# Pi Day turns 25

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Annette Spaulding receives a piece of pie during the 11th Annual Feast of Sharing at the Washington Convention Center in Washington on November 24, 2010. The event, hosted by Safeway, serves free traditional turkey meal for the homeless and elderly D.C. residents while also providing a job fair, free clothing and health screenings. UPI/Kevin Dietsch | License Photo

It's Pi Day!

That's right: March 14 is the day when the nerdiest among us celebrate the joy of the irrational number, π, so named because its first digits -- 3.14 -- line up with the American way of writing the date, 3/14.

As far as mathematicians know, Pi goes on past its most famous digits forever, without ever falling into a repeating pattern.

Pi, named for the 16th letter of the Greek alphabet, has been in use possibly since ancient Egyptians first built their mathematically accurate monuments. It is useful not only in geometry, that bane of high school sophomores everywhere, but in many of the equations physicists use to describe some of the most basic principles of the universe.

It appears in one of Einstein's field equations, critical to the theory of relativity, and related to the speed of light.

Urban legend says Pi Day was founded when physicist Larry Shaw noticed the date in 1988 and thought it would be fun to celebrate. As the story goes, Shaw and his colleagues at the San Francisco science museum Exploratorium ordered pie for the staff, and an annual tradition was born.

Pie -- the edible kind -- has become as much a part of the celebration of Pi Day as the math, helped along by the convenient coincidence that the first encounter most students have with the number is in the equations for area (pi multiplied by the radius squared) and circumference (pi multiplied by the diameter) of a circle.

Student celebrations include every kind of pie from fruit to pizza. Birthday cake would also be appropriate: Albert Einstein was born 134 years ago today.

So kick back with 45° of pizza, grab a copy of "Life of Pi" and enjoy the year's nerdiest day!

July 5, 2012 "'Anyone want to try a piece of my strawberry pie,' the President asked those at adjacent tables during a stop for lunch at Kozy Corners restaurant in Oak Harbor, Ohio. A young boy said yes and came over for a big bite of pie." (Official White House Photo by Pete Souza)

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