I'm dreading it. No hope of solving any equations that day, what with the pie-eating contests, the bickering over the merits of pi versus tau (pi times two), and the throwdowns over who can recite more digits of pi. Just stay off the streets at 9:26:53, when the time will approximate pi to ten places: 3.141592653.

The New Yorker's Steven Strogatz on why pi matters.

As Pi Day approaches, it time for a refresher course, courtesy of Steven Strogatz, on what pi actually means and how you can visualize calculating it. It's all about rearranging the pieces of a circle in a calculus-ish sort of way:

And in celebration, this is my new favorite fact about pi: we have calculated pi out to over 6.4 billion digits but only 39 of them are needed to calculate the circumference of a circle as big as the universe "with a precision comparable to the radius of a hydrogen atom". (via @santheo)

Cadaeic Cadenza is a 3834-word story by Mike Keith where each word in sequence has the same number of letters as the corresponding digit in pi. (thx, mark, who has more info on constrained writing) Related: The Feynman point is the sequence of six 9s which begins 762 digits into pi. "[Feynman] once stated during a lecture he would like to memorize the digits of pi until that point, so he could recite them and quip 'nine nine nine nine nine nine and so on.'"

The New Yorker recently ran a feature on how a couple of mathematicians helped The Met photograph a part of The Hunt of the Unicorn tapestries. That same week, they ran from their extensive archives a 1992 profile of the same mathematicians, brothers David and Gregory Chudnovsky. The Chudnovskys were then engaged in calculating as many digits of pi as they could using a homemade supercomputer housed in their Manhattan apartment. There's some speculation that director Darren Aronfsky based his 1998 film, Pi, on the Chudnovskys and after reading the above article, there's little doubt that's exactly what he did:

They wonder whether the digits contain a hidden rule, an as yet unseen architecture, close to the mind of God. A subtle and fantastic order may appear in the digits of pi way out there somewhere; no one knows. No one has ever proved, for example, that pi does not turn into nothing but nines and zeros, spattered to infinity in some peculiar arrangement. If we were to explore the digits of pi far enough, they might resolve into a breathtaking numerical pattern, as knotty as "The Book of Kells," and it might mean something. It might be a small but interesting message from God, hidden in the crypt of the circle, awaiting notice by a mathematician.

The Chudnovsky article also reminds me of Contact by Carl Sagan in which pi is prominently featured as well.

According to Wolfram Research's Mathworld, the current world record for the calculation of digits in pi is 1241100000000 digits, held by Japanese computer scientists Kanada, Ushio and Kuroda. Kanada is named in the article as the Chudnovskys main competitor at the time.

(Oh, and as for patterns hidden in pi, we've already found one. It's called the circle. Just because humans discovered circles first and pi later shouldn't mean that the latter is derived from the former.)

A pi pie. Note the edging on the crust.