Happy Pi Day!

Since 1988* people have been celebrating the number pi (π) on March 14th, or 3.14. Some celebrants are more precise, and wait for 1:59 PM and 26 seconds to begin their festivities, as pi approximates to 3.1415926.

Of course, any numerical expression of pi is approximate, as pi is an irrational number (it cannot be expressed as a ratio of two integers), and thus it never stops and never repeats itself. Pi is also a transcendental number. As I hope all of you know, pi (pronounced like "pie", hence the visual pun to the upper-right) is the ratio of a circle's circumference to its diameter. The history of mathematical progress in finding more precise values for pi is a fascinating one (In the Bible, 1 Kings 7:23-26 gives the value as 3), and pi currently has been calculated to over a trillion places. You can see pi up to a million places here. Pi (π) is a greek letter, an abbreviation for the greek word for perimeter.

Pi has long held a sentimental value for me. When I was in fourth grade, my dad (who is a high school math instructor), offered extra credit to students who could memorize 35 places of pi. He and I decided to have a contest to see who could learn the most places, and I (with my 9 year old plastic mind) was able to memorize 105 to his 65 (I can currently rattle off 120 from memory). This has served no practical purpose in my life, but it has been an excellent conversation starter and ender. The closest it came to being useful was in high school, when my good friend Frank told Brian, his fellow football team member, that I knew 105 places. Brian was skeptical, saying I was probably bluffing and offered a $10 bet to prove it. Frank took the bet, and Brian approached me with a printout from the internet. Frank won the $10. Pi memorization is an age-old nerd exercise, and the Guiness Book of World Records tracks the individuals who have memorized the most. Apparently Daniel Tammet is the current record holder, with 22,514 places.

(More on Pi and Pi Day at Wikipedia, and Science Friday's tribute to Pi Day here.)

*I was not aware until I started writing the post, but Pi Day began in 1988 at the San Francisco Exploratorium! You can see video of their 20th annual celebration here. The Exploratorium was one of my favorite places to go as a kid, with interactive science demonstrations that you weren't just allowed to touch, but encouraged to touch! Highly recommended if you're in the SF area.