With a confectionery Doodle on Wednesday, Google paid homage to Pi Day, the nerdiest holiday of the year. Pi Day occurs every year on March 14 (3.14) in celebration of the the numerical constant pi.

Pi represents the ratio of a circle’s circumference to its diameter. That is, for every circle, its circumference is pi times as long as that circle’s diameter. Its discovery is generally credited to the Ancient Greek mathematician Archimedes around 250 B.C. But it’s more than just a number — pi is a *lifestyle*.

Pi Day was first formally recognized by physicist Larry Shaw in 1988, and since its inception thirty years ago Pi Day has become a mainstay in high school geometry classrooms across the country. Shaw organized the inaugural festival at the San Francisco Exploratorium, an experience-based science and discovery space (it resists the label “museum”) founded by Frank Oppenheimer in 1969.

Mathematical revelers at the Exploratorium partake in a profound ritual every Pi Day. Baked goods in hand, a parade of mathematicians and enthusiasts form a ring around a Pi-engraved monument. Then, in concert, they circle around the marker three and one-seventh times, a close approximation to pi.

If you’re missing out on the Exploratorium observance, you can make up for the lack of community with an extra delicious pastry. Chef Dominique Ansel, who created the pie featured in Google’s Doodle, posted a recipe for his famous apple pie as a pi day gift to all.

Unfortunately for pie and circumference lovers around the world, many places don’t get the chance to truly join the Pi Day celebrations. The United States is basically the only nation that writes the date with the month first, so the punny-ness of Pi Day is lost elsewhere.

But geeks looking for another reason to party can simply swap out Pi Day for another worthy cause: the birthday of Albert Einstein. After all, Einstein did some math in his life, so feel free to talk about numbers and maybe eat some baked goods, too.

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