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Today's featured article π (or pi) is a mathematical constant that is the ratio of a circle's circumference to its diameter. It is approximately equal to 3.14159. π is an irrational number, which means that it cannot be expressed exactly as a ratio of two integers, although it is roughly approximated by 22/7. It is a transcendental number – a number that cannot be produced with a finite sequence of algebraic operations (sums, products, powers, and roots). The transcendence of π implies that it is impossible to solve the ancient challenge of squaring the circle with a compass and ruler. The digits in the decimal representation of π appear to be random. Because its definition relates to the circle, π is found in many formulae in trigonometry and geometry, such as Euler's identity, eiπ + 1 = 0. It is also found in formulae from other branches of science, such as cosmology, number theory, statistics, fractals, thermodynamics, mechanics, and electromagnetism. (more...) Recently featured: Eduard Streltsov – Nature fakers controversy – Manchester Ship Canal Did you know... From Wikipedia's newest content: ... that the psychedelic mushroom Psilocybe makarorae (pictured) was described by two New Zealand mycologists known to assist police in prosecuting those who illegally collected the species? ... that the Vinkovci Treasure, consisting of 48 items of 4th-century Roman silverware found in March 2012, has been called one of Croatia's most important archaeological finds? ... that on the penultimate lap of the 2007 Detroit Indy Grand Prix, second-placed Buddy Rice ran out of fuel, and was hit by Scott Dixon? ... that when teenage Alberta Schenck took a stand against segregation in Alaska, her actions were a full decade before either Rosa Parks's stand or the Brown v. Board of Education decision? ... that the book that Willie Morris called the "best novel about American politics in our time" was never a commercial success? ... that successful 1990s video game Cannon Fodder received a new sequel, Cannon Fodder 3, from an "unknown" Russian publisher in 2012? ... that during the 1860 clashes, a Muslim force from Sheikh Miskin saved the Christian population of Daraa from attack by local Druze?

In the news A gunman kills 12 people and injures more than 50 others during a midnight film screening (location pictured) in the U.S. state of Colorado. Bollywood actor and film producer Rajesh Khanna dies at the age of 69. Syrian defense minister Dawoud Rajiha and deputy defense minister Assef Shawkat are killed in a bomb attack on the Military Intelligence Directorate headquarters in Damascus. At least seven people are killed in an attack on a bus carrying Israeli tourists in Burgas, Bulgaria. The National Forces Alliance, led by Mahmoud Jibril, gains a plurality in the Libyan General National Congress election, the first election since the deposition of Muammar Gaddafi. On this day... July 22: Feast day of Mary Magdalene; Parents' Day in the United States (2012); Pi Approximation Day 1793 – Two days after becoming the first recorded European to complete a transcontinental crossing of North America north of Mexico, Scottish-Canadian explorer Alexander Mackenzie reached the westernmost point of his journey and inscribed his name on a rock. 1802 – Gia Long conquered Hanoi and unified modern-day Vietnam, which had experienced centuries of feudal warfare. 1934 – Bank robber John Dillinger (pictured), whose exploits were sensationalized across the United States, was shot dead by police in an ambush outside the Biograph Theater in Chicago. 1991 – American serial killer Jeffrey Dahmer was arrested in Milwaukee, Wisconsin, after police discovered human remains in his apartment. 2002 – The Israeli Defense Forces dropped a bomb on the home of Salah Shehade, the leader of the military arm of Hamas, killing him and his family. More anniversaries: July 21 – July 22 – July 23 It is now July 22, 2012 (UTC) – Refresh this page

Today's featured picture A 3D ray tracing of a glass molecular model, demonstrating the algorithm's ability in simulating depth of field (DOF), which is the distance between the nearest and farthest objects in a scene that appear acceptably sharp in an image. When much of the foreground and background of an image is sharp, its DOF is deep. The opposite is called shallow focus. Image: Purpy Pupple Recently featured: Johnny Evers – Red-necked wallaby – Slate pencil urchin

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