**OpinionCommentary**

# I usually hate Pi Day, but I don’t this year

If you really think about it, the amazing thing about p is not the number itself but the fact that the ratio of a circle’s circumference to its diameter is a constant at all.

I am a mathematician, and I hate Pi Day.

Hate is not quite right. In the words of T-Rex from Ryan North’s superb Dinosaur Comics, “I feel a profound disconnect with this holiday!” I came to math relatively late in my educational career, and I was attracted to the creativity of mathematical proofs, not to numbers or computations.

Pi Day bothers me not just because it celebrates the ratio of a circle’s circumference to its diameter, or the number 3.14159 . It’s also about the misplaced focus. What do we see on Pi Day? Circles, the Greek letter p, and digits. Oh, the digits! Scads of them! The digits of p are endemic in math gear in general, but of course they make a special showing on Pi Day. You can buy everything from T-shirts and dresses to laptop cases and watches emblazoned with the digits of p.

The digits in a number depend on the base we choose to write the number in, and the base 10, or decimal, system is basically an accident of biology and history. If you were partial to binary, you would be celebrating Pi Day on at the stroke of midnight on Nov. 1. In dozenal, or base 12, it would be four days from now.

But geeking out over digits is sort of missing the point. If you really think about it, the amazing thing about p is not the number itself but the fact that the ratio of a circle’s circumference to its diameter is a constant at all. On our podcast My Favorite Theorem, my cohost Kevin Knudson and I talked to Dave Richeson about why that fact is his favorite theorem. And last year, mathematician Kelsey Houston-Edwards made a video explaining how p can be any number between 3 and 4 if we measure distance differently.

I approached Pi Day this year with my usual lack of enthusiasm. I scoffed at the marketing emails I got from companies asking me to plug their Pi Day sale on my blog or offering a 3.14 percent discount on a subscription. I shook my head at T-shirts and mugs covered with the digits of p and continued to be profoundly bored by the pi versus tau debate. (Sorry, Steve and Matt. It’s not you, it’s me.) But as I started writing this article, I learned that Larry Shaw, the curator at the Exploratorium in San Francisco who founded Pi Day, passed away last August.

On March 14, 1988, at 1:59 p.m. (or 3/14, 1:59), Shaw first led Exploratorium visitors on a circular procession around the museum and fed them pie. Since then, the celebration has snowballed. This Pi Day, MIT applicants find out their admission decisions, Princeton celebrates both the circle constant p and the birthday of famous resident Albert Einstein, and classrooms and libraries around the country have nerd-friendly gatherings where students eat pie and maybe have a little fun with math. I scoff at the goofy marketing gimmicks, but I have to respect the fact that Shaw started a math holiday recognized by people all over the world that has been so successful that it now has scoff-at-able marketing gimmicks.

So, just for this year, I’m going to hold back my Pi Day eye rolls. You won’t find me reciting digits or measuring the number pi using pies, but I will spare a moment of gratitude for Larry Shaw, Pi Day creator, whose holiday has inspired and entertained students and teachers for 30 years. If you are interested in moving beyond digit veneration, circle measuring, and pie eating in your Pi Day celebrations (OK, maybe not that last one), I have some suggestions on my blog, Roots of Unity.

*Evelyn Lamb is a freelance math and science writer based in Salt Lake City. She has a Ph.D. in math from Rice University and has written for Scientific American, Slate, Nautilus, and other media outlets. Follow on Twitter: @evelynjlamb.*

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