely affecting color purity when the CRT is moved. This problem is solved with a built-in degaussing coil, found in many TVs and computer monitors. Degaussing may be automatic, occurring whenever the CRT is turned on.
Color CRT displays in TV sets and computer monitors often have a built-in degaussing (demagnetizing) coil mounted around the perimeter of the CRT face. Upon power-up of the CRT display, the degaussing circuit produces a brief, alternating current through the coil which fades to zero over a few seconds, producing a decaying alternating magnetic field from the coil. This degaussing field is strong enough to remove shadow mask magnetization in most cases, maintaining color purity. In unusual cases of strong magnetization where the internal degaussing field is not sufficient, the shadow mask may be degaussed externally with a stronger portable degausser or demagnetizer. However, an excessively strong magnetic field, whether alternating or constant, may mechanically deform (bend) the shadow mask, causing a permanent color distortion on the display which looks very similar to a magnetization effect.
====Resolution====
Dot pitch defines the maximum resolution of the display, assuming delta-gun CRTs. In these, as the scanned resolution approaches the dot pitch resolution, moiré appears, as the detail being displayed is finer than what the shadow mask can render. Aperture grille monitors do not suffer from vertical moiré, however, because their phosphor stripes have no vertical detail. In smaller CRTs, these strips maintain position by themselves, but larger aperture-grille CRTs require one or two crosswise (horizontal) support strips; one for smaller CRTs, and two for larger ones. The support wires block electrons, causing the wires to be visible. In aperture grille CRTs, dot pitch is replaced by stripe pitch. Hitachi developed the Enhanced Dot Pitch (EDP) shadow mask, which uses oval holes instead of circular ones, with respective oval phosphor dots. and are similar in construction to other monochrome CRTs. Larger projection CRTs in general lasted longer, and were able to provide higher brightness levels and resolution, but were also more expensive. Projection CRTs have an unusually high anode voltage for their size (such as 27 or 25 kV for a 5 or 7-inch projection CRT respectively), and a specially made tungsten/barium cathode (instead of the pure barium oxide normally used) that consists of barium atoms embedded in 20% porous tungsten or barium and calcium aluminates or of barium, calcium and aluminum oxides coated on porous tungsten; the barium diffuses through the tungsten to emit electrons. The special cathode can deliver 2 mA of current instead of the 0.3mA of normal cathodes, or colorless glycol may be used inside a container which may be colored (forming a lens known as a c-element). Colored lenses or glycol are used for improving color reproduction at the cost of brightness, and are only used on red and green CRTs. Each CRT has its own glycol, which has access to an air bubble to allow the glycol to shrink and expand as it cools and warms. Projector CRTs may have adjustment rings just like color CRTs to adjust astigmatism, which is flaring of the electron beam (stray light similar to shadows). They have three adjustment rings; one with two poles, one with four poles, and another with 6 poles. When correctly adjusted, the projector can display perfectly round dots without flaring. The screens used in projection CRTs were more transparent than usual, with 90% transmittance.
Projector CRTs were available with electrostatic and electromagnetic focusing, the latter being more expensive. Electrostatic focusing used electronics to focus the electron beam, together with focusing magnets around the neck of the CRT for fine focusing adjustments. This type of focusing degraded over time. Electromagnetic focusing was introduced in the early 1990s and included an electromagnetic focusing coil in addition to the already existing focusing magnets. Electromagnetic focusing was much more stable over the lifetime of the CRT, retaining 95% of its sharpness by the end of life of the CRT.
===Beam-index tube===
Beam-index tubes, also known as Uniray, Apple CRT or Indextron, was an attempt in the 1950s by Philco to create a color CRT without a shadow mask, eliminating convergence and purity problems, and allowing for shallower CRTs with higher deflection angles. It also required a lower voltage power supply for the final anode since it did not use a shadow mask, which normally blocks around 80% of the electrons generated by the electron gun. The lack of a shadow mask also made it immune to the earth's magnetic field while also making degaussing unnecessary and increasing image brightness. It was constructed similarly to a monochrome CRT, with an aquadag outer coating, an aluminum inner coating, and a single electron gun but with a screen with an alternating pattern of red, green, blue and UV (index) phosphor stripes (similarly to a Trinitron) with a side mounted photomultiplier tube It was revived by Sony in the 1980s as the Indextron but its adoption was limited, at least in part due to the development of LCD displays. Beam-index CRTs also suffered from poor contrast ratios of only around 50:1 since some light emission by the phosphors was required at all times by the photodiodes to track the electron beam. It allowed for single CRT color CRT projectors due to a lack of shadow mask; normally CRT projectors use three CRTs, one for each color, since a lot of heat is generated due to the high anode voltage and beam current, making a shadow mask impractical and inefficient since it would warp under the heat produced (shadow masks absorb most of the electron beam, and, hence, most of the energy carried by the relativistic electrons); the three CRTs meant that an involved calibration and adjustment procedure had to be carried out during installation of the projector, and moving the projector would require it to be recalibrated. A single CRT meant the need for calibration was eliminated, but brightness was decreased since the CRT screen had to be used for three colors instead of each color having its own CRT screen. LG's Flatron technology is based on this technology developed by Zenith, now a subsidiary of LG.
Flat CRTs have a number of challenges, like deflection. Vertical deflection boosters are required to increase the amount of current that is sent to the vertical deflection coils to compensate for the reduced curvature. The TV80 used electrostatic deflection while the Watchman used magnetic deflection with a phosphor screen that was curved inwards. Similar CRTs were used in video door bells.
File:SONY 03JM 2.5" Monochrome Flat Watchman CRT side.jpg|The side of a Sony Watchman monochrome CRT. One of the pairs of deflection coils is easily noticeable.
===Radar CRTs===
Radar CRTs such as the 7JP4 had a circular screen and scanned the beam from the center outwards. The deflection yoke rotated, causing the beam to rotate in a circular fashion. The screen often had two colors, often a bright short persistence color that only appeared as the beam scanned the display and a long persistence phosphor afterglow. When the beam strikes the phosphor, the phosphor brightly illuminates, and when the beam leaves, the dimmer long persistence afterglow would remain lit where the beam struck the phosphor, alongside the radar targets that were "written" by the beam, until the beam re-struck the phosphor.
===Oscilloscope CRTs===
In oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with TV and other large CRTs. The beam is deflected horizontally by applying an electric field between a pair of plates to its left and right, and vertically by applying an electric field to plates above and below. TVs use magnetic rather than electrostatic deflection because the deflection plates obstruct the beam when the deflection angle is as large as is required for tubes that are relatively short for their size. Some Oscilloscope CRTs incorporate post deflection anodes (PDAs) that are spiral-shaped to ensure even anode potential across the CRT and operate at up to 15 kV. In PDA CRTs the electron beam is deflected before it is accelerated, improving sensitivity and legibility, specially when analyzing voltage pulses with short duty cycles.
====Microchannel plate====
When displaying fast one-shot events, the electron beam must deflect very quickly, with few electrons impinging on the screen, leading to a faint or invisible image on the display. Oscilloscope CRTs designed for very fast signals can give a brighter display by passing the electron beam through a micro-channel plate just before it reaches the screen. Through the phenomenon of secondary emission, this plate multiplies the number of electrons reaching the phosphor screen, giving a significant improvement in writing rate (brightness) and improved sensitivity and spot size as well.
====Graticules====
Most oscilloscopes have a graticule as part of the visual display, to facilitate measurements. The graticule may be permanently marked inside the face of the CRT, or it may be a transparent external plate made of glass or acrylic plastic. An internal graticule eliminates parallax error, but cannot be changed to accommodate different types of measurements. Oscilloscopes commonly provide a means for the graticule to be illuminated from the side, which improves its visibility.
====Image storage tubes====
These are found in analog phosphor storage oscilloscopes. These are distinct from digital storage oscilloscopes which rely on solid state digital memory to store the image.
Where a single brief event is monitored by an oscilloscope, such an event will be displayed by a conventional tube only while it actually occurs. The use of a long persistence phosphor may allow the image to be observed after the event, but only for a few seconds at best. This limitation can be overcome by the use of a direct view storage cathode-ray tube (storage tube). A storage tube will continue to display the event after it has occurred until such time as it is erased. A storage tube is similar to a conventional tube except that it is equipped with a metal grid coated with a dielectric layer located immediately behind the phosphor screen. An externally applied voltage to the mesh initially ensures that the whole mesh is at a constant potential. This mesh is constantly exposed to a low velocity electron beam from a 'flood gun' which operates independently of the main gun. This flood gun is not deflected like the main gun but constantly 'illuminates' the whole of the storage mesh. The initial charge on the storage mesh is such as to repel the electrons from the flood gun which are prevented from striking the phosphor screen.
When the main electron gun writes an image to the screen, the energy in the main beam is sufficient to create a 'potential relief' on the storage mesh. The areas where this relief is created no longer repel the electrons from the flood gun which now pass through the mesh and illuminate the phosphor screen. Consequently, the image that was briefly traced out by the main gun continues to be displayed after it has occurred. The image can be 'erased' by resupplying the external voltage to the mesh restoring its constant potential. The time for which the image can be displayed was limited because, in practice, the flood gun slowly neutralises the charge on the storage mesh. One way of allowing the image to be retained for longer is temporarily to turn off the flood gun. It is then possible for the image to be retained for several days. The majority of storage tubes allow for a lower voltage to be applied to the storage mesh which slowly restores the initial charge state. By varying this voltage a variable persistence is obtained. Turning off the flood gun and the voltage supply to the storage mesh allows such a tube to operate as a conventional oscilloscope tube.
===Vector monitors===
Vector monitors were used in early computer aided design systems and are in some late-1970s to mid-1980s arcade games such as Asteroids.
They draw graphics point-to-point, rather than scanning a raster. Either monochrome or color CRTs can be used in vector displays, and the essential principles of CRT design and operation are the same for either type of display; the main difference is in the beam deflection patterns and circuits.
===Data storage tubes===
The Williams tube or Williams-Kilburn tube was a cathode-ray tube used to electronically store binary data. It was used in computers of the 1940s as a random-access digital storage device. In contrast to other CRTs in this article, the Williams tube was not a display device, and in fact could not be viewed since a metal plate covered its screen.
===Cat's eye===
In some vacuum tube radio sets, a "Magic Eye" or "Tuning Eye" tube was provided to assist in tuning the receiver. Tuning would be adjusted until the width of a radial shadow was minimized. This was used instead of a more expensive electromechanical meter, which later came to be used on higher-end tuners when transistor sets lacked the high voltage required to drive the device. The same type of device was used with tape recorders as a recording level meter, and for various other applications including electrical test equipment.
===Charactrons===
Some displays for early computers (those that needed to display more text than was practical using vectors, or that required high speed for photographic output) used Charactron CRTs. These incorporate a perforated metal character mask (stencil), which shapes a wide electron beam to form a character on the screen. The system selects a character on the mask using one set of deflection circuits, but that causes the extruded beam to be aimed off-axis, so a second set of deflection plates has to re-aim the beam so it is headed toward the center of the screen. A third set of plates places the character wherever required. The beam is unblanked (turned on) briefly to draw the character at that position. Graphics could be drawn by selecting the position on the mask corresponding to the code for a space (in practice, they were simply not drawn), which had a small round hole in the center; this effectively disabled the character mask, and the system reverted to regular vector behavior. Charactrons had exceptionally long necks, because of the need for three deflection systems.
===Nimo===
Nimo was the trademark of a family of small specialised CRTs manufactured by Industrial Electronic Engineers. These had 10 electron guns which produced electron beams in the form of digits in a manner similar to that of the charactron. The tubes were either simple single-digit displays or more complex 4- or 6- digit displays produced by means of a suitable magnetic deflection system. Having little of the complexities of a standard CRT, the tube required a relatively simple driving circuit, and as the image was projected on the glass face, it provided a much wider viewing angle than competitive types (e.g., nixie tubes). However, their requirement for several voltages and their high voltage made them uncommon.
===Flood-beam CRT===
Flood-beam CRTs are small tubes that are arranged as pixels for large video walls like Jumbotrons. The first screen using this technology (called Diamond Vision by Mitsubishi Electric) was introduced by Mitsubishi Electric for the 1980 Major League Baseball All-Star Game. It differs from a normal CRT in that the electron gun within does not produce a focused controllable beam. Instead, electrons are sprayed in a wide cone across the entire front of the phosphor screen, basically making each unit act as a single light bulb. Each one is coated with a red, green or blue phosphor, to make up the color sub-pixels. This technology has largely been replaced with light-emitting diode displays. Unfocused and undeflected CRTs were used as grid-controlled stroboscope lamps since 1958. Electron-stimulated luminescence (ESL) lamps, which use the same operating principle, were released in 2011.
===Print-head CRT===
CRTs with an unphosphored front glass but with fine wires embedded in it were used as electrostatic print heads in the 1960s. The wires would pass the electron beam current through the glass onto a sheet of paper where the desired content was therefore deposited as an electrical charge pattern. The paper was then passed near a pool of liquid ink with the opposite charge. The charged areas of the paper attract the ink and thus form the image.
===Zeus – thin CRT display===
In the late 1990s and early 2000s Philips Research Laboratories experimented with a type of thin CRT known as the Zeus display, which contained CRT-like functionality in a flat-panel display. The cathode of this display was mounted under the front of the display, and the electrons from the cathode would be directed to the back to the display where they would stay until extracted by electrodes near the front of the display, and directed to the front of the display which had phosphor dots. The devices were demonstrated but never marketed.
===Slimmer CRT===
Some CRT manufacturers, both LG.Philips Displays (later LP Displays) and Samsung SDI, innovated CRT technology by creating a slimmer tube. Slimmer CRT had the trade names Superslim, Ultraslim, Vixlim (by Samsung) and Cybertube and Cybertube+ (both by LG Philips displays). A flat CRT has a depth. The depth of Superslim was and Ultraslim was .
==Health concerns==
===Ionizing radiation===
CRTs can emit a small amount of X-ray radiation; this is a result of the electron beam's bombardment of the shadow mask/aperture grille and phosphors, which produces bremsstrahlung (braking radiation) as the high-energy electrons are decelerated. The amount of radiation escaping the front of the monitor is widely considered to be not harmful. The Food and Drug Administration regulations in are used to strictly limit, for instance, TV receivers to 0.5 milliroentgens per hour at a distance of from any external surface; since 2007, most CRTs have emissions that fall well below this limit. Note that the roentgen is an outdated unit and does not account for dose absorption. The conversion rate is about .877 roentgen per rem. Assuming that the viewer absorbed the entire dose (which is unlikely), and that they watched TV for 2 hours a day, a .5 milliroentgen hourly dose would increase the viewers yearly dose by 320 millirem. For comparison, the average background radiation in the United States is 310 millirem a year. Negative effects of chronic radiation are not generally noticeable until doses over 20,000 millirem.
The density of the x-rays that would be generated by a CRT is low because the raster scan of a typical CRT distributes the energy of the electron beam across the entire screen. Voltages above 15,000 volts are enough to generate "soft" x-rays. However, since CRTs may stay on for several hours at a time, the amount of x-rays generated by the CRT may become significant, hence the importance of using materials to shield against x-rays, such as the thick leaded glass and barium-strontium glass used in CRTs.
===Toxicity===
Older color and monochrome CRTs may have been manufactured with toxic substances, such as cadmium, in the phosphors. The rear glass tube of modern CRTs may be made from leaded glass, which represent an environmental hazard if disposed of improperly. Since 1970, glass in the front panel (the viewable portion of the CRT) used strontium oxide rather than lead, though the rear of the CRT was still produced from leaded glass. Monochrome CRTs typically do not contain enough leaded glass to fail EPA TCLP tests. While the TCLP process grinds the glass into fine particles in order to expose them to weak acids to test for leachate, intact CRT glass does not leach (The lead is vitrified, contained inside the glass itself, similar to leaded glass crystalware).
===Flicker===
At low refresh rates (60 Hz and below), the periodic scanning of the display may produce a flicker that some people perceive more easily than others, especially when viewed with peripheral vision. Flicker is commonly associated with CRT as most TVs run at 50 Hz (PAL) or 60 Hz (NTSC), although there are some 100 Hz PAL TVs that are flicker-free. Typically only low-end monitors run at such low frequencies, with most computer monitors supporting at least 75 Hz and high-end monitors capable of 100 Hz or more to eliminate any perception of flicker. Though the 100 Hz PAL was often achieved using interleaved scanning, dividing the circuit and scan into two beams of 50 Hz. Non-computer CRTs or CRT for sonar or radar may have long persistence phosphor and are thus flicker free. If the persistence is too long on a video display, moving images will be blurred.
===High-frequency audible noise===
50 Hz/60 Hz CRTs used for TV operate with horizontal scanning frequencies of 15,750 and 15,734.27 Hz (for NTSC systems) or 15,625 Hz (for PAL systems). These frequencies are at the upper range of human hearing and are inaudible to many people; however, some people (especially children) will perceive a high-pitched tone near an operating CRT TV. The sound is due to magnetostriction in the magnetic core and periodic movement of windings of the flyback transformer but the sound can also be created by movement of the deflection coils, yoke or ferrite beads.
This problem does not occur on 100/120 Hz TVs and on non-CGA (Color Graphics Adapter) computer displays, because they use much higher horizontal scanning frequencies that produce sound which is inaudible to humans (22 kHz to over 100 kHz).
===Implosion===
If the glass wall is damaged, atmospheric pressure can implode the vacuum tube into dangerous fragments which accelerate inward and then spray at high speed in all directions. Although modern cathode-ray tubes used in TVs and computer displays have epoxy-bonded face-plates or other measures to prevent shattering of the envelope, CRTs must be handled carefully to avoid injury.
====Implosion protection====
Early CRTs had a glass plate over the screen that was bonded to it using glue, while later versions such as the LG Flatron used a resin, perhaps a UV-curable resin.
Older CRTs were mounted to the TV set using a frame. The band is tensioned by heating it, then mounting it on the CRT; the band cools afterwards, shrinking in size and putting the glass under compression, which strengthens the glass and reduces the necessary thickness (and hence weight) of the glass. This makes the band an integral component that should never be removed from an intact CRT that still has a vacuum; attempting to remove it may cause the CRT to implode. to achieve sufficient image brightness, a very high voltage (EHT or extra-high tension) is required, from a few thousand volts for a small oscilloscope CRT to tens of thousands for a larger screen color TV. This is many times greater than household power supply voltage. Even after the power supply is turned off, some associated capacitors and the CRT itself may retain a charge for some time and therefore dissipate that charge suddenly through a ground such as an inattentive human grounding a capacitor discharge lead. An average monochrome CRT may use 1–1.5 kV of anode voltage per inch. Special TEMPEST shielding can mitigate this effect. Such radiation of a potentially exploitable signal, however, occurs also with other display technologies and with electronics in general.
==Recycling==
Due to the toxins contained in CRT monitors the United States Environmental Protection Agency created rules (in October 2001) stating that CRTs must be brought to special e-waste recycling facilities. In November 2002, the EPA began fining companies that disposed of CRTs through landfills or incineration. Regulatory agencies, local and statewide, monitor the disposal of CRTs and other computer equipment.
As electronic waste, CRTs are considered one of the hardest types to recycle. CRTs have relatively high concentration of lead and , both of which are necessary for the display. There are several companies in the United States that charge a small fee to collect CRTs, then subsidize their labor by selling the harvested copper, wire, and printed circuit boards. The United States Environmental Protection Agency (EPA) includes discarded CRT monitors in its category of "hazardous household waste" but considers CRTs that have been set aside for testing to be commodities if they are not discarded, speculatively accumulated, or left unprotected from weather and other damage.
Various states participate in the recycling of CRTs, each with their reporting requirements for collectors and recycling facilities. For example, in California the recycling of CRTs is governed by CALRecycle, the California Department of Resources Recycling and Recovery through their Payment System. Recycling facilities that accept CRT devices from business and residential sector must obtain contact information such as address and phone number to ensure the CRTs come from a California source in order to participate in the CRT Recycling Payment System.
In Europe, disposal of CRT TVs and monitors is covered by the WEEE Directive.
Multiple methods have been proposed for the recycling of CRT glass. The methods involve thermal, mechanical and chemical processes. All proposed methods remove the lead oxide content from the glass. Some companies operated furnaces to separate the lead from the glass. A coalition called the Recytube project was once formed by several European companies to devise a method to recycle CRTs.
The funnel can be separated from the screen of the CRT using laser cutting, diamond saws or wires or using a resistively heated nichrome wire.
Leaded CRT glass was sold to be remelted into other CRTs, concrete, concrete and cement bricks, fiberglass insulation or used as flux in metals smelting.
A considerable portion of CRT glass is landfilled, where it can pollute the surrounding environment.
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"float glass",
"GTE",
"hours",
"monomer",
"trademark",
"Ferdinand Braun",
"Routledge",
"einzel lens",
"micro-channel plate",
"dielectric absorption",
"Science Museum, London",
"glass cockpit",
"Intaglio (printmaking)",
"electron",
"retro gaming",
"Triad (monitors)",
"Direct-view bistable storage tube",
"corona discharge",
"CRT projector",
"1980 Major League Baseball All-Star Game",
"vitrified",
"magnetostriction",
"incineration",
"Implosion (mechanical process)",
"MTV-1",
"Magic eye tube",
"lead",
"LCD television",
"lead glass",
"peripheral vision",
"monochrome",
"digital storage oscilloscope",
"Scintillation (physics)",
"George Johnstone Stoney",
"Philo Farnsworth",
"Eurogamer",
"Overscan",
"voltage multiplier",
"William Crookes",
"Hz",
"atmospheric pressure",
"Laser-powered phosphor display",
"AGC Inc.",
"barium",
"Penetron",
"interactive",
"Sony",
"PCMag",
"subatomic particle",
"Raster scan",
"Vertical blanking interval",
"millirem",
"deflection yoke",
"Image dissector",
"deformation (engineering)",
"WEEE Directive",
"Television/Radio Age (magazine)",
"diode",
"Samsung",
"Matsushita Electric",
"Allen B. DuMont",
"RAMDAC",
"NTSC",
"strontium",
"J. J. Thomson",
"Aiken tube",
"magnetic deflection",
"X-ray",
"Mitsubishi Electric",
"aquadag",
"oven",
"Nippon Electric Glass",
"moiré",
"cold-cathode",
"getter",
"overscan",
"Hitachi",
"video signal",
"Cromaclear",
"Comparison of CRT, LCD, plasma, and OLED displays",
"price fixing",
"radar",
"electron beams",
"screensaver",
"PAL",
"Tempest (codename)",
"acrylic glass",
"Strobe light",
"vacuum tube",
"CT-100",
"Digital imaging",
"Popular Science",
"hot cathode",
"Boeing 747-400",
"skin effect",
"Delta (letter)",
"rear-projection TV",
"vacuum",
"arcing",
"Radio Corporation of America",
"cathode ray",
"pressure",
"public domain",
"RCA",
"surface-conduction electron-emitter display",
"sonar",
"Sony PVM-4300",
"Light gun",
"Sony Watchman",
"Beam-index tube",
"television set",
"lead oxide",
"diffusion pump",
"refresh rate",
"epoxy",
"nichrome",
"Western Electric",
"Telefunken",
"Horizontal scan rate",
"United States Environmental Protection Agency",
"Johnson noise",
"raster scan",
"landfill",
"obsolete",
"eddy current",
"LED-backlit LCD",
"Monitor filter",
"Philips Research Laboratories",
"Röntgen Society",
"Times Mirror Company",
"LG.Philips Displays",
"Diamond Vision",
"Multisync monitor",
"plasma display",
"bremsstrahlung",
"video wall",
"implosion (mechanical process)",
"Vladimir K. Zworykin",
"area",
"dielectric",
"face diagonal",
"Raytheon Company",
"Cockcroft–Walton generator",
"flicker-free",
"Williams tube",
"LED display",
"watt",
"aperture grille",
"photolithography",
"Electron-stimulated luminescence",
"cathode",
"stencil"
] |
6,015 |
Crystal
|
A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.
The word crystal derives from the Ancient Greek word (), meaning both "ice" and "rock crystal", from (), "icy cold, frost".
Examples of large crystals include snowflakes, diamonds, and table salt. Most inorganic solids are not crystals but polycrystals, i.e. many microscopic crystals fused together into a single solid. Polycrystals include most metals, rocks, ceramics, and ice. A third category of solids is amorphous solids, where the atoms have no periodic structure whatsoever. Examples of amorphous solids include glass, wax, and many plastics.
Despite the name, lead crystal, crystal glass, and related products are not crystals, but rather types of glass, i.e. amorphous solids.
Crystals, or crystalline solids, are often used in pseudoscientific practices such as crystal therapy, and, along with gemstones, are sometimes associated with spellwork in Wiccan beliefs and related religious movements.
== Crystal structure (microscopic) ==
The scientific definition of a "crystal" is based on the microscopic arrangement of atoms inside it, called the crystal structure. A crystal is a solid where the atoms form a periodic arrangement. (Quasicrystals are an exception, see below).
Not all solids are crystals. For example, when liquid water starts freezing, the phase change begins with small ice crystals that grow until they fuse, forming a polycrystalline structure. In the final block of ice, each of the small crystals (called "crystallites" or "grains") is a true crystal with a periodic arrangement of atoms, but the whole polycrystal does not have a periodic arrangement of atoms, because the periodic pattern is broken at the grain boundaries. Most macroscopic inorganic solids are polycrystalline, including almost all metals, ceramics, ice, rocks, etc. Solids that are neither crystalline nor polycrystalline, such as glass, are called amorphous solids, also called glassy, vitreous, or noncrystalline. These have no periodic order, even microscopically. There are distinct differences between crystalline solids and amorphous solids: most notably, the process of forming a glass does not release the latent heat of fusion, but forming a crystal does.
A crystal structure (an arrangement of atoms in a crystal) is characterized by its unit cell, a small imaginary box containing one or more atoms in a specific spatial arrangement. The unit cells are stacked in three-dimensional space to form the crystal.
The symmetry of a crystal is constrained by the requirement that the unit cells stack perfectly with no gaps. There are 219 possible crystal symmetries (230 is commonly cited, but this treats chiral equivalents as separate entities), called crystallographic space groups. These are grouped into 7 crystal systems, such as cubic crystal system (where the crystals may form cubes or rectangular boxes, such as halite shown at right) or hexagonal crystal system (where the crystals may form hexagons, such as ordinary water ice).
== Crystal faces, shapes and crystallographic forms==
Crystals are commonly recognized, macroscopically, by their shape, consisting of flat faces with sharp angles. These shape characteristics are not necessary for a crystal—a crystal is scientifically defined by its microscopic atomic arrangement, not its macroscopic shape—but the characteristic macroscopic shape is often present and easy to see.
Euhedral crystals are those that have obvious, well-formed flat faces. Anhedral crystals do not, usually because the crystal is one grain in a polycrystalline solid.
The flat faces (also called facets) of a euhedral crystal are oriented in a specific way relative to the underlying atomic arrangement of the crystal: they are planes of relatively low Miller index. This occurs because some surface orientations are more stable than others (lower surface energy). As a crystal grows, new atoms attach easily to the rougher and less stable parts of the surface, but less easily to the flat, stable surfaces. Therefore, the flat surfaces tend to grow larger and smoother, until the whole crystal surface consists of these plane surfaces. (See diagram on right.)
One of the oldest techniques in the science of crystallography consists of measuring the three-dimensional orientations of the faces of a crystal, and using them to infer the underlying crystal symmetry.
A crystal's crystallographic forms are sets of possible faces of the crystal that are related by one of the symmetries of the crystal. For example, crystals of galena often take the shape of cubes, and the six faces of the cube belong to a crystallographic form that displays one of the symmetries of the isometric crystal system. Galena also sometimes crystallizes as octahedrons, and the eight faces of the octahedron belong to another crystallographic form reflecting a different symmetry of the isometric system. A crystallographic form is described by placing the Miller indices of one of its faces within brackets. For example, the octahedral form is written as {111}, and the other faces in the form are implied by the symmetry of the crystal.
Forms may be closed, meaning that the form can completely enclose a volume of space, or open, meaning that it cannot. The cubic and octahedral forms are examples of closed forms. All the forms of the isometric system are closed, while all the forms of the monoclinic and triclinic crystal systems are open. A crystal's faces may all belong to the same closed form, or they may be a combination of multiple open or closed forms.
A crystal's habit is its visible external shape. This is determined by the crystal structure (which restricts the possible facet orientations), the specific crystal chemistry and bonding (which may favor some facet types over others), and the conditions under which the crystal formed.
== Occurrence in nature ==
=== Rocks ===
By volume and weight, the largest concentrations of crystals in the Earth are part of its solid bedrock. Crystals found in rocks typically range in size from a fraction of a millimetre to several centimetres across, although exceptionally large crystals are occasionally found. , the world's largest known naturally occurring crystal is a crystal of beryl from Malakialina, Madagascar, long and in diameter, and weighing .
Some crystals have formed by magmatic and metamorphic processes, giving origin to large masses of crystalline rock. The vast majority of igneous rocks are formed from molten magma and the degree of crystallization depends primarily on the conditions under which they solidified. Such rocks as granite, which have cooled very slowly and under great pressures, have completely crystallized; but many kinds of lava were poured out at the surface and cooled very rapidly, and in this latter group a small amount of amorphous or glassy matter is common. Other crystalline rocks, the metamorphic rocks such as marbles, mica-schists and quartzites, are recrystallized. This means that they were at first fragmental rocks like limestone, shale and sandstone and have never been in a molten condition nor entirely in solution, but the high temperature and pressure conditions of metamorphism have acted on them by erasing their original structures and inducing recrystallization in the solid state.
Other rock crystals have formed out of precipitation from fluids, commonly water, to form druses or quartz veins. Evaporites such as halite, gypsum and some limestones have been deposited from aqueous solution, mostly owing to evaporation in arid climates.
=== Ice ===
Water-based ice in the form of snow, sea ice, and glaciers are common crystalline/polycrystalline structures on Earth and other planets. A single snowflake is a single crystal or a collection of crystals, while an ice cube is a polycrystal. Ice crystals may form from cooling liquid water below its freezing point, such as ice cubes or a frozen lake. Frost, snowflakes, or small ice crystals suspended in the air (ice fog) more often grow from a supersaturated gaseous-solution of water vapor and air, when the temperature of the air drops below its dew point, without passing through a liquid state. Another unusual property of water is that it expands rather than contracts when it crystallizes.
=== Organigenic crystals ===
Many living organisms are able to produce crystals grown from an aqueous solution, for example calcite and aragonite in the case of most molluscs or hydroxylapatite in the case of bones and teeth in vertebrates.
== Polymorphism and allotropy ==
The same group of atoms can often solidify in many different ways. Polymorphism is the ability of a solid to exist in more than one crystal form. For example, water ice is ordinarily found in the hexagonal form Ice Ih, but can also exist as the cubic Ice Ic, the rhombohedral ice II, and many other forms. The different polymorphs are usually called different phases.
In addition, the same atoms may be able to form noncrystalline phases. For example, water can also form amorphous ice, while SiO2 can form both fused silica (an amorphous glass) and quartz (a crystal). Likewise, if a substance can form crystals, it can also form polycrystals.
For pure chemical elements, polymorphism is referred to as allotropy. For example, diamond and graphite are two crystalline forms of carbon, while amorphous carbon is a noncrystalline form. Polymorphs, despite having the same atoms, may have very different properties. For example, diamond is the hardest substance known, while graphite is so soft that it is used as a lubricant. Chocolate can form six different types of crystals, but only one has the suitable hardness and melting point for candy bars and confections. Polymorphism in steel is responsible for its ability to be heat treated, giving it a wide range of properties.
Polyamorphism is a similar phenomenon where the same atoms can exist in more than one amorphous solid form.
== Crystallization ==
Crystallization is the process of forming a crystalline structure from a fluid or from materials dissolved in a fluid. (More rarely, crystals may be deposited directly from gas; see: epitaxy and frost.)
Crystallization is a complex and extensively-studied field, because depending on the conditions, a single fluid can solidify into many different possible forms. It can form a single crystal, perhaps with various possible phases, stoichiometries, impurities, defects, and habits. Or, it can form a polycrystal, with various possibilities for the size, arrangement, orientation, and phase of its grains. The final form of the solid is determined by the conditions under which the fluid is being solidified, such as the chemistry of the fluid, the ambient pressure, the temperature, and the speed with which all these parameters are changing.
Specific industrial techniques to produce large single crystals (called boules) include the Czochralski process and the Bridgman technique. Other less exotic methods of crystallization may be used, depending on the physical properties of the substance, including hydrothermal synthesis, sublimation, or simply solvent-based crystallization.
Large single crystals can be created by geological processes. For example, selenite crystals in excess of 10 m are found in the Cave of the Crystals in Naica, Mexico. For more details on geological crystal formation, see above.
Crystals can also be formed by biological processes, see above. Conversely, some organisms have special techniques to prevent crystallization from occurring, such as antifreeze proteins.
== Defects, impurities, and twinning ==
An ideal crystal has every atom in a perfect, exactly repeating pattern. However, in reality, most crystalline materials have a variety of crystallographic defects: places where the crystal's pattern is interrupted. The types and structures of these defects may have a profound effect on the properties of the materials.
A few examples of crystallographic defects include vacancy defects (an empty space where an atom should fit), interstitial defects (an extra atom squeezed in where it does not fit), and dislocations (see figure at right). Dislocations are especially important in materials science, because they help determine the mechanical strength of materials.
Another common type of crystallographic defect is an impurity, meaning that the "wrong" type of atom is present in a crystal. For example, a perfect crystal of diamond would only contain carbon atoms, but a real crystal might perhaps contain a few boron atoms as well. These boron impurities change the diamond's color to slightly blue. Likewise, the only difference between ruby and sapphire is the type of impurities present in a corundum crystal.
In semiconductors, a special type of impurity, called a dopant, drastically changes the crystal's electrical properties. Semiconductor devices, such as transistors, are made possible largely by putting different semiconductor dopants into different places, in specific patterns.
Twinning is a phenomenon somewhere between a crystallographic defect and a grain boundary. Like a grain boundary, a twin boundary has different crystal orientations on its two sides. But unlike a grain boundary, the orientations are not random, but related in a specific, mirror-image way.
Mosaicity is a spread of crystal plane orientations. A mosaic crystal consists of smaller crystalline units that are somewhat misaligned with respect to each other.
== Chemical bonds ==
In general, solids can be held together by various types of chemical bonds, such as metallic bonds, ionic bonds, covalent bonds, van der Waals bonds, and others. None of these are necessarily crystalline or non-crystalline. However, there are some general trends as follows:
Metals crystallize rapidly and are almost always polycrystalline, though there are exceptions like amorphous metal and single-crystal metals. The latter are grown synthetically, for example, fighter-jet turbines are typically made by first growing a single crystal of titanium alloy, increasing its strength and melting point over polycrystalline titanium. A small piece of metal may naturally form into a single crystal, such as Type 2 telluric iron, but larger pieces generally do not unless extremely slow cooling occurs. For example, iron meteorites are often composed of single crystal, or many large crystals that may be several meters in size, due to very slow cooling in the vacuum of space. The slow cooling may allow the precipitation of a separate phase within the crystal lattice, which form at specific angles determined by the lattice, called Widmanstatten patterns.
Ionic compounds typically form when a metal reacts with a non-metal, such as sodium with chlorine. These often form substances called salts, such as sodium chloride (table salt) or potassium nitrate (saltpeter), with crystals that are often brittle and cleave relatively easily. Ionic materials are usually crystalline or polycrystalline. In practice, large salt crystals can be created by solidification of a molten fluid, or by crystallization out of a solution. Some ionic compounds can be very hard, such as oxides like aluminium oxide found in many gemstones such as ruby and synthetic sapphire.
Covalently bonded solids (sometimes called covalent network solids) are typically formed from one or more non-metals, such as carbon or silicon and oxygen, and are often very hard, rigid, and brittle. These are also very common, notable examples being diamond and quartz respectively.
Weak van der Waals forces also help hold together certain crystals, such as crystalline molecular solids, as well as the interlayer bonding in graphite. Substances such as fats, lipids and wax form molecular bonds because the large molecules do not pack as tightly as atomic bonds. This leads to crystals that are much softer and more easily pulled apart or broken. Common examples include chocolates, candles, or viruses. Water ice and dry ice are examples of other materials with molecular bonding.Polymer materials generally will form crystalline regions, but the lengths of the molecules usually prevent complete crystallization—and sometimes polymers are completely amorphous.
== Quasicrystals ==
A quasicrystal consists of arrays of atoms that are ordered but not strictly periodic. They have many attributes in common with ordinary crystals, such as displaying a discrete pattern in x-ray diffraction, and the ability to form shapes with smooth, flat faces.
Quasicrystals are most famous for their ability to show five-fold symmetry, which is impossible for an ordinary periodic crystal (see crystallographic restriction theorem).
The International Union of Crystallography has redefined the term "crystal" to include both ordinary periodic crystals and quasicrystals ("any solid having an essentially discrete diffraction diagram").
Quasicrystals, first discovered in 1982, are quite rare in practice. Only about 100 solids are known to form quasicrystals, compared to about 400,000 periodic crystals known in 2004. The 2011 Nobel Prize in Chemistry was awarded to Dan Shechtman for the discovery of quasicrystals.
== Special properties from anisotropy ==
Crystals can have certain special electrical, optical, and mechanical properties that glass and polycrystals normally cannot. These properties are related to the anisotropy of the crystal, i.e. the lack of rotational symmetry in its atomic arrangement. One such property is the piezoelectric effect, where a voltage across the crystal can shrink or stretch it. Another is birefringence, where a double image appears when looking through a crystal. Moreover, various properties of a crystal, including electrical conductivity, electrical permittivity, and Young's modulus, may be different in different directions in a crystal. For example, graphite crystals consist of a stack of sheets, and although each individual sheet is mechanically very strong, the sheets are rather loosely bound to each other. Therefore, the mechanical strength of the material is quite different depending on the direction of stress.
Not all crystals have all of these properties. Conversely, these properties are not quite exclusive to crystals. They can appear in glasses or polycrystals that have been made anisotropic by working or stress—for example, stress-induced birefringence.
== Crystallography ==
Crystallography is the science of measuring the crystal structure (in other words, the atomic arrangement) of a crystal. One widely used crystallography technique is X-ray diffraction. Large numbers of known crystal structures are stored in crystallographic databases.
== Image gallery ==
File:Insulincrystals.jpg|Insulin crystals grown in earth orbit. The low gravity allows crystals to be grown with minimal defects.
File:Hoar frost macro2.jpg|Hoar frost: A type of ice crystal (picture taken from a distance of about 5 cm).
File:Gallium crystals.jpg|Gallium, a metal that easily forms large crystals.
File:Apatite-Rhodochrosite-Fluorite-169799.jpg|An apatite crystal sits front and center on cherry-red rhodochroite rhombs, purple fluorite cubes, quartz and a dusting of brass-yellow pyrite cubes.
File:Monokristalines Silizium für die Waferherstellung.jpg|Boules of silicon, like this one, are an important type of industrially-produced single crystal.
File:Bornite-Chalcopyrite-Pyrite-180794.jpg|A specimen consisting of a bornite-coated chalcopyrite crystal nestled in a bed of clear quartz crystals and lustrous pyrite crystals. The bornite-coated crystal is up to 1.5 cm across.
File:Calcite-millerite association.jpg|Needle-like millerite crystals partially encased in calcite crystal and oxidized on their surfaces to zaratite; from the Devonian Milwaukee Formation of Wisconsin
File:Crystallized sugar, multiple crystals and a single crystal grown from seed.jpg|Crystallized sugar. Crystals on the right were grown from a sugar cube, while the left from a single seed crystal taken from the right. Red dye was added to the solution when growing the larger crystal, but, insoluble with the solid sugar, all but small traces were forced to precipitate out as it grew.
|
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"X-ray diffraction",
"carbon",
"amorphous metal",
"hydroxylapatite",
"Polymer",
"rock (geology)",
"dopant",
"corundum",
"Space group",
"organisms",
"ice",
"vacancy defect",
"metal",
"facet",
"Time crystal",
"Ice Ih",
"lipid",
"Milwaukee Formation",
"mica-schist",
"Anticrystal",
"anisotropy",
"diffraction",
"rhombohedral",
"sodium",
"sapphire",
"bedrock",
"Polyamorphism",
"semiconductor",
"snow",
"aqueous solution",
"allotropy",
"International Union of Crystallography",
"chemical bond",
"teeth",
"dry ice",
"screw dislocation",
"dislocation",
"Hoar frost",
"lava",
"impurity",
"atom",
"ceramic",
"frost",
"Miller index",
"shale",
"molecular solid",
"Geometry",
"isometric crystal system",
"quartzite",
"Mosaicity",
"meteorite",
"Boule (crystal)",
"igneous rocks",
"ice fog",
"boule (crystal)",
"aragonite",
"Crystallography",
"Gallium",
"silicon",
"crystal system",
"photoelasticity",
"snowflake",
"single crystal",
"Liquid crystal",
"limestone",
"Exoskeleton",
"covalent network solids",
"Crystal twinning",
"zaratite",
"van der Waals force",
"pseudoscientific",
"solidification",
"graphite",
"crystallographic restriction theorem",
"Crystal growth",
"ceramics",
"plane (mathematics)",
"Crystallographic defect",
"Evaporite",
"Periodic function",
"latent heat of fusion",
"wax",
"surface energy",
"Czochralski process",
"anisotropic",
"crystallite",
"Ancient Greek",
"van der Waals bond",
"supersaturated",
"chlorine",
"vertebrate",
"electrical conductivity",
"Spanish National Research Council",
"magmatic",
"amorphous ice",
"fat",
"ion",
"crystal growth",
"Selenite (mineral)",
"polycrystal",
"meter",
"quasicrystal",
"crystallographic database",
"millerite",
"Devonian",
"space manufacturing",
"plastic",
"Anhedral (petrology)",
"druse (geology)",
"Recrystallization (chemistry)",
"heat treating",
"amorphous carbon",
"Widmanstatten pattern",
"cubic crystal system",
"hydrothermal synthesis",
"interstitial defect",
"materials science",
"Semiconductor device",
"Sublimation (chemistry)",
"telluric iron",
"Strength of materials",
"Colloidal crystal",
"Euhedral",
"Insulin",
"Quartz",
"piezoelectric effect",
"glacier",
"Ashcroft and Mermin",
"synthetic sapphire",
"Dan Shechtman",
"stress (mechanics)",
"Ionic compound",
"inorganic",
"beryl",
"crystallographic defect",
"table salt",
"glass",
"lead glass",
"Frost",
"metals",
"amorphous solid",
"salt (chemistry)",
"Young's modulus",
"grain boundaries",
"steel",
"saltpeter",
"Wisconsin",
"ionic bond",
"gemstone",
"covalent bond",
"diamond color",
"ruby",
"Covalently bonded",
"Crystal oscillator",
"calcite",
"Chocolate",
"quartz",
"Bridgman technique",
"diamond",
"evaporation",
"face (geometry)",
"honeycomb (geometry)",
"fused silica",
"crystal habit",
"metamorphism",
"metamorphic",
"crystallization",
"crystallography",
"polycrystalline",
"birefringence",
"ice Ic",
"Crystal habit",
"electrical permittivity",
"temperature",
"crystal therapy",
"galena",
"Madagascar",
"rocks",
"Metal",
"Cocrystal",
"bone",
"stoichiometries",
"Robert Scott (philologist)",
"molten",
"dangling bonds",
"aluminium oxide",
"Cave of the Crystals",
"metallic bond",
"Wicca",
"euhedral",
"mosaic crystal",
"Quasicrystal",
"sea ice",
"Nobel Prize in Chemistry",
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"hexagonal crystal system",
"phase (matter)",
"Work hardening",
"ice cube",
"dew point",
"molecule",
"halite",
"sandstone",
"Atomic packing factor",
"amorphous",
"boron",
"grain boundary",
"About.com",
"mollusc",
"gypsum",
"Spell (paranormal)",
"granite",
"Deposition (phase transition)",
"crystal structure",
"antifreeze protein",
"Polymorphism (materials science)",
"dodecahedron",
"x-ray diffraction",
"marble",
"solid",
"Henry George Liddell",
"ambient pressure",
"transistor",
"ice II",
"epitaxy",
"Phase (matter)"
] |
6,016 |
Cytosine
|
Cytosine () (symbol C or Cyt) is one of the four nucleotide bases found in DNA and RNA, along with adenine, guanine, and thymine (uracil in RNA). It is a pyrimidine derivative, with a heterocyclic aromatic ring and two substituents attached (an amine group at position 4 and a keto group at position 2). The nucleoside of cytosine is cytidine. In Watson–Crick base pairing, it forms three hydrogen bonds with guanine.
==History==
Cytosine was discovered and named by Albrecht Kossel and Albert Neumann in 1894 when it was hydrolyzed from calf thymus tissues. A structure was proposed in 1903, and was synthesized (and thus confirmed) in the laboratory in the same year.
In 1998, cytosine was used in an early demonstration of quantum information processing when Oxford University researchers implemented the Deutsch–Jozsa algorithm on a two qubit nuclear magnetic resonance quantum computer (NMRQC).
In March 2015, NASA scientists reported the formation of cytosine, along with uracil and thymine, from pyrimidine under the space-like laboratory conditions, which is of interest because pyrimidine has been found in meteorites although its origin is unknown.
==Chemical reactions==
Cytosine can be found as part of DNA, as part of RNA, or as a part of a nucleotide. As cytidine triphosphate (CTP), it can act as a co-factor to enzymes, and can transfer a phosphate to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP).
In DNA and RNA, cytosine is paired with guanine. However, it is inherently unstable, and can change into uracil (spontaneous deamination). This can lead to a point mutation if not repaired by the DNA repair enzymes such as uracil glycosylase, which cleaves a uracil in DNA.
Cytosine can also be methylated into 5-methylcytosine by an enzyme called DNA methyltransferase or be methylated and hydroxylated to make 5-hydroxymethylcytosine. The difference in rates of deamination of cytosine and 5-methylcytosine (to uracil and thymine) forms the basis of bisulfite sequencing.
==Biological function==
When found third in a codon of RNA, cytosine is synonymous with uracil, as they are interchangeable as the third base.
When found as the second base in a codon, the third is always interchangeable. For example, UCU, UCC, UCA and UCG are all serine, regardless of the third base.
Active enzymatic deamination of cytosine or 5-methylcytosine by the APOBEC family of cytosine deaminases could have both beneficial and detrimental implications on various cellular processes as well as on organismal evolution. The implications of deamination on 5-hydroxymethylcytosine, on the other hand, remains less understood.
== Theoretical aspects ==
Until October 2021, Cytosine had not been found in meteorites, which suggested the first strands of RNA and DNA had to look elsewhere to obtain this building block. Cytosine likely formed within some meteorite parent bodies, however did not persist within these bodies due to an effective deamination reaction into uracil.
In October 2021, Cytosine was announced as having been found in meteorites by researchers in a joint Japan/NASA project, that used novel methods of detection which avoided damaging nucleotides as they were extracted from meteorites.
|
[
"codon",
"bisulfite sequencing",
"adenosine triphosphate",
"point mutation",
"hydrogen bond",
"Watson–Crick base pair",
"deamination",
"cytidine triphosphate",
"DNA repair",
"nucleotide base",
"DNA",
"thymus",
"pyrimidine",
"DNA methyltransferase",
"nucleotide",
"guanine",
"RNA",
"aromatic ring",
"NASA",
"amine",
"adenine",
"Nuclear magnetic resonance quantum computer",
"heterocyclic",
"uracil",
"5-Methylcytosine",
"qubit",
"nucleoside",
"Deutsch–Jozsa algorithm",
"serine",
"enzyme",
"Hydroxylation",
"thymine",
"adenosine diphosphate",
"cytidine",
"Ketone",
"Guanine",
"Methylation",
"5-Hydroxymethylcytosine",
"quantum information processing",
"Albrecht Kossel",
"APOBEC"
] |
6,019 |
Computational chemistry
|
Computational chemistry is a branch of chemistry that uses computer simulations to assist in solving chemical problems. It uses methods of theoretical chemistry incorporated into computer programs to calculate the structures and properties of molecules, groups of molecules, and solids. The importance of this subject stems from the fact that, with the exception of some relatively recent findings related to the hydrogen molecular ion (dihydrogen cation), achieving an accurate quantum mechanical depiction of chemical systems analytically, or in a closed form, is not feasible. The complexity inherent in the many-body problem exacerbates the challenge of providing detailed descriptions of quantum mechanical systems. While computational results normally complement information obtained by chemical experiments, it can occasionally predict unobserved chemical phenomena.
== Overview ==
Computational chemistry differs from theoretical chemistry, which involves a mathematical description of chemistry. However, computational chemistry involves the usage of computer programs and additional mathematical skills in order to accurately model various chemical problems. In theoretical chemistry, chemists, physicists, and mathematicians develop algorithms and computer programs to predict atomic and molecular properties and reaction paths for chemical reactions. Computational chemists, in contrast, may simply apply existing computer programs and methodologies to specific chemical questions.
Historically, computational chemistry has had two different aspects:
Finding a starting point for a laboratory synthesis or assisting in understanding experimental data, such as the position and source of spectroscopic peaks.
Predicting the possibility of so-far unknown molecules or exploring reaction mechanisms not readily studied via experiments. The books that were influential in the early development of computational quantum chemistry include Linus Pauling and E. Bright Wilson's 1935 Introduction to Quantum Mechanics – with Applications to Chemistry, Eyring, Walter and Kimball's 1944 Quantum Chemistry, Heitler's 1945 Elementary Wave Mechanics – with Applications to Quantum Chemistry, and later Coulson's 1952 textbook Valence, each of which served as primary references for chemists in the decades to follow.
With the development of efficient computer technology in the 1940s, the solutions of elaborate wave equations for complex atomic systems began to be a realizable objective. In the early 1950s, the first semi-empirical atomic orbital calculations were performed. Theoretical chemists became extensive users of the early digital computers. One significant advancement was marked by Clemens C. J. Roothaan's 1951 paper in the Reviews of Modern Physics. This paper focused largely on the "LCAO MO" approach (Linear Combination of Atomic Orbitals Molecular Orbitals). For many years, it was the second-most cited paper in that journal. The first ab initio Hartree–Fock method calculations on diatomic molecules were performed in 1956 at MIT, using a basis set of Slater orbitals. For diatomic molecules, a systematic study using a minimum basis set and the first calculation with a larger basis set were published by Ransil and Nesbet respectively in 1960. The first polyatomic calculations using Gaussian orbitals were performed in the late 1950s. The first configuration interaction calculations were performed in Cambridge on the EDSAC computer in the 1950s using Gaussian orbitals by Boys and coworkers. By 1971, when a bibliography of ab initio calculations was published, the largest molecules included were naphthalene and azulene. Abstracts of many earlier developments in ab initio theory have been published by Schaefer.
In 1964, Hückel method calculations (using a simple linear combination of atomic orbitals (LCAO) method to determine electron energies of molecular orbitals of π electrons in conjugated hydrocarbon systems) of molecules, ranging in complexity from butadiene and benzene to ovalene, were generated on computers at Berkeley and Oxford. These empirical methods were replaced in the 1960s by semi-empirical methods such as CNDO.
In the early 1970s, efficient ab initio computer programs such as ATMOL, Gaussian, IBMOL, and POLYAYTOM, began to be used to speed ab initio calculations of molecular orbitals. Of these four programs, only Gaussian, now vastly expanded, is still in use, but many other programs are now in use.
One of the first mentions of the term computational chemistry can be found in the 1970 book Computers and Their Role in the Physical Sciences by Sidney Fernbach and Abraham Haskell Taub, where they state "It seems, therefore, that 'computational chemistry' can finally be more and more of a reality." During the 1970s, widely different methods began to be seen as part of a new emerging discipline of computational chemistry. The Journal of Computational Chemistry was first published in 1980.
Computational chemistry has featured in several Nobel Prize awards, most notably in 1998 and 2013. Walter Kohn, "for his development of the density-functional theory", and John Pople, "for his development of computational methods in quantum chemistry", received the 1998 Nobel Prize in Chemistry. Martin Karplus, Michael Levitt and Arieh Warshel received the 2013 Nobel Prize in Chemistry for "the development of multiscale models for complex chemical systems".
== Applications ==
There are several fields within computational chemistry.
The prediction of the molecular structure of molecules by the use of the simulation of forces, or more accurate quantum chemical methods, to find stationary points on the energy surface as the position of the nuclei is varied.
Storing and searching for data on chemical entities (see chemical databases).
Identifying correlations between chemical structures and properties (see quantitative structure–property relationship (QSPR) and quantitative structure–activity relationship (QSAR)).
Computational approaches to help in the efficient synthesis of compounds.
Computational approaches to design molecules that interact in specific ways with other molecules (e.g. drug design and catalysis).
These fields can give rise to several applications as shown below.
=== Catalysis ===
Computational chemistry is a tool for analyzing catalytic systems without doing experiments. Modern electronic structure theory and density functional theory has allowed researchers to discover and understand catalysts. Computational studies apply theoretical chemistry to catalysis research. Density functional theory methods calculate the energies and orbitals of molecules to give models of those structures. Using these methods, researchers can predict values like activation energy, site reactivity and other thermodynamic properties. Methods like density functional theory can be used to model drug molecules and find their properties, like their HOMO and LUMO energies and molecular orbitals. Computational chemists also help companies with developing informatics, infrastructure and designs of drugs.
Aside from drug synthesis, drug carriers are also researched by computational chemists for nanomaterials. It allows researchers to simulate environments to test the effectiveness and stability of drug carriers. Understanding how water interacts with these nanomaterials ensures stability of the material in human bodies. These computational simulations help researchers optimize the material find the best way to structure these nanomaterials before making them.
=== Computational chemistry databases ===
Databases are useful for both computational and non computational chemists in research and verifying the validity of computational methods. Empirical data is used to analyze the error of computational methods against experimental data. Empirical data helps researchers with their methods and basis sets to have greater confidence in the researchers results. Computational chemistry databases are also used in testing software or hardware for computational chemistry.
Databases can also use purely calculated data. Purely calculated data uses calculated values over experimental values for databases. Purely calculated data avoids dealing with these adjusting for different experimental conditions like zero-point energy. These calculations can also avoid experimental errors for difficult to test molecules. Though purely calculated data is often not perfect, identifying issues is often easier for calculated data than experimental.
RCSB: Stores publicly available 3D models of macromolecules (proteins, nucleic acids) and small molecules (drugs, inhibitors)
ChEMBL: Contains data from research on drug development such as assay results. Methods that do not include any empirical or semi-empirical parameters in their equations – being derived directly from theory, with no inclusion of experimental data – are called ab initio methods. A theoretical approximation is rigorously defined on first principles and then solved within an error margin that is qualitatively known beforehand. If numerical iterative methods must be used, the aim is to iterate until full machine accuracy is obtained (the best that is possible with a finite word length on the computer, and within the mathematical and/or physical approximations made).
Ab initio methods need to define a level of theory (the method) and a basis set. A basis set consists of functions centered on the molecule's atoms. These sets are then used to describe molecular orbitals via the linear combination of atomic orbitals (LCAO) molecular orbital method ansatz.
A common type of ab initio electronic structure calculation is the Hartree–Fock method (HF), an extension of molecular orbital theory, where electron-electron repulsions in the molecule are not specifically taken into account; only the electrons' average effect is included in the calculation. As the basis set size increases, the energy and wave function tend towards a limit called the Hartree–Fock limit. These types of calculations are termed post–Hartree–Fock methods. By continually improving these methods, scientists can get increasingly closer to perfectly predicting the behavior of atomic and molecular systems under the framework of quantum mechanics, as defined by the Schrödinger equation. To obtain exact agreement with the experiment, it is necessary to include specific terms, some of which are far more important for heavy atoms than lighter ones.
In most cases, the Hartree–Fock wave function occupies a single configuration or determinant. In some cases, particularly for bond-breaking processes, this is inadequate, and several configurations must be used.
The total molecular energy can be evaluated as a function of the molecular geometry; in other words, the potential energy surface. Such a surface can be used for reaction dynamics. The stationary points of the surface lead to predictions of different isomers and the transition structures for conversion between isomers, but these can be determined without full knowledge of the complete surface.
==== Chemical dynamics ====
After the electronic and nuclear variables are separated within the Born–Oppenheimer representation), the wave packet corresponding to the nuclear degrees of freedom is propagated via the time evolution operator (physics) associated to the time-dependent Schrödinger equation (for the full molecular Hamiltonian). In the complementary energy-dependent approach, the time-independent Schrödinger equation is solved using the scattering theory formalism. The potential representing the interatomic interaction is given by the potential energy surfaces. In general, the potential energy surfaces are coupled via the vibronic coupling terms.
The most popular methods for propagating the wave packet associated to the molecular geometry are:
the Chebyshev (real) polynomial,
the multi-configuration time-dependent Hartree method (MCTDH),
the semiclassical method
and the split operator technique explained below.
===== Split operator technique =====
How a computational method solves quantum equations impacts the accuracy and efficiency of the method. The split operator technique is one of these methods for solving differential equations. In computational chemistry, split operator technique reduces computational costs of simulating chemical systems. Computational costs are about how much time it takes for computers to calculate these chemical systems, as it can take days for more complex systems. Quantum systems are difficult and time-consuming to solve for humans. Split operator methods help computers calculate these systems quickly by solving the sub problems in a quantum differential equation. The method does this by separating the differential equation into two different equations, like when there are more than two operators. Once solved, the split equations are combined into one equation again to give an easily calculable solution.
=== Semi-empirical methods ===
Semi-empirical quantum chemistry methods are based on the Hartree–Fock method formalism, but make many approximations and obtain some parameters from empirical data. They were very important in computational chemistry from the 60s to the 90s, especially for treating large molecules where the full Hartree–Fock method without the approximations were too costly. The use of empirical parameters appears to allow some inclusion of correlation effects into the methods.
Primitive semi-empirical methods were designed even before, where the two-electron part of the Hamiltonian is not explicitly included. For π-electron systems, this was the Hückel method proposed by Erich Hückel, and for all valence electron systems, the extended Hückel method proposed by Roald Hoffmann. Sometimes, Hückel methods are referred to as "completely empirical" because they do not derive from a Hamiltonian. Yet, the term "empirical methods", or "empirical force fields" is usually used to describe molecular mechanics.
=== Molecular mechanics ===
In many cases, large molecular systems can be modeled successfully while avoiding quantum mechanical calculations entirely. Molecular mechanics simulations, for example, use one classical expression for the energy of a compound, for instance, the harmonic oscillator. All constants appearing in the equations must be obtained beforehand from experimental data or ab initio calculations.
=== Molecular dynamics ===
Molecular dynamics (MD) use either quantum mechanics, molecular mechanics or a mixture of both to calculate forces which are then used to solve Newton's laws of motion to examine the time-dependent behavior of systems. The result of a molecular dynamics simulation is a trajectory that describes how the position and velocity of particles varies with time. The phase point of a system described by the positions and momenta of all its particles on a previous time point will determine the next phase point in time by integrating over Newton's laws of motion.
=== Monte Carlo ===
Monte Carlo (MC) generates configurations of a system by making random changes to the positions of its particles, together with their orientations and conformations where appropriate. It is a random sampling method, which makes use of the so-called importance sampling. Importance sampling methods are able to generate low energy states, as this enables properties to be calculated accurately. The potential energy of each configuration of the system can be calculated, together with the values of other properties, from the positions of the atoms.
=== Quantum mechanics/molecular mechanics (QM/MM) ===
QM/MM is a hybrid method that attempts to combine the accuracy of quantum mechanics with the speed of molecular mechanics. It is useful for simulating very large molecules such as enzymes.
=== Quantum Computational Chemistry ===
Quantum computational chemistry aims to exploit quantum computing to simulate chemical systems, distinguishing itself from the QM/MM (Quantum Mechanics/Molecular Mechanics) approach. While QM/MM uses a hybrid approach, combining quantum mechanics for a portion of the system with classical mechanics for the remainder, quantum computational chemistry exclusively uses quantum computing methods to represent and process information, such as Hamiltonian operators.
Conventional computational chemistry methods often struggle with the complex quantum mechanical equations, particularly due to the exponential growth of a quantum system's wave function. Quantum computational chemistry addresses these challenges using quantum computing methods, such as qubitization and quantum phase estimation, which are believed to offer scalable solutions.
Qubitization involves adapting the Hamiltonian operator for more efficient processing on quantum computers, enhancing the simulation's efficiency. Quantum phase estimation, on the other hand, assists in accurately determining energy eigenstates, which are critical for understanding the quantum system's behavior.
While these techniques have advanced the field of computational chemistry, especially in the simulation of chemical systems, their practical application is currently limited mainly to smaller systems due to technological constraints. Nevertheless, these developments may lead to significant progress towards achieving more precise and resource-efficient quantum chemistry simulations.
In quantum chemistry, particularly, the complexity can grow exponentially with the number of electrons involved in the system. This exponential growth is a significant barrier to simulating large or complex systems accurately.
Advanced algorithms in both fields strive to balance accuracy with computational efficiency. For instance, in MD, methods like Verlet integration or Beeman's algorithm are employed for their computational efficiency. In quantum chemistry, hybrid methods combining different computational approaches (like QM/MM) are increasingly used to tackle large biomolecular systems.
=== Algorithmic complexity examples ===
The following list illustrates the impact of computational complexity on algorithms used in chemical computations. It is important to note that while this list provides key examples, it is not comprehensive and serves as a guide to understanding how computational demands influence the selection of specific computational methods in chemistry.
=== Molecular dynamics ===
==== Algorithm ====
Solves Newton's equations of motion for atoms and molecules.
==== Complexity ====
The standard pairwise interaction calculation in MD leads to an \mathcal{O}(N^2)complexity for N particles. This is because each particle interacts with every other particle, resulting in \frac{N(N-1)}{2} interactions. Advanced algorithms, such as the Ewald summation or Fast Multipole Method, reduce this to \mathcal{O}(N \log N) or even \mathcal{O}(N) by grouping distant particles and treating them as a single entity or using clever mathematical approximations.
=== Quantum mechanics/molecular mechanics (QM/MM) ===
==== Algorithm ====
Combines quantum mechanical calculations for a small region with molecular mechanics for the larger environment.
==== Complexity ====
The complexity of QM/MM methods depends on both the size of the quantum region and the method used for quantum calculations. For example, if a Hartree-Fock method is used for the quantum part, the complexity can be approximated as \mathcal{O}(M^2), where M is the number of basis functions in the quantum region. This complexity arises from the need to solve a set of coupled equations iteratively until self-consistency is achieved.
=== Hartree-Fock method ===
==== Algorithm ====
Finds a single Fock state that minimizes the energy.
==== Complexity ====
NP-hard or NP-complete as demonstrated by embedding instances of the Ising model into Hartree-Fock calculations. The Hartree-Fock method involves solving the Roothaan-Hall equations, which scales as \mathcal{O}(N^3) to \mathcal{O}(N) depending on implementation, with N being the number of basis functions. The computational cost mainly comes from evaluating and transforming the two-electron integrals. This proof of NP-hardness or NP-completeness comes from embedding problems like the Ising model into the Hartree-Fock formalism.]]
=== Density functional theory ===
==== Algorithm ====
Investigates the electronic structure or nuclear structure of many-body systems such as atoms, molecules, and the condensed phases.
==== Complexity ====
Traditional implementations of DFT typically scale as \mathcal{O}(N^3), mainly due to the need to diagonalize the Kohn-Sham matrix. The diagonalization step, which finds the eigenvalues and eigenvectors of the matrix, contributes most to this scaling. Recent advances in DFT aim to reduce this complexity through various approximations and algorithmic improvements.
=== Standard CCSD and CCSD(T) method ===
==== Algorithm ====
CCSD and CCSD(T) methods are advanced electronic structure techniques involving single, double, and in the case of CCSD(T), perturbative triple excitations for calculating electronic correlation effects.
==== Complexity ====
===== CCSD =====
Scales as \mathcal{O}(M^6) where M is the number of basis functions. This intense computational demand arises from the inclusion of single and double excitations in the electron correlation calculation.
For other methods like MD or DFT, the computational complexity is often empirically observed and supported by algorithm analysis. In these cases, the proof of correctness is less about formal mathematical proofs and more about consistently observing the computational behaviour across various systems and implementations.
Molecules consist of nuclei and electrons, so the methods of quantum mechanics apply. Computational chemists often attempt to solve the non-relativistic Schrödinger equation, with relativistic corrections added, although some progress has been made in solving the fully relativistic Dirac equation. In principle, it is possible to solve the Schrödinger equation in either its time-dependent or time-independent form, as appropriate for the problem in hand; in practice, this is not possible except for very small systems. Therefore, a great number of approximate methods strive to achieve the best trade-off between accuracy and computational cost.
Accuracy can always be improved with greater computational cost. Significant errors can present themselves in ab initio models comprising many electrons, due to the computational cost of full relativistic-inclusive methods.
There is some dispute within the field whether or not the latter methods are sufficient to describe complex chemical reactions, such as those in biochemistry. Large molecules can be studied by semi-empirical approximate methods. Even larger molecules are treated by classical mechanics methods that use what are called molecular mechanics (MM).In QM-MM methods, small parts of large complexes are treated quantum mechanically (QM), and the remainder is treated approximately (MM).
== Software packages ==
Many self-sufficient computational chemistry software packages exist. Some include many methods covering a wide range, while others concentrate on a very specific range or even on one method. Details of most of them can be found in:
Biomolecular modelling programs: proteins, nucleic acid.
Molecular mechanics programs.
Quantum chemistry and solid state-physics software supporting several methods.
Molecular design software
Semi-empirical programs.
Valence bond programs.
== Specialized journals on computational chemistry ==
Annual Reports in Computational Chemistry
Computational and Theoretical Chemistry
Computational and Theoretical Polymer Science
Computers & Chemical Engineering
Journal of Chemical Information and Modeling
Journal of Chemical Software
Journal of Chemical Theory and Computation
Journal of Cheminformatics
Journal of Computational Chemistry
Journal of Computer Aided Chemistry
Journal of Computer Chemistry Japan
Journal of Computer-aided Molecular Design
Journal of Theoretical and Computational Chemistry
Molecular Informatics
Theoretical Chemistry Accounts
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6,020 |
Crash (Ballard novel)
|
Crash is a novel by British author J. G. Ballard, first published in 1973 with cover designed by Bill Botten. It follows a group of car-crash fetishists who, inspired by the famous crashes of celebrities, become sexually aroused by staging and participating in car accidents.
The novel was released to divided critical reception, with many reviewers horrified by its provocative content. It was adapted into a controversial 1996 film of the same name by David Cronenberg.
==Synopsis==
The story is told through the eyes of narrator James Ballard, named after the author himself, but it centers on the sinister figure of Dr. Robert Vaughan, a former TV scientist turned "nightmare angel of the highways". James meets Vaughan after being injured in a car crash near London Airport. Gathering around Vaughan is a group of alienated people, all of them former crash victims, who follow him in his pursuit to re-enact the crashes of Hollywood celebrities such as Jayne Mansfield and James Dean, in order to experience what the narrator calls "a new sexuality, born from a perverse technology". Vaughan's ultimate fantasy is to die in a head-on collision with movie star Elizabeth Taylor.
== Development ==
The Papers of J. G. Ballard at the British Library include two revised drafts of Crash (Add MS 88938/3/8). Scanned extracts from Ballard's drafts are included in Crash: The Collector's Edition, ed. Chris Beckett.
In 1971, Harley Cokeliss directed a short film entitled Crash! based on a chapter in J. G. Ballard's book The Atrocity Exhibition, where Ballard is featured, talking about the ideas in his book. British actress Gabrielle Drake appeared as a passenger and car-crash victim. Ballard later developed the idea, resulting in Crash. In his draft of the novel he mentioned Drake by name, but references to her were removed from the published version.
==Interpretation==
Crash has been difficult to characterize as a novel. At some points in his career, Ballard claimed that Crash was a "cautionary tale", a view that he would later regret, asserting that it is in fact "a psychopathic hymn. But it is a psychopathic hymn which has a point". Likewise, Ballard previously characterized it a science fiction novel, a position he would later take back.
Jean Baudrillard wrote an analysis of Crash in Simulacra and Simulation in which he declared it "the first great novel of the universe of simulation". He made note of how the fetish in the story conflates the functionality of the automobiles with that of the human body and how the characters' injuries and the damage to the vehicles are used as equivalent signs. To him, the hyperfunctionality leads to the dysfunction in the story. Quotes were used extensively to illustrate that the language of the novel employs plain, mechanical terms for the parts of the automobile and proper, medical language for human sex organs and acts. The story is interpreted as showing a merger between technology, sexuality, and death, and he further argued that by pointing out Vaughan's character takes and keeps photos of the car crashes and the mutilated bodies involved. Baudrillard stated that there is no moral judgment about the events within the novel but that Ballard himself intended it as a warning against a cultural trend.
The story can be classed as dystopic. A 1973 review in The New York Times was equally horrified: "Crash is, hands-down, the most repulsive book I've yet to come across."
However, retrospective opinion now considers Crash to be one of Ballard's best and most challenging works. Reassessing Crash in The Guardian, Zadie Smith wrote, "Crash is an existential book about how everybody uses everything. How everything uses everybody. And yet it is not a hopeless vision." On Ballard's legacy, she writes: "In Ballard's work there is always this mix of futuristic dread and excitement, a sweet spot where dystopia and utopia converge. For we cannot say we haven't got precisely what we dreamed of, what we always wanted, so badly."
==References in popular art==
===Music===
The Normal's 1978 song "Warm Leatherette" was inspired by the novel, and later covered in 1980 by Grace Jones. Similarly inspired was "Miss the Girl," a 1983 single by The Creatures.
The Manic Street Preachers' song "Mausoleum" from 1994's The Holy Bible contains the famous Ballard quote about his reasons for writing the book, "I wanted to rub the human face in its own vomit. I wanted to force it to look in the mirror." John Foxx's album Metamatic contains songs that have Ballardian themes, such as "No-one Driving".
===Other film adaptations===
An apparently unauthorized adaptation of Crash called Nightmare Angel was filmed in 1986 by Susan Emerling and Zoe Beloff. This short film bears the credit "Inspired by J. G. Ballard".
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6,021 |
C (programming language)
|
C (pronounced – similar to letter c) is a general-purpose programming language. It was created in the 1970s by Dennis Ritchie and remains very widely used and influential. By design, C's features cleanly reflect the capabilities of the targeted CPUs. It has found lasting use in operating systems code (especially in kernels), device drivers, and protocol stacks, but its use in application software has been decreasing. C is commonly used on computer architectures that range from the largest supercomputers to the smallest microcontrollers and embedded systems.
A successor to the programming language B, C was originally developed at Bell Labs by Ritchie between 1972 and 1973 to construct utilities running on Unix. It was applied to re-implementing the kernel of the Unix operating system. with C compilers available for practically all modern computer architectures and operating systems. The book The C Programming Language, co-authored by the original language designer, served for many years as the de facto standard for the language.
== Overview ==
C is an imperative, procedural language in the ALGOL tradition. It has a static type system. In C, all executable code is contained within subroutines (also called "functions", though not in the sense of functional programming). Function parameters are passed by value, although arrays are passed as pointers, i.e. the address of the first item in the array. Pass-by-reference is simulated in C by explicitly passing pointers to the thing being referenced.
C program source text is free-form code. Semicolons terminate statements, while curly braces are used to group statements into blocks.
The C language also exhibits the following characteristics:
The language has a small, fixed number of keywords, including a full set of control flow primitives: if/else, for, do/while, while, and switch. User-defined names are not distinguished from keywords by any kind of sigil.
It has a large number of arithmetic, bitwise, and logic operators: , etc.
More than one assignment may be performed in a single statement.
Functions:
Function return values can be ignored, when not needed.
Function and data pointers permit ad hoc run-time polymorphism.
Functions may not be defined within the lexical scope of other functions.
Variables may be defined within a function, with scope.
A function may call itself, so recursion is supported.
Data typing is static, but weakly enforced; all data has a type, but implicit conversions are possible.
User-defined (typedef) and compound types are possible.
Heterogeneous aggregate data types (struct) allow related data elements to be accessed and assigned as a unit. The contents of whole structs cannot be compared using a single built-in operator (the elements must be compared individually).
Union is a structure with overlapping members; it allows multiple data types to share the same memory location.
Array indexing is a secondary notation, defined in terms of pointer arithmetic. Whole arrays cannot be assigned or compared using a single built-in operator. There is no "array" keyword in use or definition; instead, square brackets indicate arrays syntactically, for example month[11].
Enumerated types are possible with the enum keyword. They are freely interconvertible with integers.
Strings are not a distinct data type, but are conventionally implemented as null-terminated character arrays.
Low-level access to computer memory is possible by converting machine addresses to pointers.
Procedures (subroutines not returning values) are a special case of function, with an empty return type void.
Memory can be allocated to a program with calls to library routines.
A preprocessor performs macro definition, source code file inclusion, and conditional compilation.
There is a basic form of modularity: files can be compiled separately and linked together, with control over which functions and data objects are visible to other files via static and extern attributes.
Complex functionality such as I/O, string manipulation, and mathematical functions are consistently delegated to library routines.
The generated code after compilation has relatively straightforward needs on the underlying platform, which makes it suitable for creating operating systems and for use in embedded systems.
While C does not include certain features found in other languages (such as object orientation and garbage collection), these can be implemented or emulated, often through the use of external libraries (e.g., the GLib Object System or the Boehm garbage collector).
=== Relations to other languages ===
Many later languages have borrowed directly or indirectly from C, including C++, C#, Unix's C shell, D, Go, Java, JavaScript (including transpilers), Julia, Limbo, LPC, Objective-C, Perl, PHP, Python, Ruby, Rust, Swift, Verilog and SystemVerilog (hardware description languages). and Thompson modified the syntax to be less 'wordy' and similar to a simplified ALGOL known as SMALGOL. He called the result B,
==== Structures and Unix kernel re-write ====
At Version 4 Unix, released in November 1973, the Unix kernel was extensively re-implemented in C.
Unix was one of the first operating system kernels implemented in a language other than assembly. Earlier instances include the Multics system (which was written in PL/I) and Master Control Program (MCP) for the Burroughs B5000 (which was written in ALGOL) in 1961. In around 1977, Ritchie and Stephen C. Johnson made further changes to the language to facilitate portability of the Unix operating system. Johnson's Portable C Compiler served as the basis for several implementations of C on new platforms.
=== K&R C ===
In 1978 Brian Kernighan and Dennis Ritchie published the first edition of The C Programming Language. Known as K&R from the initials of its authors, the book served for many years as an informal specification of the language. The version of C that it describes is commonly referred to as "K&R C". As this was released in 1978, it is now also referred to as C78. The second edition of the book covers the later ANSI C standard, described below.
K&R introduced several language features:
Standard I/O library
long int data type
unsigned int data type
Compound assignment operators of the form =op (such as =-) were changed to the form op= (that is, -=) to remove the semantic ambiguity created by constructs such as i=-10, which had been interpreted as i =- 10 (decrement i by 10) instead of the possibly intended i = -10 (let i be −10).
Even after the publication of the 1989 ANSI standard, for many years K&R C was still considered the "lowest common denominator" to which C programmers restricted themselves when maximum portability was desired, since many older compilers were still in use, and because carefully written K&R C code can be legal Standard C as well.
In early versions of C, only functions that return types other than int must be declared if used before the function definition; functions used without prior declaration were presumed to return type int.
For example:
long some_function(); /* This is a function declaration, so the compiler can know the name and return type of this function. */
/* int */ other_function(); /* Another function declaration. Because this is an early version of C, there is an implicit 'int' type here. A comment shows where the explicit 'int' type specifier would be required in later versions. */
/* int */ calling_function() /* This is a function definition, including the body of the code following in the { curly brackets }. Because no return type is specified, the function implicitly returns an 'int' in this early version of C. */
{
long test1;
register /* int */ test2; /* Again, note that 'int' is not required here. The 'int' type specifier */
/* in the comment would be required in later versions of C. */
/* The 'register' keyword indicates to the compiler that this variable should */
/* ideally be stored in a register as opposed to within the stack frame. */
test1 = some_function();
if (test1 > 1)
test2 = 0;
else
test2 = other_function();
return test2;
}
The int type specifiers which are commented out could be omitted in K&R C, but are required in later standards.
Since K&R function declarations did not include any information about function arguments, function parameter type checks were not performed, although some compilers would issue a warning message if a local function was called with the wrong number of arguments, or if different calls to an external function used different numbers or types of arguments. Separate tools such as Unix's lint utility were developed that (among other things) could check for consistency of function use across multiple source files.
In the years following the publication of K&R C, several features were added to the language, supported by compilers from AT&T (in particular PCC) and some other vendors. These included:
void functions (i.e., functions with no return value)
functions returning struct or union types (previously only a single pointer, integer or float could be returned)
assignment for struct data types
enumerated types (previously, preprocessor definitions for integer fixed values were used, e.g. #define GREEN 3)
The large number of extensions and lack of agreement on a standard library, together with the language popularity and the fact that not even the Unix compilers precisely implemented the K&R specification, led to the necessity of standardization.
=== ANSI C and ISO C ===
During the late 1970s and 1980s, versions of C were implemented for a wide variety of mainframe computers, minicomputers, and microcomputers, including the IBM PC, as its popularity began to increase significantly.
In 1983 the American National Standards Institute (ANSI) formed a committee, X3J11, to establish a standard specification of C. X3J11 based the C standard on the Unix implementation; however, the non-portable portion of the Unix C library was handed off to the IEEE working group 1003 to become the basis for the 1988 POSIX standard. In 1989, the C standard was ratified as ANSI X3.159-1989 "Programming Language C". This version of the language is often referred to as ANSI C, Standard C, or sometimes C89.
In 1990 the ANSI C standard (with formatting changes) was adopted by the International Organization for Standardization (ISO) as ISO/IEC 9899:1990, which is sometimes called C90. Therefore, the terms "C89" and "C90" refer to the same programming language.
ANSI, like other national standards bodies, no longer develops the C standard independently, but defers to the international C standard, maintained by the working group ISO/IEC JTC1/SC22/WG14. National adoption of an update to the international standard typically occurs within a year of ISO publication.
One of the aims of the C standardization process was to produce a superset of K&R C, incorporating many of the subsequently introduced unofficial features. The standards committee also included several additional features such as function prototypes (borrowed from C++), void pointers, support for international character sets and locales, and preprocessor enhancements. Although the syntax for parameter declarations was augmented to include the style used in C++, the K&R interface continued to be permitted, for compatibility with existing source code.
C89 is supported by current C compilers, and most modern C code is based on it. Any program written only in Standard C and without any hardware-dependent assumptions will run correctly on any platform with a conforming C implementation, within its resource limits. Without such precautions, programs may compile only on a certain platform or with a particular compiler, due, for example, to the use of non-standard libraries, such as GUI libraries, or to a reliance on compiler- or platform-specific attributes such as the exact size of data types and byte endianness.
In cases where code must be compilable by either standard-conforming or K&R C-based compilers, the __STDC__ macro can be used to split the code into Standard and K&R sections to prevent the use on a K&R C-based compiler of features available only in Standard C.
After the ANSI/ISO standardization process, the C language specification remained relatively static for several years. In 1995, Normative Amendment 1 to the 1990 C standard (ISO/IEC 9899/AMD1:1995, known informally as C95) was published, to correct some details and to add more extensive support for international character sets.
=== C99 ===
The C standard was further revised in the late 1990s, leading to the publication of ISO/IEC 9899:1999 in 1999, which is commonly referred to as "C99". It has since been amended three times by Technical Corrigenda.
C99 introduced several new features, including inline functions, several new data types (including long long int and a complex type to represent complex numbers), variable-length arrays and flexible array members, improved support for IEEE 754 floating point, support for variadic macros (macros of variable arity), and support for one-line comments beginning with //, as in BCPL or C++. Many of these had already been implemented as extensions in several C compilers.
C99 is for the most part backward compatible with C90, but is stricter in some ways; in particular, a declaration that lacks a type specifier no longer has int implicitly assumed. A standard macro __STDC_VERSION__ is defined with value 199901L to indicate that C99 support is available. GCC, Solaris Studio, and other C compilers now support many or all of the new features of C99. The C compiler in Microsoft Visual C++, however, implements the C89 standard and those parts of C99 that are required for compatibility with C++11.
In addition, the C99 standard requires support for identifiers using Unicode in the form of escaped characters (e.g. or ) and suggests support for raw Unicode names.
=== C11 ===
Work began in 2007 on another revision of the C standard, informally called "C1X" until its official publication of ISO/IEC 9899:2011 on December 8, 2011. The C standards committee adopted guidelines to limit the adoption of new features that had not been tested by existing implementations.
The C11 standard adds numerous new features to C and the library, including type generic macros, anonymous structures, improved Unicode support, atomic operations, multi-threading, and bounds-checked functions. It also makes some portions of the existing C99 library optional, and improves compatibility with C++. The standard macro __STDC_VERSION__ is defined as 201112L to indicate that C11 support is available.
=== C17 ===
C17 is an informal name for ISO/IEC 9899:2018, a standard for the C programming language published in June 2018. It introduces no new language features, only technical corrections, and clarifications to defects in C11. The standard macro __STDC_VERSION__ is defined as 201710L to indicate that C17 support is available.
=== C23 ===
C23 is an informal name for the current major C language standard revision. It was informally known as "C2X" through most of its development. C23 was published in October 2024 as ISO/IEC 9899:2024. The standard macro __STDC_VERSION__ is defined as 202311L to indicate that C23 support is available.
=== C2Y ===
C2Y is an informal name for the next major C language standard revision, after C23 (C2X), that is hoped to be released later in the 2020s decade, hence the '2' in "C2Y". An early working draft of C2Y was released in February 2024 as N3220 by the working group ISO/IEC JTC1/SC22/WG14.
=== Embedded C ===
Historically, embedded C programming requires non-standard extensions to the C language to support exotic features such as fixed-point arithmetic, multiple distinct memory banks, and basic I/O operations.
In 2008, the C Standards Committee published a technical report extending the C language to address these issues by providing a common standard for all implementations to adhere to. It includes a number of features not available in normal C, such as fixed-point arithmetic, named address spaces, and basic I/O hardware addressing.
== Syntax ==
C has a formal grammar specified by the C standard. Line endings are generally not significant in C; however, line boundaries do have significance during the preprocessing phase. Comments may appear either between the delimiters /* and */, or (since C99) following // until the end of the line. Comments delimited by /* and */ do not nest, and these sequences of characters are not interpreted as comment delimiters if they appear inside string or character literals.
C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the type followed by the variable name. Keywords such as char and int specify built-in types. Sections of code are enclosed in braces ({ and }, sometimes called "curly brackets") to limit the scope of declarations and to act as a single statement for control structures.
As an imperative language, C uses statements to specify actions. The most common statement is an expression statement, consisting of an expression to be evaluated, followed by a semicolon; as a side effect of the evaluation, functions may be called and variables assigned new values. To modify the normal sequential execution of statements, C provides several control-flow statements identified by reserved keywords. Structured programming is supported by if ... [else] conditional execution and by do ... while, while, and for iterative execution (looping). The for statement has separate initialization, testing, and reinitialization expressions, any or all of which can be omitted. break and continue can be used within the loop. Break is used to leave the innermost enclosing loop statement and continue is used to skip to its reinitialisation. There is also a non-structured goto statement which branches directly to the designated label within the function. switch selects a case to be executed based on the value of an integer expression. Different from many other languages, control-flow will fall through to the next case unless terminated by a break.
Expressions can use a variety of built-in operators and may contain function calls. The order in which arguments to functions and operands to most operators are evaluated is unspecified. The evaluations may even be interleaved. However, all side effects (including storage to variables) will occur before the next "sequence point"; sequence points include the end of each expression statement, and the entry to and return from each function call. Sequence points also occur during evaluation of expressions containing certain operators (&&, ||, ?: and the comma operator). This permits a high degree of object code optimization by the compiler, but requires C programmers to take more care to obtain reliable results than is needed for other programming languages.
Kernighan and Ritchie say in the Introduction of The C Programming Language: "C, like any other language, has its blemishes. Some of the operators have the wrong precedence; some parts of the syntax could be better." The C standard did not attempt to correct many of these blemishes, because of the impact of such changes on already existing software.
=== Character set ===
The basic C source character set includes the following characters:
Lowercase and uppercase letters of the ISO basic Latin alphabet: a–z, A–Z
Decimal digits: 0–9
Graphic characters: ! " # % & ' ( ) * + , - . / : ; < = > ? [ \ ] ^ _ { | } ~
Whitespace characters: space, horizontal tab, vertical tab, form feed, newline
The newline character indicates the end of a text line; it need not correspond to an actual single character, although for convenience C treats it as such.
Additional multi-byte encoded characters may be used in string literals, but they are not entirely portable. Since C99 multi-national Unicode characters can be embedded portably within C source text by using \uXXXX or \UXXXXXXXX encoding (where X denotes a hexadecimal character).
The basic C execution character set contains the same characters, along with representations for alert, backspace, and carriage return. Run-time support for extended character sets has increased with each revision of the C standard.
=== Reserved words ===
The following reserved words are case sensitive.
C89 has 32 reserved words, also known as 'keywords', which cannot be used for any purposes other than those for which they are predefined:
auto
break
case
char
const
continue
default
do
double
else
enum
extern
float
for
goto
if
int
long
register
return
short
signed
sizeof
static
struct
switch
typedef
union
unsigned
void
volatile
while
C99 added five more reserved words: (‡ indicates an alternative spelling alias for a C23 keyword)
inline
restrict
_Bool ‡
_Complex
_Imaginary
C11 added seven more reserved words: (‡ indicates an alternative spelling alias for a C23 keyword)
_Alignas ‡
_Alignof ‡
_Atomic
_Generic
_Noreturn
_Static_assert ‡
_Thread_local ‡
C23 reserved fifteen more words:
alignas
alignof
bool
constexpr
false
nullptr
static_assert
thread_local
true
typeof
typeof_unqual
_BitInt
_Decimal32
_Decimal64
_Decimal128
Most of the recently reserved words begin with an underscore followed by a capital letter, because identifiers of that form were previously reserved by the C standard for use only by implementations. Since existing program source code should not have been using these identifiers, it would not be affected when C implementations started supporting these extensions to the programming language. Some standard headers do define more convenient synonyms for underscored identifiers. Some of those words were added as keywords with their conventional spelling in C23 and the corresponding macros were removed.
Prior to C89, entry was reserved as a keyword. In the second edition of their book The C Programming Language, which describes what became known as C89, Kernighan and Ritchie wrote, "The ... [keyword] entry, formerly reserved but never used, is no longer reserved." and "The stillborn entry keyword is withdrawn."
=== Operators ===
C supports a rich set of operators, which are symbols used within an expression to specify the manipulations to be performed while evaluating that expression. C has operators for:
arithmetic: +, -, *, /, %
assignment: =
augmented assignment:
bitwise logic: ~, &, |, ^
bitwise shifts: <<, >>
Boolean logic: !, &&, ||
conditional evaluation: ? :
equality testing: ==, !=
calling functions: ( )
increment and decrement: ++, --
member selection: ., ->
object size: sizeof
type: typeof, typeof_unqual since C23
order relations: <, <=, >, >=
reference and dereference: &, *, [ ]
sequencing: ,
subexpression grouping: ( )
type conversion: (typename)
C uses the operator = (used in mathematics to express equality) to indicate assignment, following the precedent of Fortran and PL/I, but unlike ALGOL and its derivatives. C uses the operator == to test for equality. The similarity between the operators for assignment and equality may result in the accidental use of one in place of the other, and in many cases the mistake does not produce an error message (although some compilers produce warnings). For example, the conditional expression if (a == b + 1) might mistakenly be written as if (a = b + 1), which will be evaluated as true unless the value of a is 0 after the assignment.
The C operator precedence is not always intuitive. For example, the operator == binds more tightly than (is executed prior to) the operators & (bitwise AND) and | (bitwise OR) in expressions such as x & 1 == 0, which must be written as (x & 1) == 0 if that is the coder's intent.
== "Hello, world" example ==
The "hello, world" example that appeared in the first edition of K&R has become the model for an introductory program in most programming textbooks. The program prints "hello, world" to the standard output, which is usually a terminal or screen display.
The original version was:
main()
{
printf("hello, world\n");
}
A standard-conforming "hello, world" program is:
include
int main(void)
{
printf("hello, world\n");
}
The first line of the program contains a preprocessing directive, indicated by #include. This causes the compiler to replace that line of code with the entire text of the stdio.h header file, which contains declarations for standard input and output functions such as printf and scanf. The angle brackets surrounding stdio.h indicate that the header file can be located using a search strategy that prefers headers provided with the compiler to other headers having the same name (as opposed to double quotes which typically include local or project-specific header files).
The second line indicates that a function named main is being defined. The main function serves a special purpose in C programs; the run-time environment calls the main function to begin program execution. The type specifier int indicates that the value returned to the invoker (in this case the run-time environment) as a result of evaluating the main function, is an integer. The keyword void as a parameter list indicates that the main function takes no arguments.
The opening curly brace indicates the beginning of the code that defines the main function.
The next line of the program is a statement that calls (i.e. diverts execution to) a function named printf, which in this case is supplied from a system library. In this call, the printf function is passed (i.e. provided with) a single argument, which is the address of the first character in the string literal "hello, world\n". The string literal is an unnamed array set up automatically by the compiler, with elements of type char and a final NULL character (ASCII value 0) marking the end of the array (to allow printf to determine the length of the string). The NULL character can also be written as the escape sequence \0. The \n is a standard escape sequence that C translates to a newline character, which, on output, signifies the end of the current line. The return value of the printf function is of type int, but it is silently discarded since it is not used. (A more careful program might test the return value to check that the printf function succeeded.) The semicolon ; terminates the statement.
The closing curly brace indicates the end of the code for the main function. According to the C99 specification and newer, the main function (unlike any other function) will implicitly return a value of 0 upon reaching the } that terminates the function. The return value of 0 is interpreted by the run-time system as an exit code indicating successful execution of the function.
== Data types ==
The type system in C is static and weakly typed, which makes it similar to the type system of ALGOL descendants such as Pascal. There are built-in types for integers of various sizes, both signed and unsigned, floating-point numbers, and enumerated types (enum). Integer type char is often used for single-byte characters. C99 added a Boolean data type. There are also derived types including arrays, pointers, records (struct), and unions (union).
C is often used in low-level systems programming where escapes from the type system may be necessary. The compiler attempts to ensure type correctness of most expressions, but the programmer can override the checks in various ways, either by using a type cast to explicitly convert a value from one type to another, or by using pointers or unions to reinterpret the underlying bits of a data object in some other way.
Some find C's declaration syntax unintuitive, particularly for function pointers. (Ritchie's idea was to declare identifiers in contexts resembling their use: "declaration reflects use".)
C's usual arithmetic conversions allow for efficient code to be generated, but can sometimes produce unexpected results. For example, a comparison of signed and unsigned integers of equal width requires a conversion of the signed value to unsigned. This can generate unexpected results if the signed value is negative.
=== Pointers ===
C supports the use of pointers, a type of reference that records the address or location of an object or function in memory. Pointers can be dereferenced to access data stored at the address pointed to, or to invoke a pointed-to function. Pointers can be manipulated using assignment or pointer arithmetic. The run-time representation of a pointer value is typically a raw memory address (perhaps augmented by an offset-within-word field), but since a pointer's type includes the type of the thing pointed to, expressions including pointers can be type-checked at compile time. Pointer arithmetic is automatically scaled by the size of the pointed-to data type.
Pointers are used for many purposes in C. Text strings are commonly manipulated using pointers into arrays of characters. Dynamic memory allocation is performed using pointers; the result of a malloc is usually cast to the data type of the data to be stored. Many data types, such as trees, are commonly implemented as dynamically allocated struct objects linked together using pointers. Pointers to other pointers are often used in multi-dimensional arrays and arrays of struct objects. Pointers to functions (function pointers) are useful for passing functions as arguments to higher-order functions (such as qsort or bsearch), in dispatch tables, or as callbacks to event handlers. Array bounds violations are therefore possible and can lead to various repercussions, including illegal memory accesses, corruption of data, buffer overruns, and run-time exceptions.
C does not have a special provision for declaring multi-dimensional arrays, but rather relies on recursion within the type system to declare arrays of arrays, which effectively accomplishes the same thing. The index values of the resulting "multi-dimensional array" can be thought of as increasing in row-major order. Multi-dimensional arrays are commonly used in numerical algorithms (mainly from applied linear algebra) to store matrices. The structure of the C array is well suited to this particular task. However, in early versions of C the bounds of the array must be known fixed values or else explicitly passed to any subroutine that requires them, and dynamically sized arrays of arrays cannot be accessed using double indexing. (A workaround for this was to allocate the array with an additional "row vector" of pointers to the columns.) C99 introduced "variable-length arrays" which address this issue.
The following example using modern C (C99 or later) shows allocation of a two-dimensional array on the heap and the use of multi-dimensional array indexing for accesses (which can use bounds-checking on many C compilers):
int func(int N, int M)
{
float (*p)[N] [M] = malloc(sizeof *p);
if (p == 0)
return -1;
for (int i = 0; i < N; i++)
for (int j = 0; j < M; j++)
(*p)[i] [j] = i + j;
print_array(N, M, p);
free(p);
return 1;
}
And here is a similar implementation using C99's Auto VLA feature:
int func(int N, int M)
{
// Caution: checks should be made to ensure N*M*sizeof(float) does NOT exceed limitations for auto VLAs and is within available size of stack.
float p[N] [M]; // auto VLA is held on the stack, and sized when the function is invoked
for (int i = 0; i < N; i++)
for (int j = 0; j < M; j++)
p[i] [j] = i + j;
print_array(N, M, p);
// no need to free(p) since it will disappear when the function exits, along with the rest of the stack frame
return 1;
}
=== Array–pointer interchangeability ===
The subscript notation x[i] (where x designates a pointer) is syntactic sugar for *(x+i). Taking advantage of the compiler's knowledge of the pointer type, the address that x + i points to is not the base address (pointed to by x) incremented by i bytes, but rather is defined to be the base address incremented by i multiplied by the size of an element that x points to. Thus, x[i] designates the i+1th element of the array.
Furthermore, in most expression contexts (a notable exception is as operand of sizeof), an expression of array type is automatically converted to a pointer to the array's first element. This implies that an array is never copied as a whole when named as an argument to a function, but rather only the address of its first element is passed. Therefore, although function calls in C use pass-by-value semantics, arrays are in effect passed by reference.
The total size of an array x can be determined by applying sizeof to an expression of array type. The size of an element can be determined by applying the operator sizeof to any dereferenced element of an array A, as in n = sizeof A[0]. Thus, the number of elements in a declared array A can be determined as sizeof A / sizeof A[0]. Note, that if only a pointer to the first element is available as it is often the case in C code because of the automatic conversion described above, the information about the full type of the array and its length are lost.
== Memory management ==
One of the most important functions of a programming language is to provide facilities for managing memory and the objects that are stored in memory. C provides three principal ways to allocate memory for objects:
There are also compilers, libraries, and operating system level mechanisms for performing actions that are not a standard part of C, such as bounds checking for arrays, detection of buffer overflow, serialization, dynamic memory tracking, and automatic garbage collection.
Memory management checking tools like Purify or Valgrind and linking with libraries containing special versions of the memory allocation functions can help uncover runtime errors in memory usage.
== Uses ==
=== Rationale for use in systems programming ===
C is widely used for systems programming in implementing operating systems and embedded system applications. This is for several reasons:
The C language permits platform hardware and memory to be accessed with pointers and type punning, so system-specific features (e.g. Control/Status Registers, I/O registers) can be configured and used with code written in C – it allows fullest control of the platform it is running on.
The code generated after compilation does not demand many system features, and can be invoked from some boot code in a straightforward manner – it is simple to execute.
The C language statements and expressions typically map well on to sequences of instructions for the target processor, and consequently there is a low run-time demand on system resources – it is fast to execute.
With its rich set of operators, the C language can use many of the features of target CPUs. Where a particular CPU has more esoteric instructions, a language variant can be constructed with perhaps intrinsic functions to exploit those instructions – it can use practically all the target CPU's features.
The language makes it easy to overlay structures onto blocks of binary data, allowing the data to be comprehended, navigated and modified – it can write data structures, even file systems.
The language supports a rich set of operators, including bit manipulation, for integer arithmetic and logic, and perhaps different sizes of floating point numbers – it can process appropriately-structured data effectively.
C is a fairly small language, with only a handful of statements, and without too many features that generate extensive target code – it is comprehensible.
C has direct control over memory allocation and deallocation, which gives reasonable efficiency and predictable timing to memory-handling operations, without any concerns for sporadic stop-the-world garbage collection events – it has predictable performance.
C permits the use and implementation of different memory allocation schemes, including a typical and ; a more sophisticated mechanism with arenas; or a version for an OS kernel that may suit DMA, use within interrupt handlers, or integrated with the virtual memory system.
Depending on the linker and environment, C code can also call libraries written in assembly language, and may be called from assembly language – it interoperates well with other lower-level code.
C and its calling conventions and linker structures are commonly used in conjunction with other high-level languages, with calls both to C and from C supported – it interoperates well with other high-level code.
C has a very mature and broad ecosystem, including libraries, frameworks, open source compilers, debuggers and utilities, and is the de facto standard. It is likely the drivers already exist in C, or that there is a similar CPU architecture as a back-end of a C compiler, so there is reduced incentive to choose another language.
===Used for computationally-intensive libraries===
C enables programmers to create efficient implementations of algorithms and data structures, because the layer of abstraction from hardware is thin, and its overhead is low, an important criterion for computationally intensive programs. For example, the GNU Multiple Precision Arithmetic Library, the GNU Scientific Library, Mathematica, and MATLAB are completely or partially written in C. Many languages support calling library functions in C, for example, the Python-based framework NumPy uses C for the high-performance and hardware-interacting aspects.
===Games===
Computer games are often built from a combination of languages. C has featured significantly, especially for those games attempting to obtain best performance from computer platforms. Examples include Doom from 1993.
===C as an intermediate language===
C is sometimes used as an intermediate language by implementations of other languages. This approach may be used for portability or convenience; by using C as an intermediate language, additional machine-specific code generators are not necessary. C has some features, such as line-number preprocessor directives and optional superfluous commas at the end of initializer lists, that support compilation of generated code. However, some of C's shortcomings have prompted the development of other C-based languages specifically designed for use as intermediate languages, such as C--. Also, contemporary major compilers GCC and LLVM both feature an intermediate representation that is not C, and those compilers support front ends for many languages including C.
===Other languages written in C===
A consequence of C's wide availability and efficiency is that compilers, libraries and interpreters of other programming languages are often implemented in C. For example, the reference implementations of Python, Perl, Ruby, and PHP are written in C.
===Once used for web development===
Historically, C was sometimes used for web development using the Common Gateway Interface (CGI) as a "gateway" for information between the web application, the server, and the browser. C may have been chosen over interpreted languages because of its speed, stability, and near-universal availability. It is no longer common practice for web development to be done in C, and many other web development languages are popular. Applications where C-based web development continues include the HTTP configuration pages on routers, IoT devices and similar, although even here some projects have parts in higher-level languages e.g. the use of Lua within OpenWRT.
===Web servers===
The two most popular web servers, Apache HTTP Server and Nginx, are both written in C. These web servers interact with the operating system, listen on TCP ports for HTTP requests, and then serve up static web content, or cause the execution of other languages handling to 'render' content such as PHP, which is itself primarily written in C. C's close-to-the-metal approach allows for the construction of these high-performance software systems.
===End-user applications===
C has also been widely used to implement end-user applications. However, such applications can also be written in newer, higher-level languages.
==Limitations==
While C has been popular, influential and hugely successful, it has drawbacks, including:
The standard dynamic memory handling with malloc and free is error prone. Improper use can lead to memory leaks and dangling pointers.
The use of pointers and the direct manipulation of memory means corruption of memory is possible, perhaps due to programmer error, or insufficient checking of bad data.
There is some type checking, but it does not apply to areas like variadic functions, and the type checking can be trivially or inadvertently circumvented. It is weakly typed.
Since the code generated by the compiler contains few checks itself, there is a burden on the programmer to consider all possible outcomes, to protect against buffer overruns, array bounds checking, stack overflows, memory exhaustion, and consider race conditions, thread isolation, etc.
The use of pointers and the run-time manipulation of these means there may be two ways to access the same data (aliasing), which is not determinable at compile time. This means that some optimisations that may be available to other languages are not possible in C. FORTRAN is considered faster.
Some of the standard library functions, e.g. scanf or , can lead to buffer overruns.
There is limited standardisation in support for low-level variants in generated code, for example: different function calling conventions and ABI; different structure packing conventions; different byte ordering within larger integers (including endianness). In many language implementations, some of these options may be handled with the preprocessor directive #pragma, and some with additional keywords e.g. use __cdecl calling convention. The directive and options are not consistently supported.
String handling using the standard library is code-intensive, with explicit memory management required.
The language does not directly support object orientation, introspection, run-time expression evaluation, generics, etc.
There are few guards against inappropriate use of language features, which may lead to unmaintainable code. In particular, the C preprocessor can hide troubling effects such as double evaluation and worse. This facility for tricky code has been celebrated with competitions such as the International Obfuscated C Code Contest and the Underhanded C Contest.
C lacks standard support for exception handling and only offers return codes for error checking. The setjmp and longjmp standard library functions have been used to implement a try-catch mechanism via macros.
For some purposes, restricted styles of C have been adopted, e.g. MISRA C or CERT C, in an attempt to reduce the opportunity for bugs. Databases such as CWE attempt to count the ways C etc. has vulnerabilities, along with recommendations for mitigation.
There are tools that can mitigate against some of the drawbacks. Contemporary C compilers include checks which may generate warnings to help identify many potential bugs.
== Related languages ==
C has both directly and indirectly influenced many later languages such as C++ and Java. The most pervasive influence has been syntactical; all of the languages mentioned combine the statement and (more or less recognizably) expression syntax of C with type systems, data models or large-scale program structures that differ from those of C, sometimes radically.
Several C or near-C interpreters exist, including Ch and CINT, which can also be used for scripting.
When object-oriented programming languages became popular, C++ and Objective-C were two different extensions of C that provided object-oriented capabilities. Both languages were originally implemented as source-to-source compilers; source code was translated into C, and then compiled with a C compiler.
The C++ programming language (originally named "C with Classes") was devised by Bjarne Stroustrup as an approach to providing object-oriented functionality with a C-like syntax. C++ adds greater typing strength, scoping, and other tools useful in object-oriented programming, and permits generic programming via templates. Nearly a superset of C, C++ now supports most of C, with a few exceptions.
Objective-C was originally a very "thin" layer on top of C, and remains a strict superset of C that permits object-oriented programming using a hybrid dynamic/static typing paradigm. Objective-C derives its syntax from both C and Smalltalk: syntax that involves preprocessing, expressions, function declarations, and function calls is inherited from C, while the syntax for object-oriented features was originally taken from Smalltalk.
In addition to C++ and Objective-C, Ch, Cilk, and Unified Parallel C are nearly supersets of C.
|
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"Dr. Dobbs",
"Master Control Program",
"general-purpose programming language",
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"For loop",
"Run time (program lifecycle phase)",
"Brian Kernighan",
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"?:",
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"compiler",
"Automatic memory allocation",
"higher-order function",
"web development",
"C dynamic memory allocation",
"Verilog",
"Macro (computer science)",
"Research Unix",
"Double-precision floating-point format",
"SystemVerilog",
"mainframe computer",
"lint (software)",
"function prototype",
"Type checking",
"Association for Computing Machinery",
"bitwise shift",
"C11 (C standard revision)",
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"static type system",
"machine instructions",
"JS++",
"Ch (computer programming)",
"long int",
"executable code",
"compiled",
"Setjmp.h",
"Common Weakness Enumeration",
"bitwise logic",
"Space (punctuation)",
"Dynamic memory allocation",
"Computing platform",
"Order of operations",
"technical report",
"O'Reilly Media",
"bsearch",
"object code",
"Perl",
"Python (programming language)",
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"carriage return",
"pass-by-value",
"Alan Snyder (computer scientist)",
"functional programming",
"form feed",
"const",
"source-to-source compiler",
"syntactic sugar",
"dispatch table",
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"Bjarne Stroustrup",
"Common Gateway Interface",
"restrict",
"Runtime system",
"case sensitive",
"Statement (computer science)",
"Expression (computer science)",
"FORTRAN",
"International Obfuscated C Code Contest",
"application software",
"type conversion",
"Kernel (operating system)",
"American National Standards Institute",
"superset",
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" cdecl",
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"Split-C",
"wild pointer",
"assembly language",
"Variable length array",
"virtual memory",
"calling convention",
"Swift (programming language)",
"List of C compilers",
"Procedural programming",
"Unicode",
"Burroughs large systems",
"type introspection",
"Lowest common denominator (computers)",
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"memory leak",
"Addition",
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"structured programming",
"reference implementation",
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"Call stack",
"conditional compilation",
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"string literal",
"Label (computer science)",
"IBM Rational Purify",
"Solaris Studio",
"Seed7",
"stop-the-world",
"Locale (computer software)",
"Wired (magazine)",
"Underhanded C Contest",
"Mike Lesk",
"Version 2 Unix",
"variadic macro",
"Software maintenance",
"Modulo operation",
"record (computer science)",
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"C preprocessor",
"The C Programming Language",
"library routine",
"JavaScript",
"Cross-platform",
"endianness",
"lexical variable scope",
"Volatile variable",
"Englewood Cliffs, NJ",
"complex number",
"Memory management",
"linear algebra",
"Escape sequences in C",
"Prentice Hall",
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"horizontal tab",
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"ALGOL",
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"automatic garbage collection",
"multi-dimensional array",
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"Computer memory",
"Valgrind",
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"callbacks",
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"embedded programming",
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"intermediate representation",
"backspace",
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"memory bank",
"Assignment (computer science)",
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"Static typing",
"Limbo (programming language)",
"microcomputer",
"Memory address",
"IEEE",
"String literal",
"HTTP",
"Block (programming)",
"null pointer",
"intermediate language",
"data type",
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"qsort",
"Multiplication",
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"Equality (mathematics)",
"exception handling",
"typedef",
"GUI",
"Nim (programming language)"
] |
6,023 |
Castle of the Winds
|
Castle of the Winds is a tile-based roguelike video game for Microsoft Windows. It was developed by Rick Saada in 1989 and distributed by Epic MegaGames in 1993. The game was released around 1998 as a freeware download by the author. Though it is secondary to its hack and slash gameplay, Castle of the Winds has a plot loosely based on Norse mythology, told with setting changes, unique items, and occasional passages of text. The game is composed of two parts: A Question of Vengeance, released as shareware, and Lifthransir's Bane, sold commercially. A combined license for both parts was also sold.
==Gameplay==
The game differs from most roguelikes in a number of ways. Its interface is mouse-dependent, but supports keyboard shortcuts (such as 'g' to get an item). Castle of the Winds also allows the player to restore saved games after dying.
The game favors the use of magic in combat, as spells are the only weapons that work from a distance. The player character automatically gains a spell with each experience level, and can permanently gain others using corresponding books, until all thirty spells available are learned. There are two opposing pairs of elements: cold vs. fire and lightning vs. acid/poison. Spells are divided into six categories: attack, defense, healing, movement, divination, and miscellaneous.
Castle of the Winds possesses an inventory system that limits a player's load based on weight and bulk, rather than by number of items. It allows the character to use different containers, including packs, belts, chests, and bags. Other items include weapons, armor, protective clothing, purses, and ornamental jewellery. Almost every item in the game can be normal, cursed, or enchanted, with curses and enchantments working in a manner similar to NetHack. Although items do not break with use, they may already be broken or rusted when found. Most objects that the character currently carries can be renamed.
Wherever the player goes before entering the dungeon, there is always a town which offers the basic services of a temple for healing and curing curses, a junk store where anything can be sold for a few copper coins, a sage who can identify items and (from the second town onwards) a bank for storing the total capacity of coins to lighten the player's load. Other services that differ and vary in what they sell are outfitters, weaponsmiths, armoursmiths, magic shops and general stores.
The game tracks how much time has been spent playing the game. Although story events are not triggered by the passage of time, it does determine when merchants rotate their stock. Victorious players are listed as "Valhalla's Champions" in the order of time taken, from fastest to slowest. If the player dies, they are still put on the list, but are categorized as "Dead", with their experience point total listed as at the final killing blow. The amount of time spent also determines the difficulty of the last boss.
==Plot==
The player begins in a tiny hamlet, near which they used to live. Their farm has been destroyed and godparents killed. After clearing out an abandoned mine, the player finds a scrap of parchment that reveals the death of the player's godparents was ordered by an unknown enemy. The player then returns to the hamlet to find it pillaged, and decides to travel to Bjarnarhaven.
Once in Bjarnarhaven, the player explores the levels beneath a nearby fortress, eventually facing Hrungnir, the Hill Giant Lord, responsible for ordering the player's godparents' death. Hrungnir carries the Enchanted Amulet of Kings. Upon activating the amulet, the player is informed of their past by their dead father, after which the player is transported to the town of Crossroads, and Part I ends. The game can be imported or started over in Part II.
The town of Crossroads is run by a Jarl who at first does not admit the player, but later (on up to three occasions) provides advice and rewards. The player then enters the nearby ruined titular Castle of the Winds. There the player meets his/her deceased grandfather, who instructs them to venture into the dungeons below, defeat Surtur, and reclaim their birthright. Venturing deeper, the player encounters monsters run rampant, a desecrated crypt, a necromancer, and the installation of various special rooms for elementals. The player eventually meets and defeats the Wolf-Man leader, Bear-Man leader, the four Jotun kings, a Demon Lord, and finally Surtur. Upon defeating Surtur and escaping the dungeons, the player sits upon the throne, completing the game.
==Development==
Inspired by his love of RPGs and while learning Windows programming in the 80s, Rick Saada designed and completed Castle of the Winds. The game sold 13,500 copies. By 1998, the game's author, Rick Saada, decided to distribute the entirety of Castle of the Winds free of charge.
|
[
"roguelike",
"Jötunn",
"Computer Gaming World",
"Single-player",
"hack and slash",
"Experience point",
"farm",
"shareware",
"Norse mythology",
"Commercial software",
"Roguelike",
"Gamasutra",
"Epic Games",
"Microsoft Windows",
"hamlet (place)",
"Windows 3.x",
"Tile-based game",
"NetHack",
"freeware",
"godparent",
"Rick Saada",
"player character",
"G4 (U.S. TV channel)",
"Valhalla",
"Epic MegaGames"
] |
6,024 |
Reformed Christianity
|
Reformed Christianity, also called Calvinism, is a major branch of Protestantism that began during the 16th-century Protestant Reformation. In the modern day, it is largely represented by the Continental Reformed, Presbyterian, and Congregational traditions, as well as parts of the Baptist and Anglican (known as "Episcopal" in some regions) traditions.
Reformed theology emphasizes the authority of the Bible and the sovereignty of God, as well as covenant theology, a framework for understanding the Bible based on God's covenants with people. Reformed churches have emphasized simplicity in worship. Several forms of ecclesiastical polity are exercised by Reformed churches, including presbyterian, congregational, and some episcopal. Articulated by John Calvin, the Reformed faith holds to a spiritual (pneumatic) presence of Christ in the Lord's Supper.
Emerging in the 16th century, the Reformed tradition developed over several generations, especially in Switzerland, Scotland and the Netherlands. In the 17th century, Jacobus Arminius and the Remonstrants were expelled from the Dutch Reformed Church over disputes regarding predestination and salvation, and from that time Arminians are usually considered to be a distinct tradition from the Reformed. This dispute produced the Canons of Dort, the basis for the "doctrines of grace" also known as the "five points" of Calvinism.
==Definition and terminology==
Reformed Christianity is often called Calvinism after John Calvin (born Jehan Cauvin), influential reformer of Geneva. The term was first used by opposing Lutherans in the 1550s. Calvin did not approve of the use of this term, and scholars have argued its use is misleading, inaccurate, unhelpful, and "inherently distortive."
The definitions and boundaries of the terms Reformed Christianity and Calvinism are contested by scholars. As a historical movement, Reformed Christianity began during the Reformation with Huldrych Zwingli in Zürich, Switzerland. Following the failure of the Marburg Colloquy between Zwingli's followers and those of Martin Luther in 1529 to mediate disputes regarding the real presence of Christ in the Lord's Supper, Reformed Protestants were defined by their opposition to Lutherans. The Reformed also opposed Anabaptist radicals thus remaining within the Magisterial Reformation. During the 17th-century Arminian Controversy, followers of Jacobus Arminius were forcibly removed from the Dutch Reformed Church for their views regarding predestination and salvation, and thenceforth Arminians would be considered outside the pale of Reformed orthodoxy, though some use the term Reformed to include Arminians while using the term Calvinist to exclude Arminians.
Reformed Christianity also has a complicated relationship with Anglicanism, the branch of Christianity originating in the Church of England. The Anglican confessions are considered Protestant, and more specifically, Reformed, and leaders of the English Reformation were influenced by Calvinist rather than Lutheran theologians. Still the Church of England retained elements of Catholicism such as bishops and vestments, unlike continental Reformed churches, and thus was sometimes called "but halfly Reformed." Beginning in the 17th century, Anglicanism broadened to the extent that Reformed theology is no longer dominant in Anglicanism.
Some scholars argue that Reformed Baptists, who hold many of the same beliefs as Reformed Christians but not infant baptism, should be considered part of Reformed Christianity, though this would not have been the view of early modern Reformed theologians. Others disagree, asserting that Baptists should be considered a separate religious tradition.
== History ==
The first wave of Reformed theologians included Zwingli, Martin Bucer, Wolfgang Capito, John Oecolampadius, and Guillaume Farel. While from diverse academic backgrounds, their work already contained key themes within Reformed theology, especially the priority of scripture as a source of authority. Scripture was also viewed as a unified whole, which led to a covenantal theology of the sacraments of baptism and the Lord's Supper as visible signs of the covenant of grace. Another shared perspective was their denial of the real presence of Christ in the Eucharist. Each understood salvation to be by grace alone and affirmed a doctrine of unconditional election, the teaching that some people are chosen by God to be saved. Luther and his successor Philipp Melanchthon were significant influences on these theologians and, to a larger extent, those who followed. The doctrine of justification by faith alone, also known as sola fide, was a direct inheritance from Luther.
The second generation featured John Calvin, Heinrich Bullinger, Thomas Cranmer, Wolfgang Musculus, Peter Martyr Vermigli, Andreas Hyperius and John à Lasco. Written between 1536 and 1539, Calvin's Institutes of the Christian Religion was one of the most influential works of the era. Toward the middle of the 16th century, these beliefs were formed into one consistent creed which would shape the future definition of the Reformed faith. The 1549 Consensus Tigurinus unified Zwingli and Bullinger's memorialist theology of the Eucharist, which taught that it was simply a reminder of Christ's death, with Calvin's view of it as a means of grace with Christ actually present, though spiritually rather than bodily as in Catholic doctrine. The document demonstrates the diversity as well as unity in early Reformed theology, giving it a stability that enabled it to spread rapidly throughout Europe. This stands in marked contrast to the bitter controversy experienced by Lutherans prior to the 1579 Formula of Concord.
Through Calvin's missionary work in France, his program of reform eventually reached the French-speaking provinces of the Netherlands. Calvinism was adopted in the Electorate of the Palatinate under Frederick III, which led to the formulation of the Heidelberg Catechism in 1563. This and the Belgic Confession were adopted as confessional standards in the first synod of the Dutch Reformed Church in 1571.
In 1573 William the Silent joined the Calvinist Church. Calvinism was declared the official religion of the Kingdom of Navarre by the queen regnant Jeanne d'Albret after her conversion in 1560. Leading divines, either Calvinist or those sympathetic to Calvinism, settled in England, including Bucer, Martyr, and John Łaski, as did John Knox in Scotland. During the First English Civil War, English and Scots Presbyterians produced the Westminster Confession, which became the confessional standard for Presbyterians in the English-speaking world. Having established itself in Europe, the movement continued to spread to areas including North America, South Africa and Korea. While Calvin did not live to see the foundation of his work grow into an international movement, his death allowed his ideas to spread far beyond their city of origin and their borders and to establish their own distinct character.
=== Spread ===
Although much of Calvin's work was in Geneva, his publications spread his ideas of a correctly Reformed church to many parts of Europe. In Switzerland, some cantons are still Reformed, and some are Catholic. Calvinism became the dominant doctrine within the Church of Scotland, the Dutch Republic, some communities in Flanders, and parts of Germany, especially those adjacent to the Netherlands in the Palatinate, Kassel, and Lippe, spread by Caspar Olevian and Zacharias Ursinus among others. Protected by the local nobility, Calvinism became a significant religion in eastern Hungary and Hungarian-speaking areas of Transylvania. there are about 3.5 million Hungarian Reformed people worldwide.
Calvinism was influential in France, Lithuania, and Poland before being mostly erased during the Counter-Reformation. One of the most important Polish reformed theologists was Łaski, who was also involved into organising churches in East Frisia and Stranger's Church in London. Later, a faction called the Polish Brethren broke away from Calvinism on January 22, 1556, when Piotr of Goniądz, a Polish student, spoke out against the doctrine of the Trinity during the general synod of the Reformed churches of Poland held in the village of Secemin. Calvinism gained some popularity in Scandinavia, especially Sweden, but was rejected in favor of Lutheranism after the Synod of Uppsala in 1593.
Many 17th century European settlers in the Thirteen Colonies in British America were Calvinists, who emigrated because of arguments over church structure, including the Pilgrim Fathers. Others were forced into exile, including the French Huguenots. Dutch and French Calvinist settlers were also among the first European colonizers of South Africa, beginning in the 17th century, who became known as Boers or Afrikaners.
Sierra Leone was largely colonized by Calvinist settlers from Nova Scotia, many of whom were Black Loyalists who fought for the British Empire during the American War of Independence. John Marrant had organized a congregation there under the auspices of the Huntingdon Connection. Some of the largest Calvinist communions were started by 19th- and 20th-century missionaries. Especially large are those in Indonesia, Korea and Nigeria. In South Korea there are 20,000 Presbyterian congregations with about 9–10 million church members, scattered in more than 100 Presbyterian denominations. In South Korea, Presbyterianism is the largest Christian denomination.
== Demography==
A 2011 report of the Pew Forum on Religious and Public Life estimates that members of Presbyterian or Reformed churches make up 7% of the estimated 801 million Protestants globally, or approximately 56 million people.
Though the broadly defined Reformed faith is much larger, as it constitutes Congregationalist (0.5%), most of the United and uniting churches (unions of different denominations) (7.2%) and most likely some of the other Protestant denominations (38.2%). All three are distinct categories from Presbyterian or Reformed (7%) in this report. The Reformed family of churches is one of the largest Christian denominations, representing 75 million believers worldwide.
According to Global Christianity: A Guide to the World's Largest Religion from Afghanistan to Zimbabwe, in 2020, Presbyterian and Reformed Christians numbered around 65,446,000 people, or 0.8% of the world's population. Congregationalists were listed at 4,986,000, with 0.1% of the world's population. Therefore, the three branches of Reformed Christianity totaled 70,432,000 people, or 0.9% of the global population.
== World Communions==
The World Communion of Reformed Churches (WCRC), which includes some United Churches, has 80 million believers. WCRC is the fourth largest Christian communion in the world, after the Roman Catholic Church, the Eastern Orthodox Churches, and the Anglican Communion. Reformed theologians emphasize that this sinfulness affects all of a person's nature, including their will. This view, that sin so dominates people that they are unable to avoid sin, has been called total depravity. As a consequence, every one of their descendants inherited a stain of corruption and depravity. This condition, innate to all humans, is known in Christian theology as original sin.
Calvin thought original sin was "a hereditary corruption and depravity of our nature, extending to all the parts of the soul." Calvin asserted people were so warped by original sin that "everything which our mind conceives, meditates, plans, and resolves, is always evil." The depraved condition of every human being is not the result of sins people commit during their lives. Instead, before we are born, while we are in our mother's womb, "we are in God's sight defiled and polluted." Calvin thought people were justly condemned to hell because their corrupted state is "naturally hateful to God."
In colloquial English, the term "total depravity" can be easily misunderstood to mean that people are absent of any goodness or unable to do any good. However the Reformed teaching is actually that while people continue to bear God's image and may do things that appear outwardly good, their sinful intentions affect all of their nature and actions so that they are not pleasing to God.
Justification is the part of salvation where God pardons the sin of those who believe in Christ. It is historically held by Protestants to be the most important article of Christian faith, though more recently it is sometimes given less importance out of ecumenical concerns. People are not on their own able to fully repent of their sin or prepare themselves to repent because of their sinfulness. Therefore, justification is held to arise solely from God's free and gracious act.
Sanctification is the part of salvation in which God makes believers holy, by enabling them to exercise greater love for God and for other people. The good works accomplished by believers as they are sanctified are considered to be the necessary outworking of the believer's salvation, though they do not cause the believer to be saved. Sanctification, like justification, is by faith, because doing good works is simply living as the child of God one has become.
=== Predestination ===
Stemming from the theology of John Calvin, Reformed theologians teach that sin so affects human nature that they are unable even to exercise faith in Christ by their own will. While people are said to retain free will, in that they willfully sin, they are unable not to sin because of the corruption of their nature due to original sin. Reformed Christians believe that God predestined some people to be saved and others were predestined to eternal damnation. This choice by God to save some is held to be unconditional and not based on any characteristic or action on the part of the person chosen. The Calvinist view is opposed to the Arminian view that God's choice of whom to save is conditional or based on his foreknowledge of who would respond positively to God.
Karl Barth reinterpreted the doctrine of predestination to apply only to Christ. Individual people are only said to be elected through their being in Christ. Reformed theologians who followed Barth, including Jürgen Moltmann, David Migliore, and Shirley Guthrie, have argued that the traditional Reformed concept of predestination is speculative and have proposed alternative models. These theologians claim that a properly trinitarian doctrine emphasizes God's freedom to love all people, rather than choosing some for salvation and others for damnation. God's justice towards and condemnation of sinful people is spoken of by these theologians as out of his love for them and a desire to reconcile them to himself.
==== Five Points of Calvinism ====
Much attention surrounding Calvinism focuses on the "Five Points of Calvinism" (also called the doctrines of grace). The five points have been summarized under the acrostic TULIP. The five points are popularly said to summarize the Canons of Dort; however, there is no historical relationship between them, and some scholars argue that their language distorts the meaning of the Canons, Calvin's theology, and the theology of 17th-century Calvinistic orthodoxy, particularly in the language of total depravity and limited atonement. The five points were more recently popularized in the 1963 booklet The Five Points of Calvinism Defined, Defended, Documented by David N. Steele and Curtis C. Thomas. The origins of the five points and the acrostic are uncertain, but they appear to be outlined in the Counter Remonstrance of 1611, a lesser-known Reformed reply to the Arminians, which was written prior to the Canons of Dort. The acrostic was used by Cleland Boyd McAfee as early as circa 1905. An early printed appearance of the acrostic can be found in Loraine Boettner's 1932 book, The Reformed Doctrine of Predestination.
=== Church ===
Reformed Christians see the Christian Church as the community with which God has made the covenant of grace, a promise of eternal life and relationship with God. This covenant extends to those under the "old covenant" whom God chose, beginning with Abraham and Sarah. The church is conceived of as both invisible and visible. The invisible church is the body of all believers, known only to God. The visible church is the institutional body which contains both members of the invisible church as well as those who appear to have faith in Christ, but are not truly part of God's elect.
In order to identify the visible church, Reformed theologians have spoken of certain marks of the Church. For some, the only mark is the pure preaching of the gospel of Christ. Others, including John Calvin, also include the right administration of the sacraments. Others, such as those following the Scots Confession, include a third mark of rightly administered church discipline, or exercise of censure against unrepentant sinners. These marks allowed the Reformed to identify the church based on its conformity to the Bible rather than the magisterium or church tradition.
=== Worship ===
==== Regulative principle of worship ====
The regulative principle of worship is a teaching shared by some Calvinists and Anabaptists on how the Bible orders public worship. The substance of the doctrine regarding worship is that God institutes in the Scriptures everything he requires for worship in the Church and that everything else is prohibited. As the regulative principle is reflected in Calvin's own thought, it is driven by his evident antipathy toward the Roman Catholic Church and its worship practices, and it associates musical instruments with icons, which he considered violations of the Ten Commandments' prohibition of graven images.
On this basis, many early Calvinists also eschewed musical instruments and advocated a cappella exclusive psalmody in worship, though Calvin himself allowed other scriptural songs as well as psalms,
Since the 19th century, however, some of the Reformed churches have modified their understanding of the regulative principle and make use of musical instruments, believing that Calvin and his early followers went beyond the biblical requirements
=== Sacraments ===
The Westminster Confession of Faith limits the sacraments to baptism and the Lord's Supper. Sacraments are denoted "signs and seals of the covenant of grace." Westminster speaks of "a sacramental relation, or a sacramental union, between the sign and the thing signified; whence it comes to pass that the names and effects of the one are attributed to the other." Baptism is for infant children of believers as well as believers, as it is for all the Reformed except Baptists and some Congregationalists. Baptism admits the baptized into the visible church, and in it all the benefits of Christ are offered to the baptized. On the Lord's supper, the Westminster Confession takes a position between Lutheran sacramental union and Zwinglian memorialism: "the Lord's supper really and indeed, yet not carnally and corporally, but spiritually, receive and feed upon Christ crucified, and all benefits of his death: the body and blood of Christ being then not corporally or carnally in, with, or under the bread and wine; yet, as really, but spiritually, present to the faith of believers in that ordinance as the elements themselves are to their outward senses."
The 1689 London Baptist Confession of Faith does not use the term sacrament, but describes baptism and the Lord's supper as ordinances, as do most Baptists, Calvinist or otherwise. Baptism is only for those who "actually profess repentance towards God", and not for the children of believers. Baptists also insist on immersion or dipping, in contradistinction to other Reformed Christians. The Baptist Confession describes the Lord's supper as "the body and blood of Christ being then not corporally or carnally, but spiritually present to the faith of believers in that ordinance", similarly to the Westminster Confession. There is significant latitude in Baptist congregations regarding the Lord's supper, and many hold the Zwinglian view.
=== Logical order of God's decree ===
There are two schools of thought regarding the logical order of God's decree to ordain the fall of man: supralapsarianism (from the Latin: , "above", here meaning "before" + , "fall") and infralapsarianism (from the Latin: , "beneath", here meaning "after" + , "fall"). The former view, sometimes called "high Calvinism", argues that the Fall occurred partly to facilitate God's purpose to choose some individuals for salvation and some for damnation. Infralapsarianism, sometimes called "low Calvinism", is the position that, while the Fall was indeed planned, it was not planned with reference to who would be saved.
Supralapsarianism is based on the belief that God chose which individuals to save logically prior to the decision to allow the race to fall and that the Fall serves as the means of realization of that prior decision to send some individuals to hell and others to heaven (that is, it provides the grounds of condemnation in the reprobate and the need for salvation in the elect). In contrast, infralapsarians hold that God planned the race to fall logically prior to the decision to save or damn any individuals because, it is argued, in order to be "saved", one must first need to be saved from something and therefore the decree of the Fall must precede predestination to salvation or damnation.
These two views vied with each other at the Synod of Dort, an international body representing Calvinist Christian churches from around Europe, and the judgments that came out of that council sided with infralapsarianism (Canons of Dort, First Point of Doctrine, Article 7). The Westminster Confession of Faith also teaches (in Hodge's words "clearly impl[ies]") the infralapsarian view, but is sensitive to those holding to supralapsarianism. The Lapsarian controversy has a few vocal proponents on each side today, but overall it does not receive much attention among modern Calvinists.
== Branches ==
The Reformed tradition is historically represented by the Continental, Presbyterian, Reformed Anglican, Congregationalist, and Reformed Baptist denominational families.
Reformed churches practice several forms of church government, primarily presbyterian and congregational, but some adhere to episcopal polity. The largest interdenominational association is the World Communion of Reformed Churches with more than 100 million members in 211 member denominations around the world. Smaller, conservative Reformed associations include the World Reformed Fellowship and the International Conference of Reformed Churches.
=== Continental ===
"Continental" Reformed churches originate in continental Europe, a term used by English speakers to distinguish them from traditions from the British Isles. Many uphold the Helvetic Confessions and Heidelberg Catechism, which were adopted in Zurich and Heidelberg, respectively. In the United States, immigrants belonging to the continental Reformed churches joined the Dutch Reformed Church there, as well as the Anglican Church.
=== Presbyterian ===
Presbyterian churches are named for their order of government by assemblies of elders, or presbyters. They are especially influenced by John Knox, who brought Reformed theology and polity to the Church of Scotland after spending time on the continent in Calvin's Geneva. Presbyterians historically uphold the Westminster Confession of Faith.
=== Congregational ===
Congregationalism originates in Puritanism, a sixteenth-century movement to reform the Church of England. Unlike the Presbyterians, Congregationalists consider the local church to be rightfully self-ruled by their own officers, not higher ecclesiastical courts. The Savoy Declaration, a revision of Westminster, is the primary confession of historic Congregationalism. Evangelical Congregationalists are internationally represented by the World Evangelical Congregational Fellowship. Christian denominations in the Congregationalist tradition include the United Church of Christ, the National Association of Congregational Christian Churches and the Conservative Congregational Christian Conference in the United States, Evangelical Congregational Church in Argentina and Evangelical Fellowship of Congregational Churches in the United Kingdom, among others.
=== Anglican ===
Though Anglicanism today is often described as a separate branch from the Reformed, historic Anglicanism is a part of the wider Reformed tradition. The foundational documents of the Anglican church "express a theology in keeping with the Reformed theology of the Swiss and South German Reformation." The Most Rev. Peter Robinson, presiding bishop of the United Episcopal Church of North America, writes:}}
=== Baptist ===
Reformed or Calvinistic Baptists, unlike other Reformed traditions, exclusively practice believer's baptism. They observe congregational polity like the Congregationalists. Their primary confession is the 1689 Baptist Confession of Faith, a revision of the Savoy Declaration of the Congregationalist Church, but other Baptist Confessions are also used. Not all Baptists are Reformed. Some Reformed Baptists accept Reformed theology, especially soteriology, but do not hold to a specific confession or to covenant theology.
== Variants in Reformed theology ==
=== Amyraldism ===
Amyraldism (or sometimes Amyraldianism, also known as the School of Saumur, hypothetical universalism, post redemptionism, moderate Calvinism, or four-point Calvinism) is the belief that God, prior to his decree of election, decreed Christ's atonement for all alike if they believe, but seeing that none would believe on their own, he then elected those whom he will bring to faith in Christ, thereby preserving the Calvinist doctrine of unconditional election. The efficacy of the atonement remains limited to those who believe.
Named after its formulator Moses Amyraut, this doctrine is still viewed as a variety of Calvinism in that it maintains the particularity of sovereign grace in the application of the atonement. However, detractors like B. B. Warfield have termed it "an inconsistent and therefore unstable form of Calvinism."
=== Hyper-Calvinism ===
Hyper-Calvinism is the belief that emphasizes God's sovereignty in election and salvation to such an extent that it rejects the responsibility of all people to "repent and believe" the gospel. This belief system became prominent among some of the early English Particular Baptists in the 18th century. Historically, it has been associated with theologians such as John Gill and Joseph Hussey who contributed to the development of its distinct views. This variant of Reformed Theology was opposed by ministers such as Andrew Fuller and missionaries such as William Carey who argued against the Hyper-Calvinistic mindset that "if God wants to save the heathen, He will do it without your help or mine."
The Westminster Confession of Faith says that the gospel is to be freely offered to sinners, and the Larger Catechism makes clear that the gospel is offered to the non-elect.
The term is also used as a pejorative and occasionally appears in both theological and secular controversial contexts. It usually connotes a negative opinion about some variety of theological determinism, predestination, or a version of Evangelical Christianity or Calvinism that is deemed by the critic to be unenlightened, harsh, or extreme.
=== Neo-Calvinism ===
Beginning in the 1880s, Neo-Calvinism, a form of Dutch Calvinism, is the movement initiated by the theologian and later Dutch prime minister Abraham Kuyper. James Bratt has identified a number of different types of Dutch Calvinism: The Seceders—split into the Reformed Church "West" and the Confessionalists; and the Neo-Calvinists—the Positives and the Antithetical Calvinists. The Seceders were largely infralapsarian and the Neo-Calvinists usually supralapsarian.
Kuyper wanted to awaken the church from what he viewed as its pietistic slumber. He declared:
No single piece of our mental world is to be sealed off from the rest and there is not a square inch in the whole domain of human existence over which Christ, who is sovereign over all, does not cry: 'Mine!'
This refrain has become something of a rallying call for Neo-Calvinists.
=== Christian Reconstructionism ===
Christian Reconstructionism is a fundamentalist Calvinist theonomic movement that has remained rather obscure. Founded by R. J. Rushdoony, the movement has had an important influence on the Christian Right in the United States. The movement peaked in the 1990s. However, it lives on in small denominations such as the Reformed Presbyterian Church in the United States and as a minority position in other denominations. Christian Reconstructionists are usually postmillennialists and followers of the presuppositional apologetics of Cornelius Van Til. They tend to support a decentralized political order resulting in laissez-faire capitalism.
=== New Calvinism ===
New Calvinism is a growing perspective within conservative Evangelicalism that embraces the fundamentals of 16th century Calvinism while also trying to be relevant in the present day world. In March 2009, Time magazine described the New Calvinism as one of the "10 ideas changing the world". Some of the major figures who have been associated with the New Calvinism are John Piper, C. J. Mahaney, and Tim Keller. New Calvinists have been criticized for blending Calvinist soteriology with popular Evangelical positions on the sacraments and continuationism and for rejecting tenets seen as crucial to the Reformed faith such as confessionalism and covenant theology.
==Social and economic influences==
Calvin expressed himself on usury in a 1545 letter to a friend, Claude de Sachin, in which he criticized the use of certain passages of scripture invoked by people opposed to the charging of interest. He reinterpreted some of these passages, and suggested that others of them had been rendered irrelevant by changed conditions. He also dismissed the argument (based upon the writings of Aristotle) that it is wrong to charge interest for money because money itself is barren. He said that the walls and the roof of a house are barren, too, but it is permissible to charge someone for allowing him to use them. In the same way, money can be made fruitful.
He qualified his view, however, by saying that money should be lent to people in dire need without hope of interest, while a modest interest rate of 5% should be permitted in relation to other borrowers.
In The Protestant Ethic and the Spirit of Capitalism, Max Weber wrote that capitalism in Northern Europe evolved when the Protestant (particularly Calvinist) ethic influenced large numbers of people to engage in work in the secular world, developing their own enterprises and engaging in trade and the accumulation of wealth for investment. In other words, the Protestant work ethic was an important force behind the unplanned and uncoordinated emergence of modern capitalism.
Expert researchers and authors have referred to the United States as a "Protestant nation" or "founded on Protestant principles," specifically emphasizing its Calvinist heritage.
==Politics and society==
Calvin's concepts of God and man led to ideas which were gradually put into practice after his death, in particular in the fields of politics and society. After their fight for independence from Spain (1579), the Netherlands, under Calvinist leadership, granted asylum to religious minorities, including French Huguenots, English Independents (Congregationalists), and Jews from Spain and Portugal. The ancestors of the philosopher Baruch Spinoza were Portuguese Jews. Aware of the trial against Galileo, René Descartes lived in the Netherlands, out of reach of the Inquisition, from 1628 to 1649. Pierre Bayle, a Reformed Frenchman, also felt safer in the Netherlands than in his home country. He was the first prominent philosopher who demanded tolerance for atheists. Hugo Grotius (1583–1645) was able to publish a rather liberal interpretation of the Bible and his ideas about natural law in the Netherlands. Moreover, the Calvinist Dutch authorities allowed the printing of books that could not be published elsewhere, such as Galileo's Discorsi (1638).
Alongside the liberal development of the Netherlands came the rise of modern democracy in England and North America. In the Middle Ages, state and church had been closely connected. Martin Luther's doctrine of the two kingdoms separated state and church in principle. His doctrine of the priesthood of all believers raised the laity to the same level as the clergy. Going one step further, Calvin included elected laymen (church elders, presbyters) in his concept of church government. The Huguenots added synods whose members were also elected by the congregations. The other Reformed churches took over this system of church self-government, which was essentially a representative democracy. Baptists, Quakers, and Methodists are organized in a similar way. These denominations and the Anglican Church were influenced by Calvin's theology in varying degrees.
In another factor in the rise of democracy in the Anglo-American world, Calvin favored a mixture of democracy and aristocracy as the best form of government (mixed government). He appreciated the advantages of democracy. His political thought aimed to safeguard the rights and freedoms of ordinary men and women. In order to minimize the misuse of political power he suggested dividing it among several institutions in a system of checks and balances (separation of powers). Finally, Calvin taught that if worldly rulers rise up against God they should be put down. In this way, he and his followers stood in the vanguard of resistance to political absolutism and furthered the cause of democracy. The Congregationalists who founded Plymouth Colony (1620) and Massachusetts Bay Colony (1628) were convinced that the democratic form of government was the will of God. Enjoying self-rule, they practiced separation of powers. Rhode Island, Connecticut, and Pennsylvania, founded by Roger Williams, Thomas Hooker, and William Penn, respectively, combined democratic government with a limited freedom of religion that did not extend to Catholics (Congregationalism being the established, tax-supported religion in Connecticut). These colonies became safe havens for persecuted religious minorities, including Jews.
In England, Baptists Thomas Helwys ( 1575– 1616), and John Smyth ( 1554–) influenced the liberal political thought of the Presbyterian poet and politician John Milton (1608–1674) and of the philosopher John Locke (1632–1704), who in turn had both a strong impact on the political development in their home country (English Civil War of 1642–1651, Glorious Revolution of 1688) as well as in North America. The ideological basis of the American Revolution was largely provided by the radical Whigs, who had been inspired by Milton, Locke, James Harrington (1611–1677), Algernon Sidney (1623–1683), and other thinkers. The Whigs' "perceptions of politics attracted widespread support in America because they revived the traditional concerns of a Protestantism that had always verged on Puritanism". The United States Declaration of Independence, the United States Constitution and (American) Bill of Rights initiated a tradition of human and civil rights that continued in the French Declaration of the Rights of Man and of the Citizen and the constitutions of numerous countries around the world, e.g. Latin America, Japan, India, Germany, and other European countries. It is also echoed in the United Nations Charter and the Universal Declaration of Human Rights.
In the 19th century, churches based on or influenced by Calvin's theology became deeply involved in social reforms, e.g. the abolition of slavery (William Wilberforce, Harriet Beecher Stowe, Abraham Lincoln, and others), women suffrage, and prison reforms. Members of these churches formed co-operatives to help the impoverished masses. The founders of the Red Cross Movement, including Henry Dunant, were Reformed Christians. Their movement also initiated the Geneva Conventions.
Others view Calvinist influence as not always being solely positive. The Boers and Afrikaner Calvinists combined ideas from Calvinism and Kuyperian theology to justify apartheid in South Africa. As late as 1974 the majority of the Dutch Reformed Church in South Africa was convinced that their theological stances (including the story of the Tower of Babel) could justify apartheid. In 1990 the Dutch Reformed Church document Church and Society maintained that although they were changing their stance on apartheid, they believed that within apartheid and under God's sovereign guidance, "...everything was not without significance, but was of service to the Kingdom of God." These views were not universal and were condemned by many Calvinists outside South Africa. Pressure from both outside and inside the Dutch Reformed Calvinist church helped reverse apartheid in South Africa.
Throughout the world, the Reformed churches operate hospitals, homes for handicapped or elderly people, and educational institutions on all levels. For example, American Congregationalists founded Harvard University (1636), Yale University (1701), and about a dozen other colleges. A particular stream of influence of Calvinism concerns art. Visual art cemented society in the first modern nation state, the Netherlands, and also Neo-Calvinism put much weight on this aspect of life. Hans Rookmaaker is the most prolific example. In literature the non-fiction of Marilynne Robinson
argues for the modernity of Calvin's thinking, calling him a humanist scholar (p. 174, The Death of Adam).
|
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"B. B. Warfield",
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"Protestant Reformation",
"World Reformed Fellowship",
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"Connecticut",
"Geneva Conventions",
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"Scandinavia",
"forbidden fruit",
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"Lord's Supper in Reformed theology",
"priesthood of all believers",
"theological determinism",
"Christian universalism",
"John Marrant"
] |
6,026 |
Countable set
|
In mathematics, a set is countable if either it is finite or it can be made in one to one correspondence with the set of natural numbers. Equivalently, a set is countable if there exists an injective function from it into the natural numbers; this means that each element in the set may be associated to a unique natural number, or that the elements of the set can be counted one at a time, although the counting may never finish due to an infinite number of elements.
In more technical terms, assuming the axiom of countable choice, a set is countable if its cardinality (the number of elements of the set) is not greater than that of the natural numbers. A countable set that is not finite is said to be countably infinite.
The concept is attributed to Georg Cantor, who proved the existence of uncountable sets, that is, sets that are not countable; for example the set of the real numbers.
==A note on terminology ==
Although the terms "countable" and "countably infinite" as defined here are quite common, the terminology is not universal. An alternative style uses countable to mean what is here called countably infinite, and at most countable to mean what is here called countable.
The terms enumerable and denumerable may also be used, e.g. referring to countable and countably infinite respectively, definitions vary and care is needed respecting the difference with recursively enumerable.
==Definition==
A set S is countable if:
Its cardinality |S| is less than or equal to \aleph_0 (aleph-null), the cardinality of the set of natural numbers \N.
S is empty or there exists a surjective function from \N to S.
S is either finite (|S|<\aleph_0) or countably infinite.
The elements of S can be arranged in an infinite sequence a_0, a_1, a_2, \ldots, where a_i is distinct from a_j for i\neq j and every element of S is listed.
A set is uncountable if it is not countable, i.e. its cardinality is greater than \aleph_0.
==History==
In 1874, in his first set theory article, Cantor proved that the set of real numbers is uncountable, thus showing that not all infinite sets are countable. In 1878, he used one-to-one correspondences to define and compare cardinalities. In 1883, he extended the natural numbers with his infinite ordinals, and used sets of ordinals to produce an infinity of sets having different infinite cardinalities.
==Introduction==
A set is a collection of elements, and may be described in many ways. One way is simply to list all of its elements; for example, the set consisting of the integers 3, 4, and 5 may be denoted \{3, 4, 5\}, called roster form. This is only effective for small sets, however; for larger sets, this would be time-consuming and error-prone. Instead of listing every single element, sometimes an ellipsis ("...") is used to represent many elements between the starting element and the end element in a set, if the writer believes that the reader can easily guess what ... represents; for example, \{1, 2, 3, \dots, 100\} presumably denotes the set of integers from 1 to 100. Even in this case, however, it is still possible to list all the elements, because the number of elements in the set is finite. If we number the elements of the set 1, 2, and so on, up to n, this gives us the usual definition of "sets of size n".
Some sets are infinite; these sets have more than n elements where n is any integer that can be specified. (No matter how large the specified integer n is, such as n=10^{1000}, infinite sets have more than n elements.) For example, the set of natural numbers, denotable by \{0, 1, 2, 3, 4, 5,\dots\}, has infinitely many elements, and we cannot use any natural number to give its size. It might seem natural to divide the sets into different classes: put all the sets containing one element together; all the sets containing two elements together; ...; finally, put together all infinite sets and consider them as having the same size. This view works well for countably infinite sets and was the prevailing assumption before Georg Cantor's work. For example, there are infinitely many odd integers, infinitely many even integers, and also infinitely many integers overall. We can consider all these sets to have the same "size" because we can arrange things such that, for every integer, there is a distinct even integer:
\ldots \, -\! 2\! \rightarrow \! - \! 4, \, -\! 1\! \rightarrow \! - \! 2, \, 0\! \rightarrow \! 0, \, 1\! \rightarrow \! 2, \, 2\! \rightarrow \! 4 \, \cdots
or, more generally, n \rightarrow 2n (see picture). What we have done here is arrange the integers and the even integers into a one-to-one correspondence (or bijection), which is a function that maps between two sets such that each element of each set corresponds to a single element in the other set. This mathematical notion of "size", cardinality, is that two sets are of the same size if and only if there is a bijection between them. We call all sets that are in one-to-one correspondence with the integers countably infinite and say they have cardinality \aleph_0.
Georg Cantor showed that not all infinite sets are countably infinite. For example, the real numbers cannot be put into one-to-one correspondence with the natural numbers (non-negative integers). The set of real numbers has a greater cardinality than the set of natural numbers and is said to be uncountable.
==Formal overview==
By definition, a set S is countable if there exists a bijection between S and a subset of the natural numbers \N=\{0,1,2,\dots\}. For example, define the correspondence
a \leftrightarrow 1,\ b \leftrightarrow 2,\ c \leftrightarrow 3
Since every element of S=\{a,b,c\} is paired with precisely one element of \{1,2,3\}, and vice versa, this defines a bijection, and shows that S is countable. Similarly we can show all finite sets are countable.
As for the case of infinite sets, a set S is countably infinite if there is a bijection between S and all of \N. As examples, consider the sets A=\{1,2,3,\dots\}, the set of positive integers, and B=\{0,2,4,6,\dots\}, the set of even integers. We can show these sets are countably infinite by exhibiting a bijection to the natural numbers. This can be achieved using the assignments n \leftrightarrow n+1 and n \leftrightarrow 2n, so that
\begin{matrix}
0 \leftrightarrow 1, & 1 \leftrightarrow 2, & 2 \leftrightarrow 3, & 3 \leftrightarrow 4, & 4 \leftrightarrow 5, & \ldots \\[6pt]
0 \leftrightarrow 0, & 1 \leftrightarrow 2, & 2 \leftrightarrow 4, & 3 \leftrightarrow 6, & 4 \leftrightarrow 8, & \ldots
\end{matrix}
Every countably infinite set is countable, and every infinite countable set is countably infinite. Furthermore, any subset of the natural numbers is countable, and more generally:
The set of all ordered pairs of natural numbers (the Cartesian product of two sets of natural numbers, \N\times\N is countably infinite, as can be seen by following a path like the one in the picture: The resulting mapping proceeds as follows:
0 \leftrightarrow (0, 0), 1 \leftrightarrow (1, 0), 2 \leftrightarrow (0, 1), 3 \leftrightarrow (2, 0), 4 \leftrightarrow (1, 1), 5 \leftrightarrow (0, 2), 6 \leftrightarrow (3, 0), \ldots
This mapping covers all such ordered pairs.
This form of triangular mapping recursively generalizes to n-tuples of natural numbers, i.e., (a_1,a_2,a_3,\dots,a_n) where a_i and n are natural numbers, by repeatedly mapping the first two elements of an n-tuple to a natural number. For example, (0, 2, 3) can be written as ((0, 2), 3). Then (0, 2) maps to 5 so ((0, 2), 3) maps to (5, 3), then (5, 3) maps to 39. Since a different 2-tuple, that is a pair such as (a,b), maps to a different natural number, a difference between two n-tuples by a single element is enough to ensure the n-tuples being mapped to different natural numbers. So, an injection from the set of n-tuples to the set of natural numbers \N is proved. For the set of n-tuples made by the Cartesian product of finitely many different sets, each element in each tuple has the correspondence to a natural number, so every tuple can be written in natural numbers then the same logic is applied to prove the theorem.
The set of all integers \Z and the set of all rational numbers \Q may intuitively seem much bigger than \N. But looks can be deceiving. If a pair is treated as the numerator and denominator of a vulgar fraction (a fraction in the form of a/b where a and b\neq 0 are integers), then for every positive fraction, we can come up with a distinct natural number corresponding to it. This representation also includes the natural numbers, since every natural number n is also a fraction n/1. So we can conclude that there are exactly as many positive rational numbers as there are positive integers. This is also true for all rational numbers, as can be seen below.
In a similar manner, the set of algebraic numbers is countable.^{a_n}, where p_n is the n-th prime.}}
Sometimes more than one mapping is useful: a set A to be shown as countable is one-to-one mapped (injection) to another set B, then A is proved as countable if B is one-to-one mapped to the set of natural numbers. For example, the set of positive rational numbers can easily be one-to-one mapped to the set of natural number pairs (2-tuples) because p/q maps to (p,q). Since the set of natural number pairs is one-to-one mapped (actually one-to-one correspondence or bijection) to the set of natural numbers as shown above, the positive rational number set is proved as countable.
With the foresight of knowing that there are uncountable sets, we can wonder whether or not this last result can be pushed any further. The answer is "yes" and "no", we can extend it, but we need to assume a new axiom to do so.
For example, given countable sets \textbf{a},\textbf{b},\textbf{c},\dots, we first assign each element of each set a tuple, then we assign each tuple an index using a variant of the triangular enumeration we saw above:
\begin{array}{ c|c|c }
\text{Index} & \text{Tuple} & \text {Element} \\ \hline
0 & (0,0) & \textbf{a}_0 \\
1 & (0,1) & \textbf{a}_1 \\
2 & (1,0) & \textbf{b}_0 \\
3 & (0,2) & \textbf{a}_2 \\
4 & (1,1) & \textbf{b}_1 \\
5 & (2,0) & \textbf{c}_0 \\
6 & (0,3) & \textbf{a}_3 \\
7 & (1,2) & \textbf{b}_2 \\
8 & (2,1) & \textbf{c}_1 \\
9 & (3,0) & \textbf{d}_0 \\
10 & (0,4) & \textbf{a}_4 \\
\vdots & &
\end{array}
We need the axiom of countable choice to index all the sets \textbf{a},\textbf{b},\textbf{c},\dots simultaneously.
This set is the union of the length-1 sequences, the length-2 sequences, the length-3 sequences, and so on, each of which is a countable set (finite Cartesian product). Thus the set is a countable union of countable sets, which is countable by the previous theorem.
The elements of any finite subset can be ordered into a finite sequence. There are only countably many finite sequences, so also there are only countably many finite subsets.
These follow from the definitions of countable set as injective / surjective functions.
Cantor's theorem asserts that if A is a set and \mathcal{P}(A) is its power set, i.e. the set of all subsets of A, then there is no surjective function from A to \mathcal{P}(A). A proof is given in the article Cantor's theorem. As an immediate consequence of this and the Basic Theorem above we have:
For an elaboration of this result see Cantor's diagonal argument.
The set of real numbers is uncountable, and so is the set of all infinite sequences of natural numbers.
==Minimal model of set theory is countable==
If there is a set that is a standard model (see inner model) of ZFC set theory, then there is a minimal standard model (see Constructible universe). The Löwenheim–Skolem theorem can be used to show that this minimal model is countable. The fact that the notion of "uncountability" makes sense even in this model, and in particular that this model M contains elements that are:
subsets of M, hence countable,
but uncountable from the point of view of M,
was seen as paradoxical in the early days of set theory; see Skolem's paradox for more.
The minimal standard model includes all the algebraic numbers and all effectively computable transcendental numbers, as well as many other kinds of numbers.
==Total orders==
Countable sets can be totally ordered in various ways, for example:
Well-orders (see also ordinal number):
The usual order of natural numbers (0, 1, 2, 3, 4, 5, ...)
The integers in the order (0, 1, 2, 3, ...; −1, −2, −3, ...)
Other (not well orders):
The usual order of integers (..., −3, −2, −1, 0, 1, 2, 3, ...)
The usual order of rational numbers (Cannot be explicitly written as an ordered list!)
In both examples of well orders here, any subset has a least element; and in both examples of non-well orders, some subsets do not have a least element.
This is the key definition that determines whether a total order is also a well order.
|
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6,034 |
Cahn–Ingold–Prelog priority rules
|
In organic chemistry, the Cahn–Ingold–Prelog (CIP) sequence rules (also the CIP priority convention; named after Robert Sidney Cahn, Christopher Kelk Ingold, and Vladimir Prelog) are a standard process to completely and unequivocally name a stereoisomer of a molecule. The purpose of the CIP system is to assign an R or S descriptor to each stereocenter and an E or Z descriptor to each double bond so that the configuration of the entire molecule can be specified uniquely by including the descriptors in its systematic name. A molecule may contain any number of stereocenters and any number of double bonds, and each usually gives rise to two possible isomers. A molecule with an integer describing the number of stereocenters will usually have stereoisomers, and diastereomers each having an associated pair of enantiomers.
The key article setting out the CIP sequence rules was published in 1966, and was followed by further refinements, before it was incorporated into the rules of the International Union of Pure and Applied Chemistry (IUPAC), the official body that defines organic nomenclature, in 1974. as part of the IUPAC book Nomenclature of Organic Chemistry. The IUPAC presentation of the rules constitute the official, formal standard for their use, and it notes that "the method has been developed to cover all compounds with ligancy up to 4... and… [extended to the case of] ligancy 6… [as well as] for all configurations and conformations of such compounds." However, a different problem remains: in rare cases, two different stereoisomers of the same molecule can have the same CIP descriptors, so the CIP system may not be able to unambiguously name a stereoisomer, and other systems may be preferable.
==Steps for naming==
The steps for naming molecules using the CIP system are often presented as:
Identification of stereocenters and double bonds;
Assignment of priorities to the groups attached to each stereocenter or double-bonded atom; and
Assignment of R/S and E/Z descriptors.
===Assignment of priorities===
R/S and E/Z descriptors are assigned by using a system for ranking priority of the groups attached to each stereocenter. This procedure, often known as the sequence rules, is the heart of the CIP system. The overview in this section omits some rules that are needed only in rare cases.
Compare the atomic number (Z) of the atoms directly attached to the stereocenter; the group having the atom of higher atomic number Z receives higher priority (i.e. number 1).
If there is a tie, the atoms at distance 2 from the stereocenter have to be considered: a list is made for each group of further atoms bonded to the one directly attached to the stereocenter. Each list is arranged in order of decreasing atomic number Z. Then the lists are compared atom by atom; at the earliest difference, the group containing the atom of higher atomic number Z receives higher priority.
If there is still a tie, each atom in each of the two lists is replaced with a sublist of the other atoms bonded to it (at distance 3 from the stereocenter), the sublists are arranged in decreasing order of atomic number Z, and the entire structure is again compared atom by atom. This process is repeated recursively, each time with atoms one bond farther from the stereocenter, until the tie is broken.
====Isotopes====
If two groups differ only in isotopes, then the larger atomic mass is used to set the priority.
====Double and triple bonds====
If an atom, A, is double-bonded to another atom, then atom A should be treated as though it is "connected to the same atom twice". An atom that is double-bonded has a higher priority than an atom that is single bonded.
When B is replaced with a list of attached atoms, A itself, but not its "phantom", is excluded in accordance with the general principle of not doubling back along a bond that has just been followed. A triple bond is handled the same way except that A and B are each connected to two phantom atoms of the other.
====Cyclic molecules====
To handle a molecule containing one or more cycles, one must first expand it into a tree (called a hierarchical digraph) by traversing bonds in all possible paths starting at the stereocenter. When the traversal encounters an atom through which the current path has already passed, a phantom atom is generated in order to keep the tree finite. A single atom of the original molecule may appear in many places (some as phantoms, some not) in the tree.
=== Assigning descriptors ===
==== Stereocenters: R/S ====
A chiral sp3 hybridized isomer contains four different substituents. All four substituents are assigned prorites based on its atomic numbers. After the substituents of a stereocenter have been assigned their priorities, the molecule is oriented in space so that the group with the lowest priority is pointed away from the observer. If the substituents are numbered from 1 (highest priority) to 4 (lowest priority), then the sense of rotation of a curve passing through 1, 2 and 3 distinguishes the stereoisomers. In a configurational isomer, the lowest priority group (most times hydrogen) is positioned behind the plane or the hatched bond going away from the reader. The highest priority group will have an arc drawn connecting to the rest of the groups, finishing at the group of third priority. An arc drawn clockwise, has the rectus (R) assignment. An arc drawn counterclockwise, has the sinister (S) assignment. The names are derived from the Latin for 'right' and 'left', respectively. When naming an organic isomer, the abbreviation for either rectus or sinister assignment is placed in front of the name in parentheses. For example, 3-methyl-1-pentene with a rectus assignment is formatted as (R)-3-methyl-1-pentene.
==== Double bonds: E/Z ====
For double bonded molecules, Cahn–Ingold–Prelog priority rules (CIP rules) are followed to determine the priority of substituents of the double bond. If both of the high priority groups are on the same side of the double bond (cis configuration), then the stereoisomer is assigned the configuration Z (zusammen, German word meaning "together"). If the high priority groups are on opposite sides of the double bond (trans configuration), then the stereoisomer is assigned the configuration E (entgegen, German word meaning "opposed")
==== Coordination compounds ====
In some cases where stereogenic centers are formed, the configuration must be specified. Without the presence of a non-covalent interaction, a compound is achiral. Some professionals have proposed a new rule to account for this. This rule states that "non-covalent interactions have a fictitious number between 0 and 1" when assigning priority. Compounds in which this occurs are referred to as coordination compounds.
==== Spiro compounds ====
Some spiro compounds, for example the SDP ligands ((R)- and (S)-7,7'-bis(diphenylphosphaneyl)-2,2',3,3'-tetrahydro-1,1'-spirobi[indene]), represent chiral, C2-symmetrical molecules where the rings lie approximately at right angles to each other and each molecule cannot be superposed on its mirror image.
== Describing multiple centers ==
If a compound has more than one chiral stereocenter, each center is denoted by either R or S. For example, ephedrine exists in (1R,2S) and (1S,2R) stereoisomers, which are distinct mirror-image forms of each other, making them enantiomers. This compound also exists as the two enantiomers written (1R,2R) and (1S,2S), which are named pseudoephedrine rather than ephedrine. All four of these isomers are named 2-methylamino-1-phenyl-1-propanol in systematic nomenclature. However, ephedrine and pseudoephedrine are diastereomers, or stereoisomers that are not enantiomers because they are not related as mirror-image copies. Pseudoephedrine and ephedrine are given different names because, as diastereomers, they have different chemical properties, even for racemic mixtures of each.
More generally, for any pair of enantiomers, all of the descriptors are opposite: (R,R) and (S,S) are enantiomers, as are (R,S) and (S,R). Diastereomers have at least one descriptor in common; for example (R,S) and (R,R) are diastereomers, as are (S,R) and (S,S). This holds true also for compounds having more than two stereocenters: if two stereoisomers have at least one descriptor in common, they are diastereomers. If all the descriptors are opposite, they are enantiomers.
A meso compound is an achiral molecule, despite having two or more stereogenic centers. A meso compound is superposable on its mirror image, therefore it reduces the number of stereoisomers predicted by the 2n rule. This occurs because the molecule obtains a plane of symmetry that causes the molecule to rotate around the central carbon–carbon bond.
== Relative configuration ==
The relative configuration of two stereoisomers may be denoted by the descriptors R and S with an asterisk (*). (R*,R*) means two centers having identical configurations, (R,R) or (S,S); (R*,S*) means two centers having opposite configurations, (R,S) or (S,R). To begin, the lowest-numbered (according to IUPAC systematic numbering) stereogenic center is given the R* descriptor.
To designate two anomers the relative stereodescriptors alpha (α) and beta (β) are used. In the α anomer the anomeric carbon atom and the reference atom do have opposite configurations (R,S) or (S,R), whereas in the β anomer they are the same (R,R) or (S,S).
== Faces ==
Stereochemistry also plays a role assigning faces to trigonal molecules such as ketones. A nucleophile in a nucleophilic addition can approach the carbonyl group from two opposite sides or faces. When an achiral nucleophile attacks acetone, both faces are identical and there is only one reaction product. When the nucleophile attacks butanone, the faces are not identical (enantiotopic) and a racemic product results. When the nucleophile is a chiral molecule diastereoisomers are formed. When one face of a molecule is shielded by substituents or geometric constraints compared to the other face the faces are called diastereotopic. The same rules that determine the stereochemistry of a stereocenter (R or S) also apply when assigning the face of a molecular group. The faces are then called the Re-face and Si-face. In the example displayed on the right, the compound acetophenone is viewed from the Re-face. Hydride addition as in a reduction process from this side will form the (S)-enantiomer and attack from the opposite Si-face will give the (R)-enantiomer. However, one should note that adding a chemical group to the prochiral center from the Re-face will not always lead to an (S)-stereocenter, as the priority of the chemical group has to be taken into account. That is, the absolute stereochemistry of the product is determined on its own and not by considering which face it was attacked from. In the above-mentioned example, if chloride (Z = 17) were added to the prochiral center from the Re-face, this would result in an (R)-enantiomer.
|
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] |
6,035 |
Celibacy
|
Celibacy (from Latin caelibatus) is the state of voluntarily being unmarried, sexually abstinent, or both, usually for religious reasons. It is often in association with the role of a religious official or devotee. In its narrow sense, the term celibacy is applied only to those for whom the unmarried state is the result of a sacred vow, act of renunciation, or religious conviction. In a wider sense, it is commonly understood to only mean abstinence from sexual activity.
Celibacy has existed in one form or another throughout history, in virtually all the major religions of the world, and views on it have varied. Classical Hindu culture encouraged asceticism and celibacy in the later stages of life, after one has met one's societal obligations. Jainism, on the other hand, preached complete celibacy even for young monks and considered celibacy to be an essential behavior to attain moksha. Buddhism is similar to Jainism in this respect. There were, however, significant cultural differences in the various areas where Buddhism spread, which affected the local attitudes toward celibacy. A somewhat similar situation existed in Japan, where the Shinto tradition also opposed celibacy. In most native African and Native American religious traditions, celibacy has been viewed negatively as well, although there were exceptions like periodic celibacy practiced by some Mesoamerican warriors.
The Romans viewed celibacy as an aberration and legislated fiscal penalties against it, with the exception of the Vestal Virgins, who took a 30-year vow of chastity in order to devote themselves to the study and correct observance of state rituals. In Christianity, celibacy means the promise to live either virginal or celibate in the future. Such a vow of celibacy has been normal for some centuries for Catholic priests, Catholic and Eastern Orthodox monks, and nuns. In addition, a promise or vow of celibacy may be made in the Anglican Communion and some Protestant churches or communities, such as the Shakers; for members of religious orders and religious congregations; and for hermits, consecrated virgins, and deaconesses. Judaism and Islam have denounced celibacy, as both religions emphasize marriage and family life; however, the priests of the Essenes, a Jewish sect during the Second Temple period, practised celibacy. Several hadiths indicate that the Islamic prophet Muhammad denounced celibacy.
==Etymology==
The English word celibacy derives from the Latin caelibatus, "state of being unmarried", from Latin , meaning "unmarried". This word derives from two Proto-Indo-European stems, "alone" and "living".
==Abstinence and celibacy==
The words abstinence and celibacy are often used interchangeably, but are not necessarily the same thing. Sexual abstinence, also known as continence, is abstaining from some or all aspects of sexual activity, often for some limited period of time, while celibacy may be defined as a voluntary religious vow not to marry or engage in sexual activity. Asexuality is commonly conflated with celibacy and sexual abstinence, but it is considered distinct from the two, as celibacy and sexual abstinence are behavioral and those who use those terms for themselves are generally motivated by factors such as an individual's personal or religious beliefs.
A. W. Richard Sipe, while focusing on the topic of celibacy in Catholicism, states that "the most commonly assumed definition of celibate is simply an unmarried or single person, and celibacy is perceived as synonymous with sexual abstinence or restraint." Sipe adds that even in the relatively uniform milieu of Catholic priests in the United States there seems to be "simply no clear operational definition of celibacy". Elizabeth Abbott commented on the terminology in her A History of Celibacy (2001) writing that she "drafted a definition of celibacy that discarded the rigidly pedantic and unhelpful distinctions between celibacy, chastity, and virginity..."
The concept of "new" celibacy was introduced by Gabrielle Brown in her 1980 book The New Celibacy. In a revised version (1989) of her book, she claims abstinence to be "a response on the outside to what's going on, and celibacy is a response from the inside". According to her definition, celibacy (even short-term celibacy that is pursued for non-religious reasons) is much more than not having sex. It is more intentional than abstinence, and its goal is personal growth and empowerment. Although Brown repeatedly states that celibacy is a matter of choice, she clearly suggests that those who do not choose this route are somehow missing out. This new perspective on celibacy is echoed by several authors including Elizabeth Abbott, Wendy Keller, and Wendy Shalit.
==Buddhism==
The rule of celibacy in the Buddhist religion, whether Mahayana or Theravada, has a long history. Celibacy was advocated as an ideal rule of life for all monks and nuns by Gautama Buddha, except in Japan where it is not strictly followed due to historical and political developments following the Meiji Restoration. In Japan, celibacy was an ideal among Buddhist clerics for hundreds of years. But violations of clerical celibacy were so common for so long that finally, in 1872, state laws made marriage legal for Buddhist clerics. Subsequently, ninety percent of Buddhist monks/clerics married. An example is Higashifushimi Kunihide, a prominent Buddhist priest of Japanese royal ancestry who was married and a father whilst serving as a monk for most of his lifetime.
Gautama, later known as the Buddha, is known for his renunciation of his wife, Princess Yasodharā, and son, Rahula. In order to pursue an ascetic life, he needed to renounce aspects of the impermanent world, including his wife and son. Later on both his wife and son joined the ascetic community and are mentioned in the Buddhist texts to have become enlightened. In another sense, a buddhavacana recorded the zen patriarch Vimalakirti as being an advocate of marital continence instead of monastic renunciation. This sutra became somewhat popular due to its brash humour as well as its integration of the role of women in lay and spiritual life.
==Christianity==
There is no commandment in the New Testament that Jesus Christ's disciples have to live in celibacy. However, it is a general view that Christ himself lived a life of perfect chastity; thus, "Voluntary chastity is the imitation of him who was the virgin Son of a virgin Mother". One of his invocations is "King of virgins and lover of stainless chastity" (Rex virginum, amator castitatis).
Furthermore, Christ, when his disciples suggest it is "better not to marry," stated "Not everyone can accept this word, but only those to whom it has been given. For there are eunuchs who have been so from birth, and there are eunuchs who have been made eunuchs by others, and there are eunuchs who have made themselves eunuchs for the sake of the kingdom of heaven. Let anyone accept this who can" (Matthew 19:10-12, NRSV). While eunuchs were not generally celibate, over subsequent centuries this statement has come to be interpreted as referring to celibacy.
Paul the Apostle emphasized the importance of overcoming the desires of the flesh and saw the state of celibacy being superior to that of marriage. Paul made parallels between the relations between spouses and God's relationship with the church. "Husbands, love your wives even as Christ loved the church. Husbands should love their wives as their own bodies" (Ephesians 5:25–28). Paul himself was celibate and said that his wish was "that all of you were as I am" (1 Corinthians 7:7). In fact, this entire chapter endorses celibacy while also clarifying that marriage is also acceptable.
The early Christians lived in the belief that the end of the world would soon come upon them, and saw no point in planning new families and having children. According to Chadwick, this was why Paul encouraged both celibate and marital lifestyles
A number of early Christian martyrs were women or girls who had given themselves to Christ in perpetual virginity, such as Saint Agnes and Saint Lucy. According to most Christian thought, the first sacred virgin was Mary, the mother of Jesus, who was consecrated by the Holy Spirit during the Annunciation. Tradition also has it that the Apostle Matthew consecrated virgins. In the Catholic Church and the Orthodox churches, a consecrated virgin is a woman who has been consecrated by the church to a life of perpetual virginity in the service of the church.
===Desert Fathers===
The Desert Fathers were Christian hermits and ascetics Sometime around AD 270, Anthony heard a Sunday sermon stating that perfection could be achieved by selling all of one's possessions, giving the proceeds to the poor, and following Christ (Matthew 19:21). He followed the advice and made the further step of moving deep into the desert to seek complete solitude.
Over time, the model of Anthony and other hermits attracted many followers, who lived alone in the desert or in small groups. They chose a life of extreme asceticism, renouncing all the pleasures of the senses, rich food, baths, rest, and anything that made them comfortable. Thousands joined them in the desert, mostly men but also a handful of women. Religious seekers also began going to the desert seeking advice and counsel from the early Desert Fathers. By the time of Anthony's death, there were so many men and women living in the desert in celibacy that it was described as "a city" by Anthony's biographer.
According to the later St. Jerome (420), celibacy is a moral virtue, consisting of living in the flesh, but outside the flesh, and so being not corrupted by it (vivere in carne praeter carnem). Celibacy excludes not only libidinous acts, but also sinful thoughts or desires of the flesh. Jerome referred to marriage prohibition for priests when he claimed in Against Jovinianus that Peter and the other apostles had been married before they were called, but subsequently gave up their marital relations.
In the Catholic, Orthodox and Oriental Orthodox traditions, bishops are required to be celibate. In the Eastern Catholic and Orthodox traditions, priests and deacons are allowed to be married, yet have to remain celibate if they are unmarried at the time of ordination.
===Augustinian view===
In the early Church, higher clerics lived in marriages. Augustine taught that the original sin of Adam and Eve was either an act of foolishness (insipientia) followed by pride and disobedience to God, or else inspired by pride. The first couple disobeyed God, who had told them not to eat of the tree of the knowledge of good and evil (Gen 2:17). The tree was a symbol of the order of creation. Self-centeredness made Adam and Eve eat of it, thus failing to acknowledge and respect the world as it was created by God, with its hierarchy of beings and values. They would not have fallen into pride and lack of wisdom, if Satan had not sown into their senses "the root of evil" (radix mali). Their nature was wounded by concupiscence or libido, which affected human intelligence and will, as well as affections and desires, including sexual desire.
The sin of Adam is inherited by all human beings. Already in his pre-Pelagian writings, Augustine taught that original sin was transmitted by concupiscence, which he regarded as the passion of both soul and body, making humanity a massa damnata (mass of perdition, condemned crowd) and much enfeebling, though not destroying, the freedom of the will.
In the early 3rd century, the Canons of the Apostolic Constitutions decreed that only lower clerics might still marry after their ordination, but marriage of bishops, priests, and deacons were not allowed.
===After Augustine===
One explanation for the origin of obligatory celibacy is that it is based on the writings of Saint Paul, who wrote of the advantages of celibacy allowed a man in serving the Lord. Celibacy was popularised by the early Christian theologians like Saint Augustine of Hippo and Origen. Another possible explanation for the origins of obligatory celibacy revolves around more practical reason, "the need to avoid claims on church property by priests' offspring". It remains a matter of Canon Law (and often a criterion for certain religious orders, especially Franciscans) that priests may not own land and therefore cannot pass it on to legitimate or illegitimate children. The land belongs to the Church through the local diocese as administered by the Local Ordinary (usually a bishop), who is often an ex officio corporation sole. Celibacy is viewed differently by the Catholic Church and the various Protestant communities. It includes clerical celibacy, celibacy of the consecrated life and voluntary celibacy.
The Protestant Reformation rejected celibate life and sexual continence for preachers. Protestant celibate communities have emerged, especially from Anglican and Lutheran backgrounds. A few minor Christian sects advocate celibacy as a better way of life. These groups included the Shakers, the Harmony Society and the Ephrata Cloister.
Many evangelicals prefer the term "abstinence" to "celibacy". Assuming everyone will marry, they focus their discussion on refraining from premarital sex and focusing on the joys of a future marriage. But some evangelicals, particularly older singles, desire a positive message of celibacy that moves beyond the "wait until marriage" message of abstinence campaigns. They seek a new understanding of celibacy that is focused on God rather than a future marriage or a lifelong vow to the Church.
There are also many Pentecostal churches which practice celibate ministry. For instance, the full-time ministers of the Pentecostal Mission are celibate and generally single. Married couples who enter full-time ministry may become celibate and could be sent to different locations.
===Catholic Church===
During the first three or four centuries, no law was promulgated prohibiting clerical marriage. Celibacy was a matter of choice for bishops, priests, and deacons.
Statutes forbidding clergy from having wives were written beginning with the Council of Elvira (306) but these early statutes were not universal and were often defied by clerics and then retracted by hierarchy. The Synod of Gangra (345) condemned a false asceticism whereby worshipers boycotted celebrations presided over by married clergy. The Apostolic Constitutions () excommunicated a priest or bishop who left his wife "under the pretense of piety" (Mansi, 1:51).
"A famous letter of Synesius of Cyrene () is evidence both for the respecting of personal decision in the matter and for contemporary appreciation of celibacy. For priests and deacons clerical marriage continued to be in vogue".
"The Second Lateran Council (1139) seems to have enacted the first written law making sacred orders a direct impediment to marriage for the universal Church." In places, coercion and enslavement of clerical wives and children was apparently involved in the enforcement of the law. "The earliest decree in which the children [of clerics] were declared to be slaves and never to be enfranchised [freed] seems to have been a canon of the Synod of Pavia in 1018. Similar penalties were promulgated against wives and concubines (see the Synod of Melfi, 1189 can. xii), who by the very fact of their unlawful connexion with a subdeacon or clerk of higher rank became liable to be seized by the over-lord". In contrast, Saint Peter, whom the Church considers its first Pope, was married given that he had a mother-in-law whom Christ healed (Matthew 8). But some argue that Peter was a widower, due to the fact that this passage does not mention his wife, and that his mother-in-law is the one who serves Christ and the apostles after she is healed. Furthermore, Peter himself states: "Then Peter spoke up, 'We have left everything to follow you!' 'Truly I tell you', Jesus replied, 'no one who has left home or brothers or sisters or mother or father or children or fields for me and the gospel will fail to receive a hundred times as much'" (Mark 10,28–30).
Usually, only celibate men are ordained as priests in the Latin Church. Married clergy who have converted from other Christian denominations can be ordained Roman Catholic priests without becoming celibate. Priestly celibacy is not doctrine of the Church (such as the belief in the Assumption of Mary) but a matter of discipline, like the use of the vernacular (local) language in Mass or Lenten fasting and abstinence. As such, it can theoretically change at any time though it still must be obeyed by Catholics until the change were to take place. The Eastern Catholic Churches ordain both celibate and married men. However, in both the East and the West, bishops are chosen from among those who are celibate. In Ireland, several priests have fathered children, the two most prominent being bishop Eamonn Casey and Michael Cleary.
The classical heritage flourished throughout the Middle Ages in both the Byzantine Greek East and the Latin West. When discerning the population of Christendom in medieval Europe during the Middle Ages, Will Durant, referring to Plato's ideal community, stated on the oratores (clergy):
"The clergy, like Plato's guardians, were placed in authority not by the suffrages of the people, but by their talent as shown in ecclesiastical studies and administration, by their disposition to a life of meditation and simplicity, and (perhaps it should be added) by the influence of their relatives with the powers of state and church. In the latter half of the period in which they ruled [AD 800 onwards], the clergy were as free from family cares as even Plato could desire; and in some cases it would seem they enjoyed no little of the reproductive freedom accorded to the guardians. Celibacy was part of the psychological structure of the power of the clergy; for on the one hand they were unimpeded by the narrowing egoism of the family, and on the other their apparent superiority to the call of the flesh added to the awe in which lay sinners held them …"
===Celibate homosexual Christians===
Some homosexual Christians choose to be celibate following their denomination's teachings on homosexuality.
In 2014, the American Association of Christian Counselors amended its code of ethics to eliminate the promotion of conversion therapy for homosexuals and encouraged them to be celibate instead.
==Islam==
Islamic attitudes toward celibacy have been complex, Muhammad denounced it, however some Sufi orders embrace it. Islam does not promote celibacy; rather it condemns premarital sex and extramarital sex. In fact, according to Islam, marriage enables one to attain the highest form of righteousness within this sacred spiritual bond but the Qur'an does not state it as an obligation. The Qur'an (Q57:27) states, "But the Monasticism which they (who followed Jesus) invented for themselves, We did not prescribe for them but only to please God therewith, but that they did not observe it with the right observance." Therefore, religion is clearly not a reason to stay unmarried although people are allowed to live their lives however they are comfortable; but relationships and sex outside of marriage, let alone forced marriage, is definitely a sin, "Oh you who believe! You are forbidden to inherit women against their will" (Q4:19). In addition, marriage partners can be distractions from practicing religion at the same time, "Your mates and children are only a trial for you" (Q64:15) however that still does not mean Islam does not encourage people who have sexual desires and are willing to marry. Anyone who does not (intend to) get married in this life can always do it in the Hereafter instead.
Celibacy appears as a peculiarity among some Sufis.
Celibacy was practiced by women saints in Sufism. Celibacy was debated along with women's roles in Sufism in medieval times.
Celibacy, poverty, meditation, and mysticism within an ascetic context along with worship centered around saints' tombs were promoted by the Qadiri Sufi order among Hui Muslims in China. In China, unlike other Muslim sects, the leaders (Shaikhs) of the Qadiriyya Sufi order are celibate. Unlike other Sufi orders in China, the leadership within the order is not a hereditary position, rather, one of the disciples of the celibate Shaikh is chosen by the Shaikh to succeed him. The 92-year-old celibate Shaikh Yang Shijun was the leader of the Qadiriya order in China as of 1998.
Celibacy is practiced by Haydariya Sufi dervishes.
== Zoroastrianism ==
Zoroastrian text Videvdad (4:47) praises a married man by saying:The man who has a wife is far above him who is unmarried...
==Meher Baba==
The spiritual teacher Meher Baba stated that "[F]or the [spiritual] aspirant a life of strict celibacy is preferable to married life, if restraint comes to him easily without undue sense of self-repression. Such restraint is difficult for most persons and sometimes impossible, and for them married life is decidedly more helpful than a life of celibacy. For ordinary persons, married life is undoubtedly advisable unless they have a special aptitude for celibacy". Baba also asserted that "The value of celibacy lies in the habit of restraint and the sense of detachment and independence which it gives" and that "The aspirant must choose one of the two courses which are open to him. He must take to the life of celibacy or to the married life, and he must avoid at all costs a cheap compromise between the two. Promiscuity in sex gratification is bound to land the aspirant in a most pitiful and dangerous chaos of ungovernable lust."
==Ancient Greece and Rome==
In Sparta and many other Greek cities, failure to marry was grounds for loss of citizenship, and could be prosecuted as a crime. Both Cicero and Dionysius of Halicarnassus stated that Roman law forbade celibacy. There are no records of such a prosecution, nor is the Roman punishment for refusing to marry known.
Pythagoreanism was the system of esoteric and metaphysical beliefs held by Pythagoras and his followers. Pythagorean thinking was dominated by a profoundly mystical view of the world. The Pythagorean code further restricted his members from eating meat, fish, and beans which they practised for religious, ethical and ascetic reasons, in particular the idea of metempsychosis – the transmigration of souls into the bodies of other animals.
"Pythagoras himself established a small community that set a premium on study, vegetarianism, and sexual restraint or abstinence. Later philosophers believed that celibacy would be conducive to the detachment and equilibrium required by the philosopher's calling."
==The Balkans==
The tradition of sworn virgins developed out of the Kanuni i Lekë Dukagjinit (, or simply the Kanun). The Kanun is not a religious document – many groups follow this code, including Roman Catholics, the Albanian Orthodox, and Muslims.
Women who become sworn virgins make a vow of celibacy, and are allowed to take on the social role of men: inheriting land, wearing male clothing, etc.
== Political contexts ==
During the May Fourth Movement in China, pledges of celibacy were a means through which participants resisted traditional marriage and devote themselves to revolutionary causes.
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Coalition government
|
A coalition government, or coalition cabinet, is a government by political parties that enter into a power-sharing arrangement of the executive. Coalition governments usually occur when no single party has achieved an absolute majority after an election. A party not having majority is common under proportional representation, but not in nations with majoritarian electoral systems.
A coalition government may also be created in a time of national difficulty or crisis (for example, during wartime or economic crisis) to give a government the high degree of perceived political legitimacy or collective identity, it can also play a role in diminishing internal political strife. In such times, parties have formed all-party coalitions (national unity governments, grand coalitions).
If a coalition collapses, the prime minister and cabinet may be ousted by a vote of no confidence, call snap elections, form a new majority coalition, or continue as a minority government.
== Formation of coalition governments ==
For a coalition to come about the coalition partners need to compromise on their policy expectations. One coalition or probing partner must lose for the other one to win, to achieve a Nash equilibrium, which is necessary for a coalition to form. If the parties are not willing to compromise, the coalition will not come about.
Before parties form a coalition government, they formulate a coalition agreement, in which they state what policies they try to adapt in the legislative period.
==Coalition agreement==
In multi-party states, a coalition agreement is an agreement negotiated between the parties that form a coalition government. It codifies the most important shared goals and objectives of the cabinet. It is often written by the leaders of the parliamentary groups. Coalitions that have a written agreement are more productive than those that do not.
If an issue is discussed more deeply and in more detail in chamber than what appears in the coalition agreement, it indicates that the coalition parties do not share the same policy ideas. Hence, a more detailed written formulation of the issue helps parties in the coalition to limit 'agency loss' when the ministry overseeing that issue is managed by another coalition party.
== Electoral accountability ==
Coalition governments can also impact voting behavior by diminishing the clarity of responsibility.
Electoral accountability is harder to achieve in coalition governments than in single party governments because there is no direct responsibility within the governing parties in the coalition.
Retrospective voting has a huge influence on the outcome of an election. However, the risk of retrospective voting is a lot weaker with coalition governments than in single party governments. Within the coalition, the party with the head of state has the biggest risk of retrospective voting.
==Distribution==
Countries which often operate with coalition cabinets include: the Nordic countries, the Benelux countries, Australia, Austria, Brazil, Chile, Cyprus, East Timor, France, Germany, Greece, Guinea-Bissau, India, Indonesia, Ireland, Israel, Italy, Japan, Kenya, Kosovo, Latvia, Lebanon, Lesotho, Lithuania, Malaysia, Nepal, New Zealand, Pakistan, Thailand, Spain, Trinidad and Tobago, Turkey, and Ukraine. Switzerland has been ruled by a consensus government with a coalition of the four strongest parties in parliament since 1959, called the "Magic Formula". Between 2010 and 2015, the United Kingdom also operated a formal coalition between the Conservative and the Liberal Democrat parties, but this was unusual: the UK usually has a single-party majority government. Not every parliament forms a coalition government, for example the European Parliament.
===Armenia===
Armenia became an independent state in 1991, following the collapse of the Soviet Union. Since then, many political parties were formed in it, who mainly work with each other to form coalition governments. The country was governed by the My Step Alliance coalition after successfully gaining a majority in the National Assembly of Armenia following the 2018 Armenian parliamentary election.
===Australia===
In federal Australian politics, the conservative Liberal, National, Country Liberal and Liberal National parties are united in a coalition, known simply as the Coalition.
While nominally two parties, the Coalition has become so stable, at least at the federal level, that in practice the lower house of Parliament has become a two-party system, with the Coalition and the Labor Party being the major parties. This coalition is also found in the states of New South Wales and Victoria. In South Australia and Western Australia the Liberal and National parties compete separately, while in the Northern Territory and Queensland the two parties have merged, forming the Country Liberal Party, in 1978, and the Liberal National Party, in 2008, respectively.
Coalition governments involving the Labor Party and the Australian Greens have occurred at state and territory level, for example following the 2010 Tasmanian state election and the 2016 and 2020 Australian Capital Territory elections.
===Belgium===
In Belgium, a nation internally divided along linguistic lines (primarily between Dutch-speaking Flanders in the north and French-speaking Wallonia in the south, with Brussels also being by and large Francophone), each main political disposition (Social democracy, liberalism, right-wing populism, etc.) is, with the exception of the far-left Workers' Party of Belgium, split between Francophone and Dutch-speaking parties (e.g. the Dutch-speaking Vooruit and French-speaking Socialist Party being the two social-democratic parties). In the 2019 federal election, no party got more than 17% of the vote. Thus, forming a coalition government is an expected and necessary part of Belgian politics. In Belgium, coalition governments containing ministers from six or more parties are not uncommon; consequently, government formation can take an exceptionally long time. Between 2007 and 2011, Belgium operated under a caretaker government as no coalition could be formed.
===Canada===
In Canada, the Great Coalition was formed in 1864 by the Clear Grits, , and Liberal-Conservative Party. During the First World War, Prime Minister Robert Borden attempted to form a coalition with the opposition Liberals to broaden support for controversial conscription legislation. The Liberal Party refused the offer but some of their members did cross the floor and join the government. Although sometimes referred to as a coalition government, according to the definition above, it was not. It was disbanded after the end of the war.
During the 2008–09 Canadian parliamentary dispute, two of Canada's opposition parties signed an agreement to form what would become the country's second federal coalition government since Confederation if the minority Conservative government was defeated on a vote of non-confidence, unseating Stephen Harper as Prime Minister. The agreement outlined a formal coalition consisting of two opposition parties, the Liberal Party and the New Democratic Party. The Bloc Québécois agreed to support the proposed coalition on confidence matters for 18 months. In the end, parliament was prorogued by the Governor General, and the coalition dispersed before parliament was reconvened.
According to historian Christopher Moore, coalition governments in Canada became much less possible in 1919, when the leaders of parties were no longer chosen by elected MPs but instead began to be chosen by party members. Such a manner of leadership election had never been tried in any parliamentary system before. According to Moore, as long as that kind of leadership selection process remains in place and concentrates power in the hands of the leader, as opposed to backbenchers, then coalition governments will be very difficult to form. Moore shows that the diffusion of power within a party tends to also lead to a diffusion of power in the parliament in which that party operates, thereby making coalitions more likely.
====Provincial====
Several coalition governments have been formed within provincial politics. As a result of the 1919 Ontario election, the United Farmers of Ontario and the Labour Party, together with three independent MLAs, formed a coalition that governed Ontario until 1923.
In British Columbia, the governing Liberals formed a coalition with the opposition Conservatives in order to prevent the surging, left-wing Cooperative Commonwealth Federation from taking power in the 1941 British Columbia general election. Liberal premier Duff Pattullo refused to form a coalition with the third-place Conservatives, so his party removed him. The Liberal–Conservative coalition introduced a winner-take-all preferential voting system (the "Alternative Vote") in the hopes that their supporters would rank the other party as their second preference; however, this strategy backfired in the subsequent 1952 British Columbia general election where, to the surprise of many, the right-wing populist BC Social Credit Party won a minority. They were able to win a majority in the subsequent election as Liberal and Conservative supporters shifted their anti-CCF vote to Social Credit.
Manitoba has had more formal coalition governments than any other province. Following gains by the United Farmer's/Progressive movement elsewhere in the country, the United Farmers of Manitoba unexpectedly won the 1921 election. Like their counterparts in Ontario, they had not expected to win and did not have a leader. They asked John Bracken, a professor in animal husbandry, to become leader and premier. Bracken changed the party's name to the Progressive Party of Manitoba. During the Great Depression, Bracken survived at a time when other premiers were being defeated by forming a coalition government with the Manitoba Liberals (eventually, the two parties would merge into the Liberal-Progressive Party of Manitoba, and decades later, the party would change its name to the Manitoba Liberal Party). In 1940, Bracken formed a wartime coalition government with almost every party in the Manitoba Legislature (the Conservatives, CCF, and Social Credit; however, the CCF broke with the coalition after a few years over policy differences). The only party not included was the small, communist Labor-Progressive Party, which had a handful of seats.
In Saskatchewan, NDP premier Roy Romanow formed a formal coalition with the Saskatchewan Liberals in 1999 after being reduced to a minority. After two years, the newly elected Liberal leader David Karwacki ordered the coalition be disbanded, the Liberal caucus disagreed with him and left the Liberals to run as New Democrats in the upcoming election. The Saskatchewan NDP was re-elected with a majority under its new leader Lorne Calvert, while the Saskatchewan Liberals lost their remaining seats and have not been competitive in the province since.
===Denmark===
From the creation of the Folketing in 1849 through the introduction of proportional representation in 1918, there were only single-party governments in Denmark. Thorvald Stauning formed his second government and Denmark's first coalition government in 1929. Since then, the norm has been coalition governments, though there have been periods where single-party governments were frequent, such as the decade after the end of World War II, during the 1970s, and in the late 2010s. Every government from 1982 until the 2015 elections were coalitions. While Mette Frederiksen's first government only consisted of her own Social Democrats, her second government is a coalition of the Social Democrats, Venstre, and the Moderates.
When the Social Democrats under Stauning won 46% of the votes in the 1935 election, this was the closest any party has gotten to winning an outright majority in parliament since 1918. One party has thus never held a majority alone, and even one-party governments have needed to have confidence agreements with at least one other party to govern. For example, though Frederiksen's first government only consisted of the Social Democrats, it also relied on the support of the Social Liberal Party, the Socialist People's Party, and the Red–Green Alliance.
===Finland===
In Finland, no party has had an absolute majority in the parliament since independence, and multi-party coalitions have been the norm. Finland experienced its most stable government (Lipponen I and II) since independence with a five-party governing coalition, a so-called "rainbow government". The Lipponen cabinets set the stability record and were unusual in the respect that both the centre-left (SDP) and radical left-wing (Left Alliance) parties sat in the government with the major centre-right party (National Coalition). The Katainen cabinet was also a rainbow coalition of a total of five parties.
===Germany===
In Germany, coalition governments are the norm, as it is rare for any single party to win a majority in parliament. The German political system makes extensive use of the constructive vote of no confidence, which requires governments to control an absolute majority of seats. Every government since the foundation of the Federal Republic in 1949 has involved at least two political parties. Typically, governments involve one of the two major parties forming a coalition with a smaller party. For example, from 1982 to 1998, the country was governed by a coalition of the CDU/CSU with the minor Free Democratic Party (FDP); from 1998 to 2005, a coalition of the Social Democratic Party of Germany (SPD) and the minor Greens held power. The CDU/CSU comprises an alliance of the Christian Democratic Union of Germany and Christian Social Union in Bavaria, described as "sister parties" which form a joint parliamentary group, and for this purpose are always considered a single party. Coalition arrangements are often given names based on the colours of the parties involved, such as "red-green" for the SPD and Greens. Coalitions of three parties are often named after countries whose flags contain those colours, such as the black-yellow-green Jamaica coalition.
Grand coalitions of the two major parties also occur, but these are relatively rare, as they typically prefer to associate with smaller ones. However, if the major parties are unable to assemble a majority, a grand coalition may be the only practical option. This was the case following the 2005 federal election, in which the incumbent SPD–Green government was defeated but the opposition CDU/CSU–FDP coalition also fell short of a majority. A grand coalition government was subsequently formed between the CDU/CSU and the SPD. Partnerships like these typically involve carefully structured cabinets: Angela Merkel of the CDU/CSU became Chancellor while the SPD was granted the majority of cabinet posts.
Coalition formation has become increasingly complex as voters increasingly migrate away from the major parties during the 2000s and 2010s. While coalitions of more than two parties were extremely rare in preceding decades, they have become common on the state level. These often include the liberal FDP and the Greens alongside one of the major parties, or "red–red–green" coalitions of the SPD, Greens, and The Left. In the eastern states, dwindling support for moderate parties has seen the rise of new forms of grand coalitions such as the Kenya coalition. The rise of populist parties also increases the time that it takes for a successful coalition to form. By 2016, the Greens were participating eleven governing coalitions on the state level in seven different constellations. During campaigns, parties often declare which coalitions or partners they prefer or reject. This tendency toward fragmentation also spread to the federal level, particularly during the 2021 federal election, which saw the CDU/CSU and SPD fall short of a combined majority of votes for the first time in history.
===India===
After India's Independence on 15 August 1947, the Indian National Congress, the major political party instrumental in the Indian independence movement, ruled the nation. The first Prime Minister, Jawaharlal Nehru, his successor Lal Bahadur Shastri, and the third Prime Minister, Indira Gandhi, were all members of the Congress party. However, Raj Narain, who had unsuccessfully contested an election against Indira from the constituency of Rae Bareli in 1971, lodged a case alleging electoral malpractice. In June 1975, Indira was found guilty and barred by the High Court from holding public office for six years. In response, a state of emergency was declared under the pretext of national security. The next election resulted in the formation of India's first ever national coalition government under the prime ministership of Morarji Desai, which was also the first non-Congress national government. It existed from 24 March 1977 to 15 July 1979, headed by the Janata Party, an amalgam of political parties opposed to the emergency imposed between 1975 and 1977. As the popularity of the Janata Party dwindled, Desai had to resign, and Chaudhary Charan Singh, a rival of his, became the fifth Prime Minister. However, due to lack of support, this coalition government did not complete its five-year term.
Congress returned to power in 1980 under Indira Gandhi, and later under Rajiv Gandhi as the sixth Prime Minister. However, the general election of 1989 once again brought a coalition government under National Front, which lasted until 1991, with two Prime Ministers, the second one being supported by Congress. The 1991 election resulted in a Congress-led stable minority government for five years. The eleventh parliament produced three Prime Ministers in two years and forced the country back to the polls in 1998. The first successful coalition government in India which completed a whole five-year term was the Bharatiya Janata Party (BJP)-led National Democratic Alliance with Atal Bihari Vajpayee as Prime Minister from 1999 to 2004. Then another coalition, the Congress-led United Progressive Alliance, consisting of 13 separate parties, ruled India for two terms from 2004 to 2014 with Manmohan Singh as PM. However, in the 16th general election in May 2014, the BJP secured a majority on its own (becoming the first party to do so since the 1984 election), and the National Democratic Alliance came into power, with Narendra Modi as Prime Minister. In 2019, Narendra Modi was re-elected as Prime Minister as the National Democratic Alliance again secured a majority in the 17th general election. India returned to an NDA led coalition government in 2024 as the BJP failed to achieve an outright majority.
===Indonesia===
As a result of the toppling of Suharto, political freedom is significantly increased. Compared to only three parties allowed to exist in the New Order era, a total of 48 political parties participated in the 1999 election and always a total of more than 10 parties in next elections. There are no majority winner of those elections and coalition governments are inevitable. The current government is a coalition of five parliamentary parties led by the major centre-right Gerindra to let governing big tent Advanced Indonesia Coalition.
===Ireland===
In Ireland, coalition governments are common; not since 1977 has a single party formed a majority government. Coalition governments to date have been led by either Fianna Fáil or Fine Gael. They have been joined in government by one or more smaller parties or independent members of parliament (TDs).
Ireland's first coalition government was formed after the 1948 general election, with five parties and independents represented at cabinet. Before 1989, Fianna Fáil had opposed participation in coalition governments, preferring single-party minority government instead. It formed a coalition government with the Progressive Democrats in that year.
The Labour Party has been in government on eight occasions. On all but one of those occasions, it was as a junior coalition party to Fine Gael. The exception was a government with Fianna Fáil from 1993 to 1994. The 29th Government of Ireland (2011–16), was a grand coalition of the two largest parties, as Fianna Fáil had fallen to third place in the Dáil.
The current government is a Fianna Fáil, Fine Gael and the Independents. Although Fianna Fáil and Fine Gael have been serving in government together since 2020, they haven't formed coalition before due to their different roots that goes back to Irish Civil War (1922–23).
===Israel===
A similar situation exists in Israel, which typically has at least 10 parties holding representation in the Knesset. The only faction to ever gain the majority of Knesset seats was Alignment, an alliance of the Labor Party and Mapam that held an absolute majority for a brief period from 1968 to 1969. Historically, control of the Israeli government has alternated between periods of rule by the right-wing Likud in coalition with several right-wing and religious parties and periods of rule by the center-left Labor in coalition with several left-wing parties. Ariel Sharon's formation of the centrist Kadima party in 2006 drew support from former Labor and Likud members, and Kadima ruled in coalition with several other parties.
Israel also formed a national unity government from 1984–1988. The premiership and foreign ministry portfolio were held by the head of each party for two years, and they switched roles in 1986.
===Japan===
In Japan, controlling a majority in the House of Representatives is enough to decide the election of the prime minister (=recorded, two-round votes in both houses of the National Diet, yet the vote of the House of Representatives decision eventually overrides a dissenting House of Councillors vote automatically after the mandatory conference committee procedure fails which, by precedent, it does without real attempt to reconcile the different votes). Therefore, a party that controls the lower house can form a government on its own. It can also pass a budget on its own. But passing any law (including important budget-related laws) requires either majorities in both houses of the legislature or, with the drawback of longer legislative proceedings, a two-thirds majority in the House of Representatives.
In recent decades, single-party full legislative control is rare, and coalition governments are the norm: Most governments of Japan since the 1990s and, as of 2020, all since 1999 have been coalition governments, some of them still fell short of a legislative majority. The Liberal Democratic Party (LDP) held a legislative majority of its own in the National Diet until 1989 (when it initially continued to govern alone), and between the 2016 and 2019 elections (when it remained in its previous ruling coalition). The Democratic Party of Japan (through accessions in the House of Councillors) briefly controlled a single-party legislative majority for a few weeks before it lost the 2010 election (it, too, continued to govern as part of its previous ruling coalition).
From the constitutional establishment of parliamentary cabinets and the introduction of the new, now directly elected upper house of parliament in 1947 until the formation of the LDP and the reunification of the Japanese Socialist Party in 1955, no single party formally controlled a legislative majority on its own. Only few formal coalition governments (46th, 47th, initially 49th cabinet) interchanged with technical minority governments and cabinets without technical control of the House of Councillors (later called "twisted Diets", nejire kokkai, when they were not only technically, but actually divided). But during most of that period, the centrist Ryokufūkai was the strongest overall or decisive cross-bench group in the House of Councillors, and it was willing to cooperate with both centre-left and centre-right governments even when it was not formally part of the cabinet; and in the House of Representatives, minority governments of Liberals or Democrats (or their precursors; loose, indirect successors to the two major pre-war parties) could usually count on support from some members of the other major conservative party or from smaller conservative parties and independents. Finally in 1955, when Hatoyama Ichirō's Democratic Party minority government called early House of Representatives elections and, while gaining seats substantially, remained in the minority, the Liberal Party refused to cooperate until negotiations on a long-debated "conservative merger" of the two parties were agreed upon, and eventually successful.
After it was founded in 1955, the Liberal Democratic Party dominated Japan's governments for a long period: The new party governed alone without interruption until 1983, again from 1986 to 1993 and most recently between 1996 and 1999. The first time the LDP entered a coalition government followed its third loss of its House of Representatives majority in the 1983 House of Representatives general election. The LDP-New Liberal Club coalition government lasted until 1986 when the LDP won landslide victories in simultaneous double elections to both houses of parliament.
There have been coalition cabinets where the post of prime minister was given to a junior coalition partner: the JSP-DP-Cooperativist coalition government in 1948 of prime minister Ashida Hitoshi (DP) who took over after his JSP predecessor Tetsu Katayama had been toppled by the left wing of his own party, the JSP-Renewal-Kōmei-DSP-JNP-Sakigake-SDF-DRP coalition in 1993 with Morihiro Hosokawa (JNP) as compromise PM for the Ichirō Ozawa-negotiated rainbow coalition that removed the LDP from power for the first time to break up in less than a year, and the LDP-JSP-Sakigake government that was formed in 1994 when the LDP had agreed, if under internal turmoil and with some defections, to bury the main post-war partisan rivalry and support the election of JSP prime minister Tomiichi Murayama in exchange for the return to government.
=== Malaysia ===
Ever since Malaysia gained independence in 1957, none of its federal governments have ever been controlled by a single political party. Due to the social nature of the country, the first federal government was formed by a three-party Alliance coalition, composed of the United Malays National Organisations (UMNO), the Malaysian Chinese Association (MCA), and the Malaysian Indian Congress (MIC). It was later expanded and rebranded as Barisan Nasional (BN), which includes parties representing the Malaysian states of Sabah and Sarawak.
The 2018 Malaysian general election saw the first non-BN coalition federal government in the country's electoral history, formed through an alliance between the Pakatan Harapan (PH) coalition and the Sabah Heritage Party (WARISAN). The federal government formed after the 2020–2022 Malaysian political crisis was the first to be established through coordination between multiple political coalitions. This occurred when the newly formed Perikatan Nasional (PN) coalition partnered with BN and Gabungan Parti Sarawak (GPS). In 2022 after its registration, Sabah-based Gabungan Rakyat Sabah (GRS) formally joined the government (though it had been a part of an informal coalition since 2020). The current government led by Prime Minister Anwar Ibrahim is composed of four political coalitions and 19 parties.
=== New Zealand ===
MMP was introduced in New Zealand in the 1996 election.
In order to get into power, parties need to get a total of 50% of the approximately (there can be more if an Overhang seat exists) 120 seats in parliament – 61. Since it is rare for a party to win a full majority, they must form coalitions with other parties. For example, from 1996 to 1998, the country was governed by a coalition of the National with the minor NZ First; from 1999 to 2002, a coalition of the Labour and the minor Alliance and with confidence and supply from the Green Party held power. Between 2017 and 2020, Labour, New Zealand First formed a Coalition Government with confidence and supply from the Green Party. During the 2023 general election, National won 49 seats, ACT won eleven and New Zealand First won eight formed a coalition government.
=== Spain ===
Since 2015, there are many more coalition governments than previously in municipalities, autonomous regions and, since 2020 (coming from the November 2019 Spanish general election), in the Spanish Government. There are two ways of conforming them: all of them based on a program and its institutional architecture, one consists on distributing the different areas of government between the parties conforming the coalition and the other one is, like in the Valencian Community, where the ministries are structured with members of all the political parties being represented, so that conflicts that may occur are regarding competences and not fights between parties.
Coalition governments in Spain had already existed during the 2nd Republic, and have been common in some specific Autonomous Communities since the 1980s. Nonetheless, the prevalence of two big parties overall has been eroded and the need for coalitions appears to be the new normal since around 2015.
=== Turkey ===
Turkey's first coalition government was formed after the 1961 general election, with two political parties and independents represented at cabinet. It was also Turkey's first grand coalition as the two largest political parties of opposing political ideologies (Republican People's Party and Justice Party) united. Between 1960 and 2002, 17 coalition governments were formed in Turkey. The media and the general public view coalition governments as unfavorable and unstable due to their lack of effectiveness and short lifespan. Following Turkey's transition to a presidential system in 2017, political parties focussed more on forming electoral alliances. Due to separation of powers, the government doesn't have to be formed by parliamentarians and therefore not obliged to result in a coalition government. However, the parliament can dissolve the cabinet if the parliamentary opposition is in majority.
===United Kingdom===
In the United Kingdom, coalition governments (sometimes known as "national governments") usually have only been formed at times of national crisis. The most prominent was the National Government of 1931 to 1940. There were multi-party coalitions during both world wars. Apart from this, when no party has had a majority, minority governments normally have been formed with one or more opposition parties agreeing to vote in favour of the legislation which governments need to function: for instance the Labour government of James Callaghan formed a pact with the Liberals from March 1977 until July 1978, following a series of by-election defeats had eroded Labour's majority of three seats which had been gained at the October 1974 election. However, in the run-up to the 1997 general election, Labour opposition leader Tony Blair was in talks with Liberal Democrat leader Paddy Ashdown about forming a coalition government if Labour failed to win a majority at the election; but there proved to be no need for a coalition as Labour won the election by a landslide. The 2010 general election resulted in a hung parliament (Britain's first for 36 years), and the Conservatives, led by David Cameron, which had won the largest number of seats, formed a coalition with the Liberal Democrats in order to gain a parliamentary majority, ending 13 years of Labour government. This was the first time that the Conservatives and Lib Dems had made a power-sharing deal at Westminster. It was also the first full coalition in Britain since 1945, having been formed 70 years virtually to the day after the establishment of Winston Churchill's wartime coalition,
Labour and the Liberal Democrats have entered into a coalition twice in the Scottish Parliament, as well as twice in the Welsh Assembly.
=== Uruguay ===
Since the 1989 election, there have been 4 coalition governments, all including at least both the conservative National Party and the liberal Colorado Party. The first one was after the election of the blanco Luis Alberto Lacalle and lasted until 1992 due to policy disagreements, the longest lasting coalition was the Colorado-led coalition under the second government of Julio María Sanguinetti, in which the national leader Alberto Volonté was frequently described as a "Prime Minister", the next coalition (under president Jorge Batlle) was also Colorado-led, but it lasted only until after the 2002 Uruguay banking crisis, when the blancos abandoned the government. Following the 2019 Uruguayan general election, the blanco Luis Lacalle Pou formed the coalición multicolor, composed of his own National Party, the liberal Colorado Party, the eclectic Open Cabildo and the center left Independent Party.
==Support and criticism==
Advocates of proportional representation suggest that a coalition government leads to more consensus-based politics, as a government comprising differing parties (often based on different ideologies) need to compromise about governmental policy. Another stated advantage is that a coalition government better reflects the popular opinion of the electorate within a country; this means, for instance, that the political system contains just one majority-based mechanism. Contrast this with district voting in which the majority mechanism occurs twice: first, the majority of voters pick the representative and, second, the body of representatives make a subsequent majority decision. The doubled majority decision undermines voter support for that decision. The benefit of proportional representation is that it contains that majority mechanism just once. Additionally, coalition partnership may play an important role in moderating the level of affective polarization over parties, that is, the animosity and hostility against the opponent party identifiers/supporters.
Those who disapprove of coalition governments believe that such governments have a tendency to be fractious and prone to disharmony, as their component parties hold differing beliefs and thus may not always agree on policy. Sometimes the results of an election mean that the coalitions which are mathematically most probable are ideologically infeasible, for example in Flanders or Northern Ireland. A second difficulty might be the ability of minor parties to play "kingmaker" and, particularly in close elections, gain far more power in exchange for their support than the size of their vote would otherwise justify.
Germany is the largest nation ever to have had proportional representation during the interbellum. After WW II, the German system, district based but then proportionally adjusted afterward, contains a threshold that keeps the number of parties limited. The threshold is set at five percent, resulting in empowered parties with at least a minimum amount of political gravity.
Coalition governments have also been criticized for sustaining a consensus on issues when disagreement and the consequent discussion would be more fruitful. To forge a consensus, the leaders of ruling coalition parties can agree to silence their disagreements on an issue to unify the coalition against the opposition. The coalition partners, if they control the parliamentary majority, can collude to make the parliamentary discussion on the issue irrelevant by consistently disregarding the arguments of the opposition and voting against the opposition's proposals — even if there is disagreement within the ruling parties about the issue. However, in winner-take-all this seems always to be the case.
Powerful parties can also act in an oligocratic way to form an alliance to stifle the growth of emerging parties. Of course, such an event is rare in coalition governments when compared to two-party systems, which typically exist because of stifling of the growth of emerging parties, often through discriminatory nomination rules regulations and plurality voting systems, and so on.
A single, more powerful party can shape the policies of the coalition disproportionately. Smaller or less powerful parties can be intimidated to not openly disagree. In order to maintain the coalition, they would have to vote against their own party's platform in the parliament. If they do not, the party has to leave the government and loses executive power. However, this is contradicted by the "kingmaker" factor mentioned above.
Finally, a strength that can also be seen as a weakness is that proportional representation puts the emphasis on collaboration. All parties involved are looking at the other parties in the best light possible, since they may be (future) coalition partners. The pendulum may therefore show less of a swing between political extremes. Still, facing external issues may then also be approached from a collaborative perspective, even when the outside force is not benevolent.
==Legislative coalitions and agreements ==
A legislative coalition or voting coalition is when political parties in a legislature align on voting to push forward specific policies or legislation, but do not engage in power-sharing of the executive branch like in coalition governments.
In a parliamentary system, political parties may form a confidence and supply arrangement, pledging to support the governing party on legislative bills and motions that carry a vote of confidence. Unlike a coalition government, which is a more formalised partnership characterised by the sharing of the executive branch, a confidence and supply arrangement does not entail executive "power-sharing". Instead, it involves the governing party supporting specific proposals and priorities of the other parties in the arrangement, in return for their continued support on motions of confidence.
===United States===
In the United States, political parties have formed legislative coalitions in the past in order to push forward specific policies or legislation in the United States Congress. The most recent legislative coalition took place in 1917, a coalition was formed between members of the Democratic Party, Progressive Party and Socialist Party of America to elect Champ Clark as the speaker of the United States House of Representatives.
More recently, during the 118th Congress, an informal legislative coalition formed between Democrats and mainline Republicans to pass critical legislation opposed by the Freedom Caucus, an extreme right-wing faction controlling a minority of seats in the Republican Conference.
A coalition government, in which "power-sharing" of executive offices is performed, has not occurred in the United States. The norms that allow coalition governments to form and persist do not exist in the United States.
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"Second Nakasone Cabinet",
"Gabungan Parti Sarawak",
"Fianna Fáil",
"Confidence and supply",
"Paddy Ashdown",
"Stauning II Cabinet",
"Canada's History",
"Third Yoshida Cabinet",
"consensus democracy",
"Thailand",
"Australian Greens",
"Narendra Modi",
"House of Representatives (Japan)",
"New Liberal Club",
"Politics of Finland",
"Knesset",
"Jyrki Katainen's cabinet",
"Manmohan Singh",
"minority government",
"Chaudhary Charan Singh",
"multi-party system",
"Malaysia",
"Country Liberal Party",
"Bharatiya Janata Party",
"Power sharing",
"grand coalition",
"Luis Lacalle Pou",
"ja:第3次吉田内閣",
"electoral alliance",
"Duff Pattullo",
"Nathaniel P. Banks",
"Christopher Moore (Canadian historian)",
"1999 Indonesian legislative election",
"Thorvald Stauning",
"two-party system",
"Malaysian Chinese Association",
"2020–2022 Malaysian political crisis",
"Pakistan",
"List of countries with coalition governments",
"List of political parties in Armenia",
"United Farmers of Manitoba",
"Liberal Democrats (UK)",
"Political coalition",
"United Farmers of Ontario",
"BC Social Credit Party",
"1983 Japanese general election",
"Majoritarian representation",
"Politics of Australia",
"Social Democrats (Denmark)",
"vote of no confidence",
"Australian Labor Party",
"Liberal Party of Canada",
"Ryokufūkai (1947–60)",
"Lebanon",
"Scottish Parliament",
"1989 Indian general election",
"CDU/CSU",
"National Diet",
"Northern Territory",
"Legitimacy (political)",
"1935 Danish Folketing election",
"The Independent",
"Gerindra Party",
"Bloc Québécois",
"United front",
"Politics of Canada",
"Stephen Harper",
"Majority government",
"Greece",
"Lok Sabha",
"Germany",
"New Zealand First",
"Cabinet of Japan",
"Mette Frederiksen",
"1948 Irish general election",
"Ukraine",
"Benelux",
"Colorado Party (Uruguay)",
"Hosokawa Cabinet",
"Lorne Calvert",
"Lib–Lab pact",
"Turkey",
"India",
"big tent",
"Rae Bareli Lok Sabha constituency",
"Paavo Lipponen's second cabinet",
"Mapam",
"Tomiichi Murayama",
"Deutsche Welle",
"Venstre (Denmark)",
"Freedom Caucus",
"Trinidad and Tobago",
"Winston Churchill",
"cs:Koalice",
"2019 Uruguayan general election",
"Red–red–green coalition",
"Category:Political party alliances",
"Sabah Heritage Party",
"Nash equilibrium",
"Politics of India",
"Socialist Party (Belgium)",
"Italy",
"Brussels",
"MMP representation",
"European Parliament",
"Parti bleu",
"World War II",
"65th United States Congress",
"caretaker government",
"Liberal Democratic Party (Japan)",
"118th Congress",
"Paavo Lipponen's first cabinet",
"speaker of the United States House of Representatives",
"proportional representation",
"Governor General of Canada",
"Jamaica coalition (politics)",
"Socialist People's Party (Denmark)",
"centre-right",
"Victoria (Australia)",
"landslide victory",
"Tetsu Katayama",
"ACT Government",
"Roy Romanow",
"House of Councillors (Japan)",
"Ichirō Ozawa",
"Workers' Party of Belgium",
"Government",
"Saskatchewan Liberal Party",
"Liberal Party (UK)"
] |
6,038 |
Chemical engineering
|
Chemical engineering is an engineering field which deals with the study of the operation and design of chemical plants as well as methods of improving production. Chemical engineers develop economical commercial processes to convert raw materials into useful products. Chemical engineering uses principles of chemistry, physics, mathematics, biology, and economics to efficiently use, produce, design, transport and transform energy and materials. The work of chemical engineers can range from the utilization of nanotechnology and nanomaterials in the laboratory to large-scale industrial processes that convert chemicals, raw materials, living cells, microorganisms, and energy into useful forms and products. Chemical engineers are involved in many aspects of plant design and operation, including safety and hazard assessments, process design and analysis, modeling, control engineering, chemical reaction engineering, nuclear engineering, biological engineering, construction specification, and operating instructions.
Chemical engineers typically hold a degree in Chemical Engineering or Process Engineering. Practicing engineers may have professional certification and be accredited members of a professional body. Such bodies include the Institution of Chemical Engineers (IChemE) or the American Institute of Chemical Engineers (AIChE). A degree in chemical engineering is directly linked with all of the other engineering disciplines, to various extents.
==Etymology==
A 1996 article cites James F. Donnelly for mentioning an 1839 reference to chemical engineering in relation to the production of sulfuric acid. In the same paper, however, George E. Davis, an English consultant, was credited with having coined the term. Davis also tried to found a Society of Chemical Engineering, but instead, it was named the Society of Chemical Industry (1881), with Davis as its first secretary. The History of Science in United States: An Encyclopedia puts the use of the term around 1890. "Chemical engineering", describing the use of mechanical equipment in the chemical industry, became common vocabulary in England after 1850. By 1910, the profession, "chemical engineer," was already in common use in Britain and the United States.
==History==
===New concepts and innovations===
In the 1940s, it became clear that unit operations alone were insufficient in developing chemical reactors. While the predominance of unit operations in chemical engineering courses in Britain and the United States continued until the 1960s, transport phenomena started to receive greater focus. Along with other novel concepts, such as process systems engineering (PSE), a "second paradigm" was defined. Transport phenomena gave an analytical approach to chemical engineering while PSE focused on its synthetic elements, such as those of a control system and process design. Developments in chemical engineering before and after World War II were mainly incited by the petrochemical industry; however, advances in other fields were made as well. Advancements in biochemical engineering in the 1940s, for example, found application in the pharmaceutical industry, and allowed for the mass production of various antibiotics, including penicillin and streptomycin. Meanwhile, progress in polymer science in the 1950s paved way for the "age of plastics".
===Safety and hazard developments===
Concerns regarding large-scale chemical manufacturing facilities' safety and environmental impact were also raised during this period. Silent Spring, published in 1962, alerted its readers to the harmful effects of DDT, a potent insecticide. The 1974 Flixborough disaster in the United Kingdom resulted in 28 deaths, as well as damage to a chemical plant and three nearby villages. 1984 Bhopal disaster in India resulted in almost 4,000 deaths. These incidents, along with other incidents, affected the reputation of the trade as industrial safety and environmental protection were given more focus. In response, the IChemE required safety to be part of every degree course that it accredited after 1982. By the 1970s, legislation and monitoring agencies were instituted in various countries, such as France, Germany, and the United States. In time, the systematic application of safety principles to chemical and other process plants began to be considered a specific discipline, known as process safety.
===Recent progress===
Advancements in computer science found applications for designing and managing plants, simplifying calculations and drawings that previously had to be done manually. The completion of the Human Genome Project is also seen as a major development, not only advancing chemical engineering but genetic engineering and genomics as well. Chemical engineering principles were used to produce DNA sequences in large quantities.
==Concepts==
Chemical engineering involves the application of several principles. Key concepts are presented below.
===Plant design and construction===
Chemical engineering design concerns the creation of plans, specifications, and economic analyses for pilot plants, new plants, or plant modifications. Design engineers often work in a consulting role, designing plants to meet clients' needs. Design is limited by several factors, including funding, government regulations, and safety standards. These constraints dictate a plant's choice of process, materials, and equipment.
Plant construction is coordinated by project engineers and project managers, depending on the size of the investment. A chemical engineer may do the job of project engineer full-time or part of the time, which requires additional training and job skills or act as a consultant to the project group. In the USA the education of chemical engineering graduates from the Baccalaureate programs accredited by ABET do not usually stress project engineering education, which can be obtained by specialized training, as electives, or from graduate programs. Project engineering jobs are some of the largest employers for chemical engineers.
===Process design and analysis===
A unit operation is a physical step in an individual chemical engineering process. Unit operations (such as crystallization, filtration, drying and evaporation) are used to prepare reactants, purifying and separating its products, recycling unspent reactants, and controlling energy transfer in reactors. On the other hand, a unit process is the chemical equivalent of a unit operation. Along with unit operations, unit processes constitute a process operation. Unit processes (such as nitration, hydrogenation, and oxidation involve the conversion of materials by biochemical, thermochemical and other means. Chemical engineers responsible for these are called process engineers.
Process design requires the definition of equipment types and sizes as well as how they are connected and the materials of construction. Details are often printed on a Process Flow Diagram which is used to control the capacity and reliability of a new or existing chemical factory.
Education for chemical engineers in the first college degree 3 or 4 years of study stresses the principles and practices of process design. The same skills are used in existing chemical plants to evaluate the efficiency and make recommendations for improvements.
===Transport phenomena===
Modeling and analysis of transport phenomena is essential for many industrial applications. Transport phenomena involve fluid dynamics, heat transfer and mass transfer, which are governed mainly by momentum transfer, energy transfer and transport of chemical species, respectively. Models often involve separate considerations for macroscopic, microscopic and molecular level phenomena. Modeling of transport phenomena, therefore, requires an understanding of applied mathematics.
==Applications and practice==
Chemical engineers develop economic ways of using materials and energy. Chemical engineers use chemistry and engineering to turn raw materials into usable products, such as medicine, petrochemicals, and plastics on a large-scale, industrial setting. They are also involved in waste management and research. Both applied and research facets could make extensive use of computers.
Chemical engineers may be involved in industry or university research where they are tasked with designing and performing experiments, by scaling up theoretical chemical reactions, to create better and safer methods for production, pollution control, and resource conservation. They may be involved in designing and constructing plants as a project engineer. Chemical engineers serving as project engineers use their knowledge in selecting optimal production methods and plant equipment to minimize costs and maximize safety and profitability. After plant construction, chemical engineering project managers may be involved in equipment upgrades, troubleshooting, and daily operations in either full-time or consulting roles.
|
[
"physics",
"streptomycin",
"sulfuric acid",
"heat transfer",
"DDT",
"Polymer",
"Chemical technologist",
"Semiconductor device fabrication",
"graduate programs",
"fluid dynamics",
"Earthquake engineering",
"control system",
"Oil exploration",
"Natural environment",
"penicillin",
"Process miniaturization",
"Cost estimation",
"polymer science",
"Chemical process modeling",
"Crystallization processes",
"nanomaterials",
"process engineer",
"Computational fluid dynamics",
"Paper engineering",
"Biomolecular engineering",
"biological engineering",
"process safety",
"chemistry",
"Process engineering",
"momentum transfer",
"project engineering",
"List of chemical engineers",
"biology",
"Process control",
"biochemical engineering",
"energy transfer",
"chemical reactor",
"Process safety",
"Corrosion engineering",
"Industrial gas",
"molecular",
"Bioinformatics",
"Nanotechnology",
"Indian Institute of Chemical Engineers",
"Br. J. Hist. Sci.",
"computer science",
"Pharmaceutical engineering",
"Water technology",
"Transport phenomena",
"List of industrial disasters",
"Institution of Chemical Engineers",
"waste management",
"petrochemical industry",
"Transport phenomena (engineering & physics)",
"antibiotic",
"Nuclear reprocessing",
"engineering",
"Electrochemical engineering",
"Textile engineering",
"Separation process",
"Catalysis",
"Rice University",
"Microfluidics",
"Bioprocess engineering",
"Heat transfer",
"control engineering",
"Cheminformatics",
"English Engineering units",
"Oil refinery",
"Chemical weapons",
"pilot plant",
"pharmaceutical industry",
"Plastics engineering",
"Ceramic",
"Mass transfer",
"Electrochemistry",
"biochemical",
"Silent Spring",
"Process Flow Diagram",
"microscopic scale",
"Industrial catalysts",
"Thermodynamics",
"Environmental engineering",
"George E. Davis",
"Chemical Institute of Canada",
"mass transfer",
"systems analysis",
"nanotechnology",
"insecticide",
"Metallurgy",
"industrial safety",
"Human Genome Project",
"oxidation",
"Chemical reactor",
"Unit operations",
"Fischer Tropsch synthesis",
"American Institute of Chemical Engineers",
"drying",
"separation of mixture",
"environmental protection",
"genetic engineering",
"evaporation",
"Process manufacturing",
"nitration",
"project engineer",
"crystallization",
"chemical species",
"modeling and simulation",
"Fluid dynamics",
"Materials science",
"Chemical reactor materials selection",
"Biological engineering",
"Society of Chemical Industry",
"DNA sequences",
"Flixborough disaster",
"process systems engineering",
"National Organization for the Professional Advancement of Black Chemists and Chemical Engineers",
"Natural gas processing",
"Economics",
"Membrane technology",
"List of chemical engineering societies",
"mass production",
"Process development",
"Education for Chemical Engineers",
"thermochemical",
"Outline of chemical engineering",
"macroscopic scale",
"European Federation of Chemical Engineering",
"Transport Phenomena (book)",
"Bhopal disaster",
"Petroleum engineering",
"Biotechnology",
"chemical plant",
"process engineering",
"genomics",
"ABET",
"Mineral processing",
"Industrial chemistry",
"economics",
"nuclear engineering",
"Biotechnology engineering",
"Molecular engineering",
"Gasification",
"Biochemical engineering",
"Biomedical engineering",
"Chemical engineer",
"Distillation",
"chemical reaction engineering",
"John Wiley & Sons",
"Process design (chemical engineering)",
"Food engineering",
"Fuel cell",
"List of chemical process simulators",
"Syngas production",
"mathematics",
"filtration"
] |
6,041 |
List of comedians
|
A comedian is one who entertains through comedy, such as jokes and other forms of humour. Following is a list of comedians, comedy groups, and comedy writers.
==Comedians==
(sorted alphabetically by surname)
===A===
Rose Abdoo (born 1962)
Raymond Ablack (born 1989)
John Aboud (born 1973)
Silvia Abril (born 1971)
James Acaster (born 1985)
Jayde Adams (born 1984)
Kev Adams (born 1991)
Mark Addy (born 1964)
Lolly Adefope (born 1990)
Demi Adejuyigbe (born 1992)
Pamela Adlon (born 1966)
James Adomian (born 1980)
Scott Adsit (born 1965)
Bayani Agbayani (born 1969)
Steve Agee (born 1969)
Alex Agnew (born 1973)
Rubén Aguirre (1934–2016)
Dan Ahdoot (born 1981)
Caroline Aherne (1963–2016)
Ahmed Ahmed (born 1970)
Sohail Ahmed (born 1963)
Franklyn Ajaye (born 1949)
Anna Akana (born 1989)
Malin Akerman (born 1978)
Nawaal Akram (born 1990)
Nasser Al Qasabi (born 1963)
Lori Alan (born 1966)
Joe Alaskey (1952–2016)
Carlos Alazraqui (born 1962)
Rory Albanese (born 1977)
Lou Albano (1933–2009)
Eddie Albert (1906–2005)
Ogie Alcasid (born 1967)
Alan Alda (born 1936)
Jason Alexander (born 1959)
Mo Alexander (born 1970)
Ted Alexandro (born 1969)
Allan K. (born 1958)
Barbara Jo Allen (1906–1974)
Dave Allen (1936–2005)
Gracie Allen (1895–1964)
Krista Allen (born 1971)
Leo Allen (born 1972)
Marty Allen (1922–2018)
Steve Allen (1921–2000)
Tim Allen (born 1953)
Woody Allen (born 1935)
Kirstie Alley (1951–2022)
Kevin Allison (born 1970)
Stephanie Allynne (born 1986)
Anabel Alonso (born 1964)
Cristela Alonzo (born 1979)
Jeff Altman (born 1951)
Brian Jordan Alvarez (born 1987)
The Amazing Johnathan (1958–2022)
Utkarsh Ambudkar (born 1983)
Don Ameche (1908–1993)
Robbie Amell (born 1988)
Mo Amer (born 1981)
John Amos (1939–2024)
Megan Amram (born 1987)
Simon Amstell (born 1979)
Morey Amsterdam (1908–1996)
Andrea Anders (born 1975)
Siw Anita Andersen (born 1966)
Amy Anderson (born 1972)
Anthony Anderson (born 1970)
Blake Anderson (born 1984)
Harry Anderson (1952–2018)
James Anderson
Louie Anderson (1953–2022)
Wil Anderson (born 1974)
Eric André (born 1983)
Alex Anfanger (born 1985)
Michael Angarano (born 1987)
Lucia Aniello (born 1983)
Jennifer Aniston (born 1969)
Aziz Ansari (born 1983)
Ant (born 1967)
Dave Anthony (born 1967)
Craig Anton (born 1962)
Judd Apatow (born 1967)
Ingo Appelt (born 1967)
Christina Applegate (born 1971)
John Aprea (born 1941)
Carly Aquilino (born 1990)
Nicole Arbour (born 1985)
Lisa Arch (born 1971)
Roscoe "Fatty" Arbuckle (1887–1933)
Geoffrey Arend (born 1978)
Lesley Arfin (born 1979)
Marcella Arguello (born 1985)
Fred Armisen (born 1966)
Alexander Armstrong (born 1970)
Desi Arnaz (1917–1986)
Will Arnett (born 1970)
David A. Arnold (1968–2022)
Tichina Arnold (born 1969)
Tom Arnold (born 1959)
David Arquette (born 1971)
Bea Arthur (1922–2009)
Aaron Aryanpur (born 1978)
Katie Aselton (born 1978)
Erica Ash (1977–2024)
Lauren Ash (born 1983)
Annaleigh Ashford (born 1985)
Arthur Askey (1900–1982)
Ed Asner (1929–2021)
Sean Astin (born 1971)
Skylar Astin (born 1987)
Emily Atack (born 1989)
Anthony Atamanuik (born 1974)
Aristotle Athari (born 1991)
Essence Atkins (born 1972)
Rowan Atkinson (born 1955)
Helen Atkinson-Wood (born 1955)
Dave Attell (born 1965)
Michael "Atters" Attree (born 1965)
Scott Aukerman (born 1970)
Phil Austin (1941–2015)
Joe Avati (born 1974)
Shondrella Avery (born 1971)
Awkwafina (born 1988)
Ayelet the Kosher Komic
Dan Aykroyd (born 1952)
Peter Aykroyd (1955–2021)
Damali Ayo (born 1972)
Richard Ayoade (born 1977)
Hank Azaria (born 1964)
Hannan Azlan
Valerie Azlynn (born 1980)
===B===
Baba Ali (born 1975)
Dirk Bach (1961–2012)
King Bach (born 1988)
Jim Backus (1913–1989)
Diedrich Bader (born 1966)
Max Baer Jr. (born 1937)
Ross Bagley (born 1988)
Tim Bagley (born 1957)
Iris Bahr (born 1977)
Ainsley Bailey (born 1992)
Ben Bailey (born 1970)
Bill Bailey (born 1965)
Conrad Bain (1923–2013)
Scott Baio (born 1960)
Nick Bakay (born 1959)
Bobbie Baker
Leslie David Baker (born 1958)
Rosebud Baker (born 1985)
Sarah Baker (born 1973)
Dan Bakkedahl (born 1969)
Carlos Balá (1925–2022)
Bob Balaban (born 1945)
Josiane Balasko (born 1950)
Hugo Egon Balder (born 1950)
Alec Baldwin (born 1958)
Dougie Baldwin (born 1996)
Lucille Ball (1911–1989)
Kaye Ballard (1925–2019)
Reginald Ballard (born 1965)
Tom Ballard (born 1989)
Paolo Ballesteros (born 1982)
Colleen Ballinger (born 1986)
Tim Baltz (born 1981)
Maria Bamford (born 1970)
Eric Bana (born 1968)
Elizabeth Banks (born 1974)
Morwenna Banks (born 1961)
Zach Barack (born 1995)
Edward Barbanell (born 1977)
Celeste Barber (born 1982)
Ralph Barbosa (born 1996)
Nate Bargatze (born 1979)
Robert Baril (born 1986/1987)
Ike Barinholtz (born 1977)
Jon Barinholtz (born 1982)
Arj Barker (born 1974)
Ronnie Barker (1929–2005)
Caitlin Barlow (born 1983)
Angela Barnes (born 1976)
Cooper Barnes (born 1979)
Kevin Barnett (1986–2019)
Ty Barnett (born 1975)
Vince Barnett (1902–1977)
Sandy Baron (1937–2001)
Anita Barone (born 1964)
Roseanne Barr (born 1952)
Julian Barratt (born 1968)
Amanda Barrie (born 1935)
Kenya Barris (born 1974)
Carl Barron (born 1968)
Todd Barry (born 1964)
Mario Barth (born 1972)
Justin Bartha (born 1978)
Jay Baruchel (born 1982)
Frank-Markus Barwasser (born 1960)
David Alan Basche (born 1968)
Jason Bateman (born 1969)
Angelique Bates (born 1980)
David Batra (born 1972)
Brian Baumgartner (born 1972)
Eric Bauza (born 1979)
Stanley Baxter (born 1926)
Vanessa Bayer (born 1981)
Matthew Baynton (born 1980)
Wally Bayola (born 1972)
Carter Bays (born 1975)
Aisling Bea (born 1984)
Allyce Beasley (born 1954)
Anne Beatts (1947–2021)
Lucy Beaumont (born 1983)
David Beck (born 1970)
Alison Becker (born 1977)
Jürgen Becker (born 1959)
Rob Beckett (born 1986)
Samantha Bee (born 1969)
Beetlejuice (born 1968)
Joy Behar (born 1942)
Natasha Behnam (born 1996)
Greg Behrendt (born 1963)
Beth Behrs (born 1985)
Ashley Bell (born 1986)
Jillian Bell (born 1984)
Lake Bell (born 1979)
Tone Bell (born 1983)
W. Kamau Bell (born 1973)
Bill Bellamy (born 1965)
Ryan Belleville (born 1979)
Jim Belushi (born 1954)
John Belushi (1949–1982)
Richard Belzer (1944–2023)
Bea Benaderet (1906–1968)
H. Jon Benjamin (born 1966)
Owen Benjamin (born 1980)
Beck Bennett (born 1984)
Jeff Bennett (born 1962)
Ron Bennington (born 1958)
D.C. Benny
Jack Benny (1894–1974)
Doug Benson (born 1964)
Alec Berg (born 1969)
Candice Bergen (born 1946)
Edgar Bergen (1903–1978)
Tom Bergeron (born 1955)
Peter Paul Bergman (1939–2012)
Kate Berlant (born 1987)
Milton Berle (1908–2002)
Andy Berman (born 1968)
Shelley Berman (1925–2017)
Crystal Bernard (born 1961)
Sandra Bernhard (born 1955)
Matt Berry (born 1974)
Joe Besser (1907–1988)
Matt Besser (born 1967)
Ilka Bessin (born 1971)
Beetlejuice (born 1968)
Danny Bhoy (born 1976)
Mayim Bialik (born 1975)
Leslie Bibb (born 1974)
Craig Bierko (born 1964)
Jason Biggs (born 1978)
Mike Birbiglia (born 1978)
Simon Bird (born 1984)
Mary Birdsong (born 1968)
Des Bishop (born 1975)
Joey Bishop (1918–2007)
John Bishop (born 1966)
Kevin Bishop (born 1980)
Danielle Bisutti (born 1976)
Ashley Nicole Black (born 1985)
Jack Black (born 1969)
Jordan Black (born 1970)
Lewis Black (born 1948)
Michael Ian Black (born 1971)
Michael Blackson (born 1972)
Mark Blankfield (1950–2024)
Hamish Blake (born 1981)
Susanne Blakeslee (born 1956)
Mel Blanc (1908–1989)
Maria Blasucci (born 1986)
Brian Blessed (born 1936)
Rich Blomquist (born 1977)
Rachel Bloom (born 1987)
Ben Blue (1901–1975)
Josh Blue (born 1978)
Sarayu Blue (born 1975)
Amir Blumenfeld (born 1983)
John Bluthal (1929–2018)
Raphael Bob-Waksberg (born 1984)
Alonzo Bodden (born 1967)
Steve Bodow
Mirja Boes (born 1971)
Catherine Bohart (born 1988)
Danny Bonaduce (born 1959)
Sue Bond (born 1945)
Peter Bonerz (born 1938)
Bobby Bones (born 1980)
Wigald Boning (born 1967)
Sonny Bono (1935–1998)
Elayne Boosler (born 1952)
Joel Kim Booster (born 1988)
Connie Booth (born 1940)
Tato Bores (1927–1996)
Flula Borg (born 1982)
Victor Borge (1909–2000)
Ernest Borgnine (1917–2012)
Kyle Bornheimer (born 1975)
Alex Borstein (born 1971)
Loren Bouchard (born 1969)
Lilan Bowden (born 1985)
Andrew Bowen (born 1972)
Julie Bowen (born 1970)
Byron Bowers (born 1978)
John Ross Bowie (born 1971)
Max Boyce (born 1945)
Steven Boyer (born 1979)
Frankie Boyle (born 1972)
Peter Boyle (1935–2006)
Fern Brady
Wayne Brady (born 1972)
Harriet Braine
Zach Braff (born 1975)
Joey Bragg (born 1996)
Patrick Brammall (born 1976)
Jo Brand (born 1957)
Russell Brand (born 1975)
Betsy Brandt (born 1973)
Guy Branum (born 1975)
Larry Brantley (born 1966)
John Branyan (born 1965)
Matt Braunger (born 1974)
Kurt Braunohler (born 1976)
Daniel Breaker (born 1980)
El Brendel (1890–1964)
Josh Brener (born 1984)
Kevin Brennan (born 1960)
Neal Brennan (born 1974)
David Brenner (1936–2014)
Jim Breuer (born 1967)
Blonde Brewer
Paget Brewster (born 1969)
Fanny Brice (1891–1951)
Todd Bridges (born 1965)
Alison Brie (born 1982)
Sabrina Brier (born 1994)
Richard Briers (1934–2013)
Joe Bob Briggs (born 1953)
Awra Briguela (born 2004)
Patrick Bristow (born 1962)
Janine Brito
Paul Brittain (born 1977)
Doug Brochu (born 1990)
Matthew Broderick (born 1962)
Adam Brody (born 1979)
Jimmy Brogan (born 1948)
Benjy Bronk (born 1967)
Tim Brooke-Taylor (1940–2020)
Albert Brooks (born 1947)
Foster Brooks (1912–2001)
James L. Brooks (born 1940)
Max Brooks (born 1972)
Mel Brooks (born 1926)
Brittany Broski (born 1997)
Brother Theodore (1906–2001)
Alan Brough (born 1967)
A. Whitney Brown (born 1952)
Alton Brown (born 1962)
Candace Brown (born 1980)
Clancy Brown (born 1959)
Joe E. Brown (1891–1973)
Kevin Brown (born 1972)
Wally Brown (1904–1961)
Cocoa Brown (born 1972)
Yvette Nicole Brown (born 1971)
Carrie Brownstein (born 1974)
Lenny Bruce (1925–1966)
Hazel Brugger (born 1993)
Quinta Brunson (born 1989)
Aidy Bryant (born 1987)
Cubby Bryant (born 1971)
Rob Brydon (born 1965)
Andy Buckley (born 1965)
James Buckley (born 1987)
Sophie Buddle (born 1994)
Herlene Budol (born 1999)
Jim J. Bullock (born 1955)
Sandra Bullock (born 1964)
Vicco von Bülow (1923–2011)
Rodger Bumpass (born 1951)
Michael Bunin (born 1970)
John Bunny (1863–1915)
David Burd (aka) Lil Dicky (born 1988)
Hannibal Buress (born 1983)
Tituss Burgess (born 1979)
Delta Burke (born 1956)
Kathy Burke (born 1964)
Carol Burnett (born 1933)
Bo Burnham (born 1990)
Burnie Burns (born 1973)
George Burns (1896–1996)
Jack Burns (1933–2020)
Regan Burns (born 1968)
Sarah Burns (born 1981)
Bill Burr (born 1968)
Maryedith Burrell (born 1952)
Ty Burrell (born 1967)
Abe Burrows (1910–1985)
James Burrows (born 1940)
Steve Buscemi (born 1957)
Adam Busch (born 1978)
Mikey Bustos (born 1981)
River Butcher (born 1982)
Michelle Buteau (born 1977)
Brett Butler (born 1958)
Red Buttons (1919–2006)
Adam Buxton (born 1969)
Ruth Buzzi (born 1936)
Nicole Byer (born 1986)
John Byner (born 1938)
Ed Byrne (born 1972)
Jason Byrne (born 1972)
P. J. Byrne (born 1974)
Rose Byrne (born 1979)
Steve Byrne (born 1974)
===C===
Louis C.K. (born 1967)
Vladimir Caamaño (born 1979)
Mike Cabellon
Angelique Cabral (born 1979)
Liz Cackowski
Sid Caesar (1922–2014)
Frank Caeti (born 1973)
Frank Caliendo (born 1975)
Charlie Callas (1924–2011)
Bryan Callen (born 1967)
Frances Callier (born 1969)
Kirk Cameron (born 1970)
Rhona Cameron (born 1965)
Jaime Camil (born 1973)
Anna Camp (born 1982)
Colleen Camp (born 1953)
Adam Campbell (born 1980)
Archie Campbell (1914–1987)
Bruce Campbell (born 1958)
Craig Campbell (born 1969)
Heather Anne Campbell
Larry Joe Campbell (born 1970)
Neil Campbell
Sam Campbell (born 1991)
Tisha Campbell (born 1968)
Maria Canals-Barrera (born 1966)
John Candy (1950–1994)
Bobby Cannavale (born 1970)
Kay Cannon (born 1974)
Nick Cannon (born 1980)
Judy Canova (1913–1983)
Melai Cantiveros (born 1988)
Mario Cantone (born 1959)
Nicolas Cantu (born 2003)
John Caparulo (born 1975)
Blaine Capatch (born 1965)
Lizzy Caplan (born 1982)
Twink Caplan (born 1947)
Scott Capurro (born 1962)
Perry Caravello (born 1963)
Matty Cardarople (born 1983)
Linda Cardellini (born 1975)
D'Arcy Carden (born 1980)
Nancy Carell (born 1966)
Steve Carell (born 1962)
Anthony Carelli (aka) Santino Marella (born 1974)
Drew Carey (born 1958)
Liz Carey (born 1978)
Maggie Carey (born 1975)
George Carl (1916–2000)
George Carlin (1937–2008)
Jordan Carlos (born 1978)
Urzila Carlson (born 1976)
Jerrod Carmichael (born 1987)
Alan Carney (1909–1973)
Art Carney (1918–2003)
Adam Carolla (born 1964)
Alan Carr (born 1976)
Jimmy Carr (born 1972)
Jim Carrey (born 1962)
Rodney Carrington (born 1968)
Jack Carroll (born 1998)
Pat Carroll (1927–2022)
Carrot Top (Scott Thompson) (born 1965)
Jasper Carrott (born 1945)
Johnny Carson (1925–2005)
Nell Carter (1948–2003)
Nancy Cartwright (born 1957)
Dana Carvey (born 1955)
Neil Casey (born 1981)
Aya Cash (born 1982)
Cliff Cash (born 1981)
Craig Cash (born 1960)
Michael Cassidy (born 1983)
Dan Castellaneta (born 1957)
Mike Castle (born 1989)
Roy Castle (1932–1994)
Arturo Castro (born 1985)
Jade Catta-Preta (born 1984)
Mary Jo Catlett (born 1938)
Walter Catlett (1889–1960)
Kim Cattrall (born 1956)
John Catucci (born 1973)
Jo Caulfield (born 1965)
Tony Cavalero (born 1983)
Elise Cavanna (1902–1963)
Dick Cavett (born 1936)
Adam Cayton-Holland (born 1980)
Kyle Cease (born 1977)
Cedric the Entertainer (born 1964)
Kiray Celis (born 1995)
Wyatt Cenac (born 1976)
Michael Cera (born 1988)
Bülent Ceylan (born 1976)
Jessica Chaffin (born 1974)
Rachel Chagall (born 1952)
Sarah Chalke (born 1976)
Kevin Chamberlin (born 1963)
Emma Chambers (1964–2018)
Jackie Chan (born 1954)
Melanie Chandra (born 1984)
Jay Chandrasekhar (born 1968)
Carol Channing (1921–2019)
Jay Chanoine (born 1986/1987)
Zoë Chao (born 1985)
Omar Chaparro (born 1974)
Charlie Chaplin (1889–1977)
Graham Chapman (1941–1989)
Doug Chappel (born 1975)
Dave Chappelle (born 1973)
Charlamagne tha God (born 1978)
Craig Charles (born 1964)
Josh Charles (born 1971)
Charo
Melanie Chartoff (born 1948)
Charley Chase (1893–1940)
Chevy Chase (born 1943)
Michael Che (born 1983)
Karen Chee (born 1995)
Parvesh Cheena (born 1979)
Richard Cheese (born 1965)
Aaron Chen (born 1995)
Hank Chen (born 1989)
Kristin Chenoweth (born 1968)
Zach Cherry (born 1987)
Cherry Chevapravatdumrong (born 1977)
Ronny Chieng (born 1985)
Autumn Chiklis (born 1993)
Michael Chiklis (born 1963)
Feodor Chin (born 1974)
Chingo Bling (Pedro Herrera) (born 1979)
Lori Tan Chinn (born 1948)
Nasir Chinyoti (born 1970)
Ted Chippington (born 1960)
Whitney Chitwood
Henry Cho (born 1962)
John Cho (born 1972)
Margaret Cho (born 1968)
Jessica Chobot (born 1977)
Chokoleit (1970–2019)
Tommy Chong (born 1938)
Bill Chott (born 1969)
Stephen Chow (born 1962)
Paul Chowdhry (born 1974)
Bridget Christie (born 1971)
Richard Christy (born 1974)
Thomas Haden Church (born 1960)
Papa CJ (born 1977)
Anthony Clark (born 1964)
Bobby Clark (1888–1960)
Laurence Clark (born 1974)
Mystro Clark (born 1966)
Lenny Clarke (born 1953)
Julian Clary (born 1959)
Andrew "Dice" Clay (born 1958)
John Cleese (born 1939)
Ellen Cleghorne (born 1965)
Jemaine Clement (born 1974)
Sean Clements (born 1981)
Del Close (1934–1999)
Jerry Clower (1926–1998)
Martin Clunes (born 1961)
Andy Clyde (1892–1967)
Imogene Coca (1908–2001)
Michaela Coel (born 1987)
Andy Cohen (born 1968)
Catherine Cohen (born 1991)
Sacha Baron Cohen (born 1971)
Mindy Cohn (born 1966)
Diablo Cody (born 1978)
Sherry Cola (born 1989)
Enrico Colantoni (born 1963)
Stephen Colbert (born 1964)
Coldmirror (born 1984)
Deon Cole (born 1972)
Gary Coleman (1968–2010)
Jonathan Coleman (1956–2021)
Kelen Coleman (born 1984)
Ryan Coleman (born 1991)
Kim Coles (born 1962)
Bobby Collins (born 1951)
Michelle Collins (born 1981)
Misha Collins (born 1974)
Mo Collins (born 1965)
Katy Colloton (born 1984)
Olivia Colman (born 1974)
Sarah Colonna (born 1974)
Michael Colton (born 1975)
Robbie Coltrane (1950–2022)
Ray Combs (1956–1996)
Roisin Conaty (born 1979)
Pat Condell (born 1949)
Brian Conley (born 1961)
Kurtis Conner (born 1994)
Frank Conniff (born 1956)
Billy Connolly (born 1942)
Kevin Connolly (born 1974)
Adam Conover (born 1983)
Nina Conti (born 1974)
Paolo Contis (born 1984)
Tim Conway (1933–2019)
Steve Coogan (born 1965)
Carole Cook (1924–2023)
Dane Cook (born 1972)
Matt Cook (born 1984)
Peter Cook (1937–1995)
Josh Cooke (born 1979)
Danny Cooksey (born 1975)
Jennifer Coolidge (born 1961)
Bradley Cooper (born 1975)
Calico Cooper (born 1981)
Pat Cooper (born 1929)
Sarah Cooper (born 1977)
Tommy Cooper (1921–1984)
Alicia Coppola (born 1968)
Bill Corbett (born 1960)
Ronnie Corbett (1930–2016)
Nate Corddry (born 1977)
Rob Corddry (born 1971)
James Corden (born 1978)
Eugene Cordero (born 1978)
Professor Irwin Corey (1914–2017)
Joe Cornish (born 1968)
Judy Cornwell (born 1940)
Pete Correale (born 1970)
Rebecca Corry (born 1971)
Bud Cort (born 1948)
Paola Cortellesi (born 1973)
Bill Cosby (born 1937)
Lou Costello (1906–1959)
Sue Costello (born 1968)
Camille Cottin (born 1978)
Antony Cotton (born 1975)
Dave Coulier (born 1959)
Jonathan Coulton (born 1970)
Eliza Coupe (born 1981)
Stephanie Courtney (born 1970)
Allen Covert (born 1964)
Courteney Cox (born 1964)
Nikki Cox (born 1978)
Wally Cox (1924–1973)
Carly Craig (born 1980)
Billy Crawford (born 1982)
Lavell Crawford (born 1968)
Zach Cregger (born 1980)
Amanda Crew (born 1986)
Terry Crews (born 1968)
Chelsey Crisp (born 1983)
John Crist (born 1984)
Affion Crockett (born 1974)
Ben Crompton (born 1974)
Mackenzie Crook (born 1971)
Norm Crosby (1927–2020)
David Cross (born 1964)
Trae Crowder (born 1986)
Lucas Cruikshank (born 1993)
Hal Cruttenden (born 1969)
Barry Cryer (1935–2022)
Jon Cryer (born 1965)
Billy Crystal (born 1948)
Ice Cube (born 1969)
Seán Cullen (born 1965)
Whitney Cummings (born 1982)
Dan Cummins (born 1977)
James Cunningham (born 1973)
Mark Curry (born 1961)
Stephen Curry (born 1976)
Jane Curtin (born 1947)
Joan Cusack (born 1962)
John Cusack (born 1966)
Jack Cutmore-Scott (born 1987)
===D===
Peter F. Dailey (1868–1908)
E.G. Daily (born 1961)
Charlie Dale (1885–1971)
Jim Dale (born 1935)
Karl Dall (1941–2020)
John Francis Daley (born 1985)
Andrew Daly (born 1971)
Jon Daly (born 1977)
Tim Daly (born 1956)
Bill Dana (1924–2017)
Rodney Dangerfield (1921–2004)
Chad Daniels (born 1975)
Greg Daniels (born 1963)
Ted Danson (born 1947)
Dante (born 1970)
Tony Danza (born 1951)
Khalid Abbas Dar (born 1955)
Rhys Darby (born 1974)
Severn Darden (1929–1995)
Vir Das (born 1979)
Hayes Davenport (born 1986)
Jim David (born 1954)
Keith David (born 1956)
Larry David (born 1947)
Dov Davidoff (born 1973)
Hugh Davidson
Jim Davidson (born 1953)
Pete Davidson (born 1993)
Alan Davies (born 1966)
Greg Davies (born 1968)
Ann B. Davis (1926–2014)
Clifton Davis (born 1945)
DeRay Davis (born 1982)
Jeff B. Davis (born 1973)
Julia Davis (born 1966)
Kristin Davis (born 1965)
LaVan Davis (born 1966)
Lucy Davis (born 1973)
Matt Davis (born 1979)
Nore Davis (born 1984)
Tanyalee Davis (born 1970)
Tom Davis (born 1979)
Tom Davis (1952–2012)
Ken Davitian (born 1953)
Richard Dawson (1932–2012)
Les Dawson (1931–1993)
Shane Dawson (born 1988)
Charlie Day (born 1976)
Dennis Day (1916–1988)
Felicia Day (born 1979)
Mikey Day (born 1980)
Andy de la Tour (born 1954)
Ai-Ai delas Alas (born 1964)
Mark DeCarlo (born 1962)
Frank DeCaro (born 1962)
Enchong Dee (born 1988)
Gerry Dee (born 1968)
Jack Dee (born 1962)
Rob Deering (born 1972)
Rick Dees (born 1950)
Eddie Deezen (born 1957)
Ellen DeGeneres (born 1958)
Vance DeGeneres (born 1954)
Neil Delamere (born 1980)
Rob Delaney (born 1977)
Lea DeLaria (born 1958)
Jessica Delfino (born 1976)
Chris D'Elia (born 1980)
Joey de Leon (born 1946)
Grey DeLisle (born 1973)
Bianca Del Rio (born 1975)
David DeLuise (born 1971)
Dom DeLuise (1933–2009)
Ivor Dembina (born 1951)
Dr. Demento (born 1941)
Jamie Demetriou (born 1987)
Natasia Demetriou (born 1984)
Dustin Demri-Burns (born 1978)
Lori Beth Denberg (born 1976)
Jamie Denbo (born 1973)
Kat Dennings (born 1986)
Gabrielle Dennis (born 1981)
Hugh Dennis (born 1962)
Les Dennis (born 1953)
Bob Denver (1935–2005)
Joe DeRita (1909–1993)
Joe DeRosa (born 1977)
Portia de Rossi (born 1973)
Zooey Deschanel (born 1980)
Jack DeSena (born 1987)
Mike DeStefano (1966–2011)
Patti Deutsch (1943–2017)
Adam DeVine (born 1983)
Danny DeVito (born 1944)
Tommy Dewey (born 1978)
Joyce DeWitt (born 1949)
Eugenio Derbez (born 1962)
Dustin Diamond (1977–2021)
Chris Diamantopoulos (born 1975)
Joey Diaz (born 1963)
Ogie Diaz (born 1970)
Vic DiBitetto (born 1961)
Andy Dick (born 1965)
Daniel Dickey (born 1986)
John Di Domenico (born 1962)
Dominic Dierkes (born 1984)
Richard Digance (born 1949)
Debra DiGiovanni (born 1972)
Wendy van Dijk (born 1971)
Phyllis Diller (1917–2012)
Brooke Dillman (born 1966)
Kevin Dillon (born 1965)
Tim Dillon (born 1985)
John DiMaggio (born 1968)
Amelia Dimoldenberg (born 1994)
David Dineen-Porter (born 1979)
Paul Dinello (born 1962)
Juan Pablo Di Pace (born 1979)
Nick DiPaolo (born 1962)
Katie Dippold (born 1980)
Andrew Dismukes (born 1995)
Chris Distefano (born 1984)
Olli Dittrich (born 1956)
Gina DiVittorio (born 1995)
Omid Djalili (born 1965)
Anh Do (born 1977)
David Dobrik (born 1996)
Nik Dodani (born 1993)
Ken Dodd (1927–2018)
Mark Dolan (born 1974)
Dolphy (1928–2012)
Eugene Domingo (born 1971)
Joel Dommett (born 1985)
Kether Donohue (born 1985)
Lisa Donovan (born 1980)
Tate Donovan (born 1963)
Paul Dooley (born 1928)
Jimmy Dore (born 1965)
Jon Dore (born 1975)
Jeff Doucette (born 1947)
Doug E. Doug (born 1970)
Donna Douglas (1932–2015)
Jack Douglass (born 1988)
Beth Dover (born 1978)
John Dowie (born 1950)
Jim Downey (born 1952)
Paul W. Downs (born 1982)
Brian Doyle-Murray (born 1945)
Charlie Drake (1925–2006)
Larry Drake (1949–2016)
Ruth Draper (1884–1956)
Rachel Dratch (born 1966)
Tom Dreesen (born 1939)
Fran Drescher (born 1957)
Marie Dressler (1868–1934)
James Dreyfus (born 1968)
Anna Drezen
Drew Droege
Mike Drucker (born 1984)
Ryan Drummond (born 1973)
Eric Drysdale (born 1969)
Rebecca Drysdale (born 1978/1979)
Rick Ducommun (1952–2015)
Julia Duffy (born 1951)
Dennis Dugan (born 1946)
Christian Duguay (born 1970)
Josh Duhamel (born 1972)
Jean Dujardin (born 1972)
Clark Duke (born 1985)
Patty Duke (1946–2016)
Robin Duke (born 1954)
Sandy Duncan (born 1946)
Shane Dundas (born 1959)
Jeff Dunham (born 1962)
Lena Dunham (born 1986)
Barbara Dunkelman (born 1989)
Colton Dunn (born 1977)
Gabe Dunn (born 1988)
George Dunn (1914–1982)
Jimmy Dunn
Nora Dunn (born 1952)
Ryan Dunn (1977–2011)
Kyle Dunnigan (born 1971)
Debbe Dunning (born 1966)
Jay Duplass (born 1973)
Mark Duplass (born 1976)
Elvis Duran (born 1964)
Jimmy Durante (1893–1980)
Sanjay Dutt (born 1959)
Clea DuVall (born 1977)
Shelley Duvall (1949–2024)
Bil Dwyer (born 1962)
Jeff Dye (born 1983)
Harriet Dyer (born 1988)
Rob Dyrdek (born 1974)
Jeremy Dyson (born 1966)
===E===
Open Mike Eagle (born 1980)
Jason Earles (born 1977)
John Early (born 1988)
Christine Ebersole (born 1953)
Buddy Ebsen (1908–2003)
Chris Eckert (born 1986)
Lisa Eckhart (born 1992)
Costaki Economopoulos (born 1965)
Paul Eddington (1927–1995)
Ayo Edebiri (born 1995)
Alex Edelman (born 1989)
Eric Edelstein (born 1977)
Barbara Eden (born 1931)
Ade Edmondson (born 1957)
Dean Edwards (born 1970)
Derek Edwards (born 1958)
Ian Edwards
Justin Edwards (born 1972)
Christian Ehring (born 1972)
Billy Eichner (born 1978)
Hannah Einbinder (born 1995)
Bob Einstein (1942–2019)
Rich Eisen (born 1969)
Ophira Eisenberg (born 1972)
Naomi Ekperigin (born 1983)
Kevin Eldon (born 1959)
Jenna Elfman (born 1971)
Laurie Elliot (born 1971)
Abby Elliott (born 1987)
Bob Elliott (1923–2016)
Bridey Elliott (born 1990)
Chris Elliott (born 1960)
Mary Elizabeth Ellis (born 1979)
Gad Elmaleh (born 1971)
Ethan Embry (born 1978)
Dick Emery (1915–1983)
Harry Enfield (born 1961)
Georgia Engel (1948–2019)
Anke Engelke (born 1965)
Bill Engvall (born 1957)
John Ennis
Mike Epps (born 1970)
Molly Erdman (born 1974)
Heinz Erhardt (1909–1979)
Paco Erhard (born 1975)
Andy Erikson (born 1987)
Leon Errol (1881–1951)
Blaire Erskine (born 1991)
Maya Erskine (born 1987)
Cole Escola (born 1986)
Ennis Esmer (born 1978)
Felipe Esparza (born 1970)
Cameron Esposito (born 1981)
Charles Esten (born 1965)
Chris Estrada
Karla Estrada (born 1974)
Chris Evans (born 1966)
Lee Evans (born 1964)
Sean Evans (born 1986)
Bridget Everett (born 1972)
Kenny Everett (1944–1995)
Justine Ezarick (born 1984)
===F===
Ana Fabrega (born 1991)
Jackie Fabulous (born 1970)
Josh Fadem (born 1980)
Bill Fagerbakke (born 1957)
Damien Fahey (born 1980)
Donald Faison (born 1974)
Jimmy Fallon (born 1974)
Richard Fancy (born 1943)
Simon Fanshawe (born 1956)
Ali Farahnakian (born 1967)
Anna Faris (born 1976)
Chris Farley (1964–1997)
John Farley (born 1968)
Kevin Farley (born 1965)
Bill Farmer (born 1952)
Simon Farnaby (born 1973)
Jamie Farr (born 1934)
Bobby Farrelly (born 1958)
Peter Farrelly (born 1956)
Negin Farsad (born 1978)
Mitch Fatel (born 1968)
David Faustino (born 1974)
Jon Favreau (born 1966)
Nat Faxon (born 1975)
Isabel Fay (born 1979)
Joey Faye (1909–1997)
Helga Feddersen (1930–1990)
Wayne Federman (born 1959)
Paul Feig (born 1962)
Fortune Feimster (born 1980)
Rachel Feinstein
Ben Feldman (born 1980)
David Feldman
Liz Feldman (born 1977)
Marty Feldman (1934–1982)
Beanie Feldstein (born 1993)
Graham Fellowes (born 1959)
Randy Feltface (born 1980)
Spike Feresten (born 1964)
Craig Ferguson (born 1962)
Don Ferguson (born 1946)
Jay R. Ferguson (born 1974)
Jesse Tyler Ferguson (born 1975)
Keith Ferguson (born 1972)
Shelby Fero (born 1993)
Adam Ferrara (born 1966)
Jerry Ferrara (born 1979)
America Ferrera (born 1984)
Conchata Ferrell (1943–2020)
Will Ferrell (born 1967)
Herbert Feuerstein (1937–2020)
Tina Fey (born 1970)
Sally Field (born 1946)
Nathan Fielder (born 1983)
Michael Fielding (born 1982)
Noel Fielding (born 1973)
Totie Fields (1930–1978)
W. C. Fields (1880–1946)
Nathan Fillion (born 1971)
Larry Fine (1902–1975)
Chloe Fineman (born 1988)
Christian Finnegan (born 1973)
Katie Finneran (born 1971)
Dan Finnerty (born 1970)
Kathryn Fiore (born 1979)
Jo Firestone (born 1987)
Jordan Firstman (born 1991)
Mark Fischbach (aka) Markiplier (born 1989)
Jenna Fischer (born 1974)
Joely Fisher (born 1967)
Lang Fisher (born 1980)
Miles Fisher (born 1983)
Greg Fitzsimmons (born 1966)
Fannie Flagg (born 1944)
Joe Flaherty (1941–2024)
Crista Flanagan (born 1976)
Tom Flanigan
Kate Flannery (born 1964)
Charles Fleischer (born 1950)
Chris Fleming (born 1987)
Jim Florentine (born 1964)
Jake Flores
Neil Flynn (born 1960)
Jake Fogelnest (born 1979)
Dan Fogler (born 1976)
Lisa Foiles (born 1986)
Dave Foley (born 1963)
Mick Foley (born 1965)
Evan Fong (aka) Vanoss (born 1992)
Paul Foot (born 1973)
Faith Ford (born 1964)
Thomas Mikal Ford (1964–2016)
Matt Forde (born 1982)
Joey Forman (1929–1982)
George Formby (1904–1961)
George Formby Sr. (1875–1921)
Will Forte (born 1970)
Kat Foster (born 1978)
Jermaine Fowler (born 1988)
Jimmy Fowlie (born 1985)
Kirk Fox (born 1969)
Michael J. Fox (born 1961)
Zack Fox (born 1990)
Jeff Foxworthy (born 1958)
Jamie Foxx (born 1967)
Redd Foxx (1922–1991)
Leigh Francis (born 1974)
Stewart Francis (born 1964)
Jason Francisco (born 1987)
Pablo Francisco (born 1974)
Dave Franco (born 1985)
Eduardo Franco (born 1995)
James Franco (born 1978)
Al Franken (born 1951)
Bonnie Franklin (1944–2013)
Marina Franklin
Nelson Franklin (born 1985)
Daniel Franzese (born 1978)
Alice Fraser
William Frawley (1887–1966)
Stan Freberg (1926–2015)
Gavin Free (born 1988)
Travon Free (born 1985)
Cate Freedman
Martin Freeman (born 1971)
Jared Freid (born 1985)
Dawn French (born 1957)
Matt Frewer (born 1958)
Judah Friedlander (born 1969)
Will Friedle (born 1976)
Budd Friedman (1932–2022)
Jena Friedman (born 1983)
Matt Friend (born 1998)
Annette Frier (born 1974)
Leon Frierson (born 1986)
Don Friesen
Freddie Frinton (1909–1968)
Rebecca Front (born 1964)
David Frost (1939–2013)
Nick Frost (born 1972)
Stephen Fry (born 1957)
Pamela Fryman (born 1959)
Daisy Fuentes (born 1966)
John Fugelsang (born 1969)
Rich Fulcher (born 1968)
Kurt Fuller (born 1953)
Ned Fulmer (born 1987)
Ziwe Fumudoh (born 1992)
Ron Funches (born 1983)
Brittany Furlan (born 1986)
Fakkah Fuzz (born 1986)
===G===
Eva Gabor (1919–1995)
Jon Gabrus (born 1982)
Josh Gad (born 1981)
Richard Gadd (born 1989)
Hannah Gadsby (born 1978)
Jim Gaffigan (born 1966)
Mo Gaffney (born 1958)
Megan Gailey (born 1986)
Jayson Gainza (born 1980)
Daniele Gaither (born 1970)
Johnny Galecki (born 1975)
Zach Galifianakis (born 1969)
Gallagher (1946–2022)
Brian Gallivan
Sue Galloway
Mayce Galoni (born 1994)
Ed Gamble (born 1986)
Joross Gamboa (born 1984)
Megan Ganz (born 1984)
Robert Ben Garant (born 1970)
Jorge Garcia (born 1973)
Billy Gardell (born 1969)
Graeme Garden (born 1943)
Blanche Gardin (born 1977)
Brother Dave Gardner (1926–1983)
Heidi Gardner (born 1983)
Pete Gardner
Tony Gardner (born 1964)
Zarna Garg (born 1975)
Jeff Garlin (born 1962)
Ralph Garman (born 1964)
Paul Garner (1909–2004)
Janeane Garofalo (born 1964)
Teri Garr (1944–2024)
Betty Garrett (1919–2011)
Brad Garrett (born 1960)
Susie Garrett (1929–2002)
Kyle Gass (born 1960)
Ana Gasteyer (born 1967)
Alison Gates (born 1988/1989)
Kimmy Gatewood
Mark Gatiss (born 1966)
Joe Gatto (born 1976)
Ryan Gaul (born 1973)
Richard Gautier (1931–2017)
Joey Gay (born 1971)
George Gaynes (1917–2016)
Dustin Gee (1942–1986)
Chris Geere (born 1981)
Brett Gelman (born 1976)
John Gemberling (born 1981)
Genevieve (1920–2004)
Tom Gerhardt (born 1957)
Ricky Gervais (born 1961)
Chris Gethard (born 1980)
Estelle Getty (1923–2008)
Alice Ghostley (1923–2007)
Tom Gianas
Janno Gibbs (born 1969)
Marla Gibbs (born 1931)
Erin Gibson
Kathie Lee Gifford (born 1953)
Billy Gilbert (1894–1971)
Rhod Gilbert (born 1968)
Russell Gilbert (born 1959)
Sara Gilbert (born 1975)
Kevin Gillese (born 1980)
Terry Gilliam (born 1940)
Mo Gilligan (born 1988)
Shane Gillis (born 1987)
Paul Gilmartin (born 1963)
Ewen Gilmour (1963–2014)
Lisa Gilroy (born 1990)
Greg Giraldo (1965–2010)
Adele Givens (born 1960)
Jon Glaser (born 1968)
Nikki Glaser (born 1984)
Ira Glass (born 1959)
Todd Glass (born 1964)
Rick Glassman (born 1984)
Ilana Glazer (born 1987)
Jackie Gleason (1916–1987)
Tom Gleeson (born 1974)
Ben Gleib (born 1978)
Donald Glover (aka) Childish Gambino (born 1983)
Stephen Glover (aka) Steve-O (born 1974)
GloZell (born 1972)
George Gobel (1919–1991)
Godfrey (born 1969)
Janey Godley (born 1961)
Paul Goebel (born 1968)
Loyiso Gola (born 1983)
Judy Gold (born 1962)
Adam Goldberg (born 1970)
Adam F. Goldberg (born 1976)
Andrew Goldberg (born 1978)
Evan Goldberg (born 1982)
Whoopi Goldberg (born 1955)
Brett Goldstein (born 1980)
Jonathan Goldstein (born 1968)
Bobcat Goldthwait (born 1962)
Ian Gomez (born 1965)
Roberto Gómez Bolaños (Chespirito) (1929–2014)
Josh Gondelman (born 1985)
Jami Gong (born 1969)
Alex Gonzaga (born 1988)
Ginger Gonzaga (born 1983)
Toni Gonzaga (born 1984)
Cuba Gooding Jr. (born 1968)
Omar Gooding (born 1976)
John Goodman (born 1952)
Ken Goodwin (1933–2012)
Dan Goor (born 1975)
Leo Gorcey (1917–1969)
Joseph Gordon-Levitt (born 1981)
Christopher Gorham (born 1974)
Dave Gorman (born 1971)
Frank Gorshin (1933–2005)
Freeman Gosden (1899–1982)
Mark-Paul Gosselaar (born 1974)
Gilbert Gottfried (1955–2022)
Theodore Gottlieb (1906–2001)
Dana Gould (born 1964)
Sandra Gould (1916–1999)
Ray Goulding (1922–1990)
Sal Governale (born 1968)
Luba Goy (born 1945)
Jeff Grace
Topher Grace (born 1978)
Boothby Graffoe (born 1962)
Heather Graham (born 1970)
Matt Graham
Kelsey Grammer (born 1955)
Charlie Grandy (born 1974)
Fred Grandy (born 1948)
Corinne Grant (born 1973)
David Grant (born 1956)
Stephen Grant (born 1973)
Judy Graubart (born 1943)
Ari Graynor (born 1983)
Jeff Green (born 1964)
Seth Green (born 1974)
Tom Green (born 1971)
Bryan Greenberg (born 1978)
Shecky Greene (1926–2023)
Max Greenfield (born 1979)
Kathy Greenwood (born 1962)
Judy Greer (born 1975)
Melvin Gregg (born 1988)
Dick Gregory (1932–2017)
James Gregory (born 1946)
Tamsin Greig (born 1966)
Adrian Grenier (born 1976)
Stacey Grenrock-Woods (born 1975)
David Alan Grier (born 1955)
Erik Griffin (born 1972)
Eddie Griffin (born 1968)
Kathy Griffin (born 1960)
Andy Griffith (1926–2012)
Scott Grimes (born 1971)
Todd Grinnell (born 1976)
Asher Grodman (born 1987)
Charles Grodin (1935–2021)
Matt Groening (born 1954)
David Groh (1939–2008)
Kirsten Gronfield (born 1977)
Mary Gross (born 1953)
Michael Gross (born 1947)
Peter Grosz (born 1974)
Rene Gube (born 1979)
Matthew Gray Gubler (born 1980)
Christopher Guest (born 1948)
Patty Guggenheim (born 1984)
Ariana Guido (born 1999)
Ann Morgan Guilbert (1928–2016)
Robert Guillaume (1927–2017)
Harvey Guillen (born 1990)
Ingrid Guimarães (born 1972)
Gary Gulman (born 1970)
Appurv Gupta (born 1990)
Broti Gupta (born 1993)
Annabelle Gurwitch (born 1961)
Björn Gustafsson (born 1986)
Greg Gutfeld (born 1964)
Steve Guttenberg (born 1958)
Deryck Guyler (1914–1999)
===H===
Buddy Hackett (1924–2003)
Tiffany Haddish (born 1979)
Bill Hader (born 1978)
Sarah Hadland (born 1971)
Jenny Hagel
Hallie Haglund (born 1982)
Meredith Hagner (born 1987)
Kathryn Hahn (born 1973)
Tony Hale (born 1970)
Brian Haley (born 1961)
Jack Haley (1897–1979)
Stavros Halkias (born 1989)
Anthony Michael Hall (born 1968)
Brad Hall (born 1958)
Brandon Micheal Hall (born 1993)
Daheli Hall (born 1976)
Huntz Hall (1919–1999)
Rich Hall (born 1954)
Dieter Hallervorden (born 1935)
Katie Halper (born 1980)
Evelyn Hamann (1942–2007)
Neil Hamburger (born 1967)
Argus Hamilton
Lloyd Hamilton (1891–1935)
Ryan Hamilton (born 1976)
Jon Hamm (born 1971)
Darrell Hammond (born 1955)
Nick Hancock (born 1962)
Tony Hancock (1924–1968)
Jack Handey (born 1949)
Chelsea Handler (born 1975)
Colin Hanks (born 1977)
Tom Hanks (born 1956)
Gabbie Hanna (born 1991)
Alyson Hannigan (born 1974)
Ryan Hansen (born 1981)
Malcolm Hardee (1950–2005)
Brandon Hardesty (born 1987)
Mike Harding (born 1944)
Chris Hardwick (born 1971)
Johnny Hardwick (1958–2023)
Jeremy Hardy (1961–2019)
Oliver Hardy (1890–1957)
Allana Harkin
Otis Harlan (1865–1940)
Dan Harmon (born 1973)
Tim Harmston (born 1971/1972)
Valerie Harper (1939–2019)
William Jackson Harper (born 1980)
Neil Patrick Harris (born 1973)
Rachael Harris (born 1968)
Robin Harris (1953–1990)
Blake Harrison (born 1985)
Bret Harrison (born 1982)
Patti Harrison (born 1990)
Hannah Hart (born 1986)
Kevin Hart (born 1979)
Mamrie Hart (born 1983)
Melissa Joan Hart (born 1976)
Miranda Hart (born 1972)
Adam Hartle (born 1979)
Phil Hartman (1948–1998)
Steve Harvey (born 1957)
Ian Harvie
Murtaza Hassan (1965–2011)
Paul Walter Hauser (born 1986)
Allan Havey (born 1954)
Kali Hawk (born 1986)
Tim Hawkins (born 1968)
Tony Hawks (born 1960)
Goldie Hawn (born 1945)
Charles Hawtrey (1858–1923)
Charles Hawtrey (1914–1988)
Will Hay (1888–1949)
Richard Haydn (1905–1985)
Erinn Hayes (born 1976)
Sean Hayes (born 1970)
Mike Hayley
Natalie Haynes (born 1974)
Ted Healy (1896–1937)
Richard Hearne (1890–1987)
Caleb Hearon (born 1995)
Patricia Heaton (born 1958)
Ian Hecox (born 1987)
Mitch Hedberg (1968–2005)
Jon Heder (born 1977)
Briga Heelan (born 1987)
Bobby Heenan (1943–2017)
Kevin Heffernan (born 1968)
John Heffron (born 1970)
John Hegley (born 1953)
Robert Hegyes (1951–2012)
Tim Heidecker (born 1976)
Jesse Heiman (born 1978)
Hans-Joachim Heist (born 1949)
Simon Helberg (born 1980)
Grace Helbig (born 1985)
Emily Heller (born 1985)
Peter Helliar (born 1975)
Nick Helm (born 1980)
Katherine Helmond (1929–2019)
Ed Helms (born 1974)
Greg Hemphill (born 1969)
Shirley Hemphill (1947–1999)
Sherman Hemsley (1938–2012)
Dickie Henderson (1922–1985)
Christina Hendricks (born 1975)
Elaine Hendrix (born 1970)
Vic Henley (1962–2020)
Marilu Henner (born 1952)
Carolyn Hennesy (born 1962)
Buck Henry (1930–2020)
Ely Henry (born 1991)
Lenny Henry (born 1958)
Mike Henry (born 1964)
John Henton (born 1960)
Dai Henwood (born 1978)
Hugh Herbert (1884–1952)
Christoph Maria Herbst (born 1966)
Tim Herlihy (born 1966)
David Herman (born 1967)
Thomas Hermanns (born 1963)
Marcello Hernández (born 1997)
Mark Herras (born 1986)
Richard Herring (born 1967)
Edward Herrmann (1943–2014)
Seth Herzog (born 1970)
Howard Hesseman (1940–2022)
Bill Hicks (1961–1994)
Ryan Higa (born 1990)
David Anthony Higgins (born 1961)
John Michael Higgins (born 1963)
Maeve Higgins
Steve Higgins (born 1963)
Jhong Hilario (born 1976)
Dieter Hildebrandt (1927–2013)
Amy Hill (born 1953)
Bec Hill (born 1986)
Benny Hill (1924–1992)
Dave Hill (born 1974)
Dulé Hill (born 1975)
Ed Hill (born 1984)
Harry Hill (born 1964)
Jonah Hill (born 1983)
Martina Hill (born 1974)
Melinda Hill (born 1972)
Murray Hill
Thelma Hill (1906–1938)
Tymberlee Hill
Jeff Hiller
Adam Hills (born 1970)
Tony Hinchcliffe (born 1984)
Cheryl Hines (born 1965)
Gregory Hines (1946–2003)
Skip Hinnant (born 1940)
Michael Hitchcock (born 1958)
Thora Hird (1911–2003)
Justin Hires (born 1985)
Judd Hirsch (born 1935)
Matt Hobby (born 1985)
Stephanie Hodge (born 1956)
Jessy Hodges (born 1986)
John Hodgman (born 1971)
Joel Hodgson (born 1960)
Jackie Hoffman (born 1960)
Robby Hoffman (born 1989)
Gaby Hoffmann (born 1982)
Steve Hofstetter (born 1979)
Chris Hogan (born 1970)
Paul Hogan (born 1939)
Siobhan Fallon Hogan (born 1961)
Amy Hoggart (born 1986)
Corey Holcomb (born 1969)
Dominic Holland (born 1967)
Mary Holland (born 1985)
Judy Holliday (1921–1965)
Vanessa Hollingshead
Stanley Holloway (1890–1982)
Anders Holm (born 1981)
Chelsea Holmes (born 1993/1994)
Dave Holmes (born 1971)
Eamonn Holmes (born 1959)
Jessica Holmes (born 1973)
Pete Holmes (born 1979)
Todd Holoubek (born 1969)
Lauren Holt (born 1991)
Helen Hong (born 1985)
James Hong (born 1929)
Brian Hooks (born 1974)
Jan Hooks (1957–2014)
Bob Hope (1903–2003)
Sharon Horgan (born 1970)
Alex Horne (born 1978)
Kenneth Horne (1907–1969)
Mathew Horne (born 1978)
Alex Kapp Horner (born 1969)
David Hornsby (born 1975)
Don Hornsby (1924–1950)
Jane Horrocks (born 1964)
Lutz van der Horst (born 1975)
Edward Everett Horton (1886–1970)
Richard Steven Horvitz (born 1966)
Curly Howard (1903–1952)
Frankie Howerd (1917–1992)
Ken Howard (1944–2016)
Kyle Howard (born 1978)
Moe Howard (1897–1975)
Ron Howard (born 1954)
Russell Howard (born 1980)
Shemp Howard (1895–1955)
Kirby Howell-Baptiste (born 1987)
Glenn Howerton (born 1976)
Lil Rel Howery (born 1979)
Jeremy Hotz (born 1966)
Roy Hudd (1936–2020)
Oliver Hudson (born 1976)
Rob Huebel (born 1969)
Akilah Hughes (born 1989)
Dave Hughes (born 1970)
John Hughes (1950–2009)
London Hughes (born 1989)
Sean Hughes (1965–2017)
Steve Hughes (born 1966)
D. L. Hughley (born 1963)
Daniel Humbarger
Barry Humphries (1934–2023)
Bonnie Hunt (born 1961)
Brendan Hunt (born 1972)
Bill Hunter (1940–2011)
Reginald D. Hunter (born 1969)
David Huntsberger (born 1979)
Michelle Hurd (born 1966)
Carl Hurley (born 1941)
Elizabeth Hurley (born 1965)
Lillian Hurst (born 1943)
Jake Hurwitz (born 1985)
Jon Hurwitz (born 1977)
Brian Huskey (born 1968)
Toby Huss (born 1966)
Warren Hutcherson (born 1963)
Melanie Hutsell (born 1968)
Betty Hutton (1921–2007)
Sam Hyde (born 1985)
Jessica Hynes (born 1972)
===I===
Paul Iacono (born 1988)
Sal Iacono (born 1971)
Armando Iannucci (born 1963)
Adrienne Iapalucci
Eric Idle (born 1943)
Eddie Ifft (born 1974)
Gabriel Iglesias (born 1976)
Sabrina Impacciatore (born 1968)
Celia Imrie (born 1952)
Robin Ince (born 1969)
Neil Innes (1944–2019)
Scott Innes (born 1966)
Tino Insana (1948–2017)
Dom Irrera (born 1948)
Bill Irwin (born 1950)
Matt Iseman (born 1971)
Harith Iskander (born 1966)
Eddie Izzard (born 1962)
===J===
Brandon T. Jackson (born 1984)
Marc Evan Jackson (born 1970)
Shantira Jackson
Victoria Jackson (born 1959)
Manny Jacinto (born 1987)
Gillian Jacobs (born 1982)
Abbi Jacobson (born 1984)
Jon Jafari (aka) JonTron (born 1990)
Javed Jaffrey (born 1963)
T.J. Jagodowski (born 1971)
Gerburg Jahnke (born 1955)
Sabrina Jalees (born 1985)
Billy T. James (1948–1991)
Elis James (born 1980)
Janelle James (born 1979)
Kevin James (born 1965)
Nick Jameson (born 1948)
Jameela Jamil (born 1986)
Gary Janetti (born 1966)
Alia Janine (born 1978)
Michael Patrick Jann (born 1970)
Allison Janney (born 1959)
Zoe Jarman (born 1982)
David Jason (born 1940)
Jay Jason (1915–2001)
Sam Jay (born 1982)
Kavin Jayaram (born 1980)
Jim Jefferies (born 1977)
Richard Jeni (1957–2007)
Ken Jeong (born 1969)
Anthony Jeselnik (born 1978)
Jess Hilarious (born 1992)
Michael Jeter (1952–2003)
Geri Jewell (born 1956)
Penn Jillette (born 1955)
Andrea Jin (born 1996)
Maz Jobrani (born 1972)
Jake Johannsen (born 1960)
Anjelah Johnson (born 1982)
Anthony Johnson (1966–2021)
Chic Johnson (1891–1962)
Jake Johnson (born 1978)
James Austin Johnson (born 1989)
Josh Johnson (born 1990)
Lia Marie Johnson (born 1996)
Nicole Randall Johnson (born 1973)
Punkie Johnson (born 1985)
Rebekka Johnson
Slink Johnson
Zainab Johnson
Jay Johnston (born 1968)
Kristen Johnston (born 1967)
Brandon Scott Jones (born 1984)
"Hamburger" Jones
Jason Jones (born 1967)
Leslie Jones (born 1967)
Luka Jones (born 1975)
Matt Jones (born 1981)
Orlando Jones (born 1968)
Rashida Jones (born 1976)
Shirley Jones (born 1934)
Terry Jones (1942–2020)
Leslie Jordan (1955–2022)
Lesley Joseph (born 1945)
Colin Jost (born 1982)
Mitra Jouhari (born 1992)
Jesse Joyce (born 1978)
Mario Joyner (born 1961)
Mike Judge (born 1962)
Andy Juett (born 1977)
Phill Jupitus (born 1962)
Jay Jurden (born 1988)
===K===
Daniel Kaluuya (born 1989)
Madeline Kahn (1942–1999)
Bess Kalb (born 1987)
Jamie Kaler (born 1964)
Mindy Kaling (born 1979)
Adhir Kalyan (born 1983)
Carol Kane (born 1952)
Russell Kane (born 1975)
Gabe Kaplan (born 1945)
Myq Kaplan (born 1978)
Fabiana Karla (born 1975)
J. P. Karliak (born 1981)
Uğur Rıfat Karlova (born 1980)
Ian Karmel (born 1984)
Richard Karn (born 1956)
Aaron Karo (born 1979)
Jensen Karp (born 1979)
Moshe Kasher (born 1979)
Jackie Kashian (born 1963)
John Kassir (born 1957)
Rosanne Katon (born 1954)
Sierra Katow (born 1994)
Chris Kattan (born 1970)
Jonathan Katz (born 1946)
Mickey Katz (1909–1985)
Andy Kaufman (1949–1984)
Julie Kavner (born 1950)
Peter Kay (born 1973)
Phil Kay (born 1969)
Spencer Kayden (born 1971)
Danny Kaye (1911–1987)
Paul Kaye (born 1964)
Stubby Kaye (1918–1997)
Samson Kayo (born 1991/1992)
Zoe Kazan (born 1983)
Molly Kearney (born 1992)
Diane Keaton (born 1946)
Michael Keaton (born 1951)
Carolin Kebekus (born 1980)
Jared Keeso (born 1984)
Garrison Keillor (born 1942)
John Keister (born 1956)
Penelope Keith (born 1940)
Peter Kelamis (born 1967)
Echo Kellum (born 1982)
Chris Kelly (born 1983)
Frank Kelly (1938–2016)
Martha Kelly (born 1968)
Patsy Kelly (1910–1981)
Robert Kelly (born 1970)
Pert Kelton (1907–1968)
Brandis Kemp (1944–2020)
Ellie Kemper (born 1980)
Luke Kempner (born 1987)
Suzanna Kempner (born 1985)
Harriet Kemsley (born 1987)
Sarah Kendall (born 1976)
Edgar Kennedy (1890–1948)
Graham Kennedy (1934–2005)
Jamie Kennedy (born 1970)
Mimi Kennedy (born 1948)
Tom Kennedy (1885–1965)
Trey Kennedy
Kerri Kenney-Silver (born 1970)
Jon Kenny (born 1957)
Tom Kenny (born 1962)
Sean Kent
Humphrey Ker (born 1982)
Langston Kerman (born 1987)
Hape Kerkeling (born 1964)
Michael Kessler (born 1967)
Keegan-Michael Key (born 1971)
Kristin Key (born 1980)
Sarah Keyworth (born 1993)
Amanullah Khan (born 1970)
Guz Khan (born 1986)
Shappi Khorsandi (born 1973)
The Kid Mero (born 1983)
Ford Kiernan (born 1962)
Laura Kightlinger (born 1969)
Pat Kilbane (born 1969)
Craig Kilborn (born 1962)
Karen Kilgariff (born 1970)
Taran Killam (born 1982)
Ronnie Killings (aka) R-Truth (born 1972)
Laurie Kilmartin (born 1965)
Jimmy Kimmel (born 1967)
Jonathan Kimmel (born 1976)
Kyle Kinane (born 1976)
Richard Kind (born 1956)
Andy Kindler (born 1956)
Alan King (1927–2004)
Anthony King
Dave King (1929–2002)
Georgia King (born 1986)
Jaime King (born 1979)
Matt King (born 1968)
Michael Patrick King (born 1954)
Nika King
Sam Kinison (1953–1992)
Greg Kinnear (born 1963)
Roy Kinnear (1934–1988)
Kathy Kinney (born 1954)
Angela Kinsey (born 1971)
Bruno Kirby (1949–2006)
Bill Kirchenbauer (born 1953)
Jen Kirkman (born 1974)
Matt Kirshen (born 1980)
Jessica Kirson (born 1969)
Takeshi Kitano (born 1947)
Jonathan Kite (born 1979)
Daniel Kitson (born 1977)
Roger Kitter (1949–2015)
Felix Kjellberg (aka) PewDiePie (born 1989)
Julie Klausner (born 1978)
Chris Klein (born 1979)
Jessi Klein (born 1975)
Robert Klein (born 1942)
Jordan Klepper (born 1979)
Kevin Kline (born 1947)
Jack Klugman (1922–2012)
Jessica Knappett (born 1984)
Christopher Knight (born 1957)
Jak Knight (1993–2022)
Ted Knight (1923–1986)
Wayne Knight (born 1955)
Don Knotts (1924–2006)
Christy Knowings (born 1980)
Johnny Knoxville (born 1971)
Chris Knutson
Christine Ko (born 1988)
Cody Ko (born 1990)
Olga Koch (born 1992)
David Koechner (born 1962)
Stephanie Koenig (born 1987)
Matt Koff
Gaby Köster (born 1961)
Michael Koman (born 1977)
Hari Kondabolu (born 1982)
Dada Kondke (1932–1998)
Anna Konkle (born 1987)
Jenni Konner (born 1971)
Lynne Koplitz (born 1969)
Harvey Korman (1927–2008)
Annie Korzen (born 1938)
Liza Koshy (born 1996)
Michael Kosta (born 1979)
Ernie Kovacs (1919–1962)
Jo Koy (born 1971)
Lindsey Kraft (born 1980)
Jane Krakowski (born 1968)
Eric Allan Kramer (born 1962)
John Krasinski (born 1979)
Jan Kraus (born 1953)
Diether Krebs (1947–2000)
Bert Kreischer (born 1972)
Howard Kremer (born 1971)
Jonathan Krisel (born 1979)
Kurt Krömer (born 1974)
Nick Kroll (born 1978)
Maren Kroymann (born 1949)
Mike Krüger (born 1951)
David Krumholtz (born 1978)
Esther Ku (born 1980)
Lisa Kudrow (born 1963)
Akshay Kumar (born 1967)
Nish Kumar (born 1985)
Mila Kunis (born 1983)
Elvira Kurt (born 1961)
Swoosie Kurtz (born 1944)
Ashton Kutcher (born 1978)
Sarah Kuttner (born 1979)
Eugenia Kuzmina (born 1981)
===L===
Shia LaBeouf (born 1986)
Tyler Labine (born 1978)
Jake Lacy (born 1985)
Preston Lacy (born 1969)
Cathy Ladman
Jon Lajoie (born 1980)
Don Lake (born 1956)
Patricia Lake (1919–1993)
Maurice LaMarche (born 1958)
Leah Lamarr (born 1988)
Phil LaMarr (born 1967)
Kate Lambert (born 1981)
Lisa Lampanelli (born 1961)
Amy Landecker (born 1969)
David Lander (1947–2020)
Steve Landesberg (1936–2010)
Matteo Lane (born 1986)
Nathan Lane (born 1956)
Richard Lane (1899–1982)
Harry Langdon (1894–1944)
Artie Lange (born 1967)
Ted Lange (born 1948)
Chris Langham (born 1949)
Ruth Langsford (born 1960)
Beth Lapides
Lauren Lapkus (born 1985)
Rocky LaPorte
John Lapus (born 1973)
John Larroquette (born 1947)
Larry the Cable Guy (born 1963)
Jay Larson
Queen Latifah (born 1970)
Stan Laurel (1890–1965)
Dan Lauria (born 1947)
Hugh Laurie (born 1959)
Ed Lauter (1938–2013)
Lauren Laverne (born 1978)
Linda Lavin (1937–2024)
Tony Law (born 1969)
Bill Lawrence (born 1968)
Carolyn Lawrence (born 1967)
Doug Lawrence (Mr Lawrence) (born 1969)
Martin Lawrence (born 1965)
Mike Lawrence (born 1983)
Vicki Lawrence (born 1949)
Josh Lawson (born 1981)
Maggie Lawson (born 1980)
Preacher Lawson (born 1991)
Cloris Leachman (1926–2021)
Denis Leary (born 1957)
Matt LeBlanc (born 1967)
Annie Lederman (born 1983)
Andy Lee (born 1981)
Bobby Lee (born 1972)
C.S. Lee (born 1971)
Daniel Curtis Lee (born 1991)
Greg Lee (born 1962)
Hana Mae Lee (born 1988)
Jamie Lee (born 1983)
Jason Lee (born 1970)
Paul Sun-Hyung Lee (born 1972)
Raquel Lee (born 1986)
Rex Lee (born 1969)
Stewart Lee (born 1968)
Terence Lee (born 1964)
Andrew Leeds (born 1981)
Mekki Leeper (born 1994)
Jane Leeves (born 1961)
Michael Legge (born 1968)
Natasha Leggero (born 1974)
Jay Leggett (1963–2013)
John Leguizamo (born 1960)
John Lehr (born 1965)
Tom Lehrer (born 1928)
Carol Leifer (born 1956)
Ismo Leikola (born 1979)
Steve Lemme (born 1968)
Jack Lemmon (1925–2001)
Nancy Lenehan (born 1953)
Tom Lenk (born 1976)
Thomas Lennon (born 1970)
Jay Leno (born 1950)
Jack E. Leonard (1910–1973)
Chauncey Leopardi (born 1981)
Yassir Lester (born 1984)
James Lesure (born 1970)
David Letterman (born 1947)
Sam Levenson (1911–1980)
Johnny Lever (born 1950)
Zachary Levi (born 1980)
Kristine Levine (born 1970)
Samm Levine (born 1982)
Cash Levy
Dan Levy (born 1981)
Dan Levy (born 1983)
Eugene Levy (born 1946)
Clea Lewis (born 1965)
Jenifer Lewis (born 1957)
Jerry Lewis (1926–2017)
Kimrie Lewis (born 1982)
Phill Lewis (born 1968)
Richard Lewis (1947–2024)
Robert Q. Lewis (1921–1991)
Shari Lewis (1933–1998)
Vicki Lewis (born 1960)
Leslie Liao (born 1987)
Kobi Libii
Ali Liebegott (born 1971)
Paul Lieberstein (born 1967)
Wendy Liebman (born 1961)
Gabe Liedman (born 1982)
Judith Light (born 1949)
Lil Dicky (born 1988)
Lil' JJ (born 1990)
Matthew Lillard (born 1970)
Hal Linden (born 1931)
Riki Lindhome (born 1979)
George Lindsey (1928–2012)
Joe Lipari (born 1979)
Maureen Lipman (born 1946)
Joe List (born 1982)
Zoe Lister-Jones (born 1982)
Ian Lithgow (born 1972)
John Lithgow (born 1945)
Luciana Littizzetto (born 1964)
Ralf Little (born 1980)
Rich Little (born 1938)
Rob Little (born 1972)
Steve Little (born 1972)
Beth Littleford (born 1968)
Lucy Liu (born 1968)
Ron Livingston (born 1967)
Christopher Lloyd (born 1938)
Eric Lloyd (born 1986)
Harold Lloyd (1893–1971)
Roger Lloyd-Pack (1944–2014)
Joe Lo Truglio (born 1970)
Daniel Lobell (born 1982/1983)
Sean Lock (1963–2021)
Freddy Lockhart (born 1979)
Jamie Loftus (born 1993)
Greg London (born 1966)
Jay London (born 1966)
Josie Long (born 1982)
Justin Long (born 1978)
Shelley Long (born 1949)
Michael Longfellow (born 1994)
Mike Lookinland (born 1960)
Andrés López (born 1971)
George Lopez (born 1961)
Mario Lopez (born 1973)
Dave Losso
Julia Louis-Dreyfus (born 1961)
Faizon Love (born 1968)
Jason Love
Judi Love (born 1980)
Loni Love (born 1971)
Jon Lovett (born 1982)
Jon Lovitz (born 1957)
Rob Lowe (born 1964)
Chris Lowell (born 1984)
Britt Lower (born 1985)
Adam Lowitt
Mark Lowry (born 1958)
Matt Lucas (born 1974)
Luenell (born 1959)
Joanna Lumley (born 1946)
Eric Lutes (born 1962)
John Lutz (born 1973)
Joe Lycett (born 1988)
Desi Lydic (born 1981)
Carmen Lynch (born 1972)
Drew Lynch (born 1991)
Jane Lynch (born 1960)
Katherine Lynch (born 1972)
Stephen Lynch (born 1971)
Paul Lynde (1926–1982)
Nicholas Lyndhurst (born 1961)
Chelcie Lynn (born 1987)
Darci Lynne (born 2004)
Melanie Lynskey (born 1977)
Natasha Lyonne (born 1979)
===M===
Moms Mabley (1894–1975)
Sunny Mabrey (born 1975)
Bernie Mac (1957–2008)
Hayes MacArthur (born 1977)
Scott MacArthur (born 1979)
Norm Macdonald (1959–2021)
Rachael MacFarlane (born 1976)
Seth MacFarlane (born 1973)
Gavin MacLeod (1931–2021)
Fred MacMurray (1908–1991)
Justina Machado (born 1972)
April Macie (born 1975)
Laird Macintosh (born 1962)
Charles Mack (1888–1934)
Lee Mack (born 1968)
Mary Mack (born 1975)
Doon Mackichan (born 1962)
Mike MacRae (born 1977)
Sheila MacRae (1921–2014)
Chris Maddock (born 1977/1978)
Kathleen Madigan (born 1965)
Al Madrigal (born 1971)
Jolina Magdangal (born 1978)
Scooter Magruder (born 1988)
Sean Maguire (born 1976)
Naveed Mahbub
Bill Maher (born 1956)
Bruce Mahler (born 1950)
John Mahoney (1940–2018)
Bobby Mair (born 1986)
Shaun Majumder (born 1972)
Ally Maki (born 1986)
Wendie Malick (born 1950)
Joshua Malina (born 1966)
Keith Malley (born 1974)
Jose Manalo (born 1966)
Joe Mande (born 1983)
David Mandel (born 1970)
Howie Mandel (born 1955)
Dylan Mandlsohn (born 1980/1981)
Aasif Mandvi (born 1966)
Jason Manford (born 1981)
Stephen Mangan (born 1968)
Jonathan Mangum (born 1971)
Sunita Mani (born 1986)
Sebastian Maniscalco (born 1973)
Leslie Mann (born 1972)
Charlie Manna (1920–1970)
Bernard Manning (1930–2007)
Taryn Manning (born 1978)
J.P. Manoux (born 1969)
Jason Mantzoukas (born 1972)
Edu Manzano (born 1955)
Luis Manzano (born 1981)
Alec Mapa (born 1965)
Jenna Marbles (born 1986)
Joseph Marcell (born 1948)
Cheech Marin (born 1946)
Ken Marino (born 1968)
Pigmeat Markham (1904–1981)
Alfred Marks (1921–1996)
Bob Marley (born 1967)
Marc Maron (born 1963)
Ross Marquand (born 1981)
Empoy Marquez (born 1981)
Zoë Coombs Marr
Elizabeth Marrero (born 1963)
Dylan Marron (born 1988)
Betty Marsden (1919–1998)
James Marsden (born 1973)
Garry Marshall (1934–2016)
Paula Marshall (born 1964)
Penny Marshall (1943–2018)
Andrea Martin (born 1947)
Dean Martin (1917–1995)
Demetri Martin (born 1973)
Dick Martin (1922–2008)
Duane Martin (born 1965)
Mae Martin (born 1987)
Millicent Martin (born 1934)
Steve Martin (born 1945)
Adrian Martinez (born 1972)
Jackie Martling (born 1947)
Karen Maruyama (born 1958)
Chico Marx (1887–1961)
Groucho Marx (1890–1977)
Gummo Marx (1892–1977)
Harpo Marx (1888–1964)
Patricia Marx
Zeppo Marx (1901–1979)
Jackie Mason (1928–2021)
Christopher Massey (born 1990)
Kyle Massey (born 1991)
Christopher Masterson (born 1980)
Danny Masterson (born 1976)
Sean Masterson
Rose Matafeo (born 1992)
Ross Mathews (born 1979)
Shane Mauss (born 1980)
Andrew Maxwell (born 1974)
Elaine May (born 1932)
Ralphie May (1972–2017)
Rik Mayall (1958–2014)
Wendy Maybury (born 1974/1975)
Youngmi Mayer (born 1984)
Ayden Mayeri (born 1990)
Bill Maynard (1928–2018)
X Mayo (born 1987)
Jayma Mays (born 1979)
Dan Mazer (born 1971)
Jennie McAlpine (born 1984)
Alphonso McAuley (born 1984)
Jack McBrayer (born 1973)
Danny McBride (born 1976)
Jenny McCarthy (born 1972)
Matt McCarthy (born 1979)
Melissa McCarthy (born 1970)
Dave McCary (born 1985)
Rue McClanahan (1934–2010)
Fancy Ray McCloney
Edie McClurg (born 1945)
Matthew McConaughey (born 1969)
Brian McConnachie (1942–2024)
Eric McCormack (born 1963)
Dan McCoy (born 1978)
Michael McCullers (born 1971)
Bruce McCulloch (born 1961)
Julian McCullough (born 1979)
Paul McCullough (1883–1936)
Suli McCullough (born 1968)
Paul McDermott (born 1962)
Josh McDermitt (born 1978)
Heather McDonald (born 1970)
Kevin McDonald (born 1961)
Michael McDonald (born 1964)
Charlotte McDonnell (born 1990)
Charlie McDowell (born 1983)
Rob McElhenney (born 1977)
Griffin McElroy (born 1987)
Justin McElroy (born 1980)
Travis McElroy (born 1983)
Reba McEntire (born 1955)
Bonnie McFarlane (born 1973)
Caitlin McGee (born 1988)
John C. McGinley (born 1959)
Ted McGinley (born 1958)
Mike McGlone (born 1972)
Joel McHale (born 1971)
Jan McInnis
Michael McIntyre (born 1976)
Rose McIver (born 1988)
Adam McKay (born 1968)
Antoine McKay (born 1970)
Michael McKean (born 1947)
Jessica McKenna (born 1987)
Patrick McKenna (born 1960)
Bret McKenzie (born 1976)
Brian McKim
Mark McKinney (born 1959)
Kate McKinnon (born 1984)
Des McLean
Wendi McLendon-Covey (born 1969)
Seán McLoughlin (aka) jacksepticeye (born 1990)
Pauline McLynn (born 1962)
Heather McMahan (born 1987)
Ed McMahon (1923–2009)
Rove McManus (born 1974)
Don McMillan
Joanne McNally (born 1983)
Ryan McPartlin (born 1975)
Vaughn Meader (1936–2004)
Audrey Meadows (1922–1996)
Tim Meadows (born 1961)
Kevin Meaney (1956–2016)
Angela Means (born 1963)
Tatanka Means (born 1985)
Anne Meara (1929–2015)
Tallie Medel
Matt Meese (born 1983)
Keyla Monterroso Mejia (born 1998)
Fred Melamed (born 1956)
Stuttering John Melendez (born 1965)
Jill-Michele Melean (born 1979)
Doug Mellard
Carlos Mencia (born 1967)
Maine Mendoza (born 1995)
Rick Mercer (born 1969)
Stephen Merchant (born 1974)
Dave Merheje
Liz Meriwether (born 1981)
Buster Merryfield (1920–1999)
Paul Merton (born 1957)
Chris Messina (born 1974)
Debra Messing (born 1968)
Laurie Metcalf (born 1955)
Art Metrano (1936–2021)
Rebecca Metz (born 1973)
Kurt Metzger (born 1977)
Jason Mewes (born 1974)
Breckin Meyer (born 1974)
Josh Meyers (born 1976)
Seth Meyers (born 1973)
Florinda Meza (born 1948)
Shaun Micallef (born 1962)
Michael V. (born 1969)
Vic Michaelis (born 1993)
Felicia Michaels (born 1964)
Lorne Michaels (born 1944)
Kate Micucci (born 1980)
Thomas Middleditch (born 1982)
Bette Midler (born 1945)
A.D. Miles (born 1971)
John Milhiser (born 1981)
Cristin Milioti (born 1985)
Ben Miller (born 1966)
Christa Miller (born 1964)
Dennis Miller (born 1953)
George Miller (aka) Joji/Filthy Frank (born 1993)
Karlous Miller (born 1983)
Larry Miller (born 1953)
Marilyn Suzanne Miller (born 1950)
Max Miller (1894–1963)
Murray Miller (born 1976)
T.J. Miller (born 1981)
Sarah Millican (born 1975)
Spike Milligan (1918–2002)
Florence Mills (1896–1927)
Andy Milonakis (born 1976)
Tim Minchin (born 1975)
Brian Miner (born 1981)
Hasan Minhaj (born 1985)
Jerry Minor (born 1969)
Dan Mintz (born 1981)
Christopher Mintz-Plasse (born 1989)
Matt Mira (born 1983)
Lin-Manuel Miranda (born 1980)
Eugene Mirman (born 1975)
David Mitchell (born 1974)
Duke Mitchell (1926–1981)
Finesse Mitchell (born 1972)
Kel Mitchell (born 1978)
Mike Mitchell (born 1982)
Aditi Mittal
Michael Mittermeier (born 1966)
Jerod Mixon (born 1981)
Katy Mixon (born 1981)
Kenice Mobley (born 1985)
Colin Mochrie (born 1957)
Mehran Modiri (born 1967)
Alex Moffat (born 1982)
Kausar Mohammed (born 1992)
Nick Mohammed (born 1980)
Jay Mohr (born 1970)
Al Molinaro (1919–2015)
Richard Moll (1943–2023)
John Moloney
Dominic Monaghan (born 1976)
Mo'Nique (born 1967)
Bob Monkhouse (1928–2003)
Elizabeth Montgomery (1933–1995)
Lucy Montgomery (born 1975)
Adam Montoya (aka) SeaNanners (born 1984)
Lou Moon
Kyle Mooney (born 1984)
Nate Mooney
Paul Mooney (1941–2021)
Christina Moore (born 1973)
Dudley Moore (1935–2002)
Mary Tyler Moore (1936–2017)
Michael Moore (born 1954)
Phil Moore (born 1961)
Rudy Ray Moore (1927–2008)
Tim Moore (1887–1958)
Trevor Moore (1980–2021)
Victor Moore (1876–1962)
Agnes Moorehead (1900–1974)
Maribeth Monroe (born 1978)
Steve Monroe (born 1972)
Natalie Morales (born 1985)
Dylan Moran (born 1971)
George Moran (1881–1949)
Polly Moran (1883–1952)
Rick Moranis (born 1953)
Dave Mordal (born c. 1950–1960s)
Eric Morecambe (1926–1984)
German Moreno (1933–2016)
Harley Morenstein (born 1985)
Dermot Morgan (1952–1998)
Diane Morgan (born 1975)
Elliott Morgan (born 1987)
John Morgan (1930–2004)
Leanne Morgan (born 1965)
Matt Morgan (born 1977)
Tracy Morgan (born 1968)
Richie Moriarty (born 1980)
Brent Morin (born 1986)
Pat Morita (1932–2005)
Sam Morril (born 1986)
Brad Morris (born 1975)
Chris Morris (born 1965)
Garrett Morris (born 1937)
Lamorne Morris (born 1983)
Seth Morris (born 1970)
Neil Morrissey (born 1962)
Eleanor Morton
Howard Morton (1925–1997)
Lew Morton
Laci Mosley (born 1991)
Don Most (born 1953)
Zero Mostel (1915–1977)
José Sánchez Mota (born 1965)
Tahj Mowry (born 1986)
Matthew Moy (born 1984)
Bobby Moynihan (born 1977)
Teacher Mpamire (born 1983)
John Mulaney (born 1982)
Martin Mull (1943–2024)
Megan Mullally (born 1958)
Mitch Mullany (1968–2008)
Neil Mullarkey (born 1961)
Ina Müller (born 1965)
Brennan Lee Mulligan (born 1988)
Annie Mumolo (born 1973)
Noah Munck (born 1996)
Olivia Munn (born 1980)
Simon Munnery (born 1967)
Richard Murdoch (1907–1990)
Annie Murphy (born 1986)
Charlie Murphy (1959–2017)
Colin Murphy (born 1968)
Eddie Murphy (born 1961)
Kevin Murphy (born 1956)
Larry Murphy (born 1972)
Morgan Murphy (born 1981)
Noel Murphy (born 1961)
Al Murray (born 1968)
Bill Murray (born 1950)
James Murray (born 1976)
Jan Murray (1916–2006)
Joel Murray (born 1963)
Lorenzo Music (1937–2001)
Erik Myers
Mike Myers (born 1963)
Arden Myrin (born 1973)
===N===
Jim Nabors (1930–2017)
David Nagle (aka) Nogla (born 1992)
Suzy Nakamura (born 1968)
Kevin Nalty (born 1969)
Leonardo Nam (born 1979)
Philomaine Nanema (born 1982)
Aparna Nancherla (born 1982)
Kumail Nanjiani (born 1978)
Paul Nardizzi
Jason Narvy (born 1974)
Amber Nash (born 1977)
Jason Nash (born 1973)
Niecy Nash (born 1970)
Rex Navarette (born 1969)
Vhong Navarro (born 1977)
Henry Naylor (born 1966)
Kunal Nayyar (born 1981)
Cliff Nazarro (1904–1961)
Kevin Nealon (born 1953)
Lucas Neff (born 1985)
Taylor Negron (1957–2015)
Jamar Neighbors (born 1986)
Bob Nelson (born 1958)
Bridget Jones Nelson (born 1964)
Craig T. Nelson (born 1944)
Michael J. Nelson (born 1964)
Ozzie Nelson (1906–1975)
Thomas Nelstrop (born 1980)
Nick Nemeroff (1989–2022)
Nephew Tommy (born 1967)
Felipe Neto (born 1988)
Bebe Neuwirth (born 1958)
Kyle Newacheck (born 1984)
Bob Newhart (1929–2024)
Griffin Newman (born 1989)
Laraine Newman (born 1952)
Robert Newman (born 1964)
Tawny Newsome (born 1983)
Bert Newton (1938–2021)
Lee Newton (born 1985)
Desus Nice (born 1981)
Phil Nichol
Brittani Nichols (born 1988)
Mike Nichols (1931–2014)
Rhys Nicholson (born 1990)
Leslie Nielsen (1926–2010)
Trevor Noah (born 1984)
Ross Noble (born 1976)
Coleen Nolan (born 1965)
Katie Nolan (born 1987)
Henry Normal (born 1956)
Hayley Marie Norman (born 1989)
Mark Normand (born 1983)
Nolan North (born 1970)
Graham Norton (born 1963)
Jim Norton (born 1968)
Duncan Norvelle (born 1958)
Tig Notaro (born 1971)
B. J. Novak (born 1979)
Jacqueline Novak (born 1982)
Kayvan Novak (born 1978)
Don Novello (born 1943)
Dieter Nuhr (born 1960)
Luke Null (born 1990)
Whindersson Nunes (born 1995)
Oscar Nunez (born 1958)
Ego Nwodim (born 1988)
Bill Nye (born 1955)
Louis Nye (1913–2005)
===O===
Jay Oakerson (born 1977)
Matt Oberg (born 1976)
Dara Ó Briain (born 1972)
Conan O'Brien (born 1963)
Katie O'Brien (born 1983)
Mike O'Brien (born 1976)
Jerry O'Connell (born 1974)
Ryan O'Connell (born 1986)
Carroll O'Connor (1924–2001)
Des O'Connor (1932–2020)
Donald O'Connor (1925–2003)
Sean O'Connor (born 1985)
Bill Oddie (born 1941)
Bob Odenkirk (born 1962)
Claudia O'Doherty (born 1983)
David O'Doherty (born 1975)
Mark O'Donnell (1954–2012)
Rosie O'Donnell (born 1962)
Steve O'Donnell (born 1954)
Michael O'Donoghue (1940–1994)
Chris O'Dowd (born 1979)
Nick Offerman (born 1970)
Paul O'Grady (1955–2023)
Ardal O'Hanlon (born 1965)
Catherine O'Hara (born 1954)
Jim O'Heir (born 1962)
John O'Hurley (born 1954)
Atsuko Okatsuka (born 1988)
Tricia O'Kelley (born 1968)
Earl Okin (born 1947)
Amy Okuda (born 1989)
John Oliver (born 1977)
Alberto Olmedo (1933–1988)
Ole Olsen (1892–1963)
Kaitlin Olson (born 1975)
Conner O'Malley (born 1986)
Mike O'Malley (born 1966)
Timothy Omundson (born 1969)
Patrice O'Neal (1969–2011)
Ed O'Neill (born 1946)
Steve Oram (born 1973)
Yvonne Orji (born 1983)
Taylor Ortega (born 1989)
Zak Orth (born 1970)
Andrew Orvedahl (born 1976)
Barunka O'Shaughnessy
Andi Osho (born 1973)
Aida Osman (born 1996)
David Ossman (born 1936)
Dan Oster (born 1981)
Patton Oswalt (born 1969)
Cheri Oteri (born 1962)
Rick Overton (born 1954)
Bill Owen (1914–1999)
Gary Owen (born 1974)
Larry Owens
Zac Oyama (born 1987)
Gil Ozeri
===P===
Jack Paar (1918–2004)
Frankie Pace
Celia Pacquola (born 1983)
Anthony Padilla (born 1987)
Ashley Padilla (born 1993)
Robin Padilla (born 1969)
Monica Padman (born 1987)
Elliot Page (born 1987)
LaWanda Page (1920–2002)
Natalie Palamides (born 1990)
Brian Palermo
Ron Palillo (1949–2012)
Michael Palin (born 1943)
Adam Pally (born 1982)
Candy Palmater (1968–2021)
Sam Pancake (born 1964)
Maulik Pancholy (born 1974)
Angelica Panganiban (born 1986)
Franklin Pangborn (1889–1958)
John Pankow (born 1954)
Tom Papa (born 1968)
Yannis Pappas (born 1975)
John Paragon (1954–2021)
Zhubin Parang (born 1981)
Jimmy Pardo (born 1966)
Ron Pardo (born 1967)
Lennon Parham (born 1976)
Sandeep Parikh (born 1980)
Randall Park (born 1974)
Sydney Park (born 1997)
Nicole Parker (born 1978)
Pardis Parker
Paula Jai Parker (born 1969)
Sarah Jessica Parker (born 1965)
Trey Parker (born 1969)
Katherine Parkinson (born 1977/1978)
Chris Parnell (born 1967)
Grace Parra (born 1984)
Rachel Parris (born 1984)
Andy Parsons (born 1967)
Jim Parsons (born 1973)
Karyn Parsons (born 1966)
Jean-Claude Pascal (1927–1992)
Sara Pascoe (born 1981)
Joe Pasquale (born 1961)
David Pasquesi (born 1960)
Bastian Pastewka (born 1972)
Kasha Patel (born 1991)
Nimesh Patel (born 1986)
Punam Patel (born 1993)
Ravi Patel (born 1978)
Edi Patterson (born 1972)
Jake Paul (born 1997)
Pat Paulsen (1927–1997)
Rob Paulsen (born 1956)
David Paymer (born 1954)
Allen Payne (born 1968)
Khary Payton (born 1972)
Christina Pazsitzky (born 1976)
Ray Peacock (born 1973)
Trevor Peacock (1931–2021)
Jack Pearl (1894–1982)
Minnie Pearl (1912–1996)
Zack Pearlman (born 1988)
Josh Peck (born 1986)
Artemis Pebdani (born 1977)
Ron Pederson (born 1978)
Nasim Pedrad (born 1981)
Jordan Peele (born 1979)
Simon Pegg (born 1970)
Paula Pell (born 1963)
Jessimae Peluso (born 1982)
Johnny Pemberton (born 1981)
Steve Pemberton (born 1967)
Kal Penn (born 1977)
Joe Penner (1904–1941)
Eddie Pepitone (born 1958)
Jack Pepper (1902–1979)
Joe Pera (born 1988/1989)
Kevin Pereira (born 1982)
Chelsea Peretti (born 1978)
Danielle Perez
Ion Perez (born 1990)
Dewayne Perkins (born 1990)
Kathleen Rose Perkins (born 1974)
Sue Perkins (born 1969)
Rhea Perlman (born 1948)
Matthew Perry (1969–2023)
Tyler Perry (born 1969)
Jon Pertwee (1919–1996)
Tammy Pescatelli (born 1969)
Melissa Peterman (born 1971)
Bernadette Peters (born 1948)
Russell Peters (born 1970)
Paul Petersen (born 1945)
Cassandra Peterson (born 1951)
Alexandra Petri (born 1988)
Dat Phan (born 1975)
Jay Pharoah (born 1987)
J.J. Philbin (born 1974)
Regis Philbin (1931–2020)
Busy Philipps (born 1979)
Emo Philips (born 1956)
Henry Phillips (born 1969)
Sally Phillips (born 1970)
Philomaine Nanema, aka Philo (born 1982)
Dannah Phirman (born 1975)
Andrew Phung (born 1984)
Bobby Pickett (1938–2007)
Chonda Pierce (born 1960)
David Hyde Pierce (born 1959)
Amy Pietz (born 1969)
Karl Pilkington (born 1972)
Daniella Pineda (born 1987)
John Pinette (1964–2014)
Ryan Pinkston (born 1988)
Danielle Pinnock (born 1988)
Joe Piscopo (born 1951)
ZaSu Pitts (1894–1963)
Jeremy Piven (born 1965)
Nigel Planer (born 1953)
Ben Platt (born 1993)
Aubrey Plaza (born 1984)
Amy Poehler (born 1971)
Greg Poehler (born 1974)
Jon Pointing (born 1986)
Pokwang (born 1972)
Kevin Pollak (born 1957)
Mike Pollock (born 1965)
Jorge Porcel (1936–2006)
Javier Portales (1937–2003)
Chris Porter (born 1979)
Don Porter (1912–1997)
Lucy Porter (born 1973)
Tommy Pope (born 1979)
Brian Posehn (born 1966)
Parker Posey (born 1968)
Tom Poston (1921–2007)
Lauren Potter (born 1990)
Annie Potts (born 1952)
Paula Poundstone (born 1959)
Dan Povenmire (born 1963)
Esther Povitsky (born 1988)
Chris Powell (born 1983)
Dana Powell (born 1974)
Dante Powell (born 1987/1988)
Glen Powell (born 1988)
DeStorm Power (born 1982)
Navin Prabhakar
John Prats (born 1984)
Chris Pratt (born 1979)
Guy Pratt (born 1962)
Kyla Pratt (born 1986)
Laura Prepon (born 1980)
Jaime Pressly (born 1977)
Amber Preston
Eric Price (born 1974)
Tom Price (born 1980)
Freddie Prinze (1954–1977)
Freddie Prinze Jr. (born 1976)
Kiri Pritchard Mclean (born 1986)
Lauren Pritchard (born 1977)
Michael Pritchard (born 1950)
Philip Proctor (born 1940)
Markus Maria Profitlich (born 1960)
Greg Proops (born 1959)
Mark Proksch (born 1978)
Paul Provenza (born 1957)
Kelly Pryce (born 1986/1987)
DJ Pryor (born 1988)
Richard Pryor (1940–2005)
Cristina Pucelli (born 1969)
Danny Pudi (born 1979)
Rolo Puente (1939–2011)
Lucy Punch (born 1977)
Steve Punt (born 1962)
Missi Pyle (born 1972)
===Q===
DJ Qualls (born 1978)
Caroline Quentin (born 1960)
Adam Quesnell (born 1981/1982)
Steven Michael Quezada (born 1963)
Kate Quigley (born 1982)
Brian Quinn (born 1976)
Colin Quinn (born 1959)
Frankie Quiñones (born 1983)
Rufa Mae Quinto (born 1978)
Pauline Quirke (born 1959)
===R===
Stefan Raab (born 1966)
Allyn Rachel (born 1983)
Alan Rachins (1942–2024)
Gilda Radner (1946–1989)
Josh Radnor (born 1974)
Kat Radley (born 1985)
Charlotte Rae (1926–2018)
Issa Rae (born 1985)
Rags Ragland (1905–1946)
Jeff Ragsdale (1971–2023)
Randy Rainbow (born 1981)
Mary Lynn Rajskub (born 1971)
Sheryl Lee Ralph (born 1956)
Louis Ramey
Harold Ramis (1944–2014)
Rachel Ramras (born 1974)
Chris Ramsey (born 1986)
Franchesca Ramsey (born 1983)
Tony Randall (1920–2004)
Joe Randazzo (born 1978)
Frank Randle (1901–1957)
Romesh Ranganathan (born 1978)
Richard Rankin (born 1983)
Stephen Rannazzisi (born 1977)
Andrew Rannells (born 1978)
Esnyr Ranollo (born 2001)
Michael Rapaport (born 1970)
June Diane Raphael (born 1980)
Jim Rash (born 1971)
Allison Raskin (born 1989)
Meaghan Rath (born 1986)
Connor Ratliff
John Ratzenberger (born 1947)
Melissa Rauch (born 1980)
Raven-Symoné (born 1985)
Donnell Rawlings (born 1968)
Adam Ray (born 1982)
Jonah Ray (born 1981)
Ted Ray (1905–1977)
Martha Raye (1916–1994)
Al Read (1909–1987)
Howard Read (born 1984)
Diona Reasonover (born 1992)
Spoken Reasons (born 1988)
Andreas Rebers (born 1958)
Chris Redd (born 1985)
Jasper Redd (born 1979)
JR Reed (born 1967)
Jon Reep (born 1972)
Vic Reeves (born 1959)
Brian Regan (born 1958)
Jason Reich
Leo Reich (born 1998)
Sam Reich (born 1984)
Anne Reid (born 1935)
Noah Reid (born 1987)
Tara Reid (born 1975)
Tim Reid (born 1944)
Caitlin Reilly (born 1989)
Charles Nelson Reilly (1931–2007)
John C. Reilly (born 1965)
Carl Reiner (1922–2020)
Rob Reiner (born 1947)
Paul Reiser (born 1956)
Ivan Reitman (1946–2022)
Leah Remini (born 1970)
Roy Rene (1892–1954)
Adam Resnick
Retta (born 1970)
Paul Reubens (1952–2023)
Willie Revillame (born 1961)
Tony Revolori (born 1996)
Simon Rex (born 1974)
Gladys Reyes (born 1977)
Alex Reymundo
Manilyn Reynes (born 1972)
Burt Reynolds (1936–2018)
John Reynolds (born 1991)
Rick Reynolds (born 1951)
Ryan Reynolds (born 1976)
Caroline Rhea (born 1964)
Erica Rhodes (born 1983)
Tom Rhodes (born 1967)
Alfonso Ribeiro (born 1971)
Giovanni Ribisi (born 1974)
Alison Rich
Katie Rich
Simon Rich (born 1984)
Jeff Richards (born 1974)
Michael Richards (born 1949)
April Richardson (born 1979)
Jon Richardson (born 1982)
Matt Richardson (born 1991)
Miranda Richardson (born 1958)
Sam Richardson (born 1984)
Shane Richie (born 1964)
Mathias Richling (born 1953)
Jeff Richmond (born 1961)
Andy Richter (born 1966)
Laurence Rickard (born 1975)
Don Rickles (1926–2017)
Matt Rife (born 1995)
Daniel Rigby (born 1982)
Rob Riggle (born 1970)
Gina Riley (born 1961)
Jack Riley (1935–2016)
Lisa Riley (born 1976)
Kelly Ripa (born 1970)
Jason Ritter (born 1980)
John Ritter (1948–2003)
Tyler Ritter (born 1985)
Al Ritz (1901–1965)
Harry Ritz (1907–1986)
Jimmy Ritz (1904–1985)
Emilio Rivera (born 1961)
Joan Rivers (1933–2014)
Rowland Rivron (born 1958)
Steve Rizzo
Ted Robbins (born 1955)
Lyda Roberti (1906–1938)
Doris Roberts (1925–2016)
Ian Roberts (born 1965)
John Roberts (born 1971)
Jeanne Robertson (1943–2021)
Noah Robertson (born 1983)
Craig Robinson (born 1971)
Joe Robinson (born 1968)
Leonard Robinson
Phoebe Robinson (born 1984)
Tim Robinson (born 1981)
Linda Robson (born 1958)
Mo Rocca (born 1969)
Chris Rock (born 1965)
Tony Rock (born 1974)
Charles Rocket (1949–2005)
Glenn Rockowitz (born 1970)
Aida Rodriguez (born 1977)
Guillermo Rodriguez (born 1971)
Paul Rodriguez (born 1955)
Valente Rodriguez (born 1964)
Daniel Roebuck (born 1963)
Joe Rogan (born 1967)
Lauren Miller Rogen (born 1982)
Seth Rogen (born 1982)
Matt Rogers (born 1990)
Will Rogers (1879–1935)
Justin Roiland (born 1980)
Henry Rollins (born 1961)
Freddie Roman (1937–2022)
Rick Roman (1966–1992)
Larry Romano (born 1963)
Ray Romano (born 1957)
Michael Roof (1976–2009)
Mickey Rooney (1920–2014)
Rebecca Root (born 1969)
Stephen Root (born 1951)
George Roper (1934–2003)
Tony Rosato (1954–2017)
Patty Rosborough
Rose Marie (1923–2017)
Andrea Rosen (born 1974)
Michael Rosenbaum (born 1972)
Tom Rosenthal (born 1988)
Jeffrey Ross (born 1965)
Jonathan Ross (born 1960)
Lonny Ross (born 1978)
Tracee Ellis Ross (born 1972)
Steve Rossi (1932–2014)
Eli Roth (born 1972)
Barry Rothbart (born 1983)
Natasha Rothwell (born 1980)
Mitch Rouse (born 1964)
Patricia Routledge (born 1929)
Dan Rowan (1922–1987)
Patsy Rowlands (1931–2005)
Ben Roy (born 1979)
Alex Rubens
Michael Rubens
Alan Ruck (born 1956)
Paul Rudd (born 1969)
Rita Rudner (born 1953)
Jon Rudnitsky (born 1989)
Maya Rudolph (born 1972)
Amber Ruffin (born 1979)
Kevin Ruf (born 1961)
Sara Rue (born 1979)
Charlie Ruggles (1886–1970)
Debra Jo Rupp (born 1951)
Chris Rush (1946–2018)
Deborah Rush (born 1954)
Lenny Rush (born 2009)
Willie Rushton (1937–1996)
Anna Russell (1911–2006)
Mark Russell (1932–2023)
Nipsey Russell (1918–2005)
Rosalind Russell (1907–1976)
Paul Rust (born 1981)
Nick Rutherford (born 1985)
Irene Ryan (1902–1973)
Katherine Ryan (born 1983)
Roz Ryan (born 1951)
Ryan Bang (born 1991)
Stevie Ryan (1984–2017)
Tommy Ryman (born 1983)
===S===
Thomas Sadoski (born 1976)
Jerry Sadowitz (born 1961)
Bryan Safi
Katey Sagal (born 1954)
Bob Saget (1956–2022)
Tami Sagher
Mort Sahl (1927–2021)
Nichole Sakura (born 1989)
Rosa Salazar (born 1985)
Charles "Chic" Sale (1885–1936)
Soupy Sales (1926–2009)
Peter Sallis (1921–2017)
Tony Sam
Andy Samberg (born 1978)
Sugar Sammy (born 1976)
Angus Sampson (born 1978/1979)
Paul Sand (born 1932)
Beverly Sanders (born 1940)
Adam Sandler (born 1966)
Isabel Sanford (1917–2004)
Randy Santiago (born 1960)
Andrew Santino (born 1983)
Carlos Santos (born 1986)
Nico Santos (born 1979)
Horatio Sanz (born 1969)
Herb Sargent (1923–2005)
Martin Sargent (born 1975)
Will Sasso (born 1975)
Drake Sather (1959–2004)
Sabrina Sato (born 1981)
Rajiv Satyal (born 1976)
Jennifer Saunders (born 1958)
Andrea Savage (born 1973)
Ben Savage (born 1980)
Fred Savage (born 1976)
Julia Sawalha (born 1968)
Alexei Sayle (born 1952)
Prunella Scales (born 1932)
Brendan Scannell (born 1990)
Kristen Schaal (born 1978)
Sara Schaefer (born 1978)
Akiva Schaffer (born 1977)
Jackie Schaffer
Jeff Schaffer (born 1970)
Lewis Schaffer (born 1957)
Tom Scharpling (born 1969)
Mary Scheer (born 1963)
Paul Scheer (born 1976)
Ronnie Schell (born 1931)
Gus Schilling (1908–1957)
Robert Schimmel (1950–2010)
Hayden Schlossberg (born 1978)
Art Paul Schlosser (born 1960)
Wilfried Schmickler (born 1954)
Harald Schmidt (born 1957)
Jana Schmieding (born 1981)
Ralf Schmitz (born 1974)
Danielle Schneider (born 1975)
Helge Schneider (born 1955)
Martin Schneider (born 1964)
Rob Schneider (born 1963)
Sarah Schneider (born 1983)
Stephen Schneider (born 1980)
Barbara Schöneberger (born 1974)
Avery Schreiber (1935–2002)
Paul Schrier (born 1970)
Atze Schröder (born 1965)
Olaf Schubert (born 1967)
Richard Schull (1929–1999)
Andrew Schulz (born 1983)
Amy Schumer (born 1981)
Michael Schur (born 1975)
Leon Schuster (born 1951)
Samba Schutte (born 1983)
Ben Schwartz (born 1981)
Jason Schwartzman (born 1980)
Esther Schweins (born 1970)
David Schwimmer (born 1966)
Peter Scolari (1955–2021)
Brian Scolaro (born 1973)
Adam Scott (born 1973)
Reid Scott (born 1977)
Tom Everett Scott (born 1970)
Seann William Scott (born 1976)
Rory Scovel (born 1980)
Amanda Seales (born 1981)
Kenny Sebastian (born 1990)
Harry Secombe (1921–2001)
Amy Sedaris (born 1961)
Sam Seder (born 1966)
Rhea Seehorn (born 1972)
George Segal (1934–2021)
Jason Segel (born 1980)
Tom Segura (born 1979)
Streeter Seidell (born 1982)
Jerry Seinfeld (born 1954)
Scott Seiss (born 1994)
Jeffery Self (born 1987)
Peter Sellers (1925–1980)
Larry Semon (1889–1928)
Mack Sennett (1880–1960)
Rachel Sennott (born 1995)
Peter Serafinowicz (born 1972)
Josh Server (born 1979)
Joshua Seth (born 1970)
Glenn Shadix (1952–2010)
Ross Shafer (born 1954)
Paul Shaffer (born 1949)
Ari Shaffir (born 1974)
Ahir Shah (born 1990)
Tony Shalhoub (born 1953)
Garry Shandling (1949–2016)
Jake Shane (born 1999)
Paul Shane (1940–2013)
Rekha Shankar (born 1990)
Molly Shannon (born 1964)
Kapil Sharma (born 1981)
Josh Sharp (born 1987)
Timm Sharp (born 1978)
William Shatner (born 1931)
Alia Shawkat (born 1989)
Dick Shawn (1923–1987)
Wallace Shawn (born 1943)
Lin Shaye (born 1943)
Brendan Schaub (born 1983)
Harry Shearer (born 1943)
Reece Shearsmith (born 1969)
Charlie Sheen (born 1965)
Derek Sheen (born 1970/1971)
David Sheffield (born 1948)
Angela V. Shelton (born 1970)
Dax Shepard (born 1975)
Sherri Shepherd (born 1967)
Waen Shepherd (born 1971)
Eden Sher (born 1991)
Rondell Sheridan (born 1958)
Allan Sherman (1924–1973)
Sarah Sherman (born 1993)
Brad Sherwood (born 1964)
Tom Shillue (born 1966)
Ken Shimura (1950–2020)
Kevin Shinick (born 1969)
Iliza Shlesinger (born 1983)
Craig Shoemaker (born 1962)
Pauly Shore (born 1968)
Sammy Shore (1928–2019)
Martin Short (born 1950)
Pat Shortt (born 1967)
Michael Showalter (born 1970)
Wil Shriner (born 1953)
Jimmy Shubert
Rosie Shuster (born 1950)
Ritch Shydner (born 1952)
Ali Siddiq (born 1973/1974)
Emma Sidi (born 1991)
George Sidney (1876–1945)
Denny Siegel
Darien Sills-Evans (born 1974)
Laura Silverman (born 1966)
Sarah Silverman (born 1970)
Phil Silvers (1911–1985)
Arthur Simeon (born 1974)
John Simmit (born 1963)
Sam Simmons (born 1977)
Hannah Simone (born 1980)
Timothy Simons (born 1978)
Jimmi Simpson (born 1975)
Joan Sims (1930–2001)
Sinbad (born 1956)
Akaash Singh (born 1984)
Lilly Singh (born 1988)
Hella von Sinnen (born 1959)
Tiya Sircar (born 1982)
Dave Sirus
Red Skelton (1913–1997)
Benito Skinner (born 1993)
Frank Skinner (born 1957)
Chuck Sklar
Jenny Slate (born 1982)
Tony Slattery (1959–2025)
Jonathan Slavin (born 1969)
Bobby Slayton (born 1955)
Dulcé Sloan (born 1983)
Lindsay Sloane (born 1977)
Daniel Sloss (born 1990)
Veronika Slowikowska (born 1995)
Brendon Small (born 1975)
Lucien "Saluche" Small (1948–2007)
Andy Smart (1959–2023)
Jean Smart (born 1951)
Robert Smigel (born 1960)
Rickey Smiley (born 1968)
Yakov Smirnoff (born 1951)
Arthur Smith (born 1954)
Brandon Mychal Smith (born 1989)
Brian Thomas Smith (born 1977)
Daniel Browning Smith (born 1979)
DeAnne Smith (born 1979)
Joe Smith (1884–1981)
Kevin Smith (born 1970)
Kurtwood Smith (born 1943)
Linda Smith (1958–2006)
Margaret Smith
Phyllis Smith (born 1949)
Steve Smith (born 1945)
Will Smith (born 1968)
Will Smith (born 1971)
Yeardley Smith (born 1964)
JB Smoove (born 1965)
Cobie Smulders (born 1982)
Dana Snyder (born 1973)
Liza Snyder (born 1968)
David So (born 1987)
Barry Sobel (born 1959)
Betsy Sodaro (born 1984)
Dan Soder (born 1983)
John Solomon (born 1970)
Laura Solon (born 1979)
Lion Solser (1877–1915)
Kira Soltanovich (born 1973)
Suzanne Somers (1946–2023)
Rich Sommer (born 1978)
Sommore (born 1966)
Karan Soni (born 1989)
Gianmarco Soresi (born 1989)
Arleen Sorkin (1955–2023)
Ann Sothern (1909–2001)
Tito Sotto (born 1948)
Vic Sotto (born 1954)
Karla Souza (born 1985)
Kevin Spacey (born 1959)
David Spade (born 1964)
Hal Sparks (born 1969)
Ron Sparks (born 1977)
Aries Spears (born 1975)
Rachel Specter (born 1980)
Chris Spencer (born 1968)
Dave Spikey (born 1950)
Brent Spiner (born 1949)
Justin Spitzer
Thomas Spitzer (born 1988)
Emily Spivey (born 1971)
Brian Stack (born 1964)
Jessica St. Clair (born 1976)
Megan Stalter (born 1990)
John Stamos (born 1963)
Arnold Stang (1918–2009)
Doug Stanhope (born 1967)
Vivian Stanshall (1943–1995)
Martin Starr (born 1982)
Jen Statsky (born 1985)
Mark Steel (born 1960)
Steve Steen (born 1954)
Mary Steenburgen (born 1953)
Rob Stefaniuk (born 1971)
Axel Stein (born 1982)
Ben Stein (born 1944)
David Steinberg (born 1942)
Beth Stelling (born 1986)
Brian Stepanek (born 1971)
Jason Stephens
Pamela Stephenson (born 1949)
Skip Stephenson (1940–1992)
Ford Sterling (1883–1939)
Mindy Sterling (born 1953)
Howard Stern (born 1954)
Steve-O (born 1974)
Michael Fenton Stevens (born 1958)
Brody Stevens (1970–2019)
Ray Stevens (born 1939)
French Stewart (born 1964)
Jon Stewart (born 1962)
Paul Stewart (1908–1986)
David Ogden Stiers (1942–2018)
Ryan Stiles (born 1959)
Ben Stiller (born 1965)
Jerry Stiller (1927–2020)
Jeff Stilson (born 1959)
Hannah Stocking (born 1992)
Fred Stoller (born 1958)
Nicholas Stoller (born 1976)
Matt Stone (born 1971)
Eric Stonestreet (born 1971)
Larry Storch (1923–2022)
Gale Storm (1922–2009)
Moses Storm (born 1990)
Tom Stourton (born 1987)
Ryan Stout (born 1982)
Michael Strahan (born 1971)
Cordula Stratmann (born 1963)
Paul Strickland (born ?)
Cecily Strong (born 1984)
Rider Strong (born 1979)
Jessica Stroup (born 1986/1987)
Jud Strunk (1936–1981)
James Patrick Stuart (born 1968)
Geoff Stults (born 1977)
Jason Sudeikis (born 1975)
Chris Sugden (born 1952)
Alec Sulkin (born 1973)
Nancy Sullivan (born 1969)
Nicole Sullivan (born 1970)
Marc Summers (born 1951)
Jiaoying Summers (born 1990)
Slim Summerville (1892–1946)
Tika Sumpter (born 1980)
Josh Sundquist (born 1984)
Ethan Suplee (born 1976)
Kevin Sussman (born 1970)
Mena Suvari (born 1979)
Nick Swardson (born 1976)
John Swartzwelder (born 1949)
Barret Swatek (born 1977)
Jim Sweeney (born 1955)
Julia Sweeney (born 1959)
Steve Sweeney (born 1949)
Terry Sweeney (born 1950)
C. C. Swiney (born 1981)
JoAnna Garcia Swisher (born 1979)
Eric Sykes (1923–2012)
Wanda Sykes (born 1964)
Cynthia Szigeti (1949–2016)
Magda Szubanski (born 1961)
===T===
Jorma Taccone (born 1977)
George Takei (born 1937)
Rich Talarico (born 1973)
Jill Talley (born 1962)
Chris Tallman (born 1970)
Kerry Talmage (1963–2004)
Kapil Talwalkar (born 1993)
Danny Tamberelli (born 1982)
Jeffrey Tambor (born 1944)
Jimmy Tarbuck (born 1940)
Liza Tarbuck (born 1964)
Carl Tart (born 1989)
Drew Tarver (born 1986)
Emily Tarver (born 1982)
Masashi Tashiro (born 1956)
Catherine Tate (born 1969)
Jacques Tati (1907–1982)
Jimmy Tatro (born 1992)
Jim Tavaré (born 1963)
Christine Taylor (born 1971)
Clarice Taylor (1917–2011)
Ellie Taylor (born 1983)
Johnny Taylor Jr.
Maddie Taylor (born 1966)
Paul Taylor (born 1986)
Renée Taylor (born 1933)
Rip Taylor (1931–2019)
Tariq Teddy
Teller (born 1948)
Miles Teller (born 1987)
Judy Tenuta (1949–2022)
Steve Terreberry (born 1987)
Maria Thayer (born 1975)
Robin Thede (born 1979)
Justin Theroux (born 1971)
Alan Thicke (1947–2016)
Terry-Thomas (1911–1990)
Danny Thomas (1914–1991)
Dave Thomas (born 1949)
Eddie Kaye Thomas (born 1980)
Jay Thomas (1948–2017)
Joe Thomas (born 1983)
Josh Thomas (born 1987)
Kathryn Renée Thomas
Mark Thomas (born 1967)
Marlo Thomas (born 1937)
Michelle Thomas (1968–1998)
Vinny Thomas (born 1997)
Whitmer Thomas (born 1989)
Tim Thomerson (born 1946)
Greg Thomey (born 1961)
Bobb'e J. Thompson (born 1996)
Dave Thompson (born 1959)
Emma Thompson (born 1959)
Josh Robert Thompson (born 1975)
Kenan Thompson (born 1978)
Lea Thompson (born 1961)
Scott Thompson (born 1959)
Siobhan Thompson (born 1984)
Nick Thune (born 1979)
Baratunde Thurston (born 1977)
Sarah Thyre (born 1968)
Kai Tier
Tommy Tiernan (born 1969)
Greta Titelman (born 1990)
Christopher Titus (born 1964)
Mukesh Tiwari (born 1969)
Stephen Tobolowsky (born 1951)
Thelma Todd (1905–1935)
Sandi Toksvig (born 1958)
Steph Tolev (born 1985)
Judy Toll (1958–2002)
Allison Tolman (born 1981)
Jes Tom (born 1990)
Lily Tomlin (born 1939)
David Tomlinson (1917–2000)
Taylor Tomlinson (born 1993)
Paul F. Tompkins (born 1968)
TomSka (born 1990)
Paul Tonkinson (born 1969)
Barry Took (1928–2002)
Shayne Topp (born 1991)
Rip Torn (1931–2019)
Nate Torrence (born 1977)
Julio Torres (born 1987)
Liz Torres (born 1947)
Guy Torry (born 1969)
Joe Torry (born 1965)
Daniel Tosh (born 1975)
Josie Totah (born 2001)
Robert Townsend (born 1957)
Jerry Trainor (born 1977)
Natalie Tran (born 1986)
Robin Tran (born 1986)
Rosie Tran (born 1984)
Tien Tran (born 1987)
Nancy Travis (born 1961)
Jesus Trejo (born 1986)
Harry Trevaldwyn (born 1994)
Angela Trimbur (born 1981)
Tommy Trinder (1909–1989)
Chloe Troast (born 1997)
Verne Troyer (1969–2018)
Duncan Trussell (born 1974)
Nora Tschirner (born 1981)
Irene Tu (born 1992)
Bryan Tucker
Chris Tucker (born 1971)
Alan Tudyk (born 1971)
Jane Turner (born 1960)
Toby Turner (born 1985)
Ben Turpin (1869–1940)
Aisha Tyler (born 1970)
===U===
Alanna Ubach (born 1975)
Bob Uecker (born 1935)
Ikechukwu Ufomadu (born 1986)
Tracey Ullman (born 1959)
Sheryl Underwood (born 1963)
Brian Unger (born 1965)
Gabrielle Union (born 1972)
Stanley Unwin (1911–2002)
James Urbaniak (born 1963)
Michael Urie (born 1980)
===V===
John Valby, aka Dr. Dirty (born 1944)
Wilmer Valderrama (born 1980)
Ramón Valdés (1923–1988)
Gary Valentine (born 1961)
Billy Van (1934–2003)
Dick Van Dyke (born 1925)
Jerry Van Dyke (1931–2018)
Dick Van Patten (1928–2015)
Danitra Vance (1954–1994)
Nia Vardalos (born 1962)
Tuesday Vargas (born 1980)
Janet Varney (born 1976)
Jim Varney (1949–2000)
Johnny Vaughan (born 1966)
Baron Vaughn (born 1980)
Vince Vaughn (born 1970)
Milana Vayntrub (born 1987)
Radhika Vaz (born 1973)
Jennifer Veal (born 1991)
Sindhu Vee (born 1969)
Johnny Vegas (born 1970)
Ricky Velez (born 1989)
Reginald VelJohnson (born 1952)
Vinny Vella (1947–2019)
Prashanth Venkataramanujam (born 1987)
Milo Ventimiglia (born 1977)
Sofia Vergara (born 1972)
Tom Verica (born 1964)
Andrée Vermeulen (born 1982)
Jackie Vernon (1924–1987)
Wally Vernon (1904–1970)
Vice Ganda (born 1976)
Eva Victor
John Viener (born 1972)
Gillian Vigman (born 1972)
Kulap Vilaysack (born 1980)
Nova Villa (born 1946)
Carlos Villagrán (born 1942)
Buboy Villar (born 1998)
Melissa Villaseñor (born 1987)
Hervé Villechaize (1943–1993)
Tim Vine (born 1967)
Geraldine Viswanathan (born 1995)
Jon Vitti (born 1960)
Édgar Vivar (born 1944)
Paul C. Vogt (born 1964)
Theo Von (born 1980)
Daniel von Bargen (1950–2015)
Rich Vos (born 1957)
Sal Vulcano (born 1976)
===W===
Otto Waalkes (born 1948)
Nina Wadia (born 1968)
Mark Wahlberg (born 1971)
David Wain (born 1969)
Lena Waithe (born 1984)
Taika Waititi (born 1975)
Emil Wakim (born 1998)
Eliot Wald (1946–2003)
Gary Waldhorn (1943–2022)
Christopher Walken (born 1943)
Benjamin Walker (born 1982)
Devon Walker (born 1991)
Doug Walker (born 1981)
Holly Walker (born 1967)
Jimmie Walker (born 1947)
Nancy Walker (1922–1992)
Roy Walker (born 1940)
Max Wall (1908–1990)
Danny Wallace (born 1976)
George Wallace (1895–1960)
George Wallace Jnr (1918–1968)
George Wallace (born 1952)
Trevor Wallace (born 1992)
Linda Wallem (born 1961)
Phoebe Waller-Bridge (born 1985)
David Walliams (born 1971)
Ruth Wallis (1920–2007)
Greg Walloch (born 1970)
Bradley Walsh (born 1960)
Brendon Walsh (born 1978)
Holly Walsh (born 1980)
Kate Walsh (born 1967)
Mary Walsh (born 1952)
Matt Walsh (born 1964)
Ray Walston (1914–2001)
Jessica Walter (1941–2021)
Lisa Ann Walter (born 1963)
Julie Walters (born 1950)
David Walton (born 1978)
Christoph Waltz (born 1956)
Phil Wang (born 1990)
Sheng Wang (born 1980)
Keith Wann (born 1969)
Patrick Warburton (born 1964)
Asha Ward (born 1999)
Mike Ward (born 1973)
Brandon Wardell (born 1992)
Eric Wareheim (born 1976)
Marsha Warfield (born 1954)
Malcolm-Jamal Warner (born 1970)
Mike Warnke (born 1946)
Rusty Warren (1930–2021)
Sydnee Washington
Derek Waters (born 1979)
Michaela Watkins (born 1971)
Reggie Watts (born 1972)
Ruby Wax (born 1953)
Damon Wayans (born 1960)
Damon Wayans Jr. (born 1982)
Keenen Ivory Wayans (born 1958)
Kim Wayans (born 1961)
Marlon Wayans (born 1972)
Shawn Wayans (born 1971)
Kountry Wayne (born 1987)
Robert Webb (born 1972)
Steven Weber (born 1961)
Fred Wedlock (1942–2010)
Lauren Weedman (born 1969)
Ed Weeks (born 1980)
Henning Wehn (born 1974)
Brent Weinbach
Stephnie Weir (born 1967)
Shaun Weiss (born 1979)
Oliver Welke (born 1966)
Danny Wells (1941–2013)
Noël Wells (born 1986)
George Wendt (born 1948)
Ali Wentworth (born 1965)
Tatá Werneck (born 1983)
Amber Stevens West (born 1986)
Billy West (born 1952)
Lindy West (born 1982)
Alice Wetterlund (born 1981)
Frank Whaley (born 1963)
Wil Wheaton (born 1972)
Brooks Wheelan (born 1986)
Bert Wheeler (1895–1968)
Jill Whelan (born 1966)
Betty White (1922–2021)
Ellie White (born 1989)
Jaleel White (born 1976)
Mike White (born 1970)
Ron White (born 1956)
Slappy White (1921–1995)
June Whitfield (1925–2018)
Jack Whitehall (born 1988)
Jason John Whitehead
Paul Whitehouse (born 1958)
Bradley Whitford (born 1959)
Kym Whitley (born 1961)
Mae Whitman (born 1988)
Jane Wickline (born 1999)
Josh Widdicombe (born 1983)
Nick Wiger (born 1980)
Tracey Wigfield (born 1983)
Kristen Wiig (born 1973)
Brian Wilde (1927–2008)
Stefanie Wilder-Taylor
Fred Willard (1933–2020)
Ben Willbond (born 1973)
Allison Williams (born 1988)
Anson Williams (born 1949)
Ashley Williams (born 1978)
Barney Williams (1824–1876)
Barry Williams (born 1954)
Bert Williams (1874–1922)
Brad Williams (born 1984)
Charlie Williams (1927–2006)
Chris Williams (born 1967)
Cindy Williams (1947–2023)
Gary Anthony Williams (born 1966)
Harland Williams (born 1962)
Jessica Williams (born 1986)
Katt Williams (born 1973)
Kenneth Williams (1926–1988)
Kimberly Williams-Paisley (born 1971)
Mason Williams (born 1938)
Robin Williams (1951–2014)
Tyler James Williams (born 1992)
Victor Williams (born 1970)
Wendy Williams (born 1964)
Dave Williamson
Taylor Williamson
Cardis Cardell Willis (1937–2007)
Dave Willis (born 1970)
Dave Willis (1895–1973)
Denny Willis (1920–1995)
Justin Willman (born 1980)
Emma Willmann (born 1985)
Holly Willoughby (born 1981)
Larry Wilmore (born 1961)
Cal Wilson (1970–2023)
Casey Wilson (born 1980)
Debra Wilson (born 1962)
Demond Wilson (born 1946)
Flip Wilson (1933–1998)
Lou Wilson (born 1991)
Luke Wilson (born 1971)
Mary Louise Wilson (born 1931)
Owen Wilson (born 1968)
Rainn Wilson (born 1966)
Rebel Wilson (born 1980)
Reno Wilson (born 1969)
Thomas F. Wilson (born 1959)
Bob Wiltfong (born 1969)
April Winchell (born 1960)
Henry Winkler (born 1945)
Lizz Winstead (born 1961)
Jonathan Winters (1925–2013)
Norman Wisdom (1915–2010)
Chris Witaske (born 1983)
Brenda Withers
Harris Wittels (1984–2015)
Fred Wolf (born 1964)
Michelle Wolf (born 1985)
Dennis Wolfberg (1946–1994)
Jason Woliner (born 1980)
Ali Wong (born 1982)
Jimmy Wong (born 1987)
Kristina Wong (born 1978)
Roy Wood Jr. (born 1978)
Victoria Wood (1953–2016)
Danny Woodburn (born 1964)
Kim Woodburn (born 1942)
Zach Woods (born 1984)
Glenn Wool (born 1974)
Sheb Wooley (1921–2003)
Robert Woolsey (1888–1938)
Harry Worth (1917–1989)
Mike Wozniak (born 1979)
Edgar Wright (born 1974)
Steven Wright (born 1955)
Sabrina Wu (born 1998)
Robert Wuhl (born 1951)
Chris Wylde (born 1976)
Ed Wynn (1886–1966)
Jacob Wysocki (born 1990)
===X===
Swami X (1925–2015)
===Y===
Rajpal Yadav (born 1971)
Marc Yaffee (born 1961)
Kaya Yanar (born 1973)
Alan Yang (born 1983)
Bowen Yang (born 1990)
Eugene Lee Yang (born 1986)
Jenny Yang (born 1990)
Jimmy O. Yang (born 1987)
"Weird Al" Yankovic (born 1959)
Cedric Yarbrough (born 1973)
Mike Yard
Mike Yarwood (1941–2023)
Gina Yashere (born 1974)
Lucky Yates (born 1967)
Dustin Ybarra (born 1989)
Steven Yeun (born 1983)
Charlyne Yi (born 1986)
Cem Yılmaz (born 1973)
Celeste Yim (born 1996)
Michael Yo (born 1974)
Aaron Yonda (born 1973)
Dwight York
Heléne Yorke (born 1985)
Alan Young (1919–2016)
Bill Young (died 2014)
Parker Young (born 1988)
Rick Younger (born 1969)
Henny Youngman (1906–1998)
Jaboukie Young-White (born 1994)
Hampton Yount (born 1984)
Bassem Youssef (born 1974)
Ramy Youssef (born 1991)
Joe Yule (1892–1950)
Imran Yusuf (born 1979)
===Z===
Tincho Zabala (1923–2001)
Hollywood Zakoshisyoh (born 1974)
Andy Zaltzman (born 1974)
Sasheer Zamata (born 1986)
Katya Zamolodchikova
Alex Zane (born 1979)
Bob Zany (born 1961)
Steve Zahn (born 1967)
Steve Zaragoza (born 1982)
Vitaly Zdorovetskiy (born 1992)
Volodymyr Zelenskyy (born 1978)
Henry Zebrowski (born 1984)
David Zed
Mather Zickel (born 1970)
Dolph Ziggler (born 1980)
Jenny Zigrino (born 1987)
Steve Zissis (born 1975)
Tay Zonday (born 1982)
Alan Zweibel (born 1950)
==Comedy groups==
Ant & Dec
Armstrong and Miller
Abbott and Costello
Barats and Bereta
Beyond the Fringe
Bob and Ray
Bonzo Dog Doo-Dah Band
BriTANicK
Broken Lizard
Brown and Carney
Burns and Allen
CollegeHumor
The Chaser
Les Charlots
Cheech and Chong
Clark and McCullough
The Comedy Store Players
The Comic Strip
Dalton Trumbo's Reluctant Cabaret
The Firesign Theatre
Flight of the Conchords
Frangela
The Frat Pack
French and Saunders
Fry and Laurie
Garfunkel and Oates
God's Pottery
The Goons
The Grumbleweeds
Hale and Pace
Hamish and Andy
Hard 'n Phirm
Homer and Jethro
Jackass
Key and Peele
The Kids in the Hall
The Kipper Kids
Kreisiraadio from Estonia
Lano and Woodley
Laurel and Hardy
The League of Gentlemen
Little Britain
The Little Rascals
The Lonely Island
Les Luthiers
The Lucas Brothers
Marijuana Logues
Martin and Lewis
Marx Brothers
McKenzie Brothers
The Mighty Boosh
Million Dollar Extreme
The Minnesota Wrecking Crew
Mitchell and Webb
Monty Python
Morecambe and Wise
Not Ready for Prime-Time Players (Saturday Night Live)
Paul and Storm
Penn & Teller
Pete and Dud
Phil Lord and Christopher Miller
Please Don't Destroy
Punt and Dennis
Reeves and Mortimer
The Ritz Brothers
Rowan and Martin
Royal Canadian Air Farce
Scotland the What?
Sklar Brothers
Smith and Dale
Smosh
Smothers Brothers
Stella
Stiller and Meara
Studio C
Tenacious D
The Tenderloins
The Three Stooges
Tim and Eric
The Try Guys
The Umbilical Brothers
Upright Citizens Brigade
Vanoss Crew/Banana Bus Squad
The Valleyfolk
Vinesauce
Wayne and Shuster
Wheeler and Woolsey
The Whitest Kids U' Know
==Comedy writers==
(sorted alphabetically by surname)
Douglas Adams (1952–2011)
Fred Allen (1894–1956)
Woody Allen (born 1935)
Tony Barbieri (born 1963)
Chesney and Wolfe
Roy Clarke (born 1930)
Dick Clement (born 1937)
David Croft (1922–2011)
Barry Cryer
Esmonde and Larbey
Galton and Simpson
W. S. Gilbert
Willis Hall
Antony Jay
Carla Lane
Ian La Frenais (born 1937)
Graham Linehan and Arthur Mathews
Jeremy Lloyd
David Nobbs
Simon Nye
Frank Muir
Denis Norden
S. J. Perelman
Jimmy Perry
David Renwick
Jack Rosenthal
David Sedaris
Gerardo Sofovich (1937–2015)
Hugo Sofovich (1939–2003)
Johnny Speight
John Sullivan
James Thurber
Peter Tinniswood
Zoë Tomalin
Keith Waterhouse
|
[
"Michael Yo",
"Al Madrigal",
"Mo Amer",
"Chris Langham",
"Jimmy Perry",
"Billy Crystal",
"BriTANicK",
"Kevin Shinick",
"Peter Kay",
"Jill-Michele Melean",
"Zoe Kazan",
"Greg Walloch",
"Jack Dee",
"Nika King",
"Suzy Nakamura",
"Kal Penn",
"Jen Statsky",
"Phyllis Diller",
"Ravi Patel (actor)",
"Simon Rex",
"Jason Biggs",
"Ahmed Ahmed",
"Matt Groening",
"Rhod Gilbert",
"Awkwafina",
"Jackie Schaffer",
"Steve Zaragoza",
"Stubby Kaye",
"Christopher Walken",
"Lou Albano",
"Bryan Callen",
"Beth Behrs",
"Chris Sugden",
"Tien Tran",
"Sarah Sherman",
"Johnny Pemberton",
"Takeshi Kitano",
"John Byner",
"List of Puerto Rican comedians",
"Richard Schull",
"Laurence Rickard",
"Chris Parnell",
"Mayce Galoni",
"John Krasinski",
"Hannah Einbinder",
"Huntz Hall",
"John Ratzenberger",
"Katey Sagal",
"Will Sasso",
"Jeremy Hardy",
"Kapil Talwalkar",
"Eddie Griffin",
"Janet Varney",
"Angela V. Shelton",
"Alex Borstein",
"Jon Heder",
"Eli Roth",
"Jake Johnson",
"David Walton (actor)",
"Isabel Sanford",
"Woody Allen",
"Tom Bergeron",
"Fancy Ray",
"Shantira Jackson",
"Steve Buscemi",
"Jillian Bell",
"Mike Judge",
"Emma Thompson",
"Alan Carney",
"Johnny Galecki",
"Jack McBrayer",
"Maine Mendoza",
"Tone Bell",
"Tina Fey",
"Nelson Franklin",
"Bob Newhart",
"Megan Amram",
"George Lopez",
"Christina Pazsitzky",
"Jack Pearl",
"Richard Christy",
"Mick Foley",
"Bobby Lee",
"Paul Merton",
"Jimmy O. Yang",
"Henry Zebrowski",
"Zero Mostel",
"Josh Cooke",
"Brian Scolaro",
"James Hong",
"Charlie Day",
"German Moreno",
"Zac Oyama",
"Donald O'Connor",
"Doug Mellard",
"Paula Pell",
"David Ossman",
"Tim Bagley",
"Celia Pacquola",
"Kenneth Williams",
"George Carl",
"Dave Mordal",
"Ayo Edebiri",
"Sal Vulcano",
"Bob Hope",
"Ross Noble",
"\"Hamburger\" Jones",
"David Schwimmer",
"Wendi McLendon-Covey",
"Thomas Mikal Ford",
"Richard Hearne",
"Simon Munnery",
"Smothers Brothers",
"Ben Feldman",
"Al Murray",
"Rick Roman",
"Chris Fleming (comedian)",
"Lamorne Morris",
"Lizz Winstead",
"John Leguizamo",
"Bonnie McFarlane",
"Russell Brand",
"Jay Mohr",
"Stephnie Weir",
"Tom Stourton",
"Sheb Wooley",
"Grace Helbig",
"Julia Duffy",
"Donnell Rawlings",
"Morgan Murphy (comedian)",
"Peter Sallis",
"Sarayu Blue",
"Leon Schuster",
"Verne Troyer",
"Samm Levine",
"Tony Cavalero",
"Bill Corbett",
"Thomas Haden Church",
"Rich Eisen",
"Markus Maria Profitlich",
"Alec Mapa",
"June Whitfield",
"Elaine Hendrix",
"Eugene Domingo",
"Jackie Gleason",
"Marty Feldman",
"Kerri Kenney-Silver",
"Chris Redd",
"Seth MacFarlane",
"Natasha Behnam",
"Stevie Ryan",
"Little Britain (sketch show)",
"Jolina Magdangal",
"Feodor Chin",
"Jonathan Coleman (presenter)",
"Anjelah Johnson",
"Roy Walker (comedian)",
"Annie Mumolo",
"Ted Danson",
"Vicki Lewis",
"Robin Duke",
"Pablo Francisco",
"Luke Null",
"Pamela Adlon",
"Nathan Fielder",
"Brian McKim",
"Michael Hitchcock",
"Bülent Ceylan",
"Patricia Routledge",
"Scotland the What?",
"Stephen Rannazzisi",
"Mayim Bialik",
"Caroline Quentin",
"Billy Van",
"Mitch Hedberg",
"Tony Hinchcliffe",
"Tariq Teddy",
"Ryan O'Connell",
"The Goons",
"JB Smoove",
"Jeff Foxworthy",
"Kirk Cameron",
"Duncan Norvelle",
"Jessica Stroup",
"Mitch Fatel",
"Kevin Nalty",
"Todd Glass",
"Eddie Izzard",
"The Kipper Kids",
"Daisy Fuentes",
"Gallagher (comedian)",
"Ronnie Schell",
"John Reynolds (actor)",
"Steve Steen",
"Nell Carter",
"Michael Schur",
"Jason Narvy",
"Martin and Lewis",
"Abe Burrows",
"Denny Siegel",
"Paul F. Tompkins",
"Phil Nichol",
"Eva Gabor",
"Betty Garrett",
"Emil Wakim",
"Ford Sterling",
"Teachers (2016 TV series)",
"Joshua Seth",
"Trey Parker",
"Henny Youngman",
"Craig Kilborn",
"Lisa Foiles",
"Rebecca Root",
"Tay Zonday",
"Sheryl Underwood",
"Julia Sawalha",
"Brian Stepanek",
"Peter Scolari",
"Melinda Hill",
"Greg Proops",
"Vince Vaughn",
"Eric Bauza",
"Billy Connolly",
"Josh Robert Thompson",
"Axel Stein",
"Larry Owens (actor)",
"Alexandra Petri",
"Pert Kelton",
"CollegeHumor",
"Phil Hartman",
"Lenny Rush",
"Andrew Schulz",
"Andrea Rosen",
"Drake Sather",
"William Jackson Harper",
"Zoe Lister-Jones",
"Redd Foxx",
"Michael Urie",
"Mike McGlone",
"Leo Gorcey",
"Alan King",
"Clifton Davis",
"Jeff Dunham",
"Paul Lynde",
"Kevin Bishop",
"Ryan Stout",
"Dennis Dugan",
"Ellen Cleghorne",
"Billy Gardell",
"Roy Kinnear",
"Rajiv Satyal",
"Victoria Wood",
"David Krumholtz",
"Candace Brown",
"Drew Lynch",
"Christoph Maria Herbst",
"Lloyd Hamilton",
"Don Most",
"Jim O'Heir",
"Jon Hamm",
"Zachary Levi",
"Phil Austin",
"Smith and Dale",
"Rose Byrne",
"Matt Iseman",
"Please Don't Destroy",
"Jim Varney",
"Sabrina Jalees",
"Matt Forde",
"Danielle Bisutti",
"Jemaine Clement",
"Bridey Elliott",
"David Faustino",
"Paul Gilmartin",
"Jason Woliner",
"Rodney Carrington",
"Patrick McKenna",
"Tim Brooke-Taylor",
"Stanley Baxter",
"Nancy Sullivan (American actress)",
"Kiray",
"Jon Reep",
"Ray Stevens",
"Harris Wittels",
"Katie Aselton",
"Marina Franklin",
"Kyle Howard",
"Justin Theroux",
"Hugh Laurie",
"Cedric the Entertainer",
"Sue Bond",
"Rene Gube",
"Ogie Alcasid",
"Totie Fields",
"Linda Lavin",
"Elvis Duran",
"Scott MacArthur",
"Paul Schrier",
"Terence Lee",
"Rajpal Yadav",
"Adam Ferrara",
"David Hyde Pierce",
"Sue Galloway",
"Wyatt Cenac",
"Shecky Greene",
"Garrett Morris",
"John DiMaggio",
"Liz Feldman",
"Charles \"Chic\" Sale",
"Ed Weeks",
"Margaret Smith (comedian)",
"Zeppo Marx",
"Nate Torrence",
"Garry Shandling",
"Rosie O'Donnell",
"Patti Deutsch",
"Johnny Vegas",
"David Cross",
"Howard Stern",
"Dan Goor",
"Ted Robbins",
"Dave McCary",
"Rebecca Metz",
"Mark Duplass",
"London Hughes",
"Mike Cabellon",
"Freddie Roman",
"Peter Sellers",
"El Brendel",
"Helen Atkinson-Wood",
"Mark Lowry",
"John C. McGinley",
"Sanjay Dutt",
"Joe Lycett",
"Dirk Bach",
"Stiller and Meara",
"Taran Killam",
"David Groh",
"David Spade",
"Jerry Seinfeld",
"Nora Dunn",
"Betty Marsden",
"Mila Kunis",
"Galton and Simpson",
"Noel Murphy (comedian)",
"David O'Doherty",
"Gilda Radner",
"Rob Riggle",
"Lea DeLaria",
"Riki Lindhome",
"Marijuana Logues",
"Vic Henley",
"Gabbie Hanna",
"Dave Foley",
"Damon Wayans Jr.",
"Imogene Coca",
"The Amazing Johnathan",
"Aida Osman",
"Tom Dreesen",
"Pat Paulsen",
"Megan Ganz",
"Echo Kellum",
"Tom Gleeson",
"Busy Philipps",
"Doug Brochu",
"Adam Goldberg",
"Chris Porter (comedian)",
"Dax Shepard",
"John Early (comedian)",
"Bea Benaderet",
"Andy Parsons",
"Rachel Sennott",
"Matthew Lillard",
"Rich Vos",
"Jason Francisco",
"Laurie Kilmartin",
"Paul Rudd",
"Liz Carey",
"Margaret Cho",
"Tyler Labine",
"Jenny Yang (comedian)",
"Preston Lacy",
"Lauren Laverne",
"Barats and Bereta",
"Anna Drezen",
"Anna Konkle",
"Adam Brody",
"Richard Moll",
"Michael O'Donoghue",
"List of Norwegian comedians",
"Groucho Marx",
"Buster Merryfield",
"Nate Corddry",
"Matt Richardson",
"Eric Stonestreet",
"Jamie Lee (comedian)",
"Beth Lapides",
"Cloris Leachman",
"Gary Valentine",
"Ben Turpin",
"Alec Sulkin",
"Robin Ince",
"Don Rickles",
"Henning Wehn",
"Eleanor Morton (comedian)",
"Bert Kreischer",
"Dan Harmon",
"Hannibal Buress",
"Elizabeth Montgomery",
"Not Ready for Prime-Time Players",
"Joy Behar",
"Charlie Callas",
"Gil Ozeri",
"Jay London",
"Kate Flannery",
"Bill Maynard",
"Paul Foot (comedian)",
"Ivor Dembina",
"Ken Davitian",
"Johnny Knoxville",
"Eric McCormack",
"Luke Wilson",
"Tom Ballard (comedian)",
"Jimmy Durante",
"Brittany Furlan",
"Jay Chanoine",
"Bess Kalb",
"Finesse Mitchell",
"Steve Smith (comedian)",
"Wally Vernon",
"List of Mexican comedians",
"Mark Thomas",
"Josie Totah",
"Leigh Francis",
"Mr Lawrence",
"Justin Roiland",
"Lilly Singh",
"Heather McMahan",
"Monica Padman",
"Gavin MacLeod",
"Dannah Phirman",
"Pat Morita",
"David Ogden Stiers",
"Jason Segel",
"Wanda Sykes",
"Angelica Panganiban",
"Sam Pancake",
"Khary Payton",
"Arj Barker",
"Chris Wylde",
"Jack Burns",
"Nick Cannon",
"Luenell",
"Kausar Mohammed",
"Simon Rich",
"Paul Reiser",
"Amy Schumer",
"Jamie Kaler",
"Richard Fancy",
"Ziwe Fumudoh",
"Rob Reiner",
"Jamar Neighbors",
"Michael Richards",
"Jean Smart",
"Chris Klein (actor)",
"Bryan Safi",
"Holly Willoughby",
"John Cho",
"Chris Knutson",
"Dylan Mandlsohn",
"Bob Wiltfong",
"Dolphy",
"Elizabeth Marrero",
"Alex Agnew",
"Brian McConnachie",
"Elvira Kurt",
"Whitney Chitwood",
"Broti Gupta",
"Bobb'e J. Thompson",
"James Adomian",
"Judy Graubart",
"Mike Birbiglia",
"French Stewart",
"Mario Joyner",
"Nick Swardson",
"Orlando Jones",
"Dave Hill (comedian)",
"Lou Moon",
"Steve Oram",
"Devon Walker (comedian)",
"Randall Park",
"George Roper",
"Negin Farsad",
"Jay Larson",
"Chelsey Crisp",
"Amy Poehler",
"Jay Pharoah",
"Fred MacMurray",
"Jon Lovitz",
"Sabrina Brier",
"Geri Jewell",
"Mary Scheer",
"Gina Riley",
"The Try Guys",
"Kurt Braunohler",
"Will Rogers",
"Ann Morgan Guilbert",
"Joe Pasquale",
"Courteney Cox",
"Tom Lehrer",
"Jeff Doucette",
"Emily Spivey",
"Volodymyr Zelenskyy",
"Jake Paul",
"Lesley Arfin",
"Jim Florentine",
"Barbara Dunkelman",
"Dustin Gee",
"Aditi Mittal",
"Russell Peters",
"Scott Aukerman",
"Pauline Quirke",
"Aaron Yonda",
"Griffin McElroy",
"Tim Moore (comedian)",
"Ed Asner",
"Bridget Christie",
"Willis Hall",
"Jon Lajoie",
"Sarah Hadland",
"Heinz Erhardt",
"Patricia Lake",
"Michael Legge (comedian)",
"Ingrid Guimarães",
"Charlie Ruggles",
"Neil Flynn",
"Jim Downey (comedian)",
"Jackie Kashian",
"Paul O'Grady",
"R-Truth",
"Ilka Bessin",
"Eugene Levy",
"Jane Krakowski",
"Murtaza Hassan",
"Joey de Leon",
"Gary Gulman",
"Kevin Ruf",
"Cathy Ladman",
"Broken Lizard",
"Justina Machado",
"Ted Healy",
"Richard Belzer",
"Andrea Savage",
"Nick Bakay",
"Dave Anthony",
"Maurice LaMarche",
"Paul and Storm",
"Jeremy Lloyd",
"Jonathan Katz",
"LaVan Davis",
"Boothby Graffoe (comedian)",
"Sandra Bullock",
"Stacey Grenrock-Woods",
"Chris Pratt",
"Alfonso Ribeiro",
"Lee Evans (comedian)",
"Wigald Boning",
"Annette Frier",
"Kenice Mobley",
"Jeff Schaffer",
"Terry Jones",
"Jay Duplass",
"Jessica Delfino",
"Tom Lenk",
"Brandon T. Jackson",
"Fred Stoller",
"Robert Guillaume",
"Jared Freid",
"Mena Suvari",
"Hasan Minhaj",
"Tichina Arnold",
"Donald Faison",
"Tatanka Means",
"Jared Keeso",
"Henry Naylor",
"Cheri Oteri",
"Dan Bakkedahl",
"Jason Mewes",
"Tricia O'Kelley",
"Michael McIntyre",
"Natasha Rothwell",
"Paul Provenza",
"Michael Bunin",
"Helge Schneider",
"Geraldine Viswanathan",
"Mo Gilligan",
"Siobhan Fallon Hogan",
"Chokoleit",
"Bob Denver",
"Molly Erdman",
"Matt Koff",
"Ryan Reynolds",
"Harry Hill",
"John Roberts (actor)",
"Vic Michaelis",
"Robert Webb",
"Maz Jobrani",
"Jack Carroll (comedian)",
"Mike Henry (voice actor)",
"Katya Zamolodchikova",
"Matt Davis (comedian)",
"Drew Tarver",
"Rob Delaney",
"Daniel Dickey",
"John Catucci",
"Ron Howard",
"Rose Marie",
"Nikki Glaser",
"Charlie Murphy (actor)",
"Tiya Sircar",
"Adam Campbell (actor)",
"Terry-Thomas",
"Siw Anita Andersen",
"Glen Powell",
"Paul Rust",
"River Butcher",
"DeStorm Power",
"Dave Willis (comedian)",
"Dai Henwood",
"Enrico Colantoni",
"Josh Peck",
"Holly Walsh",
"Eric Bana",
"Kevin Murphy (actor)",
"Tyler Ritter",
"Burns and Allen",
"Blake Anderson",
"Jan Hooks",
"Guy Torry",
"Kirk Fox",
"Kevin Barnett (comedian)",
"Dan Castellaneta",
"Shaun Weiss",
"Mike Hayley",
"Bob Monkhouse",
"Ruth Buzzi",
"George Sidney (actor)",
"Dave Willis",
"Amber Ruffin",
"Sam Simmons (comedian)",
"D.C. Benny",
"Trevor Noah",
"Vicco von Bülow",
"Jay Thomas",
"Julie Kavner",
"Daniel Rigby",
"Rashida Jones",
"Burnie Burns",
"Randy Rainbow",
"Katie Nolan",
"Adam Pally",
"Fred Allen",
"Charley Chase",
"Dick Emery",
"Faith Ford",
"Rocky LaPorte",
"Daniel Lobell",
"Nik Dodani",
"Frank DeCaro",
"Cem Yılmaz",
"Flight of the Conchords",
"Ed Helms",
"Adam Busch",
"Marlo Thomas",
"Adam Ray (comedian)",
"Dave Thompson (comedian)",
"Jay Oakerson",
"Michelle Buteau",
"Sean Evans (interviewer)",
"Paul Whitehouse",
"Heather McDonald",
"Daniel Breaker",
"Jade Catta-Preta",
"Jason Byrne (comedian)",
"Shelley Duvall",
"Santino Marella",
"Fanny Brice",
"John Pinette",
"Rosie Shuster",
"Beyond the Fringe",
"Michael Che",
"Rick Glassman",
"Adam Lowitt",
"Lil Dicky",
"Jan Murray",
"Naveed Mahbub",
"Allyn Rachel",
"Guy Branum",
"Dave Coulier",
"Kevin Hart",
"Ole Olsen (comedian)",
"Steven Yeun",
"Daniel Humbarger",
"Ralf Little",
"Kunal Nayyar",
"David Sedaris",
"Hank Azaria",
"Judd Hirsch",
"John C. Reilly",
"Noah Munck",
"Jimmy Shubert",
"Rose Abdoo",
"comedy",
"Howie Mandel",
"Paul Tonkinson",
"Bobby Farrelly",
"Bill Cosby",
"Simon Helberg",
"Gerardo Sofovich",
"Catherine O'Hara",
"Markiplier",
"Ruth Wallis",
"Joey Bishop",
"King Bach",
"Danielle Schneider",
"Hard 'n Phirm",
"Suli McCullough",
"Barbara Jo Allen",
"Graham Fellowes",
"Mike Lookinland",
"Avery Schreiber",
"Tika Sumpter",
"Michael Jeter",
"Jenny McCarthy",
"Nick Nemeroff",
"America Ferrera",
"Rue McClanahan",
"Norman Wisdom",
"The Breakfast Club (radio show)",
"Ross Shafer",
"Brian Gallivan",
"David Letterman",
"Demond Wilson",
"Hallie Haglund",
"Mel Brooks",
"Kirby Howell-Baptiste",
"Andy Buckley",
"Gabe Kaplan",
"Lena Dunham",
"Eduardo Franco (actor)",
"Rhona Cameron",
"Pauly Shore",
"Jason Schwartzman",
"John Caparulo",
"Leslie Bibb",
"Carol Kane",
"Kim Woodburn",
"Josh Charles",
"Naomi Ekperigin",
"Randy Santiago",
"Daniel Roebuck",
"Kym Whitley",
"Andy Lee (comedian)",
"Kevin Nealon",
"Barry Williams (actor)",
"Kim Coles",
"Rhys Nicholson",
"Alex Rubens",
"Lennon Parham",
"Atsuko Okatsuka",
"Chris Messina",
"Phil Silvers",
"Louie Anderson",
"Bob Uecker",
"Dara Ó Briain",
"Louis C.K.",
"Dave King (actor)",
"Raven-Symoné",
"Victor Borge",
"Natalie Palamides",
"Manilyn Reynes",
"Tommy Chong",
"Allison Tolman",
"Lisa Donovan",
"Michael Patrick Jann",
"DJ Qualls",
"Ben Stein",
"Andy Smart",
"Paul Strickland",
"Rider Strong",
"Andi Osho",
"Pat Kilbane",
"Jason John Whitehead",
"Megan Gailey",
"Bec Hill",
"Krista Allen",
"Carolin Kebekus",
"Sarah Kendall",
"Jason Love (comedian)",
"Eddie Murphy",
"Ann Sothern",
"Marc Summers",
"David Koechner",
"Chris Maddock",
"Michael Pritchard (comedian)",
"Marc Yaffee",
"Archie Campbell (comedian)",
"Trae Crowder",
"Tony Rock",
"Keegan-Michael Key",
"Laurel and Hardy",
"Tracey Ullman",
"John Larroquette",
"Christa Miller",
"Melissa Villaseñor",
"Bernadette Peters",
"Jimmy Fowlie",
"Matt Berry",
"Fred Wedlock",
"Suzanne Somers",
"Bill Murray",
"Manny Jacinto",
"Siobhan Thompson",
"Kathy Kinney",
"Judy Canova",
"Jon Barinholtz",
"Slappy White",
"Sam Reich",
"James Corden",
"Katie Finneran",
"George Lindsey",
"Tim Herlihy",
"Jon Stewart",
"Juan Pablo Di Pace",
"Harith Iskander",
"William Frawley",
"Elise Cavanna",
"Jack Klugman",
"Harry Langdon",
"Yvonne Orji",
"Kathryn Hahn",
"Steve Agee",
"Gavin Free",
"Hans-Joachim Heist",
"Nolan North",
"Whindersson Nunes",
"Kenny and Keith Lucas",
"Ana Fabrega",
"Brother Theodore",
"Todd Bridges",
"Abbott and Costello",
"Scott Capurro",
"Tim and Eric",
"Stavros Halkias",
"Rob Corddry",
"Rosalind Russell",
"Michael Blackson",
"Anthony Anderson",
"Matt Lucas",
"Joe DeRosa (comedian)",
"Josh Thomas (comedian)",
"Alia Shawkat",
"Abby Elliott",
"Charlamagne tha God",
"W. C. Fields",
"Martha Raye",
"Josh Sundquist",
"Chris Tucker",
"Alan Carr",
"Mekki Leeper",
"Scott Thompson (comedian)",
"Carlos Santos (comedian)",
"Joey Gay",
"Cristela Alonzo",
"Gad Elmaleh",
"Chris Witaske",
"Alison Becker",
"Bob Saget",
"Daniel Curtis Lee",
"Franchesca Ramsey",
"Brian Baumgartner",
"Ralphie May",
"Coleen Nolan",
"Matt Frewer",
"Kavin Jayaram",
"Joe Robinson (radio personality)",
"Matthew Gray Gubler",
"David Wain",
"Annaleigh Ashford",
"Connie Booth",
"Alberto Olmedo",
"Lucy Porter",
"Mary Mack (comedian)",
"Erica Ash",
"Harpo Marx",
"Al Franken",
"Stan Freberg",
"Amy Sedaris",
"Lauren Ash",
"Jill Talley",
"Chris Hardwick",
"Ray Romano",
"Nova Villa",
"Robin Williams",
"Andrea Martin",
"Sarah Jessica Parker",
"Stephen Colbert",
"Tom Poston",
"Bobby Heenan",
"Jack Pepper",
"Jerrod Carmichael",
"Arthur Askey",
"Seth Rogen",
"Matt Friend",
"Paul McCullough",
"John Keister (comedian)",
"Paul Nardizzi",
"Chris Morris (satirist)",
"Josh McDermitt",
"Tim Robinson (comedian)",
"Eric André",
"Kira Soltanovich",
"List of New York Improv comedians",
"Sarah Keyworth",
"Chris Distefano",
"Tony Rosato",
"Papa CJ",
"Bassem Youssef",
"Ennis Esmer",
"Paul Reubens",
"Denis Norden",
"Jenny Slate",
"Nico Santos (actor)",
"Edi Patterson",
"Kevin James",
"Patrick Warburton",
"Asher Grodman",
"Paul Mooney (comedian)",
"Christina Moore",
"Tom Rhodes",
"Kobi Libii",
"Nikki Cox",
"Billy Eichner",
"Eric Wareheim",
"Rose McIver",
"Stefan Raab",
"Pamela Stephenson",
"Enchong Dee",
"Samantha Bee",
"Hayden Schlossberg",
"Chris Powell (comedian)",
"Sandra Gould",
"Dwight York (comedian)",
"Johnny Speight",
"Zach Barack",
"Skip Hinnant",
"Elliott Morgan",
"Judy Tenuta",
"Natalie Tran",
"Mo Rocca",
"Sebastian Maniscalco",
"Dick Van Dyke",
"Jacob Wysocki",
"Ryan Dunn",
"Jake Johannsen",
"Mark DeCarlo",
"Darci Lynne",
"Tony Barbieri",
"Ali Liebegott",
"Jim Breuer",
"Ryan Drummond",
"Sean Clements",
"Greg Kinnear",
"Seán Cullen",
"Craig Shoemaker",
"Maeve Higgins",
"Michael Mittermeier",
"Million Dollar Extreme",
"Jeff Grace",
"Kaye Ballard",
"Rich Talarico",
"Jayson Gainza",
"Caitlin McGee",
"Tommy Dewey",
"Lewis Schaffer",
"Brian Jordan Alvarez",
"Iris Bahr",
"Flip Wilson",
"Loren Bouchard",
"Spoken Reasons",
"Larry Drake",
"Rufa Mae Quinto",
"Wilfried Schmickler",
"Richard Dawson",
"Mehran Modiri",
"Ali Wong",
"Jaime Camil",
"Matthew Moy",
"Michael J. Fox",
"Justin Hires",
"Grey DeLisle",
"Jon Vitti",
"George Carlin",
"Sherri Shepherd",
"Red Skelton",
"Rolo Puente",
"Adele Givens",
"Bret McKenzie",
"Tara Reid",
"Dick Cavett",
"Madeline Kahn",
"Dick Van Patten",
"Joji (musician)",
"Mike Drucker",
"Linda Smith (comedian)",
"Thomas Lennon (actor)",
"Hollywood Zakoshisyoh",
"E.G. Daily",
"S. J. Perelman",
"Jon Richardson",
"Desus Nice",
"Leslie Nielsen",
"Eddie Albert",
"Graeme Garden",
"Sherry Cola",
"Joey Faye",
"Scott Seiss",
"Marsha Warfield",
"Richie Moriarty",
"Ophira Eisenberg",
"Essence Atkins",
"Edie McClurg",
"Nancy Walker",
"Chico Marx",
"Shappi Khorsandi",
"Ian Gomez",
"Jane Curtin",
"Michael \"Atters\" Attree",
"Bill Irwin",
"Florence Mills",
"Brian Doyle-Murray",
"Dylan Moran",
"Des Bishop",
"Kenny Everett",
"Jack Black",
"Nawaal Akram",
"Molly Kearney",
"Jennifer Aniston",
"Alfred Marks",
"Regis Philbin",
"Felipe Esparza",
"Paul Walter Hauser",
"Anthony Michael Hall",
"Richard Karn",
"Rebekka Johnson",
"Kevin Kline",
"Eric Sykes",
"Rachel Specter",
"Hugo Sofovich",
"Ed McMahon",
"Barbara Schöneberger",
"Rob Brydon",
"Swoosie Kurtz",
"Peter Farrelly",
"Dominic Monaghan",
"Ryan Belleville",
"Tahj Mowry",
"Rosa Salazar",
"Paul Hogan",
"Tituss Burgess",
"Mark O'Donnell",
"Lea Thompson",
"Misha Collins",
"Frankie Quiñones",
"Michael McCullers",
"Patty Rosborough",
"Mary Steenburgen",
"Alex Kapp Horner",
"Lucy Punch",
"Heather Anne Campbell",
"Khalid Abbas Dar",
"Reginald VelJohnson",
"Tony Shalhoub",
"David Croft (TV producer)",
"Billy Gilbert",
"Rich Blomquist",
"Michael Angarano",
"Ben Roy",
"Nasser Al Qasabi",
"Julian Barratt",
"Carlos Villagrán",
"Carla Lane",
"Kate McKinnon",
"Ashley Nicole Black",
"Roy Wood Jr.",
"Albert Ritz",
"Matteo Lane",
"Amy Hill",
"Oliver Hardy",
"Ryan McPartlin",
"Harry Worth (actor, born 1917)",
"Wayne Brady",
"Scooter Magruder",
"David Grant (singer)",
"Kim Possible (film)",
"Nicholas Lyndhurst",
"Barret Swatek",
"Steven Wright",
"Ion Perez",
"Denny Willis",
"Michael Cassidy (actor)",
"Steph Tolev",
"Punam Patel",
"Liza Snyder",
"John Sullivan (writer)",
"Luis Manzano",
"Retta",
"Henry Rollins",
"Brooks Wheelan",
"Christina Hendricks",
"Michael Keaton",
"Christopher Gorham",
"Amber Stevens West",
"Kyle Bornheimer",
"Dan Fogler",
"Jan McInnis",
"Anna Akana",
"Christopher Guest",
"Mike Yarwood",
"Rags Ragland",
"Erik Myers",
"Bobby Cannavale",
"Twink Caplan",
"Zach Braff",
"John Candy",
"John Paragon",
"ZaSu Pitts",
"Jasper Carrott",
"Wendy van Dijk",
"James Cunningham (comedian)",
"Tom Gerhardt",
"Barney Williams (actor)",
"Leslie Jordan",
"Gary Waldhorn",
"Duke Mitchell",
"Bill Chott",
"David Paymer",
"Ariana Guido",
"Dick Clement",
"Greg Gutfeld",
"John Hegley",
"Matt Hobby",
"Danny Pudi",
"Frankie Pace",
"Tisha Campbell",
"Jay Jason",
"Tallie Medel",
"Paul Taylor (comedian)",
"Bayani Agbayani",
"Tim Allen",
"Daniel Franzese",
"Meredith Hagner",
"Larry Fine",
"John Francis Daley",
"Robert Ben Garant",
"Olivia Colman",
"surname",
"Janeane Garofalo",
"Dan Mazer",
"Jamie Demetriou",
"Rob Lowe",
"Trevor Peacock",
"Jake Hurwitz",
"Don Friesen",
"Kelly Ripa",
"Bert Williams",
"Brittani Nichols",
"Clark and McCullough",
"Ed Lauter",
"Andy Berman",
"Vhong Navarro",
"Christine Ebersole",
"Lori Alan",
"Stephanie Hodge",
"Eliot Wald",
"Jim Parsons",
"Simon Farnaby",
"Rich Fulcher",
"Oliver Hudson",
"Will Smith (comedian)",
"Bob Odenkirk",
"Don McMillan",
"Missi Pyle",
"Andrew Rannells",
"Sophie Buddle",
"Mathias Richling",
"Jonah Hill",
"Justin Willman",
"Reid Scott (actor)",
"Brandon Mychal Smith",
"Daniel Kaluuya",
"Phil Kay",
"Navin Prabhakar",
"Graham Kennedy",
"Evan Goldberg",
"Larry Miller (comedian)",
"Celeste Barber",
"Amy Anderson (comedian)",
"Mackenzie Crook",
"Tim Dillon (comedian)",
"Hugh Herbert",
"Esther Schweins",
"Mary Gross",
"Alan Tudyk",
"Stephen Curry (comedian)",
"Bea Arthur",
"Bill Dana",
"Derek Waters",
"Upright Citizens Brigade",
"Isabel Fay",
"Scott Grimes",
"Jaime Pressly",
"Shemp Howard",
"Robert Newman (comedian)",
"Laura Kightlinger",
"Judi Love",
"Douglas Adams",
"Ryan Pinkston",
"Danny McBride",
"Jack Rosenthal",
"Prunella Scales",
"Adam Resnick",
"John Ennis (actor)",
"Matt Kirshen",
"The Little Rascals",
"Christine Ko",
"Larry Murphy (actor)",
"Dickie Henderson",
"Matt Jones (actor)",
"John Crist (comedian)",
"Bobby Pickett",
"Frank Whaley",
"Alice Fraser",
"Ethan Embry",
"JonTron",
"Grace Parra",
"Janey Godley",
"Craig Ferguson",
"Bobby Clark (comedian)",
"Greg Davies",
"Ali Farahnakian",
"Shane Gillis",
"Gary Owen (comedian)",
"Glenn Shadix",
"David Huntsberger",
"Kel Mitchell",
"Oliver Welke",
"Mike DeStefano",
"Kether Donohue",
"Daheli Hall",
"Sarah Schneider",
"Lin Shaye",
"W. Kamau Bell",
"Natasha Lyonne",
"Bob & Doug McKenzie",
"Daniella Pineda",
"Frankie Howerd",
"Kevin Chamberlin",
"Kai Tier",
"Lori Beth Denberg",
"Penn & Teller",
"Murray Miller",
"Chris D'Elia",
"Josh Lawson",
"Doon Mackichan",
"Patrice O'Neal",
"Connor Ratliff",
"Michael Rubens",
"Debra Wilson",
"Richard Pryor",
"Jerry O'Connell",
"Paula Poundstone",
"Frank Conniff",
"Topher Grace",
"Argus Hamilton",
"David Steinberg",
"Greg Hemphill",
"Wally Brown",
"Natasia Demetriou",
"Rickey Smiley",
"Les Luthiers",
"Royal Canadian Air Farce",
"Tom Hanks",
"Tom Shillue",
"Wendy Williams",
"Amanda Crew",
"Sklar Brothers",
"Patricia Heaton",
"Alexander Armstrong",
"David Brenner",
"List of musical comedians",
"Genevieve (actress)",
"Cliff Cash",
"Vicki Lawrence",
"Lake Bell",
"Ted Chippington",
"Steve Bodow",
"Kenan Thompson",
"Trevor Wallace",
"Mike Epps",
"Megan Mullally",
"Iliza Shlesinger",
"Ned Fulmer",
"Ray Goulding",
"Chris Estrada (comedian)",
"Joel McHale",
"Dada Kondke",
"Vanessa Bayer",
"Tuesday Vargas",
"Eden Sher",
"Joely Fisher",
"Billy West",
"Ron Sparks (comedian)",
"Harriet Braine",
"John O'Hurley",
"Ashley Padilla",
"Jon Daly (comedian)",
"James Thurber",
"DJ Pryor",
"Joseph Marcell",
"Betsy Sodaro",
"Jason Ritter",
"Don Porter",
"Charles Grodin",
"Andy Kaufman",
"Keith Wann",
"Ty Burrell",
"Debra DiGiovanni",
"Harley Morenstein",
"Aisling Bea",
"Jenna Elfman",
"Cardis Cardell Willis",
"Mike Castle (actor)",
"Michelle Wolf",
"Ely Henry",
"Yakov Smirnoff",
"Allen Payne",
"Richard Ayoade",
"Allan Havey",
"Ben Bailey",
"Mike Myers",
"Larry the Cable Guy",
"Cole Escola",
"Maria Thayer",
"Allyce Beasley",
"Ethan Suplee",
"Chris Tallman",
"Reeves and Mortimer",
"Hayes Davenport",
"James Franco",
"John Goodman",
"Nina Wadia",
"Calico Cooper",
"Darrell Hammond",
"T.J. Jagodowski",
"Jon Lovett",
"John Viener",
"Tig Notaro",
"Kirsten Gronfield",
"Adam Montoya",
"Bradley Whitford",
"Stefanie Wilder-Taylor",
"Dustin Ybarra",
"Lisa Kudrow",
"Andy Erikson",
"Annie Potts",
"Wally Bayola",
"Leah Remini",
"Mae Martin",
"Joe Randazzo",
"Loni Love",
"Susanne Blakeslee",
"Jackie Mason",
"Agnes Moorehead",
"Matt Morgan (comedian)",
"Marcella Arguello",
"Louis Ramey",
"Mike Warnke",
"Kate Quigley",
"John Lehr",
"Judd Apatow",
"Imran Yusuf",
"Chris Eckert",
"Mitch Rouse",
"Steve Harvey",
"Cheech Marin",
"Nasim Pedrad",
"Rosebud Baker",
"Robert Hegyes",
"Mark Steel",
"Mindy Sterling",
"Marc Evan Jackson",
"Portia de Rossi",
"Bill Oddie",
"Judy Greer",
"Annie Korzen",
"The Minnesota Wrecking Crew",
"Jimmy Carr",
"David A. Arnold",
"Jimmy Kimmel",
"Gilbert Gottfried",
"Ina Müller",
"Nick Kroll",
"John Milhiser",
"Larry Romano",
"Sara Gilbert",
"Christopher Knight (actor)",
"Rachel Dratch",
"John Henton",
"Mitch Mullany",
"Charlie Sheen",
"Joe Thomas (actor)",
"Brad Williams (comedian)",
"Jane Horrocks",
"Rich Hall",
"Appurv Gupta",
"Matt Cook (actor)",
"T.J. Miller",
"David Mandel",
"Mary Lynn Rajskub",
"Jenifer Lewis",
"Laraine Newman",
"Brent Weinbach",
"Mason Williams",
"Max Boyce",
"Lucas Cruikshank",
"Ruth Langsford",
"Cecily Strong",
"Sean Kent",
"Murray Hill (performer)",
"Burt Reynolds",
"Dave Hughes",
"Jason Lee (actor)",
"Lynne Koplitz",
"Leanne Morgan",
"Ryan Bang",
"Zainab Johnson",
"George Formby",
"John Cleese",
"Christopher Lloyd",
"Greg London",
"Renée Taylor",
"Ron Pederson",
"Bobby Moynihan",
"Herlene Budol",
"Martin Short",
"JR Reed (actor)",
"Danny Bonaduce",
"Jeff Altman",
"Vinny Vella",
"Milo Ventimiglia",
"Buboy Villar",
"Ray Walston",
"Jerry Van Dyke",
"Tenacious D",
"Estonia",
"Felicia Michaels",
"Jerry Lewis",
"Alonzo Bodden",
"Jessi Klein",
"Adam Sandler",
"Sean Masterson",
"Alex Gonzaga",
"George Wallace (Australian comedian)",
"Rob Dyrdek",
"Jeff Richmond",
"Zack Fox",
"Mickey Katz",
"Mario Barth",
"Shirley Jones",
"Nate Bargatze",
"Julie Klausner",
"Mark Blankfield",
"List of Shake It Up characters",
"Eric Lutes",
"Dean Edwards",
"Pete and Dud",
"Julia Louis-Dreyfus",
"Alan Alda",
"Steve Zissis",
"Gary Anthony Williams",
"Mukesh Tiwari",
"Bill Kirchenbauer",
"Jean Dujardin",
"John Solomon (writer)",
"Andrea Anders",
"Maggie Carey",
"Kathy Greenwood",
"Mike Wozniak",
"List of Indian comedians",
"Dave Holmes (actor)",
"Ian Roberts (American actor)",
"Rhea Perlman",
"Bianca Del Rio",
"Henry Winkler",
"Nore Davis",
"Jes Tom",
"Tiffany Haddish",
"Shayne Topp",
"Tracee Ellis Ross",
"Todd Barry",
"Harald Schmidt",
"Brad Garrett",
"Christine Taylor",
"Nick Hancock",
"Nicole Arbour",
"Robin Padilla",
"Ryan Higa",
"Liza Koshy",
"Joe Mande",
"Sarah Thyre",
"Bonzo Dog Doo-Dah Band",
"Bob Nelson (comedian)",
"George Takei",
"Rudy Ray Moore",
"Justin Spitzer",
"Amy Hoggart",
"Frank-Markus Barwasser",
"Alan Davies",
"Ben Blue",
"Ron Bennington",
"Jena Friedman",
"Kurt Metzger",
"Tony Revolori",
"Tincho Zabala",
"Betty Hutton",
"Jameela Jamil",
"Asha Ward",
"Jack Lemmon",
"Jerry Clower",
"Jeff B. Davis",
"Kristen Johnston",
"Steve Coogan",
"Shaun Micallef",
"Cherry Chevapravatdumrong",
"Liza Tarbuck",
"Emma Willmann",
"Harvey Guillen",
"Jacksfilms",
"Rob Deering",
"Dustin Diamond",
"Paul Rodriguez (actor)",
"Arden Myrin",
"Nick DiPaolo",
"Dan Soder",
"Andy Zaltzman",
"Jason Reich",
"Nicole Parker",
"Anna Russell",
"Matthew Perry",
"Jake Lacy",
"Bradley Cooper",
"Anna Faris",
"Sam Hyde",
"Harold Ramis",
"Julia Sweeney",
"Melvin Gregg",
"Rick Ducommun",
"Jenna Fischer",
"Gina Yashere",
"Roscoe \"Fatty\" Arbuckle",
"Carrot Top",
"Fred Grandy",
"Cubby Bryant",
"Lily Tomlin",
"Lou Costello",
"Larry Semon",
"J. P. Karliak",
"Jo Caulfield",
"Andrew Santino",
"Garfunkel and Oates",
"Charles Rocket",
"Jayde Adams",
"Paul Dooley",
"Gianmarco Soresi",
"Brooke Dillman",
"Donald Glover",
"Neil Morrissey",
"Catherine Bohart",
"Alec Baldwin",
"Maggie Lawson",
"Harry Secombe",
"Rex Lee (actor)",
"Paul Sand",
"John Moloney (comedian)",
"Jerry Trainor",
"Nathan Fillion",
"Larry Storch",
"Anthony Johnson (actor)",
"Romesh Ranganathan",
"Jane Turner",
"Andrew Dice Clay",
"Jackie Hoffman",
"Steve Byrne",
"Henry Cho",
"Ralph Garman",
"Edward Herrmann",
"Quinta Brunson",
"Waen Shepherd",
"Brad Hall",
"Tom Kennedy (actor)",
"Goldie Hawn",
"Nichole Sakura",
"Shelley Long",
"John Gemberling",
"Vaughn Meader",
"Craig T. Nelson",
"Zooey Deschanel",
"James Burrows",
"Shane Dundas",
"Chauncey Leopardi",
"Sam Levenson",
"Dan Levy (Canadian actor)",
"Aaron Chen",
"James Marsden",
"Dan Povenmire",
"Jack Cutmore-Scott",
"Jessica Holmes (comedian)",
"Studio C",
"Timothy Omundson",
"Colton Dunn",
"Jimmy Pardo",
"Dave Spikey",
"April Winchell",
"Rob Schneider",
"Dr. Demento",
"Alex Horne",
"List of comedy films",
"Otis Harlan",
"Tatá Werneck",
"Foster Brooks",
"Ken Marino",
"David Arquette",
"Kristin Key",
"Ross Marquand",
"Dick Shawn",
"Frank Kelly",
"Barry Sobel",
"Alicia Coppola",
"Sabrina Wu",
"Slim Summerville",
"Malin Akerman",
"Richard Lewis (comedian)",
"Lena Waithe",
"John Aboud",
"Ralph Barbosa",
"Rachel Bloom",
"Greg Fitzsimmons",
"Will Hay",
"Lutz van der Horst",
"Stella (comedy group)",
"Roy Clarke",
"Olga Koch",
"Brad Morris",
"Adam Hartle",
"Dan Mintz",
"Josh Johnson (comedian)",
"Jak Knight",
"Catherine Cohen",
"Mo Gaffney",
"Johnny Hardwick",
"Jay Baruchel",
"Budd Friedman",
"Chevy Chase",
"Glenn Howerton",
"Jim Davidson",
"Jessica McKenna",
"Marx Brothers",
"Barry Cryer",
"Matt King (comedian)",
"Emo Philips",
"Andrew Daly",
"Greg Daniels",
"Tony Gardner",
"Roy Rene",
"John Pankow",
"Janelle James",
"John Simmit",
"Eddie Deezen",
"David Tomlinson",
"Craig Charles",
"Jenna Marbles",
"Terry Sweeney",
"Prashanth Venkataramanujam",
"Mathew Horne",
"Simon Bird",
"Tino Insana",
"Justin Long",
"Nimesh Patel",
"Ritch Shydner",
"Rory Albanese",
"Lion Solser",
"Jim Gaffigan",
"Mitra Jouhari",
"Carmen Lynch",
"Brian Regan (comedian)",
"Fry and Laurie",
"Griffin Newman",
"Keith Waterhouse",
"Lauren Holt",
"David Feldman (comedian)",
"Josh Brener",
"Eric Allan Kramer",
"Shelby Fero",
"Karla Estrada",
"Angela Barnes",
"Allen Covert",
"Chris Gethard",
"Ari Graynor",
"Bonnie Hunt",
"Laurie Metcalf",
"Tim Reid",
"Kevin Sussman",
"Joe Penner",
"Allison Williams (actress)",
"Paul Dinello",
"Soupy Sales",
"Kim Cattrall",
"Andrew Maxwell",
"Vic DiBitetto",
"Albert Brooks",
"Antoine McKay",
"Phoebe Waller-Bridge",
"Ted Lange",
"Dolph Ziggler",
"Jessica Chaffin",
"Richard Herring",
"Vanessa Hollingshead",
"Spencer Kayden",
"Derek Sheen",
"Edward Barbanell",
"Michael Fielding",
"Robin Harris (comedian)",
"Sara Schaefer",
"Robert Townsend (actor)",
"Kim Wayans",
"Kat Dennings",
"Bill Nye",
"Björn Gustafsson",
"Christy Knowings",
"Tommy Tiernan",
"Aaron Karo",
"Bradley Walsh",
"Jon Pertwee",
"Vinny Thomas",
"Tyler James Williams",
"Eugene Mirman",
"Bill Bailey",
"Alex Moffat (comedian)",
"Arnold Stang",
"Kenny Sebastian",
"Dieter Nuhr",
"Joan Sims",
"Lucia Aniello",
"Ruby Wax",
"Josiane Balasko",
"Nancy Lenehan",
"Sierra Katow",
"Nicole Randall Johnson",
"Michael Kessler",
"Eugene Lee Yang",
"Dieter Hildebrandt",
"Ed Hill (comedian)",
"Jayma Mays",
"Ben Savage",
"Gregory Hines",
"French and Saunders",
"Édgar Vivar",
"Johnny Taylor (comedian)",
"Mo'Nique",
"David Jason",
"Marcello Hernández",
"Katherine Ryan",
"Noah Robertson",
"Dennis Wolfberg",
"John Di Domenico",
"Stewart Lee",
"Neil Hamburger",
"Warren Hutcherson",
"Sofia Vergara",
"John Hodgman",
"Andrée Vermeulen",
"Walter Catlett",
"Frances Callier",
"Shane Dawson",
"Joel Murray",
"Jason Manford",
"Catherine Tate",
"Moe Howard",
"Sacha Baron Cohen",
"Christian Finnegan",
"Jack Benny",
"Dana Snyder",
"Eugenia Kuzmina",
"Josh Meyers (actor)",
"Melanie Hutsell",
"Joe Yule",
"Jason Alexander",
"Jaboukie Young-White",
"Angelique Cabral",
"Peter Boyle",
"Charlie Grandy",
"Gerry Dee",
"Lenny Clarke",
"Valerie Harper",
"Joe E. Brown",
"Sydnee Washington",
"Penny Marshall",
"Bobbie Baker",
"Sarah Silverman",
"Maya Erskine",
"Wil Wheaton",
"Shirley Hemphill",
"Jon Dore",
"Noel Fielding",
"Hannah Simone",
"Norm Macdonald",
"Jordan Peele",
"Anthony Padilla",
"Judah Friedlander",
"Cuba Gooding Jr.",
"Graham Linehan",
"Bette Midler",
"Sarah Kuttner",
"Gabe Liedman",
"P. J. Byrne",
"Matt Meese",
"Julia Davis",
"Corey Holcomb",
"Ted Alexandro",
"Omid Djalili",
"List of Australian comedians",
"Jonathan Mangum",
"Hal Cruttenden",
"Adam Buxton",
"Carolyn Lawrence",
"Lyda Roberti",
"Arthur Smith (comedian)",
"Karan Soni",
"Amber Nash",
"Tawny Newsome",
"Samson Kayo",
"Mary Walsh (actress)",
"Mamrie Hart",
"Paul Shaffer",
"Hayley Marie Norman",
"Anke Engelke",
"Alan Yang",
"Tato Bores",
"Nicole Sullivan",
"Joe Torry",
"Ernie Kovacs",
"Alyson Hannigan",
"Keenen Ivory Wayans",
"Maria Canals-Barrera",
"Stephen Schneider (actor)",
"Lew Morton",
"Jorma Taccone",
"Hayes MacArthur",
"Peter Serafinowicz",
"Florinda Meza",
"Allan Sherman",
"Carly Aquilino",
"Martina Hill",
"Lou Wilson (actor)",
"Otto Waalkes",
"Hale and Pace",
"Colin Mochrie",
"Jonathan Kite",
"Max Brooks",
"Gladys Reyes",
"Karl Dall",
"Jessica Williams (actress)",
"Ronnie Barker",
"Heather Graham",
"Zhubin Parang",
"Billy Crawford",
"Steven Michael Quezada",
"Leslie David Baker",
"Bastian Pastewka",
"Joe Gatto (comedian)",
"Lin-Manuel Miranda",
"Jon Glaser",
"Dennis Miller",
"Alison Rich (actress)",
"Kristen Schaal",
"Coldmirror",
"Dom DeLuise",
"Brian Blessed",
"Noël Wells",
"Matt Graham (Scrabble)",
"Tracey Wigfield",
"Sandi Toksvig",
"Barbara Eden",
"Rodger Bumpass",
"Thomas Nelstrop",
"Pigmeat Markham",
"Richard Digance",
"Frangela",
"Jimmy Dunn (comedian)",
"Laird Macintosh",
"Damali Ayo",
"Simon Fanshawe",
"Adam Quesnell",
"Michelle Collins (comedian)",
"Herbert Feuerstein",
"Anne Reid",
"Andy Kindler",
"Lucy Liu",
"Irene Tu",
"Leon Frierson",
"Ian Edwards (comedian)",
"Greg Giraldo",
"Steve Lemme",
"Cobie Smulders",
"Suzanna Kempner",
"Michael J. Nelson",
"Kiri Pritchard Mclean",
"David Pasquesi",
"John Michael Higgins",
"Martin Clunes",
"Jerod Mixon",
"Matt Stone",
"George Burns",
"Jason Mantzoukas",
"Alan Rachins",
"Kurt Fuller",
"Tami Sagher",
"Jim J. Bullock",
"Steve Terreberry",
"Vladimir Caamaño",
"Nancy Carell",
"Chelsea Peretti",
"Daniel Browning Smith",
"Bryan Tucker",
"Nina Conti",
"Kevin Allison",
"Paul C. Vogt",
"Kev Adams",
"Ryan Coleman",
"Kay Cannon",
"Des O'Connor",
"Benito Skinner",
"List of British comedians",
"List of Italian comedians",
"Ilana Glazer",
"Jeff Garlin",
"Chris Evans (presenter)",
"Queen Latifah",
"Lisa Arch",
"The Whitest Kids U' Know",
"Sam Kinison",
"Seann William Scott",
"Peter F. Dailey",
"Nick Offerman",
"Chelcie Lynn",
"Alphonso McAuley",
"Key and Peele",
"Andrew Dismukes",
"Jim Belushi",
"Kreisiraadio",
"Josh Radnor",
"Felicia Day",
"Karen Maruyama",
"Zach Woods",
"Mort Sahl",
"Stanley Unwin (comedian)",
"Ari Shaffir",
"Daniel Kitson",
"Sally Phillips",
"Taylor Tomlinson",
"Bill Young (comedian)",
"Pete Davidson",
"Danitra Vance",
"Brandis Kemp",
"Greg Lee (actor)",
"Hannah Stocking",
"Daniel Sloss",
"Jay Chandrasekhar",
"Ed O'Neill",
"Hape Kerkeling",
"Lang Fisher",
"Ogie Diaz",
"Paula Marshall",
"Freeman Gosden",
"Thomas Middleditch",
"Caroline Rhea",
"Bob and Ray",
"Parvesh Cheena",
"Jessica Hynes",
"Jamie Denbo",
"Keith Malley",
"Ashton Kutcher",
"Jay Jurden",
"Urzila Carlson",
"Esther Povitsky",
"Phyllis Smith",
"Roy Hudd",
"Arthur Mathews (writer)",
"Brian Posehn",
"Steve Martin",
"Rob Huebel",
"Philomaine Nanema",
"Larry Joe Campbell",
"Freddy Lockhart",
"Adrian Grenier",
"Nick Wiger",
"Linda Cardellini",
"Tim Daly",
"Reba McEntire",
"Jim Norton (American comedian)",
"Eric Price",
"Andy Samberg",
"Britt Lower",
"Steve Rossi",
"Michael Longfellow",
"Tim Baltz",
"Joshua Malina",
"Alan Young",
"Dat Phan",
"Bobby Bones",
"Andrea Jin",
"Colin Jost",
"John Swartzwelder",
"Eddie Ifft",
"Craig Anton",
"Frank Gorshin",
"Patty Guggenheim",
"Rose Matafeo",
"Sabrina Impacciatore",
"Joe List",
"Charlie Williams (comedian)",
"Omar Gooding",
"Ben Stiller",
"Peter Grosz",
"Jack E. Leonard",
"Tommy Trinder",
"Brian Unger",
"Will Arnett",
"Hank Chen",
"Jamie Foxx",
"Thomas F. Wilson",
"Antony Jay",
"Buck Henry",
"Jen Kirkman",
"Youngmi Mayer",
"Jerry Sadowitz",
"Sydney Park (actress)",
"Robert Schimmel",
"List of humorists",
"Doug Stanhope",
"Angela Kinsey",
"Kimberly Williams-Paisley",
"Affion Crockett",
"Jon Gabrus",
"Will Smith",
"Tom Rosenthal (actor)",
"Brian Palermo",
"Betsy Brandt",
"Nasir Chinyoti",
"Chic Johnson",
"Ramón Valdés",
"Fred Melamed",
"Thelma Hill",
"Costaki Economopoulos",
"Jordan Klepper",
"Lucy Montgomery (actress)",
"Tom Everett Scott",
"Geoff Stults",
"Maureen Lipman",
"Zach Galifianakis",
"Rip Torn",
"Jessica Kirson",
"Lisa Riley",
"Neal Brennan",
"Adrienne Iapalucci",
"Matthew Baynton",
"Jimmy Ritz (comedian)",
"Jana Schmieding",
"Kyle Dunnigan",
"Jake Flores",
"Sue Perkins",
"Wayne and Shuster",
"Ana Gasteyer",
"Phill Lewis",
"Sammy Shore",
"Jeff Ragsdale",
"Natalie Morales (actress)",
"Mindy Cohn",
"Beth Stelling",
"Doris Roberts",
"Sandra Bernhard",
"Gerburg Jahnke",
"Mike Nichols",
"Fran Drescher",
"Christian Duguay (actor)",
"Whoopi Goldberg",
"Michael Chiklis",
"Caleb Hearon",
"Eric Edelstein",
"Eamonn Holmes",
"Amanullah Khan (comedian)",
"Casey Wilson",
"Edward Everett Horton",
"Laura Prepon",
"Kristen Wiig",
"Jason Sudeikis",
"Amir Blumenfeld",
"Shondrella Avery",
"Lorenzo Music",
"Chris Elliott",
"Karen Kilgariff",
"Jamie Kennedy",
"Tyler Perry",
"Rob Beckett",
"Mo Collins",
"Yvette Nicole Brown",
"Melanie Chandra",
"Joyce DeWitt",
"George Gaynes",
"Josh Widdicombe",
"Lori Tan Chinn",
"H. Jon Benjamin",
"Tony Law",
"Chris Lowell",
"Katherine Helmond",
"Taylor Negron",
"Tom Papa",
"Gabrielle Dennis",
"Wheeler and Woolsey",
"Lauren Lapkus",
"Hugh Davidson (actor)",
"Fern Brady",
"Hervé Villechaize",
"Brett Gelman",
"Cocoa Brown",
"David Frost",
"Ramy Youssef",
"Ingo Appelt (comedian)",
"Andy Dick",
"Lindsay Sloane",
"Sarah Burns",
"Guillermo Rodriguez (comedian)",
"Art Paul Schlosser",
"List of stand-up comedians",
"Sheila MacRae",
"Alice Ghostley",
"Carl Reiner",
"Open Mike Eagle",
"Sandy Duncan",
"Jesus Trejo",
"Will Friedle",
"John Amos",
"Sam Jay",
"Sarah Colonna",
"David Lander",
"Rainn Wilson",
"Humphrey Ker",
"Cameron Esposito",
"Jake Shane",
"Carolyn Hennesy",
"Jon Cryer",
"Lorne Michaels",
"Emilio Rivera",
"Ben Platt",
"Richard Kind",
"Doug E. Doug",
"Blanche Gardin",
"Abbi Jacobson",
"Ellie Taylor",
"Mather Zickel",
"Kyle Newacheck",
"Brett Butler (actress)",
"Mary Holland",
"Max Greenfield",
"Sarah Baker (actress)",
"Gaby Hoffmann",
"Ed Byrne (comedian)",
"Beth Dover",
"Conchata Ferrell",
"Esnyr",
"Kumail Nanjiani",
"Raquel Lee",
"Tom Verica",
"Mark Curry (actor)",
"Bill Engvall",
"Erin Gibson",
"Dan Oster",
"Amy Okuda",
"Brendan Scannell",
"Rich Little",
"Reece Shearsmith",
"Shelley Berman",
"Colleen Ballinger",
"David Sheffield",
"Jeff Hiller",
"Timm Sharp",
"Bill Farmer",
"Demetri Martin",
"Denis Leary",
"Maryedith Burrell",
"Sara Pascoe",
"Alex Edelman",
"Clea DuVall",
"Dennis Day",
"Will Forte",
"Bob Balaban",
"Eliza Coupe",
"Sandeep Parikh",
"Michael Kosta",
"James Acaster",
"Langston Kerman",
"Vice Ganda",
"Whitney Cummings",
"Debbe Dunning",
"Mike White (filmmaker)",
"Guz Khan",
"The Firesign Theatre",
"Ralf Schmitz",
"Julian McCullough",
"Jimmy Brogan",
"Polly Moran",
"Dean Martin",
"Beanie Feldstein",
"Jimmy Tatro",
"Jessica Walter",
"Lucy Beaumont (comedian)",
"Alan Zweibel",
"Lia Marie Johnson",
"Joan Rivers",
"The Kids in the Hall",
"Sean Hayes (actor)",
"Aziz Ansari",
"Joe Pera",
"Travis McElroy",
"Laci Mosley",
"Nick Rutherford",
"Chloe Fineman",
"Bobcat Goldthwait",
"Holly Walker (comedian)",
"Emma Sidi",
"Harry Shearer",
"Jesse Joyce",
"Bowen Yang",
"Beck Bennett",
"Christian Ehring",
"Charles Fleischer",
"Christopher Massey",
"Dan Lauria",
"Justin McElroy",
"Debra Messing",
"Andrew Bowen",
"Jim Jefferies (comedian)",
"Kevin McDonald",
"Brown and Carney",
"Ryan Hamilton (comedian)",
"John Belushi",
"Jean-Claude Pascal",
"Jason Earles",
"Roger Lloyd-Pack",
"Matt Walsh (comedian)",
"Phil Moore (actor)",
"Simon Amstell",
"Paul Stewart (actor)",
"Professor Irwin Corey",
"Joey Forman",
"Penelope Keith",
"Issa Rae",
"Sarah Chalke",
"Chonda Pierce",
"Dave Franco",
"Leslie Liao",
"Phil Wang",
"Greg Poehler",
"Bert Wheeler",
"Rebel Wilson",
"Chris Kelly (writer)",
"Neil Innes",
"Maria Bamford",
"Matthew McConaughey",
"Dylan Marron",
"Harry Anderson",
"Dan Finnerty",
"Aida Rodriguez",
"Steve Guttenberg",
"Simon Nye",
"Rove McManus",
"Lillian Hurst",
"Lauren Miller Rogen",
"Wil Anderson",
"Sharon Horgan",
"Leslie Jones (comedian)",
"Lil' JJ",
"Jacques Tati",
"Charles Hawtrey (actor born 1914)",
"Carter Bays",
"Katie Dippold",
"Paul Iacono",
"Rekha Shankar",
"Adam Hills",
"Annie Murphy",
"Bridget Jones Nelson",
"Rondell Sheridan",
"Aries Spears",
"David Renwick",
"Sonny Bono",
"Carol Burnett",
"David Nobbs",
"Ivan Reitman",
"Jane Leeves",
"Anthony King (writer)",
"Nathan Lane",
"Ginger Gonzaga",
"Hugh Dennis",
"Steve Rizzo",
"Terry Gilliam",
"John Prats",
"Michael Fenton Stevens",
"Rowland Rivron",
"Aasif Mandvi",
"Russell Gilbert",
"Scott Adsit",
"David Dineen-Porter",
"James Austin Johnson",
"Tamsin Greig",
"Paul Brittain",
"Loyiso Gola",
"John Valby",
"Edgar Bergen",
"Sara Rue",
"Russell Howard",
"Allana Harkin",
"Ken Dodd",
"Sarah Cooper",
"Desi Lydic",
"Clea Lewis",
"Paolo Ballesteros",
"Ike Barinholtz",
"Brent Spiner",
"Bonnie Franklin",
"Noah Reid",
"Yeardley Smith",
"Toby Turner",
"Tim Hawkins",
"Jack Riley (actor)",
"Karen Chee",
"Lisa Gilroy",
"Josh Server",
"Masashi Tashiro",
"Taika Waititi",
"Hella von Sinnen",
"Dana Gould",
"Brian Haley",
"Ruth Draper",
"Allan K.",
"Chris Williams (actor)",
"Ashley Bell (actress)",
"D. L. Hughley",
"Conner O'Malley",
"Kristin Davis",
"Pokwang",
"Karl Pilkington",
"Kevin Meaney",
"Tanyalee Davis",
"Andy Richter",
"Akilah Hughes",
"Robert Smigel",
"Sarah Millican",
"Kyle Gass",
"Michael Patrick King",
"Jill Whelan",
"Rick Mercer",
"Malcolm-Jamal Warner",
"Paul McDermott",
"Jay R. Ferguson",
"Rich Sommer",
"Tommy Cooper",
"Gillian Jacobs",
"Raphael Bob-Waksberg",
"Mindy Kaling",
"Emily Atack",
"Ford Kiernan",
"Tymberlee Hill",
"Pat Shortt",
"Rosie Tran",
"Alex Reymundo",
"Danny Woodburn",
"Andy Milonakis",
"Chad Daniels",
"Danny Wallace (humorist)",
"Richard Jeni",
"Lisa Eckhart",
"Lauren Pritchard (actress)",
"Kevin Brennan (comedian)",
"Josh Fadem",
"Paola Cortellesi",
"Sean Maguire",
"Jonah Ray",
"Radhika Vaz",
"Swami X",
"Jim Backus",
"Paul Goebel (television personality)",
"Robert Kelly (comedian)",
"Jay Leggett",
"Brenda Withers",
"Joross Gamboa",
"David Dobrik",
"John Heffron",
"Arturo Castro (Guatemalan actor)",
"Martin Schneider",
"Pete Correale",
"Ellie Kemper",
"Neil Delamere",
"Miles Fisher",
"Anna Camp",
"Samba Schutte",
"Jonathan Winters",
"Karyn Parsons",
"Michael McDonald (comedian)",
"Leah Lamarr",
"Dick Gregory",
"Christopher Masterson",
"Patty Duke",
"Matt Mira",
"Zack Pearlman",
"Veronika Slowikowska",
"Lucien \"Saluche\" Small",
"Dan Ahdoot",
"Ray Peacock",
"Carol Leifer",
"Michaela Watkins",
"Ken Jeong",
"Elis James",
"List of United States stand-up comedians",
"Kerry Talmage",
"Bob Zany",
"Richard Gautier",
"Jason Bateman",
"Aidy Bryant",
"Eric Drysdale",
"Sherman Hemsley",
"Millicent Martin",
"Sid Caesar",
"Phoebe Robinson",
"Hal Sparks",
"Gina DiVittorio",
"Wayne Federman",
"Laurie Elliot",
"David Walliams",
"Michael Moore",
"Glenn Rockowitz",
"Marlon Wayans",
"John Ritter",
"Graham Chapman",
"Stephanie Courtney",
"Keyla Monterroso Mejia",
"Roy Castle",
"The Lonely Island",
"Jordan Black (actor)",
"Miranda Hart",
"Cristina Pucelli",
"Sue Costello",
"Melanie Chartoff",
"Diedrich Bader",
"Clark Duke",
"Joseph Gordon-Levitt",
"Olaf Schubert",
"Tom Davis (actor)",
"Luciana Littizzetto",
"Paul Shane",
"Alia Janine",
"Sunita Mani",
"Martin Starr",
"James Murray (comedian)",
"Joe Bob Briggs",
"Johnny Lever",
"Teller (magician)",
"Paolo Contis",
"Anita Barone",
"Luke Kempner",
"Tim Vine",
"Ellie White",
"Alan Brough",
"Ron Pardo",
"Pete Gardner",
"Laurence Clark (comedian)",
"Dov Davidoff",
"Jake Fogelnest",
"Stan Laurel",
"Brian Stack (comedian)",
"Daniele Gaither",
"Andrés López Forero",
"Debra Jo Rupp",
"J.J. Philbin",
"Jorge Porcel",
"Amy Pietz",
"Harold Lloyd",
"Charlotte Rae",
"Mark McKinney",
"Steve Monroe",
"Chesney and Wolfe",
"Jorge Garcia",
"Tim Minchin",
"Mike O'Brien (actor)",
"Chris O'Dowd",
"Max Miller (comedian)",
"Lucky Yates",
"Colin Murphy (comedian)",
"Cristin Milioti",
"Freddie Prinze Jr.",
"Joey Bragg",
"Cassandra Peterson",
"Mark Addy",
"Anson Williams",
"Tony Hancock",
"The League of Gentlemen",
"Nat Faxon",
"C.S. Lee",
"Charles Mack (blackface performer)",
"Gaby Köster",
"Sheng Wang",
"List of Canadian comedians",
"Craig Cash",
"Josh Gondelman",
"Elaine May",
"Donna Douglas",
"Nephew Tommy",
"Maulik Pancholy",
"Andy Juett",
"George Wendt",
"Edu Manzano",
"Dewayne Perkins",
"Colin Hanks",
"Greg Behrendt",
"Stephen Lynch (musician)",
"Annabelle Gurwitch",
"April Macie",
"Mike Mitchell (actor)",
"Charles Nelson Reilly",
"Nipsey Russell",
"Stuttering John Melendez",
"Lonny Ross",
"Paul Eddington",
"Liz Cackowski",
"Bil Dwyer",
"Regan Burns",
"Jennifer Coolidge",
"Rob McElhenney",
"David Zed",
"Nostalgia Critic",
"Carl Hurley",
"Thomas Hermanns",
"Alanna Ubach",
"Lil Rel Howery",
"Nick Mohammed",
"Dulcé Sloan",
"Alec Berg",
"Clancy Brown",
"Brian Hooks",
"Bill Lawrence (TV producer)",
"Lilan Bowden",
"Dustin Demri-Burns",
"Charo",
"Julio Torres",
"Carl Barron",
"Kevin Gillese",
"Josh Sharp",
"Fred Savage",
"Ian La Frenais",
"Willie Revillame",
"Joe Piscopo",
"Hugo Egon Balder",
"Christina Applegate",
"Richard Murdoch",
"Matthew Broderick",
"Antony Cotton",
"Gale Storm",
"Al Read",
"Baron Vaughn",
"Mike Ward (comedian)",
"Horatio Sanz",
"Jon Hurwitz",
"Johnny Vaughan",
"Bo Burnham",
"Chris Hogan (actor)",
"Brandon Scott Jones",
"Frank Skinner",
"Buddy Hackett",
"Dominic Holland",
"Susie Garrett",
"Ego Nwodim",
"Gabriel Iglesias",
"Andrew Phung",
"Gillian Vigman",
"Anthony Clark (actor)",
"Janine Brito",
"Henry Normal",
"Bernard Manning",
"Scott Baio",
"Aubrey Plaza",
"Rita Rudner",
"Tito Sotto",
"Paul Kaye",
"W. S. Gilbert",
"Leonard Robinson",
"Rowan Atkinson",
"Vince Barnett",
"Ronnie Corbett",
"Owen Benjamin",
"Shaun Majumder",
"Elayne Boosler",
"Paul Garner",
"Anthony Atamanuik",
"VanossGaming",
"Seth Meyers",
"Dave Gorman",
"Kevin Eldon",
"Cheryl Hines",
"Ian Harvie",
"Faizon Love",
"Bill Burr",
"Ally Maki",
"Katherine Parkinson",
"Joel Hodgson",
"Lindy West",
"Jermaine Fowler",
"Ken Shimura",
"Godfrey (comedian)",
"Mario Cantone",
"Andy Griffith",
"Elizabeth Banks",
"Blake Harrison",
"Streeter Seidell",
"Rob Little",
"Jimmy Fallon",
"Michael Rosenbaum",
"Rebecca Corry",
"Angus Sampson",
"Sam Richardson (actor)",
"Doug Chappel",
"Briga Heelan",
"Kurtwood Smith",
"Martin Lawrence",
"Dawn French",
"John Hughes (filmmaker)",
"James Anderson (American writer)",
"Carrie Brownstein",
"John Bishop",
"Megan Stalter",
"Patton Oswalt",
"Claudia O'Doherty",
"Richard Cheese",
"The Valleyfolk",
"Brian Wilde",
"Amanda Barrie",
"Tom Davis (comedian)",
"Janno Gibbs",
"Rachel Chagall",
"Colin Quinn",
"Kenya Barris",
"John Kassir",
"Buddy Ebsen",
"Ade Edmondson",
"Sheryl Lee Ralph",
"Irene Ryan",
"Alan Ruck",
"Brandon Hardesty",
"Rhea Seehorn",
"Don Hornsby",
"Diane Keaton",
"David Batra",
"Andrew Orvedahl",
"Stephen Root",
"Brandon Wardell (comedian)",
"Vance DeGeneres",
"Steve Landesberg",
"A.D. Miles",
"Rusty Warren",
"Ron Palillo",
"Jackie Fabulous",
"Shia LaBeouf",
"Jimmy Dore",
"Carlos Balá",
"Homer and Jethro",
"Natalie Haynes",
"Rebecca Drysdale",
"Allison Janney",
"Zach Cregger",
"Bill Bellamy",
"Michael Ian Black",
"Richard Briers",
"Erik Griffin",
"Brian Thomas Smith",
"Melissa Peterman",
"Marilyn Suzanne Miller",
"Kaitlin Olson",
"Melissa McCarthy",
"Bruno Kirby",
"Danny Masterson",
"Mirja Boes",
"Victoria Jackson",
"Katherine Lynch",
"Alison Brie",
"List of The Howard Stern Show staff",
"Guy Pratt",
"Craig Bierko",
"Jonathan Goldstein (filmmaker)",
"Ron Livingston",
"Leonardo Nam",
"Jeff Richards (comedian)",
"Christoph Waltz",
"Jennifer Saunders",
"Eddie Pepitone",
"David Alan Grier",
"Maren Kroymann",
"Brennan Lee Mulligan",
"Ryan Hansen",
"Jerry Minor",
"Mel Blanc",
"Lenny Bruce",
"Marty Allen",
"Greg Thomey",
"Mark Gatiss",
"Myq Kaplan",
"Timothy Simons",
"Dan Cummins",
"Morey Amsterdam",
"John Fugelsang",
"Eric Idle",
"Bill Maher",
"Leo Allen",
"Jon Rudnitsky",
"Judy Toll",
"James Gregory (comedian)",
"Heléne Yorke",
"Bruce Campbell",
"Kevin Dillon",
"Justine Ezarick",
"Nick Helm",
"Delta Burke",
"Thora Hird",
"Hal Linden",
"Howard Kremer",
"Jim Tavaré",
"Steve Pemberton",
"Frank Randle",
"Jonathan Krisel",
"Awra Briguela",
"John Stamos",
"Mitchell and Webb",
"Tammy Pescatelli",
"The Umbilical Brothers",
"Moses Storm",
"Yassir Lester",
"Harry Trevaldwyn",
"Thomas Sadoski",
"Lolly Adefope",
"Jeanne Robertson",
"Jennifer Veal",
"Andreas Rebers",
"Shawn Wayans",
"List of German comedians",
"Giovanni Ribisi",
"Lizzy Caplan",
"Katie Halper",
"Brett Goldstein",
"Dave Thomas (actor)",
"Mark Herras",
"Stephen Mangan",
"J.P. Manoux",
"Rick Reynolds",
"Deborah Rush",
"John Lithgow",
"Estelle Getty",
"John Bluthal",
"Barry Humphries",
"Rip Taylor",
"Jason Jones (actor)",
"Jesse Heiman",
"Bill Owen (actor)",
"Jeffrey Tambor",
"Georgia Engel",
"Vitaly Zdorovetskiy",
"Peter Aykroyd",
"Charlie Drake",
"Kate Micucci",
"Ted Ray (comedian)",
"Jimmie Walker",
"Pat Cooper",
"Ian Karmel",
"Joe Lipari",
"Jonathan Slavin",
"James Dreyfus",
"Jim David",
"Cindy Williams",
"Akshay Kumar",
"Shane Richie",
"Ozzie Nelson",
"Arthur Simeon",
"Drew Droege",
"JoAnna Garcia Swisher",
"LaWanda Page",
"Roz Ryan",
"Rachael MacFarlane",
"Ellen DeGeneres",
"Kimrie Lewis",
"Peter Tinniswood",
"David So",
"Rick Overton",
"Pat Condell",
"Ronny Chieng",
"Danny Cooksey",
"Esther Ku",
"Blonde Brewer",
"Autumn Chiklis",
"Jamie Farr",
"Clarice Taylor",
"Mae Whitman",
"Mark Russell",
"Tom Kenny",
"Michelle Hurd",
"Charles Esten",
"Toni Gonzaga",
"June Diane Raphael",
"Spike Milligan",
"Chris Farley",
"Uğur Rıfat Karlova",
"Ayden Mayeri",
"Chris Rush",
"Robert Q. Lewis",
"Camille Cottin",
"Dick Martin (comedian)",
"Travon Free",
"Trevor Moore (comedian)",
"Amanda Seales",
"Karla Souza",
"Ken Howard",
"Saturday Night Live",
"The Mighty Boosh",
"Lee Mack",
"Cash Levy",
"Barunka O'Shaughnessy",
"Mack Sennett",
"Kevin Spacey",
"Adam Cayton-Holland",
"humour",
"TomSka",
"Derek Edwards",
"Miranda Richardson",
"Aristotle Athari",
"Cedric Yarbrough",
"Kapil Sharma (comedian)",
"Vic Reeves",
"Red Buttons",
"Stewart Francis",
"Charles Hawtrey (stage actor)",
"Ricky Gervais",
"Helen Hong",
"Conrad Bain",
"Vivian Stanshall",
"Eddie Kaye Thomas",
"Rick Dees",
"Jack Paar",
"Baratunde Thurston",
"Deon Cole",
"Betty White",
"Dane Cook",
"Bryan Greenberg",
"Pauline McLynn",
"Mikey Day",
"Tom Flanigan (writer)",
"John Mahoney",
"Ali Siddiq",
"Characters of Henry Danger and Danger Force",
"Nick Frost",
"Garry Marshall",
"Kathryn Fiore",
"Parker Posey",
"Ismo Leikola",
"Mike Krüger",
"Liz Torres",
"Tim Heidecker",
"Ted Knight",
"Alexei Sayle",
"Sunny Mabrey",
"Fakkah Fuzz",
"Danny Kaye",
"Jensen Karp",
"Melissa Rauch",
"Bobby Mair",
"Bert Newton",
"Dante Powell (comedian)",
"Ashley Williams (actress)",
"Ty Barnett",
"Kelly Pryce",
"James Buckley (actor)",
"Matty Cardarople",
"Hannah Hart",
"Michael Colton",
"Bill Fagerbakke",
"Frankie Boyle",
"Armstrong and Miller",
"Joel Dommett",
"Hazel Brugger",
"Milana Vayntrub",
"Cheech and Chong",
"Jami Gong",
"Dave Losso",
"John Mulaney",
"Harold Ritz",
"John Morgan (comedian)",
"Morecambe and Wise",
"Diona Reasonover",
"Adam F. Goldberg",
"Jane Lynch",
"Dulé Hill",
"Mike MacRae",
"Ian Lithgow",
"George Formby Sr.",
"Mark Normand",
"Jonathan Kimmel",
"Ryan Stiles",
"Leo Reich",
"Niecy Nash",
"Rowan and Martin",
"Max Wall",
"Roger Kitter",
"Ron White",
"Judy Cornwell",
"Matt LeBlanc",
"Jerry Ferrara",
"Mario Lopez",
"Kate Berlant",
"Lindsey Kraft",
"Keith Ferguson (voice actor)",
"Jenny Zigrino",
"Robby Hoffman",
"Maribeth Monroe",
"List of Japanese comedians",
"George Moran (comedian)",
"Steve-O",
"Aisha Tyler",
"Patsy Rowlands",
"Steven Boyer",
"Whitmer Thomas",
"Pete Holmes",
"Zoe Jarman",
"Kyle Cease",
"Adhir Kalyan",
"Nogla",
"Robert Woolsey",
"Kurtis Conner",
"Brendon Walsh",
"Paget Brewster",
"Jasper Redd",
"Jessimae Peluso",
"Kevin Smith",
"Armando Iannucci",
"Danny Wells",
"Andrew Leeds (actor)",
"Luka Jones",
"Pat Carroll",
"David Herman",
"Maddie Taylor",
"Earl Okin",
"Brendan Schaub",
"Melai Cantiveros",
"Craig Robinson (actor)",
"Carol Channing",
"Laura Solon",
"Marie Dressler",
"Amber Preston",
"Steve Higgins",
"Lauren Potter",
"Nick Thune",
"Russell Kane",
"Lucy Davis",
"Sohail Ahmed",
"Dougie Baldwin",
"Nick Jameson",
"Jaleel White",
"Brother Dave Gardner",
"Angelique Bates",
"Kelen Coleman",
"Victor Williams",
"Byron Bowers",
"Crista Flanagan",
"Rebecca Front",
"Dana Powell",
"Jeremy Hotz",
"DeAnne Smith",
"Paul Lieberstein",
"Omar Chaparro",
"Paul Feig",
"Judy Holliday",
"Dom Irrera",
"Phil LaMarr",
"Crystal Bernard",
"Paul Chowdhry",
"Ben Crompton",
"Kathleen Rose Perkins",
"Kathy Burke",
"Chris Diamantopoulos",
"Adam Scott (actor)",
"Lano and Woodley",
"David Alan Basche",
"David Beck",
"April Richardson",
"PewDiePie",
"Mary Louise Wilson",
"Anne Meara",
"The Tenderloins",
"Gummo Marx",
"Tommy Pope",
"Les Charlots",
"Carole Cook",
"Vic Sotto",
"Eugene Cordero",
"Molly Shannon",
"Vinesauce",
"Kevin Farley",
"Emily Heller",
"Stephanie Koenig",
"Jane Wickline",
"Katy Mixon",
"Blaire Erskine",
"Tom Gianas",
"Josh Gad",
"Kevin Heffernan (actor)",
"Raymond Ablack",
"Pamela Fryman",
"Eva Victor",
"Don Ameche",
"Rory Scovel",
"Paul Petersen",
"Javed Jaffrey",
"Lewis Black",
"Tony Hale",
"Josh Blue",
"Magda Szubanski",
"Amelia Dimoldenberg",
"Jennie McAlpine",
"Kountry Wayne",
"Mark-Paul Gosselaar",
"Larry Brantley",
"Spike Feresten",
"Robert Klein",
"Ayelet the Kosher Komic",
"Jesse Tyler Ferguson",
"Jack Handey",
"Lavell Crawford",
"Tracy Morgan",
"God's Pottery",
"Peter Bonerz",
"Stanley Holloway",
"Joe Besser",
"Carroll O'Connor",
"Oscar Nunez",
"William Shatner",
"Bill Hicks",
"Gabe Dunn",
"Rex Navarette",
"Steve Carell",
"Paul Sun-Hyung Lee",
"Michael McKean",
"Brandon Micheal Hall",
"Helga Feddersen",
"Al Molinaro",
"Larry Wilmore",
"Jeff Dye",
"Adrian Martinez (actor)",
"Jerry Stiller",
"Marilu Henner",
"David Hornsby",
"Tony Slattery",
"Alice Wetterlund",
"Jack Haley",
"comedian",
"Taryn Manning",
"Kyla Pratt",
"Ernest Borgnine",
"Jeremy Piven",
"Matt Rogers (comedian)",
"Jack Whitehall",
"Richard Haydn",
"Kulap Vilaysack",
"Milton Berle",
"Neil Casey",
"Evelyn Hamann",
"Howard Morton",
"Simon Pegg",
"Mickey Rooney",
"Tate Donovan",
"Michael Showalter",
"Seth Herzog",
"Howard Hesseman",
"Miles Teller",
"Carly Craig",
"Joe Alaskey",
"Georgia King",
"Diane Morgan",
"Celia Imrie",
"Martin Mull",
"Breckin Meyer",
"Jeff Stilson",
"Arleen Sorkin",
"Zoë Coombs Marr",
"Kat Radley",
"Steve Hofstetter",
"Teacher Mpamire",
"Kaya Yanar",
"Roisin Conaty",
"Lenny Henry",
"Jessica St. Clair",
"Mystro Clark",
"Rachel Ramras",
"Penn Jillette",
"Dieter Hallervorden",
"Matt Oberg",
"Fred Wolf (writer)",
"John Cusack",
"Damien Fahey",
"Neil Campbell (producer)",
"Jenny Hagel",
"Teri Garr",
"James Urbaniak",
"John Lapus",
"Luba Goy",
"Jackie Vernon (comedian)",
"Rodney Dangerfield",
"Kevin Pereira",
"Rick Moranis",
"Jim Dale",
"Danny Bhoy",
"Zach Cherry",
"Theo Von",
"Maya Rudolph",
"Peter Paul Bergman",
"Scott Innes",
"Jhong Hilario",
"John Branyan",
"X Mayo",
"Matt Rife",
"Reginald D. Hunter",
"Stephen Grant (comedian)",
"Erinn Hayes",
"Patricia Marx",
"Hamish Blake",
"Bob Marley (comedian)",
"Kali Hawk",
"Bernie Mac",
"Baba Ali",
"Seth Morris",
"Brittany Broski",
"Adam Conover",
"Jaime King",
"Rob Paulsen",
"Harland Williams",
"Beth Littleford",
"Elliot Page",
"Sinbad (entertainer)",
"Sasheer Zamata",
"Nancy Cartwright",
"Judy Gold",
"Linda Robson",
"Tom Green",
"Julie Walters",
"Minnie Pearl",
"Stephen Chow",
"Frank Caliendo",
"Joey Diaz",
"Jackie Martling",
"Duane Martin",
"Kate Walsh (actress)",
"Bruce McCulloch",
"Chris Ramsey (comedian)",
"Shari Lewis",
"Jackass (franchise)",
"Edgar Kennedy",
"Zak Orth",
"Joanna Lumley",
"Jessy Hodges",
"Tom Arnold (actor)",
"Duncan Trussell",
"Sindhu Vee",
"Emma Chambers",
"Theodore Gottlieb",
"Jason Nash",
"Kristine Levine",
"Esmonde and Larbey",
"Shane Mauss",
"Punkie Johnson",
"Melanie Lynskey",
"Robert Wuhl",
"Julie Bowen",
"Artie Lange",
"Larry David",
"Dan Rowan",
"Jay Johnston",
"Candy Palmater",
"Howard Read",
"Danny DeVito",
"Toby Huss",
"Dave Williamson",
"Brad Sherwood",
"Maria Blasucci",
"Katie Rich",
"The Grumbleweeds",
"Chingo Bling",
"Rosanne Katon",
"Gary Coleman",
"John Aprea",
"The Ritz Brothers",
"Dan McCoy",
"Anne Beatts",
"Jenni Konner",
"Ted McGinley",
"Jackie Chan",
"Ricky Velez",
"Matt McCarthy (comedian)",
"Fannie Flagg",
"Moms Mabley",
"Paco Erhard",
"Michael Strahan",
"Mikey Bustos",
"Andrew Goldberg (writer)",
"Erica Rhodes",
"Ann B. Davis",
"Keith David",
"Ed Gamble",
"Sam Seder",
"Anabel Alonso",
"Brian Huskey",
"Roberto Gómez Bolaños",
"Dudley Moore",
"Jon Pointing",
"Reggie Watts",
"Owen Wilson",
"Mary Tyler Moore",
"Monty Python",
"Charlotte McDonnell",
"Michelle Thomas",
"Joel Kim Booster",
"Colleen Camp",
"Mimi Kennedy",
"Greta Titelman",
"Yannis Pappas",
"Nicholas Stoller",
"jacksepticeye",
"John Oliver (entertainer)",
"Ken Goodwin (comedian)",
"Aaron Aryanpur",
"Blaine Capatch",
"Dan Levy (American comedian)",
"Todd Holoubek",
"Jan Kraus (actor)",
"Rob Stefaniuk",
"Steve Sweeney (comedian)",
"Richard Rankin",
"Ben Schwartz",
"Andy de la Tour",
"Artemis Pebdani",
"Christopher Titus",
"Ice Cube",
"Louis Nye",
"Mike Harding",
"Jessica Knappett",
"Brody Stevens",
"Darien Sills-Evans",
"Robert Baril",
"Hannah Gadsby",
"Zoë Tomalin",
"Mary Birdsong",
"Bobby Collins (comedian)",
"Alex Anfanger",
"Kyle Mooney",
"Lucas Neff",
"Ahir Shah",
"Carlos Alazraqui",
"Melissa Joan Hart",
"Phill Jupitus",
"Harvey Korman",
"Kasha Patel",
"Punt and Dennis",
"Empoy Marquez",
"Christopher Mintz-Plasse",
"Rubén Aguirre",
"Cynthia Szigeti",
"Caitlin Reilly",
"George Segal",
"Ian Hecox",
"David Anthony Higgins",
"Flula Borg",
"Angela Trimbur",
"Sam Morril",
"Gracie Allen",
"Stephen Merchant",
"Danielle Pinnock",
"Alison Gates",
"Jeffrey Ross",
"The Three Stooges",
"Doug Benson",
"Sean Hughes (comedian)",
"Philip Proctor",
"Fred Willard",
"Desi Arnaz",
"Billy T. James",
"Daniel von Bargen",
"Harry Enfield",
"A. Whitney Brown",
"Frank Caeti",
"Jim Carrey",
"Ross Mathews",
"Dan Aykroyd",
"Tim Harmston",
"Richard Lane (actor)",
"Jiaoying Summers",
"Mark Dolan",
"Danielle Perez (comic)",
"Sean O'Connor (comedian/writer)",
"Kenneth Horne",
"Cordula Stratmann",
"John Bunny",
"Olli Dittrich",
"Jo Brand",
"Ron Funches",
"Reginald Ballard",
"Curly Howard",
"Dave Chappelle",
"Kirstie Alley",
"Bebe Neuwirth",
"Pardis Parker",
"Wilmer Valderrama",
"Josie Long",
"John Lutz",
"Jimmy Tarbuck",
"Angela Means",
"Joe Flaherty",
"Preacher Lawson",
"Wendy Maybury",
"Michaela Coel",
"James Patrick Stuart",
"Andy Cohen",
"Bud Cort",
"Ryan Gaul",
"Ewen Gilmour",
"Audrey Meadows",
"Ardal O'Hanlon",
"Tony Randall",
"Lisa Lampanelli",
"Paul W. Downs",
"Kayvan Novak",
"Phil Lord and Christopher Miller",
"The Kid Mero",
"Ben Willbond",
"Ant (comedian)",
"Elizabeth Hurley",
"Frank Muir",
"Kurt Krömer",
"Peter Helliar",
"Rachael Harris",
"Norm Crosby",
"Rik Mayall",
"Herb Sargent",
"Marla Gibbs",
"Barry Took",
"Andy Clyde",
"Steven Weber",
"Jeffery Self",
"Jamie Loftus",
"Felipe Neto",
"Dave Allen (comedian)",
"Kathie Lee Gifford",
"Dave Merheje",
"Charlie Chaplin",
"Tim Meadows",
"Chris Spencer (actor)",
"Drew Carey",
"Bobby Slayton",
"Damon Wayans",
"Lucille Ball",
"Mike Lawrence (comedian)",
"Kathy Griffin",
"Beverly Sanders",
"Daniel Tosh",
"Bob Elliott (comedian)",
"Beetlejuice (entertainer)",
"Jud Strunk",
"Matt Braunger",
"Wally Cox",
"Atze Schröder",
"Jeremy Dyson",
"Morwenna Banks",
"Peter Cook",
"Patti Harrison",
"Jim Rash",
"Michael Rapaport",
"Joan Cusack",
"Sandy Baron",
"Patrick Bristow",
"George Gobel",
"List of Dutch comedians",
"Rick Younger",
"Rachel Parris",
"Alan Thicke",
"Art Carney",
"Tony Danza",
"Ai-Ai delas Alas",
"Josh Duhamel",
"John Dowie (humourist)",
"Silvia Abril",
"Des McLean (comedian)",
"Patsy Kelly",
"David Mitchell (comedian)",
"Ben Miller",
"Nate Mooney",
"Javier Portales",
"Todd Grinnell",
"Robbie Amell",
"Dave Attell",
"John Farley (actor)",
"Peter Kelamis",
"Diablo Cody",
"Jon Favreau",
"The Comic Strip",
"Thomas Spitzer (author)",
"Craig Campbell (comedian)",
"Charlyne Yi",
"Alex Zane",
"Allison Raskin",
"Chris Kattan",
"Smosh",
"Del Close",
"Gary Janetti",
"Alton Brown",
"Chelsea Handler",
"Mark Wahlberg",
"Robbie Coltrane",
"Aparna Nancherla",
"Joe Lo Truglio",
"Chris Rock",
"Caroline Aherne",
"Katt Williams",
"Chuck Sklar",
"Gabrielle Union",
"Kristina Wong",
"Hari Kondabolu",
"Ali Wentworth",
"Steve Zahn",
"Jürgen Becker (comedian)",
"Diether Krebs",
"Natasha Leggero",
"Michael V.",
"Mary Jo Catlett",
"Nigel Planer",
"List of Finnish comedians",
"Jordan Carlos",
"Kimmy Gatewood",
"Kevin Pollak",
"DeRay Davis",
"Steve O'Donnell (writer)",
"Les Dawson",
"Neil Patrick Harris",
"Victor Moore",
"Skylar Astin",
"The Chaser",
"Danny Thomas",
"Jay Leno",
"Adam McKay",
"Dante (comedian)",
"C. C. Swiney",
"Candice Bergen",
"Hana Mae Lee",
"Ed Wynn",
"Vir Das",
"Fred Armisen",
"\"Weird Al\" Yankovic",
"Glenn Wool",
"Celeste Yim",
"Tim Conway",
"Sally Field",
"List of deadpan comedians",
"Zarna Garg",
"Barry Rothbart",
"Danny Tamberelli",
"The Frat Pack",
"Zoë Chao",
"Roseanne Barr",
"Kevin Brown (actor)",
"Jimmy Wong",
"Jeff Bennett",
"Sal Iacono",
"Michael Gross (actor)",
"Rhys Darby",
"Mike Yard",
"Steve Allen",
"Michael Koman",
"Amy Landecker",
"Charlie Manna",
"Jon Kenny",
"Olivia Munn",
"Justin Edwards (actor)",
"Malcolm Hardee",
"Jo Koy",
"Edgar Wright",
"Jack DeSena",
"Harriet Dyer",
"Kyle Kinane",
"Lisa Ann Walter",
"Richard Steven Horvitz",
"Tim Thomerson",
"Steve Hughes",
"Liz Meriwether",
"Aya Cash",
"Sommore",
"Hamish and Andy",
"Emily Tarver",
"Justin Bartha",
"Deryck Guyler",
"Jonathan Ross",
"Wendie Malick",
"Robin Thede",
"Dermot Morgan",
"Nancy Travis",
"Tony Sam",
"Adam Carolla",
"Randy Feltface",
"Leslie Mann",
"Max Baer Jr.",
"Mike O'Malley",
"Nish Kumar",
"Don Lake",
"Bill Hunter (actor)",
"Nora Tschirner",
"Bruce Mahler",
"Martha Kelly",
"Terry Crews",
"Valente Rodriguez",
"Robin Tran",
"Jim Nabors",
"Brendon Small",
"Carlos Mencia",
"Tom Scharpling",
"Ira Glass",
"Harriet Kemsley",
"Severn Darden",
"Stephanie Allynne",
"Carl Tart",
"Hannan Azlan",
"Jacqueline Novak",
"Mary Elizabeth Ellis",
"Garrison Keillor",
"Bob Einstein",
"James Lesure",
"Martin Freeman",
"Lesley Joseph",
"Eric Lloyd",
"Nicolas Cantu",
"Wil Shriner",
"Jo Firestone",
"Dominic Dierkes",
"Lee Newton",
"Leon Errol",
"Demi Adejuyigbe",
"Corinne Grant",
"Jeff Green (comedian)",
"Wallace Shawn",
"Joe DeRita",
"Fabiana Karla",
"Laura Silverman",
"Gus Schilling",
"Cal Wilson",
"Chloe Troast",
"Mark Proksch",
"Tom Price (actor)",
"Hampton Yount",
"Martin Sargent",
"George Leonard Wallace",
"Taylor Williamson",
"Julian Clary",
"Tony Hawks",
"Annie Lederman",
"Franklyn Ajaye",
"Neil Mullarkey",
"Sean Astin",
"Matt Besser",
"Will Ferrell",
"Thelma Todd",
"Joe Cornish",
"Rachel Feinstein (comedian)",
"Michael Cera",
"Paula Jai Parker",
"Willie Rushton",
"Graham Norton",
"Kyle Massey",
"Lauren Weedman",
"Les Dennis",
"Slink Johnson",
"Fortune Feimster",
"Don Novello",
"Charlie McDowell",
"Nia Vardalos",
"Art Metrano",
"Dave Sirus",
"Nicole Byer",
"Jimmi Simpson",
"GloZell",
"Patrick Brammall",
"John Ross Bowie",
"Freddie Frinton",
"Anders Holm",
"Jose Manalo",
"Michael Palin",
"David DeLuise",
"Akaash Singh",
"Ant & Dec",
"Don Ferguson (actor)",
"Chelsea Holmes (actor)",
"D'Arcy Carden",
"Jessica Chobot",
"Steve Little (actor)",
"Jordan Firstman",
"Stephen Fry",
"Wayne Knight",
"Heidi Gardner",
"Kelsey Grammer",
"Benjamin Walker (actor)",
"Dana Carvey",
"Kathleen Madigan",
"Kevin Connolly (actor)",
"Seth Green",
"Judith Light",
"Sean Lock",
"Parker Young",
"The Comedy Store Players",
"Bret Harrison",
"Bridget Everett",
"Bill Hader",
"Chris Geere",
"Brendan Hunt",
"Trey Kennedy",
"Marc Maron",
"Brian Miner",
"B. J. Novak",
"Perry Caravello",
"Brian Quinn (comedian)",
"Geoffrey Arend",
"Moshe Kasher",
"Mo Alexander",
"Conan O'Brien",
"Karlous Miller",
"List of Portuguese comedians",
"Meaghan Rath",
"Paul Scheer",
"Skip Stephenson",
"Michael Roof",
"Brent Morin",
"George Wallace (American comedian)",
"Henry Phillips (comedian)",
"Kristin Chenoweth",
"Reno Wilson",
"Eric Morecambe",
"Cody Ko",
"Ray Combs",
"Anh Do",
"Tommy Ryman",
"Sabrina Sato",
"José Sánchez Mota",
"Franklin Pangborn",
"Utkarsh Ambudkar",
"Valerie Azlynn",
"Joanne McNally",
"George Dunn (actor)",
"Anthony Jeselnik",
"Freddie Prinze",
"Joe Rogan",
"Benny Hill",
"Steve Punt",
"Jonathan Coulton",
"James L. Brooks",
"Sugar Sammy",
"Cliff Nazarro",
"Wendy Liebman",
"Brian Conley",
"Eugenio Derbez",
"Ben Gleib",
"Richard Gadd",
"Don Knotts",
"Jim Sweeney (comedian)",
"Ikechukwu Ufomadu",
"Kat Foster",
"Stephen Tobolowsky",
"Johnny Carson",
"Sam Campbell (comedian)",
"Akiva Schaffer",
"Joe Avati",
"Jason Stephens (television producer)",
"Adam DeVine",
"Linda Wallem",
"Mike Pollock (voice actor)",
"Tom Segura",
"Ross Bagley"
] |
6,042 |
Compact space
|
In mathematics, specifically general topology, compactness is a property that seeks to generalize the notion of a closed and bounded subset of Euclidean space. The idea is that a compact space has no "punctures" or "missing endpoints", i.e., it includes all limiting values of points. For example, the open interval (0,1) would not be compact because it excludes the limiting values of 0 and 1, whereas the closed interval [0,1] would be compact. Similarly, the space of rational numbers \mathbb{Q} is not compact, because it has infinitely many "punctures" corresponding to the irrational numbers, and the space of real numbers \mathbb{R} is not compact either, because it excludes the two limiting values +\infty and -\infty. However, the extended real number line would be compact, since it contains both infinities. There are many ways to make this heuristic notion precise. These ways usually agree in a metric space, but may not be equivalent in other topological spaces.
One such generalization is that a topological space is sequentially compact if every infinite sequence of points sampled from the space has an infinite subsequence that converges to some point of the space. The Bolzano–Weierstrass theorem states that a subset of Euclidean space is compact in this sequential sense if and only if it is closed and bounded. Thus, if one chooses an infinite number of points in the closed unit interval , some of those points will get arbitrarily close to some real number in that space.
For instance, some of the numbers in the sequence accumulate to 0 (while others accumulate to 1).
Since neither 0 nor 1 are members of the open unit interval , those same sets of points would not accumulate to any point of it, so the open unit interval is not compact. Although subsets (subspaces) of Euclidean space can be compact, the entire space itself is not compact, since it is not bounded. For example, considering \mathbb{R}^1 (the real number line), the sequence of points has no subsequence that converges to any real number.
Compactness was formally introduced by Maurice Fréchet in 1906 to generalize the Bolzano–Weierstrass theorem from spaces of geometrical points to spaces of functions. The Arzelà–Ascoli theorem and the Peano existence theorem exemplify applications of this notion of compactness to classical analysis. Following its initial introduction, various equivalent notions of compactness, including sequential compactness and limit point compactness, were developed in general metric spaces. In general topological spaces, however, these notions of compactness are not necessarily equivalent. The most useful notion — and the standard definition of the unqualified term compactness — is phrased in terms of the existence of finite families of open sets that "cover" the space, in the sense that each point of the space lies in some set contained in the family. This more subtle notion, introduced by Pavel Alexandrov and Pavel Urysohn in 1929, exhibits compact spaces as generalizations of finite sets. In spaces that are compact in this sense, it is often possible to patch together information that holds locally – that is, in a neighborhood of each point – into corresponding statements that hold throughout the space, and many theorems are of this character.
The term compact set is sometimes used as a synonym for compact space, but also often refers to a compact subspace of a topological space.
== Historical development ==
In the 19th century, several disparate mathematical properties were understood that would later be seen as consequences of compactness. On the one hand, Bernard Bolzano (1817) had been aware that any bounded sequence of points (in the line or plane, for instance) has a subsequence that must eventually get arbitrarily close to some other point, called a limit point.
Bolzano's proof relied on the method of bisection: the sequence was placed into an interval that was then divided into two equal parts, and a part containing infinitely many terms of the sequence was selected.
The process could then be repeated by dividing the resulting smaller interval into smaller and smaller parts – until it closes down on the desired limit point. The full significance of Bolzano's theorem, and its method of proof, would not emerge until almost 50 years later when it was rediscovered by Karl Weierstrass.
In the 1880s, it became clear that results similar to the Bolzano–Weierstrass theorem could be formulated for spaces of functions rather than just numbers or geometrical points.
The idea of regarding functions as themselves points of a generalized space dates back to the investigations of Giulio Ascoli and Cesare Arzelà.
The culmination of their investigations, the Arzelà–Ascoli theorem, was a generalization of the Bolzano–Weierstrass theorem to families of continuous functions, the precise conclusion of which was that it was possible to extract a uniformly convergent sequence of functions from a suitable family of functions. The uniform limit of this sequence then played precisely the same role as Bolzano's "limit point". Towards the beginning of the twentieth century, results similar to that of Arzelà and Ascoli began to accumulate in the area of integral equations, as investigated by David Hilbert and Erhard Schmidt.
For a certain class of Green's functions coming from solutions of integral equations, Schmidt had shown that a property analogous to the Arzelà–Ascoli theorem held in the sense of mean convergence – or convergence in what would later be dubbed a Hilbert space. This ultimately led to the notion of a compact operator as an offshoot of the general notion of a compact space.
It was Maurice Fréchet who, in 1906, had distilled the essence of the Bolzano–Weierstrass property and coined the term compactness to refer to this general phenomenon (he used the term already in his 1904 paper which led to the famous 1906 thesis).
However, a different notion of compactness altogether had also slowly emerged at the end of the 19th century from the study of the continuum, which was seen as fundamental for the rigorous formulation of analysis.
In 1870, Eduard Heine showed that a continuous function defined on a closed and bounded interval was in fact uniformly continuous. In the course of the proof, he made use of a lemma that from any countable cover of the interval by smaller open intervals, it was possible to select a finite number of these that also covered it.
The significance of this lemma was recognized by Émile Borel (1895), and it was generalized to arbitrary collections of intervals by Pierre Cousin (1895) and Henri Lebesgue (1904). The Heine–Borel theorem, as the result is now known, is another special property possessed by closed and bounded sets of real numbers.
This property was significant because it allowed for the passage from local information about a set (such as the continuity of a function) to global information about the set (such as the uniform continuity of a function). This sentiment was expressed by , who also exploited it in the development of the integral now bearing his name. Ultimately, the Russian school of point-set topology, under the direction of Pavel Alexandrov and Pavel Urysohn, formulated Heine–Borel compactness in a way that could be applied to the modern notion of a topological space. showed that the earlier version of compactness due to Fréchet, now called (relative) sequential compactness, under appropriate conditions followed from the version of compactness that was formulated in terms of the existence of finite subcovers. It was this notion of compactness that became the dominant one, because it was not only a stronger property, but it could be formulated in a more general setting with a minimum of additional technical machinery, as it relied only on the structure of the open sets in a space.
== Basic examples ==
Any finite space is compact; a finite subcover can be obtained by selecting, for each point, an open set containing it. A nontrivial example of a compact space is the (closed) unit interval of real numbers. If one chooses an infinite number of distinct points in the unit interval, then there must be some accumulation point among these points in that interval. For instance, the odd-numbered terms of the sequence get arbitrarily close to 0, while the even-numbered ones get arbitrarily close to 1. The given example sequence shows the importance of including the boundary points of the interval, since the limit points must be in the space itself — an open (or half-open) interval of the real numbers is not compact. It is also crucial that the interval be bounded, since in the interval , one could choose the sequence of points , of which no sub-sequence ultimately gets arbitrarily close to any given real number.
In two dimensions, closed disks are compact since for any infinite number of points sampled from a disk, some subset of those points must get arbitrarily close either to a point within the disc, or to a point on the boundary. However, an open disk is not compact, because a sequence of points can tend to the boundary – without getting arbitrarily close to any point in the interior. Likewise, spheres are compact, but a sphere missing a point is not since a sequence of points can still tend to the missing point, thereby not getting arbitrarily close to any point within the space. Lines and planes are not compact, since one can take a set of equally-spaced points in any given direction without approaching any point.
== Definitions ==
Various definitions of compactness may apply, depending on the level of generality.
A subset of Euclidean space in particular is called compact if it is closed and bounded. This implies, by the Bolzano–Weierstrass theorem, that any infinite sequence from the set has a subsequence that converges to a point in the set. Various equivalent notions of compactness, such as sequential compactness and limit point compactness, can be developed in general metric spaces. That is, is compact if for every collection of open subsets of such that
X = \bigcup_{S \in C}S\ ,
there is a finite subcollection ⊆ such that
X = \bigcup_{S \in F} S\ .
Some branches of mathematics such as algebraic geometry, typically influenced by the French school of Bourbaki, use the term quasi-compact for the general notion, and reserve the term compact for topological spaces that are both Hausdorff and quasi-compact. A compact set is sometimes referred to as a compactum, plural compacta.
=== Compactness of subsets ===
A subset of a topological space is said to be compact if it is compact as a subspace (in the subspace topology). That is, is compact if for every arbitrary collection of open subsets of such that
K \subseteq \bigcup_{S \in C} S\ ,
there is a finite subcollection ⊆ such that
K \subseteq \bigcup_{S \in F} S\ .
Because compactness is a topological property, the compactness of a subset depends only on the subspace topology induced on it. It follows that, if K \subset Z \subset Y, with subset equipped with the subspace topology, then is compact in if and only if is compact in .
=== Characterization ===
If is a topological space then the following are equivalent:
is compact; i.e., every open cover of has a finite subcover.
has a sub-base such that every cover of the space, by members of the sub-base, has a finite subcover (Alexander's sub-base theorem).
is Lindelöf and countably compact.
Any collection of closed subsets of with the finite intersection property has nonempty intersection.
Every net on has a convergent subnet (see the article on nets for a proof).
Every filter on has a convergent refinement.
Every net on has a cluster point.
Every filter on has a cluster point.
Every ultrafilter on converges to at least one point.
Every infinite subset of has a complete accumulation point.
For every topological space , the projection X \times Y \to Y is a closed mapping (see proper map).
Every open cover linearly ordered by subset inclusion contains .
Bourbaki defines a compact space (quasi-compact space) as a topological space where each filter has a cluster point (i.e., 8. in the above).
==== Euclidean space ====
For any subset of Euclidean space, is compact if and only if it is closed and bounded; this is the Heine–Borel theorem.
As a Euclidean space is a metric space, the conditions in the next subsection also apply to all of its subsets. Of all of the equivalent conditions, it is in practice easiest to verify that a subset is closed and bounded, for example, for a closed interval or closed -ball.
==== Metric spaces ====
For any metric space , the following are equivalent (assuming countable choice):
is compact.
is complete and totally bounded (this is also equivalent to compactness for uniform spaces).
is sequentially compact; that is, every sequence in has a convergent subsequence whose limit is in (this is also equivalent to compactness for first-countable uniform spaces).
is limit point compact (also called weakly countably compact); that is, every infinite subset of has at least one limit point in .
is countably compact; that is, every countable open cover of has a finite subcover.
is an image of a continuous function from the Cantor set.
Every decreasing nested sequence of nonempty closed subsets in has a nonempty intersection.
Every increasing nested sequence of proper open subsets in fails to cover .
A compact metric space also satisfies the following properties:
Lebesgue's number lemma: For every open cover of , there exists a number such that every subset of of diameter < is contained in some member of the cover.
is second-countable, separable and Lindelöf – these three conditions are equivalent for metric spaces. The converse is not true; e.g., a countable discrete space satisfies these three conditions, but is not compact.
is closed and bounded (as a subset of any metric space whose restricted metric is ). The converse may fail for a non-Euclidean space; e.g. the real line equipped with the discrete metric is closed and bounded but not compact, as the collection of all singletons of the space is an open cover which admits no finite subcover. It is complete but not totally bounded.
==== Ordered spaces ====
For an ordered space (i.e. a totally ordered set equipped with the order topology), the following are equivalent:
is compact.
Every subset of has a supremum (i.e. a least upper bound) in .
Every subset of has an infimum (i.e. a greatest lower bound) in .
Every nonempty closed subset of has a maximum and a minimum element.
An ordered space satisfying (any one of) these conditions is called a complete lattice.
In addition, the following are equivalent for all ordered spaces , and (assuming countable choice) are true whenever is compact. (The converse in general fails if is not also metrizable.):
Every sequence in has a subsequence that converges in .
Every monotone increasing sequence in converges to a unique limit in .
Every monotone decreasing sequence in converges to a unique limit in .
Every decreasing nested sequence of nonempty closed subsets 1 ⊇ 2 ⊇ ... in has a nonempty intersection.
Every increasing nested sequence of proper open subsets 1 ⊆ 2 ⊆ ... in fails to cover .
==== Characterization by continuous functions ====
Let be a topological space and the ring of real continuous functions on .
For each , the evaluation map \operatorname{ev}_p\colon C(X)\to \mathbb{R}
given by is a ring homomorphism.
The kernel of is a maximal ideal, since the residue field is the field of real numbers, by the first isomorphism theorem. A topological space is pseudocompact if and only if every maximal ideal in has residue field the real numbers. For completely regular spaces, this is equivalent to every maximal ideal being the kernel of an evaluation homomorphism. There are pseudocompact spaces that are not compact, though.
In general, for non-pseudocompact spaces there are always maximal ideals in such that the residue field is a (non-Archimedean) hyperreal field. The framework of non-standard analysis allows for the following alternative characterization of compactness: a topological space is compact if and only if every point of the natural extension is infinitely close to a point of (more precisely, is contained in the monad of ).
==== Hyperreal definition ====
A space is compact if its hyperreal extension (constructed, for example, by the ultrapower construction) has the property that every point of is infinitely close to some point of . For example, an open real interval is not compact because its hyperreal extension contains infinitesimals, which are infinitely close to 0, which is not a point of .
== Sufficient conditions ==
A closed subset of a compact space is compact.
A finite union of compact sets is compact.
A continuous image of a compact space is compact.
The intersection of any non-empty collection of compact subsets of a Hausdorff space is compact (and closed);
If is not Hausdorff then the intersection of two compact subsets may fail to be compact (see footnote for example).
The product of any collection of compact spaces is compact. (This is Tychonoff's theorem, which is equivalent to the axiom of choice.)
In a metrizable space, a subset is compact if and only if it is sequentially compact (assuming countable choice)
A finite set endowed with any topology is compact.
== Properties of compact spaces ==
A compact subset of a Hausdorff space is closed.
If is not Hausdorff then a compact subset of may fail to be a closed subset of (see footnote for example).}}. Then is a compact set but it is not closed.
}}
If is not Hausdorff then the closure of a compact set may fail to be compact (see footnote for example).} does not have a finite subcover.
}}
In any topological vector space (TVS), a compact subset is complete. However, every non-Hausdorff TVS contains compact (and thus complete) subsets that are not closed.
If and are disjoint compact subsets of a Hausdorff space , then there exist disjoint open sets and in such that and .
A continuous bijection from a compact space into a Hausdorff space is a homeomorphism.
A compact Hausdorff space is normal and regular.
If a space is compact and Hausdorff, then no finer topology on is compact and no coarser topology on is Hausdorff.
If a subset of a metric space is compact then it is -bounded.
=== Functions and compact spaces ===
Since a continuous image of a compact space is compact, the extreme value theorem holds for such spaces: a continuous real-valued function on a nonempty compact space is bounded above and attains its supremum.
(Slightly more generally, this is true for an upper semicontinuous function.) As a sort of converse to the above statements, the pre-image of a compact space under a proper map is compact.
=== Compactifications ===
Every topological space is an open dense subspace of a compact space having at most one point more than , by the Alexandroff one-point compactification.
By the same construction, every locally compact Hausdorff space is an open dense subspace of a compact Hausdorff space having at most one point more than .
=== Ordered compact spaces ===
A nonempty compact subset of the real numbers has a greatest element and a least element.
Let be a simply ordered set endowed with the order topology.
Then is compact if and only if is a complete lattice (i.e. all subsets have suprema and infima).
== Examples ==
Any finite topological space, including the empty set, is compact. More generally, any space with a finite topology (only finitely many open sets) is compact; this includes in particular the trivial topology.
Any space carrying the cofinite topology is compact.
Any locally compact Hausdorff space can be turned into a compact space by adding a single point to it, by means of Alexandroff one-point compactification. The one-point compactification of \mathbb{R} is homeomorphic to the circle ; the one-point compactification of \mathbb{R}^2 is homeomorphic to the sphere . Using the one-point compactification, one can also easily construct compact spaces which are not Hausdorff, by starting with a non-Hausdorff space.
The right order topology or left order topology on any bounded totally ordered set is compact. In particular, Sierpiński space is compact.
No discrete space with an infinite number of points is compact. The collection of all singletons of the space is an open cover which admits no finite subcover. Finite discrete spaces are compact.
In \mathbb{R} carrying the lower limit topology, no uncountable set is compact.
In the cocountable topology on an uncountable set, no infinite set is compact. Like the previous example, the space as a whole is not locally compact but is still Lindelöf.
The closed unit interval is compact. This follows from the Heine–Borel theorem. The open interval is not compact: the open cover \left( \frac{1}{n}, 1 - \frac{1}{n} \right) for does not have a finite subcover. Similarly, the set of rational numbers in the closed interval is not compact: the sets of rational numbers in the intervals \left[0, \frac{1}{\pi} - \frac{1}{n}\right]\text{ and }\left[\frac{1}{\pi} + \frac{1}{n}, 1\right] cover all the rationals in [0, 1] for but this cover does not have a finite subcover. Here, the sets are open in the subspace topology even though they are not open as subsets of \mathbb{R}.
The set \mathbb{R} of all real numbers is not compact as there is a cover of open intervals that does not have a finite subcover. For example, intervals , where takes all integer values in , cover \mathbb{R} but there is no finite subcover.
On the other hand, the extended real number line carrying the analogous topology is compact; note that the cover described above would never reach the points at infinity and thus would not cover the extended real line. In fact, the set has the homeomorphism to [−1, 1] of mapping each infinity to its corresponding unit and every real number to its sign multiplied by the unique number in the positive part of interval that results in its absolute value when divided by one minus itself, and since homeomorphisms preserve covers, the Heine-Borel property can be inferred.
For every natural number , the -sphere is compact. Again from the Heine–Borel theorem, the closed unit ball of any finite-dimensional normed vector space is compact. This is not true for infinite dimensions; in fact, a normed vector space is finite-dimensional if and only if its closed unit ball is compact.
On the other hand, the closed unit ball of the dual of a normed space is compact for the weak-* topology. (Alaoglu's theorem)
The Cantor set is compact. In fact, every compact metric space is a continuous image of the Cantor set.
Consider the set of all functions from the real number line to the closed unit interval, and define a topology on so that a sequence \{f_n\} in converges towards if and only if \{f_n(x)\} converges towards for all real numbers . There is only one such topology; it is called the topology of pointwise convergence or the product topology. Then is a compact topological space; this follows from the Tychonoff theorem.
A subset of the Banach space of real-valued continuous functions on a compact Hausdorff space is relatively compact if and only if it is equicontinuous and pointwise bounded (Arzelà–Ascoli theorem).
Consider the set of all functions satisfying the Lipschitz condition for all . Consider on the metric induced by the uniform distance d(f, g) = \sup_{x \in [0, 1]} |f(x) - g(x)|. Then by the Arzelà–Ascoli theorem the space is compact.
The spectrum of any bounded linear operator on a Banach space is a nonempty compact subset of the complex numbers \mathbb{C}. Conversely, any compact subset of \mathbb{C} arises in this manner, as the spectrum of some bounded linear operator. For instance, a diagonal operator on the Hilbert space \ell^2 may have any compact nonempty subset of \mathbb{C} as spectrum.
The space of Borel probability measures on a compact Hausdorff space is compact for the vague topology, by the Alaoglu theorem.
A collection of probability measures on the Borel sets of Euclidean space is called tight if, for any positive epsilon, there exists a compact subset containing all but at most epsilon of the mass of each of the measures. Helly's theorem then asserts that a collection of probability measures is relatively compact for the vague topology if and only if it is tight.
=== Algebraic examples ===
Topological groups such as an orthogonal group are compact, while groups such as a general linear group are not.
Since the -adic integers are homeomorphic to the Cantor set, they form a compact set.
Any global field K is a discrete additive subgroup of its adele ring, and the quotient space is compact. This was used in John Tate's thesis to allow harmonic analysis to be used in number theory.
The spectrum of any commutative ring with the Zariski topology (that is, the set of all prime ideals) is compact, but never Hausdorff (except in trivial cases). In algebraic geometry, such topological spaces are examples of quasi-compact schemes, "quasi" referring to the non-Hausdorff nature of the topology.
The spectrum of a Boolean algebra is compact, a fact which is part of the Stone representation theorem. Stone spaces, compact totally disconnected Hausdorff spaces, form the abstract framework in which these spectra are studied. Such spaces are also useful in the study of profinite groups.
The structure space of a commutative unital Banach algebra is a compact Hausdorff space.
The Hilbert cube is compact, again a consequence of Tychonoff's theorem.
A profinite group (e.g. Galois group) is compact.
|
[
"second-countable space",
"Alexander's sub-base theorem",
"closed set",
"Sierpiński space",
"Tychonoff theorem",
"product topology",
"Eberlein compactum",
"bounded set",
"scheme (mathematics)",
"locally compact",
"Continuous functions on a compact Hausdorff space",
"Erhard Schmidt",
"subcover",
"axiom of choice",
"singleton (mathematics)",
"Cover (topology)",
"Compactness theorem",
"topological property",
"topological space",
"rational numbers",
"mean convergence",
"unit interval",
"first isomorphism theorem",
"non-standard analysis",
"normed vector space",
"Regular space",
"discrete metric",
"finite intersection property",
"p-adic numbers",
"extended real number line",
"total order",
"Orthocompact space",
"hyperreal field",
"Émile Borel",
"proper map",
"homeomorphism",
"dense topological subspace",
"topological vector space",
"Totally bounded space",
"Heine–Borel theorem",
"interval (mathematics)",
"uniform convergence",
"Lebesgue integral",
"cocountable topology",
"Hilbert cube",
"monad (non-standard analysis)",
"sequentially compact",
"sequence",
"orthogonal group",
"point-set topology",
"Hilbert space",
"Banach space",
"Galois group",
"Alexandroff one-point compactification",
"spectrum of an operator",
"Singleton (mathematics)",
"infinite sequence",
"Encyclopaedia Britannica",
"continuous function",
"right order topology",
"bounded linear operator",
"first-countable",
"profinite group",
"Pavel Alexandrov",
"residue field",
"Nicolas Bourbaki",
"extreme value theorem",
"closed mapping",
"Lebesgue's number lemma",
"Karl Weierstrass",
"Pavel Urysohn",
"uniform space",
"metric space",
"David Hilbert",
"lower limit topology",
"Rendiconti del Circolo Matematico di Palermo",
"metrizable space",
"left order topology",
"totally ordered set",
"method of bisection",
"structure space",
"discrete space",
"Sequentially compact space",
"hyperreal number",
"Giulio Ascoli",
"spectrum of a ring",
"countable choice",
"trivial topology",
"particular point topology",
"open cover",
"maximal ideal",
"order topology",
"Stone representation theorem",
"Euclidean space",
"axiom of countable choice",
"completely regular space",
"closed unit ball",
"limit (mathematics)",
"Separable space",
"real line",
"finite topology",
"complex number",
"Topological group",
"Cantor set",
"singleton set",
"subspace topology",
"complete accumulation point",
"completeness (topology)",
"Filters in topology",
"Hausdorff space",
"Relatively compact subspace",
"separation axiom",
"Paracompact space",
"Infinity",
"accumulation point",
"Pierre Cousin (mathematician)",
"Alaoglu's theorem",
"open set",
"kernel (algebra)",
"Cesare Arzelà",
"Maurice Fréchet",
"finite set",
"Disk (mathematics)",
"compact operator",
"cofinite topology",
"complete lattice",
"linear continuum",
"homeomorphic",
"general topology",
"n-sphere",
"Zariski topology",
"subset",
"sequential compactness",
"neighbourhood (mathematics)",
"real number",
"Eduard Heine",
"rational number",
"Peano existence theorem",
"Tychonoff's theorem",
"subsequence",
"uniformly continuous",
"number theory",
"Stone space",
"logical equivalence",
"boundary (topology)",
"totally bounded",
"global field",
"Green's functions",
"Limit point of a sequence",
"Bolzano–Weierstrass theorem",
"Limit point of a set",
"continuous function (topology)",
"cover (topology)",
"Noetherian topological space",
"irrational number",
"commutative ring",
"totally disconnected space",
"adele ring",
"sequence spaces",
"infinitesimal",
"complete space",
"pseudocompact space",
"Banach algebra",
"Tate's thesis",
"empty set",
"Boolean algebra",
"Union (set theory)",
"extended real numbers",
"separated sets",
"probability measure",
"Annales Scientifiques de l'École Normale Supérieure",
"local property",
"Bernard Bolzano",
"pointwise convergence",
"Maurice René Fréchet",
"general linear group",
"vague topology",
"ultrafilter (set theory)",
"Exhaustion by compact sets",
"sequence (mathematics)",
"non-archimedean field",
"Lindelöf space",
"Arzelà–Ascoli theorem",
"John Tate (mathematician)",
"Normal space",
"Henri Lebesgue",
"finite topological space",
"ultrapower construction",
"integral equation",
"Metacompact space",
"Totally bounded",
"neighborhood (topology)",
"net (mathematics)",
"Lipschitz condition",
"function space",
"countably compact",
"set (mathematics)",
"algebraic geometry",
"Compactly generated space",
"Limit of a sequence",
"natural number",
"harmonic analysis",
"limit point compact",
"Quasi-compact morphism",
"mathematics"
] |
6,045 |
Clodius
|
Clodius is an alternate form of the Roman nomen Claudius, a patrician gens that was traditionally regarded as Sabine in origin. The alternation of o and au is characteristic of the Sabine dialect. The feminine form is Clodia.
==Republican era==
===Publius Clodius Pulcher===
During the Late Republic, the spelling Clodius is most prominently associated with Publius Clodius Pulcher, a popularis politician who gave up his patrician status through an order in order to qualify for the office of tribune of the plebs. Clodius positioned himself as a champion of the urban plebs, supporting free grain for the poor and the right of association in guilds (collegia); because of this individual's ideology, Clodius has often been taken as a more "plebeian" spelling and a gesture of political solidarity. Clodius's two elder brothers, the Appius Claudius Pulcher who was consul in 54 BC and the C. Claudius Pulcher who was praetor in 56 BC, conducted more conventional political careers and are referred to in contemporary sources with the traditional spelling.
The view that Clodius represents a plebeian or politicized form has been questioned by Clodius's chief modern-era biographer. In The Patrician Tribune, W. Jeffrey Tatum points out that the spelling is also associated with Clodius's sisters and that "the political explanation … is almost certainly wrong." A plebeian branch of the gens, the Claudii Marcelli, retained the supposedly patrician spelling, while there is some inscriptional evidence that the -o- form may also have been used on occasion by close male relatives of the "patrician tribune" Clodius. Tatum argues that the use of -o- by the "chic" Clodia was a fashionable affectation, and that Clodius, whose perhaps inordinately loving relationship with his sister was the subject of much gossip and insinuation, was imitating his stylish sibling. The linguistic variation of o for au was characteristic of the Umbrian language, of which Sabine was a branch. Forms using o were considered archaic or rustic in the 50s BC, and the use of Clodius would have been either a whimsical gesture of pastoral fantasy, or a trendy assertion of antiquarian authenticity.
===Other Clodii of the Republic===
In addition to Clodius, Clodii from the Republican era include:
Gnaeus Cornelius Lentulus Clodianus, presumably a "Clodius" before his adoption
Clodius Aesopus, a tragic actor in the 50s BC who may have been a freedman of one of the Clodii Pulchri.
Claudia, daughter of Clodius Pulcher and Fulvia, the first wife of emperor Augustus.
Clodia, sister of Publius Clodius Pulcher, sometimes identified in Catullus' poems as "Lesbia".
Women of the Claudii Marcelli branch were often called "Clodia" in the late Republic.
==Imperial era==
People using the name Clodius during the period of the Roman Empire include:
Gaius Clodius Licinus, consul suffectus in AD 4.
Gaius Clodius Vestalis, possible builder of the Via Clodia
Publius Clodius Thrasea Paetus, senator and philosopher during the reign of Nero
Lucius Clodius Macer, a legatus who revolted against Nero
Publius Clodius Quirinalis, from Arelate in Gaul, teacher of rhetoric in time of Nero
Decimus Clodius Septimius Albinus, commonly known as Clodius Albinus, rival emperor 196–197
Marcus Clodius Pupienus Maximus, known as Pupienus, co-emperor 238
Titus Clodius Pupienus Pulcher Maximus, son of emperor Pupienus and suffect consul c. 235
===Clodii Celsini===
The Clodii Celsini continued to practice the traditional religions of antiquity in the face of Christian hegemony through at least the 4th century, when Clodius Celsinus Adelphius (see below) converted. Members of this branch include:
Quintus Fabius Clodius Agrippianus Celsinus, proconsul of Caria in 249 and the son of Clodius Celsinus (b. ca. 185); see for other members of the family.
Clodius Celsinus Adelphius, praefectus urbi in 351.
Quintus Clodius Hermogenianus Olybrius, consul 379
|
[
"Lucius Clodius Macer",
"Sabine",
"Roman Republic",
"Clodius Aesopus",
"Roman adoption",
"Arelate",
"Decline of Greco-Roman polytheism",
"Caria",
"Publius Clodius Thrasea Paetus",
"Quintus Fabius Clodius Agrippianus Celsinus",
"Clodio",
"Leges Clodiae",
"Salian Franks",
"gens",
"Gaius Claudius Pulcher (praetor 56 BC)",
"Gaius Clodius Vestalis",
"Patrician (ancient Rome)",
"Roman consul",
"legatus",
"grammatical gender",
"Collegium (ancient Rome)",
"tribune",
"Fulvia",
"Catullus",
"Gaius Clodius Licinus",
"Roman Empire",
"Publius Clodius Quirinalis",
"Clodius Albinus",
"ancient Rome",
"Religious conversion",
"Clodius Celsinus Adelphius",
"Claudia (wife of Octavian)",
"freedman",
"plebs",
"pastoral",
"ancient Roman religion",
"Titus Clodius Pupienus Pulcher Maximus",
"Via Clodia",
"Gnaeus Cornelius Lentulus Clodianus",
"Lesbia",
"Pupienus",
"Umbrian language",
"Gaul",
"Quintus Clodius Hermogenianus Olybrius",
"Appius Claudius Pulcher (consul 54 BC)",
"Publius Clodius Pulcher",
"Roman naming conventions",
"proconsul",
"praefectus urbi",
"populares",
"Claudia gens",
"rhetoric",
"epigraphy",
"Clodia (wife of Metellus)",
"Nero",
"Claudii Marcelli",
"antiquarianism"
] |
6,046 |
Cicero
|
Marcus Tullius Cicero ( ; ; 3 January 106 BC – 7 December 43 BC) was a Roman statesman, lawyer, scholar, philosopher, orator, writer and Academic skeptic, who tried to uphold optimate principles during the political crises that led to the establishment of the Roman Empire. His extensive writings include treatises on rhetoric, philosophy and politics. He is considered one of Rome's greatest orators and prose stylists and the innovator of what became known as "Ciceronian rhetoric". Cicero was educated in Rome and in Greece. He came from a wealthy municipal family of the Roman equestrian order, and served as consul in 63 BC.
He greatly influenced both ancient and modern reception of the Latin language. A substantial part of his work has survived, and he was admired by both ancient and modern authors alike. Cicero adapted the arguments of the chief schools of Hellenistic philosophy in Latin and coined a large portion of Latin philosophical vocabulary via lexical innovation (e.g. neologisms such as , generator, , infinitio, , ), almost 150 of which were the result of translating Greek philosophical terms.
Though he was an accomplished orator and successful lawyer, Cicero believed his political career was his most important achievement. It was during his consulship that the Catiline conspiracy attempted to overthrow the government through an attack on the city by outside forces, and Cicero (by his own account) suppressed the revolt by summarily and controversially executing five conspirators without trial, an act which would later lead to his exile. During the chaotic middle period of the first century BC, marked by civil wars and the dictatorship of Julius Caesar, Cicero was a supporter of the Optimates faction. Following Caesar's death, Cicero became an enemy of Mark Antony in the ensuing power struggle, attacking him in a series of speeches. He was proscribed as an enemy of the state by the Second Triumvirate and consequently executed by soldiers operating on their behalf in 43 BC, having been intercepted during an attempted flight from the Italian peninsula. His severed hands and head (taken by order of Antony and displayed representing the repercussions of his anti-Antonian actions as a writer and as an orator, respectively) were then displayed on the Rostra.
Petrarch's rediscovery of Cicero's letters is often credited for initiating the 14th-century Renaissance in public affairs, humanism, and classical Roman culture. According to Polish historian Tadeusz Zieliński, "the Renaissance was above all things a revival of Cicero, and only after him and through him of the rest of Classical antiquity." The peak of Cicero's authority and prestige came during the 18th-century Enlightenment, and his impact on leading Enlightenment thinkers and political theorists such as John Locke, David Hume, Montesquieu, and Edmund Burke was substantial. His works rank among the most influential in global culture, and today still constitute one of the most important bodies of primary material for the writing and revision of Roman history, especially the last days of the Roman Republic.
== Early life ==
Marcus Tullius Cicero was born on 3 January 106 BC in Arpinum, a hill town southeast of Rome. He belonged to the tribus Cornelia. His father was a wealthy member of the equestrian order and possessed good connections in Rome. However, not being of robust health (he experienced poor digestion and inflammation of the eyes), he could not enter public life and studied extensively to compensate. Little is known about Cicero's mother Helvia, but Cicero's brother Quintus wrote in a letter that she was a thrifty housewife.
Cicero's cognomen, a hereditary nickname, comes from the Latin for chickpea, . Plutarch explains that the name was originally given to one of Cicero's ancestors who had a cleft in the tip of his nose resembling a chickpea. The famous family names of Fabius, Lentulus, and Piso come from the Latin names of beans, lentils, and peas, respectively. Plutarch writes that Cicero was urged to change this deprecatory name when he entered politics, but refused, saying that he would make Cicero more glorious than Scaurus ("Swollen-ankled") and Catulus ("Puppy").
At the age of 15, in 90 BC, Cicero started serving under Pompey Strabo and later Sulla in the Social war between Rome and its Italian allies. When in Rome during the turbulent plebeian tribunate of Publius Sulpicius Rufus in 88 BC which saw a short bout of fighting between the Sulpicius and Sulla, who had been elected consul for that year, Cicero found himself greatly impressed by Sulpicius' oratory even if he disagreed with his politics. He continued his studies at Rome, writing a pamphlet titled On Invention relating to rhetorical argumentation and studying philosophy with Greek academics who had fled the ongoing First Mithridatic War.
=== Education ===
During this period in Roman history, Greek language and cultural studies were highly valued by the elite classes. Cicero was therefore educated in the teachings of the ancient Greek philosophers, poets and historians; as he obtained much of his understanding of the theory and practice of rhetoric from the Greek poet Archias. Cicero used his knowledge of Greek to translate many of the theoretical concepts of Greek philosophy into Latin, thus translating Greek philosophical works for a larger audience. It was precisely his broad education that tied him to the traditional Roman elite.
Cicero's interest in philosophy figured heavily in his later career and led to him providing a comprehensive account of Greek philosophy for a Roman audience, including creating a philosophical vocabulary in Latin. In 87 BC, Philo of Larissa, the head of the Platonic Academy that had been founded by Plato in Athens about 300 years earlier, arrived in Rome. Cicero, "inspired by an extraordinary zeal for philosophy", sat enthusiastically at his feet and absorbed Carneades' Academic Skeptic philosophy.
According to Plutarch, Cicero was an extremely talented student, whose learning attracted attention from all over Rome, affording him the opportunity to study Roman law under Quintus Mucius Scaevola. Cicero's fellow students were Gaius Marius Minor, Servius Sulpicius Rufus (who became a famous lawyer, one of the few whom Cicero considered superior to himself in legal matters), and Titus Pomponius. The latter two became Cicero's friends for life, and Pomponius (who later received the nickname "Atticus", and whose sister married Cicero's brother) would become, in Cicero's own words, "as a second brother", with both maintaining a lifelong correspondence.
In 79 BC, Cicero left for Greece, Asia Minor and Rhodes. This was perhaps to avoid the potential wrath of Sulla, as Plutarch claims, though Cicero himself says it was to hone his skills and improve his physical fitness. In Athens he studied philosophy with Antiochus of Ascalon, the 'Old Academic' and initiator of Middle Platonism. In Asia Minor, he met the leading orators of the region and continued to study with them. Cicero then journeyed to Rhodes to meet his former teacher, Apollonius Molon, who had taught him in Rome. Molon helped Cicero hone the excesses in his style, as well as train his body and lungs for the demands of public speaking. Charting a middle path between the competing Attic and Asiatic styles, Cicero would ultimately become considered second only to Demosthenes among history's orators.
== Early career ==
===Early legal activity===
While Cicero had feared that the law courts would be closed forever, they were reopened in the aftermath of Sulla's civil war and the purging of Sulla's political opponents in the proscriptions. Many of the orators whom Cicero had admired in his youth were now dead from age or political violence. His first major appearance in the courts was in 81 BC at the age of 26 when he delivered Pro Quinctio, a speech defending certain commercial transactions which Cicero had recorded and disseminated.
His more famous speech defending Sextus Roscius of Ameria – – on charges of parricide in 80 BC was his first appearance in criminal court. In this high-profile case, Cicero accused a freedman of the dictator Sulla, Chrysogonus, of fabricating Roscius' father's proscription to obtain Roscius' family's property. Successful in his defence, Cicero tactfully avoided incriminating Sulla of any wrongdoing and developed a positive oratorical reputation for himself.
While Plutarch claims that Cicero left Rome shortly thereafter out of fear of Sulla's response, according to Kathryn Tempest, "most scholars now dismiss this suggestion" because Cicero left Rome after Sulla resigned his dictatorship. Cicero, for his part, later claimed that he left Rome, headed for Asia, to develop his physique and develop his oratory. After marrying his wife, Terentia, in 80 BC, he eventually left for Asia Minor with his brother Quintus, his friend Titus Atticus, and others on a long trip spanning most of 79 through 77 BC. Returning to Rome in 77 BC, Cicero again busied himself with legal defence.
===Early political career===
In 76 BC, at the quaestorian elections, Cicero was elected at the minimum age required – 30 years – in the first returns from the comitia tributa, to the post of quaestor. Ex officio, he also became a member of the Senate. In the quaestorian lot, he was assigned to Sicily for 75 BC. The post, which was largely one related to financial administration in support of the state or provincial governors, proved for Cicero an important place where he could gain clients in the provinces. His time in Sicily saw him balance his duties – largely in terms of sending more grain back to Rome – with his support for the provincials, Roman businessmen in the area, and local potentates. Adeptly balancing those responsibilities, he won their gratitude. He was also appreciated by local Syracusans for the rediscovery of the lost tomb of Archimedes, which he personally financed.
Promising to lend the Sicilians his oratorical voice, he was called on a few years after his quaestorship to prosecute the Roman province's governor Gaius Verres, for abuse of power and corruption. In 70 BC, at the age of 36, Cicero launched his first high-profile prosecution against Verres, an emblem of the corrupt Sullan supporters who had risen in the chaos of the civil war.
The prosecution of Gaius Verres was a great forensic success for Cicero. While Verres hired the prominent lawyer, Quintus Hortensius, after a lengthy period in Sicily collecting testimonials and evidence and persuading witnesses to come forward, Cicero returned to Rome and won the case in a series of dramatic court battles. His unique style of oratory set him apart from the flamboyant Hortensius. On the conclusion of this case, Cicero came to be considered the greatest orator in Rome. The view that Cicero may have taken the case for reasons of his own is viable. Hortensius was, at this point, known as the best lawyer in Rome; to beat him would guarantee much success and the prestige that Cicero needed to start his career. Cicero's oratorical ability is shown in his character assassination of Verres and various other techniques of persuasion used on the jury. One such example is found in the speech In Verrem, where he states "with you on this bench, gentlemen, with Marcus Acilius Glabrio as your president, I do not understand what Verres can hope to achieve". Oratory was considered a great art in ancient Rome and an important tool for disseminating knowledge and promoting oneself in elections, in part because there were no regular newspapers or mass media. Cicero was neither a patrician nor a plebeian noble; his rise to political office despite his relatively humble origins has traditionally been attributed to his brilliance as an orator.
Cicero grew up in a time of civil unrest and war. Sulla's victory in the first of a series of civil wars led to a new constitutional framework that undermined (liberty), the fundamental value of the Roman Republic. Nonetheless, Sulla's reforms strengthened the position of the equestrian class, contributing to that class's growing political power. Cicero was both an Italian and a , but more importantly he was a Roman constitutionalist. His social class and loyalty to the Republic ensured that he would "command the support and confidence of the people as well as the Italian middle classes". The optimates faction never truly accepted Cicero, and this undermined his efforts to reform the Republic while preserving the constitution. Nevertheless, he successfully ascended the cursus honorum, holding each magistracy at or near the youngest possible age: quaestor in 75 BC (age 30), aedile in 69 BC (age 36), and praetor in 66 BC (age 39), when he served as president of the extortion court. He was then elected consul at age 42.
==Consulship==
Cicero, seizing the opportunity offered by optimate fear of reform, was elected consul for the year 63 BC; he was elected with the support of every unit of the centuriate assembly, rival members of the post-Sullan establishment, and the leaders of municipalities throughout post-Social War Italy. His co-consul for the year, Gaius Antonius Hybrida, played a minor role.
He began his consular year by opposing a land bill proposed by a plebeian tribune which would have appointed commissioners with semi-permanent authority over land reform.
Catiline fled and left behind his followers to start the revolution from within while he himself assaulted the city with an army of "moral and financial bankrupts, or of honest fanatics and adventurers". It is alleged that Catiline had attempted to involve the Allobroges, a tribe of Transalpine Gaul, in their plot, but Cicero, working with the Gauls, was able to seize letters that incriminated the five conspirators and forced them to confess in front of the Senate. The senate then deliberated upon the conspirators' punishment. As it was the dominant advisory body to the various legislative assemblies rather than a judicial body, there were limits to its power; however, martial law was in effect, and it was feared that simple house arrest or exile – the standard options – would not remove the threat to the state. At first Decimus Junius Silanus spoke for the "extreme penalty"; but during the debate many were swayed by Julius Caesar, who decried the precedent it would set and argued in favor of life imprisonment in various Italian towns. Cato the Younger then rose in defense of the death penalty and the Senate finally agreed on the matter, and came down in support of the death penalty. Cicero had the conspirators taken to the Tullianum, the notorious Roman prison, where they were strangled. Cicero himself accompanied the former consul Publius Cornelius Lentulus Sura, one of the conspirators, to the Tullianum.
Cicero received the honorific "pater patriae" for his efforts to suppress the conspiracy, but lived thereafter in fear of trial or exile for having put Roman citizens to death without trial. While the senatus consultum ultimum gave some legitimacy to the use of force against the conspirators, Cicero also argued that Catiline's conspiracy, by virtue of its treason, made the conspirators enemies of the state and forfeited the protections intrinsically possessed by Roman citizens. The consuls moved decisively. Antonius Hybrida was dispatched to defeat Catiline in battle that year, preventing Crassus or Pompey from exploiting the situation for their own political aims.
After the suppression of the conspiracy, Cicero was proud of his accomplishment. Some of his political enemies argued that though the act gained Cicero popularity, he exaggerated the extent of his success. He overestimated his popularity again several years later after being exiled from Italy and then allowed back from exile. At this time, he claimed that the republic would be restored along with him.
Shortly after completing his consulship, in late 62 BC, Cicero arranged the purchase of a large townhouse on the Palatine Hill previously owned by Rome's richest citizen, Marcus Licinius Crassus. To finance the purchase, Cicero borrowed some two million sesterces from Publius Cornelius Sulla, whom he had previously defended from court. Cicero boasted his house was "in conspectu prope totius urbis" ("in sight of nearly the whole city"), only a short walk from the Roman Forum.
==Exile and return==
In 60 BC, Julius Caesar invited Cicero to be the fourth member of his existing partnership with Pompey and Marcus Licinius Crassus, an assembly that would eventually be called the First Triumvirate. Cicero refused the invitation because he suspected it would undermine the Republic, and because he was strongly opposed to anything unconstitutional that limited the powers of the consuls and replaced them with non-elected officials.
During Caesar's consulship of 59 BC, the triumvirate had achieved many of their goals of land reform, publicani debt forgiveness, ratification of Pompeian conquests, etc. With Caesar leaving for his provinces, they wished to maintain their hold on politics. They engineered the adoption of patrician Publius Clodius Pulcher into a plebeian family and had him elected as one of the ten tribunes of the plebs for 58 BC. Clodius used the triumvirate's backing to push through legislation that benefited them. He introduced several laws (the leges Clodiae) that made him popular with the people, strengthening his power base, then he turned on Cicero. Clodius passed a law which made it illegal to offer "fire and water" (i.e. shelter or food) to anyone who executed a Roman citizen without a trial.
Cicero, having executed members of the Catiline conspiracy four years previously without formal trial, was clearly the intended target. Furthermore, many believed that Clodius acted in concert with the triumvirate who feared that Cicero would seek to abolish many of Caesar's accomplishments while consul the year before. Cicero argued that the senatus consultum ultimum indemnified him from punishment, and he attempted to gain the support of the senators and consuls, especially of Pompey.
Cicero grew out his hair, dressed in mourning and toured the streets. Clodius' gangs dogged him, hurling abuse, stones and even excrement. Hortensius, trying to rally to his old rival's support, was almost lynched. The Senate and the consuls were cowed. Caesar, who was still encamped near Rome, was apologetic but said he could do nothing when Cicero brought himself to grovel in the proconsul's tent. Everyone seemed to have abandoned Cicero.
After Clodius passed a law to deny to Cicero fire and water (i.e. shelter) within four hundred miles of Rome, Cicero went into exile. He arrived at Thessalonica, on 23 May 58 BC. In his absence, Clodius, who lived next door to Cicero on the Palatine, arranged for Cicero's house to be confiscated by the state, and was even able to purchase a part of the property in order to extend his own house. After the intervention of recently elected tribune Titus Annius Milo, acting on the behalf of Pompey who wanted Cicero as a client, the Senate voted in favor of recalling Cicero from exile. Clodius cast the single vote against the decree. Cicero returned to Italy on 5 August 57 BC, landing at Brundisium. He was greeted by a cheering crowd, and, to his delight, his beloved daughter Tullia. In his Oratio De Domo Sua Ad Pontifices, Cicero convinced the College of Pontiffs to rule that the consecration of his land was invalid, thereby allowing him to regain his property and rebuild his house on the Palatine.
Cicero tried to re-enter politics as an independent operator, but his attempts to attack portions of Caesar's legislation were unsuccessful and encouraged Caesar to re-solidify his political alliance with Pompey and Crassus. The conference at Luca in 56 BC left the three-man alliance in domination of the republic's politics; this forced Cicero to recant and support the triumvirate out of fear from being entirely excluded from public life. After the conference, Cicero lavishly praised Caesar's achievements, got the Senate to vote a thanksgiving for Caesar's victories, and grant money to pay his troops. He also delivered a speech 'On the consular provinces' () which checked an attempt by Caesar's enemies to strip him of his provinces in Gaul. After this, a cowed Cicero concentrated on his literary works. It is uncertain whether he was directly involved in politics for the following few years. His legal work largely consisted of defending allies of the ruling and his own personal friends and allies; he defended his former pupil Marcus Caelius Rufus against a charge of murder in 56. Under the influence of the triumvirs, he had also defended his former enemies Publius Vatinius (in August 54 BCE), Marcus Aemilius Scaurus (between July and September) and Gnaeus Plancius (with the ) in September, which weakened his prestige and sparked attacks on his integrity: Luca Grillo has suggested these cases as the source of the poet Catullus's double-edged comment that Cicero was "the best defender of anybody".
==Governorship of Cilicia==
In 51 BC he reluctantly accepted a promagistracy (as proconsul) in Cilicia for the year; there were few other former consuls eligible as a result of a legislative requirement enacted by Pompey in 52 BC specifying an interval of five years between a consulship or praetorship and a provincial command. He served as proconsul of Cilicia from May 51 BC, arriving in the provinces three months later around August.
In 53 BC Marcus Licinius Crassus had been defeated by the Parthians at the Battle of Carrhae. This opened the Roman East for a Parthian invasion, causing unrest in Syria and Cilicia. Cicero restored calm by his mild system of government. He discovered that a great amount of public property had been embezzled by corrupt previous governors and members of their staff, and did his utmost to restore it. Thus he greatly improved the condition of the cities. He retained the civil rights of, and exempted from penalties, the men who gave the property back. Besides this, he was extremely frugal in his outlays for staff and private expenses during his governorship, and this made him highly popular among the natives.
Besides his activity in ameliorating the hard pecuniary situation of the province, Cicero was also creditably active in the military sphere. Early in his governorship he received information that prince Pacorus, son of Orodes II the king of the Parthians, had crossed the Euphrates, and was ravaging the Syrian countryside and had even besieged Cassius (the interim Roman commander in Syria) in Antioch. Cicero eventually marched with two understrength legions and a large contingent of auxiliary cavalry to Cassius's relief. Pacorus and his army had already given up on besieging Antioch and were heading south through Syria, ravaging the countryside again. Cassius and his legions followed them, harrying them wherever they went, eventually ambushing and defeating them near Antigonea.
Another large troop of Parthian horsemen was defeated by Cicero's cavalry who happened to run into them while scouting ahead of the main army. Cicero next defeated some robbers who were based on Mount Amanus and was hailed as imperator by his troops. Afterwards he led his army against the independent Cilician mountain tribes, besieging their fortress of Pindenissum. It took him 47 days to reduce the place, which fell in December. On 30 July 50 BC Cicero left the province to his brother Quintus, who had accompanied him on his governorship as his legate. On his way back to Rome he stopped in Rhodes and then went to Athens, where he caught up with his old friend Titus Pomponius Atticus and met men of great learning.
==Julius Caesar's civil war==
Cicero arrived in Rome on 4 January 49 BC. He stayed outside the pomerium, to retain his promagisterial powers: either in expectation of a triumph or to retain his independent command authority in the coming civil war. The struggle between Pompey and Julius Caesar grew more intense in 50 BC. Cicero favored Pompey, seeing him as a defender of the senate and Republican tradition, but at that time avoided openly alienating Caesar. When Caesar invaded Italy in 49 BC, Cicero fled Rome. Caesar, seeking an endorsement by a senior senator, courted Cicero's favor, but even so Cicero slipped out of Italy and traveled to Dyrrhachium where Pompey's staff was situated. Cicero traveled with the Pompeian forces to Pharsalus in Macedonia in 48 BC, though he was quickly losing faith in the competence and righteousness of the Pompeian side. Eventually, he provoked the hostility of his fellow senator Cato, who told him that he would have been of more use to the cause of the optimates if he had stayed in Rome. After Caesar's victory at the Battle of Pharsalus on 9 August, Cicero refused to take command of the Pompeian forces and continue the war. He returned to Rome, still as a promagistrate with his lictors, in 47 BC, and dismissed them upon his crossing the pomerium and renouncing his command.
In a letter to Varro on , Cicero outlined his strategy under Caesar's dictatorship. Cicero, however, was taken by surprise when the Liberatores assassinated Caesar on the ides of March, 44 BC. Cicero was not included in the conspiracy, even though the conspirators were sure of his sympathy. Marcus Junius Brutus called out Cicero's name, asking him to restore the republic when he lifted his bloodstained dagger after the assassination. A letter Cicero wrote in February 43 BC to Trebonius, one of the conspirators, began, "How I could wish that you had invited me to that most glorious banquet on the Ides of March!" Cicero became a popular leader during the period of instability following the assassination. He had no respect for Mark Antony, who was scheming to take revenge upon Caesar's murderers. In exchange for amnesty for the assassins, he arranged for the Senate to agree not to declare Caesar to have been a tyrant, which allowed the Caesarians to have lawful support and kept Caesar's reforms and policies intact.
==Opposition to Mark Antony and death==
In April 43 BC, "diehard republicans" may have revived the ancient position of princeps senatus (leader of the senate) for Cicero. This position had been very prestigious until the constitutional reforms of Sulla in 82–80 BC, which removed most of its importance.
On the other side, Antony was consul and leader of the Caesarian faction, and unofficial executor of Caesar's public will. Relations between the two were never friendly and worsened after Cicero claimed that Antony was taking liberties in interpreting Caesar's wishes and intentions. Octavian was Caesar's adopted son and heir. After he returned to Italy, Cicero began to play him against Antony. He praised Octavian, declaring he would not make the same mistakes as his father. He attacked Antony in a series of speeches he called the Philippics, named after Demosthenes's denunciations of Philip II of Macedon. At the time, Cicero's popularity as a public figure was unrivalled.
Cicero supported Decimus Junius Brutus Albinus as governor of Cisalpine Gaul (Gallia Cisalpina) and urged the Senate to name Antony an enemy of the state. The speech of Lucius Piso, Caesar's father-in-law, delayed proceedings against Antony. Antony was later declared an enemy of the state when he refused to lift the siege of Mutina, which was in the hands of Decimus Brutus. Cicero's plan to drive out Antony failed. Antony and Octavian reconciled and allied with Lepidus to form the Second Triumvirate after the successive battles of Forum Gallorum and Mutina. The alliance came into official existence with the lex Titia, passed on 27 November 43 BC, which gave each triumvir a consular imperium for five years. The Triumvirate immediately began a proscription of their enemies, modeled after that of Sulla in 82 BC. Cicero and all of his contacts and supporters were numbered among the enemies of the state, even though Octavian argued for two days against Cicero being added to the list.
Cicero was one of the most viciously and doggedly hunted among the proscribed. He was viewed with sympathy by a large segment of the public and many people refused to report that they had seen him. He was caught on 7 December 43 BC leaving his villa in Formiae in a litter heading to the seaside, where he hoped to embark on a ship destined for Macedonia. When his killers – Herennius (a Centurion) and Popilius (a Tribune) – arrived, Cicero's own slaves said they had not seen him, but he was given away by Philologus, a freedman of his brother Quintus Cicero.
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He bowed to his captors, leaning his head out of the litter in a gladiatorial gesture to ease the task. By baring his neck and throat to the soldiers, he was indicating that he would not resist. According to Plutarch, Herennius first slew him, then cut off his head. On Antony's instructions his hands, which had penned the Philippics against Antony, were cut off as well; these were nailed along with his head on the Rostra in the Forum Romanum according to the tradition of Marius and Sulla, both of whom had displayed the heads of their enemies in the Forum. Cicero was the only victim of the proscriptions who was displayed in that manner. According to Cassius Dio, in a story often mistakenly attributed to Plutarch, Antony's wife Fulvia took Cicero's head, pulled out his tongue, and jabbed it repeatedly with her hairpin in final revenge against Cicero's power of speech.
Cicero's son, Marcus Tullius Cicero Minor, during his year as a consul in 30 BC, avenged his father's death, to a certain extent, when he announced to the Senate Mark Antony's naval defeat at Actium in 31 BC by Octavian.
Octavian is reported to have praised Cicero as a patriot and a scholar of meaning in later times, within the circle of his family. However, it was Octavian's acquiescence that had allowed Cicero to be killed, as Cicero was condemned by the new triumvirate.
Cicero's career as a statesman was marked by inconsistencies and a tendency to shift his position in response to changes in the political climate. His indecision may be attributed to his sensitive and impressionable personality; he was prone to overreaction in the face of political and private change. "Would that he had been able to endure prosperity with greater self-control, and adversity with more fortitude!" wrote C. Asinius Pollio, a contemporary Roman statesman and historian.
== Personal life and family ==
Cicero married Terentia probably at the age of 27, in 79 BC. According to the upper-class mores of the day it was a marriage of convenience but lasted harmoniously for nearly 30 years. Terentia's family was wealthy, probably the plebeian noble house of Terenti Varrones, thus meeting the needs of Cicero's political ambitions in both economic and social terms. She had a half-sister named Fabia, who as a child had become a Vestal Virgin, a great honour. Terentia was a strong-willed woman and (citing Plutarch) "took more interest in her husband's political career than she allowed him to take in household affairs".
In the 50s BC, Cicero's letters to Terentia became shorter and colder. He complained to his friends that Terentia had betrayed him but did not specify in which sense. Perhaps the marriage could not outlast the strain of the political upheaval in Rome, Cicero's involvement in it, and various other disputes between the two. The divorce appears to have taken place in 51 BC or shortly before. In 46 or 45 BC, Cicero married a young girl, Publilia, who had been his ward. It is thought that Cicero needed her money, particularly after having to repay the dowry of Terentia, who came from a wealthy family.
Although his marriage to Terentia was one of convenience, it is commonly known that Cicero held great love for his daughter Tullia. When she suddenly became ill in February 45 BC and died after having seemingly recovered from giving birth to a son in January, Cicero was stunned. "I have lost the one thing that bound me to life," he wrote to Atticus. Atticus told him to come for a visit during the first weeks of his bereavement, so that he could comfort him when his pain was at its greatest. In Atticus's large library, Cicero read everything that the Greek philosophers had written about overcoming grief, "but my sorrow defeats all consolation." Caesar and Brutus, as well as Servius Sulpicius Rufus, sent him letters of condolence.
Cicero hoped that his son Marcus would become a philosopher like him, but Marcus himself wished for a military career. He joined the army of Pompey in 49 BC, and after Pompey's defeat at Pharsalus 48 BC, he was pardoned by Caesar. Cicero sent him to Athens to study as a disciple of the peripatetic philosopher Kratippos in 48 BC, but he used this absence from "his father's vigilant eye" to "eat, drink, and be merry." After Cicero's death, he joined the army of the Liberatores but was later pardoned by Augustus. Augustus's bad conscience for having given in to Cicero's being put on the proscription list during the Second Triumvirate led him to aid considerably Marcus Minor's career. He became an augur and was nominated consul in 30 BC together with Augustus. As such, he was responsible for revoking the honors of Mark Antony, who was responsible for the proscription and could in this way take revenge. Later he was appointed proconsul of Syria and the province of Asia.
==Legacy==
Cicero has been traditionally considered the master of Latin prose, with Quintilian declaring that Cicero was "not the name of a man, but of eloquence itself." The English words Ciceronian (meaning "eloquent") and cicerone (meaning "local guide") derive from his name. He is credited with transforming Latin from a modest utilitarian language into a versatile literary medium capable of expressing abstract and complicated thoughts with clarity. Julius Caesar praised Cicero's achievement by saying "it is more important to have greatly extended the frontiers of the Roman spirit than the frontiers of the Roman empire". According to John William Mackail, "Cicero's unique and imperishable glory is that he created the language of the civilized world, and used that language to create a style which nineteen centuries have not replaced, and in some respects have hardly altered."
Cicero was also an energetic writer with an interest in a wide variety of subjects, in keeping with the Hellenistic philosophical and rhetorical traditions in which he was trained. The quality and ready accessibility of Ciceronian texts favored very wide distribution and inclusion in teaching curricula, as suggested by a graffito at Pompeii, admonishing: "You will like Cicero, or you will be whipped".
Cicero was greatly admired by influential Church Fathers such as Augustine of Hippo, who credited Cicero's lost Hortensius for his eventual conversion to Christianity, and St. Jerome, who had a feverish vision in which he was accused of being "follower of Cicero and not of Christ" before the judgment seat.
This influence further increased after the Early Middle Ages in Europe, where more of his writings survived than any other Latin author's. Medieval philosophers were influenced by Cicero's writings on natural law and innate rights.
Petrarch's rediscovery of Cicero's letters provided the impetus for searches for ancient Greek and Latin writings scattered throughout European monasteries, and the subsequent rediscovery of classical antiquity led to the Renaissance. Subsequently, Cicero became synonymous with classical Latin to such an extent that a number of humanist scholars began to assert that no Latin word or phrase should be used unless it appeared in Cicero's works, a stance criticised by Erasmus.
His voluminous correspondence, much of it addressed to his friend Atticus, has been especially influential, introducing the art of refined letter writing to European culture. Cornelius Nepos, the first century BC biographer of Atticus, remarked that Cicero's letters contained such a wealth of detail "concerning the inclinations of leading men, the faults of the generals, and the revolutions in the government" that their reader had little need for a history of the period.
Among Cicero's admirers were Desiderius Erasmus, Martin Luther, and John Locke. Following the invention of Johannes Gutenberg's printing press, De Officiis was the second book printed in Europe, after the Gutenberg Bible. Scholars note Cicero's influence on the rebirth of religious toleration in the 17th century.
Cicero was especially popular with the Philosophes of the 18th century, including Edward Gibbon, Diderot, David Hume, Montesquieu, and Voltaire. Gibbon wrote of his first experience reading the author's collective works thus: "I tasted the beauty of the language; I breathed the spirit of freedom; and I imbibed from his precepts and examples the public and private sense of a man...after finishing the great author, a library of eloquence and reason, I formed a more extensive plan of reviewing the Latin classics..."
Voltaire called Cicero "the greatest as well as the most elegant of Roman philosophers" and even staged a play based on Cicero's role in the Catilinarian conspiracy, called Rome Sauvée, ou Catilina, to "make young people who go to the theatre acquainted with Cicero." Voltaire was spurred to pen the drama as a rebuff to his rival Claude Prosper Jolyot de Crébillon's own play Catilina, which had portrayed Cicero as a coward and villain who hypocritically married his own daughter to Catiline.
Montesquieu produced his "Discourse on Cicero" in 1717, in which he heaped praise on the author because he rescued "philosophy from the hands of scholars, and freed it from the confusion of a foreign language". Montesquieu went on to declare that Cicero was "of all the ancients, the one who had the most personal merit, and whom I would prefer to resemble."
Cicero the republican inspired the Founding Fathers of the United States and the revolutionaries of the French Revolution. John Adams said, "As all the ages of the world have not produced a greater statesman and philosopher united than Cicero, his authority should have great weight." Thomas Jefferson names Cicero as one of a handful of major figures who contributed to a tradition "of public right" that informed his draft of the Declaration of Independence and shaped American understandings of "the common sense" basis for the right of revolution. Camille Desmoulins said of the French republicans in 1789 that they were "mostly young people who, nourished by the reading of Cicero at school, had become passionate enthusiasts for liberty".
In the modern era, American libertarian Jim Powell starts his history of liberty with the sentence: "Marcus Tullius Cicero expressed principles that became the bedrock of liberty in the modern world."
Likewise, no other ancient personality has inspired as much venomous dislike as Cicero, especially in more modern times. His commitment to the values of the Republic accommodated a hatred of the poor and persistent opposition to the advocates and mechanisms of popular representation. Friedrich Engels referred to him as "the most contemptible scoundrel in history" for upholding republican "democracy" while at the same time denouncing land and class reforms. Cicero has faced criticism for exaggerating the democratic qualities of republican Rome, and for defending the Roman oligarchy against the popular reforms of Caesar. Michael Parenti admits Cicero's abilities as an orator, but finds him a vain, pompous and hypocritical personality who, when it suited him, could show public support for popular causes that he privately despised. Parenti presents Cicero's prosecution of the Catiline conspiracy as legally flawed at least, and possibly unlawful.
Cicero also had an influence on modern astronomy. Nicolaus Copernicus, searching for ancient views on earth motion, said that he "first ... found in Cicero that Hicetas supposed the earth to move."
Notably, "Cicero" was the name attributed to size 12 font in typesetting table drawers. For ease of reference, type sizes 3, 4, 5, 6, 7, 8, 9, 10, 12, 14, 16, and 20 were all given different names.
==Works==
Cicero was declared a righteous pagan by the Early Church. Subsequent Roman and medieval Christian writers quoted liberally from his works De re publica (On the Commonwealth) and De Legibus (On the Laws), and much of his work has been recreated from these surviving fragments. Cicero also articulated an early, abstract conceptualization of rights, based on ancient law and custom. Of Cicero's books, six on rhetoric have survived, as well as parts of seven on philosophy. Of his speeches, 88 were recorded, but only 52 survive.
==In archaeology==
Cicero's great repute in Italy has led to numerous ruins being identified as having belonged to him, though none have been substantiated with absolute certainty. In Formia, two Roman-era ruins are popularly believed to be Cicero's mausoleum, the Tomba di Cicerone, and the villa where he was assassinated in 43 BC. The latter building is centered around a central hall with Doric columns and a coffered vault, with a separate nymphaeum, on five acres of land near Formia. A modern villa was built on the site after the Rubino family purchased the land from Ferdinand II of the Two Sicilies in 1868. Cicero's supposed tomb is a 24-meter (79 feet) tall tower on an opus quadratum base on the ancient Via Appia outside of Formia. Some suggest that it is not in fact Cicero's tomb, but a monument built on the spot where Cicero was intercepted and assassinated while trying to reach the sea.
In Pompeii, a large villa excavated in the mid 18th century just outside the Herculaneum Gate was widely believed to have been Cicero's, who was known to have owned a holiday villa in Pompeii he called his Pompeianum. The villa was stripped of its fine frescoes and mosaics and then re-buried after 1763 – it has yet to be re-excavated. However, contemporaneous descriptions of the building from the excavators combined with Cicero's own references to his Pompeianum differ, making it unlikely that it is Cicero's villa.
In Rome, the location of Cicero's house has been roughly identified from excavations of the Republican-era stratum on the northwestern slope of the Palatine Hill. Cicero's domus has long been known to have stood in the area, according to his own descriptions and those of later authors, but there is some debate about whether it stood near the base of the hill, very close to the Roman Forum, or nearer to the summit. During his life the area was the most desirable in Rome, densely occupied with Patrician houses including the Domus Publica of Julius Caesar and the home of Cicero's mortal enemy Clodius.
==Notable fictional portrayals==
In Dante's 1320 poem the Divine Comedy, the author encounters Cicero, among other philosophers, in Limbo. Ben Jonson dramatised the conspiracy of Catiline in his play Catiline His Conspiracy, featuring Cicero as a character. Cicero also appears as a minor character in William Shakespeare's play Julius Caesar.
Cicero was portrayed on the motion picture screen by British actor Alan Napier in the 1953 film Julius Caesar, based on Shakespeare's play. He has also been played by such noted actors as Michael Hordern (in Cleopatra), and André Morell (in the 1970 Julius Caesar). Most recently, Cicero was portrayed by David Bamber in the HBO series Rome (2005–2007) and appeared in both seasons.
In the historical novel series Masters of Rome, Colleen McCullough presents a not-so-flattering depiction of Cicero's career, showing him struggling with an inferiority complex and vanity, morally flexible and fatally indiscreet, while his rival Julius Caesar is shown in a more approving light. Cicero is portrayed as a hero in the novel A Pillar of Iron by Taylor Caldwell (1965). Robert Harris' novels Imperium, Lustrum (published under the name Conspirata in the United States) and Dictator comprise a three-part series based on the life of Cicero. In these novels Cicero's character is depicted in a more favorable way than in those of McCullough, with his positive traits equaling or outweighing his weaknesses (while conversely Caesar is depicted as more sinister than in McCullough). Cicero is a major recurring character in the Roma Sub Rosa series of mystery novels by Steven Saylor. He also appears several times as a peripheral character in John Maddox Roberts' SPQR series.
Samuel Barnett portrays Cicero in a 2017 audio drama series pilot produced by Big Finish Productions. A full series was released the following year. All episodes are written by David Llewellyn and directed and produced by Scott Handcock.
Giancarlo Esposito portrays Mayor Franklyn Cicero, a character from Francis Ford Coppola's 2024 sci-fi epic film Megalopolis, which is a modern futuristic interpretation of the Catiline Conspiracy. In the film, Esposito stars opposite Adam Driver, who portrays a character named Cesar Catilina.
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] |
6,047 |
Consul
|
Consul (abbrev. cos.; Latin plural consules) was the title of one of the two chief magistrates of the Roman Republic, and subsequently also an important title under the Roman Empire. The title was used in other European city-states through antiquity and the Middle Ages, in particular in the Republics of Genoa and Pisa, then revived in modern states, notably in the First French Republic. The related adjective is consular, from the Latin consularis.
This usage contrasts with modern terminology, where a consul is a type of diplomat.
==Roman consul==
A consul held the highest elected political office of the Roman Republic (509 to 27 BC), and ancient Romans considered the consulship the highest level of the cursus honorum (an ascending sequence of public offices to which politicians aspired). Consuls were elected to office and held power for one year. There were always two consuls in power at any time.
==Other uses in antiquity==
===Private sphere===
It was not uncommon for an organization under Roman private law to copy the terminology of state and city institutions for its own statutory agents. The founding statute, or contract, of such an organisation was called lex, 'law'. The people elected each year were patricians, members of the upper class.
===City-states===
While many cities, including the Gallic states and the Carthaginian Republic, had a double-headed chief magistracy, another title was often used, such as the Punic sufet, Duumvir, or native styles like Meddix.
==Medieval city-states, communes and municipalities==
=== Republic of Genoa ===
The city-state of Genoa, unlike ancient Rome, bestowed the title of consul on various state officials, not necessarily restricted to the highest. Among these were Genoese officials stationed in various Mediterranean ports, whose role included helping Genoese merchants and sailors in difficulties with the local authorities. Great Britain reciprocated by appointing consuls to Genoa from 1722. This institution, with its name, was later emulated by other powers and is reflected in the modern usage of the word (see Consul (representative)).
=== Republic of Pisa ===
In addition to the Genoese Republic, the Republic of Pisa also took the form of "Consul" in the early stages of its government. The Consulate of the Republic of Pisa was the major government institution present in Pisa from 1087 to 1189. Despite losing space within the government since 1190 in favor of the Podestà, for some periods of the 13th century some citizens were again elected as consuls.
=== Other uses in the Medieval period ===
Throughout most of southern France, a consul ( or ) was an office equivalent to the of the north and roughly similar with English aldermen. The most prominent were those of Bordeaux and Toulouse, which came to be known as jurats and capitouls, respectively. The capitouls of Toulouse were granted transmittable nobility. In many other smaller towns the first consul was the equivalent of a mayor today, assisted by a variable number of secondary consuls and jurats. His main task was to levy and collect tax.
The Dukes of Gaeta often used also the title of "consul" in its Greek form "Hypatos" (see List of Hypati and Dukes of Gaeta).
==French Revolution==
===French Republic 1799–1804===
After Napoleon Bonaparte staged a coup against the Directory government in November 1799, the French Republic adopted a constitution which conferred executive powers upon three consuls, elected for a period of ten years. In reality, the first consul, Bonaparte, dominated his two colleagues and held supreme power, soon making himself consul for life (1802) and eventually, in 1804, emperor.
The office was held by:
Napoleon Bonaparte, Emmanuel-Joseph Sieyès, Roger Ducos, provisional consuls (10 November – 12 December 1799)
Napoleon Bonaparte (first consul), Jean-Jacques Cambacérès (second consul), Charles-François Lebrun (third consul), consuls (12 December 1799 – 18 May 1804)
===Bolognese Republic, 1796===
The short-lived Bolognese Republic, proclaimed in 1796 as a French client republic in the Central Italian city of Bologna, had a government consisting of nine consuls and its head of state was the Presidente del Magistrato, i.e., chief magistrate, a presiding office held for four months by one of the consuls. Bologna already had consuls at some parts of its Medieval history.
===Roman Republic, 1798–1800===
The French-sponsored Roman Republic (15 February 1798 – 23 June 1800) was headed by multiple consuls:
Francesco Riganti, Carlo Luigi Costantini, Duke Bonelli-Crescenzi, Antonio Bassi, Gioacchino Pessuti, Angelo Stampa, Domenico Maggi, provisional consuls (15 February – 20 March 1798)
Liborio Angelucci, Giacomo De Mattheis, Panazzi, Reppi, Ennio Quirino Visconti, consuls (20 March – September 1798)
Brigi, Calisti, Francesco Pierelli, Giuseppe Rey, Federico Maria Domenico Michele, Zaccaleoni, consuls (September – 24 July 1799)
Consular rule was interrupted by the Neapolitan occupation (27 November – 12 December 1798), which installed a Provisional Government:
Prince Giambattista Borghese, Prince Paolo-Maria Aldobrandini, Prince Gibrielli, Marchese Camillo Massimo, Giovanni Ricci (29 November 1798 - 12 December 1798)
Rome was occupied by France (11 July – 28 September 1799) and again by Naples (30 September 1799 – 23 June 1800), bringing an end to the Roman Republic.
==Revolutionary Greece, 1821==
Among the many petty local republics that were formed during the first year of the Greek Revolution, prior to the creation of a unified Provisional Government at the First National Assembly at Epidaurus, were:
The Consulate of Argos (from 26 May 1821, under the Senate of the Peloponnese) had a single head of state, styled consul, 28 March 1821 – 26 May 1821: Stamatellos Antonopoulos
The Consulate of East Greece (Livadeia) (from 15 November 1821, under the Areopagus of East Greece) was headed 1 April 1821 – 15 November 1821 by three consuls: Lambros Nakos, Ioannis Logothetis & Ioannis Filon
Note: in Greek, the term for "consul" is "hypatos" (ὕπατος), which translates as "supreme one", and hence does not necessarily imply a joint office.
==Paraguay, 1813–1844==
In between a series of juntas and various other short-lived regimes, the young republic was governed by "consuls of the republic", with two consuls alternating in power every 4 months:
12 October 1813 – 12 February 1814, José Gaspar Rodríguez de Francia y Velasco
12 February 1814 – 12 June 1814, Fulgencio Yegros y Franco de Torres
12 June 1814 – 3 October 1814, José Gaspar Rodríguez de Francia y Velasco; he stayed on as "supreme dictator" 3 October 1814 – 20 September 1840 (from 6 June 1816 styled "perpetual supreme dictator")
After a few presidents of the Provisional Junta, there were again consuls of the republic, 14 March 1841 – 13 March 1844 (ruling jointly, but occasionally styled "first consul", "second consul"): Carlos Antonio López Ynsfrán (b. 1792 – d. 1862) + Mariano Roque Alonzo Romero (d. 1853) (the lasts of the aforementioned juntistas, Commandant-General of the Army)
Thereafter all republican rulers were styled "president".
==Modern uses of the term==
In modern terminology, a consul is a type of diplomat. The American Heritage Dictionary defines consul as "an official appointed by a government to reside in a foreign country and represent its interests there." The Devil's Dictionary defines Consul as "in American politics, a person who having failed to secure an office from the people is given one by the Administration on condition that he leave the country".
In most governments, the consul is the head of the consular section of an embassy, and is responsible for all consular services such as immigrant and non-immigrant visas, passports, and citizen services for expatriates living or traveling in the host country.
A less common modern usage is when the consul of one country takes a governing role in the host country.
|
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] |
6,050 |
List of equations in classical mechanics
|
Classical mechanics is the branch of physics used to describe the motion of macroscopic objects. It is the most familiar of the theories of physics. The concepts it covers, such as mass, acceleration, and force, are commonly used and known. The subject is based upon a three-dimensional Euclidean space with fixed axes, called a frame of reference. The point of concurrency of the three axes is known as the origin of the particular space.
Classical mechanics utilises many equations—as well as other mathematical concepts—which relate various physical quantities to one another. These include differential equations, manifolds, Lie groups, and ergodic theory. This article gives a summary of the most important of these.
This article lists equations from Newtonian mechanics, see analytical mechanics for the more general formulation of classical mechanics (which includes Lagrangian and Hamiltonian mechanics).
==Classical mechanics==
===Mass and inertia===
===Derived kinematic quantities===
===Derived dynamic quantities===
===General energy definitions===
Every conservative force has a potential energy. By following two principles one can consistently assign a non-relative value to U:
Wherever the force is zero, its potential energy is defined to be zero as well.
Whenever the force does work, potential energy is lost.
===Generalized mechanics===
==Kinematics==
In the following rotational definitions, the angle can be any angle about the specified axis of rotation. It is customary to use θ, but this does not have to be the polar angle used in polar coordinate systems. The unit axial vector
\mathbf{\hat{n}} = \mathbf{\hat{e}}_r\times\mathbf{\hat{e}}_\theta
defines the axis of rotation, \scriptstyle \mathbf{\hat{e}}_r = unit vector in direction of , \scriptstyle \mathbf{\hat{e}}_\theta = unit vector tangential to the angle.
==Galilean frame transforms==
For classical (Galileo-Newtonian) mechanics, the transformation law from one inertial or accelerating (including rotation) frame (reference frame traveling at constant velocity - including zero) to another is the Galilean transform.
Unprimed quantities refer to position, velocity and acceleration in one frame F; primed quantities refer to position, velocity and acceleration in another frame F' moving at translational velocity V or angular velocity Ω relative to F. Conversely F moves at velocity (—V or —Ω) relative to F'. The situation is similar for relative accelerations.
|
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] |
6,051 |
Cursus honorum
|
The , or more colloquially 'ladder of offices'; ) was the sequential order of public offices held by aspiring politicians in the Roman Republic and the early Roman Empire. It was designed for men of senatorial rank. The cursus honorum comprised a mixture of military and political administration posts; the ultimate prize for winning election to each "rung" in the sequence was to become one of the two consuls in a given year.
These rules were altered and flagrantly ignored in the course of the last century of the Republic. For example, Gaius Marius held consulships for five years in a row between 104 BC and 100 BC. He was consul seven times in all, also serving in 107 and 86. Officially presented as opportunities for public service, the offices often became mere opportunities for self-aggrandizement. The constitutional reforms of Sulla between 82 and 79 BC required a ten-year interval before holding the same office again for another term.
To have held each office at the youngest possible age (suo anno, 'in his year') was considered a great political success. For instance, to miss out on a praetorship at 39 meant that one could not become consul at 42. Cicero expressed extreme pride not only in being a novus homo ('new man'; comparable to a "self-made man") who became consul even though none of his ancestors had ever served as a consul, but also in having become consul "in his year".
== Military service ==
Prior to entering political life and the cursus honorum, a young man of senatorial rank was expected to serve around ten years of military duty. The years of service were intended to be mandatory in order to qualify for political office.
Advancement and honors would improve his political prospects, and a successful military career might culminate in the office of military tribune, to which 24 men were elected by the Tribal Assembly each year. From the time of Augustus onwards, twenty quaestors served in the financial administration at Rome or as second-in-command to a governor in the provinces. They could also serve as the paymaster for a legion.
== Aedile ==
At 36 years of age, a promagistrate could stand for election to one of the aediles (pronounced , from aedes, "temple edifice") positions. Of these aediles, two were plebeian and two were patrician, with the patrician aediles called curule aediles. The plebeian aediles were elected by the Plebeian Council and the curule aediles were either elected by the Tribal Assembly or appointed by the reigning consul. The aediles had administrative responsibilities in Rome. They had to take care of the temples (whence their title, from the Latin aedes, "temple"), organize games, and be responsible for the maintenance of the public buildings in Rome. Moreover, they took charge of Rome's water and food supplies; in their capacity as market superintendents, they served sometimes as judges in mercantile affairs.
The aedile was the supervisor of public works; the words "edifice" and "edification" stem from the same root. He oversaw the public works, temples and markets. Therefore, the aediles would have been in some cooperation with the current censors, who had similar or related duties. Also, they oversaw the organization of festivals and games (ludi), which made this a very sought-after office for a career minded politician of the late Republic, as it was a good means of gaining popularity by staging spectacles.
Curule aediles were added at a later date in the 4th century BC; their duties do not differ substantially from plebeian aediles. However, unlike plebeian aediles, curule aediles were allowed certain symbols of rank—the sella curulis or curule chair, for example—and only patricians could stand for election to curule aedile. This later changed, and both plebeians and patricians could stand for curule aedileship.
The elections for curule aedile were at first alternated between patricians and plebeians, until late in the 2nd century BC, when the practice was abandoned and both classes became free to run during all years.
While part of the cursus honorum, this step was optional and not required to hold future offices. Though the office was usually held after the quaestorship and before the praetorship, there are some cases with former praetors serving as aediles.
== Praetor ==
After serving either as quaestor or as aedile, a man of 39 years could run for praetor. During the reign of Augustus this requirement was lowered to 30, at the request of Gaius Maecenas. The number of praetors elected varied through history, generally increasing with time. During the republic, six or eight were generally elected each year to serve judicial functions throughout Rome and other governmental responsibilities. In the absence of the consuls, a praetor would be given command of the garrison in Rome or in Italy. Also, a praetor could exercise the functions of the consuls throughout Rome, but their main function was that of a judge. They would preside over trials involving criminal acts, grant court orders and validate "illegal" acts as acts of administering justice. A praetor was escorted by six lictors, and wielded imperium. After a term as praetor, the magistrate could serve as a provincial governor with the title of propraetor, wielding propraetor imperium, commanding the province's legions, and possessing ultimate authority within his province(s).
Two of the praetors were more prestigious than the others. The first was the Praetor Peregrinus, who was the chief judge in trials involving one or more foreigners. The other was the Praetor Urbanus, the chief judicial office in Rome. He had the power to overturn any verdict by any other courts, and served as judge in cases involving criminal charges against provincial governors. The Praetor Urbanus was not allowed to leave the city for more than ten days. If one of these two praetors was absent from Rome, the other would perform the duties of both.
== Consul ==
The office of consul was the most prestigious of all of the offices on the cursus honorum, and represented the summit of a successful career. The minimum age was 42. Years were identified by the names of the two consuls elected for a particular year; for instance, M. Messalla et M. Pisone consulibus, "in the consulship of Messalla and Piso", dates an event to 61 BC. Consuls were responsible for the city's political agenda, commanded large-scale armies and controlled important provinces. The consuls served for only a year (a restriction intended to limit the amassing of power by individuals) and could only rule when they agreed, because each consul could veto the other's decision.
The consuls would alternate monthly as the chairman of the Senate. They also were the supreme commanders in the Roman army, with each being granted two legions during their consular year. Consuls also exercised the highest juridical power in the Republic, being the only office with the power to override the decisions of the Praetor Urbanus. Only laws and the decrees of the Senate or the People's assembly limited their powers, and only the veto of a fellow consul or a tribune of the plebs could supersede their decisions.
A consul was escorted by twelve lictors, held imperium and wore the toga praetexta. Because the consul was the highest executive office within the Republic, they had the power to veto any action or proposal by any other magistrate, save that of the Tribune of the Plebs. After a consulship, a consul was assigned one of the more important provinces and acted as the governor in the same way that a propraetor did, only owning proconsular imperium. A second consulship could only be attempted after an interval of 10 years to prevent one man holding too much power.
== Dictator and magister equitum ==
Of all the offices within the Roman Republic, none granted as much power and authority as the position of dictator, known as the Master of the People. In times of emergency, the Senate would declare that a dictator was required, and the current consuls would appoint a dictator. This was the only decision that could not be vetoed by the Tribune of the Plebs. The dictator was the sole exception to the Roman legal principles of having multiple magistrates in the same office and being legally able to be held to answer for actions in office. Essentially by definition, only one dictator could serve at a time, and no dictator could ever be held legally responsible for any action during his time in office for any reason.
The dictator was the highest magistrate in degree of imperium and was attended by twenty-four lictors (as were the former Kings of Rome). Although his term lasted only six months instead of twelve (except for the Dictatorships of Sulla and Caesar), all other magistrates reported to the dictator (except for the tribunes of the plebs – although they could not veto any of the dictator's acts), granting the dictator absolute authority in both civil and military matters throughout the Republic. The dictator was free from the control of the Senate in all that he did, could execute anyone without a trial for any reason, and could ignore any law in the performance of his duties. The dictator was the sole magistrate under the Republic that was truly independent in discharging his duties. All of the other offices were extensions of the Senate's executive authority and thus answerable to the Senate. Since the dictator exercised his own authority, he did not suffer this limitation, which was the cornerstone of the office's power.
When a dictator entered office, he appointed to serve as his second-in-command a magister equitum, the Master of the Horse, whose office ceased to exist once the dictator left office. The magister equitum held praetorian imperium, was attended by six lictors, and was charged with assisting the dictator in managing the State. When the dictator was away from Rome, the magister equitum usually remained behind to administer the city. The magister equitum, like the dictator, had unchallengeable authority in all civil and military affairs, with his decisions only being overturned by the dictator himself.
The dictatorship was definitively abolished in 44 BC after the assassination of Gaius Julius Caesar (Lex Antonia).
|
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"equestrian order",
"Roman Republic",
"imperium",
"Gaius Maecenas",
"sacrosanctity",
"Political institutions of ancient Rome",
"aedile",
"Roman censor",
"Roman temple",
"Marcus Valerius Messalla Niger",
"plebeians",
"military tribune",
"Roman assemblies",
"suffect consul",
"constitutional reforms of Sulla",
"Roman Senate",
"Tribune",
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"Outline of ancient Rome",
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"Augustus",
"Aedile",
"Commentarii de Bello Gallico",
"Gaius Marius",
"Plebeian Council",
"toga",
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"Tribal Assembly",
"Glossary of ancient Roman religion",
"Leges Antoniae",
"promagistrate",
"Julius Caesar",
"Tribune of the Plebs",
"Promagistrate",
"novus homo",
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"Marcus Pupius Piso Frugi Calpurnianus",
"University of Alabama Press",
"day's journey",
"proconsul",
"Vigintisexviri",
"Cambridge University Press",
"Yale University Press",
"Curule chair",
"quaestor",
"Roman province",
"Sulla",
"praetor",
"self-made man"
] |
6,056 |
Continental drift
|
Continental drift is a highly supported scientific theory, originating in the early 20th century, that Earth's continents move or drift relative to each other over geologic time. The concept was independently and more fully developed by Alfred Wegener in his 1915 publication, "The Origin of Continents and Oceans".
Wegener was the first to use the phrase "continental drift" (1912, 1915) In 1939 an international geological conference was held in Frankfurt.
|
[
"Journal of Geophysical Research",
"Lower Silurian",
"Lord Kelvin",
"Bathymetry",
"tectonophysics",
"precession",
"Leopold Kober",
"Zeitschrift für Geomorphologie",
"land bridge",
"Pangaea",
"William Henry Pickering",
"oceanic crust",
"Bailey Willis",
"earthworm",
"supercontinent",
"Brazil",
"paleoclimatology",
"Lawrence Morley",
"Africa",
"Scientific American",
"orogeny",
"Challenger expedition",
"Otto Ampferer",
"continent",
"Paul Sophus Epstein",
"Maurice Ewing",
"paleontology",
"Charles Lyell",
"geosyncline",
"Geomagnetic reversal",
"glacial striation",
"thermal expansion",
"Volcanism of Iceland",
"Marie Tharp",
"Geology",
"Seafloor spreading",
"Mesosaurus",
"Kurt Wegener",
"Isostasy",
"Charles Schuchert",
"James Dwight Dana",
"magma",
"Pacific Ocean",
"lithosphere",
"sea",
"India",
"Volcanism",
"slab pull",
"subduction",
"Lystrosaurus",
"Walther Penck",
"Permo-Carboniferous",
"radioactive",
"Peter Paul Rubens",
"Abraham Ortelius",
"Jack Oliver (scientist)",
"Georg Wüst",
"Bruce Heezen",
"ridge-push",
"Centrifugal force (fictitious)",
"extensional tectonics",
"plate tectonics",
"John Perry (engineer)",
"Hans Stille",
"Plasticity (physics)",
"Antarctica",
"Hans Cloos",
"Orogeny",
"Felix Andries Vening Meinesz",
"Gondwana",
"Frankfurt",
"Johannes Herman Frederik Umbgrove",
"Antonio Snider-Pellegrini",
"Tethys Ocean",
"Vine–Matthews–Morley hypothesis",
"mantle convection",
"Israel C. White",
"World War II",
"Atlantic Ocean",
"Roberto Mantovani",
"Great Global Rift",
"Iceland",
"reptile",
"geoid",
"Émile Argand",
"Southern Peninsula (Iceland)",
"convection cell",
"South Africa",
"Samuel Warren Carey",
"Mantle (geology)",
"Potsdam Sandstone",
"Mid-Atlantic Ridge",
"Frank Bursley Taylor",
"Carl Troll",
"Expanding Earth theory",
"isostasy",
"Rock (geology)",
"tillite",
"continental shelf",
"Cretaceous",
"The Observer",
"Alpine orogeny",
"orogen",
"Alfred Russel Wallace",
"Land bridge",
"Contracting Earth",
"David Attenborough",
"Arthur Holmes",
"scientific theory",
"Indian subcontinent",
"Alexander von Humboldt",
"fossil",
"Polflucht",
"Earth",
"Eduard Suess",
"geodesy",
"continental crust",
"biogeography",
"Alfred Wegener"
] |
6,057 |
Commodores
|
Commodores, often billed as The Commodores, is an American funk and soul group. The group's most successful period was in the late 1970s and early 1980s when Lionel Richie was the co-lead singer.
The members of the group met as mostly freshmen at Tuskegee Institute (now Tuskegee University) in 1968, and signed with Motown in November 1972, having first caught the public eye opening for the Jackson 5 while on tour.
The band's biggest hit singles are ballads such as "Easy", "Three Times a Lady", and "Nightshift"; and funk-influenced dance songs, including "Brick House", "Fancy Dancer", "Lady (You Bring Me Up)", and "Too Hot ta Trot".
Commodores were inducted into the Alabama Music Hall of Fame and Vocal Group Hall of Fame. The new six-man band featured Lionel Richie, Thomas McClary, and William King from the Mystics, and Andre Callahan, Michael Gilbert, and Milan Williams from the Jays. They chose their present name when King flipped open a dictionary and ran his finger down the page. "We lucked out," he remarked with a laugh when telling this story to People magazine. "We almost became 'The Commodes.'"
The bandmembers attended Tuskegee University in Alabama. After winning the university's annual freshman talent contest, they played at fraternity parties as well as a weekend gig at the Black Forest Inn, one of a few clubs in Tuskegee that catered to college students. They performed cover tunes and some original songs with their first singer, James Ingram (not the famous solo artist). and is also heard in many films, including Boogie Nights and Looking for Mr. Goodbar. It reached No. 22 on the Billboard Hot 100 in 1974. Another 1974 song "I Feel Sanctified" has been called a "prototype" of Wild Cherry's 1976 big hit "Play That Funky Music". Of the three albums released in 1975 and 1976, Caught in the Act was funk album, but Movin' On and Hot on the Tracks were pop albums. After those recordings the group developed the mellower sound hinted at in their 1976 top-ten hits, "Sweet Love" and "Just to Be Close to You".
Founding member McClary left in 1984 (shortly after Richie) to pursue a solo career,
The group gradually abandoned its funk roots and moved into the more commercial pop arena. The Commodores were on a European tour performing at Wembley Arena, London, on June 25, 2009, when they walked off the stage after they were told that Michael Jackson had died. Initially the band thought it was a hoax. However, back in their dressing rooms they received confirmation and broke down in tears. The next night at Birmingham's NIA Arena, J.D. Nicholas added Jackson's name to the lyrics of the song, and henceforth the Commodores have mentioned Jackson and other deceased R&B singers. Thus came the inspiration upon the first anniversary of Jackson's death to re-record, with new lyrics, the hit song "Nightshift" as a tribute.
In 1990, they formed Commodores Records and re-recorded their 20 greatest hits as Commodores Hits Vol. I & II. They have recorded a live album, Commodores Live, along with a DVD of the same name, and a Christmas album titled Commodores Christmas. In 2012, the band was working on new material, with some contributions written by current and former members.
Commodores as of 2020 consist of Walter "Clyde" Orange, James Dean "J.D." Nicholas, and William "WAK" King, along with their five-piece band The Mean Machine.They continue to perform, playing at arenas, theaters, and festivals around the world.
==Personnel==
===Current members===
William "WAK" King – trumpet, guitar, keyboards, vocals (1968–present)
Walter Orange – vocals, drums (1972–present)
James Dean "J.D." Nicholas – vocals (1984–2024)
===Former members===
Lionel Richie – vocals, keyboards, saxophone (1968–82)
Milan Williams – keyboards, rhythm guitar (1968–89)
Thomas McClary – lead guitar, vocals (1968–83)
Andre Callahan – drums, vocals, keyboards (1968–70)
Michael Gilbert – bass guitar, trumpet (1968–70)
Eugene Ward – keyboards (1968–70)
Ronald LaPread – bass guitar (1970–86)
James Ingram – vocals, drums (1970–72)
Skyler Jett – vocals (1982–84)
Sheldon Reynolds – lead guitar (1983–87)
Mikael Manley – lead guitar (1995–2005)
Don Williams Sr - keyboards (1999–2001)
====Timeline====
==Discography==
Studio albums
Machine Gun (1974)
Caught in the Act (1975)
Movin' On (1975)
Hot on the Tracks (1976)
Commodores (1977)
Natural High (1978)
Midnight Magic (1979)
Heroes (1980)
In the Pocket (1981)
Commodores 13 (1983)
Nightshift (1985)
United (1986)
Rock Solid (1988)
No Tricks (1993)
==Accolades==
===Grammy awards===
The Commodores have won one Grammy Award out of ten nominations.
===Alabama Music Hall of Fame===
During 1995 the Commodores were inducted into the Alabama Music Hall of Fame.
===Vocal Group Hall of Fame===
During 2003 the Commodores were also inducted into the Vocal Group Hall of Fame.
|
[
"Hallandale, Florida",
"Tuskegee, Alabama",
"Lionel Richie",
"Funk",
"Alabama",
"Hot on the Tracks",
"Jackie Wilson",
"Grammy Award for Best Inspirational Performance",
"Just to Be Close to You",
"James Ingram",
"William King (singer)",
"Boogie Nights",
"Thomas McClary (musician)",
"Brick House (song)",
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"Birmingham",
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"Commodores 13",
"Still (Commodores song)",
"Wembley Arena",
"Alabama Music Hall of Fame",
"Guinness Publishing",
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"Tuskegee University",
"Midnight Magic (album)",
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"Too Hot ta Trot",
"Tom Joyner",
"Sheldon Reynolds (guitarist)",
"Lady (You Bring Me Up)",
"People (American magazine)",
"Encyclopedia of Popular Music",
"YouTube",
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"Commodores (album)",
"Three Times a Lady",
"Colin Larkin (writer)",
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"hit record",
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"Soul music",
"Barclaycard Arena",
"Vocal Group Hall of Fame",
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"Commodores Live",
"In the Pocket (Commodores album)",
"Easy (Commodores song)",
"London",
"sound recording and reproduction",
"Grammy Award",
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"Natural High (Commodores album)",
"Nightshift (song)",
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"Milan Williams",
"Heatwave (band)",
"concert tour",
"No Tricks",
"freshmen",
"Movin' On (Commodores album)",
"Rhythm and blues",
"Thank God It's Friday (film)",
"Heroes (Commodores album)",
"Pop music",
"Grammy Award for Best Pop Performance by a Duo or Group with Vocals"
] |
6,058 |
Collagen
|
Collagen () is the main structural protein in the extracellular matrix of the connective tissues of many animals. It is the most abundant protein in mammals, making up 25% to 35% of protein content. Amino acids are bound together to form a triple helix of elongated fibril known as a collagen helix. It is mostly found in cartilage, bones, tendons, ligaments, and skin. Vitamin C is vital for collagen synthesis.
Depending on the degree of mineralization, collagen tissues may be rigid (bone) or compliant (tendon) or have a gradient from rigid to compliant (cartilage). Collagen is also abundant in corneas, blood vessels, the gut, intervertebral discs, and the dentin in teeth. In muscle tissue, it serves as a major component of the endomysium. Collagen constitutes 1% to 2% of muscle tissue and 6% by weight of skeletal muscle. The fibroblast is the most common cell creating collagen in animals. Gelatin, which is used in food and industry, is collagen that was irreversibly hydrolyzed using heat, basic solutions, or weak acids.
==Etymology==
The name collagen comes from the Greek κόλλα (kólla), meaning "glue", and suffix -γέν, -gen, denoting "producing".
==Types==
As of 2011, 28 types of human collagen have been identified, described, and classified according to their structure. This diversity shows collagen's diverse functionality. All of the types contain at least one triple helix.
Fibrillar (type I, II, III, V, XI)
Non-fibrillar
FACIT (fibril-associated collagens with interrupted triple helices) (types IX, XII, XIV, XIX, XXI)
Short-chain (types VIII, X)
Basement membrane (type IV)
Multiplexin (multiple triple helix domains with interruptions) (types XV, XVIII)
MACIT (membrane-associated collagens with interrupted triple helices) (types XIII, XVII)
Microfibril-forming (type VI)
Anchoring fibrils (type VII)
The five most common types are:
Type I: skin, tendon, vasculature, organs, bone (main component of the organic part of bone)
Type II: cartilage (main collagenous component of cartilage)
Type III: reticulate (main component of reticular fibers), commonly found alongside type I
Type IV: forms basal lamina, the epithelium-secreted layer of the basement membrane
Type V: cell surfaces, hair, and placenta
==In humans==
===Cardiac===
The collagenous cardiac skeleton, which includes the four heart valve rings, is histologically, elastically and uniquely bound to cardiac muscle. The cardiac skeleton also includes the separating septa of the heart chambers – the interventricular septum and the atrioventricular septum. Collagen contribution to the measure of cardiac performance summarily represents a continuous torsional force opposed to the fluid mechanics of blood pressure emitted from the heart. The collagenous structure that divides the upper chambers of the heart from the lower chambers is an impermeable membrane that excludes both blood and electrical impulses through typical physiological means. With support from collagen, atrial fibrillation never deteriorates to ventricular fibrillation. Collagen is layered in variable densities with smooth muscle mass. The mass, distribution, age, and density of collagen all contribute to the compliance required to move blood back and forth. Individual cardiac valvular leaflets are folded into shape by specialized collagen under variable pressure. Gradual calcium deposition within collagen occurs as a natural function of aging. Calcified points within collagen matrices show contrast in a moving display of blood and muscle, enabling methods of cardiac imaging technology to arrive at ratios essentially stating blood in (cardiac input) and blood out (cardiac output). Pathology of the collagen underpinning of the heart is understood within the category of connective tissue disease.
===Bone grafts===
As the skeleton forms the structure of the body, it is vital that it maintains its strength, even after breaks and injuries. Collagen is used in bone grafting because its triple-helix structure makes it a very strong molecule. It is ideal for use in bones, as it does not compromise the structural integrity of the skeleton. The triple helical structure prevents collagen from being broken down by enzymes, it enables adhesiveness of cells and it is important for the proper assembly of the extracellular matrix.
===Tissue regeneration===
Collagen scaffolds are used in tissue regeneration, whether in sponges, thin sheets, gels, or fibers. Collagen has favorable properties for tissue regeneration, such as pore structure, permeability, hydrophilicity, and stability in vivo. Collagen scaffolds also support deposition of cells, such as osteoblasts and fibroblasts, and once inserted, facilitate growth to proceed normally.
===Reconstructive surgery===
Collagens are widely used in the construction of artificial skin substitutes used for managing severe burns and wounds. These collagens may be derived from cow, horse, pig, or even human sources; and are sometimes used in combination with silicones, glycosaminoglycans, fibroblasts, growth factors and other substances.
=== Wound healing ===
Collagen is one of the body's key natural resources and a component of skin tissue that can benefit all stages of wound healing. When collagen is made available to the wound bed, closure can occur. This avoids wound deterioration and procedures such as amputation.
Collagen is used as a natural wound dressing because it has properties that artificial wound dressings do not have. It resists bacteria, which is vitally important in wound dressing. As a burn dressing, collagen helps it heal fast by helping granulation tissue to grow over the burn. Collagen is also widely used as a bioink for 3D bioprinting and biofabrication of 3D tissue models.
==Biology==
The collagen protein is composed of a triple helix, which generally consists of two identical chains (α1) and an additional chain that differs slightly in its chemical composition (α2). The amino acid composition of collagen is atypical for proteins, particularly with respect to its high hydroxyproline content. The most common motifs in collagen's amino acid sequence are glycine-proline-X and glycine-X-hydroxyproline, where X is any amino acid other than glycine, proline or hydroxyproline.
The table below lists average amino acid composition for fish and mammal skin.
==Synthesis==
First, a three-dimensional stranded structure is assembled, mostly composed of the amino acids glycine and proline. This is the collagen precursor procollagen. Then, procollagen is modified by the addition of hydroxyl groups to the amino acids proline and lysine. This step is important for later glycosylation and the formation of collagen's triple helix structure. Because the hydroxylase enzymes performing these reactions require vitamin C as a cofactor, a long-term deficiency in this vitamin results in impaired collagen synthesis and scurvy. These hydroxylation reactions are catalyzed by the enzymes prolyl 4-hydroxylase and lysyl hydroxylase. The reaction consumes one ascorbate molecule per hydroxylation. Collagen synthesis occurs inside and outside cells.
The most common form of collagen is fibrillary collagen. Another common form is meshwork collagen, which is often involved in the formation of filtration systems. All types of collagen are triple helices, but differ in the make-up of their alpha peptides created in step 2. Below we discuss the formation of fibrillary collagen.
Transcription of mRNA: Synthesis begins with turning on genes associated with the formation of a particular alpha peptide (typically alpha 1, 2 or 3). About 44 genes are associated with collagen formation, each coding for a specific mRNA sequence, and are typically named with the "COL" prefix.
Pre-pro-peptide formation: The created mRNA exits the cell nucleus into the cytoplasm. There, it links with the ribosomal subunits and is translated into a peptide. The peptide goes into the endoplasmic reticulum for post-translational processing. It is directed there by a signal recognition particle on the endoplasmic reticulum, which recognizes the peptide's signal sequence (the early part of the sequence). The processed product is a pre-pro-peptide called preprocollagen.
Pro-collagen formation: Three modifications of the pre-pro-peptide form the alpha peptide:
The signal peptide on the N-terminal is removed. The molecule is now called propeptide.
Lysines and prolines are hydroxylated by the enzymes 'prolyl hydroxylase' and 'lysyl hydroxylase', producing hydroxyproline and hydroxylysine. This helps in cross-linking the alpha peptides. This enzymatic step requires vitamin C as a cofactor. In scurvy, the lack of hydroxylation of prolines and lysines causes a looser triple helix (which is formed by three alpha peptides).
Glycosylation occurs by adding either glucose or galactose monomers onto the hydroxyl groups that were placed onto lysines, but not on prolines.
Three of the hydroxylated and glycosylated propeptides twist into a triple helix (except for its ends), forming procollagen. It is packaged into a transfer vesicle destined for the Golgi apparatus.
Modification and secretion: In the Golgi apparatus, the procollagen goes through one last post-translational modification, adding oligosaccharides (not monosaccharides as in step 3). Then it is packaged into a secretory vesicle to be secreted from the cell.
Tropocollagen formation: Outside the cell, membrane-bound enzymes called collagen peptidases remove the unwound ends of the molecule, producing tropocollagen. Defects in this step produce various collagenopathies called Ehlers–Danlos syndrome. This step is absent when synthesizing type III, a type of fibrillar collagen.
Collagen fibril formation: Lysyl oxidase, a copper-dependent enzyme, acts on lysines and hydroxylysines, producing aldehyde groups, which eventually form covalent bonds between tropocollagen molecules. This polymer of tropocollagen is called a collagen fibril.
===Amino acids===
Collagen has an unusual amino acid composition and sequence:
Glycine is found at almost every third residue.
Proline makes up about 17% of collagen.
Collagen contains two unusual derivative amino acids not directly inserted during translation. These amino acids are found at specific locations relative to glycine and are modified post-translationally by different enzymes, both of which require vitamin C as a cofactor.
Hydroxyproline derived from proline
Hydroxylysine derived from lysine – depending on the type of collagen, varying numbers of hydroxylysines are glycosylated (mostly having disaccharides attached).
Cortisol stimulates degradation of (skin) collagen into amino acids.
=== Collagen I formation ===
Most collagen forms in a similar manner, but the following process is typical for type I:
Inside the cell
Two types of alpha chains – alpha-1 and alpha 2, are formed during translation on ribosomes along the rough endoplasmic reticulum (RER). These peptide chains known as preprocollagen, have registration peptides on each end and a signal peptide.
Polypeptide chains are released into the lumen of the RER.
Signal peptides are cleaved inside the RER and the chains are now known as pro-alpha chains.
Hydroxylation of lysine and proline amino acids occurs inside the lumen. This process is dependent on and consumes ascorbic acid (vitamin C) as a cofactor.
Glycosylation of specific hydroxylysine residues occurs.
Triple alpha helical structure is formed inside the endoplasmic reticulum from two alpha-1 chains and one alpha-2 chain.
Procollagen is shipped to the Golgi apparatus, where it is packaged and secreted into extracellular space by exocytosis.
Outside the cell
Registration peptides are cleaved and tropocollagen is formed by procollagen peptidase.
Multiple tropocollagen molecules form collagen fibrils, via covalent cross-linking (aldol reaction) by lysyl oxidase which links hydroxylysine and lysine residues. Multiple collagen fibrils form into collagen fibers.
Collagen may be attached to cell membranes via several types of protein, including fibronectin, laminin, fibulin and integrin.
==Molecular structure==
A single collagen molecule, tropocollagen, is used to make up larger collagen aggregates, such as fibrils. It is approximately 300 nm long and 1.5 nm in diameter, and it is made up of three polypeptide strands (called alpha peptides, see step 2), each of which has the conformation of a left-handed helix – this should not be confused with the right-handed alpha helix. These three left-handed helices are twisted together into a right-handed triple helix or "super helix", a cooperative quaternary structure stabilized by many hydrogen bonds. With type I collagen and possibly all fibrillar collagens, if not all collagens, each triple-helix associates into a right-handed super-super-coil referred to as the collagen microfibril. Each microfibril is interdigitated with its neighboring microfibrils to a degree that might suggest they are individually unstable, although within collagen fibrils, they are so well ordered as to be crystalline.
A distinctive feature of collagen is the regular arrangement of amino acids in each of the three chains of these collagen subunits. The sequence often follows the pattern Gly-Pro-X or Gly-X-Hyp, where X may be any of various other amino acid residues. Additional assembly of fibrils is guided by fibroblasts, which deposit fully formed fibrils from fibripositors. In the fibrillar collagens, molecules are staggered to adjacent molecules by about 67 nm (a unit that is referred to as 'D' and changes depending upon the hydration state of the aggregate). In each D-period repeat of the microfibril, there is a part containing five molecules in cross-section, called the "overlap", and a part containing only four molecules, called the "gap". Larger fibrillar bundles are formed with the aid of several different classes of proteins (including different collagen types), glycoproteins, and proteoglycans to form the different types of mature tissues from alternate combinations of the same key players. These later advances are particularly important to better understanding the way in which collagen structure affects cell–cell and cell–matrix communication and how tissues are constructed in growth and repair and changed in development and disease. For example, using AFM–based nanoindentation it has been shown that a single collagen fibril is a heterogeneous material along its axial direction with significantly different mechanical properties in its gap and overlap regions, correlating with its different molecular organizations in these two regions.
Collagen fibrils/aggregates are arranged in different combinations and concentrations in various tissues to provide varying tissue properties. In bone, entire collagen triple helices lie in a parallel, staggered array. 40 nm gaps between the ends of the tropocollagen subunits (approximately equal to the gap region) probably serve as nucleation sites for the deposition of long, hard, fine crystals of the mineral component, which is hydroxylapatite (approximately) Ca10(OH)2(PO4)6. Type I collagen gives bone its tensile strength.
==Associated disorders==
Collagen-related diseases most commonly arise from genetic defects or nutritional deficiencies that affect the biosynthesis, assembly, posttranslational modification, secretion, or other processes involved in normal collagen production.
In addition to the above-mentioned disorders, excessive deposition of collagen occurs in scleroderma.
==Diseases==
One thousand mutations have been identified in 12 out of more than 20 types of collagen. These mutations can lead to various diseases at the tissue level.
Osteogenesis imperfecta – Caused by a mutation in type 1 collagen, dominant autosomal disorder, results in weak bones and irregular connective tissue, some cases can be mild while others can be lethal. Mild cases have lowered levels of collagen type 1 while severe cases have structural defects in collagen.
Chondrodysplasias – Skeletal disorder believed to be caused by a mutation in type 2 collagen, further research is being conducted to confirm this.
Ehlers–Danlos syndrome – Thirteen different types of this disorder, which lead to deformities in connective tissue, are known. Some of the rarer types can be lethal, leading to the rupture of arteries. Each syndrome is caused by a different mutation. For example, the vascular type (vEDS) of this disorder is caused by a mutation in collagen type 3.
Alport syndrome – Can be passed on genetically, usually as X-linked dominant, but also as both an autosomal dominant and autosomal recessive disorder, those with the condition have problems with their kidneys and eyes, loss of hearing can also develop during the childhood or adolescent years.
Knobloch syndrome – Caused by a mutation in the COL18A1 gene that codes for the production of collagen XVIII. Patients present with protrusion of the brain tissue and degeneration of the retina; an individual who has family members with the disorder is at an increased risk of developing it themselves since there is a hereditary link.
==Characteristics==
Collagen is one of the long, fibrous structural proteins whose functions are quite different from those of globular proteins, such as enzymes. Tough bundles of collagen called collagen fibers are a major component of the extracellular matrix that supports most tissues and gives cells structure from the outside, but collagen is also found inside certain cells. Collagen has great tensile strength, and is the main component of fascia, cartilage, ligaments, tendons, bone and skin. Along with elastin and soft keratin, it is responsible for skin strength and elasticity, and its degradation leads to wrinkles that accompany aging. It strengthens blood vessels and plays a role in tissue development. It is present in the cornea and lens of the eye in crystalline form. It may be one of the most abundant proteins in the fossil record, given that it appears to fossilize frequently, even in bones from the Mesozoic and Paleozoic.
=== Mechanical properties ===
Collagen is a complex hierarchical material with mechanical properties that vary significantly across different scales.
On the molecular scale, atomistic and course-grained modeling simulations, as well as numerous experimental methods, have led to several estimates of the Young's modulus of collagen at the molecular level. Only above a certain strain rate is there a strong relationship between elastic modulus and strain rate, possibly due to the large number of atoms in a collagen molecule. The length of the molecule is also important, where longer molecules have lower tensile strengths than shorter ones due to short molecules having a large proportion of hydrogen bonds being broken and reformed.
On the fibrillar scale, collagen has a lower modulus compared to the molecular scale, and varies depending on geometry, scale of observation, deformation state, and hydration level.
Limited tests have been done on the tensile strength of the collagen fiber, but generally it has been shown to have a lower Young's modulus compared to fibrils.
When studying the mechanical properties of collagen, tendon is often chosen as the ideal material because it is close to a pure and aligned collagen structure. However, at the macro, tissue scale, the vast number of structures that collagen fibers and fibrils can be arranged into results in highly variable properties. For example, tendon has primarily parallel fibers, whereas skin consists of a net of wavy fibers, resulting in a much higher strength and lower ductility in tendon compared to skin. The mechanical properties of collagen at multiple hierarchical levels is given.
{| class="wikitable"
|+Young's Modulus of Collagen at Multiple Hierarchical Levels
!Hierarchical Level
!Young's Modulus
|-
|Molecular (via atomistic modeling)
|2.4-7 GPa
|-
|Fibril
|0.2-0.8 GPa
|-
|Fiber (measured from cross-linked rat tail tendon)
|1.10 GPa
|-
|Fiber (measured from non-cross-linked rat tail tendon)
|50-250 MPa
===Uses===
Collagen has a wide variety of applications. In the medical industry, it is used in cosmetic surgery and burn surgery. An example of collagen use for food manufacturing is in casings for sausages.
If collagen is subject to sufficient denaturation, such as by heating, the three tropocollagen strands separate partially or completely into globular domains, containing a different secondary structure to the normal collagen polyproline II (PPII) of random coils. This process describes the formation of gelatin, which is used in many foods, including flavored gelatin desserts. Besides food, gelatin has been used in pharmaceutical, cosmetic, and photography industries. It is also used as a dietary supplement, and has been advertised as a potential remedy against the ageing process.
From the Greek for glue, kolla, the word collagen means "glue producer" and refers to the early process of boiling the skin and sinews of horses and other animals to obtain glue. Collagen adhesive was used by Egyptians about 4,000 years ago, and Native Americans used it in bows about 1,500 years ago. The oldest glue in the world, carbon-dated as more than 8,000 years old, was found to be collagen – used as a protective lining on rope baskets and embroidered fabrics, to hold utensils together, and in crisscross decorations on human skulls. Collagen normally converts to gelatin, but survived due to dry conditions. Animal glues are thermoplastic, softening again upon reheating, so they are still used in making musical instruments such as fine violins and guitars, which may have to be reopened for repairs – an application incompatible with tough, synthetic plastic adhesives, which are permanent. Animal sinews and skins, including leather, have been used to make useful articles for millennia.
Gelatin-resorcinol-formaldehyde glue (and with formaldehyde replaced by less-toxic pentanedial and ethanedial) has been used to repair experimental incisions in rabbit lungs.
=== Cosmetics ===
Bovine collagen is widely used in dermal fillers for aesthetic correction of wrinkles and skin aging. Collagen cremes are also widely sold even though collagen cannot penetrate the skin because its fibers are too large. Collagen is a vital protein in skin, hair, nails, and other tissues. Its production decreases with age and factors like sun damage and smoking. Collagen supplements, derived from sources like fish and cattle, are marketed to improve skin, hair, and nails. Studies show some skin benefits, but these supplements often contain other beneficial ingredients, making it unclear if collagen alone is effective. There's minimal evidence supporting collagen's benefits for hair and nails. Overall, the effectiveness of oral collagen supplements is not well-proven, and focusing on a healthy lifestyle and proven skincare methods like sun protection is recommended.
==History==
The molecular and packing structures of collagen eluded scientists over decades of research. The first evidence that it possesses a regular structure at the molecular level was presented in the mid-1930s. Research then concentrated on the conformation of the collagen monomer, producing several competing models, although correctly dealing with the conformation of each individual peptide chain. The triple-helical "Madras" model, proposed by G. N. Ramachandran in 1955, provided an accurate model of quaternary structure in collagen. This model was supported by further studies of higher resolution in the late 20th century.
The packing structure of collagen has not been defined to the same degree outside of the fibrillar collagen types, although it has been long known to be hexagonal. As with its monomeric structure, several conflicting models propose either that the packing arrangement of collagen molecules is 'sheet-like', or is microfibrillar. The microfibrillar structure of collagen fibrils in tendon, cornea and cartilage was imaged directly by electron microscopy in the late 20th century and early 21st century. The microfibrillar structure of rat tail tendon was modeled as being closest to the observed structure, although it oversimplified the topological progression of neighboring collagen molecules, and so did not predict the correct conformation of the discontinuous D-periodic pentameric arrangement termed microfibril.
|
[
"Phenylalanine",
"silicone",
"glycosylation",
"Nucleation",
"Glycine",
"Histidine",
"Glutamic acid",
"soluble",
"denaturation (biochemistry)",
"cardiac output",
"nephron",
"Aspartic acid",
"Coarse-grained modeling",
"endostatin",
"Chondrodysplasia",
"dermal filler",
"gelatin dessert",
"Amide hydrolysis",
"COL24A1",
"collagen fibers",
"kidney",
"Gut (anatomy)",
"hydroxylase",
"disaccharide",
"Hyaline cartilage",
"burn (injury)",
"globular protein",
"COL17A1",
"cattle",
"Tyrosine",
"protein",
"capillaries",
"COL8A1",
"Hydroxyproline",
"radiocarbon dating",
"reticular fiber",
"glycine",
"Copper in health",
"Collagen loss",
"Collagenopathy, types II and XI",
"Bovine",
"skin",
"wikt:κόλλα",
"lung",
"Young's modulus",
"signal recognition particle",
"Posterior polymorphous corneal dystrophy 2",
"covalent bond",
"compliance (physiology)",
"Type-III collagen",
"COL7A1",
"granulation tissue",
"Cross-link",
"glyoxal",
"Serine",
"electron microscopy",
"casing (sausage)",
"ascorbic acid",
"extracellular matrix",
"fibulin",
"wound healing",
"Type-II collagen",
"placenta",
"prolyl 4-hydroxylase",
"scleroderma",
"amino",
"endoplasmic reticulum",
"Cortisol",
"Knobloch syndrome",
"Aesthetics",
"Gelatin",
"Type I collagen",
"COL12A1",
"intervertebral disc",
"musical instrument",
"COL6A2",
"random coil",
"embroidery",
"Anchoring fibrils",
"Protein precursor",
"COL4A4",
"residue (biochemistry)",
"eye lens",
"calcium",
"resorcinol",
"ventricular fibrillation",
"Residue (biochemistry)",
"Antihemorrhagic",
"cross-link",
"COL4A3",
"hydrogen",
"Reticular fiber",
"enzyme",
"Type XVIII collagen",
"EDM2",
"biofabrication",
"Threonine",
"COL2A1",
"smoking",
"COL4A6",
"EDM3",
"rough endoplasmic reticulum",
"COL27A1",
"COL6A5",
"COL14A1",
"EMID2",
"Ulrich myopathy",
"COL1A1",
"cornea",
"fibril",
"COL16A1",
"procollagen peptidase",
"thermoregulation",
"monomer",
"keratin",
"COL1A2",
"Bullous pemphigoid",
"biomineralization",
"FACIT collagen",
"atrioventricular septum",
"poikilothermic",
"3D bioprinting",
"polypeptide",
"human body",
"COL25A1",
"Cardiac stress test",
"lysyl oxidase",
"biological tissue",
"skeletal muscle",
"nanometre",
"chemical synthesis",
"Vitamin C",
"Journal of the American Chemical Society",
"bow (weapon)",
"artificial skin",
"connective tissue disease",
"Arginine",
"basic research",
"vitamin C",
"gelatin",
"Collagen hybridizing peptide",
"formaldehyde",
"COL18A1",
"collagen helix",
"Collagen, type IV, alpha 1",
"Type II collagen",
"Collagen, type XXIII, alpha 1",
"atopic dermatitis",
"COL6A1",
"Collagen XVII",
"scar",
"cardiac input",
"growth factor",
"Type-I collagen",
"Chemotaxis",
"COL9A2",
"Alanine",
"plastic surgery",
"wrinkle",
"tensile strength",
"Cofactor (biochemistry)",
"N-terminal",
"wikt:interdigitate",
"Alport syndrome",
"crystal",
"molecular self-assembly",
"COL21A1",
"COL5A3",
"Nail (anatomy)",
"Basal lamina",
"Hypermobility spectrum disorder",
"COL9A3",
"extracellular fluid",
"dermoepidermal junction",
"quaternary structure",
"Basement membrane",
"Lysyl oxidase",
"protein subunit",
"COL22A1",
"carboxyl",
"fascia",
"integrin",
"Golgi apparatus",
"Tryptophan",
"signal peptide",
"Glomerulus (kidney)",
"alpha helix",
"fibroblast",
"COL20A1",
"Isoleucine",
"G. N. Ramachandran",
"Paleozoic",
"Hydroxylysine",
"heart valve",
"fish",
"Osteogenesis imperfecta",
"COL3A1",
"COL6A3",
"Methionine",
"Procollagen",
"proline",
"exocytosis",
"basement membrane",
"COL15A1",
"Mesozoic",
"cofactor (biochemistry)",
"human skull",
"helix",
"dentin",
"osteoblasts",
"Hypertrophic",
"interventricular septum",
"Textile",
"type I & III collagen",
"lysine",
"pressure",
"fibroin",
"Metalloprotease inhibitor",
"Valine",
"anchoring fibril",
"Sunscreen",
"COL28A1",
"cardiac skeleton",
"Type IV collagen",
"Multiplexin",
"cardiac imaging",
"COL11A1",
"connective tissue",
"COL5A2",
"COL10A1",
"COL9A1",
"microfibril",
"perlecan",
"extracellular",
"hydrogen bond",
"International Journal of Biological Macromolecules",
"Proline",
"Type-V collagen",
"atrial fibrillation",
"ligament",
"cardiac septa",
"Ehlers–Danlos syndrome",
"Mineralization (biology)",
"Collagen, type III, alpha 1",
"Molecular dynamics",
"animal glue",
"list of eating utensils",
"Hydroxylation",
"COL8A2",
"Type-IV collagen",
"COL11A2",
"rat",
"Osteoid",
"aging",
"COL13A1",
"decorin",
"fibronectin",
"Cysteine",
"Schmid metaphyseal dysplasia",
"platelet",
"Bethlem myopathy",
"fibrous protein",
"tendon",
"hydrolyzed",
"cartilage",
"fluid mechanics",
"muscle tissue",
"Lysine",
"aldol reaction",
"triple helix",
"elastin",
"hair",
"scurvy",
"glue",
"Glycosylation",
"cell culture",
"blood vessel",
"Clearcutting",
"healthy lifestyle",
"thermoplastic",
"nidogen",
"Nanometre",
"COL19A1",
"healing",
"Epidermolysis bullosa dystrophica",
"COL23A1",
"Bio-ink",
"Collagen disease",
"mechanical properties",
"dietary supplement",
"hydroxyl",
"Goodpasture's syndrome",
"bone",
"COL5A1",
"epidermolysis bullosa",
"Vitreous humour",
"endothelium",
"COL4A5",
"lysyl hydroxylase",
"translation (genetics)",
"laminin",
"Dupuytren's contracture",
"Leucine",
"endomysium",
"COL4A2",
"Amino acid",
"glycosaminoglycan",
"hydroxyproline",
"infantile cortical hyperostosis"
] |
6,059 |
Calvin and Hobbes
|
{{Infobox comic strip
|title= Calvin and Hobbes
|image= Calvin and Hobbes Original.png
|caption= The cover of Calvin and Hobbes, the first collection of comic strips, released in April 1987.
|author = Bill Watterson
|syndicate= Universal Press Syndicate
|publisher= Andrews McMeel Publishing
|first= November 18, 1985 Calvin and Hobbes has enjoyed enduring popularity, influence, and academic and even a philosophical interest.
Calvin and Hobbes follows the humorous antics of the title characters: Calvin, a mischievous and adventurous six-year-old boy; and his friend Hobbes, a sardonic tiger. Set in the suburban United States of the 1980s and 1990s, the strip depicts Calvin's frequent flights of fancy and friendship with Hobbes. It also examines Calvin's relationships with his long-suffering parents and with his classmates, especially his neighbor Susie Derkins. Hobbes's dual nature is a defining motif for the strip: to Calvin, Hobbes is a living anthropomorphic tiger, while all the other characters seem to see Hobbes as an inanimate stuffed toy, though Watterson has not clarified exactly how Hobbes is perceived by others, or whether he is real or an imaginary friend. Though the series does not frequently mention specific political figures or ongoing events, it does explore broad issues like environmentalism, public education, and philosophical quandaries.
At the height of its popularity, Calvin and Hobbes was featured in over 2,400 newspapers worldwide. In 2010, reruns of the strip appeared in more than 50 countries, and nearly 45 million copies of the Calvin and Hobbes books have been sold worldwide. began devoting his spare time to developing a newspaper comic for potential syndication. He explored various strip ideas but all were rejected by the syndicates. United Feature Syndicate finally responded positively to one strip called The Doghouse, which featured a side character (the main character's little brother) who had a stuffed tiger. United identified these characters as the strongest and encouraged Watterson to develop them as the center of their own strip. Though United Feature ultimately rejected the new strip as lacking in marketing potential, Universal Press Syndicate took it up.
=== Launch and early success (1985–1990) ===
The first Calvin and Hobbes strip was published on November 18, 1985
Although Calvin and Hobbes underwent continual artistic development and creative innovation over the period of syndication, the earliest strips demonstrated a remarkable consistency with the latest. Watterson introduced all the major characters within the first three weeks and made no changes to the central cast over the strip's 10-year history.
By April 5, 1987, Watterson was featured in an article in the Los Angeles Times. Calvin and Hobbes has also won several more awards.
As his creation grew in popularity, there was strong interest from the syndicate to merchandise the characters and expand into other forms of media. Watterson's contract with the syndicate allowed the characters to be licensed without the creator's consent, as was standard at the time. Nevertheless, Watterson had leverage by threatening to simply walk away from the comic strip.
This dynamic played out in a long and emotionally draining battle between Watterson and his syndicate editors. By 1991, Watterson had achieved his goal of securing a new contract that granted him legal control over his creation and all future licensing arrangements.
=== Creative control (1991–1995) ===
Having achieved his objective of creative control, Watterson's desire for privacy subsequently reasserted itself and he ceased all media interviews, relocated to New Mexico, and largely disappeared from public engagements, refusing to attend the ceremonies of any of the cartooning awards he won. Watterson returned to the strip in 1992 with plans to produce his Sunday strip as an unbreakable half of a newspaper or tabloid page. This made him only the second cartoonist since Garry Trudeau to have sufficient popularity to demand more space and control over the presentation of his work.
Watterson took a second sabbatical from April 3 through December 31, 1994. His return came with an announcement that Calvin and Hobbes would be concluding at the end of 1995. Stating his belief that he had achieved everything that he wanted to within the medium, he announced his intention to work on future projects at a slower pace with fewer artistic compromises.
Speaking to NPR in 2005, animation critic Charles Solomon opined that the final strip "left behind a hole in the comics page that no strip has been able to fill."
==Sunday formatting==
Syndicated comics were typically published six times a week in black and white, with a Sunday supplement version in a larger, full color format. This larger format version of the strip was constrained by mandatory layout requirements that made it possible for newspaper editors to format the strip for different page sizes and layouts.
Watterson grew increasingly frustrated by the shrinking of the available space for comics in the newspapers and the mandatory panel divisions that restricted his ability to produce better artwork and more creative storytelling. He felt that without space for anything more than simple dialogue or sparse artwork, comics as an art form were becoming dilute, bland, and unoriginal.
Watterson longed for the artistic freedom allotted to classic strips such as Little Nemo and Krazy Kat, and in 1989 he gave a sample of what could be accomplished with such liberty in the opening pages of the Sunday strip compilation, The Calvin and Hobbes Lazy Sunday Book—an 8-page previously unpublished Calvin story fully illustrated in watercolor. The same book contained an afterword from the artist himself, reflecting on a time when comic strips were allocated a whole page of the newspaper and every comic was like a "color poster".
Within two years, Watterson was ultimately successful in negotiating a deal that provided him more space and creative freedom. Following his 1991 sabbatical, Universal Press announced that Watterson had decided to sell his Sunday strip as an unbreakable half of a newspaper or tabloid page. Many editors and even a few cartoonists including Bil Keane (The Family Circus) and Bruce Beattie (Snafu) criticized him for what they perceived as arrogance and an unwillingness to abide by the normal practices of the cartoon business. Others, including Bill Amend (Foxtrot), Johnny Hart (BC, Wizard of Id) and Barbara Brandon (Where I'm Coming From) supported him. The American Association of Sunday and Feature Editors even formally requested that Universal reconsider the changes. Watterson's own comments on the matter was that "editors will have to judge for themselves whether or not Calvin and Hobbes deserves the extra space. If they don't think the strip carries its own weight, they don't have to run it." Ultimately only 15 newspapers cancelled the strip in response to the layout changes.
==Sabbaticals==
Bill Watterson took two sabbaticals from the daily requirements of producing the strip. The first took place from May 5, 1991, to February 1, 1992, and the second from April 3 through December 31, 1994. These sabbaticals were included in the new contract Watterson managed to negotiate with Universal Features in 1990. The sabbaticals were proposed by the syndicate themselves, who, fearing Watterson's complete burnout, endeavored to get another five years of work from their star artist.
==Merchandising==
Calvin and Hobbes had almost no official product merchandising. Watterson held that comic strips should stand on their own as an art form and although he did not start out completely opposed to merchandising in all forms (or even for all comic strips), he did reject an early syndication deal that involved incorporating a more marketable, licensed character into his strip. Almost no legitimate Calvin and Hobbes merchandise exists. Exceptions produced during the strip's original run include two 16-month calendars (1988–89 and 1989–90), a t-shirt for the Smithsonian Exhibit, Great American Comics: 100 Years of Cartoon Art (1990) and the textbook Teaching with Calvin and Hobbes, which has been described as "perhaps the most difficult piece of official Calvin and Hobbes memorabilia to find." In 2010, Watterson did allow his characters to be included in a series of United States Postal Service stamps honoring five classic American comics. Licensed prints of Calvin and Hobbes were made available and have also been included in various academic works.
The strip's immense popularity has led to the appearance of various counterfeit items such as window decals and T-shirts that often feature crude humor, binge drinking and other themes that are not found in Watterson's work. Images from one strip in which Calvin and Hobbes dance to loud music at night were commonly used for copyright violations. After threat of a lawsuit alleging infringement of copyright and trademark, some sticker makers replaced Calvin with a different boy, while other makers made no changes. Watterson wryly commented, "I clearly miscalculated how popular it would be to show Calvin urinating on a Ford logo,"
===Animation===
Watterson has expressed admiration for animation as an artform. In a 1989 interview in The Comics Journal he described the appeal of being able to do things with a moving image that cannot be done by a simple drawing: the distortion, the exaggeration and the control over the length of time an event is viewed. However, although the visual possibilities of animation appealed to Watterson, the idea of finding a voice for Calvin made him uncomfortable, as did the idea of working with a team of animators. Calls from major Hollywood figures interested in an adaptation of his work, including Jim Henson, George Lucas and Steven Spielberg, were never returned Schulz and Kelly particularly influenced Watterson's outlook on comics during his formative years. He also makes a point of not showing certain things explicitly: the "Noodle Incident" and the children's book Hamster Huey and the Gooey Kablooie are left to the reader's imagination, where Watterson was sure they would be "more outrageous" than he could portray.
== Production and technique ==
Watterson's technique started with minimalist pencil sketches drawn with a light pencil (though the larger Sunday strips often required more elaborate work) on a piece of Bristol board, with his brand of choice being Strathmore because he felt it held the drawings better on the page as opposed to the cheaper brands (Watterson said he initially used any cheap pad of Bristol board his local supply store had but switched to Strathmore after he found himself growing more and more displeased with the results). He would then use a small sable brush and India ink to fill in the rest of the drawing, saying that he did not want to simply trace over his penciling and thus make the inking more spontaneous. He lettered dialogue with a Rapidograph fountain pen, and he used a crowquill pen for odds and ends. Mistakes were covered with various forms of correction fluid, including the type used on typewriters. Watterson was careful in his use of color, often spending a great deal of time in choosing the right colors to employ for the weekly Sunday strip; his technique was to cut the color tabs the syndicate sent him into individual squares, lay out the colors, and then paint a watercolor approximation of the strip on tracing paper over the Bristol board and then mark the strip accordingly before sending it on. When Calvin and Hobbes began there were 64 colors available for the Sunday strips. For the later Sunday strips Watterson had 125 colors as well as the ability to fade the colors into each other. He begins exploring the medium of snow when a warm day melts his snowman. His next sculpture "speaks to the horror of our own mortality, inviting the viewer to contemplate the evanescence of life." In later strips, Calvin's creative instincts diversify to include sidewalk drawings (or, as he terms them, examples of "suburban postmodernism").
Watterson also lampooned the academic world. In one example, Calvin carefully crafts an "artist's statement", claiming that such essays convey more messages than artworks themselves ever do (Hobbes blandly notes, "You misspelled Weltanschauung"). He indulges in what Watterson calls "pop psychobabble" to justify his destructive rampages and shift blame to his parents, citing "toxic codependency." In one instance, he pens a book report based on the theory that the purpose of academic writing is to "inflate weak ideas, obscure poor reasoning and inhibit clarity," entitled The Dynamics of Interbeing and Monological Imperatives in Dick and Jane: A Study in Psychic Transrelational Gender Modes. Displaying his creation to Hobbes, he remarks, "Academia, here I come!" Watterson explains that he adapted this jargon (and similar examples from several other strips) from an actual book of art criticism.
Overall, Watterson's satirical essays serve to attack both sides, criticizing both the commercial mainstream and the artists who are supposed to be "outside" it. The strip on Sunday, June 21, 1992, criticized the naming of the Big Bang theory as not evocative of the wonders behind it and coined the term "Horrendous Space Kablooie", an alternative that achieved some informal popularity among scientists and was often shortened to "the HSK". The term has also been referred to in newspapers, books and university courses.
===Calvin's alter-egos===
Calvin imagines himself as many great creatures and other people, including dinosaurs, elephants, jungle-farers and superheroes. Three of his alter egos are well-defined and recurrent:
"Spaceman Spiff" is a heroic spacefarer who narrates his adventures in the third person. As Spiff, Calvin battles aliens (typically his parents or teacher, but also sometimes other kids his age) with a ray gun known as a "zorcher" (later "frap-ray blaster", "death ray blaster" or "atomic napalm neutralizer") and travels to distant planets (his house, school or neighborhood), often crashing unhurt on a planet. Calvin's self-narration as Spaceman Spiff is frequently riddled with alliteration: "Zounds! Zorched by Zarches, Spaceman Spiff's crippled craft crashes on planet Plootarg!" Watterson has stated the idea of Spaceman Spiff came from an earlier attempt as a cartoon, and is meant as a parody of Flash Gordon. The canyons and deserts that many of the Spaceman Spiff stories are set in are based on the landscapes of southern Utah.
"Tracer Bullet" is a hardboiled private eye, who says he has eight slugs in him ("One's lead, and the rest are bourbon."). In one story, Bullet is called to a case in which a "pushy dame" (Calvin's mother) accuses him of destroying an expensive lamp (broken during an indoor football game between Calvin and Hobbes). Later, he is snatched by the pushy dame's "hired goon" (Calvin's father having a talk with him). In another, he "investigates" a math word problem during class, "closing the case" with an answer of 1,000,000,000 when the correct response was 15. He made his debut when Calvin donned a fedora in order to hide a terrible haircut Hobbes had given him. These strips are drawn in elaborate, shadowy black-and-white that evoke film noir. Watterson did not attempt Tracer Bullet stories often, due to the time-consuming way the strip needed to be drawn and inked.
"Stupendous Man" is a superhero who wears a mask and a cape (made by Calvin's mother) and narrates his own adventures. While Calvin is in character as Stupendous Man, he refers to his alter ego as a mild-mannered millionaire playboy. Stupendous Man almost always "suffers defeat" at the hands of his opponent. When Hobbes asks if Stupendous Man has ever won any battles, Calvin says all his battles are "moral victories." Stupendous Man's nemeses include "Mom-Lady" (Calvin's mom), "Annoying Girl" (Susie Derkins), "Crab Teacher" (Miss Wormwood) and "Baby-Sitter Girl" (Rosalyn). Some of the "super powers" of the villains have been revealed: Mom-Lady has a "mind scrambling eyeball ray" that wills the victim to "do her nefarious bidding"; and Baby Sitter Girl has a similar power of using a "psycho beam" which weakens "Stupendous Man's stupendous will". The "powers" of Annoying Girl and Crab Teacher are never revealed. Calvin often tries to pretend he and "Stupendous Man" are two different people, but it fails to work. Stupendous Man has multiple "superpowers", including, but not limited to, super strength, the ability to fly, various vision powers such as "high-speed vision", "muscles of magnitude" and a "stomach of steel".
===Cardboard boxes===
Calvin also has several adventures involving corrugated cardboard boxes, which he adapts for many imaginative and elaborate uses. In one strip, when Calvin shows off his Transmogrifier, a device that transforms its user into any desired creature or item, Hobbes remarks, "It's amazing what they do with corrugated cardboard these days." Calvin is able to change the function of the boxes by rewriting the label and flipping the box onto another side. In this way, a box can be used not only for its conventional purposes (a storage container for water balloons, for example), but also as a flying time machine, a duplicator, a transmogrifier or, with the attachment of a few wires and a colander, a "Cerebral Enhance-o-tron."
In the real world, Calvin's antics with his box have had varying effects. When he transmogrified into a tiger, he still appeared as a regular human child to his parents. However, in a story where he made several duplicates of himself, his parents are seen interacting with what does seem like multiple Calvins, including in a strip where two of him are seen in the same panel as his father. It is ultimately unknown what his parents do or do not see, as Calvin tries to hide most of his creations (or conceal their effects) so as not to traumatize them.
In addition, Calvin uses a cardboard box as a sidewalk kiosk to sell things. Often, Calvin offers merchandise no one would want, such as "suicide drink", "a swift kick in the butt" for one dollar or a "frank appraisal of your looks" for fifty cents. In one strip, he sells "happiness" for ten cents, hitting the customer in the face with a water balloon and explaining that he meant his own happiness. In another strip, he sold "insurance", firing a slingshot at those who refused to buy it. In some strips, he tried to sell "great ideas" and, in one earlier strip, he attempted to sell the family car to obtain money for a grenade launcher. In yet another strip, he sells "life" for five cents, where the customer receives nothing in return, which, in Calvin's opinion, is life.
The box has also functioned as an alternate secret meeting place for G.R.O.S.S., as the "Box of Secrecy".
===Calvinball===
Calvinball is an improvisational sport/game introduced in a 1990 storyline that involved Calvin's negative experience of joining the school baseball team. Calvinball is a nomic or self-modifying game, a contest of wits, skill and creativity rather than stamina or athletic skill. The game is portrayed as a rebellion against conventional team sports and became a staple of the final five years of the comic. The only consistent rules of the game are that Calvinball may never be played with the same rules twice and that each participant must wear a mask.
When asked how to play, Watterson stated: "It's pretty simple: you make up the rules as you go." In most appearances of the game, a comical array of conventional and non-conventional sporting equipment is involved, including a croquet set, a badminton set, assorted flags, bags, signs, a hobby horse, water buckets and balloons, with humorous allusions to unseen elements such as "time-fracture wickets". Scoring is portrayed as arbitrary and nonsensical ("Q to 12" and "oogy to boogy") and the lack of fixed rules leads to lengthy argument between the participants as to who scored, where the boundaries are, and when the game is finished. Usually, the contest results in Calvin being outsmarted by Hobbes. The game has been described in one academic work not as a new game based on fragments of an older one, but as the "constant connecting and disconnecting of parts, the constant evasion of rules or guidelines based on collective creativity."
===Snowmen and other snow art===
Calvin often creates horrendous/dark humor scenes with his snowmen and other snow sculptures. He uses the snowman for social commentary, revenge or pure enjoyment. Examples include Snowman Calvin being yelled at by Snowman Dad to shovel the snow; one snowman eating snow cones scooped out of a second snowman, who is lying on the ground with an ice-cream scoop in his back; a "snowman house of horror"; and snowmen representing people he hates. "The ones I really hate are small, so they'll melt faster," he says. There was even an occasion on which Calvin accidentally brought a snowman to life and it made itself and a small army into "deranged mutant killer monster snow goons."
Calvin's snow art is often used as a commentary on art in general. For example, Calvin has complained more than once about the lack of originality in other people's snow art and compared it with his own grotesque snow sculptures. In one of these instances, Calvin and Hobbes claim to be the sole guardians of high culture; in another, Hobbes admires Calvin's willingness to put artistic integrity above marketability, causing Calvin to reconsider and make an ordinary snowman.
===Wagon and sled rides===
Calvin and Hobbes frequently ride downhill in a wagon or sled (depending on the season), as a device to add some physical comedy to the strip and because, according to Watterson, "it's a lot more interesting ... than talking heads." While the ride is sometimes the focus of the strip, it also frequently serves as a counterpoint or visual metaphor while Calvin ponders the meaning of life, death, God, philosophy or a variety of other weighty subjects. Many of their rides end in spectacular crashes which leave them battered, beaten up and broken, a fact which convinces Hobbes to sometimes hop off before a ride even begins. In the final strip, Calvin and Hobbes depart on their sled to go exploring.
===G.R.O.S.S. (Get Rid of Slimy GirlS) ===
G.R.O.S.S. (which is a backronym for Get Rid Of Slimy GirlS, "otherwise it doesn't spell anything") is a club in which Calvin and Hobbes are the only members. The club was founded in the garage of their house, but to clear space for its activities, Calvin and (purportedly) Hobbes push Calvin's parents' car, causing it to roll into a ditch (but not suffer damage); the incident prompts the duo to change the club's location to Calvin's treehouse. They hold meetings that involve finding ways to annoy and discomfort Susie Derkins, a girl and enemy of their club. Actions include planting a fake secret tape near her in attempt to draw her in to a trap, trapping her in a closet at their house and creating elaborate water balloon traps. Calvin gave himself and Hobbes important positions in the club, Calvin being "Dictator-for-Life" and Hobbes being "President-and-First-Tiger". They go into Calvin's treehouse for their club meetings and often get into fights during them. The password to get into the treehouse is intentionally long and difficult, which has on at least one occasion ruined Calvin's plans. As Hobbes is able to climb the tree without the rope, he is usually the one who comes up with the password, which often involves heaping praise upon tigers. An example of this can be seen in the comic strip where Calvin, rushing to get into the treehouse to throw things at a passing Susie Derkins, insults Hobbes, who is in the treehouse and thus has to let down the rope. Hobbes forces Calvin to say the password for insulting him. By the time Susie arrives, in time to hear Calvin saying some of the password, causing him to stumble, Calvin is on "Verse Seven: Tigers are perfect!/The E-pit-o-me/of good looks and grace/and quiet..uh..um..dignity". The opportunity to pelt Susie with something having passed, Calvin threatens to turn Hobbes into a rug.
=== Dinosaurs ===
Dinosaurs play a heavy role in many of Calvin's imagination sequences. These strips will often begin with hyper-realistic scenes of dinosaur interactions, only to end with a cut to Calvin acting out these scenes as part of a day-dream, often to his embarrassment. Watterson placed a heavy focus on accurately depicting dinosaurs, due to his own interest in them as well as to reinforce how real they are to Calvin.
==Books==
There are 18 Calvin and Hobbes books, published from 1987 to 1997. These include 11 collections, which form a complete archive of the newspaper strips, except for a single daily strip from November 28, 1985. (The collections do contain a strip for this date, but it is not the same strip that appeared in some newspapers.) Treasuries usually combine the two preceding collections with bonus material and include color reprints of Sunday comics.
Watterson included some new material in the treasuries. In The Essential Calvin and Hobbes, which includes cartoons from the collections Calvin and Hobbes and Something Under the Bed Is Drooling, the back cover features a scene of a giant Calvin rampaging through a town. The scene is based on Watterson's home town of Chagrin Falls, Ohio, and Calvin is holding the Chagrin Falls Popcorn Shop, an iconic candy and ice cream shop overlooking the town's namesake falls. Several of the treasuries incorporate additional poetry; The Indispensable Calvin and Hobbes book features a set of poems, ranging from just a few lines to an entire page, that cover topics such as Calvin's mother's "hindsight" and exploring the woods. In The Essential Calvin and Hobbes, Watterson presents a long poem explaining a night's battle against a monster from Calvin's perspective. The Authoritative Calvin and Hobbes includes a story based on Calvin's use of the Transmogrifier to finish his reading homework.
A complete collection of Calvin and Hobbes strips, in three hardcover volumes totaling 1440 pages, was released on October 4, 2005, by Andrews McMeel Publishing. It includes color prints of the art used on paperback covers, the treasuries' extra illustrated stories and poems and a new introduction by Bill Watterson in which he talks about his inspirations and his story leading up to the publication of the strip. The alternate 1985 strip is still omitted, and three other strips (January 7 and November 24, 1987, and November 25, 1988) have altered dialogue. A four-volume paperback version was released November 13, 2012.
To celebrate the release (which coincided with the strip's 20th anniversary and the tenth anniversary of its absence from newspapers), Bill Watterson answered 15 questions submitted by readers.
Early books were printed in smaller format in black and white. These were later reproduced in twos in color in the "Treasuries" (Essential, Authoritative and Indispensable), except for the contents of Attack of the Deranged Mutant Killer Monster Snow Goons. Those Sunday strips were not reprinted in color until the Complete collection was finally published in 2005.
Watterson claims he named the books the "Essential, Authoritative and Indispensable" because, as he says in The Calvin and Hobbes Tenth Anniversary Book, the books are "obviously none of these things." It has been called the "Holy Grail" for Calvin and Hobbes collectors.
==Reception==
Reviewing Calvin and Hobbes in 1990, Entertainment Weekly Ken Tucker gave the strip an A+ rating, writing "Watterson summons up the pain and confusion of childhood as much as he does its innocence and fun."
===Academic response===
In 1993, paleontologist and paleoartist Gregory S. Paul praised Bill Watterson for the scientific accuracy of the dinosaurs appearing in Calvin and Hobbes.
In her 1994 book When Toys Come Alive, Lois Rostow Kuznets theorizes that Hobbes serves both as a figure of Calvin's childish fantasy life and as an outlet for the expression of libidinous desires more associated with adults. Kuznets also analyzes Calvin's other fantasies, suggesting that they are a second tier of fantasies utilized in places like school where transitional objects such as Hobbes would not be socially acceptable.
Political scientist James Q. Wilson, in a paean to Calvin and Hobbes upon Watterson's decision to end the strip in 1995, characterized it as "our only popular explication of the moral philosophy of Aristotle."
A collection of original Sunday strips was exhibited at Ohio State University's Billy Ireland Cartoon Library & Museum in 2001. Watterson himself selected the strips and provided his own commentary for the exhibition catalog, which was later published by Andrews McMeel as Calvin and Hobbes: Sunday Pages 1985–1995. and the university-level philosophy reader Open Questions: Readings for Critical Thinking and Writing in 2005; in the latter, the ethical views of Watterson and his characters Calvin and Hobbes are discussed in relation to the views of professional philosophers. In a 2009 evaluation of the entire body of Calvin and Hobbes strips using grounded theory methodology, Christijan D. Draper found that: "Overall, Calvin and Hobbes suggests that meaningful time use is a key attribute of a life well lived," and that "the strip suggests one way to assess the meaning associated with time use is through preemptive retrospection by which a person looks at current experiences through the lens of an anticipated future..."
Calvin and Hobbes strips were again exhibited at the Billy Ireland Cartoon Library & Museum at The Ohio State University in 2014, in an exhibition entitled Exploring Calvin and Hobbes. An exhibition catalog by the same title, which also contained an interview with Watterson conducted by Jenny Robb, the curator of the museum, was published by Andrews McMeel in 2015.
==Legacy==
Years after its original newspaper run, Calvin and Hobbes has continued to exert influence in entertainment, art, and fandom.
In television, Calvin and Hobbes have been satirically depicted in stop motion animation in the 2006 and 2018 Robot Chicken episodes "Lust for Puppets" and "Jew No. 1 Opens a Treasure Chest" respectively, and in traditional animation in the 2009 Family Guy episode "Not All Dogs Go to Heaven." In the 2013 Community episode "Paranormal Parentage," the characters Abed Nadir (Danny Pudi) and Troy Barnes (Donald Glover) dress as Calvin and Hobbes, respectively, for Halloween.
British artists, merchandisers, booksellers, and philosophers were interviewed for a 2009 BBC Radio 4 half-hour programme about the abiding popularity of the comic strip, narrated by Phill Jupitus.
The first book-length study of the strip, Looking for Calvin and Hobbes: The Unconventional Story of Bill Watterson and His Revolutionary Comic Strip by Nevin Martell, was first published in 2009; an expanded edition was published in 2010. The book chronicles Martell's quest to tell the story of Calvin and Hobbes and Watterson through research and interviews with people connected to the cartoonist and his work. The director of the later documentary Dear Mr. Watterson referenced Looking for Calvin and Hobbes in discussing the production of the movie, and Martell appears in the film.
The American documentary film Dear Mr. Watterson, released in 2013, explores the impact and legacy of Calvin and Hobbes through interviews with authors, curators, historians, and numerous professional cartoonists.
The enduring significance of Calvin and Hobbes to international cartooning was recognized by the jury of the Angoulême International Comics Festival in 2014 by the awarding of its Grand Prix to Watterson, only the fourth American to ever receive the honor (after Will Eisner, Robert Crumb, and Art Spiegelman).
From 2016 to 2021, author Berkeley Breathed included Calvin and Hobbes in various Bloom County cartoons. He launched the first cartoon on April Fool's Day 2016 and jokingly issued a statement suggesting that he had acquired Calvin and Hobbes from Bill Watterson, who was "out of the Arizona facility, continent and looking forward to some well-earned financial security." While bearing Watterson's signature and drawing style as well as featuring characters from both Calvin and Hobbes and Breathed's Bloom County, it is unclear whether Watterson had any input into these cartoons or not.
Calvin and Hobbes remains the most viewed comic on GoComics, which cycles through old strips with an approximately 30-year delay.
===Grown-up Calvin===
Portraying Calvin as a teenager/adult has inspired writers.
In 2011, a comic strip appeared by cartoonists Dan and Tom Heyerman called Hobbes and Bacon. The strip depicts Calvin as an adult, married to Susie Derkins with a young daughter named after philosopher Francis Bacon, to whom Calvin gives Hobbes. Though consisting of only four strips originally, Hobbes and Bacon received considerable attention when it appeared and was continued by other cartoonists and artists.
A novel titled Calvin by CLA Young Adult Book Award–winning author Martine Leavitt was published in 2015.
The titular character of the comic strip Frazz has been noted for his similar appearance and personality to a grown-up Calvin. Creator Jef Mallett has stated that although Watterson is an inspiration to him, the similarities are unintentional.
|
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6,060 |
Campaign for Real Ale
|
The Campaign for Real Ale (CAMRA) is an independent voluntary consumer organisation headquartered in St Albans, which promotes real ale, cider and perry and traditional British pubs and clubs.
==History==
The organisation was founded on 16 March 1971 in Kruger's Bar, Dunquin, County Kerry, Ireland, by Michael Hardman, Graham Lees, Jim Makin, and Bill Mellor, who were opposed to the growing mass production of beer and the homogenisation of the British brewing industry. The original name was the Campaign for the Revitalisation of Ale. Following the formation of the Campaign, the first annual general meeting took place in 1972, at the Rose Inn in Coton Road, Nuneaton.
Early membership consisted of the four founders and their friends. Interest in CAMRA and its objectives spread rapidly, with 5,000 members signed up by 1973. Other early influential members included Christopher Hutt, author of Death of the English Pub, who succeeded Hardman as chairman, Frank Baillie, author of The Beer Drinker's Companion, and later the many times Good Beer Guide editor, Roger Protz.
In 1991, CAMRA had 30,000 members across the UK and abroad and, a year later, helped to launch the European Beer Consumers Union.
==Activities==
CAMRA's campaigns include promoting small brewing and pub businesses, reforming licensing laws, reducing tax on beer, and stopping continued consolidation among local British brewers. It also makes an effort to promote less common varieties of beer, including stout, porter, and mild, as well as traditional cider and perry.
CAMRA's states that real ale should be served without the use of additional carbonation. This means that "any beer brand which is produced in both cask and keg versions" is not admitted to CAMRA festivals if the brewery's marketing is deemed to imply an equivalence of quality or character between the two versions.
==Organisation==
CAMRA is organised on a federal basis, over 200 local branches, each covering a particular geographical area of the UK, that contribute to the central body of the organisation based in St Albans. It is governed by a National Executive, made up of 12 voluntary unpaid directors elected by the membership. The local branches are grouped into 16 regions across the UK, such as the West Midlands or Wessex.
==Publications and websites==
CAMRA publishes the Good Beer Guide, an annually compiled directory of the best 4,500 real ale outlets and listing of real ale brewers.
CAMRA members received a monthly newspaper called What's Brewing until its April 2021 issue and there is a quarterly colour magazine called Beer. It also maintains a National Inventory of Historic Pub Interiors to help bring greater recognition and protection to Britain's most historic pubs.
==Festivals==
CAMRA supports and promotes beer and cider festivals around the country, which are organised by local CAMRA branches. Generally, each festival charges an entry fee which either covers entry only or also includes a commemorative glass showing the details of the festival. A festival programme is usually also provided, with a list and description of the drinks available. Members may get discounted entrance to CAMRA festivals.
The Campaign also organises the annual Great British Beer Festival in August. It is now held in the Great, National & West Halls at the Olympia Exhibition Centre, in Kensington, London, having been held for a few years at Earl's Court as well as regionally in the past at venues such as Brighton and Leeds. This is the UK's largest beer festival, with over 900 beers, ciders and perries available over the week long event.
For many years, CAMRA also organised the National Winter Ales Festival. However, in 2017 this was re-branded as the Great British Beer Festival Winter where they award the Champion Winter Beer of Britain. Unlike the Great British Beer Festival, the Winter event does not have a permanent venue and is rotated throughout the country every three years. Recent hosts have been Derby and Norwich, with the event currently held each February in Birmingham. In 2020 CAMRA also launched the Great Welsh Beer Festival, to be held in Cardiff in April.
==Awards==
CAMRA presents awards for beers and pubs, such as the National Pub of the Year. The competition begins in the preceding year with branches choosing their local pub of the year through either a ballot or a panel of judges. The branch winners are entered into 16 regional competitions which are then visited by several individuals who agree the best using a scoring system that considers beer quality, aesthetic and welcome. The four finalists are announced each year before a ceremony to crown the winner in the spring. There are also the Pub Design Awards, which are held in association with English Heritage and the Victorian Society. These comprise several categories, including new build, refurbished and converted pubs.
The best known CAMRA award is the Champion Beer of Britain, which is selected at the Great British Beer Festival. Other awards include the Champion Beer of Scotland and the Champion Beer of Wales.
==National Beer Scoring Scheme==
CAMRA developed the National Beer Scoring Scheme (NBSS) as an easy to use scheme for judging beer quality in pubs, to assist CAMRA branches in selecting pubs for the Good Beer Guide. CAMRA members input their beer scores online via WhatPub or through the Good Beer Guide app.
==Pub heritage==
The CAMRA Pub Heritage Group identifies, records and helps to protect pub interiors of historic and/or architectural importance, and seeks to get them listed.
The group maintains two inventories of Heritage pubs, the National Inventory (NI), which contains only those pubs that have been maintained in their original condition (or have been modified very little) for at least thirty years, but usually since at least World War II. The second, larger, inventory is the Regional Inventory (RI), which is broken down by county and contains both those pubs listed in the NI and other pubs that are not eligible for the NI, for reasons such as having been overly modified, but are still considered historically important, or have particular architectural value.
==LocAle==
The LocAle scheme was launched in 2007 to promote locally brewed beers. The scheme functions slightly differently in each area, and is managed by each branch, but each is similar: if the beer is to be promoted as a LocAle it must come from a brewery within a predetermined number of miles set by each CAMRA branch, generally around 20, although the North London branch has set it at 30 miles from brewery to pub, even if it comes from a distribution centre further away; As of January 2021 the club had over 3,000 members and owned investments worth over £17 million. Although all investors must be CAMRA members, the CAMRA Members' Investment Club is not part of CAMRA Ltd.
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6,061 |
CNO cycle
|
In astrophysics, the carbon–nitrogen–oxygen (CNO) cycle, sometimes called Bethe–Weizsäcker cycle, after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker, is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction (p–p cycle), which is more efficient at the Sun's core temperature. The CNO cycle is hypothesized to be dominant in stars that are more than 1.3 times as massive as the Sun. One nucleus goes on to become carbon, nitrogen, and oxygen isotopes through a number of transformations in a repeating cycle.
The proton–proton chain is more prominent in stars the mass of the Sun or less. This difference stems from temperature dependency differences between the two reactions; pp-chain reaction starts at temperatures around (4 megakelvin), making it the dominant energy source in smaller stars. A self-maintaining CNO chain starts at approximately , but its energy output rises much more rapidly with increasing temperatures so that it becomes the dominant source of energy at approximately .
The Sun has a core temperature of around , and only of nuclei produced in the Sun are
born in the CNO cycle.
The CNO-I process was independently proposed by Carl von Weizsäcker and Hans Bethe
== Cold CNO cycles ==
Under typical conditions found in stars, catalytic hydrogen burning by the CNO cycles is limited by proton captures. Specifically, the timescale for beta decay of the radioactive nuclei produced is faster than the timescale for fusion. Because of the long timescales involved, the cold CNO cycles convert hydrogen to helium slowly, allowing them to power stars in quiescent equilibrium for many years.
=== CNO-I ===
The first proposed catalytic cycle for the conversion of hydrogen into helium was initially called the carbon–nitrogen cycle (CN-cycle), also referred to as the Bethe–Weizsäcker cycle in honor of the independent work of Carl Friedrich von Weizsäcker in 1937–38 drew on three earlier papers written in collaboration with Robert Bacher and Milton Stanley Livingston and which came to be known informally as Bethe's Bible. It was considered the standard work on nuclear physics for many years and was a significant factor in his being awarded the 1967 Nobel Prize in Physics. Bethe's original calculations suggested the CN-cycle was the Sun's primary source of energy.
→ → → → → →
This cycle is now understood as being the first part of a larger process, the CNO-cycle, and the main reactions in this part of the cycle (CNO-I) are:)
|- style="height:2em;"
| ||+ || ||→ || ||+ || || || ||+ ||
|- style="height:2em;"
| ||+ || ||→ || ||+ || || || ||+ ||
|- style="height:2em;"
| || || ||→ || ||+ || ||+ || ||+ ||||(half-life of 122.24 seconds
The limiting (slowest) reaction in the CNO-I cycle is the proton capture on . In 2006 it was experimentally measured down to stellar energies, revising the calculated age of globular clusters by around 1 billion years.
The neutrinos emitted in beta decay will have a spectrum of energy ranges, because although momentum is conserved, the momentum can be shared in any way between the positron and neutrino, with either emitted at rest and the other taking away the full energy, or anything in between, so long as all the energy from the Q-value is used. The total momentum received by the positron and the neutrino is not great enough to cause a significant recoil of the much heavier daughter nucleus and hence, its contribution to kinetic energy of the products, for the precision of values given here, can be neglected. Thus the neutrino emitted during the decay of nitrogen-13 can have an energy from zero up to , and the neutrino emitted during the decay of oxygen-15 can have an energy from zero up to . On average, about 1.7 MeV of the total energy output is taken away by neutrinos for each loop of the cycle, leaving about available for producing luminosity.
=== CNO-II ===
In a minor branch of the above reaction, occurring in the Sun's core 0.04% of the time, the final reaction involving shown above does not produce carbon-12 and an alpha particle, but instead produces oxygen-16 and a photon and continues
In detail:
Like the carbon, nitrogen, and oxygen involved in the main branch, the fluorine produced in the minor branch is merely an intermediate product; at steady state, it does not accumulate in the star.
=== CNO-III ===
This subdominant branch is significant only for massive stars. The reactions are started when one of the reactions in CNO-II results in fluorine-18 and a photon instead of nitrogen-14 and an alpha particle, and continues
→ → → → → →
In detail:
=== CNO-IV ===
Like the CNO-III, this branch is also only significant in massive stars. The reactions are started when one of the reactions in CNO-III results in fluorine-19 and a photon instead of nitrogen-15 and an alpha particle, and continues
In detail:
In some instances can combine with a helium nucleus to start a neon-sodium cycle, in which:
The sodium-23 can also turn into magesium-24 after proton bombardment, initiating the magnesium-aluminum cycle.
== Hot CNO cycles ==
Under conditions of higher temperature and pressure, such as those found in novae and X-ray bursts, the rate of proton captures exceeds the rate of beta-decay, pushing the burning to the proton drip line. The essential idea is that a radioactive species will capture a proton before it can beta decay, opening new nuclear burning pathways that are otherwise inaccessible. Because of the higher temperatures involved, these catalytic cycles are typically referred to as the hot CNO cycles; because the timescales are limited by beta decays instead of proton captures, they are also called the beta-limited CNO cycles.
=== HCNO-I ===
The difference between the CNO-I cycle and the HCNO-I cycle is that captures a proton instead of decaying, leading to the total sequence
→→→→→→
In detail:
=== HCNO-II ===
The notable difference between the CNO-II cycle and the HCNO-II cycle is that captures a proton instead of decaying, and neon is produced in a subsequent reaction on , leading to the total sequence
→→→→→→
In detail:
=== HCNO-III ===
An alternative to the HCNO-II cycle is that captures a proton moving towards higher mass and using the same helium production mechanism as the CNO-IV cycle as
→→→→→→
In detail:
== Use in astronomy ==
While the total number of "catalytic" nuclei are conserved in the cycle, in stellar evolution the relative proportions of the nuclei are altered. When the cycle is run to equilibrium, the ratio of the carbon-12/carbon-13 nuclei is driven to 3.5, and nitrogen-14 becomes the most numerous nucleus, regardless of initial composition. During a star's evolution, convective mixing episodes moves material, within which the CNO cycle has operated, from the star's interior to the surface, altering the observed composition of the star. Red giant stars are observed to have lower carbon-12/carbon-13 and carbon-12/nitrogen-14 ratios than do main sequence stars, which is considered to be convincing evidence for the operation of the CNO cycle.
|
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6,062 |
Craps
|
Craps is a dice game in which players bet on the outcomes of the roll of a pair of dice. Players can wager money against each other (playing "street craps") or against a bank ("casino craps"). Because it requires little equipment, "street craps" can be played in informal settings. While shooting craps, players may use slang terminology to place bets and actions.
==History==
Craps developed in the United States from a simplification of the western European game of Hazard, also spelled Hazzard a detailed description of Hazard was provided by Edmond Hoyle in Hoyle's Games, Improved (1790). which in Hazard are instant-losing numbers for the first dice roll, regardless of the shooter's selected main number.
According to some accounts, Hazard was brought from London to New Orleans in approximately 1805 by the returning Bernard Xavier Philippe de Marigny de Mandeville, the young gambler and scion of a family of wealthy landowners in colonial Louisiana. Hazard allows the dice shooter to choose any number from five to nine as their "main" number; in a pamphlet published in 1933, Edward Tinker claimed that Marigny simplified the game by making the main always seven, Field hands taught their friends and deckhands, who carried the new game up the Mississippi River and its tributaries, although the game was never popular amongst the riverboat gamblers. which eventually spread throughout America by the 1910s,
The craps numbers of 2, 3, and 12 are similarly derived from Hazard. If the main is seven, then the two-dice sum of twelve is added to the crabs as a losing number on the first dice roll. This condition is retained in the simplified game called Pass. All three losing numbers (2, 3, and 12) on the first roll of Pass are jointly called the craps numbers. As introduced by Winn, "Don't Pass" bets were taken with a 5 percent commission to ensure the house retained an edge in running the game; this was replaced by the Bar-3 push for "Don't Pass", and later by the Bar-12 (or Bar-2) push.
Craps exploded in popularity during World War II,
===Dice===
The dice used at casinos for craps and many other games are sometimes called perfect or gambling house dice. These are generally made from translucent extruded cellulose, with perfectly square edges each in length, with pips drilled deep and filled with opaque paint matching the density of cellulose, which ensures the dice remain balanced. The dice are buffed and polished to a high glossy finish after the pips are set, and the edges usually are left sharp, also called square or razor edge. To discourage cheating and dice substitution, each die carries a serial number and the casino's logo or name.
Under New Jersey regulations, the shooter selects two dice from a set of at least five.
===Rules of play===
Each casino may set which bets are offered and different payouts for them, though a core set of bets and payouts is typical. Players take turns rolling two dice and whoever is throwing the dice is called the "shooter". Players can bet on the various options by placing chips directly on the appropriately-marked sections of the layout, or asking the base dealer or stickman to do so, depending on which bet is being made.
While acting as the shooter, a player must have a bet on either the "Pass" or the "Don't Pass" line or both. "Pass" and "Don't Pass" are sometimes called "Win" and "Lose", "Do" and "Don't", or "Right" and "Wrong". These frequently incorporate a reminder to the dealers as to which bets to pay or collect.
Two — "Snake Eyes", "Two Craps Two", "Double Aces", "Loose Deuce", "Snickies": The two ones that compose it look like a pair of small, beady eyes. During actual play, more common terms are "two craps two" during the comeout roll because the Pass line bet is lost on a comeout crap roll and/or because a bet on any craps would win. "Aces; double the field" would be a more common call when not on the comeout roll to remind the dealers to pay double on the field bets and encourage the field bettor to place subsequent bets and/or when no crap bets have been placed. Another name for the two is "loose deuce" or "Snickies" due to it sounding like "Snake eyes" but spoken with an accent.
Three — "Three Craps Three", "Ace Deuce", "Tracy", "Acey Deucy": Typically called as "three craps three" during the comeout roll, or "three, ace deuce, come away single" when not on the comeout to signify the come bet has been lost and to pay single to any field bettors. Three may also be referred to as "ace caught a deuce", "Tracy", or even less often "acey deucey".
Four (hard) — "Little Joe", "Joe", "Little Dick", "Little Joe from Kokomo", "Little Joe on the Front Row", "Ballerina": usually hard, is sometimes referred to as "Little Joe from Kokomo" or "Little Joe on the front row" or just "Little Joe".
|-
!Hard 6 / Hard 8
| Hard way
|10:1||9:1||9.09%
|Multi
|6 as a pair (3-3)8 as a pair (4-4)
|76 as a non-pair (1–5,2-4)8 as a non-pair (2-6,3-5)
|style="text-align:left;" | In the UK and Australia, the payout is 9.5:1 lowering the house edge to 4.55%.
Bonus Craps: Prior to the initial "come out roll", players may place an optional wager (usually a $1 minimum to a maximum $25) on one or more of the three Bonus Craps wagers, "All Small", "All Tall", or "All or Nothing at All." For players to win the "All Small" wager, the shooter must hit all five small numbers (2, 3, 4, 5, 6) before a seven is rolled; similarly, "All Tall" wins if all five high numbers (8, 9, 10, 11, 12) are hit before a seven is rolled.
These bets pay 35-for-1, for a house advantage of 7.76%. "All or Nothing at All" wins if the shooter hits all 10 numbers before a seven is rolled. This pays 176-for-1, for a house edge of 7.46%. For all three wagers, the order in which the numbers are hit does not matter. Whenever a seven is hit, including on the come out roll, all bonus bets lose, the bonus board is reset, and new bonus bets may be placed.
===Multiple different bets===
A player may wish to make multiple different bets. For example, a player may be wish to bet $1 on all hard ways and the horn. If one of the bets win the dealer may automatically replenish the losing bet with profits from the winning bet. In this example, if the shooter rolls a hard 8 (pays 9:1), the horn loses. The dealer may return $5 to the player and place the other $4 on the horn bet which lost. If the player does not want the bet replenished, he or she should request any or all bets be taken down.
===Working and not working bets===
A working bet is a live bet. Bets may also be on the board, but not in play and therefore not working. Pass line and come bets are always working meaning the chips are in play and the player is therefore wagering live money. Other bets may be working or not working depending whether a point has been established or player's choice. Place and buy bets are working by default when a point is established and not working when the point is off unless the player specifies otherwise. Lay bets are always working even if a point has not been established unless the player requests otherwise. At any time, a player may wish to take any bet or bets out of play. The dealer will put an "Off" button on the player's specific bet or bets; this allows the player to keep his chips on the board without a live wager. For example, if a player decides not to wager a place bet mid-roll but wishes to keep the chips on the number, he or she may request the bet be "not working" or "Off". The chips remain on the table, but the player cannot win from or lose chips which are not working.
The opposite is also allowed. By default place and buy bets are not working without an established point; a player may wish to wager chips before a point has been established. In this case, the player would request the bet be working in which the dealer will place an "On" button on the specified chips.
=== Betting variants ===
These variants depend on the casino and the table, and sometimes a casino will have different tables that use or omit these variants and others.
11 is a point number instead of a natural. Rolling an 11 still pays "Yo" center-table bets, but the Pass line does not automatically win (and the Don't Pass line does not automatically lose) when 11 is rolled on the come-out. Making the point pays 3:1 on Pass/Come odds bets (1:3 on Don't Pass/Come odds); all line bets are still even money. This substantially reduces the odds of a natural (from 8/36 to 6/36) and of making the point in general (since a 3:1 dog is added to the mix). All other things equal, the house edge on the Pass Line and Come bets for this play variation jumps dramatically to 9.75%.
12 pays 3:1 on the field. This is generally seen in rooms that have two different table minimums, on the tables with the higher minimums. The lower minimum ones will then have 2:1 odds. For example, the Mirage casino in Las Vegas features 3:1 odds.
11 pays 2:1 on the field. This variant is normally used when 12 pays 3:1, and neutralizes the house edge on the field.
Big 6/8 are unavailable. These bets are equivalent to placing or buying 6 or 8 as points, which have better payout for the same real odds, so Big 6/8 are rarely used and many casinos simply omit them from the layout. Casinos in Atlantic City are even prohibited by law from offering Big 6/8 bets.
==Optimal betting==
When craps is played in a casino, all bets have a house advantage. That is, it can be shown mathematically that a player will (with 100% probability) lose all his or her money to the casino in the long run, while in the short run the player is more likely to lose money than make money. There may be players who are lucky and get ahead for a period of time, but in the long run these winning streaks are eroded away. One can slow, but not eliminate, one's average losses by only placing bets with the smallest house advantage.
The Pass/Don't Pass line, Come/Don't Come line, place 6, place 8, buy 4 and buy 10 (only under the casino rules where commission is charged only on wins) have the lowest house edge in the casino, and all other bets will, on average, lose money between three and twelve times faster because of the difference in house edges.
The place bets and buy bets differ from the Pass line and come line, in that place bets and buy bets can be removed at any time, since, while they are multi-roll bets, their odds of winning do not change from roll to roll, whereas Pass line bets and come line bets are a combination of different odds on their first roll and subsequent rolls. The first roll of a Pass line bet is 2:1 advantage for the player (8 wins, 4 losses), but it is "paid for" by subsequent rolls that are at the same disadvantage to the player as the Don't Pass bets were at an advantage. As such, they cannot profitably let the player take down the bet after the first roll. Players can bet or lay odds behind an established point depending on whether it was a Pass/Come or Don't Pass/Don't Come to lower house edge by receiving true odds on the point. Casinos which allow put betting allows players to increase or make new pass/come bets after the come-out roll. This bet generally has a higher house edge than place betting, unless the casino offers high odds.
Conversely, a player can take back (pick up) a Don't Pass or Don't Come bet after the first roll, but this cannot be recommended, because they already endured the disadvantaged part of the combination – the first roll. On that come-out roll, they win just 3 times (2 and 3), while losing 8 of them (7 and 11) and pushing one (12) out of the 36 possible rolls. On the other 24 rolls that become a point, their Don't Pass bet is now to their advantage by 6:3 (4 and 10), 6:4 (5 and 9) and 6:5 (6 and 8). If a player chooses to remove the initial Don't Come and/or Don't Pass line bet, he or she can no longer lay odds behind the bet and cannot re-bet the same Don't Pass and/or Don't Come number (players must make a new Don't Pass or come bets if desired). However, players can still make standard lay bets odds on any of the point numbers (4,5,6,8,9,10).
Among these, and the remaining numbers and possible bets, there are a myriad of systems and progressions that can be used with many combinations of numbers.
An important alternative metric is house advantage per roll (rather than per bet), which may be expressed in loss per hour. The typical pace of rolls varies depending on the number of players, but 102 rolls per hour is a cited rate for a nearly full table.
When throwing the dice, the player is expected to hit the farthest wall at the opposite end of the table (these walls are typically augmented with pyramidal structures to ensure highly unpredictable bouncing after impact). Casinos will sometimes allow a roll that does not hit the opposite wall as long as the dice are thrown past the middle of the table; a very short roll will be nullified as a "no roll". The dice may not be slid across the table and must be tossed. These rules are intended to prevent dexterous players from physically influencing the outcome of the roll.
Players are generally asked not to throw the dice above a certain height (such as the eye level of the dealers). This is both for the safety of those around the table, and to eliminate the potential use of such a throw as a distraction device in order to cheat. Some may also discourage or disallow unsanitary practices such as kissing or spitting on the dice.
In most casinos, players are not allowed to hand anything directly to dealers, and vice versa. Items such as cash, checks, and chips are exchanged by laying them down on the table; for example, when "buying in" (paying cash for chips), players are expected to place the cash on the layout: the dealer will take it and then place the chips in front of the player. This rule is enforced in order to allow the casino to easily monitor and record all transfers via overhead surveillance cameras, and to reduce the opportunity for cheating via sleight-of-hand.
Most casinos prohibit "call bets", and may have a warning such as "No Call Bets" printed on the layout to make this clear. This means a player may not call out a bet without also placing the corresponding chips on the table. Such a rule reduces the potential for misunderstanding in loud environments, as well as disputes over the amount that the player intended to bet after the outcome has been decided. Some casinos choose to allow call bets once players have bought-in. When allowed, they are usually made when a player wishes to bet at the last second, immediately before the dice are thrown, to avoid the risk of obstructing the roll. An exhaustive list of these is beyond the scope of this article, but the guidelines below are most commonly given.
=== Tips ===
Tipping the dealers is universal and expected in Craps. As in most other casino games, a player may simply place (or toss) chips onto the table and say, "For the dealers", "For the crew", etc. In craps, it is also common to place a bet for the dealers. This is usually done one of three ways: by placing an ordinary bet and simply declaring it for the dealers, as a "two-way", or "on top". A "Two-Way" is a bet for both parties: for example, a player may toss in two chips and say "Two Way Hard Eight", which will be understood to mean one chip for the player and one chip for the dealers. Players may also place a stack of chips for a bet as usual, but leave the top chip off-center and announce "on top for the dealers". The dealer's portion is often called a "toke" bet, which comes from the practice of using $1 slot machine tokens to place dealer bets in some casinos.
Casinos take steps to prevent this. The dice are usually required to hit the back wall of the table, which is normally faced with a jagged angular texture such as pyramids, making controlled spins more difficult. There has been no independent evidence that such methods can be successfully applied in a real casino.
New York Craps is one of the variations of craps played mostly in the Eastern coast of the US, true to its name. History states that this game was actually found and played in casinos in Yugoslavia, the UK and the Bahamas. In this craps variant, the house edge is greater than Las Vegas Craps or Bank craps. The table layout is also different, and is called a double-end-dealer table. This variation is different from the original craps game in several ways, but the primary difference is that New York craps does not allow Come or Don't Come bets. New York Craps Players bet on box numbers like 4, 5, 6, 8, 9, or 10. The overall house edge in New York craps is 5%.
===Cards replacing dice===
To replicate the original dice odds exactly without dice or possibility of card-counting, one scheme uses two shuffle machines each with just one deck of Ace through 6 each. Each machine selects one of the 6 cards at random and this is the roll. The selected cards are replaced and the decks are reshuffled for the next roll.
The prayer or invocation "Baby needs a new pair of shoes!" is associated with shooting craps.
===Floating craps===
Floating craps is an illegal operation of craps. The term floating refers to the practice of the game's operators using portable tables and equipment to quickly move the game from location to location to stay ahead of the law enforcement authorities.
The 1950 Broadway musical Guys and Dolls features a major plot point revolving around a floating craps game.
In the 1950s and 1960s The Sands Hotel in Las Vegas had a craps table that floated in the swimming pool, as a joke reference to the notoriety of the term.
===Records===
A Golden Arm is a craps player who rolls the dice for longer than one hour without losing. Likely the first known Golden Arm was Oahu native Stanley Fujitake, who rolled 118 times without sevening out in 3 hours and 6 minutes at the California Hotel and Casino on May 28, 1989.
The current record for length of a "hand" (successive rounds won by the same shooter) is 154 rolls including 25 passes by Patricia DeMauro of New Jersey, lasting 4 hours and 18 minutes, at the Borgata in Atlantic City, New Jersey, on May 23–24, 2009. She bested by over an hour the record held for almost 20 years – that of Fujitake.
|
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6,066 |
Carl von Clausewitz
|
Carl Philipp Gottfried (or Gottlieb) von Clausewitz ( , ; 1 July 1780 – 16 November 1831) was a Prussian general and military theorist who stressed the "moral" (in modern terms meaning psychological) and political aspects of waging war. His most notable work, (About War), though unfinished at his death, is considered a seminal treatise on military strategy and science.
Clausewitz stressed the multiplex interaction of diverse factors in war, noting how unexpected developments unfolding under the "fog of war" (i.e., in the face of incomplete, dubious, and often erroneous information and great fear, doubt, and excitement) call for rapid decisions by alert commanders. He saw history as a vital check on erudite abstractions that did not accord with experience. In contrast to the early work of Antoine-Henri Jomini, he argued that war could not be quantified or reduced to mapwork, geometry, and graphs. Clausewitz had many aphorisms, of which one of the most famous is, "War is the continuation of policy with other means."
==Name==
Clausewitz's Christian names are sometimes given in non-German sources as "Karl", "Carl Philipp Gottlieb", or "Carl Maria". He spelled his own given name with a "C" in order to identify with the classical Western tradition; writers who use "Karl" are often seeking to emphasize their German (rather than European) identity. "Carl Philipp Gottfried" appears on Clausewitz's tombstone. Nonetheless, sources such as military historian Peter Paret and Encyclopædia Britannica continue to use Gottlieb instead of Gottfried.
==Life and military career==
Clausewitz was born on 1 July 1780 in Burg bei Magdeburg in the Prussian Duchy of Magdeburg as the fourth and youngest son of a family that made claims to a noble status which Carl accepted. Clausewitz's family claimed descent from the Barons of Clausewitz in Upper Silesia, though scholars question the connection. His grandfather, the son of a Lutheran pastor, had been a professor of theology. Clausewitz's father, once a lieutenant in the army of Frederick the Great, King of Prussia, held a minor post in the Prussian internal-revenue service. Clausewitz entered the Prussian military service at the age of twelve as a lance corporal, eventually attaining the rank of major general.
Clausewitz served in the Rhine campaigns (1793–1794) including the siege of Mainz, when the Prussian Army invaded France during the French Revolution, and fought in the Napoleonic Wars from 1806 to 1815. He entered the Kriegsakademie (also cited as "The German War School", the "Military Academy in Berlin", and the "Prussian Military Academy," later the "War College") in Berlin in 1801 (aged 21), probably studied the writings of the philosophers Immanuel Kant and/or Johann Gottlieb Fichte and Friedrich Schleiermacher and won the regard of General Gerhard von Scharnhorst, the future first chief-of-staff of the newly reformed Prussian Army (appointed 1809). Clausewitz, Hermann von Boyen (1771–1848) and Karl von Grolman (1777–1843) were among Scharnhorst's primary allies in his efforts to reform the Prussian army between 1807 and 1814.
Clausewitz served during the Jena Campaign as aide-de-camp to Prince August. At the Battle of Jena-Auerstedt on 14 October 1806—when Napoleon invaded Prussia and defeated the Prussian-Saxon army commanded by Karl Wilhelm Ferdinand, Duke of Brunswick—he was captured, one of the 25,000 prisoners taken that day as the Prussian army disintegrated. He was 26. Clausewitz was held prisoner with his prince in France from 1807 to 1808. Returning to Prussia, he assisted in the reform of the Prussian army and state. She also edited, published, and introduced his collected works.
Opposed to Prussia's enforced alliance with Napoleon, Clausewitz left the Prussian army and served in the Imperial Russian Army from 1812 to 1813 during the Russian campaign, taking part in the Battle of Borodino (1812). Like many Prussian officers serving in Russia, he joined the Russian–German Legion in 1813. In the service of the Russian Empire, Clausewitz helped negotiate the Convention of Tauroggen (1812), which prepared the way for the coalition of Prussia, Russia, and the United Kingdom that ultimately defeated Napoleon and his allies. He was soon appointed chief-of-staff of Johann von Thielmann's III Corps. In that capacity he served at the Battle of Ligny and the Battle of Wavre during the Waterloo campaign in 1815. An army led personally by Napoleon defeated the Prussians at Ligny (south of Mont-Saint-Jean and the village of Waterloo) on 16 June 1815, but they withdrew in good order. Napoleon's failure to destroy the Prussian forces led to his defeat a few days later at the Battle of Waterloo (18 June 1815), when the Prussian forces arrived on his right flank late in the afternoon to support the Anglo-Dutch-Belgian forces pressing his front. Napoleon had convinced his troops that the field grey uniforms were those of Marshal Grouchy's grenadiers. Clausewitz's unit fought heavily outnumbered at Wavre (18–19 June 1815), preventing large reinforcements from reaching Napoleon at Waterloo. After the war, Clausewitz served as the director of the Kriegsakademie, where he served until 1830. In that year he returned to active duty with the army. Soon afterward, the outbreak of several revolutions around Europe and a crisis in Poland appeared to presage another major European war. Clausewitz was appointed chief of staff of the only army Prussia was able to mobilise in this emergency, which was sent to the Polish border. Its commander, Gneisenau, died of cholera (August 1831), and Clausewitz took command of the Prussian army's efforts to construct a to contain the great cholera outbreak (the first time cholera had appeared in modern heartland Europe, causing a continent-wide panic). Clausewitz himself died of the same disease shortly afterwards, on 16 November 1831. She wrote the preface for On War and had published most of his collected works by 1835. who was involved in numerous military campaigns, but he is famous primarily as a military theorist interested in the examination of war, utilising the campaigns of Frederick the Great and Napoleon as frames of reference for his work. He wrote a careful, systematic, philosophical examination of war in all its aspects. The result was his principal book, On War, a major work on the philosophy of war. It was unfinished when Clausewitz died and contains material written at different stages in his intellectual evolution, producing some significant contradictions between different sections. The sequence and precise character of that evolution is a source of much debate as to the exact meaning behind some seemingly contradictory observations in discussions pertinent to the tactical, operational and strategic levels of war, for example (though many of these apparent contradictions are simply the result of his dialectical method). Clausewitz constantly sought to revise the text, particularly between 1827 and his departure on his last field assignments, to include more material on "people's war" and forms of war other than high-intensity warfare between states, but relatively little of this material was included in the book. Jomini did not attempt to define war but Clausewitz did, providing (and dialectically comparing) a number of definitions. The first is his dialectical thesis: "War is thus an act of force to compel our enemy to do our will." The second, often treated as Clausewitz's 'bottom line,' is in fact merely his dialectical antithesis: "War is merely the continuation of policy with other means." The synthesis of his dialectical examination of the nature of war is his famous "trinity," saying that war is "a fascinating trinity—composed of primordial violence, hatred, and enmity, which are to be regarded as a blind natural force; the play of chance and probability, within which the creative spirit is free to roam; and its element of subordination, as an instrument of policy, which makes it subject to pure reason." Christopher Bassford says the best shorthand for Clausewitz's trinity should be something like "violent emotion/chance/rational calculation." However, it is frequently presented as "people/army/government," a misunderstanding based on a later paragraph in the same section. This misrepresentation was popularised by U.S. Army Colonel Harry Summers' Vietnam-era interpretation, facilitated by weaknesses in the 1976 Howard/Paret translation.
The degree to which Clausewitz managed to revise his manuscript to reflect that synthesis is the subject of much debate. His final reference to war and Politik, however, goes beyond his widely quoted antithesis: "War is simply the continuation of political intercourse with the addition of other means. We deliberately use the phrase 'with the addition of other means' because we also want to make it clear that war in itself does not suspend political intercourse or change it into something entirely different. In essentials that intercourse continues, irrespective of the means it employs. The main lines along which military events progress, and to which they are restricted, are political lines that continue throughout the war into the subsequent peace."
Clausewitz introduced systematic philosophical contemplation into Western military thinking, with powerful implications not only for historical and analytical writing but also for practical policy, military instruction, and operational planning. He relied on his own experiences, contemporary writings about Napoleon, and on deep historical research. His historiographical approach is evident in his first extended study, written when he was 25, of the Thirty Years' War. In On War, Clausewitz sees all wars as the sum of decisions, actions, and reactions in an uncertain and dangerous context, and also as a socio-political phenomenon. He also stressed the complex nature of war, which encompasses both the socio-political and the operational and stresses the primacy of state policy. (One should be careful not to limit his observations on war to war between states, however, as he certainly discusses other kinds of protagonists). Clausewitz, according to Azar Gat, expressed in the field of military theory the main themes of the Romantic reaction against the worldview of the Enlightenment, rejecting universal principles and stressing historical diversity and the forces of the human spirit. This explains the strength and value of many of his arguments, derived from this great cultural movement, but also his often harsh rhetoric against his predecessors.
Clausewitz's emphasis on the inherent superiority of the defense suggests that habitual aggressors are likely to end up as failures. The inherent superiority of the defense obviously does not mean that the defender will always win, however: there are other asymmetries to be considered. He was interested in co-operation between the regular army and militia or partisan forces, or citizen soldiers, as one possible—sometimes the only—method of defense. In the circumstances of the Wars of the French Revolution and those with Napoleon, which were energised by a rising spirit of nationalism, he emphasised the need for states to involve their entire populations in the conduct of war. This point is especially important, as these wars demonstrated that such energies could be of decisive importance and for a time led to a democratisation of the armed forces much as universal suffrage democratised politics.
While Clausewitz was intensely aware of the value of intelligence at all levels, he was also very skeptical of the accuracy of much military intelligence: "Many intelligence reports in war are contradictory; even more are false, and most are uncertain.... In short, most intelligence is false."
===Principal ideas===
Key ideas discussed in On War include:
the dialectical approach to military analysis
the methods of "critical analysis"
the economic profit-seeking logic of commercial enterprise is equally applicable to the waging of war and negotiating for peace
the nature of the balance-of-power mechanism
the relationship between political objectives and military objectives in war
the asymmetrical relationship between attack and defense
the nature of "military genius" (involving matters of personality and character, beyond intellect)
the "fascinating trinity" (wunderliche Dreifaltigkeit) of war
philosophical distinctions between "absolute war," "ideal war," and "real war"
in "real war," the distinctive poles of a) limited objectives (political and/or military) and b) war to "render the enemy helpless"
the idea that war and its conduct belong fundamentally to the social realm rather than to the realms of art or science
"strategy" belongs primarily to the realm of art, but is constrained by quantitative analyses of political benefits versus military costs & losses
"tactics" belongs primarily to the realm of science (most obvious in the development of siege warfare)
the importance of "moral forces" (more than simply "morale") as opposed to quantifiable physical elements
the "military virtues" of professional armies (which do not necessarily trump the rather different virtues of other kinds of fighting forces)
conversely, the very real effects of a superiority in numbers and "mass"
the essential unpredictability of war
the "fog of war"{{refn |group=note |"[T]he great uncertainty of all data in war is a peculiar difficulty, because all action must, to a certain extent, be planned in a mere twilight, which in addition not unfrequently—like the effect of a fog or moonshine—gives to things exaggerated dimensions and an unnatural appearance."—of what they believed to be Clausewitz's ideas, and the subsequent widespread adoption of the Prussian military system worldwide, had a deleterious effect on military theory and practice, due to their egregious misinterpretation of his ideas:
As described by Christopher Bassford, then-professor of strategy at the National War College of the United States:
Henry A. Kissinger, however, described Lenin's approach as being that politics is a continuation of war by other means, thus turning Clausewitz's argument "on its head." The idea that war involves inherent "friction" that distorts, to a greater or lesser degree, all prior arrangements, has become common currency in fields such as business strategy and sport. The phrase fog of war derives from Clausewitz's stress on how confused warfare can seem while one is immersed within it. The term center of gravity, used in a military context derives from Clausewitz's usage, which he took from Newtonian mechanics. In U.S. military doctrine, "center of gravity" refers to the basis of an opponent's power at the operational, strategic, or political level, though this is only one aspect of Clausewitz's use of the term.
===Late 20th and early 21st century===
The deterrence strategy of the United States in the 1950s was closely inspired by President Dwight Eisenhower's reading of Clausewitz as a young officer in the 1920s. Eisenhower was greatly impressed by Clausewitz's example of a theoretical, idealized "absolute war" in Vom Kriege as a way of demonstrating how absurd it would be to attempt such a strategy in practice. For Eisenhower, the age of nuclear weapons had made what was for Clausewitz in the early-19th century only a theoretical vision an all too real possibility in the mid-20th century. From Eisenhower's viewpoint, the best deterrent to war was to show the world just how appalling and horrific a nuclear "absolute war" would be if it should ever occur, hence a series of much-publicized nuclear tests in the Pacific, giving first priority in the defense budget to nuclear weapons and to their delivery-systems over conventional weapons, and making repeated statements in public that the United States was able and willing at all times to use nuclear weapons. In this way, through the massive retaliation doctrine and the closely related foreign-policy concept of brinkmanship, Eisenhower hoped to hold out a credible vision of Clausewitzian nuclear "absolute war" in order to deter the Soviet Union and/or China from ever risking a war or even conditions that might lead to a war with the United States.
{{blockquote|...Philanthropists may easily imagine there is a skillful method of disarming and overcoming an enemy without causing great bloodshed, and that this is the proper tendency of the art of War. However plausible this may appear, still it is an error which must be extirpated; for in such dangerous things as war, the errors which proceed from a spirit of benevolence are just the worst. As the use of physical power to the utmost extent by no means excludes the co-operation of the intelligence, it follows that he who uses force unsparingly, without reference to the quantity of bloodshed, must obtain a superiority if his adversary does not act likewise. By such means the former dictates the law to the latter, and both proceed to extremities, to which the only limitations are those imposed by the amount of counteracting force on each side.|author= Clausewitz |source= On War, Book I, Chapter 1 John E. Sheppard Jr., argues that by developing nuclear weapons, state-based conventional armies simultaneously both perfected their original purpose, to destroy a mirror image of themselves, and made themselves obsolete. No two powers have used nuclear weapons against each other, instead using diplomacy, conventional means, or proxy wars to settle disputes. If such a conflict did occur, presumably both combatants would be annihilated. Heavily influenced by the war in Vietnam and by antipathy to American strategist Henry Kissinger, the American biologist, musician, and game-theorist Anatol Rapoport argued in 1968 that a Clausewitzian view of war was not only obsolete in the age of nuclear weapons, but also highly dangerous as it promoted a "zero-sum paradigm" to international relations and a "dissolution of rationality" amongst decision-makers.
One prominent critic of Clausewitz is the Israeli military historian Martin van Creveld. In his 1991 book The Transformation of War, Creveld argued that Clausewitz's famous "Trinity" of people, army, and government was an obsolete socio-political construct based on the state, which was rapidly passing from the scene as the key player in war, and that he (Creveld) had constructed a new "non-trinitarian" model for modern warfare. Creveld's work has had great influence. Daniel Moran replied, 'The most egregious misrepresentation of Clausewitz's famous metaphor must be that of Martin van Creveld, who has declared Clausewitz to be an apostle of Trinitarian War, by which he means, incomprehensibly, a war of 'state against state and army against army,' from which the influence of the people is entirely excluded." Christopher Bassford went further, noting that one need only read the paragraph in which Clausewitz defined his Trinity to see "that the words 'people,' 'army,' and 'government' appear nowhere at all in the list of the Trinity's components.... Creveld's and Keegan's assault on Clausewitz's Trinity is not only a classic 'blow into the air,' i.e., an assault on a position Clausewitz doesn't occupy. It is also a pointless attack on a concept that is quite useful in its own right. In any case, their failure to read the actual wording of the theory they so vociferously attack, and to grasp its deep relevance to the phenomena they describe, is hard to credit." For an opposing view see the sixteen essays presented in Clausewitz in the Twenty-First Century edited by Hew Strachan and Andreas Herberg-Rothe.
In military academies, schools, and universities worldwide, Clausewitz's Vom Kriege is often (usually in translation) mandatory reading.
Some theorists of management look to Clausewitz - just as some look to Sun Tzu - to bolster ideas on the concept of leadership.
|
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"The Prince",
"dialectic",
"diplomacy",
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"France",
"universal suffrage",
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"Christopher Bassford",
"B.H. Liddell Hart",
"On War",
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"Azar Gat",
"Brühl family",
"Russian Empire",
"Battle of Jena-Auerstedt",
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"Prussian Army",
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"Jehuda L. Wallach",
"August Otto Rühle von Lilienstern",
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"National War College",
"Frederick the Great",
"Eisenhower",
"1826–1837 cholera pandemic",
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"Major general",
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"Robert Matteson Johnston",
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"Friedrich Engels",
"Encyclopædia Britannica",
"Antoine-Henri Jomini",
"U.S. Army Strategist",
"Reiner Pommerin",
"military strategy",
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"Mont-Saint-Jean, Belgium",
"fear",
"War in the Vendée",
"Wilhelm Wach",
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"massive retaliation",
"proxy wars",
"B. H. Liddell Hart",
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"Maurice de Saxe",
"Duchy of Magdeburg",
"Võ Nguyên Giáp",
"Karl von Grolman",
"military science",
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"Kingdom of Prussia",
"French invasion of Russia",
"Gordon A. Craig",
"Dwight Eisenhower",
"leadership",
"Breslau",
"Ferdinand Foch",
"Famous military writers",
"guerrilla warfare",
"August Neidhardt von Gneisenau",
"Karl Marx",
"Atomic Age",
"philosophy of war",
"battle",
"Spenser Wilkinson",
"Battle of Borodino",
"Ligny",
"Lynn Montross",
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"Romanticism",
"Friedrich Schleiermacher",
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"John McAuley Palmer (general)",
"nuclear proliferation",
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"Chichele Professor of Military History",
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"Burg bei Magdeburg",
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"Anatol Rapoport",
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"game theory",
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"The Emperor's New Clothes",
"lance corporal",
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"A History of Warfare",
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] |
6,068 |
Common Lisp
|
Common Lisp (CL) is a dialect of the Lisp programming language, published in American National Standards Institute (ANSI) standard document ANSI INCITS 226-1994 (S2018) (formerly X3.226-1994 (R1999)). The Common Lisp HyperSpec, a hyperlinked HTML version, has been derived from the ANSI Common Lisp standard.
The Common Lisp language was developed as a standardized and improved successor of Maclisp. By the early 1980s several groups were already at work on diverse successors to MacLisp: Lisp Machine Lisp (aka ZetaLisp), Spice Lisp, NIL and S-1 Lisp. Common Lisp sought to unify, standardise, and extend the features of these MacLisp dialects. Common Lisp is not an implementation, but rather a language specification. Several implementations of the Common Lisp standard are available, including free and open-source software and proprietary products.
Common Lisp is a general-purpose, multi-paradigm programming language. It supports a combination of procedural, functional, and object-oriented programming paradigms. As a dynamic programming language, it facilitates evolutionary and incremental software development, with iterative compilation into efficient run-time programs. This incremental development is often done interactively without interrupting the running application.
It also supports optional type annotation and casting, which can be added as necessary at the later profiling and optimization stages, to permit the compiler to generate more efficient code. For instance, fixnum can hold an unboxed integer in a range supported by the hardware and implementation, permitting more efficient arithmetic than on big integers or arbitrary precision types. Similarly, the compiler can be told on a per-module or per-function basis which type of safety level is wanted, using optimize declarations.
Common Lisp includes CLOS, an object system that supports multimethods and method combinations. It is often implemented with a Metaobject Protocol.
Common Lisp is extensible through standard features such as Lisp macros (code transformations) and reader macros (input parsers for characters).
Common Lisp provides partial backwards compatibility with Maclisp and John McCarthy's original Lisp. This allows older Lisp software to be ported to Common Lisp.
==History==
Work on Common Lisp started in 1981 after an initiative by ARPA manager Bob Engelmore to develop a single community standard Lisp dialect. Much of the initial language design was done via electronic mail. In 1982, Guy L. Steele Jr. gave the first overview of Common Lisp at the 1982 ACM Symposium on LISP and functional programming.
The first language documentation was published in 1984 as Common Lisp the Language (known as CLtL1), first edition. A second edition (known as CLtL2), published in 1990, incorporated many changes to the language, made during the ANSI Common Lisp standardization process: extended LOOP syntax, the Common Lisp Object System, the Condition System for error handling, an interface to the pretty printer and much more. But CLtL2 does not describe the final ANSI Common Lisp standard and thus is not a documentation of ANSI Common Lisp. The final ANSI Common Lisp standard then was published in 1994. Since then no update to the standard has been published. Various extensions and improvements to Common Lisp (examples are Unicode, Concurrency, CLOS-based IO) have been provided by implementations and libraries.
==Syntax==
Common Lisp is a dialect of Lisp. It uses S-expressions to denote both code and data structure. Function calls, macro forms and special forms are written as lists, with the name of the operator first, as in these examples:
(+ 2 2) ; adds 2 and 2, yielding 4. The function's name is '+'. Lisp has no operators as such.
(defvar *x*) ; Ensures that a variable *x* exists,
without giving it a value. The asterisks are part of
the name, by convention denoting a special (global) variable.
The symbol *x* is also hereby endowed with the property that
subsequent bindings of it are dynamic, rather than lexical.
(setf *x* 42.1) ; Sets the variable *x* to the floating-point value 42.1
Define a function that squares a number:
(defun square (x)
(* x x))
Execute the function:
(square 3) ; Returns 9
The 'let' construct creates a scope for local variables. Here
the variable 'a' is bound to 6 and the variable 'b' is bound
to 4. Inside the 'let' is a 'body', where the last computed value is returned.
Here the result of adding a and b is returned from the 'let' expression.
The variables a and b have lexical scope, unless the symbols have been
marked as special variables (for instance by a prior DEFVAR).
(let ((a 6)
(b 4))
(+ a b)) ; returns 10
==Data types==
Common Lisp has many data types.
===Scalar types===
Number types include integers, ratios, floating-point numbers, and complex numbers. Common Lisp uses bignums to represent numerical values of arbitrary size and precision. The ratio type represents fractions exactly, a facility not available in many languages. Common Lisp automatically coerces numeric values among these types as appropriate.
The Common Lisp character type is not limited to ASCII characters. Most modern implementations allow Unicode characters.
The symbol type is common to Lisp languages, but largely unknown outside them. A symbol is a unique, named data object with several parts: name, value, function, property list, and package. Of these, value cell and function cell are the most important. Symbols in Lisp are often used similarly to identifiers in other languages: to hold the value of a variable; however there are many other uses. Normally, when a symbol is evaluated, its value is returned. Some symbols evaluate to themselves, for example, all symbols in the keyword package are self-evaluating. Boolean values in Common Lisp are represented by the self-evaluating symbols T and NIL. Common Lisp has namespaces for symbols, called 'packages'.
A number of functions are available for rounding scalar numeric values in various ways. The function round rounds the argument to the nearest integer, with halfway cases rounded to the even integer. The functions truncate, floor, and ceiling round towards zero, down, or up respectively. All these functions return the discarded fractional part as a secondary value. For example, (floor -2.5) yields −3, 0.5; (ceiling -2.5) yields −2, −0.5; (round 2.5) yields 2, 0.5; and (round 3.5) yields 4, −0.5.
===Data structures===
Sequence types in Common Lisp include lists, vectors, bit-vectors, and strings. There are many operations that can work on any sequence type.
As in almost all other Lisp dialects, lists in Common Lisp are composed of conses, sometimes called cons cells or pairs. A cons is a data structure with two slots, called its car and cdr. A list is a linked chain of conses or the empty list. Each cons's car refers to a member of the list (possibly another list). Each cons's cdr refers to the next cons—except for the last cons in a list, whose cdr refers to the nil value. Conses can also easily be used to implement trees and other complex data structures; though it is usually advised to use structure or class instances instead. It is also possible to create circular data structures with conses.
Common Lisp supports multidimensional arrays, and can dynamically resize adjustable arrays if required. Multidimensional arrays can be used for matrix mathematics. A vector is a one-dimensional array. Arrays can carry any type as members (even mixed types in the same array) or can be specialized to contain a specific type of members, as in a vector of bits. Usually, only a few types are supported. Many implementations can optimize array functions when the array used is type-specialized. Two type-specialized array types are standard: a string is a vector of characters, while a bit-vector is a vector of bits.
Hash tables store associations between data objects. Any object may be used as key or value. Hash tables are automatically resized as needed.
Packages are collections of symbols, used chiefly to separate the parts of a program into namespaces. A package may export some symbols, marking them as part of a public interface. Packages can use other packages.
Structures, similar in use to C structs and Pascal records, represent arbitrary complex data structures with any number and type of fields (called slots). Structures allow single-inheritance.
Classes are similar to structures, but offer more dynamic features and multiple-inheritance. (See CLOS). Classes have been added late to Common Lisp and there is some conceptual overlap with structures. Objects created of classes are called Instances. A special case is Generic Functions. Generic Functions are both functions and instances.
===Functions===
Common Lisp supports first-class functions. For instance, it is possible to write functions that take other functions as arguments or return functions as well. This makes it possible to describe very general operations.
The Common Lisp library relies heavily on such higher-order functions. For example, the sort function takes a relational operator as an argument and key function as an optional keyword argument. This can be used not only to sort any type of data, but also to sort data structures according to a key.
Sorts the list using the > and < function as the relational operator.
(sort (list 5 2 6 3 1 4) #'>) ; Returns (6 5 4 3 2 1)
(sort (list 5 2 6 3 1 4) #'<) ; Returns (1 2 3 4 5 6)
Sorts the list according to the first element of each sub-list.
(sort (list '(9 A) '(3 B) '(4 C)) #'< :key #'first) ; Returns ((3 B) (4 C) (9 A))
The evaluation model for functions is very simple. When the evaluator encounters a form (f a1 a2...) then it presumes that the symbol named f is one of the following:
A special operator (easily checked against a fixed list)
A macro operator (must have been defined previously)
The name of a function (default), which may either be a symbol, or a sub-form beginning with the symbol lambda.
If f is the name of a function, then the arguments a1, a2, ..., an are evaluated in left-to-right order, and the function is found and invoked with those values supplied as parameters.
====Defining functions====
The macro defun defines functions where a function definition gives the name of the function, the names of any arguments, and a function body:
(defun square (x)
(* x x))
Function definitions may include compiler directives, known as declarations, which provide hints to the compiler about optimization settings or the data types of arguments. They may also include documentation strings (docstrings), which the Lisp system may use to provide interactive documentation:
(defun square (x)
"Calculates the square of the single-float x."
(declare (single-float x) (optimize (speed 3) (debug 0) (safety 1)))
(the single-float (* x x)))
Anonymous functions (function literals) are defined using lambda expressions, e.g. (lambda (x) (* x x)) for a function that squares its argument. Lisp programming style frequently uses higher-order functions for which it is useful to provide anonymous functions as arguments.
Local functions can be defined with flet and labels.
(flet ((square (x)
(* x x)))
(square 3))
There are several other operators related to the definition and manipulation of functions. For instance, a function may be compiled with the compile operator. (Some Lisp systems run functions using an interpreter by default unless instructed to compile; others compile every function).
====Defining generic functions and methods====
The macro defgeneric defines generic functions. Generic functions are a collection of methods.
The macro defmethod defines methods.
Methods can specialize their parameters over CLOS standard classes, system classes, structure classes or individual objects. For many types, there are corresponding system classes.
When a generic function is called, multiple-dispatch will determine the effective method to use.
(defgeneric add (a b))
(defmethod add ((a number) (b number))
(+ a b))
(defmethod add ((a vector) (b number))
(map 'vector (lambda (n) (+ n b)) a))
(defmethod add ((a vector) (b vector))
(map 'vector #'+ a b))
(defmethod add ((a string) (b string))
(concatenate 'string a b))
(add 2 3) ; returns 5
(add #(1 2 3 4) 7) ; returns #(8 9 10 11)
(add #(1 2 3 4) #(4 3 2 1)) ; returns #(5 5 5 5)
(add "COMMON " "LISP") ; returns "COMMON LISP"
Generic Functions are also a first class data type. There are many more features to Generic Functions and Methods than described above.
====The function namespace====
The namespace for function names is separate from the namespace for data variables. This is a key difference between Common Lisp and Scheme. For Common Lisp, operators that define names in the function namespace include defun, flet, labels, defmethod and defgeneric.
To pass a function by name as an argument to another function, one must use the function special operator, commonly abbreviated as #'. The first sort example above refers to the function named by the symbol > in the function namespace, with the code #'>. Conversely, to call a function passed in such a way, one would use the funcall operator on the argument.
Scheme's evaluation model is simpler: there is only one namespace, and all positions in the form are evaluated (in any order) – not just the arguments. Code written in one dialect is therefore sometimes confusing to programmers more experienced in the other. For instance, many Common Lisp programmers like to use descriptive variable names such as list or string which could cause problems in Scheme, as they would locally shadow function names.
Whether a separate namespace for functions is an advantage is a source of contention in the Lisp community. It is usually referred to as the Lisp-1 vs. Lisp-2 debate. Lisp-1 refers to Scheme's model and Lisp-2 refers to Common Lisp's model. These names were coined in a 1988 paper by Richard P. Gabriel and Kent Pitman, which extensively compares the two approaches.
====Multiple return values====
Common Lisp supports the concept of multiple values, where any expression always has a single primary value, but it might also have any number of secondary values, which might be received and inspected by interested callers. This concept is distinct from returning a list value, as the secondary values are fully optional, and passed via a dedicated side channel. This means that callers may remain entirely unaware of the secondary values being there if they have no need for them, and it makes it convenient to use the mechanism for communicating information that is sometimes useful, but not always necessary. For example,
The TRUNCATE function rounds the given number to an integer towards zero. However, it also returns a remainder as a secondary value, making it very easy to determine what value was truncated. It also supports an optional divisor parameter, which can be used to perform Euclidean division trivially:
(let ((x 1266778)
(y 458))
(multiple-value-bind (quotient remainder)
(truncate x y)
(format nil "~A divided by ~A is ~A remainder ~A" x y quotient remainder)))
=> "1266778 divided by 458 is 2765 remainder 408"
GETHASH returns the value of a key in an associative map, or the default value otherwise, and a secondary Boolean indicating whether the value was found. Thus code that does not care about whether the value was found or provided as the default can simply use it as-is, but when such distinction is important, it might inspect the secondary Boolean and react appropriately. Both use cases are supported by the same call and neither is unnecessarily burdened or constrained by the other. Having this feature at the language level removes the need to check for the existence of the key or compare it to null as would be done in other languages.
(defun get-answer (library)
(gethash 'answer library 42))
(defun the-answer-1 (library)
(format nil "The answer is ~A" (get-answer library)))
Returns "The answer is 42" if ANSWER not present in LIBRARY
(defun the-answer-2 (library)
(multiple-value-bind (answer sure-p)
(get-answer library)
(if (not sure-p)
"I don't know"
(format nil "The answer is ~A" answer))))
Returns "I don't know" if ANSWER not present in LIBRARY
Multiple values are supported by a handful of standard forms, most common of which are the MULTIPLE-VALUE-BIND special form for accessing secondary values and VALUES for returning multiple values:
(defun magic-eight-ball ()
"Return an outlook prediction, with the probability as a secondary value"
(values "Outlook good" (random 1.0)))
=> "Outlook good"
=> 0.3187
===Other types===
Other data types in Common Lisp include:
Pathnames represent files and directories in the filesystem. The Common Lisp pathname facility is more general than most operating systems' file naming conventions, making Lisp programs' access to files broadly portable across diverse systems.
Input and output streams represent sources and sinks of binary or textual data, such as the terminal or open files.
Common Lisp has a built-in pseudo-random number generator (PRNG). Random state objects represent reusable sources of pseudo-random numbers, allowing the user to seed the PRNG or cause it to replay a sequence.
Conditions are a type used to represent errors, exceptions, and other "interesting" events to which a program may respond.
Classes are first-class objects, and are themselves instances of classes called metaobject classes (metaclasses for short).
Readtables are a type of object which control how Common Lisp's reader parses the text of source code. By controlling which readtable is in use when code is read in, the programmer can change or extend the language's syntax.
==Scope==
Like programs in many other programming languages, Common Lisp programs make use of names to refer to variables, functions, and many other kinds of entities. Named references are subject to scope.
The association between a name and the entity which the name refers to is called a binding.
Scope refers to the set of circumstances in which a name is determined to have a particular binding.
===Determiners of scope===
The circumstances which determine scope in Common Lisp include:
the location of a reference within an expression. If it's the leftmost position of a compound, it refers to a special operator or a macro or function binding, otherwise to a variable binding or something else.
the kind of expression in which the reference takes place. For instance, (go x) means transfer control to label x, whereas (print x) refers to the variable x. Both scopes of x can be active in the same region of program text, since tagbody labels are in a separate namespace from variable names. A special form or macro form has complete control over the meanings of all symbols in its syntax. For instance, in (defclass x (a b) ()), a class definition, the (a b) is a list of base classes, so these names are looked up in the space of class names, and x isn't a reference to an existing binding, but the name of a new class being derived from a and b. These facts emerge purely from the semantics of defclass. The only generic fact about this expression is that defclass refers to a macro binding; everything else is up to defclass.
the location of the reference within the program text. For instance, if a reference to variable x is enclosed in a binding construct such as a let which defines a binding for x, then the reference is in the scope created by that binding.
for a variable reference, whether or not a variable symbol has been, locally or globally, declared special. This determines whether the reference is resolved within a lexical environment, or within a dynamic environment.
the specific instance of the environment in which the reference is resolved. An environment is a run-time dictionary which maps symbols to bindings. Each kind of reference uses its own kind of environment. References to lexical variables are resolved in a lexical environment, et cetera. More than one environment can be associated with the same reference. For instance, thanks to recursion or the use of multiple threads, multiple activations of the same function can exist at the same time. These activations share the same program text, but each has its own lexical environment instance.
To understand what a symbol refers to, the Common Lisp programmer must know what kind of reference is being expressed, what kind of scope it uses if it is a variable reference (dynamic versus lexical scope), and also the run-time situation: in what environment is the reference resolved, where was the binding introduced into the environment, et cetera.
===Kinds of environment===
====Global====
Some environments in Lisp are globally pervasive. For instance, if a new type is defined, it is known everywhere thereafter. References to that type look it up in this global environment.
====Dynamic====
One type of environment in Common Lisp is the dynamic environment. Bindings established in this environment have dynamic extent, which means that a binding is established at the start of the execution of some construct, such as a let block, and disappears when that construct finishes executing: its lifetime is tied to the dynamic activation and deactivation of a block. However, a dynamic binding is not just visible within that block; it is also visible to all functions invoked from that block. This type of visibility is known as indefinite scope. Bindings which exhibit dynamic extent (lifetime tied to the activation and deactivation of a block) and indefinite scope (visible to all functions which are called from that block) are said to have dynamic scope.
Common Lisp has support for dynamically scoped variables, which are also called special variables. Certain other kinds of bindings are necessarily dynamically scoped also, such as restarts and catch tags. Function bindings cannot be dynamically scoped using flet (which only provides lexically scoped function bindings), but function objects (a first-level object in Common Lisp) can be assigned to dynamically scoped variables, bound using let in dynamic scope, then called using funcall or APPLY.
Dynamic scope is extremely useful because it adds referential clarity and discipline to global variables. Global variables are frowned upon in computer science as potential sources of error, because they can give rise to ad-hoc, covert channels of communication among modules that lead to unwanted, surprising interactions.
In Common Lisp, a special variable which has only a top-level binding behaves just like a global variable in other programming languages. A new value can be stored into it, and that value simply replaces what is in the top-level binding. Careless replacement of the value of a global variable is at the heart of bugs caused by the use of global variables. However, another way to work with a special variable is to give it a new, local binding within an expression. This is sometimes referred to as "rebinding" the variable. Binding a dynamically scoped variable temporarily creates a new memory location for that variable, and associates the name with that location. While that binding is in effect, all references to that variable refer to the new binding; the previous binding is hidden. When execution of the binding expression terminates, the temporary memory location is gone, and the old binding is revealed, with the original value intact. Of course, multiple dynamic bindings for the same variable can be nested.
In Common Lisp implementations which support multithreading, dynamic scopes are specific to each thread of execution. Thus special variables serve as an abstraction for thread local storage. If one thread rebinds a special variable, this rebinding has no effect on that variable in other threads. The value stored in a binding can only be retrieved by the thread which created that binding. If each thread binds some special variable *x*, then *x* behaves like thread-local storage. Among threads which do not rebind *x*, it behaves like an ordinary global: all of these threads refer to the same top-level binding of *x*.
Dynamic variables can be used to extend the execution context with additional context information which is implicitly passed from function to function without having to appear as an extra function parameter. This is especially useful when the control transfer has to pass through layers of unrelated code, which simply cannot be extended with extra parameters to pass the additional data. A situation like this usually calls for a global variable. That global variable must be saved and restored, so that the scheme doesn't break under recursion: dynamic variable rebinding takes care of this. And that variable must be made thread-local (or else a big mutex must be used) so the scheme doesn't break under threads: dynamic scope implementations can take care of this also.
In the Common Lisp library, there are many standard special variables. For instance, all standard I/O streams are stored in the top-level bindings of well-known special variables. The standard output stream is stored in *standard-output*.
Suppose a function foo writes to standard output:
(defun foo ()
(format t "Hello, world"))
To capture its output in a character string, *standard-output* can be bound to a string stream and called:
(with-output-to-string (*standard-output*)
(foo))
-> "Hello, world" ; gathered output returned as a string
====Lexical====
Common Lisp supports lexical environments. Formally, the bindings in a lexical environment have lexical scope and may have either an indefinite extent or dynamic extent, depending on the type of namespace. Lexical scope means that visibility is physically restricted to the block in which the binding is established. References which are not textually (i.e. lexically) embedded in that block simply do not see that binding.
The tags in a TAGBODY have lexical scope. The expression (GO X) is erroneous if it is not embedded in a TAGBODY which contains a label X. However, the label bindings disappear when the TAGBODY terminates its execution, because they have dynamic extent. If that block of code is re-entered by the invocation of a lexical closure, it is invalid for the body of that closure to try to transfer control to a tag via GO:
(defvar *stashed*) ;; will hold a function
(tagbody
(setf *stashed* (lambda () (go some-label)))
(go end-label) ;; skip the (print "Hello")
some-label
(print "Hello")
end-label)
-> NIL
When the TAGBODY is executed, it first evaluates the setf form which stores a function in the special variable *stashed*. Then the (go end-label) transfers control to end-label, skipping the code (print "Hello"). Since end-label is at the end of the tagbody, the tagbody terminates, yielding NIL. Suppose that the previously remembered function is now called:
(funcall *stashed*) ;; Error!
This situation is erroneous. One implementation's response is an error condition containing the message, "GO: tagbody for tag SOME-LABEL has already been left". The function tried to evaluate (go some-label), which is lexically embedded in the tagbody, and resolves to the label. However, the tagbody isn't executing (its extent has ended), and so the control transfer cannot take place.
Local function bindings in Lisp have lexical scope, and variable bindings also have lexical scope by default. By contrast with GO labels, both of these have indefinite extent. When a lexical function or variable binding is established, that binding continues to exist for as long as references to it are possible, even after the construct which established that binding has terminated. References to lexical variables and functions after the termination of their establishing construct are possible thanks to lexical closures.
Lexical binding is the default binding mode for Common Lisp variables. For an individual symbol, it can be switched to dynamic scope, either by a local declaration, by a global declaration. The latter may occur implicitly through the use of a construct like DEFVAR or DEFPARAMETER. It is an important convention in Common Lisp programming that special (i.e. dynamically scoped) variables have names which begin and end with an asterisk sigil * in what is called the "earmuff convention". If adhered to, this convention effectively creates a separate namespace for special variables, so that variables intended to be lexical are not accidentally made special.
Lexical scope is useful for several reasons.
Firstly, references to variables and functions can be compiled to efficient machine code, because the run-time environment structure is relatively simple. In many cases it can be optimized to stack storage, so opening and closing lexical scopes has minimal overhead. Even in cases where full closures must be generated, access to the closure's environment is still efficient; typically each variable becomes an offset into a vector of bindings, and so a variable reference becomes a simple load or store instruction with a base-plus-offset addressing mode.
Secondly, lexical scope (combined with indefinite extent) gives rise to the lexical closure, which in turn creates a whole paradigm of programming centered around the use of functions being first-class objects, which is at the root of functional programming.
Thirdly, perhaps most importantly, even if lexical closures are not exploited, the use of lexical scope isolates program modules from unwanted interactions. Due to their restricted visibility, lexical variables are private. If one module A binds a lexical variable X, and calls another module B, references to X in B will not accidentally resolve to the X bound in A. B simply has no access to X. For situations in which disciplined interactions through a variable are desirable, Common Lisp provides special variables. Special variables allow for a module A to set up a binding for a variable X which is visible to another module B, called from A. Being able to do this is an advantage, and being able to prevent it from happening is also an advantage; consequently, Common Lisp supports both lexical and dynamic scope.
==Macros==
A macro in Lisp superficially resembles a function in usage. However, rather than representing an expression which is evaluated, it represents a transformation of the program source code. The macro gets the source it surrounds as arguments, binds them to its parameters and computes a new source form. This new form can also use a macro. The macro expansion is repeated until the new source form does not use a macro. The final computed form is the source code executed at runtime.
Typical uses of macros in Lisp:
new control structures (example: looping constructs, branching constructs)
scoping and binding constructs
simplified syntax for complex and repeated source code
top-level defining forms with compile-time side-effects
data-driven programming
embedded domain specific languages (examples: SQL, HTML, Prolog)
implicit finalization forms
Various standard Common Lisp features also need to be implemented as macros, such as:
the standard setf abstraction, to allow custom compile-time expansions of assignment/access operators
with-accessors, with-slots, with-open-file and other similar WITH macros
Depending on implementation, if or cond is a macro built on the other, the special operator; when and unless consist of macros
The powerful loop domain-specific language
Macros are defined by the defmacro macro. The special operator macrolet allows the definition of local (lexically scoped) macros. It is also possible to define macros for symbols using define-symbol-macro and symbol-macrolet.
Paul Graham's book On Lisp describes the use of macros in Common Lisp in detail. Doug Hoyte's book Let Over Lambda extends the discussion on macros, claiming "Macros are the single greatest advantage that lisp has as a programming language and the single greatest advantage of any programming language." Hoyte provides several examples of iterative development of macros.
===Example using a macro to define a new control structure===
Macros allow Lisp programmers to create new syntactic forms in the language. One typical use is to create new control structures. The example macro provides an until looping construct. The syntax is:
(until test form*)
The macro definition for until:
(defmacro until (test &body body)
(let ((start-tag (gensym "START"))
(end-tag (gensym "END")))
`(tagbody ,start-tag
(when ,test (go ,end-tag))
(progn ,@body)
(go ,start-tag)
,end-tag)))
tagbody is a primitive Common Lisp special operator which provides the ability to name tags and use the go form to jump to those tags. The backquote ` provides a notation that provides code templates, where the value of forms preceded with a comma are filled in. Forms preceded with comma and at-sign are spliced in. The tagbody form tests the end condition. If the condition is true, it jumps to the end tag. Otherwise, the provided body code is executed and then it jumps to the start tag.
An example of using the above until macro:
(until (= (random 10) 0)
(write-line "Hello"))
The code can be expanded using the function macroexpand-1. The expansion for the above example looks like this:
(TAGBODY
START1136
(WHEN (ZEROP (RANDOM 10))
(GO #:END1137))
(PROGN (WRITE-LINE "hello"))
(GO #:START1136)
END1137)
During macro expansion the value of the variable test is (= (random 10) 0) and the value of the variable body is ((write-line "Hello")). The body is a list of forms.
Symbols are usually automatically upcased. The expansion uses the TAGBODY with two labels. The symbols for these labels are computed by GENSYM and are not interned in any package. Two go forms use these tags to jump to. Since tagbody is a primitive operator in Common Lisp (and not a macro), it will not be expanded into something else. The expanded form uses the when macro, which also will be expanded. Fully expanding a source form is called code walking.
In the fully expanded (walked) form, the when form is replaced by the primitive if:
(TAGBODY
START1136
(IF (ZEROP (RANDOM 10))
(PROGN (GO #:END1137))
NIL)
(PROGN (WRITE-LINE "hello"))
(GO #:START1136))
END1137)
All macros must be expanded before the source code containing them can be evaluated or compiled normally. Macros can be considered functions that accept and return S-expressions – similar to abstract syntax trees, but not limited to those. These functions are invoked before the evaluator or compiler to produce the final source code. Macros are written in normal Common Lisp, and may use any Common Lisp (or third-party) operator available.
===Variable capture and shadowing===
Common Lisp macros are capable of what is commonly called variable capture, where symbols in the macro-expansion body coincide with those in the calling context, allowing the programmer to create macros wherein various symbols have special meaning. The term variable capture is somewhat misleading, because all namespaces are vulnerable to unwanted capture, including the operator and function namespace, the tagbody label namespace, catch tag, condition handler and restart namespaces.
Variable capture can introduce software defects. This happens in one of the following two ways:
In the first way, a macro expansion can inadvertently make a symbolic reference which the macro writer assumed will resolve in a global namespace, but the code where the macro is expanded happens to provide a local, shadowing definition which steals that reference. Let this be referred to as type 1 capture.
The second way, type 2 capture, is just the opposite: some of the arguments of the macro are pieces of code supplied by the macro caller, and those pieces of code are written such that they make references to surrounding bindings. However, the macro inserts these pieces of code into an expansion which defines its own bindings that accidentally captures some of these references.
The Scheme dialect of Lisp provides a macro-writing system which provides the referential transparency that eliminates both types of capture problem. This type of macro system is sometimes called "hygienic", in particular by its proponents (who regard macro systems which do not automatically solve this problem as unhygienic).
In Common Lisp, macro hygiene is ensured one of two different ways.
One approach is to use gensyms: guaranteed-unique symbols which can be used in a macro-expansion without threat of capture. The use of gensyms in a macro definition is a manual chore, but macros can be written which simplify the instantiation and use of gensyms. Gensyms solve type 2 capture easily, but they are not applicable to type 1 capture in the same way, because the macro expansion cannot rename the interfering symbols in the surrounding code which capture its references. Gensyms could be used to provide stable aliases for the global symbols which the macro expansion needs. The macro expansion would use these secret aliases rather than the well-known names, so redefinition of the well-known names would have no ill effect on the macro.
Another approach is to use packages. A macro defined in its own package can simply use internal symbols in that package in its expansion. The use of packages deals with type 1 and type 2 capture.
However, packages don't solve the type 1 capture of references to standard Common Lisp functions and operators. The reason is that the use of packages to solve capture problems revolves around the use of private symbols (symbols in one package, which are not imported into, or otherwise made visible in other packages). Whereas the Common Lisp library symbols are external, and frequently imported into or made visible in user-defined packages.
The following is an example of unwanted capture in the operator namespace, occurring in the expansion of a macro:
expansion of UNTIL makes liberal use of DO
(defmacro until (expression &body body)
`(do () (,expression) ,@body))
macrolet establishes lexical operator binding for DO
(macrolet ((do (...) ... something else ...))
(until (= (random 10) 0) (write-line "Hello")))
The until macro will expand into a form which calls do which is intended to refer to the standard Common Lisp macro do. However, in this context, do may have a completely different meaning, so until may not work properly.
Common Lisp solves the problem of the shadowing of standard operators and functions by forbidding their redefinition. Because it redefines the standard operator do, the preceding is actually a fragment of non-conforming Common Lisp, which allows implementations to diagnose and reject it.
==Condition system==
The condition system is responsible for exception handling in Common Lisp. It provides conditions, handlers and restarts. Conditions are objects describing an exceptional situation (for example an error). If a condition is signaled, the Common Lisp system searches for a handler for this condition type and calls the handler. The handler can now search for restarts and use one of these restarts to automatically repair the current problem, using information such as the condition type and any relevant information provided as part of the condition object, and call the appropriate restart function.
These restarts, if unhandled by code, can be presented to users (as part of a user interface, that of a debugger for example), so that the user can select and invoke one of the available restarts. Since the condition handler is called in the context of the error (without unwinding the stack), full error recovery is possible in many cases, where other exception handling systems would have already terminated the current routine. The debugger itself can also be customized or replaced using the *debugger-hook* dynamic variable. Code found within unwind-protect forms such as finalizers will also be executed as appropriate despite the exception.
In the following example (using Symbolics Genera) the user tries to open a file in a Lisp function test called from the Read-Eval-Print-LOOP (REPL), when the file does not exist. The Lisp system presents four restarts. The user selects the Retry OPEN using a different pathname restart and enters a different pathname (lispm-init.lisp instead of lispm-int.lisp). The user code does not contain any error handling code. The whole error handling and restart code is provided by the Lisp system, which can handle and repair the error without terminating the user code.
Command: (test ">zippy>lispm-int.lisp")
Error: The file was not found.
For lispm:>zippy>lispm-int.lisp.newest
LMFS:OPEN-LOCAL-LMFS-1
Arg 0: #P"lispm:>zippy>lispm-int.lisp.newest"
s-A, : Retry OPEN of lispm:>zippy>lispm-int.lisp.newest
s-B: Retry OPEN using a different pathname
s-C, : Return to Lisp Top Level in a TELNET server
s-D: Restart process TELNET terminal
-> Retry OPEN using a different pathname
Use what pathname instead [default lispm:>zippy>lispm-int.lisp.newest]:
lispm:>zippy>lispm-init.lisp.newest
...the program continues
==Common Lisp Object System (CLOS)==
Common Lisp includes a toolkit for object-oriented programming, the Common Lisp Object System or CLOS. Peter Norvig explains how many Design Patterns are simpler to implement in a dynamic language with the features of CLOS (Multiple Inheritance, Mixins, Multimethods, Metaclasses, Method combinations, etc.).
Several extensions to Common Lisp for object-oriented programming have been proposed to be included into the ANSI Common Lisp standard, but eventually CLOS was adopted as the standard object-system for Common Lisp. CLOS is a dynamic object system with multiple dispatch and multiple inheritance, and differs radically from the OOP facilities found in static languages such as C++ or Java. As a dynamic object system, CLOS allows changes at runtime to generic functions and classes. Methods can be added and removed, classes can be added and redefined, objects can be updated for class changes and the class of objects can be changed.
CLOS has been integrated into ANSI Common Lisp. Generic functions can be used like normal functions and are a first-class data type. Every CLOS class is integrated into the Common Lisp type system. Many Common Lisp types have a corresponding class. There is more potential use of CLOS for Common Lisp. The specification does not say whether conditions are implemented with CLOS. Pathnames and streams could be implemented with CLOS. These further usage possibilities of CLOS for ANSI Common Lisp are not part of the standard. Actual Common Lisp implementations use CLOS for pathnames, streams, input–output, conditions, the implementation of CLOS itself and more.
==Compiler and interpreter==
A Lisp interpreter directly executes Lisp source code provided as Lisp objects (lists, symbols, numbers, ...) read from s-expressions. A Lisp compiler generates bytecode or machine code from Lisp source code. Common Lisp allows both individual Lisp functions to be compiled in memory and the compilation of whole files to externally stored compiled code (fasl files).
Several implementations of earlier Lisp dialects provided both an interpreter and a compiler. Unfortunately often the semantics were different. These earlier Lisps implemented lexical scoping in the compiler and dynamic scoping in the interpreter. Common Lisp requires that both the interpreter and compiler use lexical scoping by default. The Common Lisp standard describes both the semantics of the interpreter and a compiler. The compiler can be called using the function compile for individual functions and using the function compile-file for files. Common Lisp allows type declarations and provides ways to influence the compiler code generation policy. For the latter various optimization qualities can be given values between 0 (not important) and 3 (most important): speed, space, safety, debug and compilation-speed.
There is also a function to evaluate Lisp code: eval. eval takes code as pre-parsed s-expressions and not, like in some other languages, as text strings. This way code can be constructed with the usual Lisp functions for constructing lists and symbols and then this code can be evaluated with the function eval. Several Common Lisp implementations (like Clozure CL and SBCL) are implementing eval using their compiler. This way code is compiled, even though it is evaluated using the function eval.
The file compiler is invoked using the function compile-file. The generated file with compiled code is called a fasl (from fast load) file. These fasl files and also source code files can be loaded with the function load into a running Common Lisp system. Depending on the implementation, the file compiler generates byte-code (for example for the Java Virtual Machine), C language code (which then is compiled with a C compiler) or, directly, native code.
Common Lisp implementations can be used interactively, even though the code gets fully compiled. The idea of an Interpreted language thus does not apply for interactive Common Lisp.
The language makes a distinction between read-time, compile-time, load-time, and run-time, and allows user code to also make this distinction to perform the wanted type of processing at the wanted step.
Some special operators are provided to especially suit interactive development; for instance, defvar will only assign a value to its provided variable if it wasn't already bound, while defparameter will always perform the assignment. This distinction is useful when interactively evaluating, compiling and loading code in a live image.
Some features are also provided to help writing compilers and interpreters. Symbols consist of first-level objects and are directly manipulable by user code. The progv special operator allows to create lexical bindings programmatically, while packages are also manipulable. The Lisp compiler is available at runtime to compile files or individual functions. These make it easy to use Lisp as an intermediate compiler or interpreter for another language.
==Code examples==
===Birthday paradox===
The following program calculates the smallest number of people in a room for whom the probability of unique birthdays is less than 50% (the birthday paradox, where for 1 person the probability is obviously 100%, for 2 it is 364/365, etc.). The answer is 23.
In Common Lisp, by convention, constants are enclosed with + characters.
(defconstant +year-size+ 365)
(defun birthday-paradox (probability number-of-people)
(let ((new-probability (* (/ (- +year-size+ number-of-people)
+year-size+)
probability)))
(if (< new-probability 0.5)
(1+ number-of-people)
(birthday-paradox new-probability (1+ number-of-people)))))
Calling the example function using the REPL (Read Eval Print Loop):
CL-USER > (birthday-paradox 1.0 1)
23
===Sorting a list of person objects===
We define a class person and a method for displaying the name and age of a person.
Next we define a group of persons as a list of person objects.
Then we iterate over the sorted list.
(defclass person ()
((name :initarg :name :accessor person-name)
(age :initarg :age :accessor person-age))
(:documentation "The class PERSON with slots NAME and AGE."))
(defmethod display ((object person) stream)
"Displaying a PERSON object to an output stream."
(with-slots (name age) object
(format stream "~a (~a)" name age)))
(defparameter *group*
(list (make-instance 'person :name "Bob" :age 33)
(make-instance 'person :name "Chris" :age 16)
(make-instance 'person :name "Ash" :age 23))
"A list of PERSON objects.")
(dolist (person (sort (copy-list *group*)
'>
key #'person-age))
(display person *standard-output*)
(terpri))
It prints the three names with descending age.
Bob (33)
Ash (23)
Chris (16)
===Exponentiating by squaring===
Use of the LOOP macro is demonstrated:
(defun power (x n)
(loop with result = 1
while (plusp n)
when (oddp n) do (setf result (* result x))
do (setf x (* x x)
n (truncate n 2))
finally (return result)))
Example use:
CL-USER > (power 2 200)
1606938044258990275541962092341162602522202993782792835301376
Compare with the built in exponentiation:
CL-USER > (= (expt 2 200) (power 2 200))
T
===Find the list of available shells===
WITH-OPEN-FILE is a macro that opens a file and provides a stream. When the form is returning, the file is automatically closed. FUNCALL calls a function object. The LOOP collects all lines that match the predicate.
(defun list-matching-lines (file predicate)
"Returns a list of lines in file, for which the predicate applied to
the line returns T."
(with-open-file (stream file)
(loop for line = (read-line stream nil nil)
while line
when (funcall predicate line)
collect it)))
The function AVAILABLE-SHELLS calls the above function LIST-MATCHING-LINES with a pathname and an anonymous function as the predicate. The predicate returns the pathname of a shell or NIL (if the string is not the filename of a shell).
(defun available-shells (&optional (file #p"/etc/shells"))
(list-matching-lines
file
(lambda (line)
(and (plusp (length line))
(char= (char line 0) #\/)
(pathname
(string-right-trim '(#\space #\tab) line))))))
Example results (on Mac OS X 10.6):
CL-USER > (available-shells)
(#P"/bin/bash" #P"/bin/csh" #P"/bin/ksh" #P"/bin/sh" #P"/bin/tcsh" #P"/bin/zsh")
==Comparison with other Lisps==
Common Lisp is most frequently compared with, and contrasted to, Scheme—if only because they are the two most popular Lisp dialects. Scheme predates CL, and comes not only from the same Lisp tradition but from some of the same engineers—Guy Steele, with whom Gerald Jay Sussman designed Scheme, chaired the standards committee for Common Lisp.
Common Lisp is a general-purpose programming language, in contrast to Lisp variants such as Emacs Lisp and AutoLISP which are extension languages embedded in particular products (GNU Emacs and AutoCAD, respectively). Unlike many earlier Lisps, Common Lisp (like Scheme) uses lexical variable scope by default for both interpreted and compiled code.
Most of the Lisp systems whose designs contributed to Common Lisp—such as ZetaLisp and Franz Lisp—used dynamically scoped variables in their interpreters and lexically scoped variables in their compilers. Scheme introduced the sole use of lexically scoped variables to Lisp; an inspiration from ALGOL 68. CL supports dynamically scoped variables as well, but they must be explicitly declared as "special". There are no differences in scoping between ANSI CL interpreters and compilers.
Common Lisp is sometimes termed a Lisp-2 and Scheme a Lisp-1, referring to CL's use of separate namespaces for functions and variables. (In fact, CL has many namespaces, such as those for go tags, block names, and loop keywords). There is a long-standing controversy between CL and Scheme advocates over the tradeoffs involved in multiple namespaces. In Scheme, it is (broadly) necessary to avoid giving variables names that clash with functions; Scheme functions frequently have arguments named lis, lst, or lyst so as not to conflict with the system function list. However, in CL it is necessary to explicitly refer to the function namespace when passing a function as an argument—which is also a common occurrence, as in the sort example above.
CL also differs from Scheme in its handling of Boolean values. Scheme uses the special values #t and #f to represent truth and falsity. CL follows the older Lisp convention of using the symbols T and NIL, with NIL standing also for the empty list. In CL, any non-NIL value is treated as true by conditionals, such as if, whereas in Scheme all non-#f values are treated as true. These conventions allow some operators in both languages to serve both as predicates (answering a Boolean-valued question) and as returning a useful value for further computation, but in Scheme the value '() which is equivalent to NIL in Common Lisp evaluates to true in a Boolean expression.
Lastly, the Scheme standards documents require tail-call optimization, which the CL standard does not. Most CL implementations do offer tail-call optimization, although often only when the programmer uses an optimization directive. Nonetheless, common CL coding style does not favor the ubiquitous use of recursion that Scheme style prefers—what a Scheme programmer would express with tail recursion, a CL user would usually express with an iterative expression in do, dolist, loop, or (more recently) with the iterate package.
==Implementations==
See the Category Common Lisp implementations.
Common Lisp is defined by a specification (like Ada and C) rather than by one implementation (like Perl). There are many implementations, and the standard details areas in which they may validly differ.
In addition, implementations tend to come with extensions, which provide functionality not covered in the standard:
Interactive Top-Level (REPL)
Garbage Collection
Debugger, Stepper and Inspector
Weak data structures (hash tables)
Extensible sequences
Extensible LOOP
Environment access
CLOS Meta-object Protocol
CLOS based extensible streams
CLOS based Condition System
Network streams
Persistent CLOS
Unicode support
Foreign-Language Interface (often to C)
Operating System interface
Java Interface
Threads and Multiprocessing
Application delivery (applications, dynamic libraries)
Saving of images
Free and open-source software libraries have been created to support extensions to Common Lisp in a portable way, and are most notably found in the repositories of the Common-Lisp.net and CLOCC (Common Lisp Open Code Collection) projects.
Common Lisp implementations may use any mix of native code compilation, byte code compilation or interpretation. Common Lisp has been designed to support incremental compilers, file compilers and block compilers. Standard declarations to optimize compilation (such as function inlining or type specialization) are proposed in the language specification. Most Common Lisp implementations compile source code to native machine code. Some implementations can create (optimized) stand-alone applications. Others compile to interpreted bytecode, which is less efficient than native code, but eases binary-code portability. Some compilers compile Common Lisp code to C code. The misconception that Lisp is a purely interpreted language is most likely because Lisp environments provide an interactive prompt and that code is compiled one-by-one, in an incremental way. With Common Lisp incremental compilation is widely used.
Some Unix-based implementations (CLISP, SBCL) can be used as a scripting language; that is, invoked by the system transparently in the way that a Perl or Unix shell interpreter is.
===List of implementations===
====Commercial implementations====
Allegro Common Lisp: for Microsoft Windows, FreeBSD, Linux, Apple macOS and various UNIX variants. Allegro CL provides an Integrated Development Environment (IDE) (for Windows and Linux) and extensive capabilities for application delivery.
Liquid Common Lisp: formerly called Lucid Common Lisp. Only maintenance, no new releases.
LispWorks: for Microsoft Windows, FreeBSD, Linux, Apple macOS, iOS, Android and various UNIX variants. LispWorks provides an Integrated Development Environment (IDE) (available for most platforms, but not for iOS and Android) and extensive capabilities for application delivery.
mocl: for iOS, Android and macOS.
Open Genera: for DEC Alpha.
Scieneer Common Lisp: which is designed for high-performance scientific computing.
====Freely redistributable implementations====
Armed Bear Common Lisp (ABCL): A CL implementation that runs on the Java Virtual Machine. It includes a compiler to Java byte code, and allows access to Java libraries from CL. It was formerly just a component of the Armed Bear J Editor.
Clasp: A LLVM based implementation that seamlessly interoperates with C++ libraries. Runs on several Unix and Unix-like systems (including macOS).
CLISP: A bytecode-compiling implementation, portable and runs on several Unix and Unix-like systems (including macOS), as well as Microsoft Windows and several other systems.
Clozure CL (CCL): Originally a free and open-source fork of Macintosh Common Lisp. As that history implies, CCL was written for the Macintosh, but Clozure CL now runs on macOS, FreeBSD, Linux, Solaris and Windows. 32 and 64 bit x86 ports are supported on each platform. Additionally there are Power PC ports for Mac OS and Linux. CCL was previously known as OpenMCL, but that name is no longer used, to avoid confusion with the open source version of Macintosh Common Lisp.
CMUCL: Originally from Carnegie Mellon University, now maintained as free and open-source software by a group of volunteers. CMUCL uses a fast native-code compiler. It is available on Linux and BSD for Intel x86; Linux for Alpha; macOS for Intel x86 and PowerPC; and Solaris, IRIX, and HP-UX on their native platforms.
Corman Common Lisp: for Microsoft Windows. In January 2015 Corman Lisp has been published under MIT license.
Embeddable Common Lisp (ECL): ECL includes a bytecode interpreter and compiler. It can also compile Lisp code to machine code via a C compiler. ECL then compiles Lisp code to C, compiles the C code with a C compiler and can then load the resulting machine code. It is also possible to embed ECL in C programs, and C code into Common Lisp programs.
GNU Common Lisp (GCL): The GNU Project's Lisp compiler. Not yet fully ANSI-compliant, GCL is however the implementation of choice for several large projects including the mathematical tools Maxima, AXIOM and (historically) ACL2. GCL runs on Linux under eleven different architectures, and also under Windows, Solaris, and FreeBSD.
Macintosh Common Lisp (MCL): Version 5.2 for Apple Macintosh computers with a PowerPC processor running Mac OS X is open source. RMCL (based on MCL 5.2) runs on Intel-based Apple Macintosh computers using the Rosetta binary translator from Apple.
ManKai Common Lisp (MKCL): A branch of ECL. MKCL emphasises reliability, stability and overall code quality through a heavily reworked, natively multi-threaded, runtime system. On Linux, MKCL features a fully POSIX compliant runtime system.
Movitz: Implements a Lisp environment for x86 computers without relying on any underlying OS.
Poplog: Poplog implements a version of CL, with POP-11, and optionally Prolog, and Standard ML (SML), allowing mixed language programming. For all, the implementation language is POP-11, which is compiled incrementally. It also has an integrated Emacs-like editor that communicates with the compiler.
Steel Bank Common Lisp (SBCL): A branch from CMUCL. "Broadly speaking, SBCL is distinguished from CMU CL by a greater emphasis on maintainability." SBCL runs on the platforms CMUCL does, except HP/UX; in addition, it runs on Linux for AMD64, PowerPC, SPARC, MIPS, Windows x86 and AMD64. SBCL does not use an interpreter by default; all expressions are compiled to native code unless the user switches the interpreter on. The SBCL compiler generates fast native code according to a previous version of The Computer Language Benchmarks Game.
Ufasoft Common Lisp: port of CLISP for windows platform with core written in C++.
====Other implementations====
Austin Kyoto Common Lisp: an evolution of Kyoto Common Lisp by Bill Schelter
Butterfly Common Lisp: an implementation written in Scheme for the BBN Butterfly multi-processor computer
CLICC: a Common Lisp to C compiler
CLOE: Common Lisp for PCs by Symbolics
Codemist Common Lisp: used for the commercial version of the computer algebra system Axiom
ExperCommon Lisp: an early implementation for the Apple Macintosh by ExperTelligence
Golden Common Lisp: an implementation for the PC by GoldHill Inc.
Ibuki Common Lisp: a commercialized version of Kyoto Common Lisp
Kyoto Common Lisp: the first Common Lisp compiler that used C as a target language. GCL, ECL and MKCL originate from this Common Lisp implementation.
L: a small version of Common Lisp for embedded systems developed by IS Robotics, now iRobot
Lisp Machines (from Symbolics, TI and Xerox): provided implementations of Common Lisp in addition to their native Lisp dialect (Lisp Machine Lisp or Interlisp). CLOS was also available. Symbolics provides an enhanced version Common Lisp.
Procyon Common Lisp: an implementation for Windows and Mac OS, used by Franz for their Windows port of Allegro CL
Star Sapphire Common LISP: an implementation for the PC
SubL: a variant of Common Lisp used for the implementation of the Cyc knowledge-based system
Top Level Common Lisp: an early implementation for concurrent execution
WCL: a shared library implementation
VAX Common Lisp: Digital Equipment Corporation's implementation that ran on VAX systems running VMS or ULTRIX
XLISP: an implementation written by David Betz
==Applications==
Common Lisp is used to develop research applications (often in Artificial Intelligence), for rapid development of prototypes or for deployed applications.
Common Lisp is used in many commercial applications, including the Yahoo! Store web-commerce site, which originally involved Paul Graham and was later rewritten in C++ and Perl. Other notable examples include:
ACT-R, a cognitive architecture used in a large number of research projects.
Authorizer's Assistant, a large rule-based system used by American Express, analyzing credit requests.
Cyc, a long running project to create a knowledge-based system that provides a huge amount of common sense knowledge.
Gensym G2, a real-time expert system and business rules engine
Genworks GDL, based on the open-source Gendl kernel.
The development environment for the Jak and Daxter video game series, developed by Naughty Dog.
ITA Software's low fare search engine, used by travel websites such as Orbitz and Kayak.com and airlines such as American Airlines, Continental Airlines and US Airways.
Mirai, a 3D graphics suite.
Opusmodus is a music composition system based on Common Lisp, used in Computer assisted composition.
Prototype Verification System (PVS), a mechanized environment for formal specification and verification.
PWGL is a sophisticated visual programming environment based on Common Lisp, used in Computer assisted composition and sound synthesis.
Piano, a complete aircraft analysis suite, written in Common Lisp, used by companies like Boeing, Airbus, and Northrop Grumman.
Grammarly, an English-language writing-enhancement platform, has its core grammar engine written in Common Lisp.
The Dynamic Analysis and Replanning Tool (DART), which is said to alone have paid back during the years from 1991 to 1995 for all thirty years of DARPA investments in AI research.
NASA's Jet Propulsion Lab's "Deep Space 1", an award-winning Common Lisp program for autopiloting the Deep Space One spaceship.
SigLab, a Common Lisp platform for signal processing used in missile defense, built by Raytheon.
SPIKE, a scheduling system for Earth or space based observatories and satellites, notably the Hubble Space Telescope, written in Common Lisp.
Common Lisp has been used for prototyping the garbage collector of Microsoft's .NET Common Language Runtime.
The original version of Reddit, though the developers later switched to Python due to the lack of libraries for Common Lisp, according to an official blog post by Reddit co-founder Steve Huffman.
There also exist open-source applications written in Common Lisp, such as:
ACL2, a full-featured automated theorem prover for an applicative variant of Common Lisp.
Axiom, a sophisticated computer algebra system.
Maxima, a sophisticated computer algebra system, based on Macsyma.
OpenMusic, an object-oriented visual programming environment based on Common Lisp, used in computer assisted composition.
Pgloader, a data loader for PostgreSQL, which was re-written from Python to Common Lisp.
Stumpwm, a tiling, keyboard driven X11 Window Manager written entirely in Common Lisp.
|
[
"Hubble Space Telescope",
"R (programming language)",
"lexical scope",
"Computer assisted composition",
"Gerard Gazdar",
"Wade L. Hennessey",
"Artificial Intelligence",
"Berkeley Software Distribution",
"Airbus",
"Jo A. Lawless",
"SubL",
"ratio",
"Unicode",
"SQL",
"ACL2",
"Corman Common Lisp",
"rounding",
"Java (programming language)",
"Maclisp",
"Linux",
"Emacs Lisp",
"Common Lisp HyperSpec",
"Kyoto Common Lisp",
"x86",
"Tony Hasemer",
"Kenneth D. Forbus",
"CLISP",
"global variable",
"Euclidean division",
"REPL",
"Northrop Grumman",
"macOS",
"Multi-paradigm programming language",
"Hash table",
"Orbitz",
"Let Over Lambda",
"tail recursion",
"bit",
"Genera (operating system)",
"Practical Common Lisp",
"John H. Riley",
"Null morpheme",
"machine code",
"Java Virtual Machine",
"mocl",
"Scott Fahlman",
"Microsoft Windows",
"Metaobject",
"Compiler",
"Peter Norvig",
"Eric Benson",
"Jak and Daxter",
"Chris Mellish",
"metaprogramming",
"Common Lisp Object System",
"C++",
"specification",
"Kent Pitman",
"Common Lisp the Language",
"Wendy L. Milner",
"function literal",
"first-class object",
"Molly M. Miller",
"character (computing)",
"Open Genera",
"Cyc",
"S-expression",
"Sonya E. Keene",
"Otto Mayer",
"Patrick R. Harrison",
"dynamic programming language",
"object system",
"*Lisp",
"VAX",
"Ufasoft Common Lisp",
"Andreas Paepcke",
"Eugene Charniak",
"pseudo-random number generator",
"Interlisp",
"David A. Moon",
"multiple inheritance",
"abstract syntax tree",
"Maxima (software)",
"Robert Wilensky",
"computer assisted composition",
"Stephen Slade",
"Taiichi Yuasa",
"Naughty Dog",
"Reddit",
"birthday paradox",
"Category:Common Lisp implementations",
"Embeddable Common Lisp",
"Strongly-typed programming language",
"Armed Bear Common Lisp",
"SBCL",
"Lisp Machine Lisp",
"American Airlines",
".NET Framework",
"Steven L. Tanimoto",
"Dan Weinreb",
"Pavel Penev",
"Patrick Winston",
"multimethods",
"Boeing",
"Peter Seibel",
"free and open-source software",
"Lisp (programming language)",
"Defun",
"Armed Bear J Editor",
"computer algebra system",
"Julia (programming language)",
"Cadence SKILL",
"Symbolics Genera",
"US Airways",
"CMUCL",
"integrated development environment",
"Lisp Machine",
"Timothy Koschmann",
"Jim des Rivieres",
"Kayak.com",
"Clozure CL",
"Symbolics",
"let expression",
"Jerome Chailloux",
"Patrick M. Krusenotto",
"PostgreSQL",
"S-1 Lisp",
"William A. Stubblefield",
"ISLISP",
"Dylan (programming language)",
"Clasp (Common Lisp)",
"Macro (computer science)",
"Cross-platform",
"associative map",
"Mars Pathfinder",
"Guy L. Steele",
"John Dominque",
"ITA Software",
"POP-11",
"Peter Lee (computer scientist)",
"Drew V. McDermott",
"floating-point arithmetic",
"GNU",
"Dynamic Analysis and Replanning Tool",
"Library (computing)",
"object-oriented programming",
"GNU Common Lisp",
"Paul Graham (computer programmer)",
"bytecode",
"Ada (programming language)",
"complex number",
"Clive Maynard",
"hyperlink",
"Directive (programming)",
"Johan de Kleer",
"Unix shell",
"HTML",
"OpenMusic",
"Christopher K. Riesbeck",
"multiple dispatch",
"integer",
"Yahoo!",
"Prototype Verification System",
"automated theorem prover",
"James R. Meehan",
"David S. Touretzky",
"DARPA",
"W. Richard Stark",
"Axiom (computer algebra system)",
"Bill Schelter",
"Hiroshi G. Okuno",
"Java byte code",
"procedural programming",
"Raytheon",
"filesystem",
"David Jay Steele",
"C (programming language)",
"Gerald Jay Sussman",
"extension languages",
"Liquid Common Lisp",
"Clojure",
"Macintosh Common Lisp",
"Deep Space 1",
"Christian Queinnec",
"Prolog",
"metaclasses",
"EuLisp",
"Gensym G2",
"Unix",
"ManKai Common Lisp",
"Emacs",
"3GL",
"scope (programming)",
"Carnegie Mellon University",
"James L. Noyes",
"Stuart C. Shapiro",
"generic function",
"Perl",
"Profiling (computer programming)",
"Rodney Allen Brooks",
"ULTRIX",
"NIL (programming language)",
"ACT-R",
"Moose (Perl)",
"Python (programming language)",
"Yasuko Kitajima",
"Berthold K.P. Horn",
"applicative programming language",
"X3J13",
"Guy Steele",
"BBN Butterfly",
"functional programming",
"Iterative and incremental development",
"generic programming",
"FreeBSD",
"Method (computer programming)",
"Arbitrary-precision arithmetic",
"Steel Bank Common Lisp",
"OpenVMS",
"Richard Weyhrauch",
"On Lisp",
"Daniel G. Bobrow",
"Continental Airlines",
"ALGOL 68",
"AutoLISP",
"George F. Luger",
"The Computer Language Benchmarks Game",
"David B. Lamkins",
"Lexical scope",
"Boxing (computer science)",
"Deep Space One",
"earmuff",
"Digital Equipment Corporation",
"data-driven programming",
"Doug Hoyte",
"Mirai (software)",
"Spice Lisp",
"Roger C. Schank",
"Design pattern (computer science)",
"Gregor Kiczales",
"Scheme (programming language)",
"Steve Huffman",
"Golden Common Lisp",
"Richard P. Gabriel",
"gensym",
"Conrad Barski",
"addressing mode",
"VAX Common Lisp",
"Scieneer Common Lisp",
"ASCII",
"Sigil (computer programming)",
"American National Standards Institute",
"multi-paradigm programming language",
"Interpreted language",
"Standard ML",
"NASA",
"Jet Propulsion Lab",
"lexical closure",
"scripting language",
"Symbol (programming)",
"Allegro Common Lisp",
"business rules engine",
"Deborah G. Tatar",
"ZetaLisp",
"LispWorks",
"AutoLisp",
"dynamic scope",
"first-class function",
"reflective programming",
"incremental compiler",
"Guy L. Steele Jr.",
"relational operator",
"exception handling",
"data type",
"Masami Hagiya",
"Pascal (programming language)",
"Poplog",
"First-class citizen",
"Solaris (operating system)",
"Free and open-source software",
"namespaces",
"Common Language Runtime",
"Grammarly",
"Dynamic typing",
"Edmund Weitz"
] |
6,069 |
Color code
|
A color code is a system for encoding and representing non-color information with colors to facilitate communication. This information tends to be categorical (representing unordered/qualitative categories) though may also be sequential (representing an ordered/quantitative variable).
==History==
The earliest examples of color codes in use are for long-distance communication by use of flags, as in semaphore communication. The United Kingdom adopted a color code scheme for such communication wherein red signified danger and white signified safety, with other colors having similar assignments of meaning.
As chemistry and other technologies advanced, it became expedient to use coloration as a signal for telling apart things that would otherwise be confusingly similar, such as wiring in electrical and electronic devices, and pharmaceutical pills.
==Encoded Variable==
A color code encodes a variable, which may have different representations, where the color code type should match the variable type:
Categorical variable – the variable may represent discrete values of unordered qualitative data (e.g. blood type)
Binary variables are typically treated as a categorical variable (e.g. sex)
Quantitative variable – the variable represents ordered, quantitative data (e.g. age)
Discrete quantitative data (e.g. the 6 sides of a die: 1,2,3,4,5,6) are sometimes treated as a categorical variable, despite the ordered nature.
==Types==
The types of color code are:
Categorical – the colors are unordered, but are chosen to maximize saliency of the colors, by maximizing color difference between all color pair permutations.
Continuous – the colors are ordered and form a smooth color gradient.
Discrete – only a subset of a continuous color code are used (still ordered), where each is distinguishable from the others.
===Categorical===
When color is the only varied attribute, the color code is unidimensional. When other attributes are varied (e.g. shape, size), the code is multidimensional, where the dimensions can be independent (each encoding separate variables) or redundant (encoding the same variable). Partial redundancy sees one variable as a subset of another.
The ideal color scheme for a categorical color code depends on whether speed or accuracy is more important. Despite humans being able to distinguish 150 distinct colors along the hue dimension during comparative task, evidence supports that color schemes where colors differ only by hue (equal luminosity and colorfulness) should have a maximum of eight categories with optimized stimulus spacing along the hue dimension, Adding redundant coding of luminosity and colorfulness adds information and increases speed and accuracy of color decoding tasks. so color stimulus of at least 3 mm in diameter or thickness is recommended when the color is on paper or on a screen. Under normal conditions, colored backgrounds do not affect the interpretation of color codes, but chromatic (and/or low) illumination of surface color code can degrade performance.
Color codes are often designed without consideration for accessibility to color blind and blind people, and may even be inaccessible for those with normal color vision, since use of many colors to code many variables can lead to use of confusingly similar colors. Only 15–40% of the colorblind can correctly name surface color codes with 8–10 color categories, most of which test as mildly colorblind. This finding uses ideal illumination; when dimmer illumination is used, performance drops sharply.
In navigation:
Characteristic light
Navigation light
Sea mark
Traffic lights
Other technology:
At point of sale (especially for packaging within a huge range of products: to quickly differentiate variants, brands, categories)
Bottled gases
Fire extinguishers
Kerbside collection
Pipe marking
Queen bee birth year code
Underground utility location
Hospital emergency codes often incorporate colors (such as the widely used "Code Blue" indicating a cardiac arrest),
In military use:
Homeland Security Advisory System
Artillery shells and other munitions, which are color-coded according to their pyrotechnic contents
List of Rainbow Codes
NATO Military Symbols for Land Based Systems
Rainbow Herbicides
In social functions:
Black hat hacking, white hat, grey hat
Blue-collar worker, white-collar worker, pink-collar worker, grey-collar, green-collar worker
Handkerchief code
ISO 22324, Guidelines for color-coded alerts in public warning
Cooper's Color Code of the combat mindset
Rank in judo
Ribbon colors see: :Category:Ribbon symbolism
In religion:
Clerical vestments, frontals and altar hangings in Christian churches
|
[
"Traffic light",
"gendered associations of pink and blue",
"StarCraft",
"Black hat hacking",
"25-pair color code",
"Quantitative variable",
"White hat (computer security)",
"Magic (gaming)",
"white-collar worker",
"color blindness",
"Artillery shell",
"Handkerchief code",
"Three-phase electric power",
"Electronic color code",
"Queen bee",
"Rainbow Herbicides",
"color",
"Audio and video interfaces and connectors",
"Risk",
"color task",
"white",
"Kerbside collection",
"Jump start (vehicle)",
"Electrical wiring",
"Homeland Security Advisory System",
"Blue-collar worker",
"Liturgical colours",
"Color coding in data visualization",
"safety",
"pink-collar worker",
"Category:Ribbon symbolism",
"Secondary notation",
"Pipe marking",
"grey-collar",
"Jeff Cooper",
"Sea mark",
"Binary data",
"List of Rainbow Codes",
"Fire extinguisher",
"color difference",
"dice",
"luminosity",
"eight",
"grey hat",
"Characteristic light",
"Ribbon",
"Surround sound",
"Health (gaming)",
"packaging",
"Pill (pharmacy)",
"green-collar worker",
"NATO Military Symbols for Land Based Systems",
"visual angle",
"Hospital emergency codes",
"ISO 22324",
"red",
"role-playing game",
"Fiber-optic cable",
"Flag semaphore",
"United Kingdom",
"Stock keeping unit",
"Rank in judo",
"IALA",
"Navigation light",
"Halo: Combat Evolved",
"Utility color code",
"Bottled gas",
"Categorical variable",
"colorfulness",
"playing card suit",
"Ethernet physical layer",
"PC System Design Guide",
"League of Legends",
"cardiac arrest"
] |
6,080 |
CGI
|
CGI may refer to:
==Technology==
Computer-generated imagery, computer-graphic effects in films, television programs, and other visual media
Computer Graphics Interface, the low-level interface between the Graphical Kernel System and hardware
Common Gateway Interface, a standard for dynamic generation of web pages by a web server
CGI.pm, a Perl module for implementing Common Gateway Interface programs
Compacted graphite iron, a type of cast iron
Corrugated galvanised iron, a type of molded sheet metal
Cell Global Identity, a standard identifier for mobile phone cells
==Organizations==
California Graduate Institute, an independent graduate school specializing in psychology
Catholic Guides of Ireland, a Girl Guide association
Chulabhorn Graduate Institute, a private graduate institute in Thailand
CGI Aero or RusAir, a Russian airline
CGI Inc., a multinational information technology and business process services company
Clinton Global Initiative, a forum created by former US President Bill Clinton to discuss global problems
Coast Guard Intelligence, the intelligence branch of the United States Coast Guard
Commission for the Management and Application of Geoscience Information
Compagnie Générale Immobiliere, a Moroccan real-estate development company
Consultative Group on Indonesia, a former consortium of donors to the Indonesian government
Cuerpo Guardia de Infantería, an Argentine police riot control service
General Commissariat of Information, the Comisaría General de Información is an intelligence service within the National Police Corps of Spain.
==Other uses==
Clinical global impression, a family of scales to assess treatment response associated with mental disorders
Cognitively Guided Instruction, an approach to mathematics teaching and learning
CpG islands, in genetics, genomic regions that contain a high frequency of CG dinucleotides
Cape Girardeau Regional Airport (IATA airport code: CGI), an airport in Missouri, US
|
[
"Common Gateway Interface",
"Cognitively Guided Instruction",
"Computer-generated imagery",
"Graphical Kernel System",
"Cell Global Identity",
"Compagnie Générale Immobiliere",
"Consultative Group on Indonesia",
"Corrugated galvanised iron",
"Coast Guard Intelligence",
"California Graduate Institute",
"CGI Inc.",
"Cape Girardeau Regional Airport",
"General Commissariat of Information",
"Chulabhorn Graduate Institute",
"Commission for the Management and Application of Geoscience Information",
"CGI Aero",
"Clinical global impression",
"CpG islands",
"Cuerpo Guardia de Infantería",
"National Police Corps of Spain",
"Clinton Global Initiative",
"CGI.pm",
"Compacted graphite iron",
"Catholic Guides of Ireland"
] |
6,082 |
Cortex
|
Cortex or cortical may refer to:
==Biology==
Cortex (anatomy), the outermost layer of an organ
Cerebral cortex, the outer layer of the vertebrate cerebrum, part of which is the forebrain
Motor cortex, the regions of the cerebral cortex involved in voluntary motor functions
Prefrontal cortex, the anterior part of the frontal lobes of the brain
Visual cortex, regions of the cerebral cortex involved in visual functions
Cerebellar cortex, the outer layer of the vertebrate cerebellum
Renal cortex, the outer portion of the kidney
Adrenal cortex, a portion of the adrenal gland
Cell cortex, the region of a cell directly underneath the membrane
Cortex (hair), the middle layer of a strand of hair
Cortex (botany), the outer portion of the stem or root of a plant
==Entertainment==
Cortex (film), a 2008 French film directed by Nicolas Boukhrief
Cortex (podcast), a 2015 podcast
Doctor Neo Cortex, a fictional character in the Crash Bandicoot video game series
Nina Cortex, the niece of Neo Cortex
Cortex (band), a French jazz funk band featuring Alain Mion
Cortex, a Swedish post-punk alternative band featuring Freddie Wadling
==Other uses==
Cortex (archaeology), the outer layer of rock formed on the exterior of raw materials by chemical and mechanical weathering processes
Cortex (journal), cognitive science journal published by Elsevier
Cortex, a family of the ARM architecture of CPUs
Cortex, a division of Gemini Sound Products
Cortex, a digital lending platform by Think Finance
Cortex Pharmaceuticals, a company of New Jersey, United States
Cortex Innovation Community, a district in St. Louis, Missouri, United States
|
[
"Cerebral cortex",
"Cortex (archaeology)",
"Cortex (band)",
"Adrenal cortex",
"Prefrontal cortex",
"Cortex (podcast)",
"ARM architecture family",
"Cortex (botany)",
"List of Crash Bandicoot characters",
"Cordtex",
"Gemini Sound Products",
"Cerebellar cortex",
"Cortex (hair)",
"Cortex (anatomy)",
"Renal cortex",
"Corex (disambiguation)",
"Think Finance",
"Doctor Neo Cortex",
"Cortex Innovation Community",
"Cortex (journal)",
"Visual cortex",
"Cortex (film)",
"Cortex Pharmaceuticals",
"Freddie Wadling",
"Cell cortex",
"Motor cortex"
] |
6,084 |
Collection
|
Collection or Collections may refer to:
==Computing==
Collection (abstract data type), the abstract concept of collections in computer science
Collection (linking), the act of linkage editing in computing
Garbage collection (computing), automatic memory management method
==Mathematics==
Set (mathematics)
Class (set theory)
Family of sets
Indexed family
Multiset
Parametric family
==Albums==
===Collection===
Collection (Soccer Mommy album), 2017
Collection (2NE1 album), 2012
Collection (Agnes album), 2013
Collection (Arvingarna album), 2002
Collection (Jason Becker album), 2008
Collection (Tracy Chapman album), 2001
Collection (The Charlatans album)
Collection (Dave Grusin album), 1989
Collection (The Jam album)
Collection (Wynonna Judd album)
Collection (Magnus Uggla album), 1985
Collection (Men Without Hats album), 1996
Collection (MFÖ album), 2003
Collection (Mike Oldfield album), 2002
Collection (Praxis album), 1998
Collection (The Rankin Family album), 1996
Collection (Lee Ritenour album), 1991
Collection (Joe Sample album), 1991
Collection (Spyro Gyra album), 1991
Collection (The Stranglers album), 1998
Collection (Suicidal Tendencies album), 1993
Collection (Thee Michelle Gun Elephant album), 2001
Collection (The Warratahs album), 2003
Collection: The Shrapnel Years (Greg Howe album), 2006
Collection: The Shrapnel Years (Tony MacAlpine album), 2006
Collection: The Shrapnel Years (Vinnie Moore album), 2006
Collection I, a 1986 compilation album of songs by the Misfits
Collection II, a 1995 companion album to the Misfits' Collection I
===Collections===
Collections (Alexia album)
Collections (Rick Astley album), 2006
Collections (Cypress Hill album)
Collections (Terence Trent D'Arby album), 2006
Collections (Delphic album), 2013
Collections (Amanda Marshall album), 2006
Collections (Charlie Major album), 2006
Collections (Red Norvo, Art Pepper, Joe Morello and Gerry Wiggins album), 1957
Collections (Yanni album), 2008
Collections (The Young Rascals album), 1967
==Fashion==
Cruise collection
Texas Fashion Collection
== Other uses ==
Cash collection, the function of an accounts receivable department
Collection (church), money donated by the congregation during a church service
Collection agency, agency to collect cash
Collections management (museum)
Collection (museum), objects in a particular field forms the core basis for the museum
Fonds in archives
Private collection, sometimes just called "collection"
Collection (Oxford colleges), a beginning-of-term exam or Principal's Collections
Collection (horse), a horse carrying more weight on his hindquarters than his forehand
Collection (racehorse), an Irish-bred, Hong Kong–based Thoroughbred racehorse
Collection (publishing), a gathering of books under the same title at the same publisher
Scientific collection, any systematic collection of objects for scientific study
Collection (film), a 2021 film starring Alex Petttyfer
Collection #1, a database of sets of email addresses and passwords
Collections care, to prevent or delay the deterioration of cultural heritage
Collection class, in object-oriented programming
Generated collection, a musical scale formed by repeatedly adding a constant interval around the chromatic circle
|
[
"Indexed family",
"Collection (MFÖ album)",
"Collection (Men Without Hats album)",
"Collection (The Rankin Family album)",
"Collection (Praxis album)",
"Collection (abstract data type)",
"Collections (Charlie Major album)",
"Collection (Suicidal Tendencies album)",
"Collections management (museum)",
"Collection (Dave Grusin album)",
"Multiset",
"Collection (Magnus Uggla album)",
"archive",
"Collection (Jason Becker album)",
"Collection: The Shrapnel Years (Vinnie Moore album)",
"Collection (Soccer Mommy album)",
"Class (set theory)",
"Family of sets",
"Collections (Alexia album)",
"Parametric family",
"Collection (church)",
"Collection: The Shrapnel Years (Greg Howe album)",
"Collections (Rick Astley album)",
"Private collection",
"Collection: The Shrapnel Years (Tony MacAlpine album)",
"Collections (Amanda Marshall album)",
"Collection No. 1",
"Collecting",
"Collections (Red Norvo, Art Pepper, Joe Morello and Gerry Wiggins album)",
"Cruise collection",
"Aggregate (disambiguation)",
"Collection (publishing)",
"Collection (Lee Ritenour album)",
"Collection (2NE1 album)",
"Texas Fashion Collection",
"Collection (The Stranglers album)",
"Collection (Arvingarna album)",
"Collection (Mike Oldfield album)",
"Set (mathematics)",
"Collection (museum)",
"Collector (disambiguation)",
"Collection (racehorse)",
"Collections (Delphic album)",
"Cash collection",
"Fonds",
"Collection (Oxford colleges)",
"Collection (Tracy Chapman album)",
"Collection I",
"Collection (Joe Sample album)",
"Collection (linking)",
"Collection (The Warratahs album)",
"Garbage collection (computing)",
"Collections (Yanni album)",
"Collection (Thee Michelle Gun Elephant album)",
"Collections care",
"A Collection (disambiguation)",
"Collections (Cypress Hill album)",
"Collection (Agnes album)",
"Collection (The Jam album)",
"Collected (disambiguation)",
"Scientific collection",
"Collections (The Young Rascals album)",
"Collection class",
"Collection (The Charlatans album)",
"Collection agency",
"Collection (Wynonna Judd album)",
"Collection II",
"Collection (film)",
"Collection (Spyro Gyra album)",
"Generated collection",
"Collections (Terence Trent D'Arby album)",
"Collection (horse)"
] |
6,085 |
Cauchy sequence
|
In mathematics, a Cauchy sequence is a sequence whose elements become arbitrarily close to each other as the sequence progresses. More precisely, given any small positive distance, all excluding a finite number of elements of the sequence are less than that given distance from each other. Cauchy sequences are named after Augustin-Louis Cauchy; they may occasionally be known as fundamental sequences.
It is not sufficient for each term to become arbitrarily close to the term. For instance, in the sequence of square roots of natural numbers:
a_n=\sqrt n,
the consecutive terms become arbitrarily close to each other – their differences
a_{n+1}-a_n = \sqrt{n+1}-\sqrt{n} = \frac{1}{\sqrt{n+1}+\sqrt{n}} < \frac{1}{2\sqrt n}
tend to zero as the index grows. However, with growing values of , the terms a_n become arbitrarily large. So, for any index and distance , there exists an index big enough such that a_m - a_n > d. As a result, no matter how far one goes, the remaining terms of the sequence never get close to ; hence the sequence is not Cauchy.
The utility of Cauchy sequences lies in the fact that in a complete metric space (one where all such sequences are known to converge to a limit), the criterion for convergence depends only on the terms of the sequence itself, as opposed to the definition of convergence, which uses the limit value as well as the terms. This is often exploited in algorithms, both theoretical and applied, where an iterative process can be shown relatively easily to produce a Cauchy sequence, consisting of the iterates, thus fulfilling a logical condition, such as termination.
Generalizations of Cauchy sequences in more abstract uniform spaces exist in the form of Cauchy filters and Cauchy nets.
==In real numbers==
A sequence
x_1, x_2, x_3, \ldots
of real numbers is called a Cauchy sequence if for every positive real number \varepsilon, there is a positive integer N such that for all natural numbers m, n > N,
|x_m - x_n| < \varepsilon,
where the vertical bars denote the absolute value. In a similar way one can define Cauchy sequences of rational or complex numbers. Cauchy formulated such a condition by requiring x_m - x_n to be infinitesimal for every pair of infinite m, n.
For any real number r, the sequence of truncated decimal expansions of r forms a Cauchy sequence. For example, when r = \pi, this sequence is (3, 3.1, 3.14, 3.141, ...). The mth and nth terms differ by at most 10^{1-m} when m < n, and as m grows this becomes smaller than any fixed positive number \varepsilon.
===Modulus of Cauchy convergence===
If (x_1, x_2, x_3, ...) is a sequence in the set X, then a modulus of Cauchy convergence for the sequence is a function \alpha from the set of natural numbers to itself, such that for all natural numbers k and natural numbers m, n > \alpha(k), |x_m - x_n| < 1/k.
Any sequence with a modulus of Cauchy convergence is a Cauchy sequence. The existence of a modulus for a Cauchy sequence follows from the well-ordering property of the natural numbers (let \alpha(k) be the smallest possible N in the definition of Cauchy sequence, taking \varepsilon to be 1/k). The existence of a modulus also follows from the principle of countable choice. Regular Cauchy sequences are sequences with a given modulus of Cauchy convergence (usually \alpha(k) = k or \alpha(k) = 2^k). Any Cauchy sequence with a modulus of Cauchy convergence is equivalent to a regular Cauchy sequence; this can be proven without using any form of the axiom of choice.
Moduli of Cauchy convergence are used by constructive mathematicians who do not wish to use any form of choice. Using a modulus of Cauchy convergence can simplify both definitions and theorems in constructive analysis. Regular Cauchy sequences were used by and by in constructive mathematics textbooks.
==In a metric space==
Since the definition of a Cauchy sequence only involves metric concepts, it is straightforward to generalize it to any metric space X.
To do so, the absolute value \left|x_m - x_n\right| is replaced by the distance d\left(x_m, x_n\right) (where d denotes a metric) between x_m and x_n.
Formally, given a metric space (X, d), a sequence of elements of X
x_1, x_2, x_3, \ldots
is Cauchy, if for every positive real number \varepsilon > 0 there is a positive integer N such that for all positive integers m, n > N, the distance
d\left(x_m, x_n\right) < \varepsilon.
Roughly speaking, the terms of the sequence are getting closer and closer together in a way that suggests that the sequence ought to have a limit in X.
Nonetheless, such a limit does not always exist within X: the property of a space that every Cauchy sequence converges in the space is called completeness, and is detailed below.
==Completeness==
A metric space (X, d) in which every Cauchy sequence converges to an element of X is called complete.
===Examples===
The real numbers are complete under the metric induced by the usual absolute value, and one of the standard constructions of the real numbers involves Cauchy sequences of rational numbers. In this construction, each equivalence class of Cauchy sequences of rational numbers with a certain tail behavior—that is, each class of sequences that get arbitrarily close to one another— is a real number.
A rather different type of example is afforded by a metric space X which has the discrete metric (where any two distinct points are at distance 1 from each other). Any Cauchy sequence of elements of X must be constant beyond some fixed point, and converges to the eventually repeating term.
===Non-example: rational numbers===
The rational numbers \Q are not complete (for the usual distance):
There are sequences of rationals that converge (in \R) to irrational numbers; these are Cauchy sequences having no limit in \Q. In fact, if a real number x is irrational, then the sequence (xn), whose n-th term is the truncation to n decimal places of the decimal expansion of x, gives a Cauchy sequence of rational numbers with irrational limit x. Irrational numbers certainly exist in \R, for example:
The sequence defined by x_0=1, x_{n+1}=\frac{x_n+2/x_n}{2} consists of rational numbers (1, 3/2, 17/12,...), which is clear from the definition; however it converges to the irrational square root of 2, see Babylonian method of computing square root.
The sequence x_n = F_n / F_{n-1} of ratios of consecutive Fibonacci numbers which, if it converges at all, converges to a limit \phi satisfying \phi^2 = \phi+1, and no rational number has this property. If one considers this as a sequence of real numbers, however, it converges to the real number \varphi = (1+\sqrt5)/2, the Golden ratio, which is irrational.
The values of the exponential, sine and cosine functions, exp(x), sin(x), cos(x), are known to be irrational for any rational value of x \neq 0, but each can be defined as the limit of a rational Cauchy sequence, using, for instance, the Maclaurin series.
===Non-example: open interval===
The open interval X = (0, 2) in the set of real numbers with an ordinary distance in \R is not a complete space: there is a sequence x_n = 1/n in it, which is Cauchy (for arbitrarily small distance bound d > 0 all terms x_n of n > 1/d fit in the (0, d) interval), however does not converge in X — its 'limit', number 0, does not belong to the space X .
===Other properties===
Every convergent sequence (with limit s, say) is a Cauchy sequence, since, given any real number \varepsilon > 0, beyond some fixed point, every term of the sequence is within distance \varepsilon/2 of s, so any two terms of the sequence are within distance \varepsilon of each other.
In any metric space, a Cauchy sequence x_n is bounded (since for some N, all terms of the sequence from the N-th onwards are within distance 1 of each other, and if M is the largest distance between x_N and any terms up to the N-th, then no term of the sequence has distance greater than M + 1 from x_N).
In any metric space, a Cauchy sequence which has a convergent subsequence with limit s is itself convergent (with the same limit), since, given any real number r > 0, beyond some fixed point in the original sequence, every term of the subsequence is within distance r/2 of s, and any two terms of the original sequence are within distance r/2 of each other, so every term of the original sequence is within distance r of s.
These last two properties, together with the Bolzano–Weierstrass theorem, yield one standard proof of the completeness of the real numbers, closely related to both the Bolzano–Weierstrass theorem and the Heine–Borel theorem. Every Cauchy sequence of real numbers is bounded, hence by Bolzano–Weierstrass has a convergent subsequence, hence is itself convergent. This proof of the completeness of the real numbers implicitly makes use of the least upper bound axiom. The alternative approach, mentioned above, of the real numbers as the completion of the rational numbers, makes the completeness of the real numbers tautological.
One of the standard illustrations of the advantage of being able to work with Cauchy sequences and make use of completeness is provided by consideration of the summation of an infinite series of real numbers
(or, more generally, of elements of any complete normed linear space, or Banach space). Such a series
\sum_{n=1}^{\infty} x_n is considered to be convergent if and only if the sequence of partial sums (s_{m}) is convergent, where s_m = \sum_{n=1}^{m} x_n. It is a routine matter to determine whether the sequence of partial sums is Cauchy or not, since for positive integers p > q,
s_p - s_q = \sum_{n=q+1}^p x_n.
If f : M \to N is a uniformly continuous map between the metric spaces M and N and (xn) is a Cauchy sequence in M, then (f(x_n)) is a Cauchy sequence in N. If (x_n) and (y_n) are two Cauchy sequences in the rational, real or complex numbers, then the sum (x_n + y_n) and the product (x_n y_n) are also Cauchy sequences.
==Generalizations==
===In topological vector spaces===
There is also a concept of Cauchy sequence for a topological vector space X: Pick a local base B for X about 0; then (x_k) is a Cauchy sequence if for each member V\in B, there is some number N such that whenever
n,m > N, x_n - x_m is an element of V. If the topology of X is compatible with a translation-invariant metric d, the two definitions agree.
===In topological groups===
Since the topological vector space definition of Cauchy sequence requires only that there be a continuous "subtraction" operation, it can just as well be stated in the context of a topological group: A sequence (x_k) in a topological group G is a Cauchy sequence if for every open neighbourhood U of the identity in G there exists some number N such that whenever m,n>N it follows that x_n x_m^{-1} \in U. As above, it is sufficient to check this for the neighbourhoods in any local base of the identity in G.
As in the construction of the completion of a metric space, one can furthermore define the binary relation on Cauchy sequences in G that (x_k) and (y_k) are equivalent if for every open neighbourhood U of the identity in G there exists some number N such that whenever m,n>N it follows that x_n y_m^{-1} \in U. This relation is an equivalence relation: It is reflexive since the sequences are Cauchy sequences. It is symmetric since y_n x_m^{-1} = (x_m y_n^{-1})^{-1} \in U^{-1} which by continuity of the inverse is another open neighbourhood of the identity. It is transitive since x_n z_l^{-1} = x_n y_m^{-1} y_m z_l^{-1} \in U' U where U' and U are open neighbourhoods of the identity such that U'U'' \subseteq U; such pairs exist by the continuity of the group operation.
===In groups===
There is also a concept of Cauchy sequence in a group G:
Let H=(H_r) be a decreasing sequence of normal subgroups of G of finite index.
Then a sequence (x_n) in G is said to be Cauchy (with respect to H) if and only if for any r there is N such that for all m, n > N, x_n x_m^{-1} \in H_r.
Technically, this is the same thing as a topological group Cauchy sequence for a particular choice of topology on G, namely that for which H is a local base.
The set C of such Cauchy sequences forms a group (for the componentwise product), and the set C_0 of null sequences (sequences such that \forall r, \exists N, \forall n > N, x_n \in H_r) is a normal subgroup of C. The factor group C/C_0 is called the completion of G with respect to H.
One can then show that this completion is isomorphic to the inverse limit of the sequence (G/H_r).
An example of this construction familiar in number theory and algebraic geometry is the construction of the p-adic completion of the integers with respect to a prime p. In this case, G is the integers under addition, and H_r is the additive subgroup consisting of integer multiples of p_r.
If H is a cofinal sequence (that is, any normal subgroup of finite index contains some H_r), then this completion is canonical in the sense that it is isomorphic to the inverse limit of (G/H)_H, where H varies over normal subgroups of finite index. For further details, see Ch. I.10 in Lang's "Algebra".
===In a hyperreal continuum===
A real sequence \langle u_n : n \in \N \rangle has a natural hyperreal extension, defined for hypernatural values H of the index n in addition to the usual natural n. The sequence is Cauchy if and only if for every infinite H and K, the values u_H and u_K are infinitely close, or adequal, that is,
\mathrm{st}(u_H-u_K)= 0
where "st" is the standard part function.
===Cauchy completion of categories===
introduced a notion of Cauchy completion of a category. Applied to \Q (the category whose objects are rational numbers, and there is a morphism from x to y if and only if x \leq y), this Cauchy completion yields \R\cup\left\{\infty\right\} (again interpreted as a category using its natural ordering).
|
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"integer",
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"infinitesimal",
"infinite series",
"normed linear space",
"Cauchy net",
"equivalence relation",
"Index of a subgroup",
"Serge Lang",
"Banach space",
"Fibonacci number",
"Cauchy filter",
"p-adic number",
"square root of 2",
"topological group",
"least upper bound axiom",
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"Transitive relation",
"well-ordering property",
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"group (mathematics)",
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"morphism",
"translation-invariant metric",
"discrete space",
"Iterative method",
"Golden ratio",
"Methods of computing square roots",
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"hypernatural",
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"local base",
"Identity element",
"countable choice",
"real number",
"absolute value",
"rational number",
"Complete metric space",
"number theory",
"uniformly continuous",
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"algebraic geometry",
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"natural number",
"topological vector space",
"factor group",
"Maclaurin series",
"standard part function",
"Heine–Borel theorem",
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"natural numbers",
"complex number",
"Cofinal (mathematics)",
"Construction of the real numbers",
"Bolzano–Weierstrass theorem",
"mathematics",
"Space (mathematics)",
"normal subgroup"
] |
6,088 |
Common Era
|
Common Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: " CE" and "AD " each describe the current year; "400 BCE" and "400 BC" are the same year.
The expression can be traced back to 1615, when it first appears in a book by Johannes Kepler as the (), They have been promoted as more sensitive to non-Christians by not referring to Jesus, the central figure of Christianity, especially via the religious terms "Christ" and ("Lord") used by the other abbreviations. without a year zero. In 1422, Portugal became the last Western European country to switch to the system begun by Dionysius.]]
The term "Common Era" is traced back in English to its appearance as "Vulgar Era" to distinguish years of the Anno Domini era, which was in popular use, from dates of the regnal year (the year of the reign of a sovereign) typically used in national law.
(The word 'vulgar' originally meant 'of the ordinary people', with no derogatory associations. and again, as , in 1617. A 1635 English edition of that book has the title page in English that may be the earliest-found use of Vulgar Era in English. A 1701 book edited by John Le Clerc includes the phrase "Before Christ according to the Vulgar Æra,6".
The Merriam-Webster Dictionary gives 1716 as the date of first use of the term "vulgar era" (which it defines as Christian era).
The first published use of "Christian Era" may be the Latin phrase on the title page of a 1584 theology book, . In 1649, the Latin phrase appeared in the title of an English almanac. A 1652 ephemeris may be the first instance found so far of the English use of "Christian Era".
The English phrase "Common Era" appears at least as early as 1708,
and in a 1715 book on astronomy it is used interchangeably with "Christian Era" and "Vulgar Era". A 1759 history book uses common æra in a generic sense, to refer to "the common era of the Jews". The first use of the phrase "before the common era" may be that in a 1770 work that also uses common era and vulgar era as synonyms, in a translation of a book originally written in German. The 1797 edition of the Encyclopædia Britannica uses the terms vulgar era and common era synonymously.
In 1835, in his book Living Oracles, Alexander Campbell, wrote: "The vulgar Era, or Anno Domini; the fourth year of Jesus Christ, the first of which was but eight days",
and also refers to the common era as a synonym for vulgar era with "the fact that our Lord was born on the 4th year before the vulgar era, called Anno Domini, thus making (for example) the 42d year from his birth to correspond with the 38th of the common era". The Catholic Encyclopedia (1909) in at least one article reports all three terms (Christian, Vulgar, Common Era) being commonly understood by the early 20th century.
The phrase "common era", in lower case, also appeared in the 19th century in a "generic" sense, not necessarily to refer to the Christian Era, but to any system of dates in common use throughout a civilization. Thus, "the common era of the Jews", "the common era of the Mahometans", "common era of the world", "the common era of the foundation of Rome".
When it did refer to the Christian Era, it was sometimes qualified, e.g., "common era of the Incarnation", "common era of the Nativity", or "common era of the birth of Christ".
An adapted translation of Common Era into Latin as was adopted in the 20th century by some followers of Aleister Crowley, and thus the abbreviation "e.v." or "EV" may sometimes be seen as a replacement for AD.
=== History of the use of the CE/BCE abbreviation ===
Although Jews have their own Hebrew calendar, they often use the Gregorian calendar without the AD prefix. As early as 1825, the abbreviation VE (for Vulgar Era) was in use among Jews to denote years in the Western calendar. , Common Era notation has also been in use for Hebrew lessons for more than a century.
== Contemporary usage ==
Some academics in the fields of theology, education, archaeology and history have adopted CE and BCE notation despite some disagreement. A study conducted in 2014 found that the BCE/CE notation is not growing at the expense of BC and AD notation in the scholarly literature, and that both notations are used in a relatively stable fashion.
===Australia===
In 2011, media reports suggested that the BC/AD notation in Australian school textbooks would be replaced by BCE/CE notation. The change drew opposition from some politicians and church leaders. Weeks after the story broke, the Australian Curriculum, Assessment and Reporting Authority denied the rumours and stated that the BC/AD notation would remain, with CE and BCE as an optional suggested learning activity.
===Canada===
In 2013, the Canadian Museum of Civilization (now the Canadian Museum of History) in Gatineau (opposite Ottawa), which had previously switched to BCE/CE, decided to change back to BC/AD in material intended for the public while retaining BCE/CE in academic content.
===Nepal===
The notation is in particularly common use in Nepal in order to disambiguate dates from the local (Indian or Hindu) calendar, Bikram or Vikram Sambat. Disambiguation is needed because the era of the Hindu calendar is quite close to the Common Era.
===United Kingdom===
In 2002, an advisory panel for the religious education syllabus for England and Wales recommended introducing BCE/CE dates to schools, and by 2018 some local education authorities were using them. English Heritage explains its era policy thus: "It might seem strange to use a Christian calendar system when referring to British prehistory, but the BC/AD labels are widely used and understood." Some parts of the BBC use BCE/CE, but some presenters have said they will not. The style guide for The Guardian says, under the entry for CE/BCE: "some people prefer CE (common era, current era, or Christian era) and BCE (before common era, etc.) to AD and BC, which, however, remain our style".
===United States===
In the United States, the use of the BCE/CE notation in textbooks was reported in 2005 to be growing. and by the Norton Anthology of English Literature. Others have taken a different approach. The US-based History Channel uses BCE/CE notation in articles on non-Christian religious topics such as Jerusalem and Judaism. The 2006 style guide for the Episcopal Diocese Maryland Church News says that BCE and CE should be used.
In June 2006, in the United States, the Kentucky State School Board reversed its decision to use BCE and CE in the state's new Program of Studies, leaving education of students about these concepts a matter of local discretion.
== Rationales ==
=== Support ===
The use of CE in Jewish scholarship was historically motivated by the desire to avoid the implicit "Our Lord" in the abbreviation AD. Although other aspects of dating systems are based in Christian origins, AD is a direct reference to Jesus as Lord. Proponents of the Common Era notation assert that the use of BCE/CE shows sensitivity to those who use the same year numbering system as the one that originated with and is currently used by Christians, but who are not themselves Christian.
Adena K. Berkowitz, in her application to argue before the United States Supreme Court, opted to use BCE and CE because, "Given the multicultural society that we live in, the traditional Jewish designationsB.C.E. and C.E. cast a wider net of inclusion." In the World History Encyclopedia, Joshua J. Mark wrote "Non-Christian scholars, especially, embraced [CE and BCE] because they could now communicate more easily with the Christian community. Jewish, Islamic, Hindu and Buddhist scholars could retain their [own] calendar but refer to events using the Gregorian Calendar as BCE and CE without compromising their own beliefs about the divinity of Jesus of Nazareth." In History Today, Michael Ostling wrote: "BC/AD Dating: In the year of whose Lord? The continuing use of AD and BC is not only factually wrong but also offensive to many who are not Christians." Roman Catholic priest and writer on interfaith issues Raimon Panikkar argued that the BCE/CE usage is the less inclusive option since they are still using the Christian calendar numbers and forcing it on other nations. In 1993, the English-language expert Kenneth G. Wilson speculated a slippery slope scenario in his style guide that, "if we do end by casting aside the AD/BC convention, almost certainly some will argue that we ought to cast aside as well the conventional numbering system [that is, the method of numbering years] itself, given its Christian basis." including the Southern Baptist Convention. Thus, the current year is written as in both notations (or, if further clarity is needed, as CE, or as AD ), and the year that Socrates died is represented as 399 BCE (the same year that is represented by 399 BC in the BC/AD notation). The abbreviations are sometimes written with small capital letters, or with periods (e.g., "B.C.E." or "C.E."). The US-based Society of Biblical Literature style guide for academic texts on religion prefers BCE/CE to BC/AD.
== Similar conventions in other languages ==
In Germany, Jews in Berlin seem to have already been using words translating to "(before the) common era" in the 18th century, while others like Moses Mendelssohn opposed this usage as it would hinder the integration of Jews into German society. In 1938 Nazi Germany, the use of this convention was also prescribed by the National Socialist Teachers League. However, it was soon discovered that many German Jews had been using the convention ever since the 18th century, and Time magazine found it ironic to see "Aryans following Jewish example nearly 200 years later".
In Spanish, common forms used for "BC" are and (for "", "before Christ"), with variations in punctuation and sometimes the use of () instead of . The also acknowledges the use of () and (). In scholarly writing, is the equivalent of the English "BCE", "" or "Before the Common Era".
In Welsh, OC can be expanded to equivalents of both AD () and CE (); for dates before the Common Era, CC (traditionally, ) is used exclusively, as would abbreviate to a mild obscenity.
In Russian since the October Revolution (1917) , lit. before our era) and lit. of our era) are used almost universally. Within Christian churches , i.e. before/after the birth of Christ, equivalent to ) remains in use.
In Polish, "p.n.e." (, lit. before our era) and "n.e." (, lit. of our era) are commonly used in historical and scientific literature. (before Christ) and (after Christ) see sporadic usage, mostly in religious publications.
In China, upon the foundation of the Republic of China, the Government in Nanking adopted the Republic of China calendar with 1912 designated as year 1, but used the Western calendar for international purposes. The translated term was (, "Western Era"), which is still used in Taiwan in formal documents. In 1949, the People's Republic of China adopted (, "Common Era") for both internal and external affairs in mainland China. This notation was extended to Hong Kong in 1997 and Macau in 1999 (de facto extended in 1966) through Annex III of Hong Kong Basic Law and Macau Basic Law, thus eliminating the ROC calendar in these areas. BCE is translated into Chinese as (, "Before the Common Era").
In Czech, the "n. l." ( which translates as of our year count) and "př. n. l." or "před n. l." ( meaning before our year count) is used, always after the year number. The direct translation of AD (, abbreviated as L. P.) or BC (, abbreviated as př. Kr.) is seen as archaic.
In Croatian the common form used for BC and AD are pr. Kr. (prije Krista, "before Christ") and p. Kr. (poslije Krista, after Christ). The abbreviations pr. n. e. (prije nove ere, before new era) and n. e. (nove ere, (of the) new era) have also recently been introduced.
In Danish, "f.v.t." (, before our time reckoning) and "e.v.t." (, after our time reckoning) are used as BCE/CE are in English. Also commonly used are "f.Kr." (, before Christ) and "e.Kr." (, after Christ), which are both placed after the year number in contrast with BC/AD in English.
In Macedonian, the terms "п.н.е." (пред нашата ера "before our era") and "н.е." (наша ера "our era") are used in every aspect.
In Estonian, "e.m.a." (, before our time reckoning) and "m.a.j." (, according to our time reckoning) are used as BCE and CE, respectively. Also in use are terms "eKr" (, before Christ) and "pKr" (, after Christ). In all cases, the abbreviation is written after the year number.
In Finnish, "eaa." (, before time reckoning) and "jaa." (, after the start of time reckoning) are used as BCE and CE, respectively. Also (decreasingly) in use are terms "eKr", (, before Christ) and "jKr". (, after Christ). In all cases, the abbreviation is written after the year number.
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6,091 |
Charles Robert Malden
|
Charles Robert Malden (9 August 1797 – 23 May 1855) was a nineteenth-century British naval officer, surveyor and educator. He is the discoverer of Malden Island in the central Pacific, which is named in his honour. He also founded Windlesham House School at Brighton, England.
==Biography==
Malden was born in Putney, Surrey, son of Jonas Malden, a surgeon. He entered British naval service at the age of 11 on 22 June 1809. He served nine years as a volunteer 1st class, midshipman, and shipmate, including one year in the English Channel and Bay of Biscay (1809), four years at the Cape of Good Hope and in the East Indies (1809–14), two and a half years on the North American and West Indian stations (1814–16), and a year and a half in the Mediterranean (1817–18). He was present at the capture of Mauritius and Java, and at the battles of Baltimore and New Orleans.
He passed the examination in the elements of mathematics and the theory of navigation at the Royal Naval Academy on 2–4 September 1816, and became a 1st Lieutenant on 1 September 1818. In eight years of active service as an officer, he served two and a half years in a surveying ship in the Mediterranean (1818–21), one and a half years in a surveying sloop in the English Channel and off the coast of Ireland (1823–24), and one and a half years as Surveyor of the frigate during a voyage (1824–26) to and from the Hawaiian Islands (then known as the "Sandwich islands").
In Hawaii he surveyed harbours which, he noted, were "said not to exist by Captains Cook and Vancouver." On the return voyage he discovered and explored uninhabited Malden Island in the central Pacific on 30 July 1825. After his return he left active service but remained at half pay. He served for several years as hydrographer to King William IV.
He married Frances Cole, daughter of Rev. William Hodgson Cole, rector of West Clandon and Vicar of Wonersh, near Guildford, Surrey, on 8 April 1828. Malden became the father of seven sons and a daughter.
From 1830 to 1836 he took pupils for the Royal Navy at Ryde, Isle of Wight. He purchased the school of Henry Worsley at Newport, Isle of Wight, in December 1836, reopened it as a preparatory school on 20 February 1837, and moved it to Montpelier Road in Brighton in December 1837. He built the Windlesham House School at Brighton in 1844, and conducted the school until his death there in 1855. He was succeeded as headmaster by his son Henry Charles Malden.
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6,094 |
CPD
|
CPD may refer to:
==Organizations==
Centre for Policy Development, an Australian think tank
Centre for Policy Dialogue, Bangladesh
Centres of Plant Diversity, an international classification initiative
Commission on Presidential Debates, an American nonprofit
Committee on the Present Danger, an American foreign policy interest group
===Police===
Cambridge Police Department (Massachusetts)
Camden Police Department (New Jersey), a defunct police department dissolved in 2012
Carmel Police Department (Indiana)
Charleston Police Department (West Virginia)
Chattanooga Police Department, Tennessee
Chicago Police Department, Illinois
Cincinnati Police Department, Ohio
Cleveland Police Department, Ohio
Columbus Police Department, Ohio
Town of Carmel Police Department (New York)
==Science and technology==
CPD (gene), a human gene encoding the protein Carboxypeptidase D
Canonical polyadic decomposition, in mathematics
Cephalopelvic disproportion, when the capacity of the pelvis is inadequate to allow the fetus to negotiate the birth canal
Chronic pulmonary disease, a pathological condition
Conditional probability distribution, a kind of distribution in statistics
Copy/Paste Detector, software to find duplicate computer code
Cyclobutane pyrimidine dimer, a common UV product
Cyclopentadiene, an organic compound
Cyproterone acetate, a progestin and antiandrogen
==Other uses==
Camperdown railway station, Australia
Carnet de Passages en Douane, a customs document
Collaborative product development, in business
The Constitutional Practice and Discipline of the Methodist Church of Great Britain
Construction Products Directive, a repealed EU Directive
Continuing professional development
Danio margaritatus (also known as the Celestial Pearl Danio), a fish native to Southeast Asia
Coober Pedy Airport, IATA airport code
Crush protection device (CPD), an alternative to roll bar mandatory on all new Australian ATV's
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6,095 |
Chechnya
|
{{Infobox settlement
| name = Chechen Republic
| subdivision_type = Country
| settlement_type = Republic
| image_flag = Flag of Chechnya (large).svg
| image_map = Locator map of Chechnya, Russia (2014–2022).svg
| mapsize = 300px
| mapframe = yes
| mapframe-wikidata = yes
| mapframe-zoom = 6
| mapframe-height = 250
| mapframe-stroke-width = 1
| subdivision_name = Russia
| coordinates =
| coor_pinpoint =
| subdivision_type2 = Federal district
| subdivision_name2 = North Caucasian
| subdivision_type3 = Economic region
| subdivision_name3 = North Caucasus
| leader_title = Head
| leader_name = Ramzan Kadyrov
| total_type = Total
| area_total_sq_mi =
| area_total_km2 = 16,171
| population_rank = 31st
| population_density_km2 =
| population_as_of = 2021 Census
| population_total = 1,510,824
| population_footnotes =
| timezone1 = MSK
| blank_name = OKTMO ID
| blank_info = 26000000
| native_name =
| image_shield = Coat of arms of Chechnya.svg
| iso_code = RU-CE
| registration_plate = 95
| utc_offset = +03:00
| anthem = "Shatlak's Song"
| flag_size = 120px
| shield_size = 75px
| flag_link = Flag of Chechnya
| shield_link = Coat of arms of the Chechen Republic
| seat_type = Capital
| seat = Grozny
| population_urban = 38.2%
| population_rural = 61.8%
| blank_name_sec1 = Official language(s)
| blank_info_sec1 = Chechen
Russian
| area_footnotes =
| government_type = Parliament of the Chechen Republic Following the First Chechen War of 1994–1996 with Russia, Chechnya gained de facto independence as the Chechen Republic of Ichkeria, although de jure it remained a part of Russia. Russian federal control was restored in the Second Chechen War of 1999–2009, with Chechen politics being dominated by the former Ichkerian mufti Akhmad Kadyrov, and later his son Ramzan Kadyrov.
The republic covers an area of , with a population of over 1.5 million residents . It is home to the indigenous Chechens, part of the Nakh peoples, and of primarily Islamic faith. Grozny is the capital and largest city.
==History==
===Origin of Chechnya's population===
According to Leonti Mroveli, the 11th-century Georgian chronicler, the word "Caucasus" is derived from the Nakh ancestor Kavkas.
According to George Anchabadze of Ilia State University:
American linguist Johanna Nichols "has used language to connect the modern people of the Caucasus region to the ancient farmers of the Fertile Crescent" and her research suggests that "farmers of the region were proto-Nakh-Daghestanians". Nichols stated: "The Nakh–Dagestanian languages are the closest thing we have to a direct continuation of the cultural and linguistic community that gave rise to Western civilisation."
===Prehistory===
Traces of human settlement dating back to 40,000 BC were found near Lake Kezanoi. Cave paintings, artifacts, and other archaeological evidence indicate continuous habitation for some 8,000 years.
The Caucasian Epipaleolithic and early Caucasian Neolithic era saw the introduction of agriculture, irrigation, and the domestication of animals in the region. This period also saw the appearance of the wheel (3000 BC), horseback riding, metal works (copper, gold, silver, iron), dishes, armor, daggers, knives and arrow tips in the region. The artifacts were found near Nasare-Cort, Muzhichi, Ja-E-Bortz (alternatively known as Surkha-khi), Abbey-Gove (also known as Nazran or Nasare).
The 16th century saw the first Russian involvement in the Caucasus. In 1558, Temryuk of Kabarda sent his emissaries to Moscow requesting help from Ivan the Terrible against the Vainakh tribes. Ivan the Terrible married Temryuk's daughter Maria Temryukovna. An alliance was formed to gain the ground in the central Caucasus for the expanding Tsardom of Russia against Vainakh defenders.
In 1667 Mehk-Da Aldaman Gheza defended the borders of Chechnya from invasions of Kabardinians and Avars during the Battle of Khachara. The Chechens converted over the next few centuries to Sunni Islam, as Islam was associated with resistance to Russian encroachment.
===Imperial rule===
Russian Emperor Peter the Great first sought to increase Russia's political influence in the Caucasus and the Caspian Sea at the expense of Safavid Persia when he launched the Russo-Persian War of 1722–1723. Russian forces succeeded in taking much of the Caucasian territories from Persia for several years.
As the Imperial Russian Army took control of the Caspian corridor and moved into Persian-ruled Dagestan, Peter's forces ran into mountain tribes. Peter sent a cavalry force to subdue them, but the Chechens routed them. To increase its influence in the Caucasus and secure communication with Kartli and other Christian-inhabited regions of Transcaucasia, which it considered useful in its wars against Persia and the Ottoman Empire, the Russian Empire began conquering the Northern Caucasus mountains. The Russian Empire used Christianity to justify its conquests. This allowed Islam to spread widely among the Chechens, as it positioned itself as the religion of liberation from the Tsardom of Russia, which viewed Nakh tribes as "bandits".
After Persia was forced to cede the current territories of Dagestan, most of Azerbaijan, and Georgia to Russia following the Russo-Persian War of 1804–1813 and its resultant Treaty of Gulistan, Russia significantly widened its foothold in the Caucasus at Persia's expense. Another successful Caucasus war against Persia several years later, starting in 1826 and ending in 1828 with the Treaty of Turkmenchay, and a successful war against the Ottoman Empire in 1828–1829, enabled Russia to use a much larger portion of its army in subduing the natives of the North Caucasus.
The resistance of the Nakh tribes never ended and was a fertile ground for a new Muslim-Avar commander, Imam Shamil, who fought against the Russians from 1834 to 1859 (see Murid War). In 1859, Shamil was captured by the Russians at aul Gunib. Shamil left Baysangur of Benoa, a Chechen with one arm, one eye, and one leg, in charge of command at Gunib. Baysangur broke through the siege and continued to fight Russia for another two years until he was captured and killed by Russians. The Russian Tsar hoped that by sparing the life of Shamil, the resistance in the North Caucasus would stop, but it did not. Russia began to use a colonization tactic by destroying Nakh settlements and building Cossack defense lines in the lowlands. The Cossacks suffered defeat after defeat and were constantly attacked by mountaineers, who robbed them of food and weaponry.
The Russian Tsarist regime used a different approach at the end of the 1860s. They offered Chechens and Ingush to leave the Caucasus for the Ottoman Empire (see Muhajir (Caucasus)). It is estimated that about 80% of Chechens and Ingush left the Caucasus during the deportation. It weakened the resistance, which went from open warfare to insurgent warfare. One of the notable Chechen resistance fighters at the end of the 19th century was a Chechen abrek Zelimkhan Gushmazukaev and his comrade-in-arms Ingush abrek Sulom-Beck Sagopshinski. Together they built up small units which constantly harassed Russian military convoys, government mints, and the postal service, mainly in Ingushetia and Chechnya. Ingush aul Kek was completely burned when the Ingush refused to hand over Zelimkhan. Zelimkhan was killed at the beginning of the twentieth century. The war between Nakh tribes and Russia resurfaced during the times of the Russian Revolution, which saw the Nakh struggle against Anton Denikin and later against the Soviet Union.
On 21 December 1917, Ingushetia, Chechnya, and Dagestan declared independence from Russia and formed a single state: the United Mountain Dwellers of the North Caucasus, which was recognized by major world powers of the time. The capital of the new state was moved to Temir-Khan-Shura (today in Dagestan). Tapa Tchermoeff, a prominent Chechen statesman, was elected the first prime minister of the state. The second prime minister elected was Vassan-Girey Dzhabagiev, an Ingush statesman, who also was the author of the constitution of the republic in 1917, and in 1920 he was re-elected for the third term. In 1921 the Russians attacked and occupied the country and forcibly absorbed it into the Soviet state. The Caucasian war for independence restarted, and the government went into exile.
===Soviet rule===
Under the Soviet Union, Chechnya and Ingushetia were combined to form the Checheno-Ingush Autonomous Soviet Socialist Republic. In the 1930s, Chechnya was flooded with many Ukrainians fleeing a famine. As a result, many of the Ukrainians settled in Chechen-Ingush ASSR permanently and survived the famine. Although over 50,000 Chechens and over 12,000 Ingush were fighting against Nazi Germany on the front line (including Heroes of the USSR: Abukhadzhi Idrisov, Khanpasha Nuradilov, Movlid Visaitov), and although Nazi German troops advanced as far as the Ossetian ASSR city of Ordzhonikidze and the Chechen-Ingush ASSR city of Malgobek after capturing half of the Caucasus in less than a month, Chechens and Ingush were falsely accused as Nazi supporters and entire nations were deported during Operation Lentil to the Kazakh SSR (later Kazakhstan) in 1944 near the end of World War II where over 60% of Chechen and Ingush populations perished. American historian Norman Naimark writes:
The deportation was justified by the materials prepared by NKVD officer Bogdan Kobulov accusing Chechens and Ingush in a mass conspiracy preparing rebellion and providing assistance to the German forces. Many of the materials were later proven to be fabricated. Even distinguished Red Army officers who fought bravely against Germans (e.g. the commander of 255th Separate Chechen-Ingush regiment Movlid Visaitov, the first to contact American forces at Elbe river) were deported. There is a theory that the real reason why Chechens and Ingush were deported was the desire of Russia to attack Turkey, an anti-communist country, as Chechens and Ingush could impede such plans. In 2004, the European Parliament recognized the deportation of Chechens and Ingush as an act of genocide.
The territory of the Chechen-Ingush Autonomous Soviet Socialist Republic was divided between Stavropol Krai (where Grozny Okrug was formed), the Dagestan ASSR, the North Ossetian ASSR, and the Georgian SSR.
The Chechens and Ingush were allowed to return to their land after 1956 during de-Stalinisation under Nikita Khrushchev
With the impending dissolution of the Soviet Union in 1991, an independence movement, the Chechen National Congress, was formed, led by ex-Soviet Air Force general and new Chechen President Dzhokhar Dudayev. It campaigned for the recognition of Chechnya as a separate nation. This movement was opposed by Boris Yeltsin's Russian Federation, which argued that Chechnya had not been an independent entity within the Soviet Union—as the Baltic, Central Asian, and other Caucasian states such as Georgia had—but was part of the Russian Soviet Federative Socialist Republic and hence did not have a right under the Soviet constitution to secede. It also argued that other republics of Russia, such as Tatarstan, would consider seceding from the Russian Federation if Chechnya were granted that right. Finally, it argued that Chechnya was a major hub in the oil infrastructure of Russia and hence its secession would hurt the country's economy and energy access.
During the Chechen Revolution, the Soviet Chechen leader Doku Zavgayev was overthrown and Dzhokhar Dudayev seized power. On 1 November 1991, Dudaev's Chechnya issued a unilateral declaration of independence. In the ensuing decade, the territory was locked in an ongoing struggle between various factions, usually fighting unconventionally.
===Chechen Wars and brief independence===
The First Chechen War, during which Russian forces attempted to regain control over Chechnya, took place from 1994 to 1996. Despite overwhelming numerical superiority in troops, weaponry, and air support, the Russian forces were unable to establish effective permanent control over the mountainous area due to numerous successful full-scale battles and insurgency raids. The Budyonnovsk hospital hostage crisis in 1995 shocked the Russian public. In April 1996, the first democratically elected president of Chechnya, Dzhokhar Dudayev, was killed by Russian forces using a booby trap bomb and a missile fired from a warplane after he was located by triangulating the position of a satellite phone he was using.
The widespread demoralisation of the Russian Army in the area and a successful offensive to retake Grozny by Chechen rebel forces led by Aslan Maskhadov prompted Russian President Boris Yeltsin to declare a ceasefire in 1996, and sign a peace treaty a year later that saw a withdrawal of Russian troops.
After the war, parliamentary and presidential elections took place in January 1997 in Chechnya and brought to power new President Aslan Maskhadov, chief of staff and prime minister in the Chechen coalition government, for a five-year term. Maskhadov sought to maintain Chechen sovereignty while pressing the Russian government to help rebuild the republic, whose formal economy and infrastructure were virtually destroyed. Russia continued to send money for the rehabilitation of the republic; it also provided pensions and funds for schools and hospitals. Nearly half a million people (40% of Chechnya's prewar population) had been internally displaced and lived in refugee camps or overcrowded villages. There was an economic downturn. Two Russian brigades were permanently stationed in Chechnya. although victims were rarely killed. In 1998, 176 people were kidnapped, 90 of whom were released, according to official accounts. President Maskhadov started a major campaign against hostage-takers, and on 25 October 1998, Shadid Bargishev, Chechnya's top anti-kidnapping official, was killed in a remote-controlled car bombing. Bargishev's colleagues then insisted they would not be intimidated by the attack and would go ahead with their offensive. Political violence and religious extremism, blamed on Salafism and Wahhabism, was rife. In 1998, Grozny authorities declared a state of emergency. Tensions led to open clashes between the Chechen National Guard and Islamist militants, such as the July 1998 confrontation in Gudermes.
The War of Dagestan began on 7 August 1999, during which the Islamic International Peacekeeping Brigade (IIPB) began an unsuccessful incursion into the neighboring Russian republic of Dagestan in favor of the Shura of Dagestan, which sought independence from Russia. In September, a series of apartment bombings that killed around 300 people in several Russian cities, including Moscow, were blamed on Chechen separatists. In response to the bombings, a prolonged air campaign of retaliatory strikes against the Ichkerian regime and a ground offensive that began in October 1999 marked the beginning of the Second Chechen War. Much better organized and planned than the First Chechen War, the Russian armed forces took control of most regions. The Russian forces used brutal force, killing 60 Chechen civilians during a mop-up operation in Aldy, Chechnya on 5 February 2000. After the re-capture of Grozny in February 2000, the Ichkerian regime fell apart.
File:Evstafiev-chechnya-prayer3.jpg|A Chechen man prays during the Battle of Grozny.
File:Djokhar Doudaïev.jpg|Dzhokhar Dudayev
File:Aslan Maskhadov.jpg|Aslan Maskhadov
File:Cadets of the Ichkeria Chechen national guard 1999.jpg|Cadets of the Ichkeria Chechen national guard, 1999.
File:Evstafiev-chechnya-palace-gunman.jpg|A Chechen fighter stands near the government palace building during a short lull in fighting in Grozny, Chechnya.
===Post-war reconstruction and insurgency===
Chechen separatists continued to fight Russian troops and conduct terror attacks after the occupation of Grozny. In October 2002, 40–50 Chechen rebels seized a Moscow theater and took about 900 civilians hostage.
In response to these attacks, Russia tightened its grip on Chechnya and expanded its anti-terrorist operations throughout the region. Russia installed a pro-Russian Chechen regime. In 2003, a referendum was held on a constitution that reintegrated Chechnya within Russia but provided limited autonomy. According to the Chechen government, the referendum passed with 95.5% of the votes and almost 80% turnout. The Economist was skeptical of the results, arguing that "few outside the Kremlin regard the referendum as fair".
In September 2004, separatist rebels occupied a school in the town of Beslan, North Ossetia, demanding recognition of the independence of Chechnya and a Russian withdrawal. 1,100 people (including 777 children) were taken hostage. The attack lasted three days, resulting in the deaths of over 331 people, including 186 children. After the 2004 school siege, Russian President Vladimir Putin announced sweeping security and political reforms, sealing borders in the Caucasus region and revealing plans to give the central government more power. He also vowed to take tougher action against domestic terrorism, including preemptive strikes against Chechen separatists. Kadyrov's rule has been characterized by high-level corruption, a poor human rights record, widespread use of torture, and a growing cult of personality. Allegations of anti-gay purges in Chechnya were initially reported on 1 April 2017.
In April 2009, Russia ended its counter-terrorism operations and pulled out the bulk of its army. The insurgency in the North Caucasus continued even after this date. The Caucasus Emirate had fully adopted the tenets of a Salafi-jihadist group through its strict adherence to the Sunni Hanbali obedience to the literal interpretation of the Quran and the Sunnah.
The Chechen government has been outspoken in its support for the 2022 Russian invasion of Ukraine, where a Chechen military force, the Kadyrovtsy, which is under Kadyrov's personal command, has played a leading role, notably in the Siege of Mariupol. Meanwhile, a substantial number of Chechen separatists have allied themselves to the Ukrainian cause and are fighting a mutual Russian enemy in the Donbas.
On March 2025, Chechnya blocked Telegram app due to concerns that it could be used by "enemies".
==Geography==
Situated in the eastern part of the North Caucasus in Eastern Europe, Chechnya is surrounded on nearly all sides by Russian Federal territory. In the west, it borders North Ossetia and Ingushetia, in the north, Stavropol Krai, in the east, Dagestan, and to the south, Georgia. Its capital is Grozny. Chechnya is well known for being mountainous, but it is in fact split between the more flat areas north of the Terek, and the highlands south of the Terek.
Area:
Borders:
Internal:
Dagestan (NE)
Ingushetia (W)
North Ossetia–Alania (W)
Stavropol Krai (NW)
Foreign:
Georgia (Kakheti and Mtskheta-Mtianeti) (S)
Rivers:
Terek
Sunzha
Argun
===Climate===
Despite a relatively small territory, Chechnya is characterized by a variety of climate conditions. The average temperature in Grozny is .
===Cities and towns with over 20,000 people===
Grozny (capital)
Shali
Urus-Martan
Gudermes
Argun
Kurchaloy
Achkoy-Martan
==Administrative divisions==
The Chechen Republic is divided into 15 districts and three cities of republican significance.
==Demographics==
According to the 2021 Census, the population of the republic is 1,510,824, As of the 2021 Census, Chechens at 1,456,792 make up 96.4% of the republic's population. Other groups include Russians (18,225, or 1.2%), Kumyks (12,184, or 0.8%) and a host of other small groups, each accounting for less than 0.5% of the total population. The birth rate was 25.41 in 2004. (25.7 in Achkhoi Martan, 19.8 in Groznyy, 17.5 in Kurchaloi, 28.3 in Urus Martan and 11.1 in Vedeno).
The languages used in the Republic are Chechen and Russian. Chechen belongs to the Vaynakh or North-central Caucasian language family, which also includes Ingush and Batsb. Some scholars place it in a wider North Caucasian languages.
===Life expectancy===
Despite its difficult past, Chechnya has a high life expectancy, one of the highest in Russia. But the pattern of life expectancy is unusual, and in according to numerous statistics, Chechnya stands out from the overall picture. In 2020, Chechnya had the deepest fall in life expectancy, but in 2021 it had the biggest rise. Chechnya has the highest excess of life expectancy in rural areas over cities.
File:Life expectancy in Russian subject -Chechnya.png|Life expectancy at birth in Chechnya
File:Life expectancy in Russian subject -Chechnya -diff.png|Life expectancy with calculated differences
File:Life expectancy in Russia -Chechnya.png|Life expectancy in Chechnya in comparison with neighboring regions of the country
File:Comparison of life expectancy in Russian subjects by sex.svg|Interactive chart of comparison of male and female life expectancy for 2021. Open the original svg-file in a separate window and hover over a bubble to highlight it.
File:Comparison of life expectancy in Russian subjects by type of settlement.svg|Analogious interactive chart of comparison of urban and rural life expectancy.Original interactive file.
===Settlements===
===Vital statistics===
===Ethnic groups===
(In the territory of modern Chechnya)
===Religion===
====Islam====
Sunni Islam is the predominant religion in Chechnya, practiced by 95% of those polled in Grozny in 2010. Most of the population is Sunni and follows either the Shafi'i or the Hanafi schools of Islamic jurisprudence. The Shafi'i school of jurisprudence has a long tradition among the Chechens, and thus it remains the most practiced. Many Chechens are also Sufis, of either the Qadiri or Naqshbandi orders. A supreme Islamic administrative territorial organisation in Chechnya is the Spiritual Administration of the Muslims of the Chechen Republic or the Muftiate of the Chechen Republic. As of 2020, there are eight Eastern Orthodox churches in Chechnya, the largest is the temple of the Archangel Michael in Grozny.
==Politics==
Since 1990, the Chechen Republic has had many legal, military, and civil conflicts involving separatist movements and pro-Russian authorities. Chechnya has enjoyed a period of relative stability under the Russian-appointed government, although there is still some separatist movement activity. Its regional constitution entered into effect on 2 April 2003, after an all-Chechen referendum was held on 23 March 2003. Some Chechens were controlled by regional teips, or clans, despite the existence of pro- and anti-Russian political structures.
In the 2024 Russian presidential election, which critics called rigged and fraudulent, Russian President Vladimir Putin won 98.99% of the vote in Chechnya.
===Regional government===
The former separatist religious leader (mufti) Akhmad Kadyrov was elected president with 83% of the vote in an internationally monitored election on 5 October 2003. Incidents of ballot stuffing and voter intimidation by Russian soldiers and the exclusion of separatist parties from the polls were subsequently reported by Organization for Security and Co-operation in Europe (OSCE) monitors. On 9 May 2004, Kadyrov was assassinated in Grozny football stadium by a landmine explosion that was planted beneath a VIP stage and detonated during a parade, and Sergey Abramov was appointed acting prime minister after the incident. However, since 2005 Ramzan Kadyrov (son of Akhmad Kadyrov) has been the caretaker prime minister, and in 2007 was appointed as the new president. Many allege he is the wealthiest and most powerful man in the republic, with control over a large private militia (the Kadyrovites). The militia, which began as his father's security force, has been accused of killings and kidnappings by human rights organisations such as Human Rights Watch.
===Separatist government===
Ichkeria was a member of the Unrepresented Nations and Peoples Organisation between 1991 and 2010. Former president of Georgia, Zviad Gamsakhurdia, deposed in a military coup of 1991 and a participant of the Georgian Civil War, recognized the independence of the Chechen Republic of Ichkeria in 1993. Diplomatic relations with Ichkeria were also established by the partially recognised Islamic Emirate of Afghanistan under the Taliban government on 16 January 2000. This recognition ceased with the fall of the Taliban in 2001. However, despite Taliban recognition, there were no friendly relations between the Taliban and Ichkeria—Maskhadov rejected their recognition, stating that the Taliban were illegitimate. Ichkeria also received vocal support from the Baltic countries, a group of Ukrainian nationalists, and Poland; Estonia once voted to recognize, but the act never was followed through due to pressure applied by both Russia and the EU.
The president of this government was Aslan Maskhadov, and the foreign minister was Ilyas Akhmadov, who was the spokesman for the president. Maskhadov had been elected for four years in an internationally monitored election in 1997, which took place after signing a peace agreement with Russia. In 2001, he issued a decree prolonging his office for one additional year; he was unable to participate in the 2003 presidential election since separatist parties were barred by the Russian government, and Maskhadov faced accusations of terrorist offenses in Russia. Maskhadov left Grozny and moved to the separatist-controlled areas of the south at the onset of the Second Chechen War. Maskhadov was unable to influence a number of warlords who retain effective control over Chechen territory, and his power was diminished as a result. Russian forces killed Maskhadov on 8 March 2005, and the assassination was widely criticized since it left no legitimate Chechen separatist leader with whom to conduct peace talks. Akhmed Zakayev, deputy prime minister and a foreign minister under Maskhadov, was appointed shortly after the 1997 election and is currently living under asylum in England. He and others chose Abdul Khalim Saidullayev, a relatively unknown Islamic judge who was previously the host of an Islamic program on Chechen television, to replace Maskhadov following his death. On 17 June 2006, it was reported that Russian special forces killed Abdul Khalim Saidullayev in a raid in the Chechen town of Argun. On 10 July 2006, Shamil Basayev, a leader of the Chechen rebel movement, was killed in a truck explosion during an arms deal.
The successor of Saidullayev became Doku Umarov. On 31 October 2007, Umarov abolished the Chechen Republic of Ichkeria and its presidency and in its place proclaimed the Caucasus Emirate with himself as its Emir. This change of status has been rejected by many Chechen politicians and military leaders who continue to support the existence of the republic.
During the 2022 Russian invasion of Ukraine, the Ukrainian parliament voted to recognize the "Chechen Republic of Ichkeria as territory temporarily occupied by the Russian Federation".
==Human rights==
Тhe Internal Displacement Monitoring Center reports that after hundreds of thousands of ethnic Russians and Chechens fled their homes following inter-ethnic and separatist conflicts in Chechnya in 1994 and 1999, more than 150,000 people still remain displaced in Russia today.
Нuman rights organizations criticized the conduct of the 2005 parliamentary elections as unfairly influenced by the central Russian government and military. In 2006, Human Rights Watch reported that pro-Russian Chechen forces under the command of Ramzan Kadyrov, as well as Russian federal police personnel, used torture to get information about separatist forces. "If you are detained in Chechnya, you face a real and immediate risk of torture. And there is little chance that your torturer will be held accountable", said Holly Cartner, Director of the Europe and Central Asia division of the Human Rights Watch.
In 2009, the U. S. government-financed American organization Freedom House included Chechnya in the "Worst of the Worst" list of most repressive societies in the world, together with Burma, North Korea, Tibet, and others. Memorial considers Chechnya under Kadyrov to be a totalitarian regime.
On February 1 2009, The New York Times released extensive evidence to support allegations of consistent torture and executions under the Kadyrov government. The accusations were sparked by the assassination in Austria of a former Chechen rebel who had gained access to Kadyrov's inner circle, 27-year-old Umar Israilov.
On July 1 2009, Amnesty International released a detailed report covering the human rights violations committed by the Russian Federation against Chechen citizens. Among the most prominent features was that those abused had no method of redress against assaults, ranging from kidnapping to torture, while those responsible were never held accountable. This led to the conclusion that Chechnya was being ruled without law, being run into further devastating destabilization.
On 10 March 2011, Human Rights Watch reported that since Chechenization, the government has pushed for enforced Islamic dress code. The president Ramzan Kadyrov is quoted as saying "I have the right to criticize my wife. She doesn't [have the right to criticize me]. With us [in Chechen society], a wife is a housewife. A woman should know her place. A woman should give her love to us [men]... She would be [man's] property. And the man is the owner. Here, if a woman does not behave properly, her husband, father, and brother are responsible. According to our tradition, if a woman fools around, her family members kill her... That's how it happens, a brother kills his sister or a husband kills his wife... As a president, I cannot allow for them to kill. So, let women not wear shorts...". He has also openly defended honor killings on several occasions.
On 9 July 2017, Russian newspaper reported that a number of people were extrajudicially executed on the night of 26 January 2017. It published a list of 27 names of the people known to be dead, but stressed that the list is "not all [of those killed]"; the newspaper asserted that 50 people may have been executed. Some of the dead were gay, but not all. The killings appeared to have been precipitated by the death of a policeman;
In December 2021, up to 50 family members of critics of the Kadyrov government were abducted in a wave of mass kidnappings beginning on 22 December. In a case-study published during the same year, Freedom House reported that Kadyrov also conducts a total transnational repression campaign against Chechen exiles outside of Russia, including assassinations of critics and digital intimidation.
===LGBT rights===
Although homosexuality is officially legal in Chechnya per Russian law, it is de facto illegal. Chechen authorities have reportedly arrested, imprisoned and killed persons based on their perceived sexual orientation.
In 2017, it was reported by and human rights groups that Chechen authorities had set up concentration camps, one of which is in Argun, where gay men are interrogated and subjected to physical violence. On 27 June 2018, the Parliamentary Assembly of the Council of Europe noted "cases of abduction, arbitrary detention, and torture ... with the direct involvement of Chechen law enforcement officials and on the orders of top-level Chechen authorities" and expressed dismay "at the statements of Chechen and Russian public officials denying the existence of LGBTI people in the Chechen Republic". In a 2021 Council of Europe report into anti-LGBTI hate-crimes, rapporteur Foura ben Chikha described the "state-sponsored attacks carried out against LGBTI people in Chechnya in 2017" as "the single most egregious example of violence against LGBTI people in Europe that has occurred in decades".
On 11 January 2019, it was reported that another "gay purge" had begun in the country in December 2018, with several men and women being detained. The Russian LGBT Network believes that around 40 people were detained and two killed.
==Economy==
During the First Chechen War, the Chechen economy fell apart. In 1994, the separatists planned to introduce a new currency, but the change did not occur due to the re-taking of Chechnya by Russian troops in the Second Chechen War.
Chechnya's unemployment was 67% in 2006 and fell to 21.5% in 2014.
Total revenue of the budget of Chechnya for 2017 was 59.2 billion rubles. Of these, 48.5 billion rubles were grants from the federal budget of the Russian Federation.
In late 1970s, Chechnya produced up to 20 million tons of oil annually, production declined sharply to approximately 3 million tons in the late 1980s, and to below 2 million tons before 1994, first (1994–1996) second Russian invasion of Chechnya (1999) inflicted material damage on the oil-sector infrastructure, oil production decreased to 750,000 tons in 2001 only to increase to 2 million tons in 2006, by 2012 production was 1 million tons.
==Culture==
The culture of Chechnya is based on the native traditions of Chechen people. Chechen mythology along with art have helped shape the culture for over 1,000 years.
From April 2024, all music must have a tempo between 80 and 116 beats per minute, to comply with Chechen traditions. Borrowing musical culture from other peoples is not allowed.
|
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] |
6,097 |
Canonization
|
Canonization is the declaration of a deceased person as an officially recognized saint, specifically, the official act of a Christian communion declaring a person worthy of public veneration and entering their name in the canon catalogue of saints, or authorized list of that communion's recognized saints.
==Catholic Church==
Canonization is a papal declaration that the Catholic faithful may venerate a particular deceased member of the church. Popes began making such decrees in the tenth century. Up to that point, the local bishops governed the veneration of holy men and women within their own dioceses; and there may have been, for any particular saint, no formal decree at all. In subsequent centuries, the procedures became increasingly regularized and the Popes began restricting to themselves the right to declare someone a Catholic saint. In contemporary usage, the term is understood to refer to the act by which any Christian church declares that a person who has died is a saint, upon which declaration the person is included in the list of recognized saints, called the "canon".
=== Biblical roots ===
In the Roman Martyrology, the following entry is given for the Penitent Thief: "At Jerusalem, the commemoration of the good Thief, who confessed Christ on the cross, and deserved to hear from Him these words: 'This day thou shalt be with Me in paradise.'
=== Historical development ===
The Roman Canon, the historical Eucharistic Prayer or Anaphora of Canon of the Roman Rite contains only the names of apostles and martyrs, along with that of the Blessed Virgin Mary and, since 1962, that of Saint Joseph her spouse.
By the fourth century, however, "confessors"—people who had confessed their faith not by dying but by word and life—began to be venerated publicly. Examples of such people are Saint Hilarion and Saint Ephrem the Syrian in the East, and Saint Martin of Tours and Saint Hilary of Poitiers in the West. Their names were inserted in the diptychs, the lists of saints explicitly venerated in the liturgy, and their tombs were honoured in like manner as those of the martyrs. Since the witness of their lives was not as unequivocal as that of the martyrs, they were venerated publicly only with the approval by the local bishop. This process is often referred to as "local canonization".
This approval was required even for veneration of a reputed martyr. In his history of the Donatist heresy, Saint Optatus recounts that at Carthage a Catholic matron, named Lucilla, incurred the censures of the Church for having kissed the relics of a reputed martyr whose claims to martyrdom had not been juridically proved. And Saint Cyprian (died 258) recommended that the utmost diligence be observed in investigating the claims of those who were said to have died for the faith. All the circumstances accompanying the martyrdom were to be inquired into; the faith of those who suffered, and the motives that animated them were to be rigorously examined, in order to prevent the recognition of undeserving persons. Evidence was sought from the court records of the trials or from people who had been present at the trials.
Augustine of Hippo (died 430) tells of the procedure which was followed in his day for the recognition of a martyr. The bishop of the diocese in which the martyrdom took place set up a canonical process for conducting the inquiry with the utmost severity. The acts of the process were sent either to the metropolitan or primate, who carefully examined the cause, and, after consultation with the suffragan bishops, declared whether the deceased was worthy of the name of "martyr" and public veneration.
Though not "canonizations" in the narrow sense, acts of formal recognition, such as the erection of an altar over the saint's tomb or transferring the saint's relics to a church, were preceded by formal inquiries into the sanctity of the person's life and the miracles attributed to that person's intercession.
Such acts of recognition of a saint were authoritative, in the strict sense, only for the diocese or ecclesiastical province for which they were issued, but with the spread of the fame of a saint, were often accepted elsewhere also.
=== Nature ===
In the Catholic Church, both in the Latin and the constituent Eastern churches, the act of canonization is reserved to the Apostolic See and occurs at the conclusion of a long process requiring extensive proof that the candidate for canonization lived and died in such an exemplary and holy way that they are worthy to be recognized as a saint. The Church's official recognition of sanctity implies that the person is now in Heaven and that they may be publicly invoked and mentioned officially in the liturgy of the Church, including in the Litany of the Saints.
In the Catholic Church, canonization is a decree that allows universal veneration of the saint. For permission to venerate merely locally, only beatification is needed.
=== Procedure prior to reservation to the Apostolic See ===
For several centuries the bishops, or in some places only the primates and patriarchs, could grant martyrs and confessors public ecclesiastical honor; such honor, however, was always decreed only for the local territory of which the grantors had jurisdiction. Only acceptance of the cultus by the Pope made the cultus universal, because he alone can rule the universal Catholic Church. Abuses, however, crept into this discipline, due as well to indiscretions of popular fervor as to the negligence of some bishops in inquiring into the lives of those whom they permitted to be honoured as saints.
In the Medieval West, the Apostolic See was asked to intervene in the question of canonizations so as to ensure more authoritative decisions. The canonization of Saint Udalric, Bishop of Augsburg by Pope John XV in 993 was the first undoubted example of papal canonization of a saint from outside of Rome being declared worthy of liturgical veneration for the entire church.
Thereafter, recourse to the judgment of the Pope occurred more frequently. Toward the end of the 11th century, the Popes began asserting their exclusive right to authorize the veneration of a saint against the older rights of bishops to do so for their dioceses and regions. Popes therefore decreed that the virtues and miracles of persons proposed for public veneration should be examined in councils, more specifically in general councils. Pope Urban II, Pope Calixtus II, and Pope Eugene III conformed to this discipline.
=== Exclusive reservation to the Apostolic See ===
Hugh de Boves, Archbishop of Rouen, canonized Walter of Pontoise, or St. Gaultier, in 1153, the final saint in Western Europe to be canonized by an authority other than the Pope: "The last case of canonization by a metropolitan is said to have been that of St. Gaultier, or Gaucher, [A]bbot of Pontoise, by the Archbishop of Rouen. A decree of Pope Alexander III [in] 1170 gave the prerogative to the [P]ope thenceforth, so far as the Western Church was concerned." Theologians disagree as to the full import of the decretal of Pope Alexander III: either a new law was instituted, in which case the Pope then for the first time reserved the right of beatification to himself, or an existing law was confirmed.
However, the procedure initiated by the decretal of Pope Alexander III was confirmed by a bull of Pope Innocent III issued on the occasion of the canonization of Cunigunde of Luxembourg in 1200. The bull of Pope Innocent III resulted in increasingly elaborate inquiries to the Apostolic See concerning canonizations. Because the decretal of Pope Alexander III did not end all controversy and some bishops did not obey it in so far as it regarded beatification, the right of which they had certainly possessed hitherto, Pope Urban VIII issued the Apostolic letter Caelestis Hierusalem cives of 5 July 1634 that exclusively reserved to the Apostolic See both its immemorial right of canonization and that of beatification. He further regulated both of these acts by issuing his Decreta servanda in beatificatione et canonizatione Sanctorum on 12 March 1642.
=== Procedure from 1734 to 1738 to 1983 ===
In his De Servorum Dei beatificatione et de Beatorum canonizatione of five volumes the eminent canonist Prospero Lambertini (1675–1758), who later became Pope Benedict XIV, elaborated on the procedural norms of Pope Urban VIII's Apostolic letter Caelestis Hierusalem cives of 1634 and Decreta servanda in beatificatione et canonizatione Sanctorum of 1642, and on the conventional practice of the time. His work published from 1734 to 1738 governed the proceedings until 1917. The article "Beatification and canonization process in 1914" describes the procedures followed until the promulgation of the Codex of 1917. The substance of De Servorum Dei beatifιcatione et de Beatorum canonizatione was incorporated into the Codex Iuris Canonici (Code of Canon Law) of 1917, which governed until the promulgation of the revised Codex Iuris Canonici in 1983 by Pope John Paul II. Prior to promulgation of the revised Codex in 1983, Pope Paul VI initiated a simplification of the procedures.
=== Since 1983 ===
The Apostolic constitution Divinus Perfectionis Magister of Pope John Paul II of 25 January 1983 and the norms issued by the Congregation for the Causes of Saints on 7 February 1983 to implement the constitution in dioceses, continued the simplification of the process initiated by Pope Paul VI.
Candidates for canonization undergo the following process:
Canonization is a statement of the Church that the person certainly enjoys the beatific vision of Heaven. The title of "Saint" (Latin: Sanctus or Sancta) is then proper, reflecting that the saint is a refulgence of the holiness (sanctitas) of God himself, which alone comes from God's gift. The saint is assigned a feast day which may be celebrated anywhere in the universal Church, although it is not necessarily added to the General Roman Calendar or local calendars as an "obligatory" feast; parish churches may be erected in their honor; and the faithful may freely celebrate and honor the saint.
Although recognition of sainthood by the Pope does not directly concern a fact of Divine revelation, nonetheless it must be "definitively held" by the faithful as infallible pursuant to, at the least, the Universal Magisterium of the Church, because it is a truth related to revelation by historical necessity.
=== Equipollent canonization ===
Popes have several times permitted to the universal Church, without executing the ordinary judicial process of canonization described above, the veneration as a saint, the "cultus" of one long venerated as such locally. This act of a Pope is denominated "equipollent" or "equivalent canonization" and "confirmation of cultus". In such cases, there is no need to have a miracle attributed to the saint to allow their canonization.
=== United Methodist Church ===
The General Conference of the United Methodist Church has formally declared individuals martyrs, including Dietrich Bonhoeffer (in 2008) and Martin Luther King Jr. (in 2012).
== Eastern Orthodox Church ==
Various terms are used for canonization by the autocephalous Eastern Orthodox Churches: канонизация ("canonization") or прославление ("glorification", in the Russian Orthodox Church), კანონიზაცია (kanonizats’ia, Georgian Orthodox Church), канонизација (Serbian Orthodox Church), canonizare (Romanian Orthodox Church), and Канонизация (Bulgarian Orthodox Church). Additional terms are used for canonization by other autocephalous Eastern Orthodox Churches: (Katharevousa: ) agiokatataxi/agiokatataxis, "ranking among saints" (Ecumenical Patriarchate of Constantinople, Church of Cyprus, Church of Greece), kanonizim (Albanian Orthodox Church), kanonizacja (Polish Orthodox Church), and kanonizace/kanonizácia (Czech and Slovak Orthodox Church).
The Orthodox Church in America, an Eastern Orthodox Church partly recognized as autocephalous, uses the term "glorification" for the official recognition of a person as a saint.
== Oriental Orthodox Church ==
Within the Armenian Apostolic Church, part of Oriental Orthodoxy, there had been discussions since the 1980s about canonizing the victims of the Armenian genocide. On 23 April 2015, all of the victims of the genocide were canonized.
|
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6,099 |
Carboxylic acid
|
In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is often written as ' or ', sometimes as with R referring to an organyl group (e.g., alkyl, alkenyl, aryl), or hydrogen, or other groups. Carboxylic acids occur widely. Important examples include the amino acids and fatty acids. Deprotonation of a carboxylic acid gives a carboxylate anion.
==Examples and nomenclature==
Carboxylic acids are commonly identified by their trivial names. They often have the suffix -ic acid. IUPAC-recommended names also exist; in this system, carboxylic acids have an -oic acid suffix. For example, butyric acid () is butanoic acid by IUPAC guidelines. For nomenclature of complex molecules containing a carboxylic acid, the carboxyl can be considered position one of the parent chain even if there are other substituents, such as 3-chloropropanoic acid. Alternately, it can be named as a "carboxy" or "carboxylic acid" substituent on another parent structure, such as 2-carboxyfuran.
The carboxylate anion ( or ) of a carboxylic acid is usually named with the suffix -ate, in keeping with the general pattern of -ic acid and -ate for a conjugate acid and its conjugate base, respectively. For example, the conjugate base of acetic acid is acetate.
Carbonic acid, which occurs in bicarbonate buffer systems in nature, is not generally classed as one of the carboxylic acids, despite that it has a moiety that looks like a COOH group.
==Physical properties==
===Solubility===
Carboxylic acids are polar. Because they are both hydrogen-bond acceptors (the carbonyl ) and hydrogen-bond donors (the hydroxyl ), they also participate in hydrogen bonding. Together, the hydroxyl and carbonyl group form the functional group carboxyl. Carboxylic acids usually exist as dimers in nonpolar media due to their tendency to "self-associate". Smaller carboxylic acids (1 to 5 carbons) are soluble in water, whereas bigger carboxylic acids have limited solubility due to the increasing hydrophobic nature of the alkyl chain. These longer chain acids tend to be soluble in less-polar solvents such as ethers and alcohols. Aqueous sodium hydroxide and carboxylic acids, even hydrophobic ones, react to yield water-soluble sodium salts. For example, enanthic acid has a low solubility in water (0.2 g/L), but its sodium salt is very soluble in water.
===Boiling points===
Carboxylic acids tend to have higher boiling points than water, because of their greater surface areas and their tendency to form stabilized dimers through hydrogen bonds. For boiling to occur, either the dimer bonds must be broken or the entire dimer arrangement must be vaporized, increasing the enthalpy of vaporization requirements significantly.
===Acidity===
Carboxylic acids are Brønsted–Lowry acids because they are proton (H+) donors. They are the most common type of organic acid.
Carboxylic acids are typically weak acids, meaning that they only partially dissociate into Hydronium| cations and Carboxylate| anions in neutral aqueous solution. For example, at room temperature, in a 1-molar solution of acetic acid, only 0.001% of the acid are dissociated (i.e. 10−5 moles out of 1 mol). Electron-withdrawing substituents such as trifluoromethyl () give stronger acids (the pKa of acetic acid is 4.76 whereas trifluoroacetic acid, with a trifluoromethyl substituent, has a pKa of 0.23). Electron-donating substituents give weaker acids (the pKa of formic acid is 3.75 whereas acetic acid, with a methyl substituent, has a pKa of 4.76)
Deprotonation of carboxylic acids gives carboxylate anions; these are resonance stabilized, because the negative charge is delocalized over the two oxygen atoms, increasing the stability of the anion. Each of the carbon–oxygen bonds in the carboxylate anion has a partial double-bond character. The carbonyl carbon's partial positive charge is also weakened by the −1/2 negative charges on the 2 oxygen atoms.
===Odour===
Carboxylic acids often have strong sour odours. Esters of carboxylic acids tend to have fruity, pleasant odours, and many are used in perfume.
=== Characterization ===
Carboxylic acids are readily identified as such by infrared spectroscopy. They exhibit a sharp band associated with vibration of the C=O carbonyl bond (νC=O) between 1680 and 1725 cm−1. A characteristic νO–H band appears as a broad peak in the 2500 to 3000 cm−1 region. By 1H NMR spectrometry, the hydroxyl hydrogen appears in the 10–13 ppm region, although it is often either broadened or not observed owing to exchange with traces of water.
==Occurrence and applications==
Many carboxylic acids are produced industrially on a large scale. They are also frequently found in nature. Esters of fatty acids are the main components of lipids and polyamides of aminocarboxylic acids are the main components of proteins.
Carboxylic acids are used in the production of polymers, pharmaceuticals, solvents, and food additives. Industrially important carboxylic acids include acetic acid (component of vinegar, precursor to solvents and coatings), acrylic and methacrylic acids (precursors to polymers, adhesives), adipic acid (polymers), citric acid (a flavor and preservative in food and beverages), ethylenediaminetetraacetic acid (chelating agent), fatty acids (coatings), maleic acid (polymers), propionic acid (food preservative), terephthalic acid (polymers). Important carboxylate salts are soaps.
==Synthesis==
===Industrial routes===
In general, industrial routes to carboxylic acids differ from those used on a smaller scale because they require specialized equipment.
Carbonylation of alcohols as illustrated by the Cativa process for the production of acetic acid. Formic acid is prepared by a different carbonylation pathway, also starting from methanol.
Oxidation of aldehydes with air using cobalt and manganese catalysts. The required aldehydes are readily obtained from alkenes by hydroformylation.
Oxidation of hydrocarbons using air. For simple alkanes, this method is inexpensive but not selective enough to be useful. Allylic and benzylic compounds undergo more selective oxidations. Alkyl groups on a benzene ring are oxidized to the carboxylic acid, regardless of its chain length. Benzoic acid from toluene, terephthalic acid from para-xylene, and phthalic acid from ortho-xylene are illustrative large-scale conversions. Acrylic acid is generated from propene.
Oxidation of ethene using silicotungstic acid catalyst.
Base-catalyzed dehydrogenation of alcohols.
Carbonylation coupled to the addition of water. This method is effective and versatile for alkenes that generate secondary and tertiary carbocations, e.g. isobutylene to pivalic acid. In the Koch reaction, the addition of water and carbon monoxide to alkenes or alkynes is catalyzed by strong acids. Hydrocarboxylations involve the simultaneous addition of water and CO. Such reactions are sometimes called "Reppe chemistry."
Hydrolysis of triglycerides obtained from plant or animal oils. These methods of synthesizing some long-chain carboxylic acids are related to soap making.
Fermentation of ethanol. This method is used in the production of vinegar.
The Kolbe–Schmitt reaction provides a route to salicylic acid, precursor to aspirin.
===Laboratory methods===
Preparative methods for small scale reactions for research or for production of fine chemicals often employ expensive consumable reagents.
Oxidation of primary alcohols or aldehydes with strong oxidants such as potassium dichromate, Jones reagent, potassium permanganate, or sodium chlorite. The method is more suitable for laboratory conditions than the industrial use of air, which is "greener" because it yields less inorganic side products such as chromium or manganese oxides.
Oxidative cleavage of olefins by ozonolysis, potassium permanganate, or potassium dichromate.
Hydrolysis of nitriles, esters, or amides, usually with acid- or base-catalysis.
Carbonation of a Grignard reagent and organolithium reagents:
Halogenation followed by hydrolysis of methyl ketones in the haloform reaction
Base-catalyzed cleavage of non-enolizable ketones, especially aryl ketones:
===Less-common reactions===
Many reactions produce carboxylic acids but are used only in specific cases or are mainly of academic interest.
Disproportionation of an aldehyde in the Cannizzaro reaction
Rearrangement of diketones in the benzilic acid rearrangement
Involving the generation of benzoic acids are the von Richter reaction from nitrobenzenes and the Kolbe–Schmitt reaction from phenols.
==Reactions==
===Acid-base reactions===
Carboxylic acids react with bases to form carboxylate salts, in which the hydrogen of the hydroxyl (–OH) group is replaced with a metal cation. For example, acetic acid found in vinegar reacts with sodium bicarbonate (baking soda) to form sodium acetate, carbon dioxide, and water:
===Conversion to esters, amides, anhydrides===
Widely practiced reactions convert carboxylic acids into esters, amides, carboxylate salts, acid chlorides, and alcohols.
Their conversion to esters is widely used, e.g. in the production of polyesters. Likewise, carboxylic acids are converted into amides, but this conversion typically does not occur by direct reaction of the carboxylic acid and the amine. Instead esters are typical precursors to amides. The conversion of amino acids into peptides is a significant biochemical process that requires ATP.
Converting a carboxylic acid to an amide is possible, but not straightforward. Instead of acting as a nucleophile, an amine will react as a base in the presence of a carboxylic acid to give the ammonium carboxylate salt. Heating the salt to above 100 °C will drive off water and lead to the formation of the amide. This method of synthesizing amides is industrially important, and has laboratory applications as well. In the presence of a strong acid catalyst, carboxylic acids can condense to form acid anhydrides. The condensation produces water, however, which can hydrolyze the anhydride back to the starting carboxylic acids. Thus, the formation of the anhydride via condensation is an equilibrium process.
Under acid-catalyzed conditions, carboxylic acids will react with alcohols to form esters via the Fischer esterification reaction, which is also an equilibrium process. Alternatively, diazomethane can be used to convert an acid to an ester. While esterification reactions with diazomethane often give quantitative yields, diazomethane is only useful for forming methyl esters.
===Conversion to acyl halides===
The hydroxyl group on carboxylic acids may be replaced with a chlorine atom using thionyl chloride to give acyl chlorides. In nature, carboxylic acids are converted to thioesters. Thionyl chloride can be used to convert carboxylic acids to their corresponding acyl chlorides. First, carboxylic acid 1 attacks thionyl chloride, and chloride ion leaves. The resulting oxonium ion 2 is activated towards nucleophilic attack and has a good leaving group, setting it apart from a normal carboxylic acid. In the next step, 2 is attacked by chloride ion to give tetrahedral intermediate 3, a chlorosulfite. The tetrahedral intermediate collapses with the loss of sulfur dioxide and chloride ion, giving protonated acyl chloride 4. Chloride ion can remove the proton on the carbonyl group, giving the acyl chloride 5 with a loss of HCl.
Phosphorus(III) chloride (PCl3) and phosphorus(V) chloride (PCl5) will also convert carboxylic acids to acid chlorides, by a similar mechanism. One equivalent of PCl3 can react with three equivalents of acid, producing one equivalent of H3PO3, or phosphorus acid, in addition to the desired acid chloride. PCl5 reacts with carboxylic acids in a 1:1 ratio, and produces phosphorus(V) oxychloride (POCl3) and hydrogen chloride (HCl) as byproducts.
===Reactions with carbanion equivalents===
Carboxylic acids react with Grignard reagents and organolithiums to form ketones. The first equivalent of nucleophile acts as a base and deprotonates the acid. A second equivalent will attack the carbonyl group to create a geminal alkoxide dianion, which is protonated upon workup to give the hydrate of a ketone. Because most ketone hydrates are unstable relative to their corresponding ketones, the equilibrium between the two is shifted heavily in favor of the ketone. For example, the equilibrium constant for the formation of acetone hydrate from acetone is only 0.002. The carboxylic group is the most acidic in organic compounds.
===Specialized reactions===
As with all carbonyl compounds, the protons on the α-carbon are labile due to keto–enol tautomerization. Thus, the α-carbon is easily halogenated in the Hell–Volhard–Zelinsky halogenation.
The Schmidt reaction converts carboxylic acids to amines.
Carboxylic acids are decarboxylated in the Hunsdiecker reaction.
The Dakin–West reaction converts an amino acid to the corresponding amino ketone.
In the Barbier–Wieland degradation, a carboxylic acid on an aliphatic chain having a simple methylene bridge at the alpha position can have the chain shortened by one carbon. The inverse procedure is the Arndt–Eistert synthesis, where an acid is converted into acyl halide, which is then reacted with diazomethane to give one additional methylene in the aliphatic chain.
Many acids undergo oxidative decarboxylation. Enzymes that catalyze these reactions are known as carboxylases (EC 6.4.1) and decarboxylases (EC 4.1.1).
Carboxylic acids are reduced to aldehydes via the ester and DIBAL, via the acid chloride in the Rosenmund reduction and via the thioester in the Fukuyama reduction.
In ketonic decarboxylation carboxylic acids are converted to ketones.
Organolithium reagents (>2 equiv) react with carboxylic acids to give a dilithium 1,1-diolate, a stable tetrahedral intermediate which decomposes to give a ketone upon acidic workup.
The Kolbe electrolysis is an electrolytic, decarboxylative dimerization reaction. It gets rid of the carboxyl groups of two acid molecules, and joins the remaining fragments together.
==Carboxyl radical==
The carboxyl radical, •COOH, only exists briefly. The acid dissociation constant of •COOH has been measured using electron paramagnetic resonance spectroscopy. The carboxyl group tends to dimerise to form oxalic acid.
|
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"Pentadecylic acid",
"enthalpy of vaporization",
"Undecylic acid"
] |
6,100 |
Chernobyl
|
Chernobyl, also known as Chornobyl, is a partially abandoned city in the Chernobyl Exclusion Zone, situated in the Vyshhorod Raion of northern Kyiv Oblast, Ukraine. Chernobyl is about north of Kyiv, and southwest of the Belarusian city of Gomel. Before its evacuation, the city had about 14,000 residents (considerably less than neighboring Pripyat). While living anywhere within the Chernobyl Exclusion Zone is technically illegal today, authorities tolerate those who choose to live within some of the less irradiated areas, and an estimated 150 people lived in Chernobyl in 2020.
First mentioned as a ducal hunting lodge in 1193, the city has changed hands multiple times over the course of history. Jews moved into the city in the 16th century, and a now-defunct monastery was established in the area in 1626. By the end of the 18th century, Chernobyl was a major centre of Hasidic Judaism under the Twersky Dynasty, which left Chernobyl after the city was subjected to pogroms in the early 20th century. The Jewish community was later murdered during the Holocaust. Chernobyl was chosen as the site of Ukraine's first nuclear power plant in 1972, located north of the city, which opened in 1977. Chernobyl was evacuated on 5 May 1986, nine days after a catastrophic nuclear disaster at the plant, which was the largest nuclear disaster in history. Along with the residents of the nearby city of Pripyat, which was built as a home for the plant's workers, the population was relocated to the newly built city of Slavutych, and most have never returned.
The city was the administrative centre of Chernobyl Raion (district) from 1923. After the disaster, in 1988, the raion was dissolved and administration was transferred to the neighbouring Ivankiv Raion. The raion was abolished on 18 July 2020 as part of the administrative reform of Ukraine, which reduced the number of raions of Kyiv Oblast to seven. The area of Ivankiv Raion was merged into Vyshhorod Raion.
Although Chernobyl is primarily a ghost town today, a small number of people still live there, in houses marked with signs that read, "Owner of this house lives here", and a small number of animals live there as well. Workers on watch and administrative personnel of the Chernobyl Exclusion Zone are also stationed in the city. The city has two general stores and a hotel.
During the Russian invasion of Ukraine, Chernobyl was temporarily captured and occupied by Russian forces between 24 February and 2 April 2022. After its capture, it was reported that radiation levels temporarily rose, due to human activities, including earthworks, which disturbed the dust.
==Name==
The city's name is the same as one of the Ukrainian names for Artemisia vulgaris, mugwort or common wormwood: (or more commonly , 'common artemisia'). The name is inherited from or , a compound of + , the parts related to and , 'stalk', so named in distinction to the lighter-stemmed wormwood A. absinthium. or the use of romanized Ukrainian names for Ukrainian places generally.
==History==
The Polish Geographical Dictionary of the Kingdom of Poland of 1880–1902 states that the time the city was founded is not known.
===Identity of Ptolemy's "Azagarium"===
Some older geographical dictionaries and descriptions of modern Eastern Europe mention "Czernobol" (Chernobyl) with reference to Ptolemy's world map (2nd century AD). Czernobol is identified as "oppidium Sarmatiae" (Lat., "a city in Sarmatia"), by the 1605 Lexicon geographicum of Filippo Ferrari and the 1677 Lexicon Universale of Johann Jakob Hofmann. According to the Dictionary of Ancient Geography of Alexander Macbean (London, 1773), Azagarium is "a town of Sarmatia Europaea, on the Borysthenes" (Dnieper), 36° East longitude and 50°40' latitude. The city is "now supposed to be Czernobol, a town of Poland, in Red Russia [Red Ruthenia], in the Palatinate of Kiow [Kiev Voivodeship], not far from the Borysthenes."
Whether Azagarium is indeed Czernobol is debatable. The question of Azagarium's correct location was raised in 1842 by Habsburg-Slovak historian, Pavel Jozef Šafárik, who published a book titled "Slavic Ancient History" ("Sławiańskie starożytności"), where he claimed Azagarium to be the hill of Zaguryna, which he found on an old Russian map "Bolzoj czertez" (Big drawing) near the city of Pereiaslav, now in central Ukraine.
In 2019, Ukrainian architect Boris Yerofalov-Pylypchak published a book, Roman Kyiv or Castrum Azagarium at Kyiv-Podil.
===12th to 18th century===
The archaeological excavations that were conducted in 2005–2008 found a cultural layer from the 10–12th centuries AD, which predates the first documentary mention of Chernobyl.
Around the 12th century Chernobyl was part of the land of Kievan Rus′. The first known mention of the settlement as Chernobyl is from an 1193 charter, which describes it as a hunting lodge of Knyaz Rurik Rostislavich. In 1362 it was a crown village of the Grand Duchy of Lithuania. Around that time the town had own castle which was ruined at least on two occasions in 1473 and 1482. Jews were brought to Chernobyl by Filon Kmita, during the Polish campaign of colonization. The first mentioning of Jewish community in Chernobyl is in the 17th century. In 1600 the first Roman Catholic church was built in the town. In 1626, during the Counter-Reformation, a Dominican church and monastery were founded by Lukasz Sapieha. A group of Old Catholics opposed the decrees of the Council of Trent. The Chernobyl residents actively supported the Khmelnytsky Uprising (1648–1657). By the end of the 18th century, the town accounted for 2,865 residents and had 642 buildings. and became part of Radomyshl county (uezd) as a supernumerary town ("zashtatny gorod").
In 1832, following the failed Polish November Uprising, the Dominican monastery was sequestrated. The church of the Old Catholics was disbanded in 1852. The Polish and German community of Chernobyl was deported to Kazakhstan in 1936, during the Frontier Clearances.
====World War II and the Holocaust====
During World War II, Chernobyl was occupied by the German Army from 25 August 1941 to 17 November 1943. When the Germans arrived, only 400 Jews remained in Chernobyl; they were murdered during the Holocaust.
On 15 August 1972, the Chernobyl Nuclear Power Plant (officially the Vladimir Ilyich Lenin Nuclear Power Plant) began construction about northwest of Chernobyl. The plant was built alongside Pripyat, an "atomograd" city founded on 4 February 1970 that was intended to serve the nuclear power plant. The decision to build the power plant was adopted by the Central Committee of the Communist Party of the Soviet Union and the Council of Ministers of the Soviet Union on recommendations of the State Planning Committee that the Ukrainian SSR be its location. It was the first nuclear power plant to be built in Ukraine.
====Nuclear disaster of 26 April 1986====
After the nuclear disaster at the Chernobyl Nuclear Power Plant; the worst nuclear disaster in history, the city of Chernobyl was evacuated on 5 May 1986. Along with the residents of the nearby city of Pripyat, built as a home for the plant's workers, the population was relocated to the newly built city of Slavutych. While Pripyat remains completely abandoned with no remaining inhabitants, Chernobyl has since hosted a small population.
===Independent Ukraine (1991–present)===
With the dissolution of the Soviet Union in 1991, Chernobyl remained part of Ukraine within the Chernobyl Exclusion Zone which Ukraine inherited from the Soviet Union.
===Russian occupation (February–April 2022)===
During the Russian invasion of Ukraine, Russian forces captured the city on 24 February. Following the capture of Chernobyl, the Russian army used the city as a staging point for attacks on Kyiv. Ukrainian officials reported that the radiation levels in the city had started to rise due to recent military activity causing radioactive dust to ascend into the air. Hundreds of Russian soldiers were suffering from radiation poisoning after digging trenches in a contaminated area, and one died. On 31 March it was reported that Russian forces had left the exclusion zone. Ukrainian authorities reasserted control over the area on 2 April.
==Geography==
Chernobyl is located about north of Kyiv, and southwest of the Belarusian city of Gomel.
===Climate===
Chernobyl has a humid continental climate (Dfb) with very warm, wet summers with cool nights and long, cold, and snowy winters.
==Chernobyl nuclear reactor disaster==
On 26 April 1986, one of the reactors at the Chernobyl Nuclear Power Plant exploded after a scheduled test on the reactor was carried out improperly by plant operators. The resulting loss of control was due to design flaws of the RBMK reactor, which made it unstable when operated at low power, and prone to thermal runaway where increases in temperature increase reactor power output.
Chernobyl city was evacuated nine days after the disaster. The level of contamination with caesium-137 was around 555 kBq/m2 (surface ground deposition in 1986).
Later analyses concluded that, even with very conservative estimates, relocation of the city (or of any area below 1500 kBq/m2) could not be justified on the grounds of radiological health.
This however does not account for the uncertainty in the first few days of the accident about further depositions and weather patterns.
Moreover, an earlier short-term evacuation could have averted more significant doses from short-lived isotope radiation (specifically iodine-131, which has a half-life of eight days).
The long-term health effects of the Chernobyl disaster are a subject of some controversy.
In 1998, average caesium-137 doses from the accident (estimated at 1–2 mSv per year) did not exceed those from other sources of exposure. Current effective caesium-137 dose rates as of 2019 are 200–250 nSv/h, or roughly 1.7–2.2 mSv per year,
which is comparable to the worldwide average background radiation from natural sources.
The base of operations for the administration and monitoring of the Chernobyl Exclusion Zone was moved from Pripyat to Chernobyl. Chernobyl currently contains offices for the State Agency of Ukraine on the Exclusion Zone Management and accommodations for visitors. Apartment blocks have been repurposed as accommodations for employees of the State Agency. The length of time that workers may spend within the Chernobyl Exclusion Zone is restricted by regulations that have been implemented to limit radiation exposure. Today, visits are allowed to Chernobyl but limited by strict rules.
In 2003, the United Nations Development Programme launched a project, called the Chernobyl Recovery and Development Programme (CRDP), for the recovery of the affected areas. The main goal of the CRDP's activities is supporting the efforts of the Government of Ukraine to mitigate the long-term social, economic, and ecological consequences of the Chernobyl disaster.
The city has become overgrown and many types of animals live there. According to census information collected over an extended period of time, it is estimated that more mammals live there now than before the disaster.
Notably, Mikhail Gorbachev, the final leader of the Soviet Union, stated in respect to the Chernobyl disaster that, "More than anything else, (Chernobyl) opened the possibility of much greater freedom of expression, to the point that the (Soviet) system as we knew it could no longer continue."
==Notable people==
Aaron Twersky of Chernobyl (1784–1871), rabbi
Aleksander Franciszek Chodkiewicz (1776–1838), Polish politician and lithographer
Alexander Krasnoshchyokov (1880–1937), politician
Andriy Smalko (1981–), football player
Arnold Lakhovsky (1880–1937), artist
Jan Mikołaj Chodkiewicz (1738–1781), Polish nobleman, father of Rozalia Lubomirska
Ekaterina Scherbachenko (1977–), opera singer
Grigory Irmovich Novak (1919–1980), Jewish Soviet weightlifter
Joshua ben Aaron Zeitlin (1823–1888), scholar and philanthropist
Markiyan Kamysh (1988–), novelist and son of a liquidator
Rozalia Lubomirska (1768–1794), Polish noblewoman guillotined during the French Revolution
Volodymyr Pravyk (1962–1986), firefighter and liquidator
|
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"Davies, Norman",
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"Holodomor",
"Holocaust",
"Ptolemy's world map",
"World War II",
"Belarus",
"Becquerel",
"Pavel Jozef Šafárik",
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"Aleksander Franciszek Chodkiewicz",
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"Andriy Smalko",
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] |
6,102 |
Cyan
|
Cyan () is the color between blue and green on the visible spectrum of light. It is evoked by light with a predominant wavelength between 500 and 520 nm, between the wavelengths of green and blue.
In the subtractive color system, or CMYK color model, which can be overlaid to produce all colors in paint and color printing, cyan is one of the primary colors, along with magenta and yellow. In the additive color system, or RGB color model, used to create all the colors on a computer or television display, cyan is made by mixing equal amounts of green and blue light. Cyan is the complement of red; it can be made by the removal of red from white. Mixing red light and cyan light at the right intensity will make white light. It is commonly seen on a bright, sunny day in the sky.
==Shades and variations ==
Different shades of cyan can vary in terms of hue, chroma (also known as saturation, intensity, or colorfulness), or lightness (or value, tone, or brightness), or any combination of these characteristics. Differences in value can also be referred to as tints and shades, with a tint being a cyan mixed with white, and a shade being mixed with black.
Color nomenclature is subjective. Many shades of cyan with a bluish hue are called blue. Similarly, those with a greenish hue are referred to as green. A cyan with a dark shade is commonly known as teal. A teal blue shade leans toward the blue end of the spectrum. Variations of teal with a greener tint are commonly referred to as teal green.
Turquoise, reminiscent of the stone with the same name, is a shade in the green spectrum of cyan hues. Celeste is a lightly tinted cyan that represents the color of a clear sky. Other colors in the cyan color range are electric blue, aquamarine, and others described as blue-green.
==History ==
Cyan boasts a rich and diverse history, holding cultural significance for millennia. In ancient civilizations, turquoise, valued for its aesthetic appeal, served as a highly regarded precious gem. Turquoise comes in a variety of shades from green to blue, but cyan hues are particularly prevalent. Approximately 3,700 years ago, an intricately crafted dragon-shaped treasure made from over 2,000 pieces of turquoise and jade was created. This artifact is widely recognized as the oldest Chinese dragon totem by many Chinese scholars.
Turquoise jewelry also held significant importance among the Aztecs, who often featured this precious gemstone in vibrant frescoes for both symbolic and decorative purposes. The Aztecs revered turquoise, associating its color with the heavens and sacredness. Additionally, ancient Egyptians interpreted cyan hues as representing faith and truth, while Tibetans viewed them as a symbol of infinity.
After earlier uses in various contexts, cyan hues found increased use in diverse cultures due to their appealing aesthetic qualities in religious structures and art pieces. For example, the prominent dome of the Goharshad Mosque in Iran, built in 1418, showcases this trend. Additionally, Jacopo da Pontormo's use of a teal shade for Mary's robe in the 1528 painting Carmignano Visitation demonstrates the allure for these hues.
In the 1870s, the French sculptor Frédéric Bartholdi began the construction of what would later become the Statue of Liberty. Over time, exposure to the elements caused the copper structure to develop its distinctive patina, now recognized as iconic cyan. In 1917, the color term teal was introduced to describe deeper shades of cyan.
In the late 19th century, while traditional nomenclature of red, yellow, and blue persisted, the printing industry initiated a shift towards utilizing magenta and cyan inks for red and blue hues, respectively. This transition aimed to establish a more versatile color gamut achievable with only three primary colors. In 1949, a document in the printing industry stated: “The four-color set comprises Yellow, Red (magenta), Blue (cyan), Black”. This practice of labeling magenta, yellow, and cyan as red, yellow, and blue persisted until 1961. As the hues evolved, the printing industry maintained the use of the traditional terms red, yellow, and blue. Consequently, pinpointing the exact date of origin for CMYK, in which cyan serves as a primary color, proves challenging.
In August 1991, the HP Deskwriter 500C became the first Deskwriter to offer color printing as an option. It used interchangeable black and color (cyan, magenta, and yellow) inkjet print cartridges. With the inclusion of cyan ink in printers, the term "cyan" has become widely recognized in both home and office settings. According to TUP/Technology User Profile 2020, approximately 70% of online American adults regularly use a home printer.
==Etymology and terminology==
Its name is derived from the Ancient Greek word kyanos (κύανος), meaning "dark blue enamel, Lapis lazuli". It was formerly known as "cyan blue" or cyan-blue, and its first recorded use as a color name in English was in 1879. Further origins of the color name can be traced back to a dye produced from the cornflower (Centaurea cyanus).
In most languages, 'cyan' is not a basic color term and it phenomenologically appears as a greenish vibrant hue of blue to most English speakers. Other English terms for this "borderline" hue region include blue green, aqua, turquoise, teal, and grue.
==On the web and in printing==
===Web colors cyan and aqua===
The web color cyan shown at right is a secondary color in the RGB color model, which uses combinations of red, green and blue light to create all the colors on computer and television displays. In X11 colors, this color is called both cyan and aqua. In the HTML color list, this same color is called aqua.
The web colors are more vivid than the cyan used in the CMYK color system, and the web colors cannot be accurately reproduced on a printed page. To reproduce the web color cyan in inks, it is necessary to add some white ink to the printer's cyan below, so when it is reproduced in printing, it is not a primary subtractive color. It is called aqua (a name in use since 1598) because it is a color commonly associated with water, such as the appearance of the water at a tropical beach.
===Process cyan===
Cyan is also one of the common inks used in four-color printing, along with magenta, yellow, and black; this set of colors is referred to as CMYK. In printing, the cyan ink is sometimes known as printer's cyan, process cyan, or process blue.
While both the additive secondary and the subtractive primary are called cyan, they can be substantially different from one another. Cyan printing ink is typically more saturated than the RGB secondary cyan, depending on what RGB color space and ink are considered. That is, process cyan is usually outside the RGB gamut, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color that is pure cyan ink. This is because real-world subtractive (unlike additive) color mixing does not consistently produce the same result when mixing apparently identical colors, since the specific frequencies filtered out to produce that color affect how it interacts with other colors. Phthalocyanine blue is one such commonly used pigment. A typical formulation of process cyan is shown in the color box on the right.
==In science and nature==
===Color of water===
Pure water is nearly colorless. However, it does absorb slightly more red light than blue, giving significant volumes of water a bluish tint; increased scattering of blue light due to fine particles in the water shifts the blue color toward green, for a typically cyan net color.
===Cyan and cyanide===
Cyanide derives its name from Prussian blue, a blue pigment containing the cyanide ion.
===Bacteria===
Cyanobacteria (sometimes called blue-green algae) are an important link in the food chain.
===Astronomy===
The planet Uranus is colored cyan because of the abundance of methane in its atmosphere. Methane absorbs red light and reflects the blue-green light which allows observers to see it as cyan.
===Energy===
Natural gas (methane), used by many for home cooking on gas stoves, has a cyan colored flame when burned with a mixture of air.
===Photography and film===
Cyanotype, or blueprint, a monochrome photographic printing process that predates the use of the word cyan as a color, yields a deep cyan-blue colored print based on the Prussian blue pigment.
Cinecolor, a bi-pack color process, the photographer would load a standard camera with two films, one orthochromatic, dyed red, and a panchromatic strip behind it. Color light would expose the cyan record on the ortho stock, which also acted as a filter, exposing only red light to the panchromatic film stock.
===Medicine===
Cyanosis is an abnormal blueness of the skin, usually a sign of poor oxygen intake; patients are typically described as being "cyanotic".
Cyanopsia is a color vision defect where vision is tinted blue. This can be a drug-induced side effect or experienced after cataract removal.
==Gallery==
File:Green and blue make cyan.png|In the RGB color model, used to make colors on computer and TV displays, cyan is created by the combination of green and blue light.
File:RGB color wheel.svg|In the RGB and CMY(K) color wheel, cyan is midway between blue and green.
File:SubtractiveColor.svg|In the CMYK color model, used in color printing, cyan, magenta and yellow combined make black. In practice, since the inks are not perfect, some black ink is added.
File:Refill Ink Kit Color crop.jpg|Color printers today use, magenta, cyan and yellow ink to produce a wide range of colors.
File:Komplementärfarben cyan auf rot.svg|Cyan and red are complementary colors in most color spaces (mixing them in equal amounts produces an achromatic color). They have a strong contrast.
File:Wham-a different corner.jpg|Cyan is the color of shallow water over a sandy beach. The water absorbs the color red from the sunlight, leaving a greenish-blue color.
File:Samarkand05.jpg|The dome of the Tilla Kari Mosque in Samarkand, Uzbekistan (1660) is cyan. The color is widely used in architecture in Turkey and Central Asia.
File:Uranus_Voyager2_color_calibrated.png|The planet Uranus, seen from the Voyager 2 spacecraft. The cyan color comes from a combination of methane gas and atmospheric haze in the planet's atmosphere.
File:Wirbelsäulenoperation OKM.jpg|alt=A surgical team in Germany. It has been suggested that surgeons and nurses adopted a cyan-colored gown and operating rooms because it is complementary to the color of red blood and thus reduced glare, though the evidence for this claim is limited.|A surgical team in Germany. It has been suggested that surgeons and nurses adopted a cyan-colored gown and operating rooms because it contrasts the color of red blood, thus reducing glare, though the evidence for this claim is limited.
File:Old photo colors degredated into cyan.jpg|The pigments in color photographs may degrade at different rates, potentially resulting in a cyan tint.
|
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6,105 |
Conventional insulin therapy
|
Conventional insulin therapy is a therapeutic regimen for treatment of diabetes mellitus which contrasts with the newer intensive insulin therapy.
This older method (prior to the development of home blood glucose monitoring) is still in use in a proportion of cases.
== Characteristics ==
Conventional insulin therapy is characterized by:
Insulin injections of a mixture of regular (or rapid) and intermediate acting insulin are performed two times a day, or to improve overnight glucose, mixed in the morning to cover breakfast and lunch, but with regular (or rapid) acting insulin alone for dinner and intermediate acting insulin at bedtime (instead of being mixed in at dinner).
Meals are scheduled to match the anticipated peaks in the insulin profiles.
The target range for blood glucose levels is higher than is desired in the intensive regimen.
Frequent measurements of blood glucose levels were not used.
== Effects ==
The down side of this method is that it is difficult to achieve as good results of glycemic control as with intensive insulin therapy. The advantage is that, for diabetics with a regular lifestyle, the regime is less intrusive than the intensive therapy.
|
[
"intensive insulin therapy",
"Diabetes management",
"blood glucose monitoring",
"diabetes mellitus"
] |
6,109 |
Cream
|
Cream is a dairy product composed of the higher-fat layer skimmed from the top of milk before homogenization. In un-homogenized milk, the fat, which is less dense, eventually rises to the top. In the industrial production of cream, this process is accelerated by using centrifuges called "separators". In many countries, it is sold in several grades depending on the total butterfat content. It can be dried to a powder for shipment to distant markets, and contains high levels of saturated fat.
Cream skimmed from milk may be called "sweet cream" to distinguish it from cream skimmed from whey, a by-product of cheese-making. Whey cream has a lower fat content and tastes more salty, tangy, and "cheesy". In many countries partially fermented cream is also sold: sour cream, crème fraîche, and so on. Both forms have many culinary uses in both sweet and savoury dishes.
Cream produced by cattle (particularly Jersey cattle) grazing on natural pasture often contains some fat-soluble carotenoid pigments derived from the plants they eat; traces of these intensely colored pigments concentrated during separation give cream a slightly yellow hue, hence the name of the yellow-tinged off-white color cream. Carotenoids are also the origin of butter's yellow color. Cream from goat's milk, water buffalo milk, or from cows fed indoors on grain or grain-based pellets, is white.
==Cuisine==
Cream is used as an ingredient in many foods, including ice cream, many sauces, soups, stews, puddings, and some custard bases, and is also used for cakes. Whipped cream is served as a topping on ice cream sundaes, milkshakes, lassi, eggnog, sweet pies, strawberries, blueberries, or peaches. Cream is also used in Indian curries such as masala dishes. Both single and double cream (see Types for definitions) can be used in cooking. Double cream or full-fat crème fraîche is often used when the cream is added to a hot sauce, to prevent it separating or "splitting". Double cream can be thinned with milk to make an approximation of single cream.
Cream (usually light/single cream or half and half) may be added to coffee.
The French word denotes not only dairy cream but also other thick liquids such as sweet and savory custards, which are normally made with milk, not cream.
==Types ==
Different grades of cream are distinguished by their fat content, whether they have been heat-treated, whipped, and so on. In many jurisdictions, there are regulations for each type.
===Australia and New Zealand===
The Australia New Zealand Food Standards Code – Standard 2.5.2 – Defines cream as a milk product comparatively rich in fat, in the form of an emulsion of fat-in-skim milk, which can be obtained by separation from milk. Cream sold without further specification must contain no less than 350 g/kg (35%) milk fat.
Manufacturers labels may distinguish between different fat contents, a general guideline is as follows:
=== Canada ===
Canadian cream definitions are similar to those used in the United States, except for "light cream", which is very low-fat cream, usually with 5 or 6 percent butterfat. Specific product characteristics are generally uniform throughout Canada, but names vary by both geographic and linguistic area and by manufacturer: "coffee cream" may be 10 or 18 percent cream and "half-and-half" () may be 3, 5, 6 or 10 percent, all depending on location and brand.
Regulations allow cream to contain acidity regulators and stabilizers. For whipping cream, allowed additives include skim milk powder (≤ 0.25%), glucose solids (≤ 0.1%), calcium sulphate (≤ 0.005%), and xanthan gum (≤ 0.02%). The content of milk fat in canned cream must be displayed as a percentage followed by "milk fat", "B.F", or "M.F".
=== France ===
In France, the use of the term "cream" for food products is defined by the decree 80-313 of April 23, 1980. It specifies the minimum rate of milk fat (12%) as well as the rules for pasteurisation or UHT sterilisation. The mention "crème fraîche" (fresh cream) can only be used for pasteurised creams conditioned on production site within 24h after pasteurisation. Even if food additives complying with French and European laws are allowed, usually, none will be found in plain "crèmes" and "crèmes fraîches" apart from lactic ferments (some low cost creams (or close to creams) can contain thickening agents, but rarely). Fat content is commonly shown as "XX% M.G." ("matière grasse").
=== Russia ===
Russia, as well as other EAC countries, legally separates cream into two classes: normal (10–34% butterfat) and heavy (35–58%), but the industry has pretty much standardized around the following types:
===Sweden===
In Sweden, cream is usually sold as:
Matlagningsgrädde ("cooking cream"), 10–15%
Kaffegrädde ("Coffee cream"), 10–12%, earlier mostly 12%
Vispgrädde (whipping cream), 36–40%, the 36% variant often has additives.
Mellangrädde (27%) is, nowadays, a less common variant.
Gräddfil (usually 12%) and Creme Fraiche (usually around 35%) are two common sour cream products.
=== Switzerland ===
In Switzerland, the types of cream are legally defined as follows:
Sour cream and crème fraîche (German: Sauerrahm, Crème fraîche; French: crème acidulée, crème fraîche; Italian: panna acidula, crème fraîche) are defined as cream soured by bacterial cultures.
Thick cream (German: ; French: ; Italian: ) is defined as cream thickened using thickening agents.
===United Kingdom===
In the United Kingdom, these types of cream are produced. Fat content must meet the Food Labelling Regulations 1996.
Not all grades are defined by all jurisdictions, and the exact fat content ranges vary. The above figures, except for "manufacturer's cream", are based on the Code of Federal Regulations, Title 21, Part 131.
==Processing and additives==
Cream may have thickening agents and stabilizers added. Thickeners include sodium alginate, carrageenan, gelatine, sodium bicarbonate, tetrasodium pyrophosphate, and alginic acid.
Other processing may be carried out. For example, cream has a tendency to produce oily globules (called "feathering") when added to coffee. The stability of the cream may be increased by increasing the non-fat solids content, which can be done by partial demineralisation and addition of sodium caseinate, although this is expensive. Oreo and Hydrox cookies are a type of sandwich cookie in which two biscuits have a soft, sweet filling between them that is called "crème filling." In some cases, foods can be described as cream although they do not contain predominantly milk fats; for example, in Britain, "ice cream" can contain non-milk fat (declared on the label) in addition to or instead of cream, and salad cream is the customary name for a non-dairy condiment that has been produced since the 1920s.
In other languages, cognates of "cream" are also sometimes used for non-food products, such as fogkrém (Hungarian for toothpaste), or Sonnencreme (German for sunscreen).
Some products are described as "cream alternatives". For example, Elmlea Double, etc. are blends of buttermilk or lentils and vegetable oil with other additives sold by Upfield in the United Kingdom packaged and shelved in the same way as cream, labelled as having "a creamy taste".
|
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6,111 |
Chemical vapor deposition
|
Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films.
In typical CVD, the wafer (substrate) is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.
Microfabrication processes widely use CVD to deposit materials in various forms, including: monocrystalline, polycrystalline, amorphous, and epitaxial. These materials include: silicon (dioxide, carbide, nitride, oxynitride), carbon (fiber, nanofibers, nanotubes, diamond and graphene), fluorocarbons, filaments, tungsten, titanium nitride and various high-κ dielectrics.
The term chemical vapour deposition was coined in 1960 by John M. Blocher, Jr. who intended to differentiate chemical from physical vapour deposition (PVD).
== Types ==
CVD is practiced in a variety of formats. These processes generally differ in the means by which chemical reactions are initiated.
Classified by operating conditions:
Atmospheric pressure CVD (APCVD) – CVD at atmospheric pressure.
Low-pressure CVD (LPCVD) – CVD at sub-atmospheric pressures. Many journal articles and commercial tools use the term reduced pressure CVD (RPCVD) especially for single wafer tools in place of LPCVD which dominates for multi-wafer furnace tube tools. Reduced pressures tend to reduce unwanted gas-phase reactions and improve film uniformity across the wafer.
Ultrahigh vacuum CVD (UHVCVD) – CVD at very low pressure, typically below 10−6 Pa (≈ 10−8 torr). Note that in other fields, a lower division between high and ultra-high vacuum is common, often 10−7 Pa.
Sub-atmospheric CVD (SACVD) – CVD at sub-atmospheric pressures. Uses tetraethyl orthosilicate (TEOS) and ozone to fill high aspect ratio Si structures with silicon dioxide (SiO2).
Most modern CVD is either LPCVD or UHVCVD.
Classified by physical characteristics of vapor:
Aerosol assisted CVD (AACVD) – CVD in which the precursors are transported to the substrate by means of a liquid/gas aerosol, which can be generated ultrasonically. This technique is suitable for use with non-volatile precursors.
Direct liquid injection CVD (DLICVD) – CVD in which the precursors are in liquid form (liquid or solid dissolved in a convenient solvent). Liquid solutions are injected in a vaporization chamber towards injectors (typically car injectors). The precursor vapors are then transported to the substrate as in classical CVD. This technique is suitable for use on liquid or solid precursors. High growth rates can be reached using this technique.
Classified by type of substrate heating:
Hot wall CVD – CVD in which the chamber is heated by an external power source and the substrate is heated by radiation from the heated chamber walls.
Cold wall CVD – CVD in which only the substrate is directly heated either by induction or by passing current through the substrate itself or a heater in contact with the substrate. The chamber walls are at room temperature.
Plasma methods (see also Plasma processing):
Microwave plasma-assisted CVD (MPCVD)
Plasma-enhanced CVD (PECVD) – CVD that utilizes plasma to enhance chemical reaction rates of the precursors. PECVD processing allows deposition at lower temperatures, which is often critical in the manufacture of semiconductors. The lower temperatures also allow for the deposition of organic coatings, such as plasma polymers, that have been used for nanoparticle surface functionalization.
Remote plasma-enhanced CVD (RPECVD) – Similar to PECVD except that the wafer substrate is not directly in the plasma discharge region. Removing the wafer from the plasma region allows processing temperatures down to room temperature.
Low-energy plasma-enhanced chemical vapor deposition (LEPECVD) - CVD employing a high density, low energy plasma to obtain epitaxial deposition of semiconductor materials at high rates and low temperatures.
Atomic-layer CVD (ALCVD) – Deposits successive layers of different substances to produce layered, crystalline films. See Atomic layer epitaxy.
Combustion chemical vapor deposition (CCVD) – Combustion Chemical Vapor Deposition or flame pyrolysis is an open-atmosphere, flame-based technique for depositing high-quality thin films and nanomaterials.
Hot filament CVD (HFCVD) – also known as catalytic CVD (Cat-CVD) or more commonly, initiated CVD, this process uses a hot filament to chemically decompose the source gases. The filament temperature and substrate temperature thus are independently controlled, allowing colder temperatures for better absorption rates at the substrate and higher temperatures necessary for decomposition of precursors to free radicals at the filament.
Hybrid physical-chemical vapor deposition (HPCVD) – This process involves both chemical decomposition of precursor gas and vaporization of a solid source.
Metalorganic chemical vapor deposition (MOCVD) – This CVD process is based on metalorganic precursors.
Rapid thermal CVD (RTCVD) – This CVD process uses heating lamps or other methods to rapidly heat the wafer substrate. Heating only the substrate rather than the gas or chamber walls helps reduce unwanted gas-phase reactions that can lead to particle formation.
Vapor-phase epitaxy (VPE)
Photo-initiated CVD (PICVD) – This process uses UV light to stimulate chemical reactions. It is similar to plasma processing, given that plasmas are strong emitters of UV radiation. Under certain conditions, PICVD can be operated at or near atmospheric pressure.
Laser chemical vapor deposition (LCVD) - This CVD process uses lasers to heat spots or lines on a substrate in semiconductor applications. In MEMS and in fiber production the lasers are used rapidly to break down the precursor gas—process temperature can exceed 2000 °C—to build up a solid structure in much the same way as laser sintering based 3-D printers build up solids from powders.
== Uses ==
CVD is commonly used to deposit conformal films and augment substrate surfaces in ways that more traditional surface modification techniques are not capable of. CVD is extremely useful in the process of atomic layer deposition at depositing extremely thin layers of material. A variety of applications for such films exist. Gallium arsenide is used in some integrated circuits (ICs) and photovoltaic devices. Amorphous polysilicon is used in photovoltaic devices. Certain carbides and nitrides confer wear-resistance. Polymerization by CVD, perhaps the most versatile of all applications, allows for super-thin coatings which possess some very desirable qualities, such as lubricity, hydrophobicity and weather-resistance to name a few. The CVD of metal-organic frameworks, a class of crystalline nanoporous materials, has recently been demonstrated. Recently scaled up as an integrated cleanroom process depositing large-area substrates, the applications for these films are anticipated in gas sensing and low-κ dielectrics. CVD techniques are advantageous for membrane coatings as well, such as those in desalination or water treatment, as these coatings can be sufficiently uniform (conformal) and thin that they do not clog membrane pores.
==Commercially important materials prepared by CVD==
===Polysilicon===
Polycrystalline silicon is deposited from trichlorosilane (SiHCl3) or silane (SiH4), using the following reactions:
SiHCl3 → Si + Cl2 + HCl
SiH4 → Si + 2 H2
This reaction is usually performed in LPCVD systems, with either pure silane feedstock, or a solution of silane with 70–80% nitrogen. Temperatures between 600 and 650 °C and pressures between 25 and 150 Pa yield a growth rate between 10 and 20 nm per minute. An alternative process uses a hydrogen-based solution. The hydrogen reduces the growth rate, but the temperature is raised to 850 or even 1050 °C to compensate. Polysilicon may be grown directly with doping, if gases such as phosphine, arsine or diborane are added to the CVD chamber. Diborane increases the growth rate, but arsine and phosphine decrease it.
=== Silicon dioxide ===
Silicon dioxide (usually called simply "oxide" in the semiconductor industry) may be deposited by several different processes. Common source gases include silane and oxygen, dichlorosilane (SiCl2H2) and nitrous oxide (N2O), or tetraethylorthosilicate (TEOS; Si(OC2H5)4). The reactions are as follows:
SiH4 + O2 → SiO2 + 2 H2
SiCl2H2 + 2 N2O → SiO2 + 2 N2 + 2 HCl
Si(OC2H5)4 → SiO2 + byproducts
The choice of source gas depends on the thermal stability of the substrate; for instance, aluminium is sensitive to high temperature. Silane deposits between 300 and 500 °C, dichlorosilane at around 900 °C, and TEOS between 650 and 750 °C, resulting in a layer of low- temperature oxide (LTO). However, silane produces a lower-quality oxide than the other methods (lower dielectric strength, for instance), and it deposits nonconformally. Any of these reactions may be used in LPCVD, but the silane reaction is also done in APCVD. CVD oxide invariably has lower quality than thermal oxide, but thermal oxidation can only be used in the earliest stages of IC manufacturing.
Oxide may also be grown with impurities (alloying or "doping"). This may have two purposes. During further process steps that occur at high temperature, the impurities may diffuse from the oxide into adjacent layers (most notably silicon) and dope them. Oxides containing 5–15% impurities by mass are often used for this purpose. In addition, silicon dioxide alloyed with phosphorus pentoxide ("P-glass") can be used to smooth out uneven surfaces. P-glass softens and reflows at temperatures above 1000 °C. This process requires a phosphorus concentration of at least 6%, but concentrations above 8% can corrode aluminium. Phosphorus is deposited from phosphine gas and oxygen:
4 PH3 + 5 O2 → 2 P2O5 + 6 H2
Glasses containing both boron and phosphorus (borophosphosilicate glass, BPSG) undergo viscous flow at lower temperatures; around 850 °C is achievable with glasses containing around 5 weight % of both constituents, but stability in air can be difficult to achieve. Phosphorus oxide in high concentrations interacts with ambient moisture to produce phosphoric acid. Crystals of BPO4 can also precipitate from the flowing glass on cooling; these crystals are not readily etched in the standard reactive plasmas used to pattern oxides, and will result in circuit defects in integrated circuit manufacturing.
Besides these intentional impurities, CVD oxide may contain byproducts of the deposition. TEOS produces a relatively pure oxide, whereas silane introduces hydrogen impurities, and dichlorosilane introduces chlorine.
Lower temperature deposition of silicon dioxide and doped glasses from TEOS using ozone rather than oxygen has also been explored (350 to 500 °C). Ozone glasses have excellent conformality but tend to be hygroscopic – that is, they absorb water from the air due to the incorporation of silanol (Si-OH) in the glass. Infrared spectroscopy and mechanical strain as a function of temperature are valuable diagnostic tools for diagnosing such problems.
==== Silicon nitride ====
Silicon nitride is often used as an insulator and chemical barrier in manufacturing ICs. The following two reactions deposit silicon nitride from the gas phase:
3 SiH4 + 4 NH3 → Si3N4 + 12 H2
3 SiCl2H2 + 4 NH3 → Si3N4 + 6 HCl + 6 H2
Silicon nitride deposited by LPCVD contains up to 8% hydrogen. It also experiences strong tensile stress, which may crack films thicker than 200 nm. However, it has higher resistivity and dielectric strength than most insulators commonly available in microfabrication (1016 Ω·cm and 10 MV/cm, respectively).
Another two reactions may be used in plasma to deposit SiNH:
2 SiH4 + N2 → 2 SiNH + 3 H2
SiH4 + NH3 → SiNH + 3 H2
These films have much less tensile stress, but worse electrical properties (resistivity 106 to 1015 Ω·cm, and dielectric strength 1 to 5 MV/cm).
=== Metals ===
Tungsten CVD, used for forming conductive contacts, vias, and plugs on a semiconductor device, is achieved from tungsten hexafluoride (WF6), which may be deposited in two ways:
WF6 → W + 3 F2
WF6 + 3 H2 → W + 6 HF
Other metals, notably aluminium and copper, can be deposited by CVD. , commercially cost-effective CVD for copper did not exist, although volatile sources exist, such as Cu(hfac)2. Copper is typically deposited by electroplating. Aluminium can be deposited from triisobutylaluminium (TIBAL) and related organoaluminium compounds.
CVD for molybdenum, tantalum, titanium, nickel is widely used. These metals can form useful silicides when deposited onto silicon. Mo, Ta and Ti are deposited by LPCVD, from their pentachlorides. Nickel, molybdenum, and tungsten can be deposited at low temperatures from their carbonyl precursors. In general, for an arbitrary metal M, the chloride deposition reaction is as follows:
2 MCl5 + 5 H2 → 2 M + 10 HCl
whereas the carbonyl decomposition reaction can happen spontaneously under thermal treatment or acoustic cavitation and is as follows:
M(CO)n → M + n CO
the decomposition of metal carbonyls is often violently precipitated by moisture or air, where oxygen reacts with the metal precursor to form metal or metal oxide along with carbon dioxide.
Niobium(V) oxide layers can be produced by the thermal decomposition of niobium(V) ethoxide with the loss of diethyl ether according to the equation:
2 Nb(OC2H5)5 → Nb2O5 + 5 C2H5OC2H5
=== Graphene ===
Many variations of CVD can be utilized to synthesize graphene. Although many advancements have been made, the processes listed below are not commercially viable yet.
Carbon source
The most popular carbon source that is used to produce graphene is methane gas. One of the less popular choices is petroleum asphalt, notable for being inexpensive but more difficult to work with.
Although methane is the most popular carbon source, hydrogen is required during the preparation process to promote carbon deposition on the substrate. If the flow ratio of methane and hydrogen are not appropriate, it will cause undesirable results. During the growth of graphene, the role of methane is to provide a carbon source, the role of hydrogen is to provide H atoms to corrode amorphous C, and improve the quality of graphene. But excessive H atoms can also corrode graphene. As a result, the integrity of the crystal lattice is destroyed, and the quality of graphene is deteriorated. Therefore, by optimizing the flow rate of methane and hydrogen gases in the growth process, the quality of graphene can be improved.
Use of catalyst
The use of catalyst is viable in changing the physical process of graphene production. Notable examples include iron nanoparticles, nickel foam, and gallium vapor. These catalysts can either be used in situ during graphene buildup, or situated at some distance away at the deposition area. Some catalysts require another step to remove them from the sample material. paves the way for synthesizing high-quality graphene for device applications while avoiding the transfer process.
Physical conditions
Physical conditions such as surrounding pressure, temperature, carrier gas, and chamber material play a big role in production of graphene.
Most systems use LPCVD with pressures ranging from 1 to 1500 Pa. Quartz is chosen because it has a very high melting point and is chemically inert. In other words, quartz does not interfere with any physical or chemical reactions regardless of the conditions.
Methods of analysis of results
Raman spectroscopy, X-ray spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) are used to examine and characterize the graphene samples.
===Graphene nanoribbon===
In spite of graphene's exciting electronic and thermal properties, it is unsuitable as a transistor for future digital devices, due to the absence of a bandgap between the conduction and valence bands. This makes it impossible to switch between on and off states with respect to electron flow. Scaling things down, graphene nanoribbons of less than 10 nm in width do exhibit electronic bandgaps and are therefore potential candidates for digital devices. Precise control over their dimensions, and hence electronic properties, however, represents a challenging goal, and the ribbons typically possess rough edges that are detrimental to their performance.
=== Diamond ===
CVD can be used to produce a synthetic diamond by creating the circumstances necessary for carbon atoms in a gas to settle on a substrate in crystalline form. CVD of diamonds has received much attention in the materials sciences because it allows many new applications that had previously been considered too expensive. CVD diamond growth typically occurs under low pressure (1–27 kPa; 0.145–3.926 psi; 7.5–203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.
Using CVD, films of diamond can be grown over large areas of substrate with control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce a diamond, the result was typically very small free-standing diamonds of varying sizes. With CVD diamond, growth areas of greater than fifteen centimeters (six inches) in diameter have been achieved, and much larger areas are likely to be successfully coated with diamond in the future. Improving this process is key to enabling several important applications.
The growth of diamond directly on a substrate allows the addition of many of diamond's important qualities to other materials. Since diamond has the highest thermal conductivity of any bulk material, layering diamond onto high heat-producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond's hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate. Diamond's very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (polytetrafluoroethylene) and strong lipophilicity would make it a nearly ideal non-stick coating for cookware if large substrate areas could be coated economically.
CVD growth allows one to control the properties of the diamond produced. In the area of diamond growth, the word "diamond" is used as a description of any material primarily made up of sp3-bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single-crystal diamond can be made containing various dopants. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon, while others are not. These different factors affect the diamond's hardness, smoothness, conductivity, optical properties and more.
==Chalcogenides==
Commercially, mercury cadmium telluride is of continuing interest for detection of infrared radiation. Consisting of an alloy of CdTe and HgTe, this material can be prepared from the dimethyl derivatives of the respective elements.
|
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6,112 |
CN Tower
|
{{Infobox building
| name = CN Tower
| native_name = Tour CN
| alternate_names = Canadian National Tower, Canada's National Tower
| status = Complete
| image = Toronto - ON - Toronto Harbourfront7.jpg
| caption = The CN Tower as seen from the Toronto City Centre Airport in September 2008, it is currently the world's 10th tallest free-standing structure on land
| address = Toronto, OntarioM5V 3L9
| coordinates =
| start_date =
| highest_next = Burj Khalifa
| building_type = Mixed use: Observation, telecommunications, attraction, restaurant
| architectural =
| antenna_spire =
| roof =
| elevator_count = 9 Completed in 1976, it is located in downtown Toronto, built on the former Railway Lands. Its name "CN" referred to Canadian National, the railway company that built the tower. Following the railway's decision to divest non-core freight railway assets prior to the company's privatization in 1995, it transferred the tower to the Canada Lands Company, a federal Crown corporation responsible for the government's real estate portfolio.
The CN Tower held the record for the world's tallest free-standing structure for 32 years, from 1975 until 2007, when it was surpassed by the Burj Khalifa, and was the world's tallest tower until 2009 when it was surpassed by the Canton Tower. It is currently the tenth-tallest free-standing structure in the world and remains the tallest free-standing structure on land in the Western Hemisphere. In 1995, the CN Tower was declared one of the modern Seven Wonders of the World by the American Society of Civil Engineers. It also belongs to the World Federation of Great Towers.
It is a signature icon of Toronto's skyline and attracts more than two million international visitors annually. It houses several observation decks, a revolving restaurant at some , and an entertainment complex.
== History ==
The original concept of the CN Tower was first conceived in 1968 when the Canadian National Railway wanted to build a large television and radio communication platform to serve the Toronto area, and to demonstrate the strength of Canadian industry and CN in particular. These plans evolved over the next few years, and the project became official in 1972.
The tower would have been part of Metro Centre (see CityPlace), a large development south of Front Street on the Railway Lands, a large railway switching yard that was being made redundant after the opening of the MacMillan Yard north of the city in 1965 (then known as Toronto Yard). Key project team members were NCK Engineering as structural engineer; John Andrews Architects; Webb, Zerafa, Menkes, Housden Architects; Foundation Building Construction; and Canron (Eastern Structural Division).
At the time, most data communications took place over point-to-point microwave links, whose dish antennas covered the roofs of large buildings. As each new skyscraper was added to the downtown, former line-of-sight links were no longer possible. CN intended to rent "hub" space for microwave links, visible from almost any building in the Toronto area.
The original plan for the tower envisioned a tripod consisting of three independent cylindrical "pillars" linked at various heights by structural bridges. Had it been built, this design would have been considerably shorter, with the metal antenna located roughly where the concrete section between the main level and the SkyPod lies today. As the design effort continued, it evolved into the current design with a single continuous hexagonal core to the SkyPod, with three support legs blended into the hexagon below the main level, forming a large Y-shape structure at the ground level.
The idea for the main level in its current form evolved around this time, but the Space Deck (later renamed SkyPod) was not part of the plans until later. One engineer in particular felt that visitors would feel the higher observation deck would be worth paying extra for, and the costs in terms of construction were not prohibitive. Also around this time, it was realized that the tower could become the world's tallest free-standing structure to improve signal quality and attract tourists, and plans were changed to incorporate subtle modifications throughout the structure to this end. a subsidiary of Sweden's Skanska, a global project-development and construction group.
Construction began on February 6, 1973, with massive excavations at the tower base for the foundation. By the time the foundation was complete, of earth and shale were removed to a depth of in the centre, and a base incorporating of concrete with of rebar and of steel cable had been built to a thickness of . This portion of the construction was fairly rapid, with only four months needed between the start and the foundation being ready for construction on top.
==== Phases of construction ====
File:CN Tower footings 1973.jpg|Constructing the base, July 1973
File:Cntower1974.jpg|Brackets being raised, August 1974
File:CN Tower50 construction skycrane March 1975 01d.jpg|Helicopter lifting part of antenna, March 1975
File:CN Tower under construction (April 1975).jpg|Main pod construction, April 1975
File:CN Tower under construction.jpg|Nearing completion, December 1975
File:CN Tower 1976.jpg|Two months after opening, August 1976
=== Opening ===
The CN Tower opened on June 26, 1976. The construction costs of approximately ($ in dollars) were repaid in fifteen years.
From the mid-1970s to the mid-1980s, the CN Tower was practically the only development along Front Street West; it was still possible to see Lake Ontario from the foot of the CN Tower due to the expansive parking lots and lack of development in the area at the time. As the area around the tower was developed, particularly with the completion of the Metro Toronto Convention Centre (north building) in 1984 and SkyDome in 1989 (renamed Rogers Centre in 2005), the former Railway Lands were redeveloped and the tower became the centre of a newly developing entertainment area. Access was greatly improved with the construction of the SkyWalk in 1989, which connected the tower and SkyDome to the nearby Union Station railway and subway station, and, in turn, to the city's Path underground pedestrian system. By the mid-1990s, it was the centre of a thriving tourist district. The entire area continues to be an area of intense building, notably a boom in condominium construction in the first quarter of the 21st century, as well as the 2013 opening of the Ripley's Aquarium by the base of the tower.
The tower would garner worldwide media attention when stuntman Dar Robinson jumped off the CN Tower on two occasions in 1979 and 1980. The first was for a scene from the movie Highpoint, in which Robinson received ($ in dollars) for the stunt. The second was for a personal documentary. The first stunt had him use a parachute which he deployed three seconds before impact with the ground, while the second one used a wire decelerator attached to his back.
On June 26, 1986, the tenth anniversary of the tower's opening, high-rise firefighting and rescue advocate Dan Goodwin, in a sponsored publicity event, used his hands and feet to climb the outside of the tower, a feat he performed twice on the same day. Following both ascents, he used multiple rappels to descend to the ground.
From 1985 to 1992, the CN Tower basement level hosted the world's first flight simulator ride, Tour of the Universe, based on the flight of a Space Shuttle. The ride was replaced in 1992 with a similar attraction entitled "Space Race." It was later dismantled and replaced by two other rides in 1998 and 1999.
=== The 1990s and 2000s ===
A glass floor at an elevation of was installed in 1994. though the tower is commonly called the CN Tower.
Further changes were made from 1997 to January 2004: TrizecHahn Corporation managed the tower and instituted several expansion projects including a entertainment expansion, the 1997 addition of two new elevators (to a total of six) and the consequential relocation of the staircase from the north side leg to inside the core of the building, a conversion that also added nine stairs to the climb. TrizecHahn also owned the Willis Tower (Sears Tower at the time) in Chicago approximately at the same time.
In 2007, light-emitting diode (LED) lights replaced the incandescent lights that lit the CN Tower at night. This was done to take advantage of the cost savings of LED lights over incandescent lights. The colour of the LED lights can change, compared to the constant white colour of the incandescent lights. On September 12, 2007, Burj Khalifa in Dubai, then under construction and known as Burj Dubai, surpassed the CN Tower as the world's tallest free-standing structure on land. In 2008, glass panels were installed in one of the CN Tower elevators, which established a world record () for highest glass floor panelled elevator in the world.
=== 2010s: EdgeWalk ===
On August 1, 2011, the CN Tower opened the EdgeWalk, an amusement in which thrill-seekers can walk on and around the roof of the main pod of the tower at , which is directly above the 360 Restaurant. It is the world's highest full-circle, hands-free walk. Visitors are tethered to an overhead rail system and walk around the edge of the CN Tower's main pod above the 360 Restaurant on a metal floor. The attraction is closed throughout the winter and during periods of electrical storms and high winds.
One of the notable guests who visited EdgeWalk was Canadian comedian Rick Mercer, featured as the first episode of the ninth season of his CBC Television news satire show, Rick Mercer Report. There, he was accompanied by Canadian pop singer Jann Arden. The episode first aired on April 10, 2013.
==== 2015 Pan Am Games ====
The tower and surrounding areas were prominent in the 2015 Pan American Games production. In the opening ceremony, a pre-recorded segment featured track-and-field athlete Bruny Surin passing the flame to sprinter Donovan Bailey on the EdgeWalk and parachuting into Rogers Centre. A fireworks display off the tower concluded both the opening and closing ceremonies.
==== Canada 150 ====
On July 1, 2017, as part of the nationwide celebrations for Canada 150, which celebrated the 150th anniversary of Canadian Confederation, fireworks were once again shot from the tower in a five-minute display coordinated with the tower lights and music broadcast on a local radio station.
=== 2020s ===
The CN Tower closed during much of the COVID-19 pandemic. During much of the pandemic, the gift shop was renovated to take advantage of the tower's closure.
== Closures ==
The CN Tower was closed on September 11, 2001, following the terrorist attacks on the World Trade Center in New York City.
The CN Tower was closed during the G20 summit on June 26–27, 2010, for security reasons, given its proximity to the Metro Toronto Convention Centre and ongoing citywide protests and riots.
The CN Tower was closed from 2020 to 2021 due to COVID-19 pandemic restrictions throughout Ontario.
The CN Tower was closed on December 16, 2021, due to glass falling off from heavy winds.
== Structure ==
The CN Tower consists of several substructures. The main portion of the tower is a hollow concrete hexagonal pillar containing the stairwells and power and plumbing connections. The tower's six elevators are located in the three inverted angles created by the Tower's hexagonal shape (two elevators per angle). Each of the three elevator shafts is lined with glass, allowing for views of the city as the glass-windowed elevators make their way through the tower. The stairwell was originally located in one of these angles (the one facing north), but was moved into the central hollow of the tower; the tower's new fifth and sixth elevators were placed in the hexagonal angle that once contained the stairwell. On top of the main concrete portion of the tower is a tall metal broadcast antenna, carrying television and radio signals. There are three visitor areas: the Glass Floor and Outdoor Observation Terrace, which are both located at an elevation of , the Indoor Lookout Level (formerly known as "Indoor Observation Level") located at , and the higher SkyPod (formerly known as "Space Deck") at , just below the metal antenna. The hexagonal shape is visible between the two highest areas; however, below the main deck, three large supporting legs give the tower the appearance of a large tripod.
The main deck level has seven storeys, some of which are open to the public. Below the public areas—at —is a large white donut-shaped radome containing the structure's UHF transmitters. The glass floor and outdoor observation deck are at . The glass floor has an area of and can withstand a pressure of . The floor's thermal glass units are thick, consisting of a pane of laminated glass, airspace and a pane of laminated glass. In 2008, one elevator was upgraded to add a glass floor panel, believed to have the highest vertical rise of any elevator equipped with this feature. The Horizons Cafe and the lookout level are at . The 360 Restaurant, a revolving restaurant that completes a full rotation once every 72 minutes, is at . When the tower first opened, it also featured a discotheque named Sparkles (at the Indoor Observation Level), billed as the highest disco and dance floor in the world.
The SkyPod was once the highest public observation deck in the world until it was surpassed by the Shanghai World Financial Center in 2008.
A metal staircase reaches the main deck level after 1,776 steps, and the SkyPod above after 2,579 steps; it is the tallest metal staircase on Earth. These stairs are intended for emergency use only except for charity stair-climb events two times during the year. The average climber takes approximately 30 minutes to climb to the base of the radome, but the fastest climb on record is 7 minutes and 52 seconds in 1989 by Brendan Keenoy, an Ontario Provincial Police officer.
File:CN Tower, Toronto, Ontario (29969151776).jpg|Inside 360 Restaurant
File:CN Tower Main Observation Level 2023.jpg|Main Observation Level after renovation in 2018
File:CN Tower Turmkorb-Modell-blau.png|Cross-section of Main Pod
File:Inside the skypod of the CN Tower (27287339323).jpg|Skypod
File:CN Tower Terrace Level after renovation in 2023.jpg|Terrace Level glass floor
File:CNTowerNastyFall.jpg|View through glass floor
File:CN Tower Gift Shop after renovation 2023.jpg|Gift shop in 2023
File:CN Tower Ground View Looking Up.png|Ground view looking up at the CN Tower.
=== Architects ===
WZMH Architects
John Hamilton Andrews
Webb Zerafa
Menkes Housden with the help of Edward R. Baldwin
=== Falling ice danger ===
A freezing rain storm on March 2, 2007, resulted in a layer of ice several centimetres thick forming on the side of the tower and other downtown buildings. The sun thawed the ice, then winds of up to blew some of it away from the structure. There were fears that cars and windows of nearby buildings would be smashed by large chunks of ice. In response, police closed some streets surrounding the tower. During morning rush hour on March 5 of the same year, police expanded the area of closed streets to include the Gardiner Expressway away from the tower as increased winds blew the ice farther, as far north as King Street West, away, where a taxicab window was shattered. Subsequently, on March 6, 2007, the Gardiner Expressway reopened after winds abated.
On April 16, 2018, falling ice from the CN Tower punctured the roof of the nearby Rogers Centre stadium, causing the Toronto Blue Jays to postpone the game that day to the following day as a doubleheader; this was the third doubleheader held at the Rogers Centre. On April 20 of the same year, the CN Tower reopened.
=== Safety features ===
In August 2000, a fire broke out at the Ostankino Tower in Moscow, killing three people and causing extensive damage. The fire was blamed on poor maintenance and outdated equipment. The failure of the fire-suppression systems and the lack of proper equipment for firefighters allowed the fire to destroy most of the interior and sparked fears the tower might even collapse.
The Ostankino Tower was completed nine years before the CN Tower and is only shorter. The parallels between the towers led to some concern that the CN Tower could be at risk of a similar tragedy. However, Canadian officials subsequently stated that it is "highly unlikely" that a similar disaster could occur at the CN Tower, as it has important safeguards that were not present in the Ostankino Tower. Specifically, officials cited:
the fireproof building materials used in the tower's construction,
frequent and stringent safety inspections,
an extensive sprinkler system,
a 24-hour emergency monitoring operation,
two 68,160-litre (15,000-imperial gallon; 18,006-US gallon) water reservoirs at the top, which are automatically replenished,
a fire hose at the base of the structure capable of sending to any location in the tower,
a ban on natural gas appliances anywhere in the tower (including the restaurant in the main pod),
an elevator that can be used during a fire as it runs up the outside of the building and can be powered by three emergency generators at the base of the structure (unlike the elevator at the Ostankino Tower, which malfunctioned).
Officials also noted that the CN Tower has an excellent safety record, although there was an electrical fire in the antennas on August 16, 2017 — the tower's first fire. Moreover, other supertall structures built between 1967 and 1976 — such as the Willis Tower (formerly the Sears Tower), the World Trade Center (until its destruction on September 11, 2001), the Fernsehturm Berlin, the Aon Center, 875 North Michigan Avenue (formerly the John Hancock Center), and First Canadian Place — also have excellent safety records, which suggests that the Ostankino Tower accident was a rare safety failure, and that the likelihood of similar events occurring at other supertall structures is extremely low.
== Lighting ==
The CN Tower was originally lit at night with incandescent lights, which were removed in 1997 because they were inefficient and expensive to repair. In June 2007, the tower was outfitted with 1,330 super-bright LED lights inside the elevator shafts, shooting over the main pod and upward to the top of the tower's mast to light the tower from dusk until 2 a.m. the next calendar day. The official opening ceremony took place on June 28, 2007, before the Canada Day holiday weekend.
The tower changes its lighting scheme on holidays and to commemorate major events. After the 95th Grey Cup in Toronto, the tower was lit in green and white to represent the colours of the Grey Cup champion Saskatchewan Roughriders. From sundown on August 27, 2011, to sunrise the following day, the tower was lit in orange, the official colour of the New Democratic Party (NDP), to commemorate the death of federal NDP leader and leader of the official opposition Jack Layton. When former South African president Nelson Mandela died, the tower was lit in the colours of the South African flag. When former federal finance minister under Stephen Harper's Conservatives Jim Flaherty died, the tower was lit in green to reflect his Irish Canadian heritage. On the night of the attacks on Paris on November 13, 2015, the tower displayed the colours of the French flag. On June 8, 2021, the tower displayed the colours of the Toronto Maple Leafs' archrivals Montreal Canadiens after they advanced to the semifinals of 2021 Stanley Cup playoffs. The CN Tower was lit in the colours of the Ukrainian flag during the beginning of the Russian invasion of Ukraine in late February 2022.
Programmed remotely from a desktop computer with a wireless network interface controller in Burlington, Ontario, the LEDs use less energy to light than the previous incandescent lights (10% less energy than the dimly lit version and 60% less than the brightly lit version). The estimated cost to use the LEDs is $1,000 per month.
During the spring and autumn bird migration seasons, the lights are turned off to comply with the voluntary Fatal Light Awareness Program, which "encourages buildings to dim unnecessary exterior lighting to mitigate bird mortality during spring and summer migration."
== Height comparisons ==
The CN Tower is the tallest freestanding structure in the Western Hemisphere. As of 2013, there were two other freestanding structures in the Western Hemisphere exceeding in height: the Willis Tower in Chicago, which stands at when measured to its pinnacle, and One World Trade Center in New York City, which has a pinnacle height of , or approximately shorter than the CN Tower. Due to the symbolism of the number 1776 (the year of the signing of the United States Declaration of Independence), the height of One World Trade Center is unlikely to be increased. The proposed Chicago Spire was expected to exceed the height of the CN Tower, but its construction was halted early due to financial difficulties amid the Great Recession, and was eventually cancelled in 2010.
=== Height distinction debate ===
==== "World's Tallest Tower" title ====
Guinness World Records has called the CN Tower "the world's tallest self-supporting tower" and "the world's tallest free-standing tower". Although Guinness did list this description of the CN Tower under the heading "tallest building" at least once, The issue of what was tallest became moot when Burj Khalifa, then under construction, exceeded the height of the CN Tower in 2007 (see below).
Although the CN Tower contains a restaurant, a gift shop and multiple observation levels, it does not have floors continuously from the ground, and therefore it is not considered a building by the Council on Tall Buildings and Urban Habitat (CTBUH) or Emporis. CTBUH defines a building as "a structure that is designed for residential, business, or manufacturing purposes. An essential characteristic of a building is that it has floors." The tower definition used by Guinness was defined by the Council on Tall Buildings and Urban Habitat as 'a building in which less than 50% of the construction is usable floor space'. Guinness World Records editor-in-chief Craig Glenday announced that Burj Khalifa was not classified as a tower because it has too much usable floor space to be considered to be a tower. CN Tower still held world records for highest above ground wine cellar (in 360 Restaurant) at 351 m, highest above-ground restaurant at 346 m (Horizons Restaurant), and tallest free-standing concrete tower during Guinness's recertification. The CN Tower was surpassed in 2009 by the Canton Tower in Guangzhou, China, which stands at tall, as the world's tallest tower; which in turn was surpassed by the Tokyo Skytree in 2011, which currently is the tallest tower at in height. The CN Tower, as of 2022, stands as the tenth-tallest free-standing structure on land, remains the tallest free-standing structure in the Western Hemisphere, and is the third-tallest tower. The CN Tower is the second-tallest free-standing structure in the Commonwealth of Nations behind Merdeka 118 in Kuala Lumpur, Malaysia.
==== Height records ====
Since its construction, the tower has gained the following world height records:
== Use ==
The CN Tower has been and continues to be used as a communications tower for a number of different media and by numerous companies.
=== Television broadcasters ===
{| class="wikitable sortable"
|-
!VHF
!UHF
!Virtual
!Callsign
!Affiliation
!Branding
|-
|9
|—
|9.1
|CFTO-DT
|CTV
|CTV Toronto
|-
|—
|19
|19.1
|CICA-DT
|TVO
|TVO
|-
|—
|20
|5.1
|CBLT-DT
|CBC Television
|CBC Toronto
|-
|—
|25
|25.1
|CBLFT-DT
|Ici Radio-Canada Télé
|ICI Ontario
|-
|—
|40
|40.1
|CJMT-DT
|Omni Television
|Omni.2
|-
|—
|41
|41.1
|CIII-DT-41
|Global
|Global Toronto
|-
|—
|44
|57.1
|CITY-DT
|Citytv
|Citytv Toronto
|-
|—
|47
|47.1
|CFMT-DT
|Omni Television
|Omni.1
|-
| colspan="6" style="text-align: center;" | Source: Vividcomm The FM transmitters are situated in a metal broadcast antenna, on top of the main concrete portion of the tower at an elevation above from the ground.
{| class="wikitable sortable"
!Frequency
!kW
!Callsign
!Affiliation/Owner
!Branding
!Notes
|-
|91.1 MHz
|40
|CJRT
|Independent; Public
|JAZZ.FM91
|Jazz
|-
|94.1 MHz
|38
|CBL
|Canadian Broadcasting Corporation
|CBC Music
|Non-commercial; classical; jazz
|-
|97.3 MHz
|28.9
|CHBM
|Stingray Group
|boom 97.3
|Classic hits
|-
|98.1 MHz
|44
|CHFI
|Rogers Sports & Media
|98.1 CHFI
|Adult contemporary
|-
|99.9 MHz
|40
|CKFM
|Bell Media
|Virgin Radio 99.9FM
|Top 40/Contemporary hits
|-
|100.7 MHz
|4
|CHIN
|CHIN Radio/TV International
|CHIN Radio
|Primarily in Italian and Portuguese
|-
|102.1 MHz
|35
|CFNY
|Corus Entertainment
|102.1 the Edge
|Alternative rock
|-
|104.5 MHz
|40
|CHUM
|Bell Media
|104.5 CHUM FM
|Hot adult contemporary
|-
|107.1 MHz
|40
|CILQ
|Corus Entertainment
|Classic Rock Q 107
|Mainstream rock
|-
| colspan="6" style="text-align: center;" | Source: Vividcomm
== In popular culture ==
The CN Tower has been featured in numerous films, television shows, music recording covers, and video games. The tower also has its own official mascot, which resembles the tower itself.
Highpoint is a Canadian 1982 action film starring Richard Harris, Christopher Plummer and Beverly D'Angelo. It features a shot of stuntman Dar Robinson jumping off of the CN Tower in 1979. Drake appeared significantly larger than life-size on the cover, and the CN Tower's Twitter account later confirmed it to be photo edited.
|
[
"First Canadian Place",
"Dar Robinson",
"Kuala Lumpur",
"List of tallest buildings in Toronto",
"PartyNextDoor",
"Institute of Electrical and Electronics Engineers",
"Green",
"World Wide Fund for Nature",
"Dan Goodwin",
"Blue",
"COVID-19 pandemic",
"KVLY-TV mast",
"Mississippi River Delta",
"November 2015 Paris attacks",
"National Post",
"Incandescent light bulb",
"Petronius (oil platform)",
"Corus Entertainment",
"President of South Africa",
"FM broadcasting",
"Alternative rock",
"soil",
"Sterling Publishing",
"Toronto Islands",
"White",
"Divestment",
"Alzheimer's disease",
"Hot adult contemporary",
"Amateur radio",
"wire rope",
"glass floor",
"Views (album)",
"2010 G20 Toronto summit protests",
"Canadian Confederation",
"Bell Media",
"Bank of Montreal",
"John Hancock Center",
"List of tallest buildings",
"Path (Toronto)",
"The Hahn Company",
"Rick Mercer",
"Jann Arden",
"Toronto",
"skyline",
"King Street (Toronto)",
"Death and state funeral of Nelson Mandela",
"High-rise building",
"Jeff Adams",
"Jack Layton",
"Moscow",
"Russian invasion of Ukraine",
"Shades of blue",
"Citytv",
"Chicago Spire",
"WZMH Architects",
"Western Hemisphere",
"oil platform",
"Manhattanization",
"CBL-FM",
"Christopher Plummer",
"Winter solstice",
"Italian language",
"The Independent",
"Tour of the Universe",
"New Year's Eve",
"Drake (musician)",
"Bird migration",
"Bloomberg Businessweek",
"Canton Tower",
"CBC News",
"Fernsehturm Berlin",
"Shanghai",
"Architecture of Toronto",
"tower",
"Stephen Harper",
"United States Army",
"shale",
"Bell Canada",
"Canada Lands Company",
"2010 G20 Toronto summit",
"simulator ride",
"Toronto Star",
"Bruny Surin",
"List of tallest buildings and structures",
"Photograph manipulation",
"Foundation Company of Canada",
"Ultra high frequency",
"University of Toronto Press",
"List of tallest towers",
"COVID-19 pandemic in Toronto",
"WP:NOTBROKEN",
"CBC Music",
"privatization",
"September 11 attacks",
"Rogers Centre",
"United States Declaration of Independence",
"Sikorsky S-64 Skycrane",
"Guangzhou",
"CBLT-DT",
"Death and state funeral of Jack Layton",
"CICA-DT",
"rebar",
"List of tallest freestanding structures",
"Ici Radio-Canada Télé",
"The Daily Telegraph",
"wireless network interface controller",
"The Canadian Press",
"Emporis",
"Omni Television",
"Contemporary hit radio",
"Inco Superstack",
"CILQ-FM",
"Global Television Network",
"CFNY-FM",
"The Sports Network",
"World Trade Center (1973–2001)",
"Oriental Pearl Tower",
"Yellow",
"Wonders of the World",
"plumb bob",
"Willis Tower",
"Irish Canadians",
"elevator",
"2015 Pan American Games",
"2015 Pan American Games opening ceremony",
"Aon Center (Chicago)",
"Financial District, Toronto",
"TVO",
"light-emitting diode",
"news satire",
"Burlington, Ontario",
"CITY-DT",
"Flag of France",
"Gardiner Expressway",
"Commonwealth of Nations",
"Toronto Transit Commission",
"Union station (TTC)",
"Highpoint (film)",
"American Society of Civil Engineers",
"National Day of Remembrance and Action on Violence Against Women",
"radio masts and towers",
"Canada Day",
"CIII-DT",
"Nelson Mandela",
"Council on Tall Buildings and Urban Habitat",
"Slip forming",
"150th anniversary of Canada",
"Valentine's Day",
"CTV Television Network",
"CKFM-FM",
"Federal Communications Commission",
"observation deck",
"World AIDS Day",
"CJRT-FM",
"Ontario",
"Christmas and holiday season",
"Conservative Party of Canada",
"Billy Bishop Toronto City Airport",
"Red",
"MacMillan Yard",
"Saskatchewan Roughriders",
"CHBM-FM",
"Twitter",
"downtown Toronto",
"Public radio",
"YouTube",
"freezing rain",
"CHFI-FM",
"Greater Sudbury",
"Skanska",
"Union Station (Toronto)",
"Toronto Blue Jays",
"CFMT-DT",
"Las Vegas",
"Ripley's Aquarium of Canada",
"CBLFT-DT",
"Flag of South Africa",
"London",
"Stingray Group",
"Classic hits",
"List of tallest structures",
"Documentary film",
"New Democratic Party",
"CBC Television",
"Very high frequency",
"CHIN Radio/TV International",
"Toronto Maple Leafs",
"condominium",
"CityPlace, Toronto",
"Stairs",
"Gulf of Mexico",
"Jim Flaherty",
"CFTO-DT",
"SkyscraperPage",
"guy-wire",
"bird migration",
"Dotdash",
"Canadian property bubble",
"Doubleheader (baseball)",
"List of tallest structures in Canada",
"Montreal Canadiens",
"Mainstream rock",
"The Strat",
"Guinness World Records",
"Shanghai World Financial Center",
"Paralympic Games",
"Merdeka 118",
"desktop computer",
"Great Recession",
"SkyWalk",
"Ostankino Tower",
"tripod",
"CHUM-FM",
"Adult contemporary music",
"Burj Khalifa",
"Rick Mercer Report",
"Orange (colour)",
"Saint Patrick's Day",
"Classical music",
"Malaysia",
"Ontario Provincial Police",
"Microwave",
"Human Rights Day",
"One World Trade Center",
"Jazz",
"Dubai",
"taxicab",
"John Andrews (architect)",
"repeater",
"95th Grey Cup",
"Rogers Sports & Media",
"Taipei 101",
"buoyancy",
"Reuters",
"St. Andrew station",
"Blanchard, North Dakota",
"Metro Toronto Convention Centre",
"Purple",
"Minister of Finance (Canada)",
"AM broadcasting",
"Portuguese language",
"National Geographic",
"Crown corporation",
"radome",
"CJMT-DT",
"The New York Times",
"Flag of Ukraine",
"CHIN-FM",
"Paris",
"Front Street (Toronto)",
"World Cancer Day",
"Tokyo Skytree",
"Railway Lands",
"Canadian National Railway",
"Canadian Broadcasting Corporation",
"Antenna (radio)",
"2021 Stanley Cup playoffs",
"Space Shuttle",
"Donovan Bailey",
"Beverly D'Angelo",
"Eiffel Tower",
"Richard Harris",
"revolving restaurant",
"wheelchair"
] |
6,113 |
Chain rule
|
In calculus, the chain rule is a formula that expresses the derivative of the composition of two differentiable functions and in terms of the derivatives of and . More precisely, if h=f\circ g is the function such that h(x)=f(g(x)) for every , then the chain rule is, in Lagrange's notation,
h'(x) = f'(g(x)) g'(x).
or, equivalently,
h'=(f\circ g)'=(f'\circ g)\cdot g'.
The chain rule may also be expressed in Leibniz's notation. If a variable depends on the variable , which itself depends on the variable (that is, and are dependent variables), then depends on as well, via the intermediate variable . In this case, the chain rule is expressed as
\frac{dz}{dx} = \frac{dz}{dy} \cdot \frac{dy}{dx},
and
\left.\frac{dz}{dx}\right|_{x} = \left.\frac{dz}{dy}\right|_{y(x)}
\cdot \left. \frac{dy}{dx}\right|_{x} ,
for indicating at which points the derivatives have to be evaluated.
In integration, the counterpart to the chain rule is the substitution rule.
==Intuitive explanation==
Intuitively, the chain rule states that knowing the instantaneous rate of change of relative to and that of relative to allows one to calculate the instantaneous rate of change of relative to as the product of the two rates of change.
As put by George F. Simmons: "If a car travels twice as fast as a bicycle and the bicycle is four times as fast as a walking man, then the car travels 2 × 4 = 8 times as fast as the man."
The relationship between this example and the chain rule is as follows. Let , and be the (variable) positions of the car, the bicycle, and the walking man, respectively. The rate of change of relative positions of the car and the bicycle is \frac {dz}{dy}=2. Similarly, \frac {dy}{dx}=4. So, the rate of change of the relative positions of the car and the walking man is
\frac{dz}{dx}=\frac{dz}{dy}\cdot\frac{dy}{dx}=2\cdot 4=8.
The rate of change of positions is the ratio of the speeds, and the speed is the derivative of the position with respect to the time; that is,
\frac{dz}{dx}=\frac \frac{dz}{dt}\frac{dx}{dt},
or, equivalently,
\frac{dz}{dt}=\frac{dz}{dx}\cdot \frac{dx}{dt},
which is also an application of the chain rule.
== History ==
The chain rule seems to have first been used by Gottfried Wilhelm Leibniz. He used it to calculate the derivative of \sqrt{a + bz + cz^2} as the composite of the square root function and the function a + bz + cz^2\!. He first mentioned it in a 1676 memoir (with a sign error in the calculation). The common notation of the chain rule is due to Leibniz. Guillaume de l'Hôpital used the chain rule implicitly in his Analyse des infiniment petits. The chain rule does not appear in any of Leonhard Euler's analysis books, even though they were written over a hundred years after Leibniz's discovery.. It is believed that the first "modern" version of the chain rule appears in Lagrange's 1797 Théorie des fonctions analytiques; it also appears in Cauchy's 1823 Résumé des Leçons données a L’École Royale Polytechnique sur Le Calcul Infinitesimal.
(f\circ g)'(c) = f'(g(c))\cdot g'(c).
The rule is sometimes abbreviated as
(f\circ g)' = (f'\circ g) \cdot g'.
If and , then this abbreviated form is written in Leibniz notation as:
\frac{dy}{dx} = \frac{dy}{du} \cdot \frac{du}{dx}.
The points where the derivatives are evaluated may also be stated explicitly:
\left.\frac{dy}{dx}\right|_{x=c} = \left.\frac{dy}{du}\right|_{u = g(c)} \cdot \left.\frac{du}{dx}\right|_{x=c}.
Carrying the same reasoning further, given functions f_1, \ldots, f_n\! with the composite function f_1 \circ ( f_2 \circ \cdots (f_{n-1} \circ f_n) )\!, if each function f_i\! is differentiable at its immediate input, then the composite function is also differentiable by the repeated application of Chain Rule, where the derivative is (in Leibniz's notation):
\frac{df_1}{dx} = \frac{df_1}{df_2}\frac{df_2}{df_3}\cdots\frac{df_n}{dx}.
== Applications ==
=== Composites of more than two functions ===
The chain rule can be applied to composites of more than two functions. To take the derivative of a composite of more than two functions, notice that the composite of , , and ' (in that order) is the composite of with . The chain rule states that to compute the derivative of , it is sufficient to compute the derivative of ' and the derivative of . The derivative of can be calculated directly, and the derivative of can be calculated by applying the chain rule again.
For concreteness, consider the function
y = e^{\sin (x^2)}.
This can be decomposed as the composite of three functions:
\begin{align}
y &= f(u) = e^u, \\
u &= g(v) = \sin v, \\
v &= h(x) = x^2.
\end{align}
So that y = f(g(h(x))) .
Their derivatives are:
\begin{align}
\frac{dy}{du} &= f'(u) = e^u, \\
\frac{du}{dv} &= g'(v) = \cos v, \\
\frac{dv}{dx} &= h'(x) = 2x.
\end{align}
The chain rule states that the derivative of their composite at the point is:
\begin{align}
(f \circ g \circ h)'(a) & = f'((g \circ h)(a)) \cdot (g \circ h)'(a) \\
& = f'((g \circ h)(a)) \cdot g'(h(a)) \cdot h'(a) \\
& = (f' \circ g \circ h)(a) \cdot (g' \circ h)(a) \cdot h'(a).
\end{align}
In Leibniz's notation, this is:
\frac{dy}{dx} = \left.\frac{dy}{du}\right|_{u=g(h(a))}\cdot\left.\frac{du}{dv}\right|_{v=h(a)}\cdot\left.\frac{dv}{dx}\right|_{x=a},
or for short,
\frac{dy}{dx} = \frac{dy}{du}\cdot\frac{du}{dv}\cdot\frac{dv}{dx}.
The derivative function is therefore:
\frac{dy}{dx} = e^{\sin(x^2)}\cdot\cos(x^2)\cdot 2x.
Another way of computing this derivative is to view the composite function as the composite of and h. Applying the chain rule in this manner would yield:
\begin{align}
(f \circ g \circ h)'(a) &= (f \circ g)'(h(a)) \cdot h'(a) \\
&= f'(g(h(a))) \cdot g'(h(a)) \cdot h'(a).
\end{align}
This is the same as what was computed above. This should be expected because .
Sometimes, it is necessary to differentiate an arbitrarily long composition of the form f_1 \circ f_2 \circ \cdots \circ f_{n-1} \circ f_n\!. In this case, define
f_{a\,.\,.\,b} = f_{a} \circ f_{a+1} \circ \cdots \circ f_{b-1} \circ f_{b}
where f_{a\,.\,.\,a} = f_a and f_{a\,.\,.\,b}(x) = x when b < a. Then the chain rule takes the form
\begin{align}
Df_{1\,.\,.\,n}
&= (Df_1 \circ f_{2\,.\,.\,n}) (Df_2 \circ f_{3\,.\,.\,n}) \cdots (Df_{n-1} \circ f_{n\,.\,.\,n}) Df_n \\
&= \prod_{k=1}^n \left[Df_k \circ f_{(k+1)\,.\,.\,n}\right]
\end{align}
or, in the Lagrange notation,
\begin{align}
f_{1\,.\,.\,n}'(x)
&= f_1' \left( f_{2\,.\,.\,n}(x) \right) \; f_2' \left( f_{3\,.\,.\,n}(x) \right) \cdots f_{n-1}' \left(f_{n\,.\,.\,n}(x)\right) \; f_n'(x) \\[1ex]
&= \prod_{k=1}^{n} f_k' \left(f_{(k+1\,.\,.\,n)}(x) \right)
\end{align}
=== Quotient rule ===
The chain rule can be used to derive some well-known differentiation rules. For example, the quotient rule is a consequence of the chain rule and the product rule. To see this, write the function as the product . First apply the product rule:
\begin{align}
\frac{d}{dx}\left(\frac{f(x)}{g(x)}\right)
&= \frac{d}{dx}\left(f(x)\cdot\frac{1}{g(x)}\right) \\
&= f'(x)\cdot\frac{1}{g(x)} + f(x)\cdot\frac{d}{dx}\left(\frac{1}{g(x)}\right).
\end{align}
To compute the derivative of , notice that it is the composite of with the reciprocal function, that is, the function that sends to . The derivative of the reciprocal function is -1/x^2\!. By applying the chain rule, the last expression becomes:
f'(x)\cdot\frac{1}{g(x)} + f(x)\cdot\left(-\frac{1}{g(x)^2}\cdot g'(x)\right)
= \frac{f'(x) g(x) - f(x) g'(x)}{g(x)^2},
which is the usual formula for the quotient rule.
=== Derivatives of inverse functions ===
Suppose that has an inverse function. Call its inverse function so that we have . There is a formula for the derivative of in terms of the derivative of . To see this, note that and satisfy the formula
f(g(x)) = x.
And because the functions f(g(x)) and are equal, their derivatives must be equal. The derivative of is the constant function with value 1, and the derivative of f(g(x)) is determined by the chain rule. Therefore, we have that:
f'(g(x)) g'(x) = 1.
To express as a function of an independent variable , we substitute f(y) for wherever it appears. Then we can solve for .
\begin{align}
f'(g(f(y))) g'(f(y)) &= 1 \\
f'(y) g'(f(y)) &= 1 \\
f'(y) = \frac{1}{g'(f(y))}.
\end{align}
For example, consider the function . It has an inverse . Because , the above formula says that
\frac{d}{dy}\ln y = \frac{1}{e^{\ln y}} = \frac{1}{y}.
This formula is true whenever is differentiable and its inverse is also differentiable. This formula can fail when one of these conditions is not true. For example, consider . Its inverse is , which is not differentiable at zero. If we attempt to use the above formula to compute the derivative of at zero, then we must evaluate . Since and , we must evaluate 1/0, which is undefined. Therefore, the formula fails in this case. This is not surprising because is not differentiable at zero.
=== Back propagation ===
The chain rule forms the basis of the back propagation algorithm, which is used in gradient descent of neural networks in deep learning (artificial intelligence).
== Higher derivatives ==
Faà di Bruno's formula generalizes the chain rule to higher derivatives. Assuming that and , then the first few derivatives are:
\begin{align}
\frac{dy}{dx} & = \frac{dy}{du} \frac{du}{dx} \\
\frac{d^2 y }{d x^2} & =
\frac{d^2 y}{d u^2} \left(\frac{du}{dx}\right)^2
+ \frac{dy}{du} \frac{d^2 u}{dx^2} \\
\frac{d^3 y }{d x^3} & =
\frac{d^3 y}{d u^3} \left(\frac{du}{dx}\right)^3
+ 3 \, \frac{d^2 y}{d u^2} \frac{du}{dx} \frac{d^2 u}{d x^2}
+ \frac{dy}{du} \frac{d^3 u}{d x^3} \\
\frac{d^4 y}{d x^4} & =
\frac{d^4 y}{du^4} \left(\frac{du}{dx}\right)^4
+ 6 \, \frac{d^3 y}{d u^3} \left(\frac{du}{dx}\right)^2 \frac{d^2 u}{d x^2}
+ \frac{d^2 y}{d u^2} \left( 4 \, \frac{du}{dx} \frac{d^3 u}{dx^3}
+ 3 \, \left(\frac{d^2 u}{dx^2}\right)^2\right)
+ \frac{dy}{du} \frac{d^4 u}{dx^4}.
\end{align}
== Proofs ==
=== First proof ===
One proof of the chain rule begins by defining the derivative of the composite function , where we take the limit of the difference quotient for as approaches :
(f \circ g)'(a) = \lim_{x \to a} \frac{f(g(x)) - f(g(a))}{x - a}.
Assume for the moment that g(x)\! does not equal g(a) for any x near a. Then the previous expression is equal to the product of two factors:
\lim_{x \to a} \frac{f(g(x)) - f(g(a))}{g(x) - g(a)} \cdot \frac{g(x) - g(a)}{x - a}.
If g oscillates near , then it might happen that no matter how close one gets to , there is always an even closer such that . For example, this happens near for the continuous function defined by for and otherwise. Whenever this happens, the above expression is undefined because it involves division by zero. To work around this, introduce a function Q as follows:
Q(y) = \begin{cases}
\displaystyle\frac{f(y) - f(g(a))}{y - g(a)}, & y \neq g(a), \\
f'(g(a)), & y = g(a).
\end{cases}
We will show that the difference quotient for is always equal to:
Q(g(x)) \cdot \frac{g(x) - g(a)}{x - a}.
Whenever is not equal to , this is clear because the factors of cancel. When equals , then the difference quotient for is zero because equals , and the above product is zero because it equals times zero. So the above product is always equal to the difference quotient, and to show that the derivative of at exists and to determine its value, we need only show that the limit as goes to of the above product exists and determine its value.
To do this, recall that the limit of a product exists if the limits of its factors exist. When this happens, the limit of the product of these two factors will equal the product of the limits of the factors. The two factors are and . The latter is the difference quotient for at , and because is differentiable at by assumption, its limit as tends to exists and equals .
As for , notice that is defined wherever ' is. Furthermore, ' is differentiable at by assumption, so is continuous at , by definition of the derivative. The function is continuous at because it is differentiable at , and therefore is continuous at . So its limit as ' goes to ' exists and equals , which is .
This shows that the limits of both factors exist and that they equal and , respectively. Therefore, the derivative of at a exists and equals .
=== Second proof ===
Another way of proving the chain rule is to measure the error in the linear approximation determined by the derivative. This proof has the advantage that it generalizes to several variables. It relies on the following equivalent definition of differentiability at a point: A function g is differentiable at a if there exists a real number g′(a) and a function ε(h) that tends to zero as h tends to zero, and furthermore
g(a + h) - g(a) = g'(a) h + \varepsilon(h) h.
Here the left-hand side represents the true difference between the value of g at a and at , whereas the right-hand side represents the approximation determined by the derivative plus an error term.
In the situation of the chain rule, such a function ε exists because g is assumed to be differentiable at a. Again by assumption, a similar function also exists for f at g(a). Calling this function η, we have
f(g(a) + k) - f(g(a)) = f'(g(a)) k + \eta(k) k.
The above definition imposes no constraints on η(0), even though it is assumed that η(k) tends to zero as k tends to zero. If we set , then η is continuous at 0.
Proving the theorem requires studying the difference as h tends to zero. The first step is to substitute for using the definition of differentiability of g at a:
f(g(a + h)) - f(g(a)) = f(g(a) + g'(a) h + \varepsilon(h) h) - f(g(a)).
The next step is to use the definition of differentiability of f at g(a). This requires a term of the form for some k. In the above equation, the correct k varies with h. Set and the right hand side becomes . Applying the definition of the derivative gives:
f(g(a) + k_h) - f(g(a)) = f'(g(a)) k_h + \eta(k_h) k_h.
To study the behavior of this expression as h tends to zero, expand kh. After regrouping the terms, the right-hand side becomes:
f'(g(a)) g'(a)h + [f'(g(a)) \varepsilon(h) + \eta(k_h) g'(a) + \eta(k_h) \varepsilon(h)] h.
Because ε(h) and η(kh) tend to zero as h tends to zero, the first two bracketed terms tend to zero as h tends to zero. Applying the same theorem on products of limits as in the first proof, the third bracketed term also tends zero. Because the above expression is equal to the difference , by the definition of the derivative is differentiable at a and its derivative is
The role of Q in the first proof is played by η in this proof. They are related by the equation:
Q(y) = f'(g(a)) + \eta(y - g(a)).
The need to define Q at g(a) is analogous to the need to define η at zero.
=== Third proof ===
Constantin Carathéodory's alternative definition of the differentiability of a function can be used to give an elegant proof of the chain rule.
Under this definition, a function is differentiable at a point if and only if there is a function , continuous at and such that . There is at most one such function, and if is differentiable at then .
Given the assumptions of the chain rule and the fact that differentiable functions and compositions of continuous functions are continuous, we have that there exist functions , continuous at , and , continuous at , and such that,
f(g(x))-f(g(a))=q(g(x))(g(x)-g(a))
and
g(x)-g(a)=r(x)(x-a).
Therefore,
f(g(x))-f(g(a))=q(g(x))r(x)(x-a),
but the function given by is continuous at , and we get, for this
(f(g(a)))'=q(g(a))r(a)=f'(g(a))g'(a).
A similar approach works for continuously differentiable (vector-)functions of many variables. This method of factoring also allows a unified approach to stronger forms of differentiability, when the derivative is required to be Lipschitz continuous, Hölder continuous, etc. Differentiation itself can be viewed as the polynomial remainder theorem (the little Bézout theorem, or factor theorem), generalized to an appropriate class of functions.
=== Proof via infinitesimals ===
If y=f(x) and x=g(t) then choosing infinitesimal \Delta t\not=0 we compute the corresponding \Delta x=g(t+\Delta t)-g(t) and then the corresponding \Delta y=f(x+\Delta x)-f(x), so that
\frac{\Delta y}{\Delta t} = \frac{\Delta y}{\Delta x} \frac{\Delta x}{\Delta t}
and applying the standard part we obtain
\frac{d y}{d t}=\frac{d y}{d x} \frac{dx}{dt}
which is the chain rule.
== Multivariable case ==
The full generalization of the chain rule to multi-variable functions (such as f : \mathbb{R}^m \to \mathbb{R}^n) is rather technical. However, it is simpler to write in the case of functions of the form
f(g_1(x), \dots, g_k(x)),
where f : \reals^k \to \reals, and g_i : \mathbb{R} \to \mathbb{R} for each i = 1, 2, \dots, k.
As this case occurs often in the study of functions of a single variable, it is worth describing it separately.
===Case of scalar-valued functions with multiple inputs===
Let f : \reals^k \to \reals, and g_i : \mathbb{R} \to \mathbb{R} for each i = 1, 2, \dots, k.
To write the chain rule for the composition of functions
x \mapsto f(g_1(x), \dots , g_k(x)),
one needs the partial derivatives of with respect to its arguments. The usual notations for partial derivatives involve names for the arguments of the function. As these arguments are not named in the above formula, it is simpler and clearer to use D-Notation, and to denote by
D_i f
the partial derivative of with respect to its th argument, and by
D_i f(z)
the value of this derivative at .
With this notation, the chain rule is
\frac{d}{dx}f(g_1(x), \dots, g_k (x))=\sum_{i=1}^k \left(\frac{d}{dx}{g_i}(x)\right) D_i f(g_1(x), \dots, g_k (x)).
====Example: arithmetic operations====
If the function is addition, that is, if
f(u,v)=u+v,
then D_1 f = \frac{\partial f}{\partial u} = 1 and D_2 f = \frac{\partial f}{\partial v} = 1. Thus, the chain rule gives
\frac{d}{dx}(g(x)+h(x)) = \left( \frac{d}{dx}g(x) \right) D_1 f+\left( \frac{d}{dx}h(x)\right) D_2 f=\frac{d}{dx}g(x) +\frac{d}{dx}h(x).
For multiplication
f(u,v)=uv,
the partials are D_1 f = v and D_2 f = u. Thus,
\frac{d}{dx}(g(x)h(x)) = h(x) \frac{d}{dx} g(x) + g(x) \frac{d}{dx} h(x).
The case of exponentiation
f(u,v)=u^v
is slightly more complicated, as
D_1 f = vu^{v-1},
and, as u^v=e^{v\ln u},
D_2 f = u^v\ln u.
It follows that
\frac{d}{dx}\left(g(x)^{h(x)}\right) = h(x)g(x)^{h(x)-1} \frac{d}{dx}g(x) + g(x)^{h(x)} \ln g(x) \,\frac{d}{dx}h(x).
===General rule: Vector-valued functions with multiple inputs===
The simplest way for writing the chain rule in the general case is to use the total derivative, which is a linear transformation that captures all directional derivatives in a single formula. Consider differentiable functions and , and a point in . Let denote the total derivative of at and denote the total derivative of at . These two derivatives are linear transformations and , respectively, so they can be composed. The chain rule for total derivatives is that their composite is the total derivative of at :
D_{\mathbf{a}}(f \circ g) = D_{g(\mathbf{a})}f \circ D_{\mathbf{a}}g,
or for short,
D(f \circ g) = Df \circ Dg.
The higher-dimensional chain rule can be proved using a technique similar to the second proof given above.
Because the total derivative is a linear transformation, the functions appearing in the formula can be rewritten as matrices. The matrix corresponding to a total derivative is called a Jacobian matrix, and the composite of two derivatives corresponds to the product of their Jacobian matrices. From this perspective the chain rule therefore says:
J_{f \circ g}(\mathbf{a}) = J_{f}(g(\mathbf{a})) J_{g}(\mathbf{a}),
or for short,
J_{f \circ g} = (J_f \circ g)J_g.
That is, the Jacobian of a composite function is the product of the Jacobians of the composed functions (evaluated at the appropriate points).
The higher-dimensional chain rule is a generalization of the one-dimensional chain rule. If , , and are 1, so that and , then the Jacobian matrices of and are . Specifically, they are:
\begin{align}
J_g(a) &= \begin{pmatrix} g'(a) \end{pmatrix}, \\
J_{f}(g(a)) &= \begin{pmatrix} f'(g(a)) \end{pmatrix}.
\end{align}
The Jacobian of is the product of these matrices, so it is , as expected from the one-dimensional chain rule. In the language of linear transformations, is the function which scales a vector by a factor of and is the function which scales a vector by a factor of . The chain rule says that the composite of these two linear transformations is the linear transformation , and therefore it is the function that scales a vector by .
Another way of writing the chain rule is used when f and g are expressed in terms of their components as and . In this case, the above rule for Jacobian matrices is usually written as:
\frac{\partial(y_1, \ldots, y_k)}{\partial(x_1, \ldots, x_n)} = \frac{\partial(y_1, \ldots, y_k)}{\partial(u_1, \ldots, u_m)} \frac{\partial(u_1, \ldots, u_m)}{\partial(x_1, \ldots, x_n)}.
The chain rule for total derivatives implies a chain rule for partial derivatives. Recall that when the total derivative exists, the partial derivative in the -th coordinate direction is found by multiplying the Jacobian matrix by the -th basis vector. By doing this to the formula above, we find:
\frac{\partial(y_1, \ldots, y_k)}{\partial x_i} = \frac{\partial(y_1, \ldots, y_k)}{\partial(u_1, \ldots, u_m)} \frac{\partial(u_1, \ldots, u_m)}{\partial x_i}.
Since the entries of the Jacobian matrix are partial derivatives, we may simplify the above formula to get:
\frac{\partial(y_1, \ldots, y_k)}{\partial x_i} = \sum_{\ell = 1}^m \frac{\partial(y_1, \ldots, y_k)}{\partial u_\ell} \frac{\partial u_\ell}{\partial x_i}.
More conceptually, this rule expresses the fact that a change in the direction may change all of through , and any of these changes may affect .
In the special case where , so that is a real-valued function, then this formula simplifies even further:
\frac{\partial y}{\partial x_i} = \sum_{\ell = 1}^m \frac{\partial y}{\partial u_\ell} \frac{\partial u_\ell}{\partial x_i}.
This can be rewritten as a dot product. Recalling that , the partial derivative is also a vector, and the chain rule says that:
\frac{\partial y}{\partial x_i} = \nabla y \cdot \frac{\partial \mathbf{u}}{\partial x_i}.
==== Example ====
Given where and , determine the value of and using the chain rule.
\frac{\partial u}{\partial r}=\frac{\partial u}{\partial x} \frac{\partial x}{\partial r}+\frac{\partial u}{\partial y} \frac{\partial y}{\partial r} = (2x)(\sin(t)) + (2)(0) = 2r \sin^2(t),
and
\begin{align}
\frac{\partial u}{\partial t}
&= \frac{\partial u}{\partial x} \frac{\partial x}{\partial t}+\frac{\partial u}{\partial y} \frac{\partial y}{\partial t} \\
&= (2x)(r\cos(t)) + (2)(2\sin(t)\cos(t)) \\
&= (2r\sin(t))(r\cos(t)) + 4\sin(t)\cos(t) \\
&= 2(r^2 + 2) \sin(t)\cos(t) \\
&= (r^2 + 2) \sin(2t).
\end{align}
==== Higher derivatives of multivariable functions ====
Faà di Bruno's formula for higher-order derivatives of single-variable functions generalizes to the multivariable case. If is a function of as above, then the second derivative of is:
\frac{\partial^2 y}{\partial x_i \partial x_j} = \sum_k \left(\frac{\partial y}{\partial u_k}\frac{\partial^2 u_k}{\partial x_i \partial x_j}\right) + \sum_{k, \ell} \left(\frac{\partial^2 y}{\partial u_k \partial u_\ell}\frac{\partial u_k}{\partial x_i}\frac{\partial u_\ell}{\partial x_j}\right).
== Further generalizations ==
All extensions of calculus have a chain rule. In most of these, the formula remains the same, though the meaning of that formula may be vastly different.
One generalization is to manifolds. In this situation, the chain rule represents the fact that the derivative of is the composite of the derivative of and the derivative of . This theorem is an immediate consequence of the higher dimensional chain rule given above, and it has exactly the same formula.
The chain rule is also valid for Fréchet derivatives in Banach spaces. The same formula holds as before. This case and the previous one admit a simultaneous generalization to Banach manifolds.
In differential algebra, the derivative is interpreted as a morphism of modules of Kähler differentials. A ring homomorphism of commutative rings determines a morphism of Kähler differentials which sends an element to , the exterior differential of . The formula holds in this context as well.
The common feature of these examples is that they are expressions of the idea that the derivative is part of a functor. A functor is an operation on spaces and functions between them. It associates to each space a new space and to each function between two spaces a new function between the corresponding new spaces. In each of the above cases, the functor sends each space to its tangent bundle and it sends each function to its derivative. For example, in the manifold case, the derivative sends a -manifold to a -manifold (its tangent bundle) and a -function to its total derivative. There is one requirement for this to be a functor, namely that the derivative of a composite must be the composite of the derivatives. This is exactly the formula .
There are also chain rules in stochastic calculus. One of these, Itō's lemma, expresses the composite of an Itō process (or more generally a semimartingale) dXt with a twice-differentiable function f. In Itō's lemma, the derivative of the composite function depends not only on dXt and the derivative of f but also on the second derivative of f. The dependence on the second derivative is a consequence of the non-zero quadratic variation of the stochastic process, which broadly speaking means that the process can move up and down in a very rough way. This variant of the chain rule is not an example of a functor because the two functions being composed are of different types.
|
[
"Gottfried Wilhelm Leibniz",
"integral",
"differential algebra",
"inverse function",
"Lipschitz continuity",
"tangent bundle",
"Constantin Carathéodory",
"division by zero",
"Guillaume de l'Hôpital",
"commutative ring",
"Faà di Bruno's formula",
"stochastic calculus",
"standard part",
"dependent variable",
"Banach space",
"Kähler differential",
"difference quotient",
"quadratic variation",
"formula",
"Hölder condition",
"Leonhard Euler",
"multi-variable function",
"Étienne Bézout",
"Fréchet derivative",
"continuous function",
"dot product",
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"Limit of a function",
"Function composition",
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"polynomial remainder theorem",
"manifold",
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"The American Mathematical Monthly",
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] |
6,115 |
P versus NP problem
|
The P versus NP problem is a major unsolved problem in theoretical computer science. Informally, it asks whether every problem whose solution can be quickly verified can also be quickly solved.
Here, "quickly" means an algorithm exists that solves the task and runs in polynomial time (as opposed to, say, exponential time), meaning the task completion time is bounded above by a polynomial function on the size of the input to the algorithm. The general class of questions that some algorithm can answer in polynomial time is "P" or "class P". For some questions, there is no known way to find an answer quickly, but if provided with an answer, it can be verified quickly. The class of questions where an answer can be verified in polynomial time is "NP", standing for "nondeterministic polynomial time".
An answer to the P versus NP question would determine whether problems that can be verified in polynomial time can also be solved in polynomial time. If P ≠ NP, which is widely believed, it would mean that there are problems in NP that are harder to compute than to verify: they could not be solved in polynomial time, but the answer could be verified in polynomial time.
The problem has been called the most important open problem in computer science. Aside from being an important problem in computational theory, a proof either way would have profound implications for mathematics, cryptography, algorithm research, artificial intelligence, game theory, multimedia processing, philosophy, economics and many other fields.
It is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute, each of which carries a US$1,000,000 prize for the first correct solution.
== Example ==
Consider the following yes/no problem: given an incomplete Sudoku grid of size n^2 \times n^2, is there at least one legal solution where every row, column, and n \times n square contains the integers 1 through n^2? It is straightforward to verify "yes" instances of this generalized Sudoku problem given a candidate solution. However, it is not known whether there is a polynomial-time algorithm that can correctly answer "yes" or "no" to all instances of this problem. Therefore, generalized Sudoku is in NP (quickly verifiable), but may or may not be in P (quickly solvable). (It is necessary to consider a generalized version of Sudoku, as any fixed size Sudoku has only a finite number of possible grids. In this case the problem is in P, as the answer can be found by table lookup.)
==History==
The precise statement of the P versus NP problem was introduced in 1971 by Stephen Cook in his seminal paper "The complexity of theorem proving procedures" (and independently by Leonid Levin in 1973).
Although the P versus NP problem was formally defined in 1971, there were previous inklings of the problems involved, the difficulty of proof, and the potential consequences. In 1955, mathematician John Nash wrote a letter to the NSA, speculating that cracking a sufficiently complex code would require time exponential in the length of the key. If proved (and Nash was suitably skeptical), this would imply what is now called P ≠ NP, since a proposed key can be verified in polynomial time. Another mention of the underlying problem occurred in a 1956 letter written by Kurt Gödel to John von Neumann. Gödel asked whether theorem-proving (now known to be co-NP-complete) could be solved in quadratic or linear time, and pointed out one of the most important consequences—that if so, then the discovery of mathematical proofs could be automated.
==Context==
The relation between the complexity classes P and NP is studied in computational complexity theory, the part of the theory of computation dealing with the resources required during computation to solve a given problem. The most common resources are time (how many steps it takes to solve a problem) and space (how much memory it takes to solve a problem).
In such analysis, a model of the computer for which time must be analyzed is required. Typically such models assume that the computer is deterministic (given the computer's present state and any inputs, there is only one possible action that the computer might take) and sequential (it performs actions one after the other).
In this theory, the class P consists of all decision problems (defined below) solvable on a deterministic sequential machine in a duration polynomial in the size of the input; the class NP consists of all decision problems whose positive solutions are verifiable in polynomial time given the right information, or equivalently, whose solution can be found in polynomial time on a non-deterministic machine. Clearly, P ⊆ NP. Arguably, the biggest open question in theoretical computer science concerns the relationship between those two classes:
Is P equal to NP?
Since 2002, William Gasarch has conducted three polls of researchers concerning this and related questions. Confidence that P ≠ NP has been increasing – in 2019, 88% believed P ≠ NP, as opposed to 83% in 2012 and 61% in 2002. When restricted to experts, the 2019 answers became 99% believed P ≠ NP. It is in NP because (given an input) it is simple to check whether M accepts the input by simulating M; it is NP-complete because the verifier for any particular instance of a problem in NP can be encoded as a polynomial-time machine M that takes the solution to be verified as input. Then the question of whether the instance is a yes or no instance is determined by whether a valid input exists.
The first natural problem proven to be NP-complete was the Boolean satisfiability problem, also known as SAT. As noted above, this is the Cook–Levin theorem; its proof that satisfiability is NP-complete contains technical details about Turing machines as they relate to the definition of NP. However, after this problem was proved to be NP-complete, proof by reduction provided a simpler way to show that many other problems are also NP-complete, including the game Sudoku discussed earlier. In this case, the proof shows that a solution of Sudoku in polynomial time could also be used to complete Latin squares in polynomial time. This in turn gives a solution to the problem of partitioning tri-partite graphs into triangles, which could then be used to find solutions for the special case of SAT known as 3-SAT, which then provides a solution for general Boolean satisfiability. So a polynomial-time solution to Sudoku leads, by a series of mechanical transformations, to a polynomial time solution of satisfiability, which in turn can be used to solve any other NP-problem in polynomial time. Using transformations like this, a vast class of seemingly unrelated problems are all reducible to one another, and are in a sense "the same problem".
==Harder problems==
Although it is unknown whether P = NP, problems outside of P are known. Just as the class P is defined in terms of polynomial running time, the class EXPTIME is the set of all decision problems that have exponential running time. In other words, any problem in EXPTIME is solvable by a deterministic Turing machine in O(2p(n)) time, where p(n) is a polynomial function of n. A decision problem is EXPTIME-complete if it is in EXPTIME, and every problem in EXPTIME has a polynomial-time many-one reduction to it. A number of problems are known to be EXPTIME-complete. Because it can be shown that P ≠ EXPTIME, these problems are outside P, and so require more than polynomial time. In fact, by the time hierarchy theorem, they cannot be solved in significantly less than exponential time. Examples include finding a perfect strategy for chess positions on an N × N board and similar problems for other board games.
The problem of deciding the truth of a statement in Presburger arithmetic requires even more time. Fischer and Rabin proved in 1974 that every algorithm that decides the truth of Presburger statements of length n has a runtime of at least 2^{2^{cn}} for some constant c. Hence, the problem is known to need more than exponential run time. Even more difficult are the undecidable problems, such as the halting problem. They cannot be completely solved by any algorithm, in the sense that for any particular algorithm there is at least one input for which that algorithm will not produce the right answer; it will either produce the wrong answer, finish without giving a conclusive answer, or otherwise run forever without producing any answer at all.
It is also possible to consider questions other than decision problems. One such class, consisting of counting problems, is called #P: whereas an NP problem asks "Are there any solutions?", the corresponding #P problem asks "How many solutions are there?". Clearly, a #P problem must be at least as hard as the corresponding NP problem, since a count of solutions immediately tells if at least one solution exists, if the count is greater than zero. Surprisingly, some #P problems that are believed to be difficult correspond to easy (for example linear-time) P problems. For these problems, it is very easy to tell whether solutions exist, but thought to be very hard to tell how many. Many of these problems are #P-complete, and hence among the hardest problems in #P, since a polynomial time solution to any of them would allow a polynomial time solution to all other #P problems.
==Problems in NP not known to be in P or NP-complete==
In 1975, Richard E. Ladner showed that if P ≠ NP, then there exist problems in NP that are neither in P nor NP-complete. If graph isomorphism is NP-complete, the polynomial time hierarchy collapses to its second level. Since it is widely believed that the polynomial hierarchy does not collapse to any finite level, it is believed that graph isomorphism is not NP-complete. The best algorithm for this problem, due to László Babai, runs in quasi-polynomial time.
The integer factorization problem is the computational problem of determining the prime factorization of a given integer. Phrased as a decision problem, it is the problem of deciding whether the input has a factor less than k. No efficient integer factorization algorithm is known, and this fact forms the basis of several modern cryptographic systems, such as the RSA algorithm. The integer factorization problem is in NP and in co-NP (and even in UP and co-UP). If the problem is NP-complete, the polynomial time hierarchy will collapse to its first level (i.e., NP = co-NP). The most efficient known algorithm for integer factorization is the general number field sieve, which takes expected time
O\left (\exp \left ( \left (\tfrac{64n}{9} \log(2) \right )^{\frac{1}{3}} \left ( \log(n\log(2)) \right )^{\frac{2}{3}} \right) \right )
to factor an n-bit integer. The best known quantum algorithm for this problem, Shor's algorithm, runs in polynomial time, although this does not indicate where the problem lies with respect to non-quantum complexity classes.
==Does P mean "easy"?==
All of the above discussion has assumed that P means "easy" and "not in P" means "difficult", an assumption known as Cobham's thesis. It is a common assumption in complexity theory; but there are caveats.
First, it can be false in practice. A theoretical polynomial algorithm may have extremely large constant factors or exponents, rendering it impractical. For example, the problem of deciding whether a graph G contains H as a minor, where H is fixed, can be solved in a running time of O(n2), where n is the number of vertices in G. However, the big O notation hides a constant that depends superexponentially on H. The constant is greater than 2 \uparrow \uparrow (2 \uparrow \uparrow (2 \uparrow \uparrow (h/2) ) ) (using Knuth's up-arrow notation), and where h is the number of vertices in H.
On the other hand, even if a problem is shown to be NP-complete, and even if P ≠ NP, there may still be effective approaches to the problem in practice. There are algorithms for many NP-complete problems, such as the knapsack problem, the traveling salesman problem, and the Boolean satisfiability problem, that can solve to optimality many real-world instances in reasonable time. The empirical average-case complexity (time vs. problem size) of such algorithms can be surprisingly low. An example is the simplex algorithm in linear programming, which works surprisingly well in practice; despite having exponential worst-case time complexity, it runs on par with the best known polynomial-time algorithms.
Finally, there are types of computations which do not conform to the Turing machine model on which P and NP are defined, such as quantum computation and randomized algorithms.
==Reasons to believe P ≠ NP or P = NP==
Cook provides a restatement of the problem in The P Versus NP Problem as "Does P = NP?" most computer scientists believe that P ≠ NP. A key reason for this belief is that after decades of studying these problems no one has been able to find a polynomial-time algorithm for any of more than 3,000 important known NP-complete problems (see List of NP-complete problems). These algorithms were sought long before the concept of NP-completeness was even defined (Karp's 21 NP-complete problems, among the first found, were all well-known existing problems at the time they were shown to be NP-complete). Furthermore, the result P = NP would imply many other startling results that are currently believed to be false, such as NP = co-NP and P = PH.
It is also intuitively argued that the existence of problems that are hard to solve but whose solutions are easy to verify matches real-world experience.
On the other hand, some researchers believe that it is overconfident to believe P ≠ NP and that researchers should also explore proofs of P = NP. For example, in 2002 these statements were made: that DLIN ≠ NLIN.
==Consequences of solution==
One of the reasons the problem attracts so much attention is the consequences of the possible answers. Either direction of resolution would advance theory enormously, and perhaps have huge practical consequences as well.
===P = NP===
A proof that P = NP could have stunning practical consequences if the proof leads to efficient methods for solving some of the important problems in NP. The potential consequences, both positive and negative, arise since various NP-complete problems are fundamental in many fields.
It is also very possible that a proof would not lead to practical algorithms for NP-complete problems. The formulation of the problem does not require that the bounding polynomial be small or even specifically known. A non-constructive proof might show a solution exists without specifying either an algorithm to obtain it or a specific bound. Even if the proof is constructive, showing an explicit bounding polynomial and algorithmic details, if the polynomial is not very low-order the algorithm might not be sufficiently efficient in practice. In this case the initial proof would be mainly of interest to theoreticians, but the knowledge that polynomial time solutions are possible would surely spur research into better (and possibly practical) methods to achieve them.
A solution showing P = NP could upend the field of cryptography, which relies on certain problems being difficult. A constructive and efficient solution to an NP-complete problem such as 3-SAT would break most existing cryptosystems including:
Existing implementations of public-key cryptography, a foundation for many modern security applications such as secure financial transactions over the Internet.
Symmetric ciphers such as AES or 3DES, used for the encryption of communications data.
Cryptographic hashing, which underlies blockchain cryptocurrencies such as Bitcoin, and is used to authenticate software updates. For these applications, finding a pre-image that hashes to a given value must be difficult, ideally taking exponential time. If P = NP, then this can take polynomial time, through reduction to SAT.
These would need modification or replacement with information-theoretically secure solutions that do not assume P ≠ NP.
There are also enormous benefits that would follow from rendering tractable many currently mathematically intractable problems. For instance, many problems in operations research are NP-complete, such as types of integer programming and the travelling salesman problem. Efficient solutions to these problems would have enormous implications for logistics. Many other important problems, such as some problems in protein structure prediction, are also NP-complete; making these problems efficiently solvable could considerably advance life sciences and biotechnology.
These changes could be insignificant compared to the revolution that efficiently solving NP-complete problems would cause in mathematics itself. Gödel, in his early thoughts on computational complexity, noted that a mechanical method that could solve any problem would revolutionize mathematics:
Similarly, Stephen Cook (assuming not only a proof, but a practically efficient algorithm) says:
Research mathematicians spend their careers trying to prove theorems, and some proofs have taken decades or even centuries to find after problems have been stated—for instance, Fermat's Last Theorem took over three centuries to prove. A method guaranteed to find a proof if a "reasonable" size proof exists, would essentially end this struggle.
Donald Knuth has stated that he has come to believe that P = NP, but is reserved about the impact of a possible proof:
===P ≠ NP===
A proof of P ≠ NP would lack the practical computational benefits of a proof that P = NP, but would represent a great advance in computational complexity theory and guide future research. It would demonstrate that many common problems cannot be solved efficiently, so that the attention of researchers can be focused on partial solutions or solutions to other problems. Due to widespread belief in P ≠ NP, much of this focusing of research has already taken place.
P ≠ NP still leaves open the average-case complexity of hard problems in NP. For example, it is possible that SAT requires exponential time in the worst case, but that almost all randomly selected instances of it are efficiently solvable. Russell Impagliazzo has described five hypothetical "worlds" that could result from different possible resolutions to the average-case complexity question. These range from "Algorithmica", where P = NP and problems like SAT can be solved efficiently in all instances, to "Cryptomania", where P ≠ NP and generating hard instances of problems outside P is easy, with three intermediate possibilities reflecting different possible distributions of difficulty over instances of NP-hard problems. The "world" where P ≠ NP but all problems in NP are tractable in the average case is called "Heuristica" in the paper. A Princeton University workshop in 2009 studied the status of the five worlds.
==Results about difficulty of proof==
Although the P = NP problem itself remains open despite a million-dollar prize and a huge amount of dedicated research, efforts to solve the problem have led to several new techniques. In particular, some of the most fruitful research related to the P = NP problem has been in showing that existing proof techniques are insufficient for answering the question, suggesting novel technical approaches are required.
As additional evidence for the difficulty of the problem, essentially all known proof techniques in computational complexity theory fall into one of the following classifications, all insufficient to prove P ≠ NP:
{| class="wikitable"
|-
!Classification
!Definition
|-
|Relativizing proofs
|Imagine a world where every algorithm is allowed to make queries to some fixed subroutine called an oracle (which can answer a fixed set of questions in constant time, such as an oracle that solves any traveling salesman problem in 1 step), and the running time of the oracle is not counted against the running time of the algorithm. Most proofs (especially classical ones) apply uniformly in a world with oracles regardless of what the oracle does. These proofs are called relativizing. In 1975, Baker, Gill, and Solovay showed that P = NP with respect to some oracles, while P ≠ NP for other oracles. As relativizing proofs can only prove statements that are true for all possible oracles, these techniques cannot resolve P = NP.
|-
|Natural proofs
|In 1993, Alexander Razborov and Steven Rudich defined a general class of proof techniques for circuit complexity lower bounds, called natural proofs. At the time, all previously known circuit lower bounds were natural, and circuit complexity was considered a very promising approach for resolving P = NP. However, Razborov and Rudich showed that if one-way functions exist, P and NP are indistinguishable to natural proof methods. Although the existence of one-way functions is unproven, most mathematicians believe that they do, and a proof of their existence would be a much stronger statement than P ≠ NP. Thus it is unlikely that natural proofs alone can resolve P = NP.
|-
|Algebrizing proofs
|After the Baker–Gill–Solovay result, new non-relativizing proof techniques were successfully used to prove that IP = PSPACE. However, in 2008, Scott Aaronson and Avi Wigderson showed that the main technical tool used in the IP = PSPACE proof, known as arithmetization, was also insufficient to resolve P = NP. Arithmetization converts the operations of an algorithm to algebraic and basic arithmetic symbols and then uses those to analyze the workings. In the IP = PSPACE proof, they convert the black box and the Boolean circuits to an algebraic problem. However, if the problem is undecidable even with much weaker assumptions extending the Peano axioms for integer arithmetic, then nearly polynomial-time algorithms exist for all NP problems. Therefore, assuming (as most complexity theorists do) some NP problems don't have efficient algorithms, proofs of independence with those techniques are impossible. This also implies proving independence from PA or ZFC with current techniques is no easier than proving all NP problems have efficient algorithms.
==Logical characterizations==
The P = NP problem can be restated as certain classes of logical statements, as a result of work in descriptive complexity.
Consider all languages of finite structures with a fixed signature including a linear order relation. Then, all such languages in P are expressible in first-order logic with the addition of a suitable least fixed-point combinator. Recursive functions can be defined with this and the order relation. As long as the signature contains at least one predicate or function in addition to the distinguished order relation, so that the amount of space taken to store such finite structures is actually polynomial in the number of elements in the structure, this precisely characterizes P.
Similarly, NP is the set of languages expressible in existential second-order logic—that is, second-order logic restricted to exclude universal quantification over relations, functions, and subsets. The languages in the polynomial hierarchy, PH, correspond to all of second-order logic. Thus, the question "is P a proper subset of NP" can be reformulated as "is existential second-order logic able to describe languages (of finite linearly ordered structures with nontrivial signature) that first-order logic with least fixed point cannot?". The word "existential" can even be dropped from the previous characterization, since P = NP if and only if P = PH (as the former would establish that NP = co-NP, which in turn implies that NP = PH).
==Polynomial-time algorithms==
No known algorithm for a NP-complete problem runs in polynomial time. However, there are algorithms known for NP-complete problems that if P = NP, the algorithm runs in polynomial time on accepting instances (although with enormous constants, making the algorithm impractical). However, these algorithms do not qualify as polynomial time because their running time on rejecting instances are not polynomial. The following algorithm, due to Levin (without any citation), is such an example below. It correctly accepts the NP-complete language SUBSET-SUM. It runs in polynomial time on inputs that are in SUBSET-SUM if and only if P = NP:
// Algorithm that accepts the NP-complete language SUBSET-SUM.
//
// this is a polynomial-time algorithm if and only if P = NP.
//
// "Polynomial-time" means it returns "yes" in polynomial time when
// the answer should be "yes", and runs forever when it is "no".
//
// Input: S = a finite set of integers
// Output: "yes" if any subset of S adds up to 0.
// Runs forever with no output otherwise.
// Note: "Program number M" is the program obtained by
// writing the integer M in binary, then
// considering that string of bits to be a
// program. Every possible program can be
// generated this way, though most do nothing
// because of syntax errors.
FOR K = 1...∞
FOR M = 1...K
Run program number M for K steps with input S
IF the program outputs a list of distinct integers
AND the integers are all in S
AND the integers sum to 0
THEN
OUTPUT "yes" and HALT
This is a polynomial-time algorithm accepting an NP-complete language only if P = NP. "Accepting" means it gives "yes" answers in polynomial time, but is allowed to run forever when the answer is "no" (also known as a semi-algorithm).
This algorithm is enormously impractical, even if P = NP. If the shortest program that can solve SUBSET-SUM in polynomial time is b bits long, the above algorithm will try at least other programs first.
==Formal definitions==
===P and NP===
A decision problem is a problem that takes as input some string w over an alphabet Σ, and outputs "yes" or "no". If there is an algorithm (say a Turing machine, or a computer program with unbounded memory) that produces the correct answer for any input string of length n in at most cnk steps, where k and c are constants independent of the input string, then we say that the problem can be solved in polynomial time and we place it in the class P. Formally, P is the set of languages that can be decided by a deterministic polynomial-time Turing machine. Meaning,
\mathbf{P} = \{ L : L=L(M) \text{ for some deterministic polynomial-time Turing machine } M \}
where
L(M) = \{ w\in\Sigma^{*}: M \text{ accepts } w \}
and a deterministic polynomial-time Turing machine is a deterministic Turing machine M that satisfies two conditions:
M halts on all inputs w and
there exists k \in N such that T_M(n)\in O(n^k), where O refers to the big O notation and
T_M(n) = \max\{ t_M(w) : w\in\Sigma^{*}, |w| = n \}
t_M(w) = \text{ number of steps }M\text{ takes to halt on input }w.
NP can be defined similarly using nondeterministic Turing machines (the traditional way). However, a modern approach uses the concept of certificate and verifier. Formally, NP is the set of languages with a finite alphabet and verifier that runs in polynomial time. The following defines a "verifier":
Let L be a language over a finite alphabet, Σ.
L ∈ NP if, and only if, there exists a binary relation R\subset\Sigma^{*}\times\Sigma^{*} and a positive integer k such that the following two conditions are satisfied:
For all x\in\Sigma^{*}, x\in L \Leftrightarrow\exists y\in\Sigma^{*} such that (x, y) ∈ R and |y|\in O(|x|^k); and
the language L_{R} = \{ x\# y:(x,y)\in R\} over \Sigma\cup\{\#\} is decidable by a deterministic Turing machine in polynomial time.
A Turing machine that decides LR is called a verifier for L and a y such that (x, y) ∈ R is called a certificate of membership of x in L.
Not all verifiers must be polynomial-time. However, for L to be in NP, there must be a verifier that runs in polynomial time.
====Example====
Let
\mathrm{COMPOSITE} = \left \{x\in\mathbb{N} \mid x=pq \text{ for integers } p, q > 1 \right \}
R = \left \{(x,y)\in\mathbb{N} \times\mathbb{N} \mid 1
Whether a value of x is composite is equivalent to of whether x is a member of COMPOSITE. It can be shown that COMPOSITE ∈ NP by verifying that it satisfies the above definition (if we identify natural numbers with their binary representations).
COMPOSITE also happens to be in P, a fact demonstrated by the invention of the AKS primality test.
===NP-completeness===
There are many equivalent ways of describing NP-completeness.
Let L be a language over a finite alphabet Σ.
L is NP-complete if, and only if, the following two conditions are satisfied:
L ∈ NP; and
any L' in NP is polynomial-time-reducible to L (written as L' \leq_{p} L), where L' \leq_{p} L if, and only if, the following two conditions are satisfied:
There exists f : Σ* → Σ* such that for all w in Σ* we have: (w\in L' \Leftrightarrow f(w)\in L); and
there exists a polynomial-time Turing machine that halts with f(w) on its tape on any input w.
Alternatively, if L ∈ NP, and there is another NP-complete problem that can be polynomial-time reduced to L, then L is NP-complete. This is a common way of proving some new problem is NP-complete.
==Claimed solutions ==
While the P versus NP problem is generally considered unsolved, many amateur and some professional researchers have claimed solutions. Gerhard J. Woeginger compiled a list of 116 purported proofs from 1986 to 2016, of which 61 were proofs of P = NP, 49 were proofs of P ≠ NP, and 6 proved other results, e.g. that the problem is undecidable. Some attempts at resolving P versus NP have received brief media attention, though these attempts have been refuted.
==Popular culture==
The film Travelling Salesman, by director Timothy Lanzone, is the story of four mathematicians hired by the US government to solve the P versus NP problem.
In the sixth episode of The Simpsons seventh season "Treehouse of Horror VI", the equation P = NP is seen shortly after Homer accidentally stumbles into the "third dimension".
In the second episode of season 2 of Elementary, "Solve for X" Sherlock and Watson investigate the murders of mathematicians who were attempting to solve P versus NP.
==Similar problems==
R vs. RE problem, where R is analog of class P, and RE is analog class NP. These classes are not equal, because undecidable but verifiable problems do exist, for example, Hilbert's tenth problem which is RE-complete.
A similar problem exists in the theory of algebraic complexity: VP vs. VNP problem. Like P vs. NP, the answer is currently unknown.
|
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"Journal of the ACM",
"Donald Knuth",
"knapsack problem",
"The Simpsons",
"Michael O. Rabin",
"game theory",
"quantum computation",
"Scott Aaronson",
"big O notation",
"Travelling Salesman (2012 film)",
"Independence (mathematical logic)",
"David Eppstein",
"black box",
"Graph (discrete mathematics)",
"one-way functions",
"Avi Wigderson",
"AKS primality test",
"exponential time",
"John von Neumann",
"NP-hard",
"linear order",
"economics",
"Game complexity",
"Cryptographic hash function",
"Certificate (complexity)",
"time hierarchy theorem",
"Composite number",
"linear programming",
"co-NP",
"information-theoretic security",
"polynomial time",
"SIGACT News",
"Sharp-P",
"Sharp-P-complete",
"Michael J. Fischer",
"quasi-polynomial time",
"Kurt Gödel",
"RSA (algorithm)",
"cryptography",
"Steven Rudich",
"Karp's 21 NP-complete problems",
"multipartite graph"
] |
6,117 |
Charles Sanders Peirce
|
{{infobox philosopher
| name = Charles Sanders Peirce
| image = Charles Sanders Peirce.jpg
| caption=Peirce in 1891
| birth_date =
| birth_place = Cambridge, Massachusetts, U.S.
| death_date =
| death_place = Milford, Pennsylvania, U.S.
| relatives = Benjamin Peirce (father)
| institutions = Johns Hopkins University
| alma_mater = Harvard University
| known_for =
| region = Western philosophy
| era = Late modern philosophy
| school_tradition =
| main_interests =
| notable_students = {{collapsible list|
{{hlist | John Dewey | Fabian Franklin ; September 10, 1839 – April 19, 1914) was an American scientist, mathematician, logician, and philosopher who is sometimes known as "the father of pragmatism". According to philosopher Paul Weiss, Peirce was "the most original and versatile of America's philosophers and America's greatest logician". Bertrand Russell wrote "he was one of the most original minds of the later nineteenth century and certainly the greatest American thinker ever".
In metaphysics, Peirce was an "objective idealist" in the tradition of German philosopher Immanuel Kant as well as a scholastic realist about universals. He also held a commitment to the ideas of continuity and chance as real features of the universe, views he labeled synechism and tychism respectively. Peirce believed an epistemic fallibilism and anti-skepticism went along with these views.
==Biography==
=== Early life ===
Peirce was born at 3 Phillips Place in Cambridge, Massachusetts. He was the son of Sarah Hunt Mills and Benjamin Peirce, himself a professor of mathematics and astronomy at Harvard University. At age 12, Charles read his older brother's copy of Richard Whately's Elements of Logic, then the leading English-language text on the subject. So began his lifelong fascination with logic and reasoning.
He suffered from his late teens onward from a nervous condition then known as "facial neuralgia", which would today be diagnosed as trigeminal neuralgia. His biographer, Joseph Brent, says that when in the throes of its pain "he was, at first, almost stupefied, and then aloof, cold, depressed, extremely suspicious, impatient of the slightest crossing, and subject to violent outbursts of temper". Its consequences may have led to the social isolation of his later life.
=== Education ===
Peirce went on to earn a Bachelor of Arts degree and a Master of Arts degree (1862) from Harvard. In 1863 the Lawrence Scientific School awarded him a Bachelor of Science degree, Harvard's first summa cum laude chemistry degree. His academic record was otherwise undistinguished. At Harvard, he began lifelong friendships with Francis Ellingwood Abbot, Chauncey Wright, and William James. One of his Harvard instructors, Charles William Eliot, formed an unfavorable opinion of Peirce. This proved fateful, because Eliot, while President of Harvard (1869–1909—a period encompassing nearly all of Peirce's working life), repeatedly vetoed Peirce's employment at the university.
=== United States Coast Survey ===
Between 1859 and 1891, Peirce was intermittently employed in various scientific capacities by the United States Coast Survey, which in 1878 was renamed the United States Coast and Geodetic Survey, where he enjoyed his highly influential father's protection until the latter's death in 1880. At the Survey, he worked mainly in geodesy and gravimetry, refining the use of pendulums to determine small local variations in the Earth's gravity. No members of the Peirce family volunteered or enlisted. Peirce grew up in a home where white supremacy was taken for granted, and slavery was considered natural. Peirce's father had described himself as a secessionist until the outbreak of the war, after which he became a Union partisan, providing donations to the Sanitary Commission, the leading Northern war charity.
Peirce liked to use the following syllogism to illustrate the unreliability of traditional forms of logic (for the first premise arguably assumes the conclusion):
All Men are equal in their political rights.
Negroes are Men.
Therefore, negroes are equal in political rights to whites.
==== Travels to Europe ====
He was elected a resident fellow of the American Academy of Arts and Sciences in January 1867. The Survey sent him to Europe five times, first in 1871 as part of a group sent to observe a solar eclipse. There, he sought out Augustus De Morgan, William Stanley Jevons, and William Kingdon Clifford, British mathematicians and logicians whose turn of mind resembled his own.
==== Harvard observatory ====
From 1869 to 1872, he was employed as an assistant in Harvard's astronomical observatory, doing important work on determining the brightness of stars and the shape of the Milky Way. In 1872 he founded the Metaphysical Club, a conversational philosophical club that Peirce, the future Supreme Court Justice Oliver Wendell Holmes Jr., the philosopher and psychologist William James, amongst others, formed in January 1872 in Cambridge, Massachusetts, and dissolved in December 1872. Other members of the club included Chauncey Wright, John Fiske, Francis Ellingwood Abbot, Nicholas St. John Green, and Joseph Bangs Warner. The discussions eventually birthed Peirce's notion of pragmatism.
==== National Academy of Sciences ====
On April 20, 1877, he was elected a member of the National Academy of Sciences. Also in 1877, he proposed measuring the meter as so many wavelengths of light of a certain frequency, the kind of definition employed from 1960 to 1983.
In 1879 Peirce developed Peirce quincuncial projection, having been inspired by H. A. Schwarz's 1869 conformal transformation of a circle onto a polygon of n sides (known as the Schwarz–Christoffel mapping).
==== 1880 to 1891 ====
During the 1880s, Peirce's indifference to bureaucratic detail waxed while his Survey work's quality and timeliness waned. Peirce took years to write reports that he should have completed in months. Meanwhile, he wrote entries, ultimately thousands, during 1883–1909 on philosophy, logic, science, and other subjects for the encyclopedic Century Dictionary. In 1885, an investigation by the Allison Commission exonerated Peirce, but led to the dismissal of Superintendent Julius Hilgard and several other Coast Survey employees for misuse of public funds. In 1891, Peirce resigned from the Coast Survey at Superintendent Thomas Corwin Mendenhall's request.
=== Johns Hopkins University ===
In 1879, Peirce was appointed lecturer in logic at Johns Hopkins University, which had strong departments in areas that interested him, such as philosophy (Royce and Dewey completed their PhDs at Hopkins), psychology (taught by G. Stanley Hall and studied by Joseph Jastrow, who coauthored a landmark empirical study with Peirce), and mathematics (taught by J. J. Sylvester, who came to admire Peirce's work on mathematics and logic). His Studies in Logic by Members of the Johns Hopkins University (1883) contained works by himself and Allan Marquand, Christine Ladd, Benjamin Ives Gilman, and Oscar Howard Mitchell, several of whom were his graduate students. Peirce's nontenured position at Hopkins was the only academic appointment he ever held.
Brent documents something Peirce never suspected, namely that his efforts to obtain academic employment, grants, and scientific respectability were repeatedly frustrated by the covert opposition of a major Canadian-American scientist of the day, Simon Newcomb. Newcomb had been a favourite student of Peirce's father; although "no doubt quite bright", "like Salieri in Peter Shaffer's Amadeus he also had just enough talent to recognize he was not a genius and just enough pettiness to resent someone who was". Additionally "an intensely devout and literal-minded Christian of rigid moral standards", he was appalled by what he considered Peirce's personal shortcomings. Peirce's efforts may also have been hampered by what Brent characterizes as "his difficult personality". In contrast, Keith Devlin believes that Peirce's work was too far ahead of his time to be appreciated by the academic establishment of the day and that this played a large role in his inability to obtain a tenured position.
=== Personal life ===
Peirce's personal life undoubtedly worked against his professional success. After his first wife, Harriet Melusina Fay ("Zina"), left him in 1875, Peirce, while still legally married, became involved with Juliette, whose last name, given variously as Froissy and Pourtalai, and nationality (she spoke French) remain uncertain. When his divorce from Zina became final in 1883, he married Juliette. That year, Newcomb pointed out to a Johns Hopkins trustee that Peirce, while a Hopkins employee, had lived and traveled with a woman to whom he was not married; the ensuing scandal led to his dismissal in January 1884. Over the years Peirce sought academic employment at various universities without success. He had no children by either marriage.
=== Later life and poverty ===
In 1887, Peirce spent part of his inheritance from his parents to buy of rural land near Milford, Pennsylvania, which never yielded an economic return. There he had an 1854 farmhouse remodeled to his design. The Peirces named the property "Arisbe". There they lived with few interruptions for the rest of their lives, Charles writing prolifically, with much of his work remaining unpublished to this day (see Works). Living beyond their means soon led to grave financial and legal difficulties. Charles spent much of his last two decades unable to afford heat in winter and subsisting on old bread donated by the local baker. Unable to afford new stationery, he wrote on the verso side of old manuscripts. An outstanding warrant for assault and unpaid debts led to his being a fugitive in New York City for a while. Several people, including his brother James Mills Peirce and his neighbors, relatives of Gifford Pinchot, settled his debts and paid his property taxes and mortgage.
Peirce did some scientific and engineering consulting and wrote much for meager pay, mainly encyclopedic dictionary entries, and reviews for The Nation (with whose editor, Wendell Phillips Garrison, he became friendly). He did translations for the Smithsonian Institution, at its director Samuel Langley's instigation. Peirce also did substantial mathematical calculations for Langley's research on powered flight. Hoping to make money, Peirce tried inventing. He began but did not complete several books. In 1888, President Grover Cleveland appointed him to the Assay Commission.
From 1890 on, he had a friend and admirer in Judge Francis C. Russell of Chicago, who introduced Peirce to editor Paul Carus and owner Edward C. Hegeler of the pioneering American philosophy journal The Monist, which eventually published at least 14 articles by Peirce. He wrote many texts in James Mark Baldwin's Dictionary of Philosophy and Psychology (1901–1905); half of those credited to him appear to have been written actually by Christine Ladd-Franklin under his supervision. He applied in 1902 to the newly formed Carnegie Institution for a grant to write a systematic book describing his life's work. The application was doomed; his nemesis, Newcomb, served on the Carnegie Institution executive committee, and its president had been president of Johns Hopkins at the time of Peirce's dismissal.
The one who did the most to help Peirce in these desperate times was his old friend William James, dedicating his Will to Believe (1897) to Peirce, and arranging for Peirce to be paid to give two series of lectures at or near Harvard (1898 and 1903). Most important, each year from 1907 until James's death in 1910, James wrote to his friends in the Boston intelligentsia to request financial aid for Peirce; the fund continued even after James died. Peirce reciprocated by designating James's eldest son as his heir should Juliette predecease him. It has been believed that this was also why Peirce used "Santiago" ("St. James" in English) as a middle name, but he appeared in print as early as 1890 as Charles Santiago Peirce. (See Charles Santiago Sanders Peirce for discussion and references).
==Death and legacy==
Peirce died destitute in Milford, Pennsylvania, twenty years before his widow. Juliette Peirce kept the urn with Peirce's ashes at Arisbe. In 1934, Pennsylvania Governor Gifford Pinchot arranged for Juliette's burial in Milford Cemetery. The urn with Peirce's ashes was interred with Juliette.
Bertrand Russell (1959) wrote "Beyond doubt [...] he was one of the most original minds of the later nineteenth century and certainly the greatest American thinker ever". Russell and Whitehead's Principia Mathematica, published from 1910 to 1913, does not mention Peirce (Peirce's work was not widely known until later). A. N. Whitehead, while reading some of Peirce's unpublished manuscripts soon after arriving at Harvard in 1924, was struck by how Peirce had anticipated his own "process" thinking. (On Peirce and process metaphysics, see Lowe 1964. Yet Peirce's achievements were not immediately recognized. His imposing contemporaries William James and Josiah Royce admired him and Cassius Jackson Keyser, at Columbia and C. K. Ogden, wrote about Peirce with respect but to no immediate effect.
The first scholar to give Peirce his considered professional attention was Royce's student Morris Raphael Cohen, the editor of an anthology of Peirce's writings entitled Chance, Love, and Logic (1923), and the author of the first bibliography of Peirce's scattered writings. John Dewey studied under Peirce at Johns Hopkins. The publication of the first six volumes of Collected Papers (1931–1935) was the most important event to date in Peirce studies and one that Cohen made possible by raising the needed funds; however it did not prompt an outpouring of secondary studies. The editors of those volumes, Charles Hartshorne and Paul Weiss, did not become Peirce specialists. Early landmarks of the secondary literature include the monographs by Buchler (1939), Feibleman (1946), and Goudge (1950), the 1941 PhD thesis by Arthur W. Burks (who went on to edit volumes 7 and 8), and the studies edited by Wiener and Young (1952). The Charles S. Peirce Society was founded in 1946. Its Transactions, an academic quarterly specializing in Peirce's pragmatism and American philosophy has appeared since 1965. (See Phillips 2014, 62 for discussion of Peirce and Dewey relative to transactionalism.)
By 1943 such was Peirce's reputation, in the US at least, that Webster's Biographical Dictionary said that Peirce was "now regarded as the most original thinker and greatest logician of his time".
In 1949, while doing unrelated archival work, the historian of mathematics Carolyn Eisele (1902–2000) chanced on an autograph letter by Peirce. So began her forty years of research on Peirce, “the mathematician and scientist,” culminating in Eisele (1976, 1979, 1985). In 1952, the Scottish philosopher W. B. Gallie had his book Peirce and Pragmatism published, which introduced the work of Peirce to an international readership. A.J. Ayer, the English philosopher, provided the Editorial Foreword to Gallie's book. In it he credited Peirce's philosophy as being 'not only of great historical significance, as one of the original sources of American pragmatism, but also extremely important in itself.' Ayer concluded: 'it is clear from Professor Gallie’s exposition of his doctrines that he is a philosopher from whom we still have much to learn.'
Beginning around 1960, Max Fisch (1900-1995), the philosopher and historian of ideas, emerged as an authority on Peirce (Fisch, 1986). He included many of his relevant articles in a survey (Fisch 1986: 422–448) of the impact of Peirce's thought through 1983.
Peirce has gained an international following, marked by university research centers devoted to Peirce studies and pragmatism in Brazil (CeneP/CIEP and Centro de Estudos de Pragmatismo), Finland (HPRC and #CDPT|), Germany (Wirth's group, Hoffman's and Otte's group, and Deuser's and Härle's group), France (L'I.R.S.C.E.), Spain (GEP), and Italy (CSP). His writings have been translated into several languages, including German, French, Finnish, Spanish, and Swedish. Since 1950, there have been French, Italian, Spanish, British, and Brazilian Peirce scholars of note. For many years, the North American philosophy department most devoted to Peirce was the University of Toronto, thanks in part to the leadership of Thomas Goudge and David Savan. In recent years, U.S. Peirce scholars have clustered at Indiana University – Purdue University Indianapolis, home of the Peirce Edition Project (PEP) –, and Pennsylvania State University.
{{Blockquote|Currently, considerable interest is being taken in Peirce's ideas by researchers wholly outside the arena of academic philosophy. The interest comes from industry, business, technology, intelligence organizations, and the military; and it has resulted in the existence of a substantial number of agencies, institutes, businesses, and laboratories in which ongoing research into and development of Peircean concepts are being vigorously undertaken.|Robert Burch, 2001, updated 2010
==Works==
Peirce's reputation rests largely on academic papers published in American scientific and scholarly journals such as Proceedings of the American Academy of Arts and Sciences, the Journal of Speculative Philosophy, The Monist, Popular Science Monthly, the American Journal of Mathematics, Memoirs of the National Academy of Sciences, The Nation, and others. See Articles by Peirce, published in his lifetime for an extensive list with links to them online. The only full-length book (neither extract nor pamphlet) that Peirce authored and saw published in his lifetime was Photometric Researches (1878), a 181-page monograph on the applications of spectrographic methods to astronomy. While at Johns Hopkins, he edited Studies in Logic (1883), containing chapters by himself and his graduate students. Besides lectures during his years (1879–1884) as lecturer in Logic at Johns Hopkins, he gave at least nine series of lectures, many now published; see Lectures by Peirce.
After Peirce's death, Harvard University obtained from Peirce's widow the papers found in his study, but did not microfilm them until 1964. Only after Richard Robin (1967) catalogued this Nachlass did it become clear that Peirce had left approximately 1,650 unpublished manuscripts, totaling over 100,000 pages, mostly still unpublished except on microfilm. On the vicissitudes of Peirce's papers, see Houser (1989). Reportedly the papers remain in unsatisfactory condition.
The first published anthology of Peirce's articles was the one-volume Chance, Love and Logic: Philosophical Essays, edited by Morris Raphael Cohen, 1923, still in print. Other one-volume anthologies were published in 1940, 1957, 1958, 1972, 1994, and 2009, most still in print. The main posthumous editions of Peirce's works in their long trek to light, often multi-volume, and some still in print, have included:
1931–1958: Collected Papers of Charles Sanders Peirce (CP), 8 volumes, includes many published works, along with a selection of previously unpublished work and a smattering of his correspondence. This long-time standard edition drawn from Peirce's work from the 1860s to 1913 remains the most comprehensive survey of his prolific output from 1893 to 1913. It is organized thematically, but texts (including lecture series) are often split up across volumes, while texts from various stages in Peirce's development are often combined, requiring frequent visits to editors' notes. Edited (1–6) by Charles Hartshorne and Paul Weiss and (7–8) by Arthur Burks, in print and online.
1975–1987: Charles Sanders Peirce: Contributions to The Nation, 4 volumes, includes Peirce's more than 300 reviews and articles published 1869–1908 in The Nation. Edited by Kenneth Laine Ketner and James Edward Cook, online.
1976: The New Elements of Mathematics by Charles S. Peirce, 4 volumes in 5, included many previously unpublished Peirce manuscripts on mathematical subjects, along with Peirce's important published mathematical articles. Edited by Carolyn Eisele, back in print.
1977: Semiotic and Significs: The Correspondence between C. S. Peirce and Victoria Lady Welby (2nd edition 2001), included Peirce's entire correspondence (1903–1912) with Victoria, Lady Welby. Peirce's other published correspondence is largely limited to the 14 letters included in volume 8 of the Collected Papers, and the 20-odd pre-1890 items included so far in the Writings. Edited by Charles S. Hardwick with James Cook, out of print.
1982–now: Writings of Charles S. Peirce, A Chronological Edition (W), Volumes 1–6 & 8, of a projected 30. The limited coverage, and defective editing and organization, of the Collected Papers led Max Fisch and others in the 1970s to found the Peirce Edition Project (PEP), whose mission is to prepare a more complete critical chronological edition. Only seven volumes have appeared to date, but they cover the period from 1859 to 1892, when Peirce carried out much of his best-known work. Writings of Charles S. Peirce, 8 was published in November 2010; and work continues on Writings of Charles S. Peirce, 7, 9, and 11. In print and online.
1985: Historical Perspectives on Peirce's Logic of Science: A History of Science, 2 volumes. Auspitz has said, "The extent of Peirce's immersion in the science of his day is evident in his reviews in the Nation [...] and in his papers, grant applications, and publishers' prospectuses in the history and practice of science", referring latterly to Historical Perspectives. Edited by Carolyn Eisele, back in print.
1992: Reasoning and the Logic of Things collects in one place Peirce's 1898 series of lectures invited by William James. Edited by Kenneth Laine Ketner, with commentary by Hilary Putnam, in print.
1992–1998: The Essential Peirce (EP), 2 volumes, is an important recent sampler of Peirce's philosophical writings. Edited (1) by Nathan Hauser and Christian Kloesel and (2) by Peirce Edition Project editors, in print.
1997: Pragmatism as a Principle and Method of Right Thinking collects Peirce's 1903 Harvard "Lectures on Pragmatism" in a study edition, including drafts, of Peirce's lecture manuscripts, which had been previously published in abridged form; the lectures now also appear in The Essential Peirce, 2. Edited by Patricia Ann Turisi, in print.
2010: Philosophy of Mathematics: Selected Writings collects important writings by Peirce on the subject, many not previously in print. Edited by Matthew E. Moore, in print.
==Mathematics==
Peirce's most important work in pure mathematics was in logical and foundational areas. He also worked on linear algebra, matrices, various geometries, topology and Listing numbers, Bell numbers, graphs, the four-color problem, and the nature of continuity.
He worked on applied mathematics in economics, engineering, and map projections, and was especially active in probability and statistics.
Discoveries
↓ The Peirce arrow, symbol for "(neither) ... nor ...", also called the Quine dagger
Peirce made a number of striking discoveries in formal logic and foundational mathematics, nearly all of which came to be appreciated only long after he died:
In 1860, he suggested a cardinal arithmetic for infinite numbers, years before any work by Georg Cantor (who completed his dissertation in 1867) and without access to Bernard Bolzano's 1851 (posthumous) Paradoxien des Unendlichen.
In 1880–1881, he showed how Boolean algebra could be done via a repeated sufficient single binary operation (logical NOR), anticipating Henry M. Sheffer by 33 years. (See also De Morgan's Laws.)
In 1881, he set out the axiomatization of natural number arithmetic, a few years before Richard Dedekind and Giuseppe Peano. In the same paper Peirce gave, years before Dedekind, the first purely cardinal definition of a finite set in the sense now known as "Dedekind-finite", and implied by the same stroke an important formal definition of an infinite set (Dedekind-infinite), as a set that can be put into a one-to-one correspondence with one of its proper subsets.
In 1885, he distinguished between first-order and second-order quantification. In the same paper he set out what can be read as the first (primitive) axiomatic set theory, anticipating Zermelo by about two decades (Brady 2000, pp. 132–133).
In 1886, he saw that Boolean calculations could be carried out via electrical switches, he was devising existential graphs, a diagrammatic notation for the predicate calculus. Based on them are John F. Sowa's conceptual graphs and Sun-Joo Shin's diagrammatic reasoning.
The New Elements of Mathematics
Peirce wrote drafts for an introductory textbook, with the working title The New Elements of Mathematics, that presented mathematics from an original standpoint. Those drafts and many other of his previously unpublished mathematical manuscripts finally appeared
===Mathematics of logic===
Mathematical logic and foundations, some noted articles
"On an Improvement in Boole's Calculus of Logic" (1867)
"Description of a Notation for the Logic of Relatives" (1870)
"On the Algebra of Logic" (1880)
"A Boolian Algebra with One Constant" (1880 MS)
"On the Logic of Number" (1881)
"Note B: The Logic of Relatives" (1883)
"On the Algebra of Logic: A Contribution to the Philosophy of Notation" (1884/1885)
"The Logic of Relatives" (1897)
"The Simplest Mathematics" (1902 MS)
"Prolegomena to an Apology for Pragmaticism" (1906, on existential graphs)
===Probability and statistics===
Peirce held that science achieves statistical probabilities, not certainties, and that spontaneity ("absolute chance") is real (see Tychism on his view). Most of his statistical writings promote the frequency interpretation of probability (objective ratios of cases), and many of his writings express skepticism about (and criticize the use of) probability when such models are not based on objective randomization. Though Peirce was largely a frequentist, his possible world semantics introduced the "propensity" theory of probability before Karl Popper. Peirce (sometimes with Joseph Jastrow) investigated the probability judgments of experimental subjects, "perhaps the very first" elicitation and estimation of subjective probabilities in experimental psychology and (what came to be called) Bayesian statistics. (Hacking 1990:205) and pragmatism commits one to anti-nominalist belief in the reality of the general (CP 5.453–457).
For Peirce, First Philosophy, which he also called cenoscopy, is less basic than mathematics and more basic than the special sciences (of nature and mind). It studies positive phenomena in general, phenomena available to any person at any waking moment, and does not settle questions by resorting to special experiences. He divided such philosophy into (1) phenomenology (which he also called phaneroscopy or categorics), (2) normative sciences (esthetics, ethics, and logic), and (3) metaphysics; his views on them are discussed in order below.
Peirce did not write extensively in aesthetics and ethics, but came by 1902 to hold that aesthetics, ethics, and logic, in that order, comprise the normative sciences. He characterized aesthetics as the study of the good (grasped as the admirable), and thus of the ends governing all conduct and thought.
===Influence and legacy===
Umberto Eco described Peirce as "undoubtedly the greatest unpublished writer of our generation" and by Karl Popper as "one of the greatest philosophers of all time". The Internet Encyclopedia of Philosophy says of Peirce that although "long considered an eccentric figure whose contribution to pragmatism was to provide its name and whose importance was as an influence upon James and Dewey, Peirce's significance in his own right is now largely accepted."
==Pragmatism==
Some noted articles and lectures
Illustrations of the Logic of Science (1877–1878): inquiry, pragmatism, statistics, inference
The Fixation of Belief (1877)
How to Make Our Ideas Clear (1878)
The Doctrine of Chances (1878)
The Probability of Induction (1878)
The Order of Nature (1878)
Deduction, Induction, and Hypothesis (1878)
The Harvard lectures on pragmatism (1903)
What Pragmatism Is (1905)
Issues of Pragmaticism (1905)
Pragmatism (1907 MS in The Essential Peirce, 2) Peirce's recipe for pragmatic thinking, which he called pragmatism and, later, pragmaticism, is recapitulated in several versions of the so-called pragmatic maxim. Here is one of his more emphatic reiterations of it:
As a movement, pragmatism began in the early 1870s in discussions among Peirce, William James, and others in the Metaphysical Club. James among others regarded some articles by Peirce such as "The Fixation of Belief" (1877) and especially "How to Make Our Ideas Clear" (1878) as foundational to pragmatism. Peirce (CP 5.11–12), like James (Pragmatism: A New Name for Some Old Ways of Thinking, 1907), saw pragmatism as embodying familiar attitudes, in philosophy and elsewhere, elaborated into a new deliberate method for fruitful thinking about problems. Peirce differed from James and the early John Dewey, in some of their tangential enthusiasms, in being decidedly more rationalistic and realistic, in several senses of those terms, throughout the preponderance of his own philosophical moods.
In 1905 Peirce coined the new name pragmaticism "for the precise purpose of expressing the original definition", saying that "all went happily" with James's and F.C.S. Schiller's variant uses of the old name "pragmatism" and that he coined the new name because of the old name's growing use in "literary journals, where it gets abused". Yet he cited as causes, in a 1906 manuscript, his differences with James and Schiller and, in a 1908 publication, his differences with James as well as literary author Giovanni Papini's declaration of pragmatism's indefinability. Peirce in any case regarded his views that truth is immutable and infinity is real, as being opposed by the other pragmatists, but he remained allied with them on other issues.
Pragmatism begins with the idea that belief is that on which one is prepared to act. Peirce's pragmatism is a method of clarification of conceptions of objects. It equates any conception of an object to a conception of that object's effects to a general extent of the effects' conceivable implications for informed practice. It is a method of sorting out conceptual confusions occasioned, for example, by distinctions that make (sometimes needed) formal yet not practical differences. He formulated both pragmatism and statistical principles as aspects of scientific logic, in his "Illustrations of the Logic of Science" series of articles. In the second one, "How to Make Our Ideas Clear", Peirce discussed three grades of clearness of conception:
Clearness of a conception familiar and readily used, even if unanalyzed and undeveloped.
Clearness of a conception in virtue of clearness of its parts, in virtue of which logicians called an idea "distinct", that is, clarified by analysis of just what makes it applicable. Elsewhere, echoing Kant, Peirce called a likewise distinct definition "nominal" (CP 5.553).
Clearness in virtue of clearness of conceivable practical implications of the object's conceived effects, such that fosters fruitful reasoning, especially on difficult problems. Here he introduced that which he later called the pragmatic maxim.
By way of example of how to clarify conceptions, he addressed conceptions about truth and the real as questions of the presuppositions of reasoning in general. In clearness's second grade (the "nominal" grade), he defined truth as a sign's correspondence to its object, and the real as the object of such correspondence, such that truth and the real are independent of that which you or I or any actual, definite community of inquirers think. After that needful but confined step, next in clearness's third grade (the pragmatic, practice-oriented grade) he defined truth as that opinion which would be reached, sooner or later but still inevitably, by research taken far enough, such that the real does depend on that ideal final opinion—a dependence to which he appeals in theoretical arguments elsewhere, for instance for the long-run validity of the rule of induction. Peirce argued that even to argue against the independence and discoverability of truth and the real is to presuppose that there is, about that very question under argument, a truth with just such independence and discoverability.
Peirce said that a conception's meaning consists in "all general modes of rational conduct" implied by "acceptance" of the conception—that is, if one were to accept, first of all, the conception as true, then what could one conceive to be consequent general modes of rational conduct by all who accept the conception as true?—the whole of such consequent general modes is the whole meaning. His pragmatism does not equate a conception's meaning, its intellectual purport, with the conceived benefit or cost of the conception itself, like a meme (or, say, propaganda), outside the perspective of its being true, nor, since a conception is general, is its meaning equated with any definite set of actual consequences or upshots corroborating or undermining the conception or its worth. His pragmatism also bears no resemblance to "vulgar" pragmatism, which misleadingly connotes a ruthless and Machiavellian search for mercenary or political advantage. Instead the pragmatic maxim is the heart of his pragmatism as a method of experimentational mental reflection arriving at conceptions in terms of conceivable confirmatory and disconfirmatory circumstances—a method hospitable to the formation of explanatory hypotheses, and conducive to the use and improvement of verification.
Peirce's pragmatism, as method and theory of definitions and conceptual clearness, is part of his theory of inquiry, which he variously called speculative, general, formal or universal rhetoric or simply methodeutic. He applied his pragmatism as a method throughout his work.
===Theory of inquiry===
In "The Fixation of Belief" (1877), Peirce gives his take on the psychological origin and aim of inquiry. On his view, individuals are motivated to inquiry by desire to escape the feelings of anxiety and unease which Peirce takes to be characteristic of the state of doubt. Doubt is described by Peirce as an "uneasy and dissatisfied state from which we struggle to free ourselves and pass into the state of belief." Peirce uses words like "irritation" to describe the experience of being in doubt and to explain why he thinks we find such experiences to be motivating. The irritating feeling of doubt is appeased, Peirce says, through our efforts to achieve a settled state of satisfaction with what we land on as our answer to the question which led to that doubt in the first place. This settled state, namely, belief, is described by Peirce as "a calm and satisfactory state which we do not wish to avoid." Our efforts to achieve the satisfaction of belief, by whichever methods we may pursue, are what Peirce calls "inquiry". Four methods which Peirce describes as having been actually pursued throughout the history of thought are summarized below in the section after next.
====Critical common-sensism====
Critical common-sensism, treated by Peirce as a consequence of his pragmatism, is his combination of Thomas Reid's common-sense philosophy with a fallibilism that recognizes that propositions of our more or less vague common sense now indubitable may later come into question, for example because of transformations of our world through science. It includes efforts to raise genuine doubts in tests for a core group of common indubitables that change slowly, if at all.
====Rival methods of inquiry====
In "The Fixation of Belief" (1877), Peirce described inquiry in general not as the pursuit of truth per se but as the struggle to move from irritating, inhibitory doubt born of surprise, disagreement, and the like, and to reach a secure belief, belief being that on which one is prepared to act. That let Peirce frame scientific inquiry as part of a broader spectrum and as spurred, like inquiry generally, by actual doubt, not mere verbal, quarrelsome, or hyperbolic doubt, which he held to be fruitless. Peirce sketched four methods of settling opinion, ordered from least to most successful:
The method of (policy of sticking to initial belief) – which brings comforts and decisiveness but leads to trying to ignore contrary information and others' views as if truth were intrinsically private, not public. The method goes against the social impulse and easily falters since one may well notice when another's opinion seems as good as one's own initial opinion. Its successes can be brilliant but tend to be transitory.
The method of – which overcomes disagreements but sometimes brutally. Its successes can be majestic and long-lasting, but it cannot regulate people thoroughly enough to withstand doubts indefinitely, especially when people learn about other societies present and past.
The method of the – which promotes conformity less brutally but fosters opinions as something like tastes, arising in conversation and comparisons of perspectives in terms of "what is agreeable to reason". Thereby it depends on fashion in paradigms and goes in circles over time. It is more intellectual and respectable but, like the first two methods, sustains accidental and capricious beliefs, destining some minds to doubt it.
The method of – wherein inquiry supposes that the real is discoverable but independent of particular opinion, such that, unlike in the other methods, inquiry can, by its own account, go wrong (fallibilism), not only right, and thus purposely tests itself and criticizes, corrects, and improves itself.
Peirce held that, in practical affairs, slow and stumbling ratiocination is often dangerously inferior to instinct and traditional sentiment, and that the scientific method is best suited to theoretical research, which in turn should not be trammeled by the other methods and practical ends; reason's "first rule" is summarized below (except as otherwise noted). There he also reviewed plausibility and inductive precision (issues of critique of arguments).
Abductive (or retroductive) phase. Guessing, inference to explanatory hypotheses for selection of those best worth trying. From abduction, Peirce distinguishes induction as inferring, on the basis of tests, the proportion of truth in the hypothesis. Every inquiry, whether into ideas, brute facts, or norms and laws, arises from surprising observations in one or more of those realms (and for example at any stage of an inquiry already underway). All explanatory content of theories comes from abduction, which guesses a new or outside idea so as to account in a simple, economical way for a surprising or complicated phenomenon. The modicum of success in our guesses far exceeds that of random luck, and seems born of attunement to nature by developed or inherent instincts, especially insofar as best guesses are optimally plausible and simple in the sense of the "facile and natural", as by Galileo's natural light of reason and as distinct from "logical simplicity". Abduction is the most fertile but least secure mode of inference. Its general rationale is inductive: it succeeds often enough and it has no substitute in expediting us toward new truths. In 1903, Peirce called pragmatism "the logic of abduction". Coordinative method leads from abducting a plausible hypothesis to judging it for its testability and for how its trial would economize inquiry itself. The hypothesis, being insecure, needs to have practical implications leading at least to mental tests and, in science, lending themselves to scientific tests. A simple but unlikely guess, if not costly to test for falsity, may belong first in line for testing. A guess is intrinsically worth testing if it has plausibility or reasoned objective probability, while subjective likelihood, though reasoned, can be misleadingly seductive. Guesses can be selected for trial strategically, for their caution (for which Peirce gave as example the game of Twenty Questions), breadth, or incomplexity. One can discover only that which would be revealed through their sufficient experience anyway, and so the point is to expedite it; economy of research demands the leap, so to speak, of abduction and governs its art. In 1893, Peirce restated most of it for a less advanced audience.
== Logic, or semiotic ==
In 1918, the logician C. I. Lewis wrote, "The contributions of C.S. Peirce to symbolic logic are more numerous and varied than those of any other writer—at least in the nineteenth century."
=== Relational logic ===
Beginning with his first paper on the "Logic of Relatives" (1870), Peirce extended the theory of relations pioneered by Augustus De Morgan.{{efn|Much of the mathematics of relations now taken for granted was "borrowed" from Peirce, not always with all due credit; on that and on how the young Bertrand Russell, especially his Principles of Mathematics and Principia Mathematica, did not do Peirce justice, see Anellis (1995). of Arthur W. Burks, a Peirce scholar. In economics, relational logic was used by Frank P. Ramsey, John von Neumann, and Paul Samuelson to study preferences and utility and by Kenneth J. Arrow in Social Choice and Individual Values, following Arrow's association with Tarski at City College of New York.
=== Quantifiers ===
On Peirce and his contemporaries Ernst Schröder and Gottlob Frege, Hilary Putnam (1982) and logician William Ernest Johnson, both British;
The Polish school of logic and foundational mathematics, including Alfred Tarski;
Arthur Prior, who praised and studied Peirce's logical work in a 1964 paper and Randall Dipert's chapter in Cheryl Misak (2004).
==== Logic as philosophical ====
Peirce regarded logic per se as a division of philosophy, as a normative science based on esthetics and ethics, as more basic than metaphysics, and as "the art of devising methods of research". More generally, as inference, "logic is rooted in the social principle", since inference depends on a standpoint that, in a sense, is unlimited. Peirce called (with no sense of deprecation) "mathematics of logic" much of the kind of thing which, in current research and applications, is called simply "logic". He was productive in both (philosophical) logic and logic's mathematics, which were connected deeply in his work and thought.
Peirce argued that logic is formal semiotic: the formal study of signs in the broadest sense, not only signs that are artificial, linguistic, or symbolic, but also signs that are semblances or are indexical such as reactions. Peirce held that "all this universe is perfused with signs, if it is not composed exclusively of signs", along with their representational and inferential relations. He argued that, since all thought takes time, all thought is in signs and sign processes ("semiosis") such as the inquiry process. He divided logic into: (1) speculative grammar, or stechiology, on how signs can be meaningful and, in relation to that, what kinds of signs there are, how they combine, and how some embody or incorporate others; (2) logical critic, or logic proper, on the modes of inference; and (3) speculative or universal rhetoric, or methodeutic,
==== Four incapacities ====
The Journal of Speculative Philosophy series (1868–1869), including
Questions concerning certain Faculties claimed for Man (1868)
Some Consequences of Four Incapacities (1868)
Grounds of Validity of the Laws of Logic:Further Consequences of Four Incapacities (1869) In three articles in 1868–1869, Peirce rejected mere verbal or hyperbolic doubt and first or ultimate principles, and argued that we have (as he numbered them
==== Logic as formal semiotic ====
Peirce sought, through his wide-ranging studies through the decades, formal philosophical ways to articulate thought's processes, and also to explain the workings of science. These inextricably entangled questions of a dynamics of inquiry rooted in nature and nurture led him to develop his semiotic with very broadened conceptions of signs and inference, and, as its culmination, a theory of inquiry for the task of saying 'how science works' and devising research methods. This would be logic by the medieval definition taught for centuries: art of arts, science of sciences, having the way to the principles of all methods. As to signs in thought, Peirce emphasized the reverse: "To say, therefore, that thought cannot happen in an instant, but requires a time, is but another way of saying that every thought must be interpreted in another, or that all thought is in signs."—the focus is on sign action in general rather than on psychology, linguistics, or social studies (fields which he also pursued).
Inquiry is a kind of inference process, a manner of thinking and semiosis. Global divisions of ways for phenomena to stand as signs, and the subsumption of inquiry and thinking within inference as a sign process, enable the study of inquiry on semiotics' three levels:
Conditions for meaningfulness. Study of significatory elements and combinations, their grammar.
Validity, conditions for true representation. Critique of arguments in their various separate modes.
Conditions for determining interpretations. Methodology of inquiry in its mutually interacting modes.
Peirce uses examples often from common experience, but defines and discusses such things as assertion and interpretation in terms of philosophical logic. In a formal vein, Peirce said:
== Signs ==
=== Sign relation ===
Peirce's theory of signs is known to be one of the most complex semiotic theories due to its generalistic claim. Anything is a sign—not absolutely as itself, but instead in some relation or other. The sign relation is the key. It defines three roles encompassing (1) the sign, (2) the sign's subject matter, called its object, and (3) the sign's meaning or ramification as formed into a kind of effect called its interpretant (a further sign, for example a translation). It is an irreducible triadic relation, according to Peirce. The roles are distinct even when the things that fill those roles are not. The roles are but three; a sign of an object leads to one or more interpretants, and, as signs, they lead to further interpretants.
Extension × intension = information. Two traditional approaches to sign relation, necessary though insufficient, are the way of extension (a sign's objects, also called breadth, denotation, or application) and the way of intension (the objects' characteristics, qualities, attributes referenced by the sign, also called depth, comprehension, significance, or connotation). Peirce adds a third, the way of information, including change of information, to integrate the other two approaches into a unified whole. For example, because of the equation above, if a term's total amount of information stays the same, then the more that the term 'intends' or signifies about objects, the fewer are the objects to which the term 'extends' or applies.
Determination. A sign depends on its object in such a way as to represent its object—the object enables and, in a sense, determines the sign. A physically causal sense of this stands out when a sign consists in an indicative reaction. The interpretant depends likewise on both the sign and the object—an object determines a sign to determine an interpretant. But this determination is not a succession of dyadic events, like a row of toppling dominoes; sign determination is triadic. For example, an interpretant does not merely represent something which represented an object; instead an interpretant represents something as a sign representing the object. The object (be it a quality or fact or law or even fictional) determines the sign to an interpretant through one's collateral experience with the object, in which the object is found or from which it is recalled, as when a sign consists in a chance semblance of an absent object. Peirce used the word "determine" not in a strictly deterministic sense, but in a sense of "specializes", bestimmt, involving variable amount, like an influence. Peirce came to define representation and interpretation in terms of (triadic) determination. The object determines the sign to determine another sign—the interpretant—to be related to the object as the sign is related to the object, hence the interpretant, fulfilling its function as sign of the object, determines a further interpretant sign. The process is logically structured to perpetuate itself, and is definitive of sign, object, and interpretant in general. As Peirce sometimes put it (he defined sign at least 76 times All of those are special or partial objects. The object most accurately is the universe of discourse to which the partial or special object belongs.
An interpretant (or interpretant sign) is a sign's meaning or ramification as formed into a kind of idea or effect, an interpretation, human or otherwise. An interpretant is a sign (a) of the object and (b) of the interpretant's "predecessor" (the interpreted sign) as a sign of the same object. An interpretant either (i) is immediate to a sign and is a kind of quality or possibility such as a word's usual meaning, or (ii) is a dynamic interpretant, such as a state of agitation, or (iii) is a final or normal interpretant, a sum of the lessons which a sufficiently considered sign would have as effects on practice, and with which an actual interpretant may at most coincide.
Some of the understanding needed by the mind depends on familiarity with the object. To know what a given sign denotes, the mind needs some experience of that sign's object, experience outside of, and collateral to, that sign or sign system. In that context Peirce speaks of collateral experience, collateral observation, collateral acquaintance, all in much the same terms. This typology classifies every sign according to the sign's own phenomenological category—the qualisign is a quality, a possibility, a "First"; the sinsign is a reaction or resistance, a singular object, an actual event or fact, a "Second"; and the legisign is a habit, a rule, a representational relation, a "Third".
II. Icon, index, symbol: This typology, the best known one, classifies every sign according to the category of the sign's way of denoting its object—the icon (also called semblance or likeness) by a quality of its own, the index by factual connection to its object, and the symbol by a habit or rule for its interpretant.
III. Rheme, dicisign, argument (also called sumisign, dicisign, suadisign, also seme, pheme, delome, He does this by rearranging the rule (Barbara's major premise), the case (Barbara's minor premise), and the result (Barbara's conclusion):
Deduction.
Rule: All the beans from this bag are white.
Case: These beans are beans from this bag.
\therefore Result: These beans are white.
Induction.
Case: These beans are [randomly selected] from this bag.
Result: These beans are white.
\therefore Rule: All the beans from this bag are white.
Hypothesis (Abduction).
Rule: All the beans from this bag are white.
Result: These beans [oddly] are white.
\therefore Case: These beans are from this bag.
In 1883, in "A Theory of Probable Inference" (Studies in Logic), Peirce equated hypothetical inference with the induction of characters of objects (as he had done in effect before
The logical form does not also cover induction, since induction neither depends on surprise nor proposes a new idea for its conclusion. Induction seeks facts to test a hypothesis; abduction seeks a hypothesis to account for facts. "Deduction proves that something must be; Induction shows that something actually is operative; Abduction merely suggests that something may be." Peirce did not remain quite convinced that one logical form covers all abduction. In his methodeutic or theory of inquiry (see below), he portrayed abduction as an economic initiative to further inference and study, and portrayed all three modes as clarified by their coordination in essential roles in inquiry: hypothetical explanation, deductive prediction, inductive testing
== Metaphysics ==
Peirce divided metaphysics into (1) ontology or general metaphysics, (2) psychical or religious metaphysics, and (3) physical metaphysics.
=== Ontology ===
On the issue of universals, Peirce was a scholastic realist, declaring the reality of generals as early as 1868. According to Peirce, his category he called "thirdness", the more general facts about the world, are extra-mental realities. Regarding modalities (possibility, necessity, etc.), he came in later years to regard himself as having wavered earlier as to just how positively real the modalities are. In his 1897 "The Logic of Relatives" he wrote:
Peirce retained, as useful for some purposes, the definitions in terms of information states, but insisted that the pragmaticist is committed to a strong modal realism by conceiving of objects in terms of predictive general conditional propositions about how they would behave under certain circumstances.
==== Continua ====
Continuity and synechism are central in Peirce's philosophy: "I did not at first suppose that it was, as I gradually came to find it, the master-Key of philosophy".
From a mathematical point of view, he embraced infinitesimals and worked long on the mathematics of continua. He long held that the real numbers constitute a pseudo-continuum; that a true continuum is the real subject matter of analysis situs (topology); and that a true continuum of instants exceeds—and within any lapse of time has room for—any Aleph number (any infinite multitude as he called it) of instants.
In 1908 Peirce wrote that he found that a true continuum might have or lack such room. Jérôme Havenel (2008): "It is on 26 May 1908, that Peirce finally gave up his idea that in every continuum there is room for whatever collection of any multitude. From now on, there are different kinds of continua, which have different properties."
=== Psychical or religious metaphysics ===
Peirce believed in God, and characterized such belief as founded in an instinct explorable in musing over the worlds of ideas, brute facts, and evolving habits—and it is a belief in God not as an actual or existent being (in Peirce's sense of those words), but all the same as a real being. In "A Neglected Argument for the Reality of God" (1908), and (see Synechism) that there is at least an attenuated kind of immortality.
=== Physical metaphysics ===
Peirce held the view, which he called objective idealism, that "matter is effete mind, inveterate habits becoming physical laws". Peirce observed that "Berkeley's metaphysical theories have at first sight an air of paradox and levity very unbecoming to a bishop".
Peirce asserted the reality of (1) "absolute chance" or randomness (his tychist view), (2) "mechanical necessity" or physical laws (anancist view), and (3) what he called the "law of love" (agapist view), echoing his categories Firstness, Secondness, and Thirdness, respectively. of the cosmos and its parts. He found his conception of agapasm embodied in Lamarckian evolution; the overall idea in any case is that of evolution tending toward an end or goal, and it could also be the evolution of a mind or a society; it is the kind of evolution which manifests workings of mind in some general sense. He said that overall he was a synechist, holding with reality of continuity, especially of space, time, and law.
===Some noted articles===
The Monist Metaphysical Series (1891–1893)
The Architecture of Theories (1891)
The Doctrine of Necessity Examined (1892)
The Law of Mind (1892)
Man's Glassy Essence (1892)
Evolutionary Love (1893)
Immortality in the Light of Synechism (1893 MS)
== Philosophy of science ==
Peirce outlined two fields, "Cenoscopy" and "Science of Review", both of which he called philosophy. Both included philosophy about science. In 1903 he arranged them, from more to less theoretically basic, thus:
Science of Discovery.
Mathematics.
Cenoscopy (philosophy as discussed earlier in this article – categorial, normative, metaphysical), as First Philosophy, concerns positive phenomena in general, does not rely on findings from special sciences, and includes the general study of inquiry and scientific method.
Idioscopy, or the Special Sciences (of nature and mind).
Science of Review, as Ultimate Philosophy, arranges "... the results of discovery, beginning with digests, and going on to endeavor to form a philosophy of science". His examples included Humboldt's Cosmos, Comte's Philosophie positive, and Spencer's Synthetic Philosophy.
Practical Science, or the Arts.
Peirce placed, within Science of Review, the work and theory of classifying the sciences (including mathematics and philosophy). His classifications, on which he worked for many years, draw on argument and wide knowledge, and are of interest both as a map for navigating his philosophy and as an accomplished polymath's survey of research in his time.
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6,118 |
Carnot heat engine
|
A Carnot heat engine is a theoretical heat engine that operates on the Carnot cycle. The basic model for this engine was developed by Nicolas Léonard Sadi Carnot in 1824. The Carnot engine model was graphically expanded by Benoît Paul Émile Clapeyron in 1834 and mathematically explored by Rudolf Clausius in 1857, work that led to the fundamental thermodynamic concept of entropy. The Carnot engine is the most efficient heat engine which is theoretically possible. The efficiency depends only upon the absolute temperatures of the hot and cold heat reservoirs between which it operates.
A heat engine acts by transferring energy from a warm region to a cool region of space and, in the process, converting some of that energy to mechanical work. The cycle may also be reversed. The system may be worked upon by an external force, and in the process, it can transfer thermal energy from a cooler system to a warmer one, thereby acting as a refrigerator or heat pump rather than a heat engine.
Every thermodynamic system exists in a particular state. A thermodynamic cycle occurs when a system is taken through a series of different states, and finally returned to its initial state. In the process of going through this cycle, the system may perform work on its surroundings, thereby acting as a heat engine.
The Carnot engine is a theoretical construct, useful for exploring the efficiency limits of other heat engines. An actual Carnot engine, however, would be completely impractical to build.
== Carnot's diagram ==
In the adjacent diagram, from Carnot's 1824 work, Reflections on the Motive Power of Fire, there are "two bodies A and B, kept each at a constant temperature, that of A being higher than that of B. These two bodies to which we can give, or from which we can remove the heat without causing their temperatures to vary, exercise the functions of two unlimited reservoirs of caloric. We will call the first the furnace and the second the refrigerator." Carnot then explains how we can obtain motive power, i.e., "work", by carrying a certain quantity of heat from body A to body B.
It also acts as a cooler and hence can also act as a refrigerator.
== Modern diagram ==
The previous image shows the original piston-and-cylinder diagram used by Carnot in discussing his ideal engine. The figure at right shows a block diagram of a generic heat engine, such as the Carnot engine. In the diagram, the "working body" (system), a term introduced by Clausius in 1850, can be any fluid or vapor body through which heat Q can be introduced or transmitted to produce work. Carnot had postulated that the fluid body could be any substance capable of expansion, such as vapor of water, vapor of alcohol, vapor of mercury, a permanent gas, air, etc. Although in those early years, engines came in a number of configurations, typically QH was supplied by a boiler, wherein water was boiled over a furnace; QC was typically removed by a stream of cold flowing water in the form of a condenser located on a separate part of the engine. The output work, W, is transmitted by the movement of the piston as it is used to turn a crank-arm, which in turn was typically used to power a pulley so as to lift water out of flooded salt mines. Carnot defined work as "weight lifted through a height".
==Carnot cycle==
The Carnot cycle when acting as a heat engine consists of the following steps:
Reversible isothermal expansion of the gas at the "hot" temperature, (isothermal heat addition or absorption). During this step ( to ) the gas is allowed to expand and it does work on the surroundings. The temperature of the gas (the system) does not change during the process, and thus the expansion is isothermic. The gas expansion is propelled by absorption of heat energy and of entropy from the high temperature reservoir.
Isentropic (reversible adiabatic) expansion of the gas (isentropic work output). For this step ( to ) the piston and cylinder are assumed to be thermally insulated, thus they neither gain nor lose heat. The gas continues to expand, doing work on the surroundings, and losing an equivalent amount of internal energy. The gas expansion causes it to cool to the "cold" temperature, . The entropy remains unchanged.
Reversible isothermal compression of the gas at the "cold" temperature, (isothermal heat rejection) ( to ). Now the gas is exposed to the cold temperature reservoir while the surroundings do work on the gas by compressing it (such as through the return compression of a piston), while causing an amount of waste heat (with the standard sign convention for heat) and of entropy to flow out of the gas to the low temperature reservoir. (In magnitude, this is the same amount of entropy absorbed in step 1. The entropy decreases in isothermal compression since the multiplicity of the system decreases with the volume.) In terms of magnitude, the recompression work performed by the surroundings in this step is less than the work performed on the surroundings in step 1 because it occurs at a lower pressure due to the lower temperature (i.e. the resistance to compression is lower under step 3 than the force of expansion under step 1). We can refer to the first law of thermodynamics to explain this behavior: .
Isentropic compression of the gas (isentropic work input) ( to ). Once again the piston and cylinder are assumed to be thermally insulated and the cold temperature reservoir is removed. During this step, the surroundings continue to do work to further compress the gas and both the temperature and pressure rise now that the heat sink has been removed. This additional work increases the internal energy of the gas, compressing it and causing the temperature to rise to . The entropy remains unchanged. At this point the gas is in the same state as at the start of step 1.
== Carnot's theorem ==
Carnot's theorem is a formal statement of this fact: No engine operating between two heat reservoirs can be more efficient than a Carnot engine operating between the same reservoirs.
\eta_{I}=\frac{W}{Q_{\mathrm{H}}}=1-\frac{T_{\mathrm{C}}}{T_{\mathrm{H}}}
===Explanation===
This maximum efficiency is defined as above:
is the work done by the system (energy exiting the system as work),
is the heat put into the system (heat energy entering the system),
is the absolute temperature of the cold reservoir, and
is the absolute temperature of the hot reservoir.
A corollary to Carnot's theorem states that: All reversible engines operating between the same heat reservoirs are equally efficient.
It is easily shown that the efficiency is maximum when the entire cyclic process is a reversible process. This means the total entropy of system and surroundings (the entropies of the hot furnace, the "working fluid" of the heat engine, and the cold sink) remains constant when the "working fluid" completes one cycle and returns to its original state. (In the general and more realistic case of an irreversible process, the total entropy of this combined system would increase.)
Since the "working fluid" comes back to the same state after one cycle, and entropy of the system is a state function, the change in entropy of the "working fluid" system is 0. Thus, it implies that the total entropy change of the furnace and sink is zero, for the process to be reversible and the efficiency of the engine to be maximum. This derivation is carried out in the next section.
The coefficient of performance (COP) of the heat engine is the reciprocal of its efficiency.
== Efficiency of real heat engines ==
For a real heat engine, the total thermodynamic process is generally irreversible. The working fluid is brought back to its initial state after one cycle, and thus the change of entropy of the fluid system is 0, but the sum of the entropy changes in the hot and cold reservoir in this one cyclical process is greater than 0.
The internal energy of the fluid is also a state variable, so its total change in one cycle is 0. So the total work done by the system is equal to the net heat put into the system, the sum of Q_\text{H} > 0 taken up and the waste heat Q_\text{C} < 0 given off:
For real engines, stages 1 and 3 of the Carnot cycle, in which heat is absorbed by the "working fluid" from the hot reservoir, and released by it to the cold reservoir, respectively, no longer remain ideally reversible, and there is a temperature differential between the temperature of the reservoir and the temperature of the fluid while heat exchange takes place.
During heat transfer from the hot reservoir at T_\text{H} to the fluid, the fluid would have a slightly lower temperature than T_\text{H}, and the process for the fluid may not necessarily remain isothermal.
Let \Delta S_\text{H} be the total entropy change of the fluid in the process of intake of heat.
\frac{\text{d}Q_\text{H}}{T} |LnSty=1px dashed |3}}
where the temperature of the fluid is always slightly lesser than T_\text{H}, in this process.
So, one would get:
{T_\text{H}}=\frac{\int \text{d}Q_\text{H}}{T_\text{H}} \leq \Delta S_\text{H} |LnSty=1px dashed |4}}
Similarly, at the time of heat injection from the fluid to the cold reservoir one would have, for the magnitude of total entropy change \Delta S_\text{C} < 0 of the fluid in the process of expelling heat:
{T_\text{C}}< 0 |LnSty=1px dashed |5}}
where, during this process of transfer of heat to the cold reservoir, the temperature of the fluid is always slightly greater than T_\text{C}.
We have only considered the magnitude of the entropy change here. Since the total change of entropy of the fluid system for the cyclic process is 0, we must have
The previous three equations, namely (), (), (), substituted into () to give:
{T_\text{C}}\geqslant\frac{Q_\text{H}}{T_\text{H}} |LnSty=1px dashed |7}}
For [ΔSh ≥ (Qh/Th)] +[ΔSc ≥ (Qc/Tc)] = 0
[ΔSh ≥ (Qh/Th)] = - [ΔSc ≥ (Qc/Tc)]
= [-ΔSc ≤ (-Qc/Tc)]
it is at least (Qh/Th) ≤ (-Qc/Tc)
Equations () and () combine to give
\leq 1- \frac{T_\text{C}}{T_\text{H}} |LnSty=1px dashed |8}}
To derive this step needs two adiabatic processes involved to show an isentropic process property for the ratio of the changing volumes of two isothermal processes are equal.
Most importantly, since the two adiabatic processes are volume works without heat lost, and since the ratio of volume changes for this two processes are the same, so the works for these two adiabatic processes are the same with opposite direction to each other, namely, one direction is work done by the system and the other is work done on the system; therefore, heat efficiency only concerns the amount of work done by the heat absorbed comparing to the amount of heat absorbed by the system.
Therefore, (W/Qh) = (Qh - Qc) / Qh
= 1 - (Qc/Qh)
= 1 - (Tc/Th)
And, from ()
(Qh/Th) ≤ (-Qc/Tc) here Qc it is less than 0 (release heat)
(Tc/Th) ≤ (-Qc/Qh)
-(Tc/Th) ≥ (Qc/Qh)
1+[-(Tc/Th)] ≥ 1+(Qc/Qh)
1 - (Tc/Th) ≥ (Qh + Qc)/Qh here Qc\eta = \frac{W}{Q_\text{H}} is the efficiency of the real engine, and \eta_\text{I} is the efficiency of the Carnot engine working between the same two reservoirs at the temperatures T_\text{H} and T_\text{C}. For the Carnot engine, the entire process is 'reversible', and Equation () is an equality. Hence, the efficiency of the real engine is always less than the ideal Carnot engine.
Equation () signifies that the total entropy of system and surroundings (the fluid and the two reservoirs) increases for the real engine, because (in a surroundings-based analysis) the entropy gain of the cold reservoir as Q_\text{C} flows into it at the fixed temperature T_\text{C}, is greater than the entropy loss of the hot reservoir as Q_\text{H} leaves it at its fixed temperature T_\text{H}. The inequality in Equation () is essentially the statement of the Clausius theorem.
According to the second theorem, "The efficiency of the Carnot engine is independent of the nature of the working substance".
==The Carnot engine and Rudolf Diesel==
In 1892 Rudolf Diesel patented an internal combustion engine inspired by the Carnot engine. Diesel knew a Carnot engine is an ideal that cannot be built, but he thought he had invented a working approximation. His principle was unsound, but in his struggle to implement it he developed a practical Diesel engine.
The conceptual problem was how to achieve isothermal expansion in an internal combustion engine, since burning fuel at the highest temperature of the cycle would only raise the temperature further. Diesel's patented solution was: having achieved the highest temperature just by compressing the air, to add a small amount of fuel at a controlled rate, such that heating caused by burning the fuel would be counteracted by cooling caused by air expansion as the piston moved. Hence all the heat from the fuel would be transformed into work during the isothermal expansion, as required by Carnot's theorem.
For the idea to work a small mass of fuel would have to be burnt in a huge mass of air. Diesel first proposed a working engine that would compress air to 250 atmospheres at , then cycle to one atmosphere at . However, this was well beyond the technological capabilities of the day, since it implied a compression ratio of 60:1. Such an engine, if it could have been built, would have had an efficiency of 73%. (In contrast, the best steam engines of his day achieved 7%.)
Accordingly, Diesel sought to compromise. He calculated that, were he to reduce the peak pressure to a less ambitious 90 atmospheres, he would sacrifice only 5% of the thermal efficiency. Seeking financial support, he published the "Theory and Construction of a Rational Heat Engine to Take the Place of the Steam Engine and All Presently Known Combustion Engines" (1893). Endorsed by scientific opinion, including Lord Kelvin, he won the backing of Krupp and . He clung to the Carnot cycle as a symbol. But years of practical work failed to achieve an isothermal combustion engine, nor could have done, since it requires such an enormous quantity of air that it cannot develop enough power to compress it. Furthermore, controlled fuel injection turned out to be no easy matter.
Even so, the Diesel engine slowly evolved over 25 years to become a practical high-compression air engine, its fuel injected near the end of the compression stroke and ignited by the heat of compression, capable by 1969 of 40% efficiency.
== As a macroscopic construct ==
The Carnot heat engine is, ultimately, a theoretical construct based on an idealized thermodynamic system. On a practical human-scale level the Carnot cycle has proven a valuable model, as in advancing the development of the diesel engine. However, on a macroscopic scale limitations placed by the model's assumptions prove it impractical, and, ultimately, incapable of doing any work. As such, per Carnot's theorem, the Carnot engine may be thought as the theoretical limit of macroscopic scale heat engines rather than any practical device that could ever be built.
For example, for the isothermal expansion part of the Carnot cycle, the following
infinitesimal conditions must be satisfied simultaneously at every step in the expansion:
The hot reservoir temperature TH is infinitesimally higher than the system gas temperature T so heat flow (energy transfer) from the hot reservoir to the gas is made without increasing T (via infinitesimal work on the surroundings by the gas as another energy transfer); if TH is significantly higher than T, then T may be not uniform through the gas so the system would deviate from thermal equilibrium as well as not being a reversible process (i.e. not a Carnot cycle) or T might increase noticeably so it would not be an isothermal process.
The force externally applied on the piston (opposite to the internal force on the piston by the gas) needs to be infinitesimally reduced externally. Without this assistance, it would not be possible to follow a gas PV (Pressure-Volume) curve downward at a constant T since following this curve means that the gas-to-piston force decreases (P decreases) as the volume expands (the piston moves outward). If this assistance is so strong that the volume expansion is significant, the system may deviate from thermal equilibrium, and the process fail to be reversible (and thus not a Carnot cycle).
Such "infinitesimal" requirements as these (and others) cause the Carnot cycle to take an infinite amount of time, rendering the production of work impossible.
Other practical requirements that make the Carnot cycle impractical to realize include fine control of the gas, and perfect thermal contact with the surroundings (including high and low temperature reservoirs).
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6,119 |
Context-sensitive
|
Context-sensitive is an adjective meaning "depending on context" or "depending on circumstances". It may refer to:
Context-sensitive meaning, where meaning depends on context (language use)
Context-sensitive grammar, a formal grammar in which the left-hand sides and right-hand sides of any production rules may be surrounded by a context of terminal and nonterminal symbols
Context-sensitive language, a formal language that can be defined by a context-sensitive grammar (and equivalently by a noncontracting grammar). Context-sensitive is one of the four types of grammars in the Chomsky hierarchy
Context-sensitive help, a kind of online help that is obtained from a specific point in the state of the software, providing help for the situation that is associated with that state
Context-sensitive solutions (also called Context Sensitive Design), a theoretical and practical approach to transportation decision-making and design that takes into consideration the communities and lands through which streets, roads, and highways pass ("the context")
Context-sensitive user interface, in computing
|
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6,121 |
Central America
|
Central America is a subregion of North America. Its political boundaries are defined as bordering Mexico to the north, Colombia to the southeast, the Caribbean to the east, and the Pacific Ocean to the southwest. Central America is usually defined as consisting of seven countries: Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and Panama. Within Central America is the Mesoamerican biodiversity hotspot, which extends from southern Mexico to southeastern Panama. Due to the presence of several active geologic faults and the Central America Volcanic Arc, there is a high amount of seismic activity in the region, such as volcanic eruptions and earthquakes, which has resulted in death, injury, and property damage.
Most of Central America falls under the Isthmo-Colombian cultural area. Before the Spanish expedition of Christopher Columbus' voyages to the Americas, hundreds of indigenous peoples made their homes in the area. From the year 1502 onwards, Spain began their colonization. From 1609 to 1821, the majority of Central American territories (except for what would become Belize and Panama and including the modern Mexican state of Chiapas) were governed by the viceroyalty of New Spain from Mexico City as the Captaincy General of Guatemala. On 24 August 1821, Spanish Viceroy Juan de O'Donojú signed the Treaty of Córdoba, which established New Spain's independence and autonomy from mainland Spain. On 15 September, the Act of Independence of Central America was enacted to announce Central America's separation from the Spanish Empire. Some of New Spain's provinces in the Central American region were invaded and annexed to the First Mexican Empire; however in 1823 they seceded from Mexico to form the Federal Republic of Central America until 1838.
In 1838, Costa Rica, Guatemala, Honduras, and Nicaragua became the first of Central America's seven states to become independent countries, followed by El Salvador in 1841, Panama in 1903, and Belize in 1981. Despite the dissolution of the Federal Republic of Central America, the five remaining countries, save for Panama and Belize, all preserved and maintained a Central American identity.
The Spanish-speaking countries officially include both North America and South America as a single continent, , which is split into four subregions: Central America, Insular America (a.k.a. the West Indies), North America (Mexico and Northern America), and South America.
== Definitions ==
"Central America" may mean different things to various people, based upon different contexts:
The United Nations geoscheme for the Americas defines Central America as all states of mainland North America south of the United States, hence grouping Mexico as a part of Central America for statistics purposes, but historically and politically Mexico is considered North American.
In 1538, Spain established the Real Audiencia of Panama, which had jurisdiction over all land from the Strait of Magellan to the Gulf of Fonseca. This entity was dissolved in 1543, and most of the territory within Central America then fell under the jurisdiction of the Audiencia Real de Guatemala. This area included the current territories of Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and the Mexican state of Chiapas, but excluded the lands that would become Belize and Panama. The president of the Audiencia, which had its seat in Antigua Guatemala, was the governor of the entire area. In 1609 the area became a captaincy general and the governor was also granted the title of captain general. The Captaincy General of Guatemala encompassed most of Central America, with the exception of present-day Belize and Panama.
The Captaincy General of Guatemala lasted for more than two centuries, but began to fray after a rebellion in 1811 which began in the Intendancy of San Salvador. The Captaincy General formally ended on 15 September 1821, with the signing of the Act of Independence of Central America. Mexican independence was achieved at virtually the same time with the signing of the Treaty of Córdoba and the Declaration of Independence of the Mexican Empire, and the entire region was finally independent from Spanish authority by 28 September 1821.
From its independence from Spain in 1821 until 1823, the former Captaincy General remained intact as part of the short-lived First Mexican Empire. When the Emperor of Mexico abdicated on 19 March 1823, Central America again became independent. On 1 July 1823, the Congress of Central America peacefully seceded from Mexico and declared absolute independence from all foreign nations, and the region formed the Federal Republic of Central America.
The Federal Republic of Central America, initially known as the United Provinces of Central America, was a sovereign state that existed from 1823 to 1840. It was composed of five states: Guatemala, Honduras, El Salvador, Nicaragua, and Costa Rica. The federation was established after these regions declared independence from Spain in 1821 and briefly joined the Mexican Empire before breaking away to form their own union. The republic adopted a constitution in 1824, which was inspired by the federal system of the United States. It provided for a federal capital, initially located in Guatemala City, and a president for each of the five constituent states. The constitution abolished slavery and maintained the privileges of the Roman Catholic Church, while restricting suffrage to the upper classes.
The territory that now makes up Belize was heavily contested in a dispute that continued for decades after Guatemala achieved independence. Spain, and later Guatemala, considered this land a Guatemalan department. In 1862, Britain formally declared it a British colony and named it British Honduras. It became independent as Belize in 1981.
After more than two hundred years of social unrest, violent conflict, and revolution, Central America today remains in a period of political transformation. Poverty, social injustice, and violence are still widespread. The volcano with the most activity in Central America is Santa María. Still experiencing frequent eruptions to this day, with the last one beginning in 2013, and still is going on to this day.
Of the many mountain ranges within Central America, the longest are the Sierra Madre de Chiapas, the Cordillera Isabelia and the Cordillera de Talamanca. At , Volcán Tajumulco is the highest peak in Central America. Other high points of Central America are as listed in the table below:
Between the mountain ranges lie fertile valleys that are suitable for the raising of livestock and for the production of coffee, tobacco, beans and other crops. Most of the population of Honduras, Costa Rica and Guatemala lives in valleys.
Trade winds have a significant effect upon the climate of Central America. Temperatures in Central America are highest just prior to the summer wet season, and are lowest during the winter dry season, when trade winds contribute to a cooler climate. The highest temperatures occur in April, due to higher levels of sunlight, lower cloud cover and a decrease in trade winds. No timeline for implementation was discussed.
Central America already has several supranational institutions such as the Central American Parliament, the Central American Bank for Economic Integration and the Central American Common Market.
On 22 July 2011, President Mauricio Funes of El Salvador became the first president pro tempore to SICA. El Salvador also became the headquarters of SICA with the inauguration of a new building. The President of El Salvador, Nayib Bukele, broke diplomatic relations with Taiwan and established ties with China. On 9 December 2021, Nicaragua resumed relations with the PRC.
== Economy ==
File:Banco deGuatemala.JPG|Central Bank of Guatemala
File:World Trade Center San Salvador.jpg|World Trade Center San Salvador
File:BCH.jpg|Central Bank of Honduras
File:Maqueta del Banco Central de Nicaragua.jpg|Central Bank of Nicaragua
File:Banco Nacional de Panamá, en vía España de la ciudad de Panamá.jpg|National Bank of Panama
File:Belizean Central Bank 2015.jpg|Central Bank of Belize
Signed in 2004, the Central American Free Trade Agreement (CAFTA) is an agreement between the United States, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua, and the Dominican Republic. The treaty is aimed at promoting free trade among its members.
Guatemala has the largest economy in the region.
They are also criticised for the working conditions of employees: insults and physical violence, abusive dismissals (especially of pregnant workers), working hours, non-payment of overtime. According to Lucrecia Bautista, coordinator of the maquilas sector of the audit firm Coverco, "labour law regulations are regularly violated in maquilas and there is no political will to enforce their application. In the case of infringements, the labour inspectorate shows remarkable leniency. It is a question of not discouraging investors." Trade unionists are subject to pressure, and sometimes to kidnapping or murder. In some cases, business leaders have used the services of the maras. Finally, black lists containing the names of trade unionists or political activists are circulating in employers' circles.
!GDP(PPP)$ millions
Costa Rica is the most visited nation in Central America.
{{Multiple image|total_width = 600
| align = center
| direction = horizontal
| image1 = Life expectancy map -Central America -2019 -with names.png
| image2 = Life expectancy map -Central America -2020 -with names.png
| image3 = Life expectancy map -Central America -2021 -with names.png
| footer_align = center
| footer = Change in life expectancy in Central America from 2019 to 2021
Source: Jason Mandrik, Operation World Statistics (2020).
Protestantism in Central America also include Independent Christian, most of total Protestants in this region (+80%) are Evangelicals, the rest follow traditional beliefs.
Other Christian include Other Traditional Churches (Orthodox, Episcopalian, etc.) and contemporary churches (Mormons, Adventists, Scientology, etc.), also include Non-denominational Christian who are the most numerous group, specially in Guatemala.
=== Education ===
List of architecture schools in Central America
List of universities in Belize
List of universities in Costa Rica
List of universities in El Salvador
List of universities in Guatemala
List of universities in Honduras
List of universities in Nicaragua
List of universities in Panama
== Culture ==
===Art===
File:JacaltecBrocade.jpg|Guatemalan textiles
File:KunaWomanWithMolas.jpg|Mola, Panama
File:Mercaditode Artesanias en el Centro Historico de Santa Ana.JPG|El Salvador La Plama art form
===National dishes===
File:Cocinando El Pepian.jpg|Pepián Guatemala
File:Baleada.jpg|Baleada Honduras
File:Pupusas El Salvador Centro America.JPG|Pupusa El Salvador
File:SANCOCHO.jpg|Sancocho Panama
File:Gallo Pinto at breakfast.jpg|Gallo pinto Costa Rica
File:Nacatamal assembled.jpg|Nacatamal Nicaragua
File:Rice and Beans, Stew Chicken and Potato Salad - Belize.jpg|Rice and beans Belize
Central American music
Central American cuisine
List of cuisines of the Americas – Central American cuisine
=== Sport ===
Central American Games
Central American and Caribbean Games
1926 Central American and Caribbean Games – the first time this event occurred
Central American Football Union
Surfing
|
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"Agustín de Iturbide",
"Roatán",
"Rosario Murillo",
"Territorial dispute",
"Rhyncholaelia digbyana",
"Index of Nicaragua-related articles",
"Tilarán",
"Types of volcanic eruptions",
"Bogotá",
"Mesoamerican Barrier Reef System",
"habitat fragmentation",
"Mara (gang)",
"Xiomara Castro",
"Cayman Trough",
"Pinus oocarpa",
"Latin American cuisine",
"Bird migration",
"February 2001 El Salvador earthquake",
"Panama City",
"Middle America (Americas)",
"Arenal Volcano",
"Central American Bank for Economic Integration",
"Tegucigalpa",
"Salvadoran",
"Laurel forest",
"1717 Guatemala earthquake",
"Central American Integration System",
"Calycophyllum candidissimum",
"UTC−05:00",
"Cerro Chirripó",
"Index of Central America-related articles",
"Captaincy General of Guatemala",
"Miskito Coast Creole",
"Pacific Flyway",
"Johnny Briceño",
"1773 Guatemala earthquake",
"United Fruit Company",
"Pupusa",
"Protestantism",
"World",
"biodiversity hotspot",
"Amerindian",
"Central American Pacific Islands",
"List of universities in Costa Rica",
"Sonsonate",
"Metropolitan Cathedral of San José",
"Talamancan montane forests",
"The San Pedro Sun",
"Juan O'Donojú",
"Act of Independence of Central America",
"Mesoamerican languages",
"Tabebuia rosea",
"Central America Volcanic Arc",
"tropical moist forests",
"Index of Belize-related articles",
"deforestation",
"List of universities in Belize",
"Christianity",
"Drimys granadensis",
"Panama",
"San Miguel, El Salvador",
"Petén–Veracruz moist forests",
"San Salvador",
"three-wattled bellbird",
"The Guardian",
"exchange rate",
"1976 Guatemala earthquake",
"Municipalities of Nicaragua",
"Nacatamal",
"Departments of Guatemala",
"Gulf of Mexico",
"Ibero-America",
"volcanic eruption",
"Sterculia apetala",
"Central Bank of Honduras",
"Rodrigo Chaves Robles",
"Parque Internacional la Amistad",
"ecosystem",
"Volcán Arenal",
"cloud forest",
"Belize Barrier Reef",
"World Heritage Site",
"list of geographical societies",
"North American Plate",
"Swietenia macrophylla",
"Central American montane forests",
"Chibchan languages",
"1972 Nicaragua earthquake",
"fir",
"Antilles",
"Middle America Trench",
"Inter-American Highway",
"Northern America",
"Miskito people",
"Portuguese language",
"Venezuela",
"North America",
"Montecristo National Park",
"Central America under Mexican rule",
"K'iche' Kingdom of Q'umarkaj",
"tropical and subtropical moist broadleaf forests",
"List of countries and dependencies by area",
"Jiquilisco Bay",
"biome",
"subregion",
"List of universities in Guatemala",
"INCAE Business School",
"Tegucigalpa Cathedral",
"List of cuisines of the Americas",
"France",
"Federal Republic of Central America",
"1985 Mexico City earthquake",
"wet season",
"cypress",
"Santa Ana, El Salvador",
"Prosthechea cochleata",
"Cantons of Costa Rica",
"Sierra Madre de Chiapas",
"Plumeria",
"Black people",
"Chiapas",
"Mestizo",
"Mombacho",
"List of administrative divisions by country",
"Garifuna language",
"Mexico",
"Isthmus Department",
"1942 Guatemala earthquake",
"Altun Ha",
"White people",
"Taiwan",
"resplendent quetzal",
"Latin America and the Caribbean",
"Caribbean",
"List of municipalities in Belize",
"Province of Tierra Firme",
"Intendancy of San Salvador",
"Christopher Columbus",
"United States",
"mestizo",
"Laurus",
"Granadine Confederation",
"List of universities in Panama",
"Pacific/Chocó natural region",
"Maderas",
"January 2001 El Salvador earthquake",
"2009 Honduras earthquake",
"Maya peoples",
"1982 El Salvador earthquake",
"Motagua Fault",
"Lycaste skinneri",
"pine",
"Cayos Zapatilla",
"Kowoj",
"FAO",
"1980 Honduras earthquake",
"Kaqchikel people",
"Copan",
"Tamarindo, Costa Rica",
"José Raúl Mulino",
"Caribbean Plate",
"West Indies",
"British Honduras",
"La Nación (San José)",
"oak",
"San Miguelito District",
"Weinmannia",
"Bank of Guatemala",
"List of places in Guatemala",
"Monteverde Cloud Forest Reserve",
"Captaincies of the Spanish Empire",
"Index of Honduras-related articles",
"List of universities in El Salvador",
"Official language",
"Atlantic Ocean",
"Guarianthe skinneri",
"Sierra de las Minas",
"Stone spheres of Costa Rica",
"Mesoamerica",
"List of cities in Honduras",
"rainforest",
"precipitation",
"1956 Nicaragua earthquake",
"Nuevo Laredo",
"Harpy eagle",
"black guan",
"Neotropical realm",
"South America",
"Pipil people",
"Caribbean English",
"Tazumal",
"Trade winds",
"Central American Football Union",
"Treaty of Córdoba",
"Turquoise-browed motmot",
"Deforestation in Central America",
"Dominican Republic–Central America Free Trade Agreement",
"Antigua Guatemala",
"1811 Independence Movement",
"bare-necked umbrellabird",
"Cerro El Pital",
"United Nations geoscheme for the Americas",
"Ancient footprints of Acahualinca",
"Keel-billed toucan",
"Catholic Church",
"Index of Panama-related articles",
"archipelago",
"Santa María (volcano)",
"Lake Atitlán",
"list of countries and territories where Spanish is an official language",
"Central American Court of Justice",
"spider monkey",
"UTC−06:00",
"pro tempore",
"Central American pine-oak forests",
"Holy Redeemer Cathedral",
"Americas",
"Nicaragua",
"Óscar Arias",
"tropical and subtropical coniferous forests",
"Limonese Creole",
"Clay-colored thrush",
"List of cities in El Salvador",
"World Bank Group",
"cardamom",
"Scarlet macaw",
"Pacific Ocean",
"Central American and Caribbean Games",
"Central American music",
"Central American Common Market",
"Rice and beans",
"evergreen oak",
"Viceroyalty of New Granada",
"Daniel Ortega",
"invertebrate",
"World Trade Center San Salvador",
"Xincan languages",
"Monteverde",
"Cerro Las Minas",
"Maya civilization",
"Metropolitan Cathedral of Panama City",
"anteater",
"American Free Press",
"Tierra del Fuego",
"Central American Spanish",
"Monteverde, Costa Rica",
"Peristeria elata",
"Sify",
"List of universities in Honduras",
"Belize",
"Enterolobium cyclocarpum",
"free trade",
"Spanish language",
"Americas (terminology)",
"Mogotón",
"Guatemala City",
"Separation of Panama from Colombia",
"Dry season",
"2007 Guatemala earthquake",
"Mayan languages",
"Itza people",
"Jaguar",
"active fault",
"ecoregion",
"Wet season",
"Petén Basin",
"The Guianas",
"Amandala",
"transform fault",
"English language",
"Bajo Nuevo Bank",
"Volcán Tajumulco",
"List of architecture schools",
"Dominican Republic",
"Miskito language",
"Soconusco",
"Volcán Barú",
"temperate climate",
"life expectancy",
"Caribbean South America",
"Magnolia",
"Subregion",
"Central American Seaway",
"Spanish conquest of Guatemala",
"Yucca gigantea",
"Real Audiencia of Guatemala",
"Darién Gap",
"Resplendent quetzal",
"Immaculate Conception Cathedral, Managua",
"Chixoy-Polochic Fault",
"Panama State",
"tropical dry forests",
"1992 Nicaragua earthquake",
"Belizean Creole",
"Gulf of Fonseca",
"List of countries and dependencies by population",
"Mexico City"
] |
6,122 |
Continuous function
|
In mathematics, a continuous function is a function such that a small variation of the argument induces a small variation of the value of the function. This implies there are no abrupt changes in value, known as discontinuities. More precisely, a function is continuous if arbitrarily small changes in its value can be assured by restricting to sufficiently small changes of its argument. A discontinuous function is a function that is . Until the 19th century, mathematicians largely relied on intuitive notions of continuity and considered only continuous functions. The epsilon–delta definition of a limit was introduced to formalize the definition of continuity.
Continuity is one of the core concepts of calculus and mathematical analysis, where arguments and values of functions are real and complex numbers. The concept has been generalized to functions between metric spaces and between topological spaces. The latter are the most general continuous functions, and their definition is the basis of topology.
A stronger form of continuity is uniform continuity. In order theory, especially in domain theory, a related concept of continuity is Scott continuity.
As an example, the function denoting the height of a growing flower at time would be considered continuous. In contrast, the function denoting the amount of money in a bank account at time would be considered discontinuous since it "jumps" at each point in time when money is deposited or withdrawn.
==History==
A form of the epsilon–delta definition of continuity was first given by Bernard Bolzano in 1817. Augustin-Louis Cauchy defined continuity of y = f(x) as follows: an infinitely small increment \alpha of the independent variable x always produces an infinitely small change f(x+\alpha)-f(x) of the dependent variable y (see e.g. Cours d'Analyse, p. 34). Cauchy defined infinitely small quantities in terms of variable quantities, and his definition of continuity closely parallels the infinitesimal definition used today (see microcontinuity). The formal definition and the distinction between pointwise continuity and uniform continuity were first given by Bolzano in the 1830s, but the work wasn't published until the 1930s. Like Bolzano, Karl Weierstrass denied continuity of a function at a point c unless it was defined at and on both sides of c, but Édouard Goursat allowed the function to be defined only at and on one side of c, and Camille Jordan allowed it even if the function was defined only at c. All three of those nonequivalent definitions of pointwise continuity are still in use. Eduard Heine provided the first published definition of uniform continuity in 1872, but based these ideas on lectures given by Peter Gustav Lejeune Dirichlet in 1854.
==Real functions==
===Definition===
A real function that is a function from real numbers to real numbers can be represented by a graph in the Cartesian plane; such a function is continuous if, roughly speaking, the graph is a single unbroken curve whose domain is the entire real line. A more mathematically rigorous definition is given below.
Continuity of real functions is usually defined in terms of limits. A function with variable is continuous at the real number , if the limit of f(x), as tends to , is equal to f(c).
There are several different definitions of the (global) continuity of a function, which depend on the nature of its domain.
A function is continuous on an open interval if the interval is contained in the function's domain and the function is continuous at every interval point. A function that is continuous on the interval (-\infty, +\infty) (the whole real line) is often called simply a continuous function; one also says that such a function is continuous everywhere. For example, all polynomial functions are continuous everywhere.
A function is continuous on a semi-open or a closed interval; if the interval is contained in the domain of the function, the function is continuous at every interior point of the interval, and the value of the function at each endpoint that belongs to the interval is the limit of the values of the function when the variable tends to the endpoint from the interior of the interval. For example, the function f(x) = \sqrt{x} is continuous on its whole domain, which is the closed interval [0,+\infty).
Many commonly encountered functions are partial functions that have a domain formed by all real numbers, except some isolated points. Examples include the reciprocal function x \mapsto \frac {1}{x} and the tangent function x\mapsto \tan x. When they are continuous on their domain, one says, in some contexts, that they are continuous, although they are not continuous everywhere. In other contexts, mainly when one is interested in their behavior near the exceptional points, one says they are discontinuous.
A partial function is discontinuous at a point if the point belongs to the topological closure of its domain, and either the point does not belong to the domain of the function or the function is not continuous at the point. For example, the functions x\mapsto \frac {1}{x} and x\mapsto \sin(\frac {1}{x}) are discontinuous at , and remain discontinuous whichever value is chosen for defining them at . A point where a function is discontinuous is called a discontinuity.
Using mathematical notation, several ways exist to define continuous functions in the three senses mentioned above.
Let f : D \to \R be a function defined on a subset D of the set \R of real numbers.
This subset D is the domain of . Some possible choices include
D = \R : i.e., D is the whole set of real numbers. or, for and real numbers,
D = [a, b] = \{x \in \R \mid a \leq x \leq b \} : D is a closed interval, or
D = (a, b) = \{x \in \R \mid a < x < b \} : D is an open interval.
In the case of the domain D being defined as an open interval, a and b do not belong to D, and the values of f(a) and f(b) do not matter for continuity on D.
====Definition in terms of limits of functions====
The function is continuous at some point of its domain if the limit of f(x), as x approaches c through the domain of f, exists and is equal to f(c). In mathematical notation, this is written as
\lim_{x \to c}{f(x)} = f(c).
In detail this means three conditions: first, has to be defined at (guaranteed by the requirement that is in the domain of ). Second, the limit of that equation has to exist. Third, the value of this limit must equal f(c).
(Here, we have assumed that the domain of f does not have any isolated points.)
====Definition in terms of neighborhoods====
A neighborhood of a point c is a set that contains, at least, all points within some fixed distance of c. Intuitively, a function is continuous at a point c if the range of f over the neighborhood of c shrinks to a single point f(c) as the width of the neighborhood around c shrinks to zero. More precisely, a function f is continuous at a point c of its domain if, for any neighborhood N_1(f(c)) there is a neighborhood N_2(c) in its domain such that f(x) \in N_1(f(c)) whenever x\in N_2(c).
As neighborhoods are defined in any topological space, this definition of a continuous function applies not only for real functions but also when the domain and the codomain are topological spaces and is thus the most general definition. It follows that a function is automatically continuous at every isolated point of its domain. For example, every real-valued function on the integers is continuous.
====Definition in terms of limits of sequences====
One can instead require that for any sequence (x_n)_{n \in \N} of points in the domain which converges to c, the corresponding sequence \left(f(x_n)\right)_{n\in \N} converges to f(c). In mathematical notation, \forall (x_n)_{n \in \N} \subset D:\lim_{n\to\infty} x_n = c \Rightarrow \lim_{n\to\infty} f(x_n) = f(c)\,.
====Weierstrass and Jordan definitions (epsilon–delta) of continuous functions====
Explicitly including the definition of the limit of a function, we obtain a self-contained definition: Given a function f : D \to \mathbb{R} as above and an element x_0 of the domain D, f is said to be continuous at the point x_0 when the following holds: For any positive real number \varepsilon > 0, however small, there exists some positive real number \delta > 0 such that for all x in the domain of f with x_0 - \delta < x < x_0 + \delta, the value of f(x) satisfies
f\left(x_0\right) - \varepsilon < f(x) < f(x_0) + \varepsilon.
Alternatively written, continuity of f : D \to \mathbb{R} at x_0 \in D means that for every \varepsilon > 0, there exists a \delta > 0 such that for all x \in D:
\left|x - x_0\right| < \delta ~~\text{ implies }~~ |f(x) - f(x_0)| < \varepsilon.
More intuitively, we can say that if we want to get all the f(x) values to stay in some small neighborhood around f\left(x_0\right), we need to choose a small enough neighborhood for the x values around x_0. If we can do that no matter how small the f(x_0) neighborhood is, then f is continuous at x_0.
In modern terms, this is generalized by the definition of continuity of a function with respect to a basis for the topology, here the metric topology.
Weierstrass had required that the interval x_0 - \delta < x < x_0 + \delta be entirely within the domain D, but Jordan removed that restriction.
====Definition in terms of control of the remainder====
In proofs and numerical analysis, we often need to know how fast limits are converging, or in other words, control of the remainder. We can formalize this to a definition of continuity.
A function C: [0,\infty) \to [0,\infty] is called a control function if
C is non-decreasing
\inf_{\delta > 0} C(\delta) = 0
A function f : D \to R is C-continuous at x_0 if there exists such a neighbourhood N(x_0) that
|f(x) - f(x_0)| \leq C\left(\left|x - x_0\right|\right) \text{ for all } x \in D \cap N(x_0)
A function is continuous in x_0 if it is C-continuous for some control function C.
This approach leads naturally to refining the notion of continuity by restricting the set of admissible control functions. For a given set of control functions \mathcal{C} a function is if it is for some C \in \mathcal{C}. For example, the Lipschitz, the Hölder continuous functions of exponent and the uniformly continuous functions below are defined by the set of control functions
\mathcal{C}_{\mathrm{Lipschitz}} = \{C : C(\delta) = K|\delta| ,\ K > 0\}
\mathcal{C}_{\text{Hölder}-\alpha} = \{C : C(\delta) = K |\delta|^\alpha, \ K > 0\}
\mathcal{C}_{\text{uniform cont.}} = \{C : C(0) = 0 \}
respectively.
====Definition using oscillation====
Continuity can also be defined in terms of oscillation: a function f is continuous at a point x_0 if and only if its oscillation at that point is zero; in symbols, \omega_f(x_0) = 0. A benefit of this definition is that it discontinuity: the oscillation gives how the function is discontinuous at a point.
This definition is helpful in descriptive set theory to study the set of discontinuities and continuous points – the continuous points are the intersection of the sets where the oscillation is less than \varepsilon (hence a G_{\delta} set) – and gives a rapid proof of one direction of the Lebesgue integrability condition.
The oscillation is equivalent to the \varepsilon-\delta definition by a simple re-arrangement and by using a limit (lim sup, lim inf) to define oscillation: if (at a given point) for a given \varepsilon_0 there is no \delta that satisfies the \varepsilon-\delta definition, then the oscillation is at least \varepsilon_0, and conversely if for every \varepsilon there is a desired \delta, the oscillation is 0. The oscillation definition can be naturally generalized to maps from a topological space to a metric space.
====Definition using the hyperreals====
Cauchy defined the continuity of a function in the following intuitive terms: an infinitesimal change in the independent variable corresponds to an infinitesimal change of the dependent variable (see Cours d'analyse, page 34). Non-standard analysis is a way of making this mathematically rigorous. The real line is augmented by adding infinite and infinitesimal numbers to form the hyperreal numbers. In nonstandard analysis, continuity can be defined as follows.
(see microcontinuity). In other words, an infinitesimal increment of the independent variable always produces an infinitesimal change of the dependent variable, giving a modern expression to Augustin-Louis Cauchy's definition of continuity.
===Construction of continuous functions===
Checking the continuity of a given function can be simplified by checking one of the above defining properties for the building blocks of the given function. It is straightforward to show that the sum of two functions, continuous on some domain, is also continuous on this domain. Given
f, g \colon D \to \R,
then the
s = f + g
(defined by s(x) = f(x) + g(x) for all x\in D) is continuous in D.
The same holds for the ,
p = f \cdot g
(defined by p(x) = f(x) \cdot g(x) for all x \in D)
is continuous in D.
Combining the above preservations of continuity and the continuity of constant functions and of the identity function I(x) = x one arrives at the continuity of all polynomial functions such as
f(x) = x^3 + x^2 - 5 x + 3
(pictured on the right).
In the same way, it can be shown that the
r = 1/f
(defined by r(x) = 1/f(x) for all x \in D such that f(x) \neq 0)
is continuous in D\setminus \{x : f(x) = 0\}.
This implies that, excluding the roots of g, the
q = f / g
(defined by q(x) = f(x)/g(x) for all x \in D, such that g(x) \neq 0)
is also continuous on D\setminus \{x:g(x) = 0\}.
For example, the function (pictured)
y(x) = \frac{2x-1}{x+2}
is defined for all real numbers x \neq -2 and is continuous at every such point. Thus, it is a continuous function. The question of continuity at x = -2 does not arise since x = -2 is not in the domain of y. There is no continuous function F : \R \to \R that agrees with y(x) for all x \neq -2.
Since the function sine is continuous on all reals, the sinc function G(x) = \sin(x)/x, is defined and continuous for all real x \neq 0. However, unlike the previous example, G be extended to a continuous function on real numbers, by the value G(0) to be 1, which is the limit of G(x), when x approaches 0, i.e.,
G(0) = \lim_{x\to 0} \frac{\sin x}{x} = 1.
Thus, by setting
G(x) =
\begin{cases}
\frac {\sin (x)}x & \text{ if }x \ne 0\\
1 & \text{ if }x = 0,
\end{cases}
the sinc-function becomes a continuous function on all real numbers. The term is used in such cases when (re)defining values of a function to coincide with the appropriate limits make a function continuous at specific points.
A more involved construction of continuous functions is the function composition. Given two continuous functions
g : D_g \subseteq \R \to R_g \subseteq \R \quad \text{ and } \quad f : D_f \subseteq \R \to R_f \subseteq D_g,
their composition, denoted as
c = g \circ f : D_f \to \R, and defined by c(x) = g(f(x)), is continuous.
This construction allows stating, for example, that
e^{\sin(\ln x)}
is continuous for all x > 0.
===Examples of discontinuous functions===
An example of a discontinuous function is the Heaviside step function H, defined by
H(x) = \begin{cases}
1 & \text{ if } x \ge 0\\
0 & \text{ if } x < 0
\end{cases}
Pick for instance \varepsilon = 1/2. Then there is no around x = 0, i.e. no open interval (-\delta,\;\delta) with \delta > 0, that will force all the H(x) values to be within the of H(0), i.e. within (1/2,\;3/2). Intuitively, we can think of this type of discontinuity as a sudden jump in function values.
Similarly, the signum or sign function
\sgn(x) = \begin{cases}
\;\;\ 1 & \text{ if }x > 0\\
\;\;\ 0 & \text{ if }x = 0\\
-1 & \text{ if }x < 0
\end{cases}
is discontinuous at x = 0 but continuous everywhere else. Yet another example: the function
f(x) = \begin{cases}
\sin\left(x^{-2}\right)&\text{ if }x \neq 0\\
0&\text{ if }x = 0
\end{cases}
is continuous everywhere apart from x = 0.
Besides plausible continuities and discontinuities like above, there are also functions with a behavior, often coined pathological, for example, Thomae's function,
f(x)=\begin{cases}
1 &\text{ if } x=0\\
\frac{1}{q}&\text{ if } x = \frac{p}{q} \text{(in lowest terms) is a rational number}\\
0&\text{ if }x\text{ is irrational}.
\end{cases}
is continuous at all irrational numbers and discontinuous at all rational numbers. In a similar vein, Dirichlet's function, the indicator function for the set of rational numbers,
D(x)=\begin{cases}
0&\text{ if }x\text{ is irrational } (\in \R \setminus \Q)\\
1&\text{ if }x\text{ is rational } (\in \Q)
\end{cases}
is nowhere continuous.
===Properties===
====A useful lemma====
Let f(x) be a function that is continuous at a point x_0, and y_0 be a value such f\left(x_0\right)\neq y_0. Then f(x)\neq y_0 throughout some neighbourhood of x_0.
Proof: By the definition of continuity, take \varepsilon =\frac{2}>0 , then there exists \delta>0 such that
\left|f(x)-f(x_0)\right| < \frac{\left|y_0 - f(x_0)\right|}{2} \quad \text{ whenever } \quad |x-x_0| < \delta
Suppose there is a point in the neighbourhood |x-x_0|<\delta for which f(x)=y_0; then we have the contradiction
\left|f(x_0)-y_0\right| < \frac{\left|f(x_0) - y_0\right|}{2}.
====Intermediate value theorem====
The intermediate value theorem is an existence theorem, based on the real number property of completeness, and states:
If the real-valued function f is continuous on the closed interval [a, b], and k is some number between f(a) and f(b), then there is some number c \in [a, b], such that f(c) = k.
For example, if a child grows from 1 m to 1.5 m between the ages of two and six years, then, at some time between two and six years of age, the child's height must have been 1.25 m.
As a consequence, if f is continuous on [a, b] and f(a) and f(b) differ in sign, then, at some point c \in [a, b], f(c) must equal zero.
====Extreme value theorem====
The extreme value theorem states that if a function f is defined on a closed interval [a, b] (or any closed and bounded set) and is continuous there, then the function attains its maximum, i.e. there exists c \in [a, b] with f(c) \geq f(x) for all x \in [a, b]. The same is true of the minimum of f. These statements are not, in general, true if the function is defined on an open interval (a, b) (or any set that is not both closed and bounded), as, for example, the continuous function f(x) = \frac{1}{x}, defined on the open interval (0,1), does not attain a maximum, being unbounded above.
====Relation to differentiability and integrability====
Every differentiable function
f : (a, b) \to \R
is continuous, as can be shown. The converse does not hold: for example, the absolute value function
f(x)=|x| = \begin{cases}
\;\;\ x & \text{ if }x \geq 0\\
-x & \text{ if }x < 0
\end{cases}
is everywhere continuous. However, it is not differentiable at x = 0 (but is so everywhere else). Weierstrass's function is also everywhere continuous but nowhere differentiable.
The derivative f′(x) of a differentiable function f(x) need not be continuous. If f′(x) is continuous, f(x) is said to be continuously differentiable. The set of such functions is denoted C^1((a, b)). More generally, the set of functions
f : \Omega \to \R
(from an open interval (or open subset of \R) \Omega to the reals) such that f is n times differentiable and such that the n-th derivative of f is continuous is denoted C^n(\Omega). See differentiability class. In the field of computer graphics, properties related (but not identical) to C^0, C^1, C^2 are sometimes called G^0 (continuity of position), G^1 (continuity of tangency), and G^2 (continuity of curvature); see Smoothness of curves and surfaces.
Every continuous function
f : [a, b] \to \R
is integrable (for example in the sense of the Riemann integral). The converse does not hold, as the (integrable but discontinuous) sign function shows.
====Pointwise and uniform limits====
Given a sequence
f_1, f_2, \dotsc : I \to \R
of functions such that the limit
f(x) := \lim_{n \to \infty} f_n(x)
exists for all x \in D,, the resulting function f(x) is referred to as the pointwise limit of the sequence of functions \left(f_n\right)_{n \in N}. The pointwise limit function need not be continuous, even if all functions f_n are continuous, as the animation at the right shows. However, f is continuous if all functions f_n are continuous and the sequence converges uniformly, by the uniform convergence theorem. This theorem can be used to show that the exponential functions, logarithms, square root function, and trigonometric functions are continuous.
===Directional Continuity===
Image:Right-continuous.svg|A right-continuous function
Image:Left-continuous.svg|A left-continuous function
Discontinuous functions may be discontinuous in a restricted way, giving rise to the concept of directional continuity (or right and left continuous functions) and semi-continuity. Roughly speaking, a function is if no jump occurs when the limit point is approached from the right. Formally, f is said to be right-continuous at the point c if the following holds: For any number \varepsilon > 0 however small, there exists some number \delta > 0 such that for all x in the domain with c < x < c + \delta, the value of f(x) will satisfy
|f(x) - f(c)| < \varepsilon.
This is the same condition as continuous functions, except it is required to hold for x strictly larger than c only. Requiring it instead for all x with c - \delta < x < c yields the notion of functions. A function is continuous if and only if it is both right-continuous and left-continuous.
=== Semicontinuity===
A function f is if, roughly, any jumps that might occur only go down, but not up. That is, for any \varepsilon > 0, there exists some number \delta > 0 such that for all x in the domain with |x - c| < \delta, the value of f(x) satisfies
f(x) \geq f(c) - \epsilon.
The reverse condition is .
==Continuous functions between metric spaces==
The concept of continuous real-valued functions can be generalized to functions between metric spaces. A metric space is a set X equipped with a function (called metric) d_X, that can be thought of as a measurement of the distance of any two elements in X. Formally, the metric is a function
d_X : X \times X \to \R
that satisfies a number of requirements, notably the triangle inequality. Given two metric spaces \left(X, d_X\right) and \left(Y, d_Y\right) and a function
f : X \to Y
then f is continuous at the point c \in X (with respect to the given metrics) if for any positive real number \varepsilon > 0, there exists a positive real number \delta > 0 such that all x \in X satisfying d_X(x, c) < \delta will also satisfy d_Y(f(x), f(c)) < \varepsilon. As in the case of real functions above, this is equivalent to the condition that for every sequence \left(x_n\right) in X with limit \lim x_n = c, we have \lim f\left(x_n\right) = f(c). The latter condition can be weakened as follows: f is continuous at the point c if and only if for every convergent sequence \left(x_n\right) in X with limit c, the sequence \left(f\left(x_n\right)\right) is a Cauchy sequence, and c is in the domain of f.
The set of points at which a function between metric spaces is continuous is a G_{\delta} set – this follows from the \varepsilon-\delta definition of continuity.
This notion of continuity is applied, for example, in functional analysis. A key statement in this area says that a linear operator
T : V \to W
between normed vector spaces V and W (which are vector spaces equipped with a compatible norm, denoted \|x\|) is continuous if and only if it is bounded, that is, there is a constant K such that
\|T(x)\| \leq K \|x\|
for all x \in V.
===Uniform, Hölder and Lipschitz continuity===
The concept of continuity for functions between metric spaces can be strengthened in various ways by limiting the way \delta depends on \varepsilon and c in the definition above. Intuitively, a function f as above is uniformly continuous if the \delta does
not depend on the point c. More precisely, it is required that for every real number \varepsilon > 0 there exists \delta > 0 such that for every c, b \in X with d_X(b, c) < \delta, we have that d_Y(f(b), f(c)) < \varepsilon. Thus, any uniformly continuous function is continuous. The converse does not generally hold but holds when the domain space X is compact. Uniformly continuous maps can be defined in the more general situation of uniform spaces.
A function is Hölder continuous with exponent α (a real number) if there is a constant K such that for all b, c \in X, the inequality
d_Y (f(b), f(c)) \leq K \cdot (d_X (b, c))^\alpha
holds. Any Hölder continuous function is uniformly continuous. The particular case \alpha = 1 is referred to as Lipschitz continuity. That is, a function is Lipschitz continuous if there is a constant K such that the inequality
d_Y (f(b), f(c)) \leq K \cdot d_X (b, c)
holds for any b, c \in X. The Lipschitz condition occurs, for example, in the Picard–Lindelöf theorem concerning the solutions of ordinary differential equations.
==Continuous functions between topological spaces==
Another, more abstract, notion of continuity is the continuity of functions between topological spaces in which there generally is no formal notion of distance, as there is in the case of metric spaces. A topological space is a set X together with a topology on X, which is a set of subsets of X satisfying a few requirements with respect to their unions and intersections that generalize the properties of the open balls in metric spaces while still allowing one to talk about the neighborhoods of a given point. The elements of a topology are called open subsets of X (with respect to the topology).
A function
f : X \to Y
between two topological spaces X and Y is continuous if for every open set V \subseteq Y, the inverse image
f^{-1}(V) = \{x \in X \; | \; f(x) \in V \}
is an open subset of X. That is, f is a function between the sets X and Y (not on the elements of the topology T_X), but the continuity of f depends on the topologies used on X and Y.
This is equivalent to the condition that the preimages of the closed sets (which are the complements of the open subsets) in Y are closed in X.
An extreme example: if a set X is given the discrete topology (in which every subset is open), all functions
f : X \to T
to any topological space T are continuous. On the other hand, if X is equipped with the indiscrete topology (in which the only open subsets are the empty set and X) and the space T set is at least T0, then the only continuous functions are the constant functions. Conversely, any function whose codomain is indiscrete is continuous.
=== Continuity at a point ===
The translation in the language of neighborhoods of the (\varepsilon, \delta)-definition of continuity leads to the following definition of the continuity at a point:
This definition is equivalent to the same statement with neighborhoods restricted to open neighborhoods and can be restated in several ways by using preimages rather than images.
Also, as every set that contains a neighborhood is also a neighborhood, and f^{-1}(V) is the largest subset of such that f(U) \subseteq V, this definition may be simplified into:
As an open set is a set that is a neighborhood of all its points, a function f : X \to Y is continuous at every point of if and only if it is a continuous function.
If X and Y are metric spaces, it is equivalent to consider the neighborhood system of open balls centered at x and f(x) instead of all neighborhoods. This gives back the above \varepsilon-\delta definition of continuity in the context of metric spaces. In general topological spaces, there is no notion of nearness or distance. If, however, the target space is a Hausdorff space, it is still true that f is continuous at a if and only if the limit of f as x approaches a is f(a). At an isolated point, every function is continuous.
Given x \in X, a map f : X \to Y is continuous at x if and only if whenever \mathcal{B} is a filter on X that converges to x in X, which is expressed by writing \mathcal{B} \to x, then necessarily f(\mathcal{B}) \to f(x) in Y.
If \mathcal{N}(x) denotes the neighborhood filter at x then f : X \to Y is continuous at x if and only if f(\mathcal{N}(x)) \to f(x) in Y. Moreover, this happens if and only if the prefilter f(\mathcal{N}(x)) is a filter base for the neighborhood filter of f(x) in Y.
=== Alternative definitions ===
Several equivalent definitions for a topological structure exist; thus, several equivalent ways exist to define a continuous function.
==== Sequences and nets ====
In several contexts, the topology of a space is conveniently specified in terms of limit points. This is often accomplished by specifying when a point is the limit of a sequence. Still, for some spaces that are too large in some sense, one specifies also when a point is the limit of more general sets of points indexed by a directed set, known as nets. A function is (Heine-)continuous only if it takes limits of sequences to limits of sequences. In the former case, preservation of limits is also sufficient; in the latter, a function may preserve all limits of sequences yet still fail to be continuous, and preservation of nets is a necessary and sufficient condition.
In detail, a function f : X \to Y is sequentially continuous if whenever a sequence \left(x_n\right) in X converges to a limit x, the sequence \left(f\left(x_n\right)\right) converges to f(x). Thus, sequentially continuous functions "preserve sequential limits." Every continuous function is sequentially continuous. If X is a first-countable space and countable choice holds, then the converse also holds: any function preserving sequential limits is continuous. In particular, if X is a metric space, sequential continuity and continuity are equivalent. For non-first-countable spaces, sequential continuity might be strictly weaker than continuity. (The spaces for which the two properties are equivalent are called sequential spaces.) This motivates the consideration of nets instead of sequences in general topological spaces. Continuous functions preserve the limits of nets, and this property characterizes continuous functions.
For instance, consider the case of real-valued functions of one real variable:
Proof. Assume that f : A \subseteq \R \to \R is continuous at x_0 (in the sense of \epsilon-\delta continuity). Let \left(x_n\right)_{n\geq1} be a sequence converging at x_0 (such a sequence always exists, for example, x_n = x, \text{ for all } n); since f is continuous at x_0
\forall \epsilon > 0\, \exists \delta_{\epsilon} > 0 : 0 < |x-x_0| < \delta_{\epsilon} \implies |f(x)-f(x_0)| < \epsilon.\quad (*)
For any such \delta_{\epsilon} we can find a natural number \nu_{\epsilon} > 0 such that for all n > \nu_{\epsilon},
|x_n-x_0| < \delta_{\epsilon},
since \left(x_n\right) converges at x_0; combining this with (*) we obtain
\forall \epsilon > 0 \,\exists \nu_{\epsilon} > 0 : \forall n > \nu_{\epsilon} \quad |f(x_n)-f(x_0)| < \epsilon.
Assume on the contrary that f is sequentially continuous and proceed by contradiction: suppose f is not continuous at x_0
\exists \epsilon > 0 : \forall \delta_{\epsilon} > 0,\,\exists x_{\delta_{\epsilon}}: 0 < |x_{\delta_{\epsilon}}-x_0| < \delta_\epsilon \implies |f(x_{\delta_{\epsilon}})-f(x_0)| > \epsilon
then we can take \delta_{\epsilon}=1/n,\,\forall n > 0 and call the corresponding point x_{\delta_{\epsilon}} =: x_n: in this way we have defined a sequence (x_n)_{n\geq1} such that
\forall n > 0 \quad |x_n-x_0| < \frac{1}{n},\quad |f(x_n)-f(x_0)| > \epsilon
by construction x_n \to x_0 but f(x_n) \not\to f(x_0), which contradicts the hypothesis of sequential continuity. \blacksquare
==== Closure operator and interior operator definitions ====
In terms of the interior operator, a function f : X \to Y between topological spaces is continuous if and only if for every subset B \subseteq Y,
f^{-1}\left(\operatorname{int}_Y B\right) ~\subseteq~ \operatorname{int}_X\left(f^{-1}(B)\right).
In terms of the closure operator, f : X \to Y is continuous if and only if for every subset A \subseteq X,
f\left(\operatorname{cl}_X A\right) ~\subseteq~ \operatorname{cl}_Y (f(A)).
That is to say, given any element x \in X that belongs to the closure of a subset A \subseteq X, f(x) necessarily belongs to the closure of f(A) in Y. If we declare that a point x is a subset A \subseteq X if x \in \operatorname{cl}_X A, then this terminology allows for a plain English description of continuity: f is continuous if and only if for every subset A \subseteq X, f maps points that are close to A to points that are close to f(A). Similarly, f is continuous at a fixed given point x \in X if and only if whenever x is close to a subset A \subseteq X, then f(x) is close to f(A).
Instead of specifying topological spaces by their open subsets, any topology on X can alternatively be determined by a closure operator or by an interior operator.
Specifically, the map that sends a subset A of a topological space X to its topological closure \operatorname{cl}_X A satisfies the Kuratowski closure axioms. Conversely, for any closure operator A \mapsto \operatorname{cl} A there exists a unique topology \tau on X (specifically, \tau := \{ X \setminus \operatorname{cl} A : A \subseteq X \}) such that for every subset A \subseteq X, \operatorname{cl} A is equal to the topological closure \operatorname{cl}_{(X, \tau)} A of A in (X, \tau). If the sets X and Y are each associated with closure operators (both denoted by \operatorname{cl}) then a map f : X \to Y is continuous if and only if f(\operatorname{cl} A) \subseteq \operatorname{cl} (f(A)) for every subset A \subseteq X.
Similarly, the map that sends a subset A of X to its topological interior \operatorname{int}_X A defines an interior operator. Conversely, any interior operator A \mapsto \operatorname{int} A induces a unique topology \tau on X (specifically, \tau := \{ \operatorname{int} A : A \subseteq X \}) such that for every A \subseteq X, \operatorname{int} A is equal to the topological interior \operatorname{int}_{(X, \tau)} A of A in (X, \tau). If the sets X and Y are each associated with interior operators (both denoted by \operatorname{int}) then a map f : X \to Y is continuous if and only if f^{-1}(\operatorname{int} B) \subseteq \operatorname{int}\left(f^{-1}(B)\right) for every subset B \subseteq Y.
==== Filters and prefilters ====
Continuity can also be characterized in terms of filters. A function f : X \to Y is continuous if and only if whenever a filter \mathcal{B} on X converges in X to a point x \in X, then the prefilter f(\mathcal{B}) converges in Y to f(x). This characterization remains true if the word "filter" is replaced by "prefilter."
===Properties===
If f : X \to Y and g : Y \to Z are continuous, then so is the composition g \circ f : X \to Z. If f : X \to Y is continuous and
X is compact, then f(X) is compact.
X is connected, then f(X) is connected.
X is path-connected, then f(X) is path-connected.
X is Lindelöf, then f(X) is Lindelöf.
X is separable, then f(X) is separable.
The possible topologies on a fixed set X are partially ordered: a topology \tau_1 is said to be coarser than another topology \tau_2 (notation: \tau_1 \subseteq \tau_2) if every open subset with respect to \tau_1 is also open with respect to \tau_2. Then, the identity map
\operatorname{id}_X : \left(X, \tau_2\right) \to \left(X, \tau_1\right)
is continuous if and only if \tau_1 \subseteq \tau_2 (see also comparison of topologies). More generally, a continuous function
\left(X, \tau_X\right) \to \left(Y, \tau_Y\right)
stays continuous if the topology \tau_Y is replaced by a coarser topology and/or \tau_X is replaced by a finer topology.
===Homeomorphisms===
Symmetric to the concept of a continuous map is an open map, for which of open sets are open. If an open map f has an inverse function, that inverse is continuous, and if a continuous map g has an inverse, that inverse is open. Given a bijective function f between two topological spaces, the inverse function f^{-1} need not be continuous. A bijective continuous function with a continuous inverse function is called a .
If a continuous bijection has as its domain a compact space and its codomain is Hausdorff, then it is a homeomorphism.
===Defining topologies via continuous functions===
Given a function
f : X \to S,
where X is a topological space and S is a set (without a specified topology), the final topology on S is defined by letting the open sets of S be those subsets A of S for which f^{-1}(A) is open in X. If S has an existing topology, f is continuous with respect to this topology if and only if the existing topology is coarser than the final topology on S. Thus, the final topology is the finest topology on S that makes f continuous. If f is surjective, this topology is canonically identified with the quotient topology under the equivalence relation defined by f.
Dually, for a function f from a set S to a topological space X, the initial topology on S is defined by designating as an open set every subset A of S such that A = f^{-1}(U) for some open subset U of X. If S has an existing topology, f is continuous with respect to this topology if and only if the existing topology is finer than the initial topology on S. Thus, the initial topology is the coarsest topology on S that makes f continuous. If f is injective, this topology is canonically identified with the subspace topology of S, viewed as a subset of X.
A topology on a set S is uniquely determined by the class of all continuous functions S \to X into all topological spaces X. Dually, a similar idea can be applied to maps X \to S.
==Related notions==
If f : S \to Y is a continuous function from some subset S of a topological space X then a of f to X is any continuous function F : X \to Y such that F(s) = f(s) for every s \in S, which is a condition that often written as f = F\big\vert_S. In words, it is any continuous function F : X \to Y that restricts to f on S. This notion is used, for example, in the Tietze extension theorem and the Hahn–Banach theorem. If f : S \to Y is not continuous, then it could not possibly have a continuous extension. If Y is a Hausdorff space and S is a dense subset of X then a continuous extension of f : S \to Y to X, if one exists, will be unique. The Blumberg theorem states that if f : \R \to \R is an arbitrary function then there exists a dense subset D of \R such that the restriction f\big\vert_D : D \to \R is continuous; in other words, every function \R \to \R can be restricted to some dense subset on which it is continuous.
Various other mathematical domains use the concept of continuity in different but related meanings. For example, in order theory, an order-preserving function f : X \to Y between particular types of partially ordered sets X and Y is continuous if for each directed subset A of X, we have \sup f(A) = f(\sup A). Here \,\sup\, is the supremum with respect to the orderings in X and Y, respectively. This notion of continuity is the same as topological continuity when the partially ordered sets are given the Scott topology.
In category theory, a functor
F : \mathcal C \to \mathcal D
between two categories is called if it commutes with small limits. That is to say,
\varprojlim_{i \in I} F(C_i) \cong F \left(\varprojlim_{i \in I} C_i \right)
for any small (that is, indexed by a set I, as opposed to a class) diagram of objects in \mathcal C.
A is a generalization of metric spaces and posets, which uses the concept of quantales, and that can be used to unify the notions of metric spaces and domains.
In measure theory, a function f : E \to \mathbb{R}^k defined on a Lebesgue measurable set E \subseteq \mathbb{R}^n is called approximately continuous at a point x_0 \in E if the approximate limit of f at x_0 exists and equals f(x_0). This generalizes the notion of continuity by replacing the ordinary limit with the approximate limit. A fundamental result known as the Stepanov-Denjoy theorem states that a function is measurable if and only if it is approximately continuous almost everywhere.
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6,123 |
Curl (mathematics)
|
In vector calculus, the curl, also known as rotor, is a vector operator that describes the infinitesimal circulation of a vector field in three-dimensional Euclidean space. The curl at a point in the field is represented by a vector whose length and direction denote the magnitude and axis of the maximum circulation. which also reveals the relation between curl (rotor), divergence, and gradient operators.
Unlike the gradient and divergence, curl as formulated in vector calculus does not generalize simply to other dimensions; some generalizations are possible, but only in three dimensions is the geometrically defined curl of a vector field again a vector field. This deficiency is a direct consequence of the limitations of vector calculus; on the other hand, when expressed as an antisymmetric tensor field via the wedge operator of geometric calculus, the curl generalizes to all dimensions. The circumstance is similar to that attending the 3-dimensional cross product, and indeed the connection is reflected in the notation \nabla \times for the curl.
The name "curl" was first suggested by James Clerk Maxwell in 1871 but the concept was apparently first used in the construction of an optical field theory by James MacCullagh in 1839.
==Definition==
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and the fingers curl along the orientation of
| align =
| direction =
| alt1 =
| header = Right-hand rule
}}
The curl of a vector field , denoted by , or \nabla \times \mathbf{F}, or , is an operator that maps functions in to functions in , and in particular, it maps continuously differentiable functions to continuous functions . It can be defined in several ways, to be mentioned below:
One way to define the curl of a vector field at a point is implicitly through its components along various axes passing through the point: if \mathbf{\hat{u}} is any unit vector, the component of the curl of along the direction \mathbf{\hat{u}} may be defined to be the limiting value of a closed line integral in a plane perpendicular to \mathbf{\hat{u}} divided by the area enclosed, as the path of integration is contracted indefinitely around the point.
More specifically, the curl is defined at a point as
(\nabla \times \mathbf{F})(p)\cdot \mathbf{\hat{u}} \ \overset{\underset{\mathrm{def}}{}} \lim_{A \to 0}\frac{1}\oint_{C(p)} \mathbf{F} \cdot \mathrm{d}\mathbf{r}
where the line integral is calculated along the boundary of the area containing point p, being the magnitude of the area. This equation defines the component of the curl of along the direction \mathbf{\hat{u}}. The infinitesimal surfaces bounded by have \mathbf{\hat{u}} as their normal. is oriented via the right-hand rule.
The above formula means that the component of the curl of a vector field along a certain axis is the infinitesimal area density of the circulation of the field in a plane perpendicular to that axis. This formula does not a priori define a legitimate vector field, for the individual circulation densities with respect to various axes a priori need not relate to each other in the same way as the components of a vector do; that they do indeed relate to each other in this precise manner must be proven separately.
To this definition fits naturally the Kelvin–Stokes theorem, as a global formula corresponding to the definition. It equates the surface integral of the curl of a vector field to the above line integral taken around the boundary of the surface.
Another way one can define the curl vector of a function at a point is explicitly as the limiting value of a vector-valued surface integral around a shell enclosing divided by the volume enclosed, as the shell is contracted indefinitely around .
More specifically, the curl may be defined by the vector formula
(\nabla \times \mathbf{F})(p) \overset{\underset{\mathrm{def}}{}} \lim_{V \to 0}\frac{1}\oint_S \mathbf{\hat{n}} \times \mathbf{F} \ \mathrm{d}S
where the surface integral is calculated along the boundary of the volume , being the magnitude of the volume, and \mathbf{\hat{n}} pointing outward from the surface perpendicularly at every point in .
In this formula, the cross product in the integrand measures the tangential component of at each point on the surface , and points along the surface at right angles to the tangential projection of . Integrating this cross product over the whole surface results in a vector whose magnitude measures the overall circulation of around , and whose direction is at right angles to this circulation. The above formula says that the curl of a vector field at a point is the infinitesimal volume density of this "circulation vector" around the point.
To this definition fits naturally another global formula (similar to the Kelvin-Stokes theorem) which equates the volume integral of the curl of a vector field to the above surface integral taken over the boundary of the volume.
Whereas the above two definitions of the curl are coordinate free, there is another "easy to memorize" definition of the curl in curvilinear orthogonal coordinates, e.g. in Cartesian coordinates, spherical, cylindrical, or even elliptical or parabolic coordinates: \begin{align}
& (\operatorname{curl}\mathbf F)_1=\frac{1}{h_2h_3}\left (\frac{\partial (h_3F_3)}{\partial u_2}-\frac{\partial (h_2F_2)}{\partial u_3}\right ), \\[5pt]
& (\operatorname{curl}\mathbf F)_2=\frac{1}{h_3h_1}\left (\frac{\partial (h_1F_1)}{\partial u_3}-\frac{\partial (h_3F_3)}{\partial u_1}\right ), \\[5pt]
& (\operatorname{curl}\mathbf F)_3=\frac{1}{h_1h_2}\left (\frac{\partial (h_2F_2)}{\partial u_1}-\frac{\partial (h_1F_1)}{\partial u_2}\right ).
\end{align}
The equation for each component can be obtained by exchanging each occurrence of a subscript 1, 2, 3 in cyclic permutation: 1 → 2, 2 → 3, and 3 → 1 (where the subscripts represent the relevant indices).
If are the Cartesian coordinates and are the orthogonal coordinates, then
h_i = \sqrt{\left (\frac{\partial x_1}{\partial u_i} \right )^2 + \left (\frac{\partial x_2}{\partial u_i} \right )^2 + \left (\frac{\partial x_3}{\partial u_i} \right )^2}
is the length of the coordinate vector corresponding to . The remaining two components of curl result from cyclic permutation of indices: 3,1,2 → 1,2,3 → 2,3,1.
== Usage ==
In practice, the two coordinate-free definitions described above are rarely used because in virtually all cases, the curl operator can be applied using some set of curvilinear coordinates, for which simpler representations have been derived.
The notation \nabla\times\mathbf{F} has its origins in the similarities to the 3-dimensional cross product, and it is useful as a mnemonic in Cartesian coordinates if \nabla is taken as a vector differential operator del. Such notation involving operators is common in physics and algebra.
Expanded in 3-dimensional Cartesian coordinates (see Del in cylindrical and spherical coordinates for spherical and cylindrical coordinate representations), \nabla\times\mathbf{F} is, for \mathbf{F} composed of [F_x,F_y,F_z] (where the subscripts indicate the components of the vector, not partial derivatives):
\nabla \times \mathbf{F} =
\begin{vmatrix} \boldsymbol{\hat\imath} & \boldsymbol{\hat\jmath} & \boldsymbol{\hat k} \\[5mu]
{\dfrac{\partial}{\partial x}} & {\dfrac{\partial}{\partial y}} & {\dfrac{\partial}{\partial z}} \\[5mu]
F_x & F_y & F_z \end{vmatrix}
where , , and are the unit vectors for the -, -, and -axes, respectively. This expands as follows:
\nabla \times \mathbf{F} =
\left(\frac{\partial F_z}{\partial y} - \frac{\partial F_y}{\partial z}\right) \boldsymbol{\hat\imath} +
\left(\frac{\partial F_x}{\partial z} - \frac{\partial F_z}{\partial x} \right) \boldsymbol{\hat\jmath} +
\left(\frac{\partial F_y}{\partial x} - \frac{\partial F_x}{\partial y} \right) \boldsymbol{\hat k}
Although expressed in terms of coordinates, the result is invariant under proper rotations of the coordinate axes but the result inverts under reflection.
In a general coordinate system, the curl is given by
(\nabla \times \mathbf{F} )^k = \frac{1}{\sqrt{g}} \varepsilon^{k\ell m} \nabla_\ell F_m
where denotes the Levi-Civita tensor, the covariant derivative, g is the determinant of the metric tensor and the Einstein summation convention implies that repeated indices are summed over. Due to the symmetry of the Christoffel symbols participating in the covariant derivative, this expression reduces to the partial derivative:
(\nabla \times \mathbf{F} ) = \frac{1}{\sqrt{g}} \mathbf{R}_k\varepsilon^{k\ell m} \partial_\ell F_m
where are the local basis vectors. Equivalently, using the exterior derivative, the curl can be expressed as:
\nabla \times \mathbf{F} = \left( \star \big( {\mathrm d} \mathbf{F}^\flat \big) \right)^\sharp
Here and are the musical isomorphisms, and is the Hodge star operator. This formula shows how to calculate the curl of in any coordinate system, and how to extend the curl to any oriented three-dimensional Riemannian manifold. Since this depends on a choice of orientation, curl is a chiral operation. In other words, if the orientation is reversed, then the direction of the curl is also reversed.
==Examples==
=== Example 1 ===
Suppose the vector field describes the velocity field of a fluid flow (such as a large tank of liquid or gas) and a small ball is located within the fluid or gas (the center of the ball being fixed at a certain point). If the ball has a rough surface, the fluid flowing past it will make it rotate. The rotation axis (oriented according to the right hand rule) points in the direction of the curl of the field at the center of the ball, and the angular speed of the rotation is half the magnitude of the curl at this point.
The curl of the vector field at any point is given by the rotation of an infinitesimal area in the xy-plane (for z-axis component of the curl), zx-plane (for y-axis component of the curl) and yz-plane (for x-axis component of the curl vector). This can be seen in the examples below.
=== Example 2 ===
The vector field
\mathbf{F}(x,y,z)=y\boldsymbol{\hat{\imath}}-x\boldsymbol{\hat{\jmath}}
can be decomposed as
F_x =y, F_y = -x, F_z =0.
Upon visual inspection, the field can be described as "rotating". If the vectors of the field were to represent a linear force acting on objects present at that point, and an object were to be placed inside the field, the object would start to rotate clockwise around itself. This is true regardless of where the object is placed.
Calculating the curl:
\nabla \times \mathbf{F} =0\boldsymbol{\hat{\imath}}+0\boldsymbol{\hat{\jmath}}+ \left({\frac{\partial}{\partial x}}(-x) -{\frac{\partial}{\partial y}} y\right)\boldsymbol{\hat{k}}=-2\boldsymbol{\hat{k}}
The resulting vector field describing the curl would at all points be pointing in the negative direction. The results of this equation align with what could have been predicted using the right-hand rule using a right-handed coordinate system. Being a uniform vector field, the object described before would have the same rotational intensity regardless of where it was placed.
=== Example 3 ===
For the vector field
\mathbf{F}(x,y,z) = -x^2\boldsymbol{\hat{\jmath}}
the curl is not as obvious from the graph. However, taking the object in the previous example, and placing it anywhere on the line , the force exerted on the right side would be slightly greater than the force exerted on the left, causing it to rotate clockwise. Using the right-hand rule, it can be predicted that the resulting curl would be straight in the negative direction. Inversely, if placed on , the object would rotate counterclockwise and the right-hand rule would result in a positive direction.
Calculating the curl:
{\nabla} \times \mathbf{F} = 0 \boldsymbol{\hat{\imath}} + 0\boldsymbol{\hat{\jmath}} + {\frac{\partial}{\partial x}}\left(-x^2\right) \boldsymbol{\hat{k}} = -2x\boldsymbol{\hat{k}}.
The curl points in the negative direction when is positive and vice versa. In this field, the intensity of rotation would be greater as the object moves away from the plane .
===Further examples===
In a vector field describing the linear velocities of each part of a rotating disk in uniform circular motion, the curl has the same value at all points, and this value turns out to be exactly two times the vectorial angular velocity of the disk (oriented as usual by the right-hand rule). More generally, for any flowing mass, the linear velocity vector field at each point of the mass flow has a curl (the vorticity of the flow at that point) equal to exactly two times the local vectorial angular velocity of the mass about the point.
For any solid object subject to an external physical force (such as gravity or the electromagnetic force), one may consider the vector field representing the infinitesimal force-per-unit-volume contributions acting at each of the points of the object. This force field may create a net torque on the object about its center of mass, and this torque turns out to be directly proportional and vectorially parallel to the (vector-valued) integral of the curl of the force field over the whole volume.
Of the four Maxwell's equations, two—Faraday's law and Ampère's law—can be compactly expressed using curl. Faraday's law states that the curl of an electric field is equal to the opposite of the time rate of change of the magnetic field, while Ampère's law relates the curl of the magnetic field to the current and the time rate of change of the electric field.
== Identities ==
In general curvilinear coordinates (not only in Cartesian coordinates), the curl of a cross product of vector fields and can be shown to be
\nabla \times \left( \mathbf{v \times F} \right) = \Big( \left( \mathbf{ \nabla \cdot F } \right) + \mathbf{F \cdot \nabla} \Big) \mathbf{v}- \Big( \left( \mathbf{ \nabla \cdot v } \right) + \mathbf{v \cdot \nabla} \Big) \mathbf{F} \ .
Interchanging the vector field and operator, we arrive at the cross product of a vector field with curl of a vector field:
\mathbf{v \ \times } \left( \mathbf{ \nabla \times F} \right) =\nabla_\mathbf{F} \left( \mathbf{v \cdot F } \right) - \left( \mathbf{v \cdot \nabla } \right) \mathbf{F} \ ,
where is the Feynman subscript notation, which considers only the variation due to the vector field (i.e., in this case, is treated as being constant in space).
Another example is the curl of a curl of a vector field. It can be shown that in general coordinates
\nabla \times \left( \mathbf{\nabla \times F} \right) = \mathbf{\nabla}(\mathbf{\nabla \cdot F}) - \nabla^2 \mathbf{F} \ ,
and this identity defines the vector Laplacian of , symbolized as .
The curl of the gradient of any scalar field is always the zero vector field
\nabla \times ( \nabla \varphi ) = \boldsymbol{0}
which follows from the antisymmetry in the definition of the curl, and the symmetry of second derivatives.
The divergence of the curl of any vector field is equal to zero:
\nabla\cdot(\nabla\times\mathbf{F}) = 0.
If is a scalar valued function and is a vector field, then
\nabla \times ( \varphi \mathbf{F}) = \nabla \varphi \times \mathbf{F} + \varphi \nabla \times \mathbf{F}
== Generalizations ==
The vector calculus operations of grad, curl, and div are most easily generalized in the context of differential forms, which involves a number of steps. In short, they correspond to the derivatives of 0-forms, 1-forms, and 2-forms, respectively. The geometric interpretation of curl as rotation corresponds to identifying bivectors (2-vectors) in 3 dimensions with the special orthogonal Lie algebra \mathfrak{so}(3) of infinitesimal rotations (in coordinates, skew-symmetric 3 × 3 matrices), while representing rotations by vectors corresponds to identifying 1-vectors (equivalently, 2-vectors) and these all being 3-dimensional spaces.
=== Differential forms ===
In 3 dimensions, a differential 0-form is a real-valued function f(x,y,z); a differential 1-form is the following expression, where the coefficients are functions:
a_1\,dx + a_2\,dy + a_3\,dz;
a differential 2-form is the formal sum, again with function coefficients:
a_{12}\,dx\wedge dy + a_{13}\,dx\wedge dz + a_{23}\,dy\wedge dz;
and a differential 3-form is defined by a single term with one function as coefficient:
a_{123}\,dx\wedge dy\wedge dz.
(Here the -coefficients are real functions of three variables; the "wedge products", e.g. \text{d}x\wedge\text{d}y, can be interpreted as some kind of oriented area elements, \text{d}x\wedge\text{d}y=-\text{d}y\wedge\text{d}x, etc.)
The exterior derivative of a -form in is defined as the -form from above—and in if, e.g.,
\omega^{(k)}=\sum_{1\leq i_1
then the exterior derivative leads to
d\omega^{(k)}=\sum_{\scriptstyle{j=1} \atop \scriptstyle{i_1<\cdots
The exterior derivative of a 1-form is therefore a 2-form, and that of a 2-form is a 3-form. On the other hand, because of the interchangeability of mixed derivatives,
\frac{\partial^2}{\partial x_i\,\partial x_j} = \frac{\partial^2}{\partial x_j\,\partial x_i} ,
and antisymmetry,
d x_i \wedge d x_j = -d x_j \wedge d x_i
the twofold application of the exterior derivative yields 0 (the zero k+2-form).
Thus, denoting the space of -forms by \Omega^k(\mathbb{R}^3) and the exterior derivative by one gets a sequence:
0 \, \overset{d}{\longrightarrow} \;
\Omega^0\left(\mathbb{R}^3\right) \, \overset{d}{\longrightarrow} \;
\Omega^1\left(\mathbb{R}^3\right) \, \overset{d}{\longrightarrow} \;
\Omega^2\left(\mathbb{R}^3\right) \, \overset{d}{\longrightarrow} \;
\Omega^3\left(\mathbb{R}^3\right) \, \overset{d}{\longrightarrow} \, 0.
Here \Omega^k(\mathbb{R}^n) is the space of sections of the exterior algebra \Lambda^k(\mathbb{R}^n) vector bundle over Rn, whose dimension is the binomial coefficient \binom{n}{k}; note that \Omega^k(\mathbb{R}^3)=0 for k>3 or k. Writing only dimensions, one obtains a row of Pascal's triangle:
0\rightarrow 1\rightarrow 3\rightarrow 3\rightarrow 1\rightarrow 0;
the 1-dimensional fibers correspond to scalar fields, and the 3-dimensional fibers to vector fields, as described below. Modulo suitable identifications, the three nontrivial occurrences of the exterior derivative correspond to grad, curl, and div.
Differential forms and the differential can be defined on any Euclidean space, or indeed any manifold, without any notion of a Riemannian metric. On a Riemannian manifold, or more generally pseudo-Riemannian manifold, -forms can be identified with -vector fields (-forms are -covector fields, and a pseudo-Riemannian metric gives an isomorphism between vectors and covectors), and on an oriented vector space with a nondegenerate form (an isomorphism between vectors and covectors), there is an isomorphism between -vectors and -vectors; in particular on (the tangent space of) an oriented pseudo-Riemannian manifold. Thus on an oriented pseudo-Riemannian manifold, one can interchange -forms, -vector fields, -forms, and -vector fields; this is known as Hodge duality. Concretely, on this is given by:
1-forms and 1-vector fields: the 1-form corresponds to the vector field .
1-forms and 2-forms: one replaces by the dual quantity (i.e., omit ), and likewise, taking care of orientation: corresponds to , and corresponds to . Thus the form corresponds to the "dual form" .
Thus, identifying 0-forms and 3-forms with scalar fields, and 1-forms and 2-forms with vector fields:
grad takes a scalar field (0-form) to a vector field (1-form);
curl takes a vector field (1-form) to a pseudovector field (2-form);
div takes a pseudovector field (2-form) to a pseudoscalar field (3-form)
On the other hand, the fact that corresponds to the identities
\nabla\times(\nabla f) = \mathbf 0
for any scalar field , and
\nabla \cdot (\nabla \times\mathbf v)=0
for any vector field .
Grad and div generalize to all oriented pseudo-Riemannian manifolds, with the same geometric interpretation, because the spaces of 0-forms and -forms at each point are always 1-dimensional and can be identified with scalar fields, while the spaces of 1-forms and -forms are always fiberwise -dimensional and can be identified with vector fields.
Curl does not generalize in this way to 4 or more dimensions (or down to 2 or fewer dimensions); in 4 dimensions the dimensions are
so the curl of a 1-vector field (fiberwise 4-dimensional) is a 2-vector field, which at each point belongs to 6-dimensional vector space, and so one has
\omega^{(2)}=\sum_{i
which yields a sum of six independent terms, and cannot be identified with a 1-vector field. Nor can one meaningfully go from a 1-vector field to a 2-vector field to a 3-vector field (4 → 6 → 4), as taking the differential twice yields zero (). Thus there is no curl function from vector fields to vector fields in other dimensions arising in this way.
However, one can define a curl of a vector field as a 2-vector field in general, as described below.
=== Curl geometrically ===
2-vectors correspond to the exterior power ; in the presence of an inner product, in coordinates these are the skew-symmetric matrices, which are geometrically considered as the special orthogonal Lie algebra of infinitesimal rotations. This has dimensions, and allows one to interpret the differential of a 1-vector field as its infinitesimal rotations. Only in 3 dimensions (or trivially in 0 dimensions) we have , which is the most elegant and common case. In 2 dimensions the curl of a vector field is not a vector field but a function, as 2-dimensional rotations are given by an angle (a scalar – an orientation is required to choose whether one counts clockwise or counterclockwise rotations as positive); this is not the div, but is rather perpendicular to it. In 3 dimensions the curl of a vector field is a vector field as is familiar (in 1 and 0 dimensions the curl of a vector field is 0, because there are no non-trivial 2-vectors), while in 4 dimensions the curl of a vector field is, geometrically, at each point an element of the 6-dimensional Lie algebra
The curl of a 3-dimensional vector field which only depends on 2 coordinates (say and ) is simply a vertical vector field (in the direction) whose magnitude is the curl of the 2-dimensional vector field, as in the examples on this page.
Considering curl as a 2-vector field (an antisymmetric 2-tensor) has been used to generalize vector calculus and associated physics to higher dimensions.
==Inverse==
In the case where the divergence of a vector field is zero, a vector field exists such that . This is why the magnetic field, characterized by zero divergence, can be expressed as the curl of a magnetic vector potential.
If is a vector field with , then adding any gradient vector field to will result in another vector field such that as well. This can be summarized by saying that the inverse curl of a three-dimensional vector field can be obtained up to an unknown irrotational field with the Biot–Savart law.
|
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] |
6,125 |
Carl Friedrich Gauss
|
Johann Carl Friedrich Gauss (; ; ; 30 April 177723 February 1855) was a German mathematician, astronomer, geodesist, and physicist, who contributed to many fields in mathematics and science, and has been called "the prince of mathematics" and "the greatest mathematician who ever lived". He was director of the Göttingen Observatory and professor of astronomy from 1807 until his death in 1855.
While studying at the University of Göttingen, he propounded several mathematical theorems. As an independent scholar, he wrote the masterpieces Disquisitiones Arithmeticae and Theoria motus corporum coelestium. Gauss produced the second and third complete proofs of the fundamental theorem of algebra. In number theory, he made numerous contributions, such as the composition law, the law of quadratic reciprocity and the Fermat polygonal number theorem. He also contributed to the theory of binary and ternary quadratic forms, the construction of the heptadecagon, and the theory of hypergeometric series. Due to Gauss' extensive and fundamental contributions to science and mathematics, more than 100 mathematical and scientific concepts are named after him.
Gauss was instrumental in the identification of Ceres as a dwarf planet. His work on the motion of planetoids disturbed by large planets led to the introduction of the Gaussian gravitational constant and the method of least squares, which he had discovered before Adrien-Marie Legendre published it. Gauss led the geodetic survey of the Kingdom of Hanover together with an arc measurement project from 1820 to 1844; he was one of the founders of geophysics and formulated the fundamental principles of magnetism. His practical work led to the invention of the heliotrope in 1821, a magnetometer in 1833 and – with Wilhelm Eduard Weber – the first electromagnetic telegraph in 1833.
Gauss was the first to discover and study non-Euclidean geometry, which he also named. He developed a fast Fourier transform some 160 years before John Tukey and James Cooley.
Gauss refused to publish incomplete work and left several works to be edited posthumously. He believed that the act of learning, not possession of knowledge, provided the greatest enjoyment. Gauss was not a committed or enthusiastic teacher, generally preferring to focus on his own work. Nevertheless, some of his students, such as Dedekind and Riemann, became well-known and influential mathematicians in their own right.
== Biography ==
=== Youth and education ===
Gauss was born on 30 April 1777 in Brunswick in the Duchy of Brunswick-Wolfenbüttel (now in the German state of Lower Saxony). His family was of relatively low social status. His father Gebhard Dietrich Gauss (1744–1808) worked variously as a butcher, bricklayer, gardener, and treasurer of a death-benefit fund. Gauss characterized his father as honourable and respected, but rough and dominating at home. He was experienced in writing and calculating, whereas his second wife Dorothea, Carl Friedrich's mother, was nearly illiterate. He had one elder brother from his father's first marriage.
Gauss was a child prodigy in mathematics. When the elementary teachers noticed his intellectual abilities, they brought him to the attention of the Duke of Brunswick who sent him to the local Collegium Carolinum, which he attended from 1792 to 1795 with Eberhard August Wilhelm von Zimmermann as one of his teachers. Thereafter the Duke granted him the resources for studies of mathematics, sciences, and classical languages at the University of Göttingen until 1798. His professor in mathematics was Abraham Gotthelf Kästner, whom Gauss called "the leading mathematician among poets, and the leading poet among mathematicians" because of his epigrams. His favorite English author was Walter Scott, his favorite German Jean Paul. At the age of 62, he began to teach himself Russian, very likely to understand scientific writings from Russia, among them those of Lobachevsky on non-Euclidean geometry. Gauss liked singing and went to concerts. He was a busy newspaper reader; in his last years, he would visit an academic press salon of the university every noon. Gauss did not care much for philosophy, and mocked the "splitting hairs of the so-called metaphysicians", by which he meant proponents of the contemporary school of Naturphilosophie.
Gauss had an "aristocratic and through and through conservative nature", with little respect for people's intelligence and morals, following the motto "mundus vult decipi". He disliked Napoleon and his system and was horrified by violence and revolution of all kinds. Thus he condemned the methods of the Revolutions of 1848, though he agreed with some of their aims, such as that of a unified Germany. He had a low estimation of the constitutional system and he criticized parliamentarians of his time for their perceived ignorance and logical errors.
Some Gauss biographers have speculated on his religious beliefs. He sometimes said "God arithmetizes" and "I succeeded – not on account of my hard efforts, but by the grace of the Lord." Gauss was a member of the Lutheran church, like most of the population in northern Germany, but it seems that he did not believe all Lutheran dogma or understand the Bible fully literally. According to Sartorius, Gauss' religious tolerance, "insatiable thirst for truth" and sense of justice were motivated by his religious convictions.
== Mathematics ==
=== Algebra and number theory ===
==== Fundamental theorem of algebra ====
In his doctoral thesis from 1799, Gauss proved the fundamental theorem of algebra which states that every non-constant single-variable polynomial with complex coefficients has at least one complex root. Mathematicians including Jean le Rond d'Alembert had produced false proofs before him, and Gauss's dissertation contains a critique of d'Alembert's work. He subsequently produced three other proofs, the last one in 1849 being generally rigorous. His attempts led to considerable clarification of the concept of complex numbers.
==== Disquisitiones Arithmeticae ====
In the preface to the Disquisitiones, Gauss dates the beginning of his work on number theory to 1795. By studying the works of previous mathematicians like Fermat, Euler, Lagrange, and Legendre, he realized that these scholars had already found much of what he had independently discovered. The Disquisitiones Arithmeticae, written in 1798 and published in 1801, consolidated number theory as a discipline and covered both elementary and algebraic number theory. Therein he introduces the triple bar symbol () for congruence and uses it for a clean presentation of modular arithmetic. It deals with the unique factorization theorem and primitive roots modulo n. In the main sections, Gauss presents the first two proofs of the law of quadratic reciprocity and develops the theories of binary and ternary quadratic forms.
The Disquisitiones include the Gauss composition law for binary quadratic forms, as well as the enumeration of the number of representations of an integer as the sum of three squares. As an almost immediate corollary of his theorem on three squares, he proves the triangular case of the Fermat polygonal number theorem for n = 3. From several analytic results on class numbers that Gauss gives without proof towards the end of the fifth section, it appears that Gauss already knew the class number formula in 1801.
In the last section, Gauss gives proof for the constructibility of a regular heptadecagon (17-sided polygon) with straightedge and compass by reducing this geometrical problem to an algebraic one. He shows that a regular polygon is constructible if the number of its sides is either a power of 2 or the product of a power of 2 and any number of distinct Fermat primes. In the same section, he gives a result on the number of solutions of certain cubic polynomials with coefficients in finite fields, which amounts to counting integral points on an elliptic curve. An unfinished chapter, consisting of work done during 1797–1799, was found among his papers after his death.
==== Further investigations ====
One of Gauss's first results was the empirically found conjecture of 1792 – the later called prime number theorem – giving an estimation of the number of prime numbers by using the integral logarithm.
In 1816, Olbers encouraged Gauss to compete for a prize from the French Academy for a proof for Fermat's Last Theorem; he refused, considering the topic uninteresting. However, after his death a short undated paper was found with proofs of the theorem for the cases n = 3 and n = 5. The particular case of n = 3 was proved much earlier by Leonhard Euler, but Gauss developed a more streamlined proof which made use of Eisenstein integers; though more general, the proof was simpler than in the real integers case.
Gauss contributed to solving the Kepler conjecture in 1831 with the proof that a greatest packing density of spheres in the three-dimensional space is given when the centres of the spheres form a cubic face-centred arrangement, when he reviewed a book of Ludwig August Seeber on the theory of reduction of positive ternary quadratic forms. Having noticed some lacks in Seeber's proof, he simplified many of his arguments, proved the central conjecture, and remarked that this theorem is equivalent to the Kepler conjecture for regular arrangements.
In two papers on biquadratic residues (1828, 1832) Gauss introduced the ring of Gaussian integers \mathbb{Z}[i], showed that it is a unique factorization domain. and generalized some key arithmetic concepts, such as Fermat's little theorem and Gauss's lemma. The main objective of introducing this ring was to formulate the law of biquadratic reciprocity
In the second paper, he stated the general law of biquadratic reciprocity and proved several special cases of it. In an earlier publication from 1818 containing his fifth and sixth proofs of quadratic reciprocity, he claimed the techniques of these proofs (Gauss sums) can be applied to prove higher reciprocity laws.
=== Analysis ===
One of Gauss's first discoveries was the notion of the arithmetic-geometric mean (AGM) of two positive real numbers. He discovered its relation to elliptic integrals in the years 1798–1799 through Landen's transformation, and a diary entry recorded the discovery of the connection of Gauss's constant to lemniscatic elliptic functions, a result that Gauss stated "will surely open an entirely new field of analysis". He also made early inroads into the more formal issues of the foundations of complex analysis, and from a letter to Bessel in 1811 it is clear that he knew the "fundamental theorem of complex analysis" – Cauchy's integral theorem – and understood the notion of complex residues when integrating around poles.
Euler's pentagonal numbers theorem, together with other researches on the AGM and lemniscatic functions, led him to plenty of results on Jacobi theta functions, His works show that he knew modular transformations of order 3, 5, 7 for elliptic functions since 1808.
Several mathematical fragments in his Nachlass indicate that he knew parts of the modern theory of modular forms. One of Gauss's sketches of this kind was a drawing of a tessellation of the unit disk by "equilateral" hyperbolic triangles with all angles equal to \pi/4.
An example of Gauss's insight in analysis is the cryptic remark that the principles of circle division by compass and straightedge can also be applied to the division of the lemniscate curve, which inspired Abel's theorem on lemniscate division. Another example is his publication "Summatio quarundam serierum singularium" (1811) on the determination of the sign of quadratic Gauss sums, in which he solved the main problem by introducing q-analogs of binomial coefficients and manipulating them by several original identities that seem to stem from his work on elliptic function theory; however, Gauss cast his argument in a formal way that does not reveal its origin in elliptic function theory, and only the later work of mathematicians such as Jacobi and Hermite has exposed the crux of his argument.
In the "Disquisitiones generales circa series infinitam..." (1813), he provides the first systematic treatment of the general hypergeometric function F(\alpha,\beta,\gamma,x), and shows that many of the functions known at the time are special cases of the hypergeometric function. This work is the first exact inquiry into convergence of infinite series in the history of mathematics. Furthermore, it deals with infinite continued fractions arising as ratios of hypergeometric functions, which are now called Gauss continued fractions.
In 1823, Gauss won the prize of the Danish Society with an essay on conformal mappings, which contains several developments that pertain to the field of complex analysis. Gauss stated that angle-preserving mappings in the complex plane must be complex analytic functions, and used the later-named Beltrami equation to prove the existence of isothermal coordinates on analytic surfaces. The essay concludes with examples of conformal mappings into a sphere and an ellipsoid of revolution.
==== Numerical analysis ====
Gauss often deduced theorems inductively from numerical data he had collected empirically. As such, the use of efficient algorithms to facilitate calculations was vital to his research, and he made many contributions to numerical analysis, such as the method of Gaussian quadrature, published in 1816.
In a private letter to Gerling from 1823, he described a solution of a 4x4 system of linear equations with the Gauss-Seidel method – an "indirect" iterative method for the solution of linear systems, and recommended it over the usual method of "direct elimination" for systems of more than two equations.
Gauss invented an algorithm for calculating what is now called discrete Fourier transforms when calculating the orbits of Pallas and Juno in 1805, 160 years before Cooley and Tukey found their similar Cooley–Tukey algorithm. He developed it as a trigonometric interpolation method, but the paper Theoria Interpolationis Methodo Nova Tractata was published only posthumously in 1876, well after Joseph Fourier's introduction of the subject in 1807.
=== Geometry ===
==== Differential geometry ====
The geodetic survey of Hanover fuelled Gauss's interest in differential geometry and topology, fields of mathematics dealing with curves and surfaces. This led him in 1828 to the publication of a work that marks the birth of modern differential geometry of surfaces, as it departed from the traditional ways of treating surfaces as cartesian graphs of functions of two variables, and that initiated the exploration of surfaces from the "inner" point of view of a two-dimensional being constrained to move on it. As a result, the Theorema Egregium (remarkable theorem), established a property of the notion of Gaussian curvature. Informally, the theorem says that the curvature of a surface can be determined entirely by measuring angles and distances on the surface, regardless of the embedding of the surface in three-dimensional or two-dimensional space.
The Theorema Egregium leads to the abstraction of surfaces as doubly-extended manifolds; it clarifies the distinction between the intrinsic properties of the manifold (the metric) and its physical realization in ambient space. A consequence is the impossibility of an isometric transformation between surfaces of different Gaussian curvature. This means practically that a sphere or an ellipsoid cannot be transformed to a plane without distortion, which causes a fundamental problem in designing projections for geographical maps. A portion of this essay is dedicated to a profound study of geodesics. In particular, Gauss proves the local Gauss–Bonnet theorem on geodesic triangles, and generalizes Legendre's theorem on spherical triangles to geodesic triangles on arbitrary surfaces with continuous curvature; he found that the angles of a "sufficiently small" geodesic triangle deviate from that of a planar triangle of the same sides in a way that depends only on the values of the surface curvature at the vertices of the triangle, regardless of the behaviour of the surface in the triangle interior.
Gauss's memoir from 1828 lacks the conception of geodesic curvature. However, in a previously unpublished manuscript, very likely written in 1822–1825, he introduced the term "side curvature" (German: "Seitenkrümmung") and proved its invariance under isometric transformations, a result that was later obtained by Ferdinand Minding and published by him in 1830. This Gauss paper contains the core of his lemma on total curvature, but also its generalization, found and proved by Pierre Ossian Bonnet in 1848 and known as the Gauss–Bonnet theorem.
==== Non-Euclidean geometry ====
During Gauss' lifetime, the Parallel postulate of Euclidean geometry was heavily discussed. Numerous efforts were made to prove it in the frame of the Euclidean axioms, whereas some mathematicians discussed the possibility of geometrical systems without it. Gauss thought about the basics of geometry from the 1790s on, but only realized in the 1810s that a non-Euclidean geometry without the parallel postulate could solve the problem. In a letter to Franz Taurinus of 1824, he presented a short comprehensible outline of what he named a "non-Euclidean geometry", but he strongly forbade Taurinus to make any use of it. Gauss is credited with having been the one to first discover and study non-Euclidean geometry, even coining the term as well.
The first publications on non-Euclidean geometry in the history of mathematics were authored by Nikolai Lobachevsky in 1829 and Janos Bolyai in 1832. In the following years, Gauss wrote his ideas on the topic but did not publish them, thus avoiding influencing the contemporary scientific discussion. Gauss commended the ideas of Janos Bolyai in a letter to his father and university friend Farkas Bolyai claiming that these were congruent to his own thoughts of some decades. However, it is not quite clear to what extent he preceded Lobachevsky and Bolyai, as his written remarks are vague and obscure.
Sartorius first mentioned Gauss's work on non-Euclidean geometry in 1856, but only the publication of Gauss's Nachlass in Volume VIII of the Collected Works (1900) showed Gauss's ideas on the matter, at a time when non-Euclidean geometry was still an object of some controversy.
==== Early topology ====
Gauss was also an early pioneer of topology or Geometria Situs, as it was called in his lifetime. The first proof of the fundamental theorem of algebra in 1799 contained an essentially topological argument; fifty years later, he further developed the topological argument in his fourth proof of this theorem.
Another encounter with topological notions occurred to him in the course of his astronomical work in 1804, when he determined the limits of the region on the celestial sphere in which comets and asteroids might appear, and which he termed "Zodiacus". He discovered that if the Earth's and comet's orbits are linked, then by topological reasons the Zodiacus is the entire sphere. In 1848, in the context of the discovery of the asteroid 7 Iris, he published a further qualitative discussion of the Zodiacus.
In Gauss's letters of 1820–1830, he thought intensively on topics with close affinity to Geometria Situs, and became gradually conscious of semantic difficulty in this field. Fragments from this period reveal that he tried to classify "tract figures", which are closed plane curves with a finite number of transverse self-intersections, that may also be planar projections of knots. To do so he devised a symbolical scheme, the Gauss code, that in a sense captured the characteristic features of tract figures.
In a fragment from 1833, Gauss defined the linking number of two space curves by a certain double integral, and in doing so provided for the first time an analytical formulation of a topological phenomenon. On the same note, he lamented the little progress made in Geometria Situs, and remarked that one of its central problems will be "to count the intertwinings of two closed or infinite curves". His notebooks from that period reveal that he was also thinking about other topological objects such as braids and tangles. he stated the fundamental theorem of axonometry, which tells how to represent a 3D cube on a 2D plane with complete accuracy, via complex numbers. He described rotations of this sphere as the action of certain linear fractional transformations on the extended complex plane, and gave a proof for the geometric theorem that the altitudes of a triangle always meet in a single orthocenter.
Gauss was concerned with John Napier's "Pentagramma mirificum" – a certain spherical pentagram – for several decades; he approached it from various points of view, and gradually gained a full understanding of its geometric, algebraic, and analytic aspects. In particular, in 1843 he stated and proved several theorems connecting elliptic functions, Napier spherical pentagons, and Poncelet pentagons in the plane.
Furthermore, he contributed a solution to the problem of constructing the largest-area ellipse inside a given quadrilateral, and discovered a surprising result about the computation of area of pentagons.
== Sciences ==
=== Astronomy ===
On 1 January 1801, Italian astronomer Giuseppe Piazzi discovered a new celestial object, presumed it to be the long searched planet between Mars and Jupiter according to the so-called Titius–Bode law, and named it Ceres. He could track it only for a short time until it disappeared behind the glare of the Sun. The mathematical tools of the time were not sufficient to predict the location of its reappearance from the few data available. Gauss tackled the problem and predicted a position for possible rediscovery in December 1801. This turned out to be accurate within a half-degree when Franz Xaver von Zach on 7 and 31 December at Gotha, and independently Heinrich Olbers on 1 and 2 January in Bremen, identified the object near the predicted position.
Gauss's method leads to an equation of the eighth degree, of which one solution, the Earth's orbit, is known. The solution sought is then separated from the remaining six based on physical conditions. In this work, Gauss used comprehensive approximation methods which he created for that purpose.
The discovery of Ceres led Gauss to the theory of the motion of planetoids disturbed by large planets, eventually published in 1809 as Theoria motus corporum coelestium in sectionibus conicis solem ambientum. It introduced the Gaussian gravitational constant. After long years of work, he finished it in 1816 without a result that seemed sufficient to him. This marked the end of his activities in theoretical astronomy.
One fruit of Gauss's research on Pallas perturbations was the Determinatio Attractionis... (1818) on a method of theoretical astronomy that later became known as the "elliptic ring method". It introduced an averaging conception in which a planet in orbit is replaced by a fictitious ring with mass density proportional to the time the planet takes to follow the corresponding orbital arcs. Gauss presents the method of evaluating the gravitational attraction of such an elliptic ring, which includes several steps; one of them involves a direct application of the arithmetic-geometric mean (AGM) algorithm to calculate an elliptic integral.
Even after Gauss's contributions to theoretical astronomy came to an end, more practical activities in observational astronomy continued and occupied him during his entire career. As early as 1799, Gauss dealt with the determination of longitude by use of the lunar parallax, for which he developed more convenient formulas than those were in common use. After appointment as director of observatory he attached importance to the fundamental astronomical constants in correspondence with Bessel. Gauss himself provided tables of nutation and aberration, solar coordinates, and refraction. He made many contributions to spherical geometry, and in this context solved some practical problems about navigation by stars. He published a great number of observations, mainly on minor planets and comets; his last observation was the solar eclipse of 28 July 1851.
=== Chronology ===
Gauss's first publication following his doctoral thesis dealt with the determination of the date of Easter (1800), an elementary mathematical topic. Gauss aimed to present a convenient algorithm for people without any knowledge of ecclesiastical or even astronomical chronology, and thus avoided the usual terms of golden number, epact, solar cycle, domenical letter, and any religious connotations. This choice of topic likely had historical grounds. The replacement of the Julian calendar by the Gregorian calendar had caused confusion in the Holy Roman Empire since the 16th century and was not finished in Germany until 1700, when the difference of eleven days was deleted. Even after this, Easter fell on different dates in Protestant and Catholic territories, until this difference was abolished by agreement in 1776. In the Protestant states, such as the Duchy of Brunswick, the Easter of 1777, five weeks before Gauss's birth, was the first one calculated in the new manner. In the history of statistics, this disagreement is called the "priority dispute over the discovery of the method of least squares".
In the first paper he proved Gauss's inequality (a Chebyshev-type inequality) for unimodal distributions, and stated without proof another inequality for moments of the fourth order (a special case of the Gauss-Winckler inequality). He derived lower and upper bounds for the variance of the sample variance. In the second paper, Gauss described recursive least squares methods. His work on the theory of errors was extended in several directions by the geodesist Friedrich Robert Helmert to the Gauss-Helmert model.
Gauss also contributed to problems in probability theory that are not directly concerned with the theory of errors. One example appears as a diary note where he tried to describe the asymptotic distribution of entries in the continued fraction expansion of a random number uniformly distributed in (0,1). He derived this distribution, now known as the Gauss-Kuzmin distribution, as a by-product of the discovery of the ergodicity of the Gauss map for continued fractions. Gauss's solution is the first-ever result in the metrical theory of continued fractions.
=== Geodesy ===
Gauss was busy with geodetic problems since 1799 when he helped Karl Ludwig von Lecoq with calculations during his survey in Westphalia. Beginning in 1804, he taught himself some practical geodesy in Brunswick and Göttingen.
Since 1816, Gauss's former student Heinrich Christian Schumacher, then professor in Copenhagen, but living in Altona (Holstein) near Hamburg as head of an observatory, carried out a triangulation of the Jutland peninsula from Skagen in the north to Lauenburg in the south. This project was the basis for map production but also aimed at determining the geodetic arc between the terminal sites. Data from geodetic arcs were used to determine the dimensions of the earth geoid, and long arc distances brought more precise results. Schumacher asked Gauss to continue this work further to the south in the Kingdom of Hanover; Gauss agreed after a short time of hesitation. Finally, in May 1820, King George IV gave the order to Gauss.
An arc measurement needs a precise astronomical determination of at least two points in the network. Gauss and Schumacher used the coincidence that both observatories in Göttingen and Altona, in the garden of Schumacher's house, laid nearly in the same longitude. The latitude was measured with both their instruments and a zenith sector of Ramsden that was transported to both observatories.
Gauss and Schumacher had already determined some angles between Lüneburg, Hamburg, and Lauenburg for the geodetic connection in October 1818. During the summers of 1821 until 1825 Gauss directed the triangulation work personally, from Thuringia in the south to the river Elbe in the north. The triangle between Hoher Hagen, Großer Inselsberg in the Thuringian Forest, and Brocken in the Harz mountains was the largest one Gauss had ever measured with a maximum size of . In the thinly populated Lüneburg Heath without significant natural summits or artificial buildings, he had difficulties finding suitable triangulation points; sometimes cutting lanes through the vegetation was necessary.
In 1828, when studying differences in latitude, Gauss first defined a physical approximation for the figure of the Earth as the surface everywhere perpendicular to the direction of gravity; later his doctoral student Johann Benedict Listing called this the geoid.
=== Magnetism and telegraphy ===
==== Geomagnetism ====
Gauss had been interested in magnetism since 1803. After Alexander von Humboldt visited Göttingen in 1826, both scientists began intensive research on geomagnetism, partly independently, partly in productive cooperation. In 1828, Gauss was Humboldt's guest during the conference of the Society of German Natural Scientists and Physicians in Berlin, where he got acquainted with the physicist Wilhelm Weber.
When Weber got the chair for physics in Göttingen as successor of Johann Tobias Mayer by Gauss's recommendation in 1831, both of them started a fruitful collaboration, leading to a new knowledge of magnetism with a representation for the unit of magnetism in terms of mass, charge, and time. They founded the Magnetic Association (German: Magnetischer Verein), an international working group of several observatories, which carried out measurements of Earth's magnetic field in many regions of the world using equivalent methods at arranged dates in the years 1836 to 1841.
In 1836, Humboldt suggested the establishment of a worldwide net of geomagnetic stations in the British dominions with a letter to the Duke of Sussex, then president of the Royal Society; he proposed that magnetic measures should be taken under standardized conditions using his methods. Together with other instigators, this led to a global program known as "Magnetical crusade" under the direction of Edward Sabine. The dates, times, and intervals of observations were determined in advance, the Göttingen mean time was used as the standard. 61 stations on all five continents participated in this global program. Gauss and Weber founded a series for publication of the results, six volumes were edited between 1837 and 1843. Weber's departure to Leipzig in 1843 as late effect of the Göttingen Seven affair marked the end of Magnetic Association activity. and the data allowed to determine their location with rather good precision.
Gauss influenced the beginning of geophysics in Russia, when Adolph Theodor Kupffer, one of his former students, founded a magnetic observatory in St. Petersburg, following the example of the observatory in Göttingen, and similarly, Ivan Simonov in Kazan.
Gauss's main theoretical interests in electromagnetism were reflected in his attempts to formulate quantitive laws governing electromagnetic induction. In notebooks from these years, he recorded several innovative formulations; he discovered the vector potential function, independently rediscovered by Franz Ernst Neumann in 1845, and in January 1835 he wrote down an "induction law" equivalent to Faraday's law, which stated that the electromotive force at a given point in space is equal to the instantaneous rate of change (with respect to time) of this function.
Gauss tried to find a unifying law for long-distance effects of electrostatics, electrodynamics, electromagnetism, and induction, comparable to Newton's law of gravitation, but his attempt ended in a "tragic failure". He characterized optical systems under a paraxial approximation only by its cardinal points, and he derived the Gaussian lens formula, applicable without restrictions in respect to the thickness of the lenses.
=== Mechanics ===
Gauss's first work in mechanics concerned the earth's rotation. When his university friend Benzenberg carried out experiments to determine the deviation of falling masses from the perpendicular in 1802, what today is known as the Coriolis force, he asked Gauss for a theory-based calculation of the values for comparison with the experimental ones. Gauss elaborated a system of fundamental equations for the motion, and the results corresponded sufficiently with Benzenberg's data, who added Gauss's considerations as an appendix to his book on falling experiments.
After Foucault had demonstrated the earth's rotation by his pendulum experiment in public in 1851, Gerling questioned Gauss for further explanations. This instigated Gauss to design a new apparatus for demonstration with a much shorter length of pendulum than Foucault's one. The oscillations were observed with a reading telescope, with a vertical scale and a mirror fastened at the pendulum. It is described in the Gauss–Gerling correspondence and Weber made some experiments with this apparatus in 1853, but no data were published.
Gauss's principle of least constraint of 1829 was established as a general concept to overcome the division of mechanics into statics and dynamics, combining D'Alembert's principle with Lagrange's principle of virtual work, and showing analogies to the method of least squares.
=== Metrology ===
In 1828, Gauss was appointed as head of the board for weights and measures of the Kingdom of Hanover. He created standards for length and measure. Gauss himself took care of the time-consuming measures and gave detailed orders for the mechanical construction. In the correspondence with Schumacher, who was also working on this matter, he described new ideas for high-precision scales. He submitted the final reports on the Hanoverian foot and pound to the government in 1841. This work achieved international importance due to an 1836 law that connected the Hanoverian measures with the English ones. the French Academy of Sciences (1804/ 1820), the Royal Society of London (1804), the Royal Prussian Academy in Berlin (1810), the National Academy of Science in Verona (1810), the Royal Society of Edinburgh (1820), the Bavarian Academy of Sciences of Munich (1820), the Royal Danish Academy in Copenhagen (1821), the Royal Astronomical Society in London (1821), the Royal Swedish Academy of Sciences (1821), the American Academy of Arts and Sciences in Boston (1822), the Royal Bohemian Society of Sciences in Prague (1833), the Royal Academy of Science, Letters and Fine Arts of Belgium (1841/1845), the Royal Society of Sciences in Uppsala (1843), the Royal Irish Academy in Dublin (1843), the Royal Institute of the Netherlands (1845/ 1851), the Spanish Royal Academy of Sciences in Madrid (1850), the Russian Geographical Society (1851), the Imperial Academy of Sciences in Vienna (1848), the American Philosophical Society (1853), the Cambridge Philosophical Society, and the Royal Hollandish Society of Sciences in Haarlem.
Both the University of Kazan and the Philosophy Faculty of the University of Prague appointed him honorary member in 1848.
Gauss received the Lalande Prize from the French Academy of Science in 1809 for the theory of planets and the means of determining their orbits from only three observations, the Danish Academy of Science prize in 1823 for his memoir on conformal projection, and the Copley Medal from the Royal Society in 1838 for "his inventions and mathematical researches in magnetism". and became one of the first members of the Prussian Order Pour le Merite (Civil class) when it was established in 1842. He received the Order of the Crown of Westphalia (1810), the Danish Order of the Dannebrog (1817), the Hanoverian Royal Guelphic Order (1815), the Swedish Order of the Polar Star (1844), the Order of Henry the Lion (1849), and the Bavarian Maximilian Order for Science and Art (1853).
The Kings of Hanover appointed him the honorary titles "Hofrath" (1816) and "Geheimer Hofrath" (1845). In 1949, on the occasion of his golden doctor degree jubilee, he received honorary citizenship of both Brunswick and Göttingen. Soon after his death a medal was issued by order of King George V of Hanover with the back inscription dedicated "to the Prince of Mathematicians".
The "Gauss-Gesellschaft Göttingen" ("Göttingen Gauss Society") was founded in 1964 for research on the life and work of Carl Friedrich Gauss and related persons. It publishes the Mitteilungen der Gauss-Gesellschaft (Communications of the Gauss Society).
== Names and commemorations ==
List of things named after Carl Friedrich Gauss
== Selected writings ==
=== Mathematics and astronomy ===
1799: (Doctoral thesis on the fundamental theorem of algebra, University of Helmstedt) Original book
1816: Original
1816: Original
1850: Original (Lecture from 1849)
(German)
1800: Original
1801:
(translated from the second German edition, Göttingen 1860)
1802: Original
1804: Original (on the Zodiacus)
1808: Original (Introduces Gauss's lemma, uses it in the third proof of quadratic reciprocity)
1808:
1809: Original book
1811: Original (from 1810) (Orbit of Pallas)
1811: Original (from 1808) (Determination of the sign of the quadratic Gauss sum, uses this to give the fourth proof of quadratic reciprocity)
1813: Original (from 1812, contains the Gauss's continued fraction)
1816: Original (from 1814)
1818: Original (from 1817) (Fifth and sixth proofs of quadratic reciprocity)
1818: Original (Only reference to the – mostly unpublished – work on the algorithm of the arithmetic-geometric mean.)
1823: Original (from 1821)
1823: Original
1825: (Prize winning essay from 1822 on conformal mapping)
1828: Original book
1828: (from 1826)
(Three essays concerning the calculation of probabilities as the basis of the Gaussian law of error propagation)
1828: Original (from 1827)
1828: Original (from 1825)
1832: Original (from 1831) (Introduces the Gaussian integers, states (without proof) the law of biquadratic reciprocity, proves the supplementary law for 1 + i)
1845: Original (from 1843)
1847: Original (from 1846)
1848: Original
1903: Wissenschaftliches Tagebuch () Original book (from 1847, on the Zodiacus)
=== Physics ===
1804: Fundamentalgleichungen für die Bewegung schwerer Körper auf der Erde ( in original book: Original)
1813: Original (contains Gauss's theorem of vector analysis)
1817:
1829:
1830: Original (from 1829)
1841: Original (from 1832){{efn|Gauss presented the text to the Göttingen Academy in December 1832, a preprint in Latin with a small number of copies appeared in 1833. It was soon translated and published in German and French. The complete text in Latin was published in 1841. The literary estate is kept and provided by the Göttingen State and University Library. Written materials from Carl Friedrich Gauss and family members can also be found in the municipal archive of Brunswick.
|
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"Palm Heinrich Ludwig von Boguslawski",
"Austrian Academy of Sciences",
"Cambridge Philosophical Society",
"Chebyshev's inequality",
"The American Mathematical Monthly",
"magnetism",
"unique factorization theorem",
"Royal Academy of Science, Letters and Fine Arts of Belgium",
"Heliotrope (instrument)",
"James Cooley",
"instantaneous rate of change",
"embedding",
"Jupiter",
"Gustav Kirchhoff",
"Ernst Klinkerfues",
"Elemente der Mathematik",
"Solar cycle (calendar)",
"August Ritter (civil engineer)",
"Constructible polygon",
"achromatic lens",
"spherical geometry",
"Skagen",
"Georg Frederik Ursin",
"quadrilateral",
"Gaussian elimination",
"Euclidean geometry",
"geodesic curvature",
"Gauss composition law",
"topology",
"Leonhard Euler",
"pentagon",
"Nachlass",
"Henrik Johan Walbeck",
"Notes and Records of the Royal Society",
"Lalande Prize",
"Johann Benedict Listing",
"Missouri",
"pentagram",
"Gotthold Eisenstein",
"St. Petersburg",
"Gauss-Helmert model",
"Dispersion (optics)",
"discrete Fourier transform",
"franc",
"Royal Guelphic Order",
"Earth ellipsoid",
"power of 2",
"Royal Society",
"Gauss's diary",
"Order of the Polar Star",
"Braid theory",
"Altitude (triangle)",
"Gauss's inequality",
"Springer Science+Business Media",
"Pentagonal number theorem",
"Theorema Egregium",
"Mathematics Magazine",
"Prussian Academy of Sciences",
"Moritz Abraham Stern",
"Jacobi triple product identity",
"heptadecagon",
"Astrophysics Data System",
"Tangle (mathematics)",
"Fermat's Last Theorem",
"Adolph Theodor Kupffer",
"Monthly Notices of the Royal Astronomical Society",
"Gauss-Seidel method",
"Hans Christian Ørsted",
"Mobius transformation",
"triangulation",
"H. C. Schumacher",
"Pierre Ossian Bonnet",
"Jesse Ramsden",
"Harz",
"Thuringian Forest",
"observational astronomy",
"triaxial ellipsoid",
"Order of Henry the Lion",
"sextant",
"Journal of the Royal Astronomical Society of Canada",
"Prince-primate",
"Moritz Cantor",
"Gauss–Bonnet theorem",
"Heinrich Christian Schumacher",
"Heinrich Ewald",
"Conrad Heinrich Fuchs",
"Charles William Ferdinand, Duke of Brunswick",
"Sophie Germain",
"Hamburg",
"Frankfurt",
"Gotha Observatory",
"Cambridge University Press",
"Wilhelm Olbers",
"Royal Society of Edinburgh",
"Meridian circle",
"Hermann Wagner (geographer)",
"modular forms",
"Mathematische Annalen",
"Standard (metrology)",
"Karl Kreil",
"Discrete & Computational Geometry",
"Joseph-Louis Lagrange",
"Ludwig Maximilian University of Munich",
"Wolfgang Sartorius von Waltershausen",
"honorary citizenship",
"Compass and straightedge constructions",
"geoid",
"Magnetic dip",
"Johann Elert Bode",
"Heinrich Wilhelm Matthäus Olbers",
"gout",
"Carl August von Steinheil",
"Fritz Schaper",
"Prince-elector",
"Christian Ludwig Gerling",
"mathematical table",
"normal distribution",
"Order Pour le Merite",
"Göttingen Observatory",
"Kingdom of Hanover",
"Eisenstein integers",
"variance",
"Magnetic vector potential",
"Julian calendar",
"Duchy of Holstein",
"Heinrich Wilhelm Matthias Olbers",
"observatory",
"unique factorization domain",
"sample variance",
"iterative method",
"Neue Deutsche Biographie",
"Hanover",
"Gaussian binomial coefficient",
"Karl Ludwig von Lecoq",
"Moritz Ludwig George Wichmann",
"electric Induction",
"orbital resonance",
"Edward Sabine",
"analytic function",
"lemniscatic elliptic functions",
"John Napier",
"Honorary degree",
"Joseph von Fraunhofer",
"Ernest Augustus, King of Hanover",
"closed-form expression",
"biquadratic reciprocity",
"hyperbolic triangle",
"latitude",
"Gauss's theorem",
"first lieutenant",
"Binary quadratic form",
"Braunschweig",
"Aberration (astronomy)",
"magnetometer",
"Copley Medal",
"Johann Friedrich Ludwig Hausmann",
"Jacobi theta functions",
"vector analysis",
"Classics",
"Christian August Friedrich Peters",
"Bavarian Academy of Sciences and Humanities",
"geophysics",
"Georg Christoph Lichtenberg",
"Jutland",
"Joseph Fourier",
"Heinrich Wilhelm Brandes",
"residue (complex analysis)",
"chromatic aberration",
"masterpiece",
"Mathematics of Computation",
"Friedrich Bernhard Gottfried Nicolai",
"physicist",
"Cardinal point (optics)",
"Copenhagen",
"Legendre's theorem on spherical triangles",
"Johann Friedrich Pfaff",
"Seal (emblem)",
"Bremen",
"Jeremy Gray",
"angle",
"(2) Pallas",
"Justus Liebig",
"Walter Scott",
"Kingdom of Prussia",
"lemniscate curve",
"triangle",
"flattening",
"War of the Fourth Coalition",
"linking number",
"Coriolis force",
"The Mathematical Gazette",
"Bernhard Riemann",
"Accademia nazionale delle scienze",
"class number formula",
"2 Pallas",
"L'Enseignement mathématique",
"Gauss-Kuzmin-Wirsing operator",
"Close-packing of equal spheres",
"mathematician",
"Random House Webster's Unabridged Dictionary",
"Twelve Olympians",
"Jean le Rond d'Alembert",
"Johann Georg Repsold",
"curve",
"Johann Friedrich Benzenberg",
"Logarithmic integral function",
"Lüneburg Heath",
"George Green (mathematician)",
"Eduard Heine",
"Achromatic lens",
"fast Fourier transform",
"Baseline (surveying)",
"elliptic curve",
"Lüneburg",
"Duchy of Brunswick-Wolfenbüttel",
"Kingdom of Westphalia",
"invariant (mathematics)",
"George III",
"Altona, Hamburg",
"University of Kazan",
"Johann Tobias Mayer",
"Earth's magnetic field",
"Latin",
"Acta Arithmetica",
"Johann Franz Encke",
"Rudolf Wagner",
"Royal Swedish Academy of Sciences",
"Eberhard August Wilhelm von Zimmermann",
"probability theory",
"actuarial science",
"Triangulation network",
"Perturbation (astronomy)",
"St. Peterburg",
"Date of Easter",
"Lilienthal, Lower Saxony",
"threnody",
"heliometer",
"Fermat's little theorem",
"conformal mapping",
"Transverse Mercator projection",
"Ernst zu Münster",
"Foot (unit)",
"Gaussian optics",
"Benjamin Apthorp Gould",
"Alexander von Humboldt",
"Friedrich Wilhelm Bessel",
"Gauss's constant",
"figure of the Earth",
"applied mathematics",
"tessellation",
"quadratic reciprocity"
] |
6,130 |
Cornish language
|
Cornish (Standard Written Form: or , ) is a Southwestern Brittonic language of the Celtic language family. Along with Welsh and Breton, Cornish is descended from the Common Brittonic language spoken throughout much of Great Britain before the English language came to dominate. For centuries, until it was pushed westwards by English, it was the main language of Cornwall, maintaining close links with its sister language Breton, with which it was mutually intelligible, perhaps even as long as Cornish continued to be spoken as a vernacular. Cornish continued to function as a common community language in parts of Cornwall until the mid 18th century, and there is some evidence for traditional speakers of the language persisting into the 19th century.
Cornish became extinct as a living community language in Cornwall by the end of the 18th century, although knowledge of Cornish, including speaking ability to a certain extent, persisted within some families and individuals. A revival started in the early 20th century, and in 2010 UNESCO reclassified the language as critically endangered, stating that its former classification of the language as extinct was no longer accurate. The language has a growing number of second-language speakers, and a very small number of families now raise children to speak revived Cornish as a first language.
Cornish is currently recognised under the European Charter for Regional or Minority Languages, and the language is often described as an important part of Cornish identity, culture and heritage. Since the revival of the language, some Cornish textbooks and works of literature have been published, and an increasing number of people are studying the language. independent films, and children's books. A small number of people in Cornwall have been brought up to be bilingual native speakers, and the language is taught in schools and appears on street nameplates. The first Cornish-language day care opened in 2010.
== Classification ==
Cornish is a Southwestern Brittonic language, a branch of the Insular Celtic section of the Celtic language family, which is a sub-family of the Indo-European language family. Brittonic also includes Welsh, Breton, Cumbric and possibly Pictish, the last two of which are extinct. Scottish Gaelic, Irish and Manx are part of the separate Goidelic branch of Insular Celtic.
Joseph Loth viewed Cornish and Breton as being two dialects of the same language, claiming that "Middle Cornish is without doubt closer to Breton as a whole than the modern Breton dialect of Quiberon [] is to that of Saint-Pol-de-Léon []." Also, Kenneth Jackson argued that it is almost certain that Cornish and Breton would have been mutually intelligible as long as Cornish was a living language, and that Cornish and Breton are especially closely related to each other and less closely related to Welsh.
== History ==
Cornish evolved from the Common Brittonic spoken throughout Britain south of the Firth of Forth during the British Iron Age and Roman period. As a result of westward Anglo-Saxon expansion, the Britons of the southwest were separated from those in modern-day Wales and Cumbria, which Jackson links to the defeat of the Britons at the Battle of Deorham in about 577. The western dialects eventually evolved into modern Welsh and the now extinct Cumbric, while Southwestern Brittonic developed into Cornish and Breton, the latter as a result of emigration to parts of the continent, known as Brittany over the following centuries.
=== Old Cornish ===
The area controlled by the southwestern Britons was progressively reduced by the expansion of Wessex over the next few centuries. During the Old Cornish () period (800–1200), the Cornish-speaking area was largely coterminous with modern-day Cornwall, after the Saxons had taken over Devon in their south-westward advance, which probably was facilitated by a second migration wave to Brittany that resulted in the partial depopulation of Devon.
The earliest written record of the Cornish language comes from this period: a 9th-century gloss in a Latin manuscript of by Boethius, which used the words . The phrase may mean "it [the mind] hated the gloomy places", or alternatively, as Andrew Breeze suggests, "she hated the land". Other sources from this period include the Saints' List, a list of almost fifty Cornish saints, the Bodmin manumissions, which is a list of manumittors and slaves, the latter with mostly Cornish names, and, more substantially, a Latin–Cornish glossary (the or Cottonian Vocabulary), a Cornish translation of Ælfric of Eynsham's Latin–Old English Glossary, which is thematically arranged into several groups, such as the Genesis creation narrative, anatomy, church hierarchy, the family, names for various kinds of artisans and their tools, flora, fauna, and household items. The manuscript was widely thought to be in Old Welsh until the 18th century when it was identified as Cornish by Edward Lhuyd. Some Brittonic glosses in the 9th-century colloquy were once identified as Old Cornish, but they are more likely Old Welsh, possibly influenced by a Cornish scribe. No single phonological feature distinguishes Cornish from both Welsh and Breton until the beginning of the assibilation of dental stops in Cornish, which is not found before the second half of the eleventh century, and it is not always possible to distinguish Old Cornish, Old Breton, and Old Welsh orthographically.
=== Middle Cornish ===
The Cornish language continued to flourish well through the Middle Cornish () period (1200–1600), reaching a peak of about 39,000 speakers in the 13th century, after which the number started to decline. From this period also are the hagiographical dramas (The Life of Meriasek) and (The Life of Ke), both of which feature as an antagonist the villainous and tyrannical King Tewdar (or Teudar), a historical medieval king in Armorica and Cornwall, who, in these plays, has been interpreted as a lampoon of either of the Tudor kings Henry VII or Henry VIII.
Others are the Charter Fragment, the earliest known continuous text in the Cornish language, apparently part of a play about a medieval marriage, and (The Passion of Our Lord), a poem probably intended for personal worship, were written during this period, probably in the second half of the 14th century. Another important text, the , was realized to be Cornish in 1949, having previously been incorrectly classified as Welsh. It is the longest text in the traditional Cornish language, consisting of around 30,000 words of continuous prose. This text is a late 16th century translation of twelve of Bishop Bonner's thirteen homilies by a certain John Tregear, tentatively identified as a vicar of St Allen from Crowan, and has an additional catena, Sacrament an Alter, added later by his fellow priest, Thomas Stephyn. In the reign of Henry VIII, an account was given by Andrew Boorde in his 1542 . He states, ""
When Parliament passed the Act of Uniformity 1549, which established the 1549 edition of the English Book of Common Prayer as the sole legal form of worship in England, including Cornwall, people in many areas of Cornwall did not speak or understand English. The passing of this Act was one of the causes of the Prayer Book Rebellion (which may also have been influenced by government repression after the failed Cornish rebellion of 1497), with "the commoners of Devonshyre and Cornwall" producing a manifesto demanding a return to the old religious services and included an article that concluded, "and so we the Cornyshe men (whereof certen of us understande no Englysh) utterly refuse thys newe Englysh." In response to their articles, the government spokesman (either Philip Nichols or Nicholas Udall) wondered why they did not just ask the king for a version of the liturgy in their own language. Archbishop Thomas Cranmer asked why the Cornishmen should be offended by holding the service in English, when they had before held it in Latin, which even fewer of them could understand. Anthony Fletcher points out that this rebellion was primarily motivated by religious and economic, rather than linguistic, concerns. The rebellion prompted a heavy-handed response from the government, and 5,500 people died during the fighting and the rebellion's aftermath. Government officials then directed troops under the command of Sir Anthony Kingston to carry out pacification operations throughout the West Country. Kingston subsequently ordered the executions of numerous individuals suspected of involvement with the rebellion as part of the post-rebellion reprisals.
The rebellion eventually proved a turning-point for the Cornish language, as the authorities came to associate it with sedition and "backwardness". This proved to be one of the reasons why the Book of Common Prayer was never translated into Cornish (unlike Welsh), as proposals to do so were suppressed in the rebellion's aftermath. The failure to translate the Book of Common Prayer into Cornish led to the language's rapid decline during the 16th and 17th centuries. Peter Berresford Ellis cites the years 1550–1650 as a century of immense damage for the language, and its decline can be traced to this period. In 1680 William Scawen wrote an essay describing 16 reasons for the decline of Cornish, among them the lack of a distinctive Cornish alphabet, the loss of contact between Cornwall and Brittany, the cessation of the miracle plays, loss of records in the Civil War, lack of a Cornish Bible and immigration to Cornwall. Mark Stoyle, however, has argued that the 'glotticide' of the Cornish language was mainly a result of the Cornish gentry adopting English to dissociate themselves from the reputation for disloyalty and rebellion associated with the Cornish language since the 1497 uprising.
=== Late Cornish ===
By the middle of the 17th century, the language had retreated to Penwith and Kerrier, and transmission of the language to new generations had almost entirely ceased. In his Survey of Cornwall, published in 1602, Richard Carew writes:[M]ost of the inhabitants can speak no word of Cornish, but very few are ignorant of the English; and yet some so affect their own, as to a stranger they will not speak it; for if meeting them by chance, you inquire the way, or any such matter, your answer shall be, "," "I [will] speak no Saxonage."
The Late Cornish () period from 1600 to about 1800 has a less substantial body of literature than the Middle Cornish period, but the sources are more varied in nature, including songs, poems about fishing and curing pilchards, and various translations of verses from the Bible, the Ten Commandments, the Lord's Prayer and the Creed. Edward Lhuyd's Archaeologia Britannica, which was mainly recorded in the field from native speakers in the early 1700s, and his unpublished field notebook are seen as important sources of Cornish vocabulary, some of which are not found in any other source. Archaeologia Britannica also features a complete version of a traditional folk tale, John of Chyanhor, a short story about a man from St Levan who goes far to the east seeking work, eventually returning home after three years to find that his wife has borne him a child during his absence.
In 1776, William Bodinar, who describes himself as having learned Cornish from old fishermen when he was a boy, wrote a letter to Daines Barrington in Cornish, with an English translation, which was probably the last prose written in the traditional language. In his letter, he describes the sociolinguistics of the Cornish language at the time, stating that there are no more than four or five old people in his village who can still speak Cornish, concluding with the remark that Cornish is no longer known by young people. However, the last recorded traditional Cornish literature may have been the Cranken Rhyme, a corrupted version of a verse or song published in the late 19th century by John Hobson Matthews, recorded orally by John Davey (or Davy) of Boswednack, of uncertain date but probably originally composed during the last years of the traditional language. Davey had traditional knowledge of at least some Cornish. John Kelynack (1796–1885), a fisherman of Newlyn, was sought by philologists for old Cornish words and technical phrases in the 19th century.
=== Decline of Cornish speakers between 1300 and 1800 ===
It is difficult to state with certainty when Cornish ceased to be spoken, due to the fact that its last speakers were of relatively low social class and that the definition of what constitutes "a living language" is not clear cut. Peter Pool argues that by 1800 nobody was using Cornish as a daily language and no evidence exists of anyone capable of conversing in the language at that date. However, passive speakers, semi-speakers and rememberers, who retain some competence in the language despite not being fluent nor using the language in daily life, generally survive even longer.
The traditional view that Dolly Pentreath (1692–1777) was the last native speaker of Cornish has been challenged, However, although it is clear Davey possessed some traditional knowledge in addition to having read books on Cornish, accounts differ of his competence in the language. Some contemporaries stated he was able to converse on certain topics in Cornish whereas others affirmed they had never heard him claim to be able to do so.
The search for the last speaker is hampered by a lack of transcriptions or audio recordings, so that it is impossible to tell from this distance whether the language these people were reported to be speaking was Cornish, or English with a heavy Cornish substratum, nor what their level of fluency was. Nevertheless, this academic interest, along with the beginning of the Celtic Revival in the late 19th century, provided the groundwork for a Cornish language revival movement.
Notwithstanding the uncertainty over who was the last speaker of Cornish, researchers have posited the following numbers for the prevalence of the language between 1050 and 1800.
=== Revived Cornish ===
In 1904, the Celtic language scholar and Cornish cultural activist Henry Jenner published A Handbook of the Cornish Language. The publication of this book is often considered to be the point at which the revival movement started. Jenner wrote about the Cornish language in 1905, "one may fairly say that most of what there was of it has been preserved, and that it has been continuously preserved, for there has never been a time when there were not some Cornishmen who knew some Cornish."
The revival focused on reconstructing and standardising the language, including coining new words for modern concepts, and creating educational material in order to teach Cornish to others. In 1929 Robert Morton Nance published his Unified Cornish () system, based on the Middle Cornish literature while extending the attested vocabulary with neologisms and forms based on Celtic roots also found in Breton and Welsh, publishing a dictionary in 1938. Nance's work became the basis of revived Cornish () for most of the 20th century. During the 1970s, criticism of Nance's system, including the inconsistent orthography and unpredictable correspondence between spelling and pronunciation, resulted in the creation of several rival systems. In the 1980s, Ken George published a new system, ('Common Cornish'), based on a reconstruction of the phonological system of Middle Cornish, but with an approximately morphophonemic orthography. It was subsequently adopted by the Cornish Language Board and was the written form used by a reported 54.5% of all Cornish language users according to a survey in 2008, but was heavily criticised for a variety of reasons by Jon Mills and Nicholas Williams, including making phonological distinctions that they state were not made in the traditional language , failing to make distinctions that they believe were made in the traditional language at this time, and the use of an orthography that deviated too far from the traditional texts and Unified Cornish. Also during this period, Richard Gendall created his Modern Cornish system (also known as Revived Late Cornish), which used Late Cornish as a basis, and Nicholas Williams published a revised version of Unified; In 2010 a new milestone was reached when UNESCO altered its classification of Cornish, stating that its previous label of "extinct" was no longer accurate. From before the 1980s to the end of the 20th century there was a sixfold increase in the number of speakers to around 300. One figure for the number of people who know a few basic words, such as knowing that "Kernow" means "Cornwall", was 300,000; the same survey gave the number of people able to have simple conversations as 3,000.
The Cornish Language Strategy project commissioned research to provide quantitative and qualitative evidence for the number of Cornish speakers: due to the success of the revival project it was estimated that 2,000 people were fluent (surveyed in spring 2008), an increase from the estimated 300 people who spoke Cornish fluently suggested in a study by Kenneth MacKinnon in 2000.
Jenefer Lowe of the Cornish Language Partnership said in an interview with the BBC in 2010 that there were around 300 fluent speakers. Bert Biscoe, a councillor and bard, in a statement to the Western Morning News in 2014 said there were "several hundred fluent speakers". Cornwall Council estimated in 2015 that there were 300–400 fluent speakers who used the language regularly, with 5,000 people having a basic conversational ability in the language.
A report on the 2011 Census published in 2013 by the Office for National Statistics placed the number of speakers at somewhere between 325 and 625. In 2017 the ONS released data based on the 2011 Census that placed the number of speakers at 557 people in England and Wales who declared Cornish to be their main language, 464 of whom lived in Cornwall.
A study that appeared in 2018 established the number of people in Cornwall with at least minimal skills in Cornish, such as the use of some words and phrases, to be more than 3,000, including around 500 estimated to be fluent.
The Institute of Cornish Studies at the University of Exeter is working with the Cornish Language Partnership to study the Cornish language revival of the 20th century, including the growth in number of speakers.
== Legal status and recognition ==
In 2002, Cornish was recognized by the UK government under Part II of the European Charter for Regional or Minority Languages. UNESCO's Atlas of World Languages classifies Cornish as "critically endangered". UNESCO has said that a previous classification of 'extinct' "does not reflect the current situation for Cornish" and is "no longer accurate". This plan has drawn some criticism. In October 2015, the council announced that staff would be encouraged to use "basic words and phrases" in Cornish when dealing with the public. In 2021 Cornwall Council prohibited a marriage ceremony from being conducted in Cornish as the Marriage Act 1949 only allowed for marriage ceremonies in English or Welsh.
In 2014, the Cornish people were recognised by the UK Government as a national minority under the Framework Convention for the Protection of National Minorities. The FCNM provides certain rights and protections to a national minority with regard to their minority language.
In 2016, British government funding for the Cornish language ceased, and responsibility transferred to Cornwall Council.
== Orthography ==
=== Old Cornish orthography ===
Until around the middle of the 11th century, Old Cornish scribes used a traditional spelling system shared with Old Breton and Old Welsh, based on the pronunciation of British Latin. By the time of the , usually dated to around 1100, Old English spelling conventions, such as the use of thorn (Þ, þ) and eth (Ð, ð) for dental fricatives, and wynn (Ƿ, ƿ) for /w/, had come into use, allowing documents written at this time to be distinguished from Old Welsh, which rarely uses these characters, and Old Breton, which does not use them at all. Old Cornish features include using initial ⟨ch⟩, ⟨c⟩, or ⟨k⟩ for /k/, and, in internal and final position, ⟨p⟩, ⟨t⟩, ⟨c⟩, ⟨b⟩, ⟨d⟩, and ⟨g⟩ are generally used for the phonemes /b/, /d/, /ɡ/, /β/, /ð/, and /ɣ/ respectively, meaning that the results of Brittonic lenition are not usually apparent from the orthography at this time.
=== Middle Cornish orthography ===
Middle Cornish orthography has a significant level of variation, and shows influence from Middle English spelling practices. Yogh (Ȝ ȝ) is used in certain Middle Cornish texts, where it is used to represent a variety of sounds, including the dental fricatives /θ/ and /ð/, a usage which is unique to Middle Cornish and is never found in Middle English. Middle Cornish scribes tend to use ⟨c⟩ for /k/ before back vowels, and ⟨k⟩ for /k/ before front vowels, though this is not always true, and this rule is less consistent in certain texts. Middle Cornish scribes almost universally use ⟨wh⟩ to represent /ʍ/ (or /hw/), as in Middle English. Middle Cornish, especially towards the end of this period, tends to use orthographic ⟨g⟩ and ⟨b⟩ in word-final position in stressed monosyllables, and ⟨k⟩ and ⟨p⟩ in word-final position in unstressed final syllables, to represent the reflexes of late Brittonic /ɡ/ and /b/, respectively.
=== Late Cornish orthography ===
Written sources from this period are often spelled following English spelling conventions since many of the writers of the time had not been exposed to Middle Cornish texts or the Cornish orthography within them. Around 1700, Edward Lhuyd visited Cornwall, introducing his own partly phonetic orthography that he used in his , which was adopted by some local writers, leading to the use of some Lhuydian features such as the use of circumflexes to denote long vowels, ⟨k⟩ before front vowels, word-final ⟨i⟩, and the use of ⟨dh⟩ to represent the voiced dental fricative /ð/. Nance's system was used by almost all Revived Cornish speakers and writers until the 1970s. Criticism of Nance's system, particularly the relationship of spelling to sounds and the phonological basis of Unified Cornish, resulted in rival orthographies appearing by the early 1980s, including Gendal's Modern Cornish, based on Late Cornish native writers and Lhuyd, and Ken George's Kernewek Kemmyn, a mainly morphophonemic orthography based on George's reconstruction of Middle Cornish , which features a number of orthographic, and phonological, distinctions not found in Unified Cornish. resulted in the creation of Unified Cornish Revised, a modified version of Nance's orthography, featuring: an additional phoneme not distinguished by Nance, "ö in German ", represented in the UCR orthography by ⟨ue⟩; replacement of ⟨y⟩ with ⟨e⟩ in many words; internal ⟨h⟩ rather than ⟨gh⟩; and use of final ⟨b⟩, ⟨g⟩, and ⟨dh⟩ in stressed monosyllables. A Standard Written Form, intended as a compromise orthography for official and educational purposes, was introduced in 2008, although a number of previous orthographic systems remain in use and, in response to the publication of the SWF, another new orthography, Kernowek Standard, was created, mainly by Nicholas Williams and Michael Everson, which is proposed as an amended version of the Standard Written Form.
== Phonology ==
The phonological system of Old Cornish, inherited from Proto-Southwestern Brittonic and originally differing little from Old Breton and Old Welsh, underwent various changes during its Middle and Late phases, eventually resulting in several characteristics not found in the other Brittonic languages. The first sound change to distinguish Cornish from both Breton and Welsh, the assibilation of the dental stops and in medial and final position, had begun by the time of the , or earlier. This change, and the subsequent, or perhaps dialectical, palatalization (or occasional rhotacization in a few words) of these sounds, results in orthographic forms such as Middle Cornish 'father', Late Cornish (Welsh ), Middle Cornish 'believe', Late Cornish (Welsh ), and Middle Cornish 'leave', Late Cornish (Welsh ). A further characteristic sound change, pre-occlusion, occurred during the 16th century, resulting in the nasals and being realised as and respectively in stressed syllables, and giving Late Cornish forms such as 'head' (Welsh ) and 'crooked' (Welsh ).
As a revitalised language, the phonology of contemporary spoken Cornish is based on a number of sources, including various reconstructions of the sound system of middle and early modern Cornish based on an analysis of internal evidence such as the orthography and rhyme used in the historical texts, comparison with the other Brittonic languages Breton and Welsh, and the work of the linguist Edward Lhuyd, who visited Cornwall in 1700 and recorded the language in a partly phonetic orthography.
== Vocabulary ==
Cornish is a Celtic language, and the majority of its vocabulary, when usage frequency is taken into account, at every documented stage of its history is inherited from Proto-Celtic, either directly from the ancestral Proto-Indo-European language or through vocabulary borrowed from unknown substrate language(s) at some point in the development of the Celtic proto-language from PIE. Examples of the PIE > PCelt. development are various terms related to kinship and people, including 'mother', 'aunt, mother's sister', 'sister', 'son', 'man', 'person, human', and 'people', and words for parts of the body, including 'hand' and 'tooth'. Inherited adjectives with an Indo-European etymology include 'new', 'broad, wide', 'red', 'old', 'young', and 'alive, living'.
Several Celtic or Brittonic words cannot be reconstructed to Proto-Indo-European, and are suggested to have been borrowed from unknown substrate language(s) at an early stage, such as Proto-Celtic or Proto-Brittonic. Proposed examples in Cornish include 'beer' and 'badger'.
Other words in Cornish inherited direct from Proto-Celtic include a number of toponyms, for example 'hill', 'fort', and 'land', and a variety of animal names such as 'mouse', 'wether', 'pigs', and 'bull'.
During the Roman occupation of Britain a large number (around 800) of Latin loan words entered the vocabulary of Common Brittonic, which subsequently developed in a similar way to the inherited lexicon. These include 'arm' (from British Latin ), 'net' (from ), and 'cheese' (from ).
A substantial number of loan words from English and to a lesser extent French entered the Cornish language throughout its history. Whereas only 5% of the vocabulary of the Old Cornish Vocabularium Cornicum is thought to be borrowed from English, and only 10% of the lexicon of the early modern Cornish writer William Rowe, around 42% of the vocabulary of the whole Cornish corpus is estimated to be English loan words, without taking frequency into account. (However, when frequency is taken into account, this figure for the entire corpus drops to 8%.) The many English loanwords, some of which were sufficiently well assimilated to acquire native Cornish verbal or plural suffixes or be affected by the mutation system, include 'to read', 'to understand', 'way', 'boot' and 'art'.
Many Cornish words, such as mining and fishing terms, are specific to the culture of Cornwall. Examples include 'mine waste' and 'to mend fishing nets'. and are different types of pastries. is a 'traditional Cornish dance get-together' and is a specific kind of ceremonial dance that takes place in Cornwall. Certain Cornish words may have several translation equivalents in English, so for instance may be translated into English as either 'book' or 'volume' and can mean either 'hand' or 'fist'.
Like other Celtic languages, Cornish lacks a number of verbs commonly found in other languages, including modals and psych-verbs; examples are 'have', 'like', 'hate', 'prefer', 'must/have to' and 'make/compel to'. These functions are instead fulfilled by periphrastic constructions involving a verb and various prepositional phrases.
== Grammar ==
The grammar of Cornish shares with other Celtic languages a number of features which, while not unique, are unusual in an Indo-European context. The grammatical features most unfamiliar to English speakers of the language are the initial consonant mutations, the verb–subject–object word order, inflected prepositions, fronting of emphasised syntactic elements and the use of two different forms for 'to be'.
=== Morphology ===
==== Mutations ====
Cornish has initial consonant mutation: The first sound of a Cornish word may change according to grammatical context. As in Breton, there are four types of mutation in Cornish (compared with three in Welsh, two in Irish and Manx and one in Scottish Gaelic). These changes apply to only certain letters (sounds) in particular grammatical contexts, some of which are given below:
Lenition or "soft" mutation:
Feminine singular nouns are lenited after 'the':
'cat' > 'the cat'
Spirantization or "aspirate" mutation:
Nouns are spirantized after 'my':
'father' > 'my father'
Provection or "hard" mutation:
Verbs are provected after the verbal particle (approximately English "-ing"):
'see' > 'seeing'
Lenition followed by provection (usually), or "mixed" mutation:
Type 1 mixed mutation:
Occurs after the affirmative particle :
> 'I see'
Type 2 mixed mutation:
Occurs after 2nd person singular infixed pronoun :
'hand' > 'in thy hand'
==== Articles ====
Cornish has no indefinite article. can either mean 'harbour' or 'a harbour'. In certain contexts, can be used, with the meaning 'a certain, a particular', e.g. 'a certain harbour'. There is, however, a definite article 'the', which is used for all nouns regardless of their gender or number, e.g. 'the harbour'.
==== Nouns ====
Cornish nouns belong to one of two grammatical genders, masculine and feminine, but are not inflected for case. Nouns may be singular or plural. Plurals can be formed in various ways, depending on the noun:
Vowel change:
'hole' > 'holes'
Addition of a specific plural suffix:
'angel' > 'angels'
'father' > 'fathers'
'peddler' > 'peddlers'
Suppletion:
'man' > 'men, people'
Some nouns are collective or mass nouns. Singulatives can be formed from collective nouns by the addition of the suffix ⫽-enn⫽ (SWF -en):
'grass' > 'a blade of grass'
'willow-trees' > 'a willow tree'
==== Verbs ====
Verbs are conjugated for person, number, tense and mood. For example, the verbal noun 'see' has derived forms such as 1st person singular present indicative 'I see', 3rd person plural imperfect indicative 'they saw', and 2nd person singular imperative 'see!' Grammatical categories can be indicated either by inflection of the main verb, or by the use of auxiliary verbs such as 'be' or 'do'.
==== Prepositions ====
Cornish uses inflected (or conjugated) prepositions: Prepositions are inflected for person and number. For example, (with, by) has derived forms such as 'with me', 'with him', and 'with you (plural)'.
=== Syntax ===
Word order in Cornish is somewhat fluid and varies depending on several factors such as the intended element to be emphasised and whether a statement is negative or affirmative. In a study on Cornish word order in the play Bewnans Meriasek (), Ken George has argued that the most common word order in main clauses in Middle Cornish was, in affirmative statements, SVO, with the verb in the third person singular:
When affirmative statements are in the less common VSO order, they usually begin with an adverb or other element, followed by an affirmative particle, with the verb inflected for person and tense:
In negative statements, the order was usually VSO, with an initial negative particle and the verb conjugated for person and tense:
A similar structure is used for questions:
Elements can be fronted for emphasis:
Sentences can also be constructed periphrastically using auxiliary verbs such as 'be, exist':
As Cornish lacks verbs such as 'to have', possession can also be indicated in this way:
Enquiring about possession is similar, using a different interrogative form of :
Nouns usually precede the adjective, unlike in English:
Some adjectives usually precede the noun, however:
== Culture ==
The Celtic Congress and Celtic League are groups that advocate cooperation amongst the Celtic Nations in order to protect and promote Celtic languages and cultures, thus working in the interests of the Cornish language.
There have been films such as , some televised, made entirely, or significantly, in Cornish. Some businesses use Cornish names.
Cornish has significantly and durably affected Cornwall's place-names as well as Cornish surnames and knowledge of the language helps the understanding of these ancient meanings. Cornish names are adopted for children, pets, houses and boats.
There is Cornish literature, including spoken poetry and song, as well as traditional Cornish chants historically performed in marketplaces during religious holidays and public festivals and gatherings.
There are periodicals solely in the language, such as the monthly , and . BBC Radio Cornwall has a news broadcast in Cornish and sometimes has other programmes and features for learners and enthusiasts. Local newspapers such as the Western Morning News have articles in Cornish, and newspapers such as The Packet, The West Briton, and The Cornishman have also been known to have Cornish features. There is an online radio and TV service in Cornish called , publishing a one-hour podcast each week, based on a magazine format. It includes music in Cornish as well as interviews and features.
The language has financial sponsorship from sources including the Millennium Commission. A number of language organisations exist in Cornwall: (Our Language), the Cornish sub-group of the European Bureau for Lesser-Used Languages, , (the Cornish Language Board) and (the Cornish Language Fellowship).
There are ceremonies, some ancient, some modern, that use the language or are entirely in the language.
=== Cultural events ===
Cornwall has had cultural events associated with the language, including the international Celtic Media Festival, hosted in St Ives in 1997. The Old Cornwall Society has promoted the use of the language at events and meetings. Two examples of ceremonies that are performed in both the English and Cornish languages are Crying the Neck and the annual mid-summer bonfires.
Since 1969, there have been three full performances of the Ordinalia, originally written in the Cornish language, the most recent of which took place at the plen-an-gwary in St Just in September 2021. While significantly adapted from the original, as well as using mostly English-speaking actors, the plays used sizable amounts of Cornish, including a character who spoke only in Cornish and another who spoke both English and Cornish. The event drew thousands over two weeks, also serving as a celebration of Celtic culture. The next production, scheduled for 2024, could, in theory, be entirely in Cornish, without English, if assisted by a professional linguist.
Outside of Cornwall, efforts to revive the Cornish language and culture through community events are occurring in Australia. A biennial festival, Kernewek Lowender, takes place in South Australia, where both cultural displays and language lessons are offered.
=== Study and teaching ===
Cornish is taught in some schools; it was previously taught at degree level at the University of Wales, though the only existing course in the language at university level is as part of a course in Cornish studies at the University of Exeter. In March 2008 a course in the language was started as part of the Celtic Studies curriculum at the University of Vienna, Austria.
The University of Cambridge offers courses in Cornish through its John Trim Resources Centre, which is part of the university's Language Centre. In addition, the Department of Anglo-Saxon, Norse and Celtic (which is part of the Faculty of English) also carries out research into the Cornish language.
In 2015 a university-level course aiming at encouraging and supporting practitioners working with young children to introduce the Cornish language into their settings was launched. The Cornish Language Practice Project (Early Years) is a level 4 course approved by Plymouth University and run at Cornwall College. The course is not a Cornish-language course but students will be assessed on their ability to use the Cornish language constructively in their work with young children. The course will cover such topics as Understanding Bilingualism, Creating Resources and Integrating Language and Play, but the focus of the language provision will be on Cornish. A non-accredited specialist Cornish-language course has been developed to run alongside the level 4 course for those who prefer tutor support to learn the language or develop their skills for use with young children.
Cornwall's first Cornish-language crèche, , was established in 2010 at Cornwall College, Camborne. The nursery teaches children aged between two and five years alongside their parents to ensure the language is also spoken in the home.
Classes and conversation groups for adults are available at several locations in Cornwall as well as in London, Cardiff and Bristol. Since the onset of the COVID-19 pandemic a number of conversation groups entitled have been held online, advertised through Facebook and other media. A surge in interest, not just from people in Cornwall but from all over the world, has meant that extra classes have been organised.
=== Cornish studies ===
William Scawen produced a manuscript on the declining Cornish language that continually evolved until he died in 1689, aged 89. He was one of the first to realise the language was dying out and wrote detailed manuscripts which he started working on when he was 78. The only version that was ever published was a short first draft but the final version, which he worked on until his death, is a few hundred pages long. At the same time a group of scholars led by John Keigwin (nephew of William Scawen) of Mousehole tried to preserve and further the Cornish language and chose to write in Cornish. One of their number, Nicholas Boson, tells how he had been discouraged from using Cornish to servants by his mother. This group left behind a large number of translations of parts of the Bible, proverbs and songs. They were contacted by the Welsh linguist Edward Lhuyd, who came to Cornwall to study the language.
Early Modern Cornish was the subject of a study published by Lhuyd in 1707, and differs from the medieval language in having a considerably simpler structure and grammar. Such differences included sound changes and more frequent use of auxiliary verbs. The medieval language also possessed two additional tenses for expressing past events and an extended set of possessive suffixes.
John Whitaker, the Manchester-born rector of Ruan Lanihorne, studied the decline of the Cornish language. In his 1804 work the Ancient Cathedral of Cornwall he concluded that: "[T]he English Liturgy, was not desired by the Cornish, but forced upon them by the tyranny of England, at a time when the English language was yet unknown in Cornwall. This act of tyranny was at once gross barbarity to the Cornish people, and a death blow to the Cornish language."
Robert Williams published the first comprehensive Cornish dictionary in 1865, the . As a result of the discovery of additional ancient Cornish manuscripts, 2000 new words were added to the vocabulary by Whitley Stokes in A Cornish Glossary. William C. Borlase published Proverbs and Rhymes in Cornish in 1866 while A Glossary of Cornish Names was produced by John Bannister in the same year. Frederick Jago published his English–Cornish Dictionary in 1882.
In 2002, the Cornish language gained new recognition because of the European Charter for Regional and Minority Languages. Conversely, along with government provision was the governmental basis of "New Public Management", measuring quantifiable results as means of determining effectiveness. This put enormous pressure on finding a single orthography that could be used in unison. The revival of Cornish required extensive rebuilding. The Cornish orthographies that were reconstructed may be considered versions of Cornish because they are not traditional sociolinguistic variations. In the middle-to-late twentieth century, the debate over Cornish orthographies angered more people because several language groups received public funding. This caused other groups to sense favouritism as playing a role in the debate.
A governmental policymaking structure called New Public Management (NPM) has helped the Cornish language by managing public life of the Cornish language and people. In 2007, the Cornish Language Partnership MAGA represents separate divisions of government and their purpose is to further enhance the Cornish Language Developmental Plan. MAGA established an Ad-Hoc Group, which resulted in three orthographies being presented. The relations for the Ad-Hoc Group were to obtain consensus among the three orthographies and then develop a "single written form". The result was creating a new form of Cornish, which had to be natural for both new learners and skilled speakers.
=== Literature ===
==== Recent Modern Cornish literature ====
In 1981, the Breton library edited (Passion of our lord), a 15th-century Cornish poem. The first complete translation of the Bible into Cornish, translated from English, was published in 2011. Another Bible translation project translating from original languages is underway. The New Testament and Psalms were made available online on YouVersion (Bible.com) and Bibles.org in July 2014 by the Bible Society.
A few small publishers produce books in Cornish which are stocked in some local bookshops, as well as in Cornish branches of Waterstones and WH Smith, although publications are becoming increasingly available on the Internet. Printed copies of these may also be found from Amazon. The Truro Waterstones hosts the annual literary awards, established by to recognise publications relating to Cornwall or in the Cornish language. In recent years, a number of Cornish translations of literature have been published, including Alice's Adventures in Wonderland (2009), Around the World in Eighty Days (2009), Treasure Island (2010), The Railway Children (2012), Hound of the Baskervilles (2012), The War of the Worlds (2012), The Wind in the Willows (2013), Three Men in a Boat (2013), Alice in Wonderland and Through the Looking-Glass (2014), and A Christmas Carol (which won the 2012 award for Cornish Language books), as well as original Cornish literature such as (The Lyonesse Stone) by Craig Weatherhill. Literature aimed at children is also available, such as (Where's Spot?), (The Beast of Bodmin Moor), three Topsy and Tim titles, two Tintin titles and (Briallen and the Alien), which won the 2015 award for Cornish Language books for children. In 2014 , Nicholas Williams's translation of J. R. R. Tolkien's The Hobbit, was published.
is a monthly magazine published entirely in the Cornish language. Members contribute articles on various subjects. The magazine is produced by Graham Sandercock who has been its editor since 1976.
=== Media ===
In 1983 BBC Radio Cornwall started broadcasting around two minutes of Cornish every week. In 1987, however, they gave over 15 minutes of airtime on Sunday mornings for a programme called ('Holdall'), presented by John King, running until the early 1990s. It was eventually replaced with a five-minute news bulletin called ('The News'). The bulletin was presented every Sunday evening for many years by Rod Lyon, then Elizabeth Stewart, and currently a team presents in rotation. Pirate FM ran short bulletins on Saturday lunchtimes from 1998 to 1999. In 2006, Matthew Clarke who had presented the Pirate FM bulletin, launched a web-streamed news bulletin called ('Weekly News'), which in 2008 was merged into a new weekly magazine podcast (RanG).
Cornish television shows have included a 1982 series by Westward Television with each episode containing a three-minute lesson in Cornish. , an eight-episode series produced by Television South West and broadcast between June and July 1984, later on S4C from May to July 1985, and as a schools programme in 1986. Also by Television South West were two bilingual programmes on Cornish Culture called .
In 2016 Kelly's Ice Cream of Bodmin introduced a light hearted television commercial in the Cornish language and this was repeated in 2017.
The first episode from the third season of the US television program Deadwood features a conversation between miners, purportedly in the Cornish language, but really in Irish. One of the miners is then shot by thugs working for businessman George Hearst who justify the murder by saying, "He come at me with his foreign gibberish."
A number of Cornish language films have been made, including Hwerow Hweg, a 2002 drama film written and directed by Hungarian film-maker Antal Kovacs and Trengellick Rising, a short film written and directed by Guy Potter.
Screen Cornwall works with Cornwall Council to commission a short film in the Cornish language each year, with their FilmK competition. Their website states "FylmK is an annual contemporary Cornish language short film competition, producing an imaginative and engaging film, in any genre, from distinctive and exciting filmmakers".
A monthly half-hour online TV show began in 2017 called (The Month). It contained news items about cultural events and more mainstream news stories all through Cornish. It also ran a cookery segment called "" ('Esther's Kitchen').
=== Music ===
English composer Peter Warlock wrote a Christmas carol in Cornish (setting words by Henry Jenner). The Cornish electronic musician Aphex Twin has used Cornish names for track titles, most notably on his Drukqs album.
Several traditional Cornish folk songs have been collected and can be sung to various tunes. These include "", "", and "".
In 2018, the singer Gwenno Saunders released an album in Cornish, entitled , saying: "I speak Cornish with my son: if you're comfortable expressing yourself in a language, you want to share it."
=== Place-names and surnames ===
The Cornish language features in the toponymy of Cornwall, with a significant contrast between English place-names prevalent in eastern Cornwall and Cornish place-names to the west of the Camel-Fowey river valleys, where English place-names are much less common. Hundreds of Cornish family names have an etymology in the Cornish language, the majority of which are derived from Cornish place-names. Long before the agreement of the Standard Written Form of Cornish in the 21st century, Late Cornish orthography in the Early Modern period usually followed Welsh to English transliteration, phonetically rendering C for K, I for Y, U for W, and Z for S. This meant that place names were adopted into English with spellings such as 'Porthcurno' and 'Penzance'; they are written and in the Standard Written Form of Cornish, agreed upon in 2008. Likewise words such as ('island') can be found spelled as as at Ince Castle. These apparent mistransliterations can, however, reveal an insight into how names and places were actually pronounced, explaining, for example, how anglicised is still pronounced [ˈlansǝn] with emphasis on the first element, perhaps from Cornish , though the Concise Oxford Dictionary of English Place-Names considers this unlikely.
The following tables present some examples of Cornish place names and surnames and their anglicised versions:
== Samples ==
From the Universal Declaration of Human Rights:
From , the Cornish anthem:
From the wrestler's oath:
|
[
"Meriasek",
"Old Welsh",
"Boethius",
"Truro",
"Languages in the United Kingdom",
"Cornish alphabet",
"grammatical gender",
"Breton language",
"Bodmin",
"Lyonesse",
"Ælfric of Eynsham",
"eth",
"pre-stopped consonant",
"Qualifications and Credit Framework",
"Hagiography",
"Morphophonology",
"Agan Tavas",
"Manumission",
"preposition",
"Bodmin manumissions",
"List of topics related to Cornwall",
"extinct language",
"Celtic Media Festival",
"palatalization (sound change)",
"House of Tudor",
"St Allen",
"Celtic Revival",
"Three Men in a Boat",
"An Awhesyth",
"Proto-Celtic language",
"Bert Biscoe",
"Le Kov",
"last speaker of the Cornish language",
"Brittonic languages",
"Pirate FM",
"Cornish people",
"Genesis creation narrative",
"Gorsedh Kernow",
"Plymouth University",
"grammatical mood",
"assibilation",
"Launceston, Cornwall",
"Great Britain",
"second language",
"Devon",
"John Davey (Cornish speaker)",
"Department of Anglo-Saxon, Norse and Celtic, University of Cambridge",
"Henry VII of England",
"Ken George",
"Saint-Pol-de-Léon",
"vernacular",
"Language Problems and Language Planning",
"Archæologia Britannica",
"Southwestern Brittonic languages",
"Yogh",
"Rod Lyon",
"Penwith",
"Subject–verb–object",
"grammatical case",
"London",
"Manx language",
"Alice's Adventures in Wonderland",
"Ellery (surname)",
"Hilary (name)",
"St Stephen",
"Linguistic reconstruction",
"Nicholas Udall",
"Glottolog",
"Pearson Longman",
"Second language",
"Falmouth, Cornwall",
"Kenneth H. Jackson",
"Latin language",
"Marriage Act 1949",
"Western Brittonic languages",
"Celtic League (political organisation)",
"Michael Everson",
"Critically endangered language",
"De Gruyter",
"Cornish Bible",
"Cornwall Council",
"Framework Convention for the Protection of National Minorities",
"lenition",
"Boswednack",
"The Adventures of Tintin",
"European Charter for Regional or Minority Languages",
"Mark Stoyle",
"S4C",
"Consolation of Philosophy",
"Anglo-Saxon settlement of Britain",
"Vocabularium Cornicum",
"Hwerow Hweg",
"Welsh Academic Press",
"Tewdwr Mawr",
"Henry VIII of England",
"Peter Berresford Ellis",
"Act of Uniformity 1549",
"Atlas of the World's Languages in Danger",
"Newquay, Cornwall",
"manuscript",
"UNESCO",
"J. R. R. Tolkien",
"The Daily Telegraph",
"Plymouth Herald",
"Atlas Obscura",
"Latin script",
"European Bureau for Lesser-Used Languages",
"plen-an-gwary",
"Treasure Island",
"stratum (linguistics)",
"Drukqs",
"Early Modern",
"Whitley Stokes (scholar)",
"Millennium Commission",
"Kesva an Taves Kernewek",
"Pictish",
"Kernewek Kemmyn",
"Teague (disambiguation)",
"Redruth",
"The Wind in the Willows",
"Bewnans Ke",
"Robert Morton Nance",
"verb–subject–object",
"Holdall",
"John Hobson Matthews",
"Irish language",
"Welsh language",
"language revitalization",
"Delkiow Sivy",
"Celtic nations",
"Institute of Cornish Studies",
"The Guardian",
"Jagiellonian University Press",
"circumflex",
"Andrew Breeze",
"Ruan Lanihorne",
"Philology",
"Thorn (letter)",
"Ancestry.com",
"grammatical tense",
"St Austell",
"iarchive:cu31924026878334",
"John Keigwin",
"Craig Weatherhill",
"List of Celtic-language media",
"The Cornishman (newspaper)",
"Edinburgh University Press",
"Cornwall College (England)",
"Fred W. P. Jago",
"Nicholas Williams (poet)",
"Radyo an Gernewegva",
"University of Cambridge",
"Brittany",
"music of Cornwall",
"The War of the Worlds",
"Kowethas an Yeth Kernewek",
"St Levan",
"Cornish language revival",
"Cornish surnames",
"Celtic Congress",
"Office for National Statistics",
"phonemic orthography",
"Grammatical person",
"Taylor & Francis",
"Crowan",
"Proto-Indo-European language",
"Cranken Rhyme",
"Standard Written Form",
"Cornish rebellion of 1497",
"St Just in Penwith",
"John Wiley & Sons",
"Pascon agan Arluth",
"Last speaker of the Cornish language",
"Liskeard",
"The Times",
"consonant mutation",
"Project Gutenberg",
"Cumbria",
"independent film",
"iarchive:handbookofcornis00jennuoft",
"Cornish diaspora",
"dental stop",
"Commission of the European Communities",
"Edward Lhuyd",
"Prayer Book Rebellion",
"Modern Cornish",
"Trevithick",
"Anglo-Cornish",
"Common Brittonic",
"BBC",
"Penzance",
"Kenneth MacKinnon",
"Omniglot",
"Around the World in Eighty Days",
"Richard Carew (antiquary)",
"Cornish Language Partnership",
"Oxford University Press",
"Goldsworthy (name)",
"Brill Publishing",
"Lenition",
"periphrasis",
"Verb–subject–object",
"Cornish wrestling",
"Provection",
"sheep",
"United Kingdom",
"University of Wales",
"Trengellick Rising",
"John Whitaker (historian)",
"William Scawen",
"England",
"Kerrier",
"Insular Celtic languages",
"rememberer",
"The Hobbit",
"Roman Britain",
"inflected language",
"Henry Jenner",
"rhotacism",
"Philip Nichols",
"Comparative method",
"Wales",
"Cornish Language Office",
"British Iron Age",
"Dolly Pentreath",
"Cambridge University Press",
"Television South West",
"Ordinalia",
"Ince Castle",
"Penryn, Cornwall",
"British Latin",
"Goidelic languages",
"The Cornish Language Council",
"Western Morning News",
"Scottish Gaelic",
"St Ives, Cornwall",
"article (grammar)",
"sedition",
"Celts (modern)",
"Westward Television",
"Pascoe",
"Universal Declaration of Human Rights",
"Daines Barrington",
"Cardiff",
"Glasney College",
"Spirantization",
"Thomas Cranmer",
"Beunans Meriasek",
"Hound of the Baskervilles",
"Topsy and Tim",
"toponymy",
"Gwenno Saunders",
"Crying the Neck",
"BBC News Online",
"Cornwall",
"Porthcurno",
"Anthony Kingston",
"inflected preposition",
"BBC News",
"Blackheath, London",
"Sardine",
"Anthony Fletcher",
"The Independent",
"Southwestern Brittonic language",
"first language",
"Richard Gendall",
"Firth of Forth",
"Crows-an-Wra",
"Kernowek Standard",
"Camborne",
"Battle of Deorham",
"Nicholas Boson",
"day care",
"YouVersion",
"Language revival",
"The Railway Children",
"New Testament",
"Cumbric language",
"masterpiece",
"verbal noun",
"Aphex Twin",
"Tremaine",
"A Christmas Carol",
"Andrew Boorde",
"dental fricative",
"WalesOnline",
"Chenoweth",
"Old Cornwall Society",
"Edmund Bonner",
"Joseph Loth",
"Google Books",
"Routledge",
"University of Exeter",
"Bible translations into Cornish",
"ABC-CLIO",
"grammatical number",
"Peter Warlock",
"BBC Radio Cornwall",
"University of Exeter Press",
"Guy Potter",
"Spot the Dog",
"Gloss (annotation)",
"University of Vienna",
"Angwin (disambiguation)",
"Cumbric",
"wynn",
"Quiberon",
"Bristol",
"De raris fabulis",
"grammatical conjugation",
"Saint Kea",
"George Hearst",
"Gaelic revival",
"Latin",
"Bro Goth agan Tasow",
"Passive speaker (language)",
"Celtic languages",
"Deadwood (TV series)",
"Wessex",
"Journal of British Studies",
"Celtic language family",
"Veryan",
"multilingualism",
"Unified Cornish",
"An Gannas",
"semi-speaker",
"Cornish literature",
"Indo-European languages",
"mutually intelligible",
"Psalms"
] |
6,132 |
Complexity theory
|
Complexity theory may refer to:
==Science and technology==
Computational complexity theory, a field in theoretical computer science and mathematics
Complex systems theory, the study of the complexity in context of complex systems
Assembly theory, a way of characterizing extraterrestrial molecular complexity to assess the probability of the presence of life
==Other uses==
Complexity economics, the application of complexity theory to economics
Complexity theory and organizations, the application of complexity theory to strategy
|
[
"Computational complexity theory",
"complex systems",
"Complexity (disambiguation)",
"Complexity theory and organizations",
"Systems thinking",
"Complex adaptive system",
"Complexity economics",
"Assembly theory",
"Complex network",
"Computational complexity",
"Systems theory"
] |
6,134 |
Charybdis
|
Charybdis (; , ; , ) is a sea monster in Greek mythology. Charybdis, along with the sea monster Scylla, appears as a challenge to epic characters such as Odysseus, Jason, and Aeneas. Scholarship locates her in the Strait of Messina.
The idiom "between Scylla and Charybdis" has come to mean being forced to choose between two similarly dangerous situations.
==Description==
The sea monster Charybdis was believed to live under a small rock on one side of a narrow channel. Opposite her was Scylla, another sea monster, who lived inside a much larger rock. The sides of the strait were within an arrow-shot of each other, and sailors attempting to avoid one of them would come in reach of the other. To be "between Scylla and Charybdis" therefore means to be presented with two opposite dangers, the task being to find a route that avoids both. Three times a day, Charybdis swallowed a huge amount of water, before belching it back out again, creating large whirlpools capable of dragging a ship underwater. In some variations of the story, Charybdis was simply a large whirlpool instead of a sea monster.
Through the descriptions of Greek mythical chroniclers and Greek historians such as Thucydides, modern scholars generally agree that Charybdis was said to have been located in the Strait of Messina, off the coast of Sicily and opposite a rock on the mainland identified with Scylla. A whirlpool does exist there, caused by currents meeting, but it is dangerous only to small craft in extreme conditions.
== Family ==
Another myth makes Charybdis the daughter of Poseidon and Gaia and living as a loyal servant to her father.
==Mythology==
=== Origin ===
Charybdis aided her father Poseidon in his feud with her paternal uncle Zeus and, as such, helped him engulf lands and islands in water. Zeus, angry over the land she stole from him, sent her to the bottom of the sea with a thunderbolt; from the sea bed, she drank the water from the sea thrice a day, creating whirlpools. She lingered on a rock with Scylla facing her directly on another rock, making a strait.
In some myths, Charybdis was a voracious woman who stole oxen from Heracles, and was hurled by the thunderbolt of Zeus into the sea, where she retained her voracious nature.
===Jason and the Argonauts===
The Argonauts were able to avoid both dangers because Hera ordered the Nereid Thetis to guide them through the perilous passage.
===The Aeneid===
In the Aeneid, the Trojans are warned by Helenus of Scylla and Charybdis, and are advised to avoid them by sailing around Pachynus point (Cape Passero) rather than risk the strait. Later, however, they find themselves passing Etna, and have to row for their lives to escape Charybdis.
===Aesop===
Aristotle mentions in his Meteorologica that Aesop once teased a ferryman by telling him a myth concerning Charybdis. With one gulp of the sea, she brought the mountains to view; islands appeared after the next. The third is yet to come and will dry the sea altogether, thus depriving the ferryman of his livelihood.
|
[
"between Scylla and Charybdis",
"Poseidon",
"Gaia (mythology)",
"Thucydides",
"Thetis",
"Jason",
"Dictionary of Greek and Roman Biography and Mythology",
"Aesop and the Ferryman",
"Argonautica",
"Helenus",
"Argonauts",
"History of the Peloponnesian War",
"sea monster",
"Homer",
"coast",
"Odyssey",
"Cape Passero",
"Charybdis Icefalls",
"Aeneas",
"whirlpool",
"Sicily",
"Aesop",
"Scholia",
"Nereid",
"Aristotle",
"Hera",
"Odysseus",
"Strait of Messina",
"Aeneid",
"Maurus Servius Honoratus",
"Greek mythology",
"Scylla",
"Mount Etna",
"Virgil",
"William Smith (lexicographer)",
"Apollonius of Rhodes",
"Heracles"
] |
6,136 |
Carbon monoxide
|
{{Chembox
|verifiedrevid = 477004453
|ImageFileL1 = Carbon-monoxide-3D-balls.png
|ImageNameL1 = Ball-and-stick model of carbon monoxide
|ImageFileR1 = Carbon-monoxide-3D-vdW.png
|ImageNameR1 = Spamodel of carbon monoxide
|ImageFile2 = Carbon monoxide 2D.svg
|ImageSize2 = 170px
|ImageName2 = model of carbon monoxide
|ImageClass2 = skin-invert-image
|IUPACName= Carbon monoxide
|OtherNames = Carbonic oxide gasCarbon protoxideOxide of carbonProtoxide of carbonCarbonous oxideCarbonous acid gasCarbon(II) oxideBreath of carbonOxygenated carbonCarbateCarbonylWater gasHydrocarbon gasFuel gasRauchgasCarbonic inflammable airHeavy inflammable airWhite dampFire DampPowder GasIlluminating gasDowson gasMond gasPower gasProducer gasBlast furnace gasCoal gasPhlogistonCar gas
|Section1 =
|Section2 =
|Section3 =
|Section4 =
|Section5 = {{Chembox Hazards
|MainHazards = Poisonous by inhalation
|NFPA-H = 3
|NFPA-F = 4
|NFPA-R = 0
|GHSPictograms =
|GHSSignalWord = Danger
|HPhrases =
|PPhrases =
|FlashPtC = −191
|AutoignitionPtC = 609
|ExploLimits = 12.5–74.2%
|NIOSH_ref =
|PEL = TWA 50 ppm (55 mg/m3)
|REL =
|IDLH = 1200 ppm
|LC50 =
|LCLo =
Carbon monoxide (chemical formula CO) is a poisonous, flammable gas that is colorless, odorless, tasteless, and slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simplest carbon oxide. In coordination complexes, the carbon monoxide ligand is called carbonyl. It is a key ingredient in many processes in industrial chemistry.
The most common source of carbon monoxide is the partial combustion of carbon-containing compounds. Numerous environmental and biological sources generate carbon monoxide. In industry, carbon monoxide is important in the production of many compounds, including drugs, fragrances, and fuels.
Indoors CO is one of the most acutely toxic contaminants affecting indoor air quality. CO may be emitted from tobacco smoke and generated from malfunctioning fuel burning stoves (wood, kerosene, natural gas, propane) and fuel burning heating systems (wood, oil, natural gas) and from blocked flues connected to these appliances. Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. This bond length is consistent with a triple bond, as in molecular nitrogen (), which has a similar bond length (109.76 pm) and nearly the same molecular mass. Carbon–oxygen double bonds are significantly longer, 120.8 pm in formaldehyde, for example. The boiling point (82 K) and melting point (68 K) are very similar to those of (77 K and 63 K, respectively). The bond-dissociation energy of 1072 kJ/mol is stronger than that of (942 kJ/mol) and represents the strongest chemical bond known.
The ground electronic state of carbon monoxide is a singlet state since there are no unpaired electrons.
===Bonding and dipole moment===
The strength of the bond in carbon monoxide is indicated by the high frequency of its vibration, 2143 cm−1. For comparison, organic carbonyls such as ketones and esters absorb at around 1700 cm−1.
Carbon and oxygen together have a total of 10 electrons in the valence shell. Following the octet rule for both carbon and oxygen, the two atoms form a triple bond, with six shared electrons in three bonding molecular orbitals, rather than the usual double bond found in organic carbonyl compounds. Since four of the shared electrons come from the oxygen atom and only two from carbon, one bonding orbital is occupied by two electrons from oxygen, forming a dative or dipolar bond. This causes a C←O polarization of the molecule, with a small negative charge on carbon and a small positive charge on oxygen. The other two bonding orbitals are each occupied by one electron from carbon and one from oxygen, forming (polar) covalent bonds with a reverse C→O polarization since oxygen is more electronegative than carbon. In the free carbon monoxide molecule, a net negative charge δ− remains at the carbon end and the molecule has a small dipole moment of 0.122 D.
The molecule is therefore asymmetric: oxygen is more electron dense than carbon and is also slightly positively charged compared to carbon being negative.
Carbon monoxide has a computed fractional bond order of 2.6, indicating that the "third" bond is important but constitutes somewhat less than a full bond. Thus, in valence bond terms, is the most important structure, while :C=O is non-octet, but has a neutral formal charge on each atom and represents the second most important resonance contributor. Because of the lone pair and divalence of carbon in this resonance structure, carbon monoxide is often considered to be an extraordinarily stabilized carbene. Isocyanides are compounds in which the O is replaced by an NR (R = alkyl or aryl) group and have a similar bonding scheme.
If carbon monoxide acts as a ligand, the polarity of the dipole may reverse with a net negative charge on the oxygen end, depending on the structure of the coordination complex.
See also the section "Coordination chemistry" below.
===Bond polarity and oxidation state===
Theoretical and experimental studies show that, despite the greater electronegativity of oxygen, the dipole moment points from the more-negative carbon end to the more-positive oxygen end. The three bonds are in fact polar covalent bonds that are strongly polarized. The calculated polarization toward the oxygen atom is 71% for the σ-bond and 77% for both π-bonds.
The oxidation state of carbon in carbon monoxide is +2 in each of these structures. It is calculated by counting all the bonding electrons as belonging to the more electronegative oxygen. Only the two non-bonding electrons on carbon are assigned to carbon. In this count, carbon then has only two valence electrons in the molecule compared to four in the free atom.
==Occurrence==
Carbon monoxide occurs in many environments, usually in trace leveles. Photochemical degradation of plant matter for example generates an estimated 60 million tons/year. Typical concentrations in parts per million are as follows:
{| class="wikitable"
|+Composition of dry atmosphere, by volume
|-
! Concentration (ppmv)
! Source
|-
| 0.1
| Natural atmosphere level (MOPITT)
|-
| 0.5–5
| Average level in homes
|-
| 5–15
| Near properly adjusted gas stoves in homes, modern vehicle exhaust emissions
|-
| 17
| Atmosphere of Venus
|-
| 100–200
| Exhaust from automobiles in the Mexico City central area in 1975
|-
| 700
| Atmosphere of Mars
|-
| •OH) that would otherwise destroy methane. Through natural processes in the atmosphere, it is oxidized to carbon dioxide and ozone. Carbon monoxide is short-lived in the atmosphere (with an average lifetime of about one to two months), and spatially variable in concentration.
Due to its long lifetime in the mid-troposphere, carbon monoxide is also used as a tracer for pollutant plumes.
=== Astronomy ===
Beyond Earth, carbon monoxide is the second-most common diatomic molecule in the interstellar medium, after molecular hydrogen. Because of its asymmetry, this polar molecule produces far brighter spectral lines than the hydrogen molecule, making CO much easier to detect. Interstellar CO was first detected with radio telescopes in 1970. It is now the most commonly used tracer of molecular gas in general in the interstellar medium of galaxies, as molecular hydrogen can only be detected using ultraviolet light, which requires space telescopes. Carbon monoxide observations provide much of the information about the molecular clouds in which most stars form.
Beta Pictoris, the second brightest star in the constellation Pictor, shows an excess of infrared emission compared to normal stars of its type, which is caused by large quantities of dust and gas (including carbon monoxide) near the star.
In the atmosphere of Venus carbon monoxide occurs as a result of the photodissociation of carbon dioxide by electromagnetic radiation of wavelengths shorter than 169 nm. It has also been identified spectroscopically on the surface of Neptune's moon Triton.
Solid carbon monoxide is a component of comets. The volatile or "ice" component of Halley's Comet is about 15% CO. At room temperature and at atmospheric pressure, carbon monoxide is actually only metastable (see Boudouard reaction) and the same is true at low temperatures where CO and are solid, but nevertheless it can exist for billions of years in comets. There is very little CO in the atmosphere of Pluto, which seems to have been formed from comets. This may be because there is (or was) liquid water inside Pluto.
Carbon monoxide can react with water to form carbon dioxide and hydrogen:
This is called the water-gas shift reaction when occurring in the gas phase, but it can also take place (very slowly) in an aqueous solution.
If the hydrogen partial pressure is high enough (for instance in an underground sea), formic acid will be formed:
These reactions can take place in a few million years even at temperatures such as found on Pluto.
== Pollution and health effects ==
=== Urban pollution ===
Carbon monoxide is a temporary atmospheric pollutant in some urban areas, chiefly from the exhaust of internal combustion engines (including vehicles, portable and back-up generators, lawnmowers, power washers, etc.), but also from incomplete combustion of various other fuels (including wood, coal, charcoal, oil, paraffin, propane, natural gas, and trash).
Large CO pollution events can be observed from space over cities.
==== Role in ground level ozone formation ====
Carbon monoxide is, along with aldehydes, part of the series of cycles of chemical reactions that form photochemical smog. It reacts with hydroxyl radical (•OH) to produce a radical intermediate •HOCO, which rapidly transfers its radical hydrogen to to form peroxy radical (•) and carbon dioxide (). Peroxy radical subsequently reacts with nitrogen oxide (NO) to form nitrogen dioxide () and hydroxyl radical. gives O(3P) via photolysis, thereby forming following reaction with .
Since hydroxyl radical is formed during the formation of , the balance of the sequence of chemical reactions starting with carbon monoxide and leading to the formation of ozone is:
(where hν refers to the photon of light absorbed by the molecule in the sequence)
Although the creation of is the critical step leading to low level ozone formation, it also increases this ozone in another, somewhat mutually exclusive way, by reducing the quantity of NO that is available to react with ozone.
=== Indoor air pollution ===
Carbon monoxide is one of the most acutely toxic indoor air contaminants. Carbon monoxide may be emitted from tobacco smoke and generated from malfunctioning fuel burning stoves (wood, kerosene, natural gas, propane) and fuel burning heating systems (wood, oil, natural gas) and from blocked flues connected to these appliances. Appliance malfunction may be due to faulty installation or lack of maintenance and proper use. The idiom "Canary in the coal mine" pertained to an early warning of a carbon monoxide presence.
===Health effects===
Carbon monoxide poisoning is the most common type of fatal air poisoning in many countries. Acute exposure can also lead to long-term neurological effects such as cognitive and behavioural changes. Severe CO poisoning may lead to unconsciousness, coma and death. Chronic exposure to low concentrations of carbon monoxide may lead to lethargy, headaches, nausea, flu-like symptoms and neuropsychological and cardiovascular issues.
== Chemistry ==
Carbon monoxide has a wide range of functions across all disciplines of chemistry. The four premier categories of reactivity involve metal-carbonyl catalysis, radical chemistry, cation and anion chemistries.
===Coordination chemistry===
Most metals form coordination complexes containing covalently attached carbon monoxide. These derivatives, which are called metal carbonyls, tend to be more robust when the metal is in lower oxidation states. For example iron pentacarbonyl () is an air-stable, distillable liquid. Nickel carbonyl is a metal carbonyl complex that forms by the direct combination of carbon monoxide with the metal:
(1 bar, 55 °C)
These volatile complexes are often highly toxic. Some metal–CO complexes are prepared by decarbonylation of organic solvents, not from CO. For instance, iridium trichloride and triphenylphosphine react in boiling 2-methoxyethanol or DMF to afford .
As a ligand, CO binds through carbon, forming a kind of triple bond. The lone pair on the carbon atom donates electron density to form a M-CO sigma bond. The two π* orbitals on CO bind to filled metal orbitals. The effect is related to the Dewar-Chatt-Duncanson model. The effects of the quasi-triple M-C bond is reflected in the infrared spectrum of these complexes. Whereas free CO vibrates at 2143 cm-1, its complexes tend to absorb near 1950 cm-1.
===Organic and main group chemistry===
In the presence of strong acids, alkenes react with carboxylic acids. Hydrolysis of this species (an acylium ion) gives the carboxylic acid, a net process known as the Koch–Haaf reaction. In the Gattermann–Koch reaction, arenes are converted to benzaldehyde derivatives in the presence of CO, , and HCl.
A mixture of hydrogen gas and CO reacts with alkenes to give aldehydes. The process requires the presence of metal catalysts.
With main group reagents, CO undergoes several noteworthy reactions. Chlorination of CO is the industrial route to the important compound phosgene. With borane CO forms the adduct , which is isoelectronic with the acylium cation . CO reacts with sodium to give products resulting from C−C coupling such as sodium acetylenediolate . It reacts with molten potassium to give a mixture of an organometallic compound, potassium acetylenediolate , potassium benzenehexolate , and potassium rhodizonate .
The compounds cyclohexanehexone or triquinoyl () and cyclopentanepentone or leuconic acid (), which so far have been obtained only in trace amounts, can be regarded as polymers of carbon monoxide. At pressures exceeding 5 GPa, carbon monoxide converts to polycarbonyl, a solid polymer that is metastable at atmospheric pressure but is explosive.
==== Laboratory preparation ====
Carbon monoxide is conveniently produced in the laboratory by the dehydration of formic acid or oxalic acid, for example with concentrated sulfuric acid. Another method is heating an intimate mixture of powdered zinc metal and calcium carbonate, which releases CO and leaves behind zinc oxide and calcium oxide:
Silver nitrate and iodoform also afford carbon monoxide:
Finally, metal oxalate salts release CO upon heating, leaving a carbonate as byproduct:
== Production ==
Thermal combustion is the most common source for carbon monoxide. Carbon monoxide is produced from the partial oxidation of carbon-containing compounds; it forms when there is not enough oxygen to produce carbon dioxide (), such as when operating a stove or an internal combustion engine in an enclosed space.
A large quantity of CO byproduct is formed during the oxidative processes for the production of chemicals. For this reason, the process off-gases have to be purified.
Many methods have been developed for carbon monoxide production.
===Industrial production===
A major industrial source of CO is producer gas, a mixture containing mostly carbon monoxide and nitrogen, formed by combustion of carbon in air at high temperature when there is an excess of carbon. In an oven, air is passed through a bed of coke. The initially produced equilibrates with the remaining hot carbon to give CO. The reaction of with carbon to give CO is described as the Boudouard reaction. Above 800 °C, CO is the predominant product:
(ΔHr = 170 kJ/mol)
Another source is "water gas", a mixture of hydrogen and carbon monoxide produced via the endothermic reaction of steam and carbon:
(ΔHr = 131 kJ/mol)
Other similar "synthesis gases" can be obtained from natural gas and other fuels.
Carbon monoxide can also be produced by high-temperature electrolysis of carbon dioxide with solid oxide electrolyzer cells. One method developed at DTU Energy uses a cerium oxide catalyst and does not have any issues of fouling of the catalyst.
Carbon monoxide is also a byproduct of the reduction of metal oxide ores with carbon, shown in a simplified form as follows:
MO + C → M + CO
Carbon monoxide is also produced by the direct oxidation of carbon in a limited supply of oxygen or air.
Since CO is a gas, the reduction process can be driven by heating, exploiting the positive (favorable) entropy of reaction. The Ellingham diagram shows that CO formation is favored over in high temperatures.
==Use==
===Chemical industry===
Carbon monoxide is an industrial gas that has many applications in bulk chemicals manufacturing. Large quantities of aldehydes are produced by the hydroformylation reaction of alkenes, carbon monoxide, and . Hydroformylation is coupled to the Shell higher olefin process to give precursors to detergents.
Phosgene, useful for preparing isocyanates, polycarbonates, and polyurethanes, is produced by passing purified carbon monoxide and chlorine gas through a bed of porous activated carbon, which serves as a catalyst. World production of this compound was estimated to be 2.74 million tonnes in 1989.
Methanol is produced by the hydrogenation of carbon monoxide. In a related reaction, the hydrogenation of carbon monoxide is coupled to C−C bond formation, as in the Fischer–Tropsch process where carbon monoxide is hydrogenated to liquid hydrocarbon fuels. This technology allows coal or biomass to be converted to diesel.
In the Cativa process, carbon monoxide and methanol react in the presence of a homogeneous iridium catalyst and hydroiodic acid to give acetic acid. This process is responsible for most of the industrial production of acetic acid.
===Metallurgy===
Carbon monoxide is a strong reductive agent and has been used in pyrometallurgy to reduce metals from ores since ancient times. Carbon monoxide strips oxygen off metal oxides, reducing them to pure metal in high temperatures, forming carbon dioxide in the process. Carbon monoxide is not usually supplied as is, in the gaseous phase, in the reactor, but rather it is formed in high temperature in presence of oxygen-carrying ore, or a carboniferous agent such as coke, and high temperature. The blast furnace process is a typical example of a process of reduction of metal from ore with carbon monoxide.
Likewise, blast furnace gas collected at the top of blast furnace, still contains some 10% to 30% of carbon monoxide, and is used as fuel on Cowper stoves and on Siemens-Martin furnaces on open hearth steelmaking.
===Proposed use as a rocket fuel ===
Carbon monoxide has been proposed for use as a fuel on Mars by NASA researcher Geoffrey Landis. Carbon monoxide/oxygen engines have been suggested for early surface transportation use as both carbon monoxide and oxygen can be straightforwardly produced from the carbon dioxide atmosphere of Mars by zirconia electrolysis, without using any Martian water resources to obtain hydrogen, which would be needed to make methane or any hydrogen-based fuel.
Landis also proposed manufacturing the fuel from the similar carbon dioxide atmosphere of Venus for a sample return mission, in combination with solar-powered UAVs and rocket balloon ascent.
==Biological and physiological properties==
===Physiology===
Carbon monoxide is a bioactive molecule which acts as a gaseous signaling molecule. It is naturally produced by many enzymatic and non-enzymatic pathways, Following the first report that carbon monoxide is a normal neurotransmitter in 1993, In many tissues, carbon monoxide acts as anti-inflammatory, vasodilatory, and encouragers of neovascular growth. In animal model studies, carbon monoxide reduced the severity of experimentally induced bacterial sepsis, pancreatitis, hepatic ischemia/reperfusion injury, colitis, osteoarthritis, lung injury, lung transplantation rejection, and neuropathic pain while promoting skin wound healing. Therefore, there is significant interest in the therapeutic potential of carbon monoxide becoming pharmaceutical agent and clinical standard of care.
====Medicine====
Studies involving carbon monoxide have been conducted in many laboratories throughout the world for its anti-inflammatory and cytoprotective properties. These properties have the potential to be used to prevent the development of a series of pathological conditions including ischemia reperfusion injury, transplant rejection, atherosclerosis, severe sepsis, severe malaria, or autoimmunity.
===Microbiology===
Microbiota may also utilize carbon monoxide as a gasotransmitter. Carbon monoxide sensing is a signaling pathway facilitated by proteins such as CooA. The scope of the biological roles for carbon monoxide sensing is still unknown.
The human microbiome produces, consumes, and responds to carbon monoxide. For example, in certain bacteria, carbon monoxide is produced via the reduction of carbon dioxide by the enzyme carbon monoxide dehydrogenase with favorable bioenergetics to power downstream cellular operations.
Carbon monoxide has certain antimicrobial properties which have been studied to treat against infectious diseases. The carbon monoxide combines with myoglobin to form carboxymyoglobin, a bright-cherry-red pigment. Carboxymyoglobin is more stable than the oxygenated form of myoglobin, oxymyoglobin, which can become oxidized to the brown pigment metmyoglobin. This stable red color can persist much longer than in normally packaged meat. Typical levels of carbon monoxide used in the facilities that use this process are between 0.4% and 0.5%. The process is currently unauthorized in many other countries, including Japan, Singapore, and the European Union.
=== Weaponization ===
In ancient history, Hannibal executed Roman prisoners with coal fumes during the Second Punic War.
==History==
=== Prehistory ===
Humans have maintained a complex relationship with carbon monoxide since first learning to control fire circa 800,000 BC. Early humans probably discovered the toxicity of carbon monoxide poisoning upon introducing fire into their dwellings. The early development of metallurgy and smelting technologies emerging circa 6,000 BC through the Bronze Age likewise plagued humankind from carbon monoxide exposure. Apart from the toxicity of carbon monoxide, indigenous Native Americans may have experienced the neuroactive properties of carbon monoxide through shamanistic fireside rituals.
Thomas Beddoes and James Watt recognized carbon monoxide (as hydrocarbonate) to brighten venous blood in 1793. Watt suggested coal fumes could act as an antidote to the oxygen in blood, and Beddoes and Watt likewise suggested hydrocarbonate has a greater affinity for animal fiber than oxygen in 1796. In 1854, Adrien Chenot similarly suggested carbon monoxide to remove the oxygen from blood and then be oxidized by the body to carbon dioxide. In a third major process, attributed to researchers at Monsanto, CO combines with methanol to give acetic acid. Most acetic acid is produced by the Cativa process. Hydroformylation and the acetic acid syntheses are two of myriad carbonylation processes.
|
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] |
6,138 |
Conjecture
|
In mathematics, a conjecture is a conclusion or a proposition that is proffered on a tentative basis without proof. Some conjectures, such as the Riemann hypothesis or Fermat's conjecture (now a theorem, proven in 1995 by Andrew Wiles), have shaped much of mathematical history as new areas of mathematics are developed in order to prove them.
==Resolution of conjectures==
===Proof===
Formal mathematics is based on provable truth. In mathematics, any number of cases supporting a universally quantified conjecture, no matter how large, is insufficient for establishing the conjecture's veracity, since a single counterexample could immediately bring down the conjecture. Mathematical journals sometimes publish the minor results of research teams having extended the search for a counterexample farther than previously done. For instance, the Collatz conjecture, which concerns whether or not certain sequences of integers terminate, has been tested for all integers up to 1.2 × 1012 (1.2 trillion). However, the failure to find a counterexample after extensive search does not constitute a proof that the conjecture is true—because the conjecture might be false but with a very large minimal counterexample.
Nevertheless, mathematicians often regard a conjecture as strongly supported by evidence even though not yet proved. That evidence may be of various kinds, such as verification of consequences of it or strong interconnections with known results.
A conjecture is considered proven only when it has been shown that it is logically impossible for it to be false. There are various methods of doing so; see methods of mathematical proof for more details.
One method of proof, applicable when there are only a finite number of cases that could lead to counterexamples, is known as "brute force": in this approach, all possible cases are considered and shown not to give counterexamples. In some occasions, the number of cases is quite large, in which case a brute-force proof may require as a practical matter the use of a computer algorithm to check all the cases. For example, the validity of the 1976 and 1997 brute-force proofs of the four color theorem by computer was initially doubted, but was eventually confirmed in 2005 by theorem-proving software.
When a conjecture has been proven, it is no longer a conjecture but a theorem. Many important theorems were once conjectures, such as the Geometrization theorem (which resolved the Poincaré conjecture), Fermat's Last Theorem, and others.
===Disproof===
Conjectures disproven through counterexample are sometimes referred to as false conjectures (cf. the Pólya conjecture and Euler's sum of powers conjecture). In the case of the latter, the first counterexample found for the n=4 case involved numbers in the millions, although it has been subsequently found that the minimal counterexample is actually smaller.
===Independent conjectures===
Not every conjecture ends up being proven true or false. The continuum hypothesis, which tries to ascertain the relative cardinality of certain infinite sets, was eventually shown to be independent from the generally accepted set of Zermelo–Fraenkel axioms of set theory. It is therefore possible to adopt this statement, or its negation, as a new axiom in a consistent manner (much as Euclid's parallel postulate can be taken either as true or false in an axiomatic system for geometry).
In this case, if a proof uses this statement, researchers will often look for a new proof that does not require the hypothesis (in the same way that it is desirable that statements in Euclidean geometry be proved using only the axioms of neutral geometry, i.e. without the parallel postulate). The one major exception to this in practice is the axiom of choice, as the majority of researchers usually do not worry whether a result requires it—unless they are studying this axiom in particular.
==Conditional proofs==
Sometimes, a conjecture is called a hypothesis when it is used frequently and repeatedly as an assumption in proofs of other results. For example, the Riemann hypothesis is a conjecture from number theory that — amongst other things — makes predictions about the distribution of prime numbers. Few number theorists doubt that the Riemann hypothesis is true. In fact, in anticipation of its eventual proof, some have even proceeded to develop further proofs which are contingent on the truth of this conjecture. These are called conditional proofs: the conjectures assumed appear in the hypotheses of the theorem, for the time being.
These "proofs", however, would fall apart if it turned out that the hypothesis was false, so there is considerable interest in verifying the truth or falsity of conjectures of this type.
==Important examples==
===Fermat's Last Theorem===
In number theory, Fermat's Last Theorem (sometimes called Fermat's conjecture, especially in older texts) states that no three positive integers a, b, and c can satisfy the equation a^n + b^n = c^n for any integer value of n greater than two.
This theorem was first conjectured by Pierre de Fermat in 1637 in the margin of a copy of Arithmetica, where he claimed that he had a proof that was too large to fit in the margin. The first successful proof was released in 1994 by Andrew Wiles, and formally published in 1995, after 358 years of effort by mathematicians. The unsolved problem stimulated the development of algebraic number theory in the 19th century, and the proof of the modularity theorem in the 20th century. It is among the most notable theorems in the history of mathematics, and prior to its proof it was in the Guinness Book of World Records for "most difficult mathematical problems".
===Four color theorem===
In mathematics, the four color theorem, or the four color map theorem, states that given any separation of a plane into contiguous regions, producing a figure called a map, no more than four colors are required to color the regions of the map—so that no two adjacent regions have the same color. Two regions are called adjacent if they share a common boundary that is not a corner, where corners are the points shared by three or more regions. For example, in the map of the United States of America, Utah and Arizona are adjacent, but Utah and New Mexico, which only share a point that also belongs to Arizona and Colorado, are not.
Möbius mentioned the problem in his lectures as early as 1840. The conjecture was first proposed on October 23, 1852 when Francis Guthrie, while trying to color the map of counties of England, noticed that only four different colors were needed. The five color theorem, which has a short elementary proof, states that five colors suffice to color a map and was proven in the late 19th century; however, proving that four colors suffice turned out to be significantly harder. A number of false proofs and false counterexamples have appeared since the first statement of the four color theorem in 1852.
The four color theorem was ultimately proven in 1976 by Kenneth Appel and Wolfgang Haken. It was the first major theorem to be proved using a computer. Appel and Haken's approach started by showing that there is a particular set of 1,936 maps, each of which cannot be part of a smallest-sized counterexample to the four color theorem (i.e., if they did appear, one could make a smaller counter-example). Appel and Haken used a special-purpose computer program to confirm that each of these maps had this property. Additionally, any map that could potentially be a counterexample must have a portion that looks like one of these 1,936 maps. Showing this with hundreds of pages of hand analysis, Appel and Haken concluded that no smallest counterexample exists because any must contain, yet do not contain, one of these 1,936 maps. This contradiction means there are no counterexamples at all and that the theorem is therefore true. Initially, their proof was not accepted by mathematicians at all because the computer-assisted proof was infeasible for a human to check by hand. However, the proof has since then gained wider acceptance, although doubts still remain.
===Hauptvermutung===
The Hauptvermutung (German for main conjecture) of geometric topology is the conjecture that any two triangulations of a triangulable space have a common refinement, a single triangulation that is a subdivision of both of them. It was originally formulated in 1908, by Steinitz and Tietze.
This conjecture is now known to be false. The non-manifold version was disproved by John Milnor in 1961 using Reidemeister torsion.
The manifold version is true in dimensions . The cases were proved by Tibor Radó and Edwin E. Moise in the 1920s and 1950s, respectively.
===Weil conjectures===
In mathematics, the Weil conjectures were some highly influential proposals by on the generating functions (known as local zeta-functions) derived from counting the number of points on algebraic varieties over finite fields.
A variety V over a finite field with q elements has a finite number of rational points, as well as points over every finite field with qk elements containing that field. The generating function has coefficients derived from the numbers Nk of points over the (essentially unique) field with qk elements.
Weil conjectured that such zeta-functions should be rational functions, should satisfy a form of functional equation, and should have their zeroes in restricted places. The last two parts were quite consciously modeled on the Riemann zeta function and Riemann hypothesis. The rationality was proved by , the functional equation by , and the analogue of the Riemann hypothesis was proved by .
===Poincaré conjecture===
In mathematics, the Poincaré conjecture is a theorem about the characterization of the 3-sphere, which is the hypersphere that bounds the unit ball in four-dimensional space. The conjecture states that: An equivalent form of the conjecture involves a coarser form of equivalence than homeomorphism called homotopy equivalence: if a 3-manifold is homotopy equivalent to the 3-sphere, then it is necessarily homeomorphic to it.
Originally conjectured by Henri Poincaré in 1904, the theorem concerns a space that locally looks like ordinary three-dimensional space but is connected, finite in size, and lacks any boundary (a closed 3-manifold). The Poincaré conjecture claims that if such a space has the additional property that each loop in the space can be continuously tightened to a point, then it is necessarily a three-dimensional sphere. An analogous result has been known in higher dimensions for some time.
After nearly a century of effort by mathematicians, Grigori Perelman presented a proof of the conjecture in three papers made available in 2002 and 2003 on arXiv. The proof followed on from the program of Richard S. Hamilton to use the Ricci flow to attempt to solve the problem. Hamilton later introduced a modification of the standard Ricci flow, called Ricci flow with surgery to systematically excise singular regions as they develop, in a controlled way, but was unable to prove this method "converged" in three dimensions. Perelman completed this portion of the proof. Several teams of mathematicians have verified that Perelman's proof is correct.
The Poincaré conjecture, before being proven, was one of the most important open questions in topology.
===Riemann hypothesis===
In mathematics, the Riemann hypothesis, proposed by , is a conjecture that the non-trivial zeros of the Riemann zeta function all have real part 1/2. The name is also used for some closely related analogues, such as the Riemann hypothesis for curves over finite fields.
The Riemann hypothesis implies results about the distribution of prime numbers. Along with suitable generalizations, some mathematicians consider it the most important unresolved problem in pure mathematics. The Riemann hypothesis, along with the Goldbach conjecture, is part of Hilbert's eighth problem in David Hilbert's list of 23 unsolved problems; it is also one of the Clay Mathematics Institute Millennium Prize Problems.
===P versus NP problem===
The P versus NP problem is a major unsolved problem in computer science. Informally, it asks whether every problem whose solution can be quickly verified by a computer can also be quickly solved by a computer; it is widely conjectured that the answer is no. It was essentially first mentioned in a 1956 letter written by Kurt Gödel to John von Neumann. Gödel asked whether a certain NP-complete problem could be solved in quadratic or linear time. The precise statement of the P=NP problem was introduced in 1971 by Stephen Cook in his seminal paper "The complexity of theorem proving procedures" and is considered by many to be the most important open problem in the field. It is one of the seven Millennium Prize Problems selected by the Clay Mathematics Institute to carry a US$1,000,000 prize for the first correct solution.
===Other conjectures===
Goldbach's conjecture
The twin prime conjecture
The Collatz conjecture
The Manin conjecture
The Maldacena conjecture
The Euler conjecture, proposed by Euler in the 18th century but for which counterexamples for a number of exponents (starting with n=4) were found beginning in the mid 20th century
The Hardy-Littlewood conjectures are a pair of conjectures concerning the distribution of prime numbers, the first of which expands upon the aforementioned twin prime conjecture. Neither one has either been proven or disproven, but it has been proven that both cannot simultaneously be true (i.e., at least one must be false). It has not been proven which one is false, but it is widely believed that the first conjecture is true and the second one is false.
The Langlands program is a far-reaching web of these ideas of 'unifying conjectures' that link different subfields of mathematics (e.g. between number theory and representation theory of Lie groups). Some of these conjectures have since been proved.
==In other sciences==
Karl Popper pioneered the use of the term "conjecture" in scientific philosophy. Conjecture is related to hypothesis, which in science refers to a testable conjecture.
|
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"Heinrich Tietze",
"hypothesis",
"rational function",
"counterexample",
"Kenneth Appel",
"generating function",
"positive number",
"Hilbert's eighth problem",
"Lance Fortnow",
"Goldbach's conjecture",
"Second Hardy–Littlewood conjecture",
"Henri Poincaré",
"3-sphere",
"Collatz conjecture",
"Bold hypothesis",
"algebraic variety",
"mathematics",
"axiom of choice",
"manifold",
"Euler's sum of powers conjecture",
"root of a function",
"Euclid",
"continuum hypothesis",
"Ernst Steinitz",
"Geometrization conjecture",
"Analytic torsion",
"Arithmetica",
"prime numbers",
"Proof by exhaustion",
"cardinal number",
"August Ferdinand Möbius",
"Clay Mathematics Institute",
"Hilbert's problems",
"Four Corners Monument",
"closed manifold",
"representation theory",
"Philosophy of science",
"Hypotheticals",
"axiom",
"conditional proof",
"twin prime conjecture",
"pure mathematics",
"Langlands program",
"Karl Popper",
"John Milnor",
"Consequent",
"P versus NP problem",
"sequence",
"Richard S. Hamilton",
"Fermat's conjecture",
"Euclidean geometry",
"topology",
"rational point",
"real part",
"four color theorem",
"Millennium Prize Problems",
"Tibor Radó",
"Mathematical proof",
"Société Mathématique de France",
"David Hilbert",
"Grigori Perelman",
"triangulable space",
"Ricci flow",
"five color theorem",
"functional equation",
"local zeta-function",
"Poincaré conjecture",
"Publications Mathématiques de l'IHÉS",
"theorem",
"Andrew Wiles",
"Riemann hypothesis",
"Goldbach conjecture",
"science",
"Guinness Book of World Records",
"dimension",
"Francis Guthrie",
"Fermat's Last Theorem",
"integer",
"unit ball",
"theorem-proving",
"Closed manifold",
"mathematical proof",
"Riemann zeta function",
"Ramanujan machine",
"Zermelo–Fraenkel axioms",
"American Journal of Mathematics",
"Triangulation (topology)",
"Futures studies",
"Wolfgang Haken",
"Annals of Mathematics",
"Stephen Cook",
"Wiles' proof of Fermat's Last Theorem",
"homeomorphic",
"Edwin E. Moise",
"finite field",
"Manin conjecture",
"proposition",
"Riemann hypothesis for curves over finite fields",
"number theory",
"Pólya conjecture",
"infinite set",
"W. W. Rouse Ball",
"Pierre de Fermat",
"computer-assisted proof",
"parallel postulate",
"prime number",
"3-manifold",
"Weil conjectures",
"Lie group",
"List of unsolved problems in computer science",
"Maldacena conjecture",
"homotopy equivalence",
"path (topology)",
"simply connected",
"generalized Poincaré conjecture",
"Characterization (mathematics)",
"List of conjectures",
"arXiv",
"Independence (mathematical logic)",
"Hauptvermutung",
"geometric topology",
"John von Neumann",
"algebraic number theory",
"modularity theorem",
"history of mathematics",
"universally quantified",
"Kurt Gödel",
"unifying conjecture",
"wikt:contiguity"
] |
6,139 |
Christoph Ludwig Agricola
|
Christoph Ludwig Agricola (5 November 1665 – 8 August 1724) was a German landscape painter and etcher. He was born and died in Regensburg (Ratisbon).
==Life and career==
Christoph Ludwig Agricola was born on 5 November 1665 in Regensburg in Germany. He trained, as many painters of the period did, by studying nature.
He spent a great part of his life in travel visiting England, the Netherlands and France, and residing for a considerable period in Naples, where he may have been influenced by Nicolas Poussin. He also stayed in Venice for several years around 1712, where he painted many works for Zaccaria Sagredo.
He died in Regensburg in 1724.
==Work==
Although he primarily worked in gouache and oils, documentary sources show that he also produced a small number of etchings. He was a good draughtsman, used warm lighting and exhibited a warm, masterly brushstroke.
His numerous landscapes, chiefly cabinet pictures, are remarkable for their fidelity to nature, and especially for their skilful representation of varied phases of climate, especially nocturnal scenes and weather phenomena like thunderstorms. In composition, his style shows the influence of Nicolas Poussin: Agricola's work often displays idealistic scenes like Poussin's work. In light and colour Agricola's work resembles that of Claude Lorrain. His compositions often include ruins of ancient buildings in the foreground, but his favourite foreground figures were men dressed in Oriental attire.
His pictures can be found in Dresden, Braunschweig, Vienna, Florence, Naples and many other locations in Germany and Italy.
==Legacy==
He probably tutored the artist Johann Theile and had a strong influence on him. Art historians have also noted that the work of the landscape painter Christian Johann Bendeler (1699–1728) was influenced by Agricola.
==Gallery==
File:Christoph Ludwig Agricola (zugeschr.) - Eine Flusslandschaft mit Anglern.jpg|River landscape
File:Christoph Ludwig Agricola - Großer Hänfling und Schopfmeise.jpg|Greater Redpole and crested titmous; Bluethroat
File:Christoph Ludwig Agricola (Umkreis) - Räuber schießen auf Reisende.jpg|Bandits Shooting at Travellers
File:Christoph Ludwig Agricola - Trappe un Elster in exotischer Landschaft.jpg|A bustard and a magpie in an exotic landscape
File:Christoph Ludwig Agricola - Ein Vogel auf einem Ast.jpg|A bird seated on a branch
File:Wintergezicht met ijsvermaak, RP-T-1898-A-3549.jpg|Winter face with ice entertainment
File:Christoph Ludwig Agricola - Singvogel auf einem Nadelbaum.jpg|Songbird in an Evergreen
|
[
"Italy",
"Naples",
"Landscape art",
"Bernhard Vogel (engraver)",
"Nicolas Poussin",
"Venice",
"Braunschweig",
"Regensburg",
"Sagredo family",
"Claude Lorrain",
"Dresden",
"Florence",
"Johann Theile",
"Vienna"
] |
6,140 |
Claudius
|
Tiberius Claudius Caesar Augustus Germanicus ( ; ; 1 August 10 BC – 13 October AD 54), or Claudius, was a Roman emperor, ruling from AD 41 to 54. A member of the Julio-Claudian dynasty, Claudius was born to Drusus and Antonia Minor at Lugdunum in Roman Gaul, where his father was stationed as a military legate. He was the first Roman emperor to be born outside Italy.
As he had a limp and slight deafness due to an illness he suffered when young, he was ostracized by his family and was excluded from public office until his consulship (which was shared with his nephew, Caligula, in 37). Claudius's infirmity probably saved him from the fate of many other nobles during the purges throughout the reigns of Tiberius and Caligula, as potential enemies did not see him as a serious threat. His survival led to him being declared emperor by the Praetorian Guard after Caligula's assassination, at which point he was the last adult male of his family.
Despite his lack of experience, Claudius was an able and efficient administrator. He expanded the imperial bureaucracy to include freedmen, and helped restore the empire's finances after the excesses of Caligula's reign. He was also an ambitious builder, constructing new roads, aqueducts, and canals across the Empire. During his reign, the Empire started its successful conquest of Britain. Having a personal interest in law, he presided at public trials, and issued edicts daily. He was seen as vulnerable throughout his reign, particularly by elements of the nobility. Claudius was constantly forced to shore up his position, which resulted in the deaths of many senators. Those events damaged his reputation among the ancient writers, though more recent historians have revised that opinion. Many authors contend that he was murdered by his own wife, Agrippina the Younger. After his death at the age of 63, his grandnephew and legally adopted step-son, Nero, succeeded him as emperor.
== Name ==
As a consequence of Roman customs, society, and personal preference, Claudius' full name varied throughout his life:
Tiberius Claudius D. f. Ti. n. Drusus, the cognomen Drusus being inherited from his father as his brother Germanicus, as the eldest son, inherited the cognomen Nero when their uncle the future Emperor Tiberius was adopted by Augustus into the Julii Caesares and the victory name (agnomen) Germanicus from their father.
Tiberius Claudius D. f. Ti. n. Nero, the cognomen Nero devolved to Claudius as the head of the Claudii Nerones after his elder brother was adopted by Tiberius as required by Augustus into the Julii Caesares in AD 9. Germanicus kept the victory title Germanicus as a praenomen, becoming Germanicus Julius Caesar. His son, Caligula, was known as Gaius Julius Caesar Germanicus, keeping the victory title, and later was known as Gaius Caesar Augustus Germanicus. Some authorities consider that his full name may have been Tiberius Claudius Drusus Nero Germanicus.
Tiberius Claudius Caesar Augustus Germanicus While Claudius had never been formally adopted either by Augustus or his successors, he was nevertheless the grandson of Augustus's sister Octavia, and so he felt that he had the right of family. He also adopted the name "Augustus" as the two previous emperors had done at their accessions. He kept the honorific "Germanicus" to display the connection with his heroic brother and father. He deified his paternal grandmother Livia to highlight her position as wife of the divine Augustus. Claudius frequently used the term "filius Drusi" (son of Drusus) in his titles, to remind the people of his legendary father and lay claim to his reputation.
== Family and youth ==
=== Early life ===
Claudius was born on 1 August 10 BC at Lugdunum (modern Lyon, France). He had two older siblings, Germanicus and Livilla. His mother, Antonia Minor, may have had two other children who died young. Claudius's maternal grandparents were Mark Antony and Octavia Minor, Augustus's sister, and he was therefore the great-great-grandnephew of Gaius Julius Caesar. His paternal grandparents were Livia, Augustus's third wife, and Tiberius Claudius Nero. During his reign, Claudius revived the rumour that his father Nero Claudius Drusus was actually the illegitimate son of Augustus, to give the appearance that Augustus was Claudius's paternal grandfather.
In 9 BC, Claudius's father Drusus died on campaign in Germania from a fall from a horse. Claudius was then raised by his mother, who never remarried. When his disability became evident, the relationship with his family turned sour. Antonia referred to him as a monster, and used him as a standard for stupidity. She seems to have passed her son off to his grandmother Livia for a number of years.
Livia was a little kinder, but nevertheless sent Claudius short, angry letters of reproof. He was put under the care of a former mule-driver to keep him disciplined, under the logic that his condition was due to laziness and a lack of willpower. However, by the time he reached his teenage years, his symptoms apparently waned and his family began to take some notice of his scholarly interests. In AD 7, Livy was hired to tutor Claudius in history, with the assistance of Sulpicius Flavus. He spent a lot of his time with the latter, as well as the philosopher Athenodorus. Augustus, according to a letter, was surprised at the clarity of Claudius's oratory.
=== Public life ===
Claudius' work as a historian damaged his prospects for advancement in public life. According to Vincent Scramuzza and others, he began work on a history of the Civil Wars that was either too truthful or too critical of Octavian, then reigning as Caesar Augustus. In either case, it was far too early for such an account, and may have only served to remind Augustus that Claudius was Antony's descendant. His mother and grandmother quickly put a stop to it, and this may have convinced them that Claudius was not fit for public office, since he could not be trusted to toe the existing party line.
When Claudius returned to the narrative later in life, he skipped over the wars of the Second Triumvirate altogether; but the damage was done, and his family pushed him into the background. When the Arch of Pavia was erected to honour the Imperial clan in AD 8, Claudius's name (now Tiberius Claudius Nero Germanicus after his elevation to pater familias of the Claudii Nerones on the adoption of his brother) was inscribed on the edge, past the deceased princes, Gaius and Lucius, and Germanicus's children. There is some speculation that the inscription was added by Claudius himself decades later, and that he originally did not appear at all.
When Augustus died in AD 14, Claudius – then aged 23 – appealed to his uncle Tiberius to allow him to begin the cursus honorum. Tiberius, the new Emperor, responded by granting Claudius consular ornaments. Claudius requested office once more and was snubbed. Since the new emperor was no more generous than the old, Claudius gave up hope of public office and retired to a scholarly, private life.
Despite the disdain of the Imperial family, it seems that from very early on the general public respected Claudius. At Augustus's death, the equites, or knights, chose Claudius to head their delegation. When his house burned down, the Senate demanded it be rebuilt at public expense. They also requested that Claudius be allowed to debate in the Senate. Tiberius turned down both motions, but the sentiment remained.
During the period immediately after the death of Tiberius's son, Drusus, Claudius was pushed by some quarters as a potential heir to the throne. This again suggests the political nature of his exclusion from public life. However, as this was also the period during which the power and terror of the commander of the Praetorian Guard, Sejanus, was at its peak, Claudius chose to downplay this possibility. After the death of Tiberius, the new emperor Caligula (the son of Claudius's brother Germanicus) recognized Claudius to be of some use. He appointed Claudius his co-consul in 37 to emphasize the memory of Caligula's deceased father Germanicus.
Despite this, Caligula tormented his uncle: playing practical jokes, charging him enormous sums of money, humiliating him before the Senate, and the like. According to Cassius Dio, Claudius became sickly and thin by the end of Caligula's reign, most likely due to stress. A possible surviving portrait of Claudius from this period may support this.
===Assassination of Caligula and Declaration of Claudius as Emperor (AD 41)===
On 24 January 41, Caligula was assassinated in a conspiracy involving Cassius Chaerea – a military tribune in the Praetorian Guard – and several senators. There is no evidence that Claudius had a direct hand in the assassination, although it has been argued that he knew about the plot – particularly since he left the scene of the crime shortly before his nephew was murdered. However, after the deaths of Caligula's wife and daughter, it became apparent that Cassius intended to go beyond the terms of the conspiracy and wipe out the Imperial family.
In the chaos following the murder, Claudius witnessed the German guard cut down several uninvolved noblemen, including many of his friends. He fled to the palace to hide. According to tradition, a Praetorian named Gratus found him hiding behind a curtain and suddenly proclaimed him princeps. so it remains uncertain. Eventually the Senate was forced to give in. In return, Claudius granted a general amnesty, although he executed a few junior officers involved in the conspiracy. The actual assassins, including Cassius Chaerea and Julius Lupus, the murderer of Caligula's wife and daughter, were put to death to ensure Claudius's own safety and as a future deterrent.
Since Claudius was the first emperor proclaimed on the initiative of the Praetorian Guard instead of the Senate, his repute suffered at the hands of commentators (such as Seneca). Moreover, they accused him of being the first emperor to resort to bribery as a means to secure army loyalty and rewarded the soldiers of the Praetorian Guard that had elevated him with 15,000 sesterces, although Tiberius and Augustus had both left gifts to the army and guard in their wills and upon Caligula's death the same would have been expected, even if no will existed. Claudius remained grateful to the guard, issuing coins with tributes to the Praetorians in the early part of his reign.
==Emperor==
Claudius took several steps to legitimize his rule against potential usurpers, most of them emphasizing his place within the Julio-Claudian family. He adopted the name "Caesar" as a cognomen, as the name still carried great weight with the populace. To do so, he dropped the cognomen "Nero", which he had adopted as pater familias of the Claudii Nerones when his brother Germanicus was adopted. As Pharaoh of Egypt, Claudius adopted the royal titulary Tiberios Klaudios, Autokrator Heqaheqau Meryasetptah, Kanakht Djediakhshuemakhet ("Tiberius Claudius, Emperor and ruler of rulers, beloved of Isis and Ptah, the strong bull of the stable moon on the horizon").
While Claudius had never been formally adopted either by Augustus or his successors, he was nevertheless the grandson of Augustus's sister Octavia, and so he felt that he had the right of family. He also adopted the name "Augustus" as the two previous emperors had done at their accessions. He kept the honorific "Germanicus" to display the connection with his heroic brother. He deified his paternal grandmother Livia to highlight her position as wife of the divine Augustus. Claudius frequently used the term "filius Drusi" (son of Drusus) in his titles, to remind the people of his legendary father and lay claim to his reputation.
Pliny the Elder noted, according to the 1938 Loeb Classical Library translation by Harris Rackham, "... many people do not allow any gems in a signet-ring, and seal with the gold itself; this was a fashion invented when Claudius Cæsar was emperor."
===Senate===
Because of the circumstances of his accession, Claudius took great pains to please the Senate. During regular sessions, the Emperor sat among the Senate body, speaking in turn. When introducing a law, he sat on a bench between the consuls in his position as holder of the power of Tribune, (the Emperor could not officially serve as a Tribune of the Plebes since he was a patrician, but this was a power taken by previous rulers, which he continued). He refused to accept all his predecessors' titles (including Imperator) at the beginning of his reign, preferring to earn them in due course. He allowed the Senate to issue its own bronze coinage for the first time since Augustus. He also restored the peaceful Imperial provinces of Macedonia and Achaea as senatorial provinces.
Claudius set about remodeling the Senate into a more efficient, representative body. He chided the senators about their reluctance to debate bills introduced by himself, as noted in the fragments of a surviving speech:
In 47, he assumed the office of censor with Lucius Vitellius, which had been allowed to lapse for some time. He struck out the names of many senators and equites who no longer met qualifications, but showed respect by allowing them to resign in advance. At the same time, he sought to admit to the senate eligible men from the provinces. The Lyon Tablet preserves his speech on the admittance of Gallic senators, in which he addresses the Senate with reverence but also with criticism for their disdain of these men. He even joked about how the Senate had admitted members from beyond Gallia Narbonensis (Lyons), i.e. himself. He also increased the number of patricians by adding new families to the dwindling number of noble lines. Here he followed the precedent of Lucius Junius Brutus and Julius Caesar.
Nevertheless, many in the Senate remained hostile to Claudius, and many plots were made on his life. This hostility carried over into the historical accounts. As a result, Claudius reduced the Senate's power for the sake of efficiency. The administration of Ostia was turned over to an Imperial procurator after construction of the port. Administration of many of the empire's financial concerns was turned over to Imperial appointees and freedmen. This led to further resentment and suggestions that these same freedmen were ruling the Emperor.
===Secretariat and centralization of powers===
Claudius was hardly the first emperor to use freedmen to help with the day-to-day running of the Empire. He has however become famous for the new extents at which he made use of such men in the administration of the government, forced by the centralization of the powers of the princeps and not wanting free-born magistrates to serve under him as if they were not peers.
The secretariat was divided into bureaus, with each being placed under the leadership of one freedman. Narcissus was the secretary of correspondence. Pallas became the secretary of the treasury. Callistus became secretary of justice. There was a fourth bureau for miscellaneous issues, which was put under Polybius until his execution for treason. The freedmen could also officially speak for the Emperor, as when Narcissus addressed the troops in Claudius's stead before the conquest of Britain.
Since these were important positions, the senators were aghast at their being placed in the hands of former slaves and "well-known eunuchs". If freedmen had total control of money, letters and law, it seemed it would not be hard for them to manipulate the Emperor. This is exactly the accusation put forth by ancient sources. However, these same sources admit that the freedmen were loyal to Claudius.]]
Claudius conducted a census in 48 that found 5,984,072 (adult male) Roman citizens (women, children, slaves, and free adult males without Roman citizenship were not counted), an increase of around a million since the census conducted at Augustus's death. He had helped increase this number through the foundation of Roman colonies that were granted blanket citizenship. These colonies were often made out of existing communities, especially those with elites who could rally the populace to the Roman cause. Several colonies were placed in new provinces or on the border of the Empire to secure Roman holdings as quickly as possible.
Additionally under Claudius, the Empire underwent its first major territorial expansion since the reign of Augustus. The provinces of Thrace, Noricum, Lycia, and Judea were annexed (or put under direct rule) under various circumstances during his term. The annexation of Mauretania, begun under Caligula, was completed after the defeat of rebel forces, as well as the official division of the former client kingdom into two Imperial provinces.
====The British Campaign====
The most far-reaching conquest however was that of Britannia: In 43, Claudius sent Aulus Plautius with four legions to Britain (Britannia) after an appeal from an ousted tribal ally. Britain was an attractive target for Rome because of its mines and the potential of slave labor, as well as being a haven for Gallic rebels. Claudius himself traveled to the island after the completion of initial offensives, bringing with him reinforcements and elephants. The Roman colonia of Colonia Claudia Victricensis was established as the provincial capital of the newly established province of Britannia at Camulodunum, where a large temple was dedicated in his honour.
He left Britain after 16 days, but remained in the provinces for some time. The Senate granted him a triumph for his efforts. Only members of the Imperial family were allowed such honours, but Claudius subsequently lifted this restriction for some of his conquering generals. He was granted the honorific "Britannicus" but only accepted it on behalf of his son, never using the title himself. When the British general Caractacus was captured in 50, Claudius granted him clemency. Caractacus lived out his days on land provided by the Roman state, an unusual end for an enemy commander.
===Public works===
Claudius embarked on many public works throughout his reign, both in the capital and in the provinces. He built or finished two aqueducts, the Aqua Claudia, begun by Caligula, and the Aqua Anio Novus. These entered the city in 52 and met at the Porta Maggiore. He also restored a third, the Aqua Virgo.
He paid special attention to transportation. Throughout Italy and the provinces he built roads and canals. Among these was a large canal leading from the Rhine to the sea, as well as a road from Italy to Germany – both begun by his father, Drusus. Closer to Rome, he built a navigable canal on the Tiber, leading to Portus, his new port just north of Ostia. This port was constructed in a semicircle with two moles and a lighthouse at its mouth, reducing flooding in Rome.
The port at Ostia was part of Claudius's solution to the constant grain shortages that occurred in winter, after the Roman shipping season. The other part of his solution was to insure the ships of grain merchants who were willing to risk travelling to Egypt in the off-season. He also granted their sailors special privileges, including citizenship and exemption from the Lex Papia Poppaea, a law that regulated marriage. In addition, he repealed the taxes that Caligula had instituted on food, and further reduced taxes on communities suffering drought or famine.
The last part of Claudius's plan to avoid famine was to increase the amount of arable land in Italy. This was to be achieved by draining the Fucine lake, also making the nearby river navigable year-round. A serious famine is mentioned in the book of Acts as taking place during Claudius' reign, and had been prophesied by a Christian called Agabus while visiting Antioch.
A tunnel was dug through the lake bed, but the plan was a failure. The tunnel was crooked and not large enough to carry the water, which caused it to back up when opened. The resultant flood washed out a large gladiatorial exhibition held to commemorate the opening, causing Claudius to run for his life along with the other spectators. The draining of the lake continued to present a problem well into the Middle Ages. It was finally achieved by the Prince Torlonia in the 19th century, producing over of new arable land; he expanded the Claudian tunnel to three times its original size.
===Religious reforms===
Claudius, as the author of a treatise on Augustus's religious reforms, thought himself to be in a good position to institute some of his own. He had strong opinions about the proper form for state religion. He refused the request of Alexandrian Greeks to dedicate a temple to his divinity, saying that only gods may choose new gods; he restored lost days to festivals and got rid of many extraneous celebrations added by Caligula. He also re-established old observances and archaic language.
Claudius was concerned with the spread of eastern mysteries within the city and searched for more Roman replacements. He emphasized the Eleusinian Mysteries, which had been practiced by so many during the Republic. He expelled foreign astrologers, and at the same time rehabilitated the old Roman soothsayers (known as haruspices) as a replacement. He was especially hard on Druidism, because of its incompatibility with the Roman state religion and its proselytizing activities.
===Judicial and legislative affairs===
Claudius personally judged many of the legal cases tried during his reign. Ancient historians have many complaints about this, stating that his judgments were variable and sometimes did not follow the law. He was also easily swayed. Nevertheless, Claudius paid detailed attention to the operation of the judicial system. He extended the summer court session, as well as the winter term, by shortening the traditional breaks. Claudius also made a law requiring plaintiffs to remain in the city while their cases were pending, as defendants had previously been required to do. These measures had the effect of clearing out the docket. The minimum age for jurors was also raised to 25 to ensure a more experienced jury pool.
Claudius also settled disputes in the provinces. He freed the island of Rhodes from Roman rule for their good faith and exempted Ilium (Troy) from taxes. Early in his reign, the Greeks and Jews of Alexandria each sent him embassies after riots broke out between the two communities. This resulted in the famous "Letter to the Alexandrians", which reaffirmed Jewish rights in the city but forbade them to move in more families en masse. According to Josephus, he then reaffirmed the rights and freedoms of all the Jews in the Empire. However, Claudius also expelled Jews from the city of Rome, following disturbances allegedly instigated by Christians. This expulsion is attested to in Acts of the Apostles (18:2), and by Roman historians Suetonius and Cassius Dio along with the fifth-century Christian author Paulus Orosius.
One of Claudius's investigators discovered that many old Roman citizens based in the city of Tridentum (modern Trento) were not in fact citizens. The Emperor issued a declaration, contained in the Tabula clesiana, that they would be allowed to hold citizenship from then on, since to strip them of their status would cause major problems. However, in individual cases, Claudius punished the false assumption of citizenship harshly, making it a capital offense. Similarly, any freedmen found to be laying false claim to membership of the Roman equestrian order were to have their property confiscated and selling into slavery, in the words of Suetonius, "such as were ungrateful and a cause of complaint to their patrons".
Numerous edicts were issued throughout Claudius's reign. These were on a number of topics, everything from medical advice to moral judgments. A famous medical example is one promoting yew juice as a cure for snakebite. Suetonius wrote that he is even said to have thought of an edict allowing public flatulence for good health. One of the more famous edicts concerned the status of sick slaves. Masters had been abandoning ailing slaves at the temple of Aesculapius on Tiber Island to die instead of providing them with medical assistance and care, and then reclaiming them if they lived. Claudius ruled that slaves who were thus abandoned and recovered after such treatment would be free. Furthermore, masters who chose to kill slaves rather than take care of them were liable to be charged with murder.
===Public games and entertainments===
According to Suetonius, Claudius was extraordinarily fond of games. He is said to have risen with the crowd after gladiatorial matches and given unrestrained praise to the fighters. Claudius also presided over many new and original events. Soon after coming into power he instituted games to be held in honor of his father on the latter's birthday; annual games were also held in honor of his accession, and took place at the Praetorian camp where Claudius had first been proclaimed Emperor.
Claudius organized a performance of the Secular Games, marking the 800th anniversary of the founding of Rome. Augustus had performed the same games less than a century prior. Augustus's excuse was that the interval for the games was 110 years, not 100, but his date actually did not qualify under either reasoning. Claudius also presented staged naval battles to mark the attempted draining of the Fucine Lake, as well as many other public games and shows.
At Ostia, in front of a crowd of spectators, Claudius fought an orca which was trapped in the harbour. The event was witnessed by Pliny the Elder:
Claudius also restored and adorned many public venues in Rome. At the Circus Maximus, the turning posts and starting stalls were replaced in marble and embellished, and an embankment was probably added to prevent flooding of the track. Claudius also reinforced or extended the seating rules that reserved front seating at the Circus for senators. He rebuilt Pompey's Theatre after it had been destroyed by fire, organising special fights at the re-dedication, which he observed from a special platform in the orchestra box.
=== Plots and coup attempts ===
Several coup attempts were made during Claudius's reign, resulting in the deaths of many senators. Appius Silanus was executed early in Claudius's reign under questionable circumstances. Shortly after this, a large rebellion was undertaken by the Senator Vinicianus and Scribonianus - governor of Dalmatia - and gained quite a few senatorial supporters. It ultimately failed because of the reluctance of Scribonianus' troops, which led to the suicide of the main conspirators.
Many other senators tried different conspiracies and were condemned. Claudius's son-in-law Pompeius Magnus was executed for his part in a conspiracy with his father Crassus Frugi. Another plot involved the consulars Lusius Saturninus, Cornelius Lupus, and Pompeius Pedo.
In 46, Asinius Gallus, grandson of Asinius Pollio, and Titus Statilius Taurus Corvinus were exiled for a plot hatched with several of Claudius's own freedmen. Valerius Asiaticus was executed without public trial for unknown reasons. Ancient sources say the charge was adultery, and that Claudius was tricked into issuing the punishment. However, Claudius singles out Asiaticus for special damnation in his speech on the Gauls, which dates over a year later, suggesting that the charge must have been much more serious.
Asiaticus had been a claimant to the throne in the chaos following Caligula's death and a co-consul with Titus Statilius Taurus Corvinus. Most of these conspiracies took place before Claudius's term as Censor, and may have induced him to review the Senatorial rolls. The conspiracy of Gaius Silius in the year after his Censorship, 48, is detailed in book 11 of Tacitus' Annals. This section of Tacitus' history narrates the alleged conspiracy of Claudius's third wife, Messalina. Suetonius states that a total of 35 senators and 300 knights were executed for offenses during Claudius's reign.
==Marriages and personal life==
Suetonius and the other ancient authors accused Claudius of being dominated by women and wives, and of being a womanizer.
Claudius married four times, after two failed betrothals. The first betrothal was to his distant cousin Aemilia Lepida, but was broken for political reasons. The second was to Livia Medullina Camilla, which ended with Medullina's sudden death on their wedding day.
===Plautia Urgulanilla===
Plautia Urgulanilla was the granddaughter of Livia's confidant Urgulania. During their marriage she gave birth to a son, Claudius Drusus. Drusus died of asphyxiation in his early teens, shortly after becoming engaged to Junilla, daughter of Sejanus.
Claudius later divorced Urgulanilla for adultery and on suspicion of murdering her sister-in-law Apronia. When Urgulanilla gave birth after the divorce, Claudius repudiated the baby girl, Claudia, as the father was allegedly one of his own freedmen. Later, this action made him the target of criticism by his enemies.
===Aelia Paetina===
Soon after, (possibly in 28) Claudius married Aelia Paetina, a relative of Sejanus, if not Sejanus's adoptive sister. During their marriage, Claudius and Paetina had a daughter, Claudia Antonia. He later divorced her after the marriage became a political liability. One version suggests that it may have been due to emotional and mental abuse by Paetina.
===Valeria Messalina===
Some years after divorcing Aelia Paetina, in 38 or early 39, Claudius married Valeria Messalina, who was his first cousin once removed (Claudius's grandmother, Octavia the Younger, was Valeria's great-grandmother on both her mother and father's side) and closely allied with Caligula's circle. Shortly thereafter, she gave birth to a daughter, Claudia Octavia. A son, first named Tiberius Claudius Germanicus, and later known as Britannicus, was born just after Claudius's accession.
This marriage ended in tragedy. The ancient historians allege that Messalina was a nymphomaniac who was regularly unfaithful to Claudius—Tacitus states she went so far as to compete with a prostitute to see who could have more sexual partners in a nightand manipulated his policies to amass wealth. In 48, Messalina married her lover Gaius Silius in a public ceremony while Claudius was at Ostia.
Sources disagree as to whether or not she divorced the Emperor first, and whether the intention was to usurp the throne. Under Roman law, the spouse needed to be informed that he or she had been divorced before a new marriage could take place; the sources state that Claudius was in total ignorance until after the marriage. Scramuzza, in his biography, suggests that Silius may have convinced Messalina that Claudius was doomed, and the union was her only hope of retaining her rank and protecting her children. The historian Tacitus suggests that Claudius's ongoing term as Censor may have prevented him from noticing the affair before it reached such a critical point, after which she was executed.
===Agrippina the Younger===
Claudius married once more. Ancient sources tell that his freedmen put forward three candidates, Caligula's third wife Lollia Paulina, Claudius's divorced second wife Aelia Paetina and Claudius's niece Agrippina the Younger. According to Suetonius, Agrippina won out through her feminine wiles. She gradually seized power from Claudius and successfully conspired to eliminate his son's rivals, opening the way for her son to become emperor.
The truth is probably more political. The attempted coup d'état by Silius and Messalina probably made Claudius realize the weakness of his position as a member of the Claudian (but not the Julian) family. This weakness was compounded by the fact that he did not yet have an obvious adult heir, Britannicus being just a boy. Agrippina was one of the few remaining descendants of Augustus, and her son Lucius Domitius Ahenobarbus (the future Nero) was one of the last males of the Imperial family. Coup attempts might rally around the pair and Agrippina was already showing such ambition. It has been suggested that the Senate may have pushed for the marriage, an attempt to end the feud between the Julian and Claudian branches. This feud dated back to Agrippina's mother's actions against Tiberius after the death of her husband Germanicus (Claudius's brother), actions that Tiberius had punished.
Another reason was to bring in Lucius Domitius Ahenobarbus as a candidate for the succession. His prestige as the descendent of Augustus and Germanicus made him popular, and marking him as an heir would have helped the survival of Claudius' regime. In any case, Claudius accepted Agrippina and later adopted the mature Ahenobarbus as his son, renaming him as 'Nero Claudius Caesar'.
Nero was married to Claudius's daughter Octavia, made joint heir with the underage Britannicus, and promoted; Augustus had similarly named his grandson Postumus Agrippa and his stepson Tiberius as joint heirs, and Tiberius had named Caligula as his joint heir with his grandson Tiberius Gemellus. Adoption of adults or near adults was an old tradition in Rome when a suitable natural adult heir was unavailable, as was the case during Britannicus's minority. Claudius may have previously looked to adopt one of his sons-in-law to protect his own reign.
Faustus Cornelius Sulla Felix, who was married to Claudius's daughter Claudia Antonia, was only descended from Octavia and Antony on one side – not close enough to the Imperial family to ensure his right to be Emperor (although that did not stop others from making him the object of a coup attempt against Nero a few years later), besides being the half-brother of Valeria Messalina, which told against him. Nero was more popular with the general public as both the grandson of Germanicus and the direct descendant of Augustus.
==Affliction and personality==
The historian Suetonius describes the physical manifestations of Claudius's condition. His knees were weak and gave way under him and his head shook. He stammered and his speech was confused. He slobbered and his nose ran when he was excited. The Stoic Seneca states in his Apocolocyntosis that Claudius's voice belonged to no land animal, and that his hands were weak as well.
However, he showed no physical deformity, as Suetonius notes that when calm and seated he was a tall, well-built figure of dignitas. When angered or stressed, his symptoms became worse. Historians agree that this condition improved upon his accession to the throne. Claudius himself claimed that he had exaggerated his ailments to save his life.
Modern assessments of his health have changed several times in the past century. Prior to World War II, infantile paralysis (or polio) was widely accepted as the cause. This is the diagnosis used in Robert Graves's Claudius novels, first published in the 1930s. The New York Times wrote in 1934 that Claudius suffered from infantile paralysis (which led to his limp state) and measles (which made him deaf) at seven months of age, among several other ailments. Polio does not explain many of the described symptoms, however, and a more recent theory implicates cerebral palsy as the cause. Tourette syndrome has also been considered a possibility.
As a person, ancient historians described Claudius as generous and lowbrow, a man who sometimes lunched with the plebeians. They also paint him as bloodthirsty and cruel, over-fond of gladiatorial combat and executions, and very quick to anger; Claudius himself acknowledged the latter trait, and apologized publicly for his temper. According to the ancient historians he was also excessively trusting, and easily manipulated by his wives and freedmen, but at the same time they portray him as paranoid and apathetic, dull and easily confused.
==Scholarly works and their impact==
Claudius wrote copiously throughout his life. Arnaldo Momigliano states that during the reign of Tiberius, which covers the peak of Claudius's literary career, it became impolitic to speak of republican Rome. The trend among the young historians was either to write about the new empire or about obscure antiquarian topics. Claudius was the rare scholar who covered both.
Besides his history of Augustus' reign that caused him so much grief, his major works included Tyrrhenika, a twenty-book Etruscan history, and Carchedonica, an eight-volume history of Carthage, as well as an Etruscan dictionary. He also wrote a book on dice-playing. Despite the general avoidance of the topic of the Republican era, he penned a defense of Cicero against the charges of Asinius Gallus. Modern historians have used this to determine the nature of his politics and of the aborted chapters of his civil war history.
He proposed a reform of the Latin alphabet by the addition of three new letters; he officially instituted the change during his censorship but they did not survive his reign. Claudius also tried to revive the old custom of putting dots between successive words (Classical Latin was written with no spacing). Finally, he wrote an eight-volume autobiography that Suetonius describes as lacking in taste. Claudius (like most of the members of his dynasty) harshly criticized his predecessors and relatives in surviving speeches.
None of the works survived, but other sources' reference to him provide material for the surviving histories of the Julio-Claudian dynasty. Suetonius quotes Claudius's autobiography once and must have used it as a source numerous times. Tacitus uses Claudius's arguments for the orthographical innovations mentioned above and may have used him for some of the more antiquarian passages in his annals. Claudius is the source for numerous passages of Pliny's Natural History.
The influence of historical study on Claudius is obvious. In his speech on Gallic senators, he uses a version of the founding of Rome identical to that of Livy, his tutor in adolescence. Many of the public works instituted in his reign were based on plans first suggested by Julius Caesar. Levick believes this emulation of Caesar may have spread to all aspects of his policies.
His censorship seems to have been based on those of his ancestors, particularly Appius Claudius Caecus, and he used the office to put into place many policies based on those of Republican times. This is when many of his religious reforms took effect; also, his building efforts greatly increased during his tenure. In fact, his assumption of the office of Censor may have been motivated by a desire to see his academic labors bear fruit. For example, he believed (as most Romans did) that Caecus had used the power of the censorship office to introduce the letter "R" and so used his own term to introduce his new letters.
==Death==
Ancient historians agree that Claudius was murdered by poison – possibly contained in mushrooms or on a feather (ostensibly put down his throat to induce vomiting) – and died in the early hours of 13 October 54.
Nearly all implicate his final and powerful wife, Agrippina, as the instigator. Agrippina and Claudius had become more combative in the months leading up to his death. This carried on to the point where Claudius openly lamented his bad wives, and began to comment on Britannicus' approaching manhood with an eye towards restoring his status within the imperial family. Agrippina had motive in ensuring the succession of Nero before Britannicus could gain power.
Some implicate either his taster Halotus, his doctor Xenophon, or the infamous poisoner Locusta as the administrator of the fatal substance. Some say he died after prolonged suffering following a single dose at dinner, and some have him recovering only to be poisoned again. Among his contemporary sources, Seneca the Younger ascribed the emperor's death to natural causes, while Josephus only spoke of rumors of his poisoning.
Some historians have cast doubt on whether Claudius was murdered or merely died from illness or old age. Evidence against his murder include his serious illnesses in his last years, his unhealthy lifestyle and the fact that his taster Halotus continued to serve in the same position under Nero. Claudius had been so ill the year before that Nero vowed games for his recovery and the year of 54 seems to have been such an unhealthy year that one sitting member of each magistracy died within the span of a few months. He may even have died by eating a naturally poisonous mushroom, possibly Amanita muscaria. On the other hand, some modern scholars claim the near universality of the accusations in ancient texts lends credence to the crime. Claudius's ashes were interred in the Mausoleum of Augustus on 24 October 54, after a funeral similar to that of his great-uncle Augustus 40 years earlier.
==Legacy==
===Divine honours===
Already, while alive, he received the widespread private worship of a living princeps and was worshipped in Britannia in his own temple in Camulodunum.
Claudius was deified by Nero and the Senate almost immediately.
===Views of the new regime===
Agrippina had sent Narcissus away shortly before Claudius's death, and now had the freedman murdered.
The last act of this secretary of letters was to burn all of Claudius's correspondence – most likely so it could not be used against him and others in an already hostile new regime. Thus Claudius's private words about his own policies and motives were lost to history. Just as Claudius had criticized his predecessors in official edicts, Nero often criticized the deceased Emperor, and many Claudian laws and edicts were disregarded under the reasoning that he was too stupid and senile to have meant them.
Seneca's Apocolocyntosis mocks the deification of Claudius and reinforces the view of Claudius as an unpleasant fool; this remained the official view for the duration of Nero's reign. Eventually Nero stopped referring to his deified adoptive father at all. Claudius's temple was left unfinished after only some of the foundation had been laid down. Eventually the site was overtaken by Nero's Golden House.
===Flavian and later perspectives===
The Flavians, who had risen to prominence under Claudius, took a different tack. They needed to shore up their legitimacy, but also justify the fall of the Julio-Claudians. They reached back to Claudius in contrast with Nero, to show that they were associated with a good regime. Commemorative coins were issued of Claudius and his son Britannicus, who had been a friend of Emperor Titus (Titus was born in 39, Britannicus was born in 41). When Nero's Golden House was burned, the Temple of Claudius was finally completed on the Caelian Hill.
However, as the Flavians became established, they needed to emphasize their own credentials more, and their references to Claudius ceased. Instead, he was lumped with the other emperors of the fallen dynasty. His state-cult in Rome probably continued until the abolition of all cults of dead Emperors by Maximinus Thrax in 237–238. The Feriale Duranum, probably identical to the festival calendars of every regular army unit, assigns him a sacrifice of a steer on his birthday, the Kalends of August. And such commemoration (and consequent feasting) probably continued until the Christianization and disintegration of the army in the late 4th century.
Graves's two books were the basis for a British television adaptation I, Claudius, produced by the BBC. The series starred Derek Jacobi as Claudius and was broadcast in 1976 on BBC2. It was a substantial critical success, and won several BAFTA awards. The series was later broadcast in the United States on Masterpiece Theatre in 1977. The 1996 7-VHS release and the later DVD release of the television series, include The Epic That Never Was documentary.
A radio adaptation of the Graves novels by Robin Brooks and directed by Jonquil Panting, was broadcast in six one-hour episodes on BBC Radio 4 beginning 4 December 2010. The cast featured Tom Goodman-Hill as Claudius, Derek Jacobi as Augustus, Harriet Walter as Livia, Tim McInnerny as Tiberius and Samuel Barnett as Caligula.
In 2011, it was announced rights for a miniseries adaptation passed to HBO and BBC Two. Anne Thomopoulos and Jane Tranter, producers of the popular HBO–BBC2 Rome miniseries, were attached to the I, Claudius project. However, as of 2018, it has yet to be produced, and no release date is pending.
The 1954 film Demetrius and the Gladiators also portrayed him sympathetically, played by Barry Jones.
In the 1960 film Messalina, Claudius is portrayed by Mino Doro.
On television, Freddie Jones portrayed Claudius in the 1968 British television series The Caesars.
The 1975 TV Special Further Up Pompeii! (based on the Frankie Howerd sit-com Up Pompeii!) featured Cyril Appleton as Claudius.
In the 1979 motion picture Caligula, where the role was performed by Giancarlo Badessi, Claudius is depicted as an idiot, in contrast to Robert Graves' portrait of Claudius as a cunning and deeply intelligent man, who is perceived by others to be an idiot.
In the 1981 Franco-Italian film Caligula and Messalina, he was portrayed by Gino Turini (as John Turner).
The 1985 made-for-television miniseries A.D. features actor Richard Kiley as Claudius. Kiley portrays him as thoughtful, but willing to cater to public opinion as well as being under the influence of Agrippina.
In the 2004 TV film Imperium: Nero, Claudius is portrayed by Massimo Dapporto.
He is portrayed in Season 3 of the Netflix documentary series Roman Empire, which focused on the reign of Caligula, by Kelson Henderson. The series concludes with Claudius's accession.
There is also a reference to Claudius's suppression of a coup in the movie Gladiator, though that incident is entirely fictional.
In the series Britannia (2018), Claudius visits Britannia, played by Steve Pemberton as a fool who is drugged by Aulus Plautius.
He is portrayed by Derek Jacobi in the 2019 BBC film Horrible Histories: The Movie - Rotten Romans
In literature, Claudius and his contemporaries appear in the historical novel The Roman by Mika Waltari. Canadian-born science fiction writer A. E. van Vogt reimagined Robert Graves's Claudius story, in his two novels, Empire of the Atom and The Wizard of Linn.
The historical novel Chariot of the Soul by Linda Proud features Claudius as host and mentor of the young Togidubnus, son of King Verica of the Atrebates, during his ten-year stay in Rome. When Togidubnus returns to Britain in advance of the Roman army, it is with a mission given to him by Claudius.
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"Stoicism",
"Agabus",
"Aqueduct (Roman)",
"Locusta",
"Gaius Caesar Augustus Germanicus",
"I, Claudius (TV series)",
"Mauretania",
"Aelia Paetina",
"The Roman",
"Pavia",
"Lyon, France",
"Massimo Dapporto",
"Loeb Classical Library",
"Fucine lake",
"Claudius Drusus",
"Demetrius and the Gladiators",
"Mino Doro",
"Julio-Claudian family tree",
"Circus Maximus",
"s:Of Consolation: To Polybius",
"Nero",
"ProQuest",
"senatus consultum",
"Roman Senate",
"Insurance",
"Roman Italy",
"Roman conquest of Britain",
"Claudius (novel)",
"Rainer Riesner",
"orca",
"BBC Radio 4",
"Frankie Howerd",
"Cornelius Lupus",
"Gaul",
"Titus Statilius Taurus Corvinus",
"Jews of Alexandria",
"Interpunct",
"Messalina (1960 film)",
"Autokrator",
"Troy",
"Mausoleum of Augustus",
"Caligula (film)",
"pater familias",
"Roman History (Cassius Dio)",
"Gaius Plinius Secundus",
"Roman triumph",
"Aqua Anio Novus",
"Roman citizenship",
"Postumus Agrippa",
"princeps",
"Lucius Salvius Otho Titianus",
"adultery",
"Boudican revolt",
"Paulus Orosius",
"Etruscan civilization",
"Livy",
"Hypersexuality",
"Gaius Terentius Tullius Geminus",
"Pax-Nemesis",
"Claudius the God",
"Antonia Minor",
"Titus",
"Noricum",
"Lucius Arruntius Camillus Scribonianus",
"British Museum",
"Britannia",
"Castra Praetoria",
"military tribune",
"British Academy of Film and Television Arts",
"Tribune",
"Vitellius",
"Lucius Annius Vinicianus",
"Livia",
"Roman emperor",
"Lucius Caesar",
"Cicero",
"Grammatical person",
"haruspices",
"List of Roman emperors",
"Polybius (freedman)",
"Gaius Asinius Gallus Saloninus",
"Triumphal arch",
"Rome",
"Freedman",
"Tiberius Claudius Narcissus",
"Gladiator (2000 film)",
"Gaius Caesar",
"Varro",
"France",
"Pliny the Elder",
"Proselytism",
"Harvard University Press",
"founding of Rome",
"Drusus Julius Caesar",
"De arte aleae",
"Halotus",
"cognomen",
"Claudia Antonia",
"Promagistrate",
"Acts 18:2",
"Pallas (freedman)",
"Nero Claudius Drusus",
"Columbia University Press",
"Mark Antony",
"Aulus Plautius",
"Agrippina the Younger",
"Aulus Caecina Paetus",
"Up Pompeii!",
"Natural History (Pliny)",
"Gaius Stertinius Xenophon",
"Valeria Messalina",
"Augustus",
"Psychological stress",
"Flavians",
"BBC Two",
"Faustus Cornelius Sulla Felix",
"Lawrence Alma-Tadema",
"Lollia Paulina",
"Tyrrhenika",
"Taxus baccata",
"Harriet Walter",
"Gaius Sallustius Passienus Crispus",
"Roman Republic",
"Herod Agrippa",
"Servius Cornelius Scipio Salvidienus Orfitus (consul 51)",
"The Annals",
"denarius",
"Roman Britain",
"Livilla",
"Lyons",
"Lucius Annaeus Seneca the Younger",
"List of early imperial Roman consuls",
"Roman law",
"senatorial provinces",
"infantile paralysis",
"Druidism",
"Robert Graves",
"Jonquil Panting",
"Apocolocyntosis divi Claudii",
"British Broadcasting Corporation",
"Gaius Petronius Pontius Nigrinus",
"Africanus Fabius Maximus",
"Party line (politics)",
"Claudii Nerones",
"Quintus Futius Lusius Saturninus",
"Tunnels of Claudius",
"The Twelve Caesars",
"Empire of the Atom",
"Carthage",
"Lucius Cassius Dio",
"Womanizing",
"Gnaeus Acerronius Proculus",
"Lugdunum",
"Titus Statilius Taurus (consul 44)",
"Tiberius Claudius Nero (father of Tiberius Caesar)",
"Tacitus",
"Octavia Minor",
"repudiate",
"Camulodunum",
"Rome (TV series)",
"Cassius Chaerea",
"Domus Aurea",
"Giancarlo Badessi",
"Numerus Batavorum",
"Julia Agrippina",
"Gnaeus Pompeius Magnus (husband of Claudia Antonia)",
"Rhodes",
"Gratus",
"Sejanus",
"Pertinax",
"eunuch",
"Netflix",
"Gaius Silius (consul designatus 49 AD)",
"Julia Drusilla (daughter of Caligula)",
"Charles Laughton",
"Josef von Sternberg",
"Bellum Judaicum",
"Iullus Antonius",
"Valerius Asiaticus",
"Urgulania",
"Seneca the Younger",
"Torlonia",
"cerebral palsy",
"Tom Goodman-Hill",
"Temple of Claudius, Colchester",
"Acts of the Apostles",
"s:The War of the Jews/Book II",
"Gaius Julius Callistus",
"Gallia Narbonensis",
"Scott Rudin",
"Naples National Archaeological Museum",
"coup d'état",
"Claudia gens",
"will (law)",
"Lucius Vitellius",
"Milonia Caesonia",
"Antiquities of the Jews",
"R",
"Merle Oberon",
"William Whiston",
"Julio-Claudian",
"Germanicus",
"Derek Jacobi",
"Antonia the Younger",
"Antioch",
"book of Acts",
"Aqua Claudia",
"Porta Maggiore",
"Robin Brooks",
"Horrible Histories: The Movie – Rotten Romans",
"A. E. van Vogt",
"Pompey's Theatre",
"Barry Jones (actor)",
"Amanita muscaria",
"Tiber Island",
"Achaea (Roman province)",
"Trento",
"World War II",
"Plautia Urgulanilla",
"consulship",
"Praetorian Guard",
"Julii Caesares",
"Herod Agrippa I",
"Camerinus Antistius Vetus",
"Aqua Virgo",
"Livia Medullina Camilla",
"Steve Pemberton",
"Kalends",
"Christianity in the 1st century",
"Eleusinian Mysteries",
"Colonia (Roman)",
"Lyon Tablet",
"Claudia Octavia",
"Roman legion",
"Lycia",
"History of the Jews in the Roman Empire",
"Gallia Lugdunensis",
"Rhine",
"Gnaeus Sentius Saturninus (consul 41)",
"snakebite",
"clemency",
"Via Claudia Augusta",
"Lucius Vipstanus Poplicola",
"Linda Proud"
] |