What is pi? At first, it seems that pi is a sort of pastry which can be filled with apple or cherry or many other kinds of fruit, best served hot with some ice cream. Pi is also a movie - pi must be terribly special to have a movie made about it... But pi is also a number, known as Archimedes' constant, a special number with its own special symbol: π! It was named by the Greeks, who found that the ratio of the circumference of a circle to its diameter was always the same, no matter what size the circle. They represented this ratio by one of the letters of their alphabet, π Pi has an extreme use in geometry, math and physics and is often approximated to 3.14159. But in fact it is an irrational number and so has an infinite number of digits. Computers have been used to calculate pi to billions of decimal places and the world record for Pi is 1,241,100,000,000 digits (That's 1 quadrillion 241 trillion 1 million digits!).
There is a great following of people who like to memorize large numbers of digits. A great amount of prestige may be gained among these people by knowing pi to the largest number of decimal places. So, in order to start you off, here are the first few digits of pi - from memory, of course!
3.1415926535897932384626433832795028841971693993751058209749445923... (See the article Pi to 10000 Digits for more digits not from memory)
Pi in Culture
There is an entire field of humorous yet serious study that involves the use of mnemonic techniques to remember the digits of π, which is known as piphilology.
March 14 (3/14) marks Pi Day which is celebrated by many lovers of p. On July 22, Pi Approximation Day is celebrated (22/7 is a popular approximation of p).
Furthermore, many talk of "pi o clock" [fifteen seconds past fourteen minutes past 3 (3:14:15) is slightly less than pi o clock; 3:08:30 would be closest to π hours past noon or midnight in whole seconds].
Another example of math-humor is this approximation of p: Take the number "1234", transpose the first two digits and the last two digits, so the number becomes "2143". Divide that number by "two-two" (22, so 2143/22 = 97.40909...). Take the two-squaredth root (4th root) of this number. The final outcome is remarkably close to π: 3.14159265.
See also: The 1st Stop on the Pi Digit Tour.
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