# What is Pi Day?

March 14 marks Pi Day, an annual celebration of the mathematical sign pi. Founded in 1988 by physicist Larry Shaw, March 14 was selected because the numerical date (3.14) represents the first three digits of pi, and it also happens to be Albert Einstein’s birthday—the perfect pi-incidence.

The first Pi Day celebration took place at the Exploratorium (Shaw’s place of work), a San Francisco-based interactive science museum, and featured a circular parade and the eating of fruit pies. The festivities have gotten larger each year, and now include webcasts and a virtual party in Second Life (an online virtual world). It wasn’t until 2009, however, that it became an official national holiday when the U.S. House of Representatives passed legislation.

Why all the fuss about pi? The Ancient Greek mathematician Archimedes is most commonly credited with being the first to accurately calculate the estimated value of pi. Since it is an irrational, transcendental number, it continues on to infinity—the pi-ssibilities are endless! The seemingly never-ending number needs to be abbreviated for problem solving, and the first three digits (3.14) or the fraction 22/7, are commonly accepted as accurate estimations.

In mathematics, this infinite number is crucial because of what it represents in relation to a circle—it’s the constant ratio of a circle’s circumference to its diameter. Pi is also essential to engineering, making modern construction possible.

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Since the mid-18th century pi has also been represented by the Greek letter π. In fact, the word “pi” itself was actually derived from the first letter of the Greek word perimetros, which means circumference.

In 2015, Pi Day fanatics had a special treat. Celebrations took place on 3/14/15 at 9:26:53 a.m., the numerical date and time together representing the first 10 digits of pi, 3.141592653. To date, pi has been calculated to more than 1 trillion decimal places—and the mathematicians don’t plan on stopping there.

Mathematicians, scientists and teachers hope the holiday will help increase interest in math and science nationwide, through instruction, museum exhibitions, pie-eating (or throwing) contests and much more. It seems this kitschy national holiday can satisfy the left-brained and the sweet-tooth inclined. How will you be celebrating?