Today is Pi Day, in honor of the mathematical constant pi (π), an irrational number that begins 3.14 — like today's date, March 14th or 3/14.
π is a letter of the Greek alphabet, and it's the symbol for the ratio of a circle's circumference to its diameter. In other words, if a circle has a diameter of 10 inches, we could find out its circumference by multiplying 10 inches by π, and we'd find out that the circle with a 10-inch diameter has a circumference (or perimeter) of approximately 31.4159265. It can only ever be approximate — never exact — because π is an irrational number, meaning that it goes on forever without repeating or having patterns. Using powerful computers, π has been calculated in recent years into trillions of decimal places.
Pi Day began in 1988, started by a physicist named Larry Shaw. And just last year, in 2009, the U.S. House of Representatives passed a non-binding resolution designating today as National Pi Day.
Pi Day celebrations around the nation today involve eating dessert pies or pizza pies, throwing cream pies, and listening to lectures on the importance of the irrational number — sometimes all of these things occurring in unison.
There are legions of people worldwide devoted to memorizing π to as far as they can memorize it. And today around the world, there are π recitation contests. The world record, according to the Guinness Book, is currently held by Lu Chao, a grad student from China, who over the course of 24 hours and 4 minutes recited pi to the 67,890th decimal place without error.
To aid in the memorization of the never-ending, pattern-less number, people have written poetry and stories in a mnemonic called "Pilish," which is a way of constrained writing "in which the number of letters in each successive word "spells out" the digits of π." One of the earliest and best-known examples of it was a sentence by English physicist Sir James Jeans, who wrote: "How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics!" 'How' has three letters, 'I' has one, "need" has four — so it forms 3.14, the start of π — and each successive word's letter count represents the next digit in π.
Then, in 1996, a piphilologist (as these people are called), wrote a 3,834-digit Cadaeic Cadenza, which begins with a retelling of Edgar Allan Poe's "The Raven"; every single word adheres to the constraints that render letter counts into accurate successive π digits.
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