What’s the best way to celebrate Pi Day? That’s the geeky holiday that takes place on 3/14 … in other words, today. For some, it’s a day for baking geeky pies, or getting a $3.14 deal on slices of pizza. For Google, it’s a day for breaking a world record, by calculating the irrational number’s value to 31.4 trillion digits of precision.

31,415,926,535,897 digits, to be exact.

Pi enters into every walk of life, if that walk happens to be circular. On one level, it’s the ratio of a circle’s circumference to its diameter. On another level, it’s a mystical number to contemplate, because the digits just go on, and on, and on …

Physicist Larry Shaw invented a ritual to celebrate that mystical value, and that ritual was first celebrated at San Francisco’s Exploratorium for the first time 30 years ago. It involves walking in a circular procession on 3/14 at 1:59 p.m. (in honor of 3.14159), singing happy birthday to Albert Einstein, and reveling in a pie feast (fruit and/or pizza). The ritual is celebrated at the Exploratorium to this day.