Today is Pi Day! That's π, as in the ratio between the circumference of a circle and its diameter, better known as the mathematical constant beginning with 3.14. We celebrate pi on March 14, or 3/14, because the date represents the first three digits of π in decimal form.

Evidence suggests that pi was first approximated by the ancient Babylonians. Many mathematicians have contributed to the history of pi. However, it’s the Greek mathematician Archimedes (287-212 BC) who is generally considered to be the first to calculate an accurate estimation of the value of pi.

In 1989, physicist Larry Shaw created Pi Day, which was celebrated at the San Francisco Exploratorium, where staff and members of the public marched in a circle and then ate fruit pies. In 2009, the United States Congress officially recognized March 14 as Pi Day and encouraged schools to celebrate the day as a way to engage students in mathematics.

Many schools have special events, including contests to see who can recite the most digits of pi from memory. Because pi is an irrational number, its decimal representation is infinite. A computer has calculated pi to more than a trillion (1012) digits, but the world record holder for reciting the most digits from memory is Chao Lu, who recited the first 67,890 digits in 2005.

How many digits of pi can you recite? Enjoy a slice of pie while you watch this video about losing yourself in the digits reciting pi from memory.

If numbers tickle your fancy, then take a look at the latest release of Microsoft Mathematics.