Talk of the Nation, March 14, 2008 · On Friday, math enthusiasts celebrate pi, the infinite number representing the relationship between a circle’s diameter and its circumference. Represented by the Greek letter pi, the number is usually shortened to 3.14, so festivities take place on March 14 or 3/14.
Across the country, math aficionados trade pi recipes, hold pizza parties, and recite as many digits of the never-ending number as they can remember. (Listen to a recitation by Mark Umile, North American record-holder for memorizing pi.)
Physicist Ron Hipschman talks with host Ira Flatow about the all-day pi celebration taking place at the Exploratorium in San Francisco.
A lot of people are excited about the power of pi. But not everyone knows it has an official celebration — Pi Day, on the fourteenth day of the third month, 3.14. Those are the first three digits of pi, that transcendental number, the icon with the digits after the decimal point that go on forever.
Strictly speaking, pi represents the constant ratio of a circle’s diameter to its circumference. There is no pattern to pi. But it’s a cool number with real-life applications. Today, as Dan Hellerich of PiDay.org reports, numbers geeks all over the world bake pies, write “pi-kus” and recite pi to as many decimal points as possible. “I know 15,” he says. “Some people know 10 times that, but you really only need about 10 to do accurate math in geometry or physics.”

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