## 14 March 2011

### Happy Pi Day! Eat an apple Pi! Recite 22,514 digits of the decimal expansion of Pi!

Click image for larger.

Today's also Albert Einstein's birthday.

Wikipedia:

Pi Day is a holiday commemorating the mathematical constant π (pi). Pi Day is celebrated on March 14 (or 3/14 in month/day date format), since 3, 1 and 4 are the three most significant digits of π in the decimal form. In 2009, the United States House of Representatives supported the designation of Pi Day.[2]

Pi Approximation Day is held on July 22 (or 22/7 in day/month date format), since the fraction 22⁄7 is a common approximation of π.[3] This date is also referred to as "European Pi Appreciation Day" because of the European practice of placing the day before the month.

History

Larry Shaw created Pi Day in 1989.[4] The holiday was celebrated at the San Francisco Exploratorium, where Shaw worked as a physicist,[5] with staff and public marching around one of its circular spaces, then consuming fruit pies.[6] The Exploratorium continues to hold Pi Day celebrations.[7]

On Pi Day 2004, Daniel Tammet recited 22,514 decimal digits of π.[8]

On March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (HRES 224),[2] recognizing March 14, 2009, as National Pi Day.[9]

For Pi Day 2010, Google presented a Google Doodle celebrating the holiday, with the word Google laid over images of circles and pi symbols.[10]

Date Abstractions from Pi

Pi Day is observed on March 14 because of the date's representation as 3/14 in month/day date format. This representation adheres to the commonly used approximation of 3.14 for π.

The fractional approximation of π = 22⁄7 resembles the date July 22 in the day/month format, where it is written 22/7. Pi Approximation Day is therefore celebrated on July 22.

In 2015, Pi Day will reflect five digits of π (3.1415) as 3/14/15 in month/day/year date format.

Celebration

There are many ways of celebrating Pi Day. Some of them include eating pie (pi and pie being homophones) and discussing the relevance of π.[1]

The Massachusetts Institute of Technology often mails its application decision letters to prospective students for delivery on Pi Day.[11]