Pi Day
Next: March 14, 2027
A slice for every digit.
The story
Where it comes from
Pi Day was born at the Exploratorium, San Francisco's science museum, in 1988. At a staff retreat in Monterey, the physicist and tinkerer Larry Shaw noticed that 14 March, written 3.14, matches the first digits of pi, the never-ending number that links a circle's circumference to its width. On the first Pi Day, at 1:59, the digits that come next, Larry and his wife Catherine set out fruit pies and a tea urn on the museum floor. A few years later his daughter Sara noticed that it was also Albert Einstein's birthday.
How it's celebrated
Maths lovers, schools and museums around the world eat pie, recite as many digits as they can and set circle puzzles. The Exploratorium still holds a public Pi Day each year. Shaw, known as the 'Prince of Pi', led its parade until his death in 2017, a boombox playing the digits of pi, and the parade ends by circling the museum's brass Pi Shrine 3.14 times while everyone sings 'Happy Birthday' to Einstein.
Did you know
- Shaw's Pi Shrine is a circular brass plaque in the centre of a circular classroom built from circular cinderblocks.
- Einstein was born on 14 March 1879, so the party celebrates a physicist as well as a number.
- UNESCO has made the same date the International Day of Mathematics, so 14 March now belongs to all of maths, not only to pi.
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