### National Pi Day

Today is National Pi Day, March 14, written as 3/14. Even though the House of Representatives passed a resolution recognizing National Pi Day back in 2009, I had never heard of it. I was first aware of this celebrated day when a fellow blogger—Go Jules Go—announced that she would be submitting a pie in the Pi Day Pie Challenge being held by another blogger, Accidental Step Mom. What a fun idea! I, of course, would not enter the contest, since I am even less of a baker than I am a cook—and I am not a cook.

Still, the idea of a National Pi Day intrigued me. Even though I am more a word-person than a numbers-person, the world of numbers and its beauty and symmetry generally fascinates me. In an earlier post “The Music of Math: Just Listen” I had already explored the concept (and the sound) of Tau. Apparently, there is a controversy over the best representation of the circle constant, the traditional Pi or the proposed Tau. Since it is National Pi Day, I thought I better find out a bit more about Pi than that it is written in decimal format as 3.14.

Pi is an irrational and transcendental number that has captivated mathematicians for thousands of years. By definition, it is the mathematical constant that is the ratio of a circle’s circumference to its diameter, and is approximately equal to 3.14159. This decimal representation just keeps going and going and never repeats a pattern. These qualities make Pi an intriguing puzzle of sorts to mathematicians the world over. It has been represented by the Greek letter “π” since the mid-18^{th} century.

The San Francisco Exploratorium has been celebrating Pi Day since 1988. Typically, celebrants walk around circular areas at the facility and eat pie at the end of the march. For many years, Massachusetts Institute of Technology has postmarked its acceptance letters to new students on Pi Day. Starting in 2012, MIT has announced it will post those decisions (privately) online on Pi Day at exactly 6:28 pm, which they have called “Tau Time,” to acknowledge the controversy between Pi and Tau as the best circle constant. Princeton combines its Pi Day Activities with its annual Einstein Celebration, since March 14 is also Einstein’s birthday. There are lots of ways to celebrate Pi Day.

The Official Pi Day Website shares a wealth of information about Pi, including ideas for the classroom, a rap video about reciting Pi, news reports involving Pi, and ideas and archives about celebrations. This site also notes that it is fun to memorize and recite Pi for as many digits past the decimal point as you can. In case you want to try memorizing this number, here is a listing offered by the website providing hundreds of digits beyond the decimal point.

The Teaching Pi Website shares classroom ideas for teaching Pi and provides quotes from teachers and students about the fascination surrounding Pi. One 8^{th} grader captures this general fascination quite well: “If you think about it, pi never ends. There’s an infinite space between 3 and 4. It never ends, and that’s weird.” For me, weird is good! The website also suggests what a fun challenge it is to memorize and recite Pi, so it also gives lists of winners by grade level, noting how many digits were recited by each winner.

One student who was going to try to memorize a string of 140 digits, said it was easier to think of the challenge as memorizing 20 phone numbers than just a random string of numbers. That’s a helpful memorization tip, but no matter what the websites say, memorizing Pi does not sound like a fun challenge to me. But to give a sense of what such a recitation might sound like, here’s a video that has someone singing the number quite a few spaces beyond the decimal point:

I am still not certain how I will be celebrating National Pi Day. Maybe I’ll swing by Marie Callender’s after lunch to buy a piece of pie. I know I will listen to the video embedded below called “The Music of Pi” by Michael Blake. The fact that music is hidden in the numbers is mesmerizing to me, much more fun than someone—not me!—memorizing and reciting the numbers in order. The following video is similar to “The Music of Tau” video I presented in an earlier post. Although A Frank Angle presented this exact Pi video in his post “On a Piece of Pi” last year, it is worth sharing here as well. But don’t forget to visit his site—it offers a lot more fun information about Pi.

**HAPPY NATIONAL PI DAY!**

**HOW DO YOU PLAN TO CELEBRATE?**

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**A FINAL CAUTION:** The American Pie Council would be very disappointed if anyone were to confuse Pi Day (3/14) with Pie Day (January 23). They are really quite different, although it seems they both involve eating lots of pie.

P.S. To keep your focus on the fun of mathematics, here are two more videos. They are not about Pi, but they are fun! Enjoy!

“When Not Knowing Math Can Cost You $15,000”

“Doodling in Math Class: Infinity Elephants”