by Jason Sylvestre, Special Collections
“Cross my heart and hope to die. / Here’s the digits that make pi: 3.1415926535897932384….”
If it’s been a while since you’ve calculated the area of a circle, the volume of a cylinder, or the surface area of a sphere, you may be a little rusty on pi, the mathematical constant defined as the number of times the diameter of a circle can be wrapped around its circumference.
Increasingly, however, pi is becoming unforgettable with the growing popularity of National Pi Day. Participation in the holiday involves sharing in an elaborate spread of the homophonous pastry, whose shape serves as a reminder of pi’s significant geometric contribution.
Even before Pi Day was officially established, however, pi has had a high pop culture significance, as the above quote from The Simpsons and many other movie and television references attest. (In the particular scene from a 1997 episode, two young girls at a gifted school are reciting the non-repeating digits as a playground chant while playing the game of patty-cake.)[i]
Pi as we know it today is a few thousand years in the making. The concept was first explored by the Babylonians and Egyptians around 1650 BC. A Babylonian tablet dating between 1900-1680 BC gives a value for pi as 3.125, while the Egyptian Rhind Papyrus (ca 1650) defined pi as 3.1605. Greek mathematician Archimedes’ famed work with polygons led him to arrive at the approximation of pi as 3.14. The symbol for pi, π, was first proposed in 1706 by Welsh mathematician William Jones, and became widely used after pioneering Swiss mathematician and physicist Leonhard Euler included the symbol in his 1736 work, Mechanica.
Pi has proved extremely useful when dealing with geometry problems involving circles. Finding the area of a circle is arguably the most well-known usage of pi: A=πr^2. Pi also provides the formula for finding the volume of a cylinder: A=πr^2h. Although scientific applications do not generally require more than 40 digits of pi, modern computing power has allowed mathematicians to calculate pi to more than 13.3 trillion digits!
In 1988, to celebrate the wonderful, irrational number that is pi, physicist Larry Shaw of the San Francisco Exploratorium designated March 14 (3/14), the first three digits of pi, to march around a circular space at the museum with his colleagues while consuming fruit pies.[ii]
In 2009, the U.S. House of Representatives recognized March 14, 2009, as National Pi Day. March 14, 2015, will be the most precise Pi Day to date. At 9:26:53 a.m. and p.m. the date and time will correspond with the first 10 digits of pi, 3.141592653.
In order to celebrate this momentous mathematical occasion, the Richter Library suggests exploring these books and movies—and be sure to enjoy a slice of pie with your pi.
The Number Pi by Pierre Eymard, Jean-Pierre Lafon; translated by Stephen S. Wilson
The Joy of Pi by David Blatner
America’s Best Harvest Pies by Linda Hoskins
Pot Pies by Beatrice Ojakangas
Key lime Cookin’ by Joyce LaFray Young
The Sweetness at the Bottom of the Pie by Alan Bradley
[i] The Simpsons, “Lisa’s Sax.” October 19, 1997.
[ii] “A Brief History of π,” The Exploratorium, http://www.exploratorium.edu/pi/history_of_pi/index.html