Pi Day Celebrates a Number We Couldn't Live Without

Mar 12, 2020

Saturday, March 14 is Pi Day, a day to celebrate that unique number represented by the Greek letter pi.  It's about 3.14 (hence its celebration on 3/14), but University of South Carolina mathematician Josh Cooper says it's an irrational number, meaning it goes on forever after the decimal point.  

It's most well known for calculating the area of a circle (the famous formula Πr2, misunderstood in the old joke "pie are round, cornbread are square."), but Cooper said pie is used for all kinds of things in math and physics.  A practical application of pi, he said, would be "if you wanted to pre-compute how much air I should put in this tire, there's a pi involved in the formula.  What's the surface area of my basketball?  Again, pi comes up."

Because it is an endless number, pi has gained a unique application as a test of computing hardware, said Cooper.  "One of the test batteries that new machines are put through is, 'let's see how far we can get in computing digits of pi.'  If you have an efficient formula for doing that, you could go and compute the quadrillionth digit or something." 

Many schools observe Pi Day by serving pie (the dessert) to students.  Chelsea Haines, a math teacher at Columbia's Richland Northeast High School, plans to help her students learn by offering a piece of pie as a reward for students who correctly answer a math question using pi.   "It gives us a chance to be a math nerd for a day,"  she said, explaining that Pi Day was created by physicist Larry Shaw in California in 1988, adding that it's impossible to think of a world without pi because without it, we couldn't calculate anything with a curved surface. 

Likewise, Cooper could not comprehend how science could function without pi.  "It's so fundamental it's hard to even answer that, because it comes up whenever there's electrical signals, alternating current or there's radio waves or transmission, or anything round that needs to be measured, whether it's three-dimensional like a sphere or a dome, or round like a circle, a plate or a can.  Whatever , pi's in there." 

The number of pi has been around for thousands of years and was used in ancient Greece, Egypt and Babylon, though their calculations weren't quite as exact as today's figure.   The Greek letter pi was first applied to the 3.14 number in 1706  by Welsh mathematician William Jones.  

One more happy factoid to add to the Pi Day list:  Several years after Larry Shaw established March 14 as Pi Day, his daughter made a discovery that reinforced the wisdom of that choice of  date: it's also Albert Einstein's birthday!