What Is Pi Day? 4 Fun Facts About Mathematical Celebration

Every March 14 (3/14) is the annual celebration of Pi Day, commemorating the mathematical constant π (pi) since 3, 1, and 4 are the first three significant digits of π in decimal form. Pi is the ratio of a circle’s circumference to its diameter. Since it's a constant, Pi will be the same for all circles of any size. Pi has been calculated to over one trillion digits beyond its decimal point. As an irrational and transcendental number, it will continue infinitely without repetition or pattern. While only a handful of digits are needed for typical calculations, Pi’s infinite nature makes it a fun challenge to memorize, and to computationally calculate more and more digits. Here are other fun facts about this mathematical celebration.

1) The earliest known official or large-scale celebration of Pi Day was organized by Larry Shaw in 1988 at the San Francisco Exploratorium, where he worked as a physicist, with staff and public marching around one of its circular spaces, then consuming fruit pies. The Exploratorium continues to hold Pi Day celebrations.

2) Pi Day is observed in many ways, including eating pie, throwing pies and discussing the significance of the number π. Some schools hold competitions as to which student can recall Pi to the highest number of decimal places.

3) Massachusetts Institute of Technology has often mailed its application decision letters to prospective students for delivery on Pi Day. Since 2012, MIT posts those decisions (privately) online on Pi Day at exactly 6:28 pm, which they have called “Tau Time,” to honor the rival numbers Pi and Tau equally.

4) The town of Princeton, New Jersey, hosts numerous events in a combined celebration of Pi Day and Albert Einstein's birthday, which is also March 14. Einstein lived in Princeton for more than twenty years while working at the Institute for Advanced Study. In addition to pie eating and recitation contests, there is an annual Einstein look-alike contest.