Every year has a Pi Day, but this year’s , which takes place next Saturday, will be a once-in-a-century happening.
Pi, of course, is the mathematical constant that describes the relationship between the circumference of a circle and its diameter. And so Pi Day occurs every year on March 14 to celebrate the first three digits of pi, 3.14.
But there’s something odd about pi, which you probably remember from your school days. It’s infinite. You can keep dividing a circle’s circumference by the diameter and you’ll never get a final number, there will always be something left over. And the sequence never repeats. Pi has been calculated to more than a trillion digits past the decimal.
So this year, on March 15, 2015 we can add two numbers and celebrate 3/14/15. If you want to be even more precise, you can carry the calculation out further and celebrate at precisely 9:26:53 – a.m. or p.m. You’ll be forgiven if you take two seconds to mark the occasion: some argue that 9:26:54 on 3/14/15 is more the accurate time because the 11th digit of pi is 5, which would cause the 10th digit to round up to 4, rather than 3. (Though by the same logic, we should celebrate Pi Day next year, because the sixth digit, 9, should round the fifth digit up to 6.)
The first Pi Day was organized by Larry Shaw, a physicist at the San Francisco Exploratorium, in 1988. Visitors joined the museum’s staff in marching around the circular spaces and then eating fruit pies. The Exploratorium still has annual Pi Day celebrations.
Congress has even gotten into the act. The U.S. House of Representatives passed a non-binding resolution in 2009 recognizing March 14 as Pi Day.
There’s also a Pi Approximation Day, July 22, which makes sense if you write the dates European-style, with the day first, followed by the month: 22/7 is a close fractional approximation of the value of pi.
Lots of colleges and other organizations celebrate by eating pie, throwing pies or holding contests to see who can recite the most decimal places for pi. At Princeton University they also celebrate the March 14 birthday of Albert Einstein, who worked there for 20 years. In addition to pie eating and pi recitation, there’s an Einstein look-alike contest.
Even the ancients knew that a circle is a little more than three times its width around. In the Bible book of 1 Kings (7:26), a circular pool is described as 30 cubits around and 10 cubits across.
The Greek mathematician Archimedes determined that pi was approximately 22/7. The Greek letter “pi” was first used in 1706 by Welsh mathematician William Jones. History Today has an interesting article about Jones and the development of the pi symbol.
You might want to mark this once-in-a-lifetime day by buying a commemorative tee-shirt; you can find many varieties for sale on Amazon.
Better yet, eat pie. Here’s a great recipe for a pecan pie from my sister, Sue Holliday, who makes it every Thanksgiving.
But before I sign off, I have to share an old joke.
A young lad in Appalachia is the first in his family to go to high school. When he comes back to the holler, his pappy asks him what he learned in school, and the boy says he learned geometry.
“Well say something in geometry,” says the father.
“Um, er…well, today I learned pi-r-squared,” says the boy.
“Hah!” says the father. “Shows what good all this high-falutin’ learning is! Everyone knows pie are round – cornbread are square!”