The basic definition of the number pi is that it’s doesn’t have an exact value – it’s an infinite calculation. But it *is* possible to know the exact number of people required to sing a fully orchestrated song about it – sixteen.

I visited San Francisco’s Exploratorium a few days before this year’s Pi Day celebration, to watch a rehearsal of the 16-person band in question. They’re called Buffon’s Needle, a reference to an 18th Century French mathematician who approximated the value of pi by throwing pine needles on the ground.

“He took needles, drew lines on floor – the needles were about half the width of each line – and he threw the needles on floor,” says Khamara Pettus, an Exploratorium Explainer and the band’s lead singer. “And then he counted to see how many crossed the lines, and then he divided them by number of lines. He came to conclusion that it’s 22/7 which approximates pi the closest.”

For this reason, some people also celebrate pi on July 22nd. To the members of Buffon’s Needle, pi is a number worthy of celebration. “It has a sense of wonder and a sense of magic to it,” says band member Chas Thomsen. “It’s not like 8, or 272. It’s a number that just doesn’t end.”

“The most pi places someone’s memorized is 100,000,” adds band member Adam Green. “The mneumonics are amazing.”

The verified memorization record is actually 67,890 places – set in 2006. The number of digits that have been officially calculated, though, is two quadrillion. It took 1,000 computers almost a month to do that one.

Scientists like Larry Shaw love that stuff. Shaw is a physicist who’s worked at the Exploratorium for 33 years. One of the highlights was launching the pi day celebration in 1988.

“Learning about pi, what the digits are, it’s a never-ending task,” he says. “So we thought we should make a shrine to this never-ending-taskness.”

The Exploratorium does have a literal shrine: it’s a small plaque embedded in the floor, that’s the focus of much pomp every year. Shaw says that part’s always fun. But there are other ways people relate to pi.

“You can sing pi, you can count pi,” says Shaw. “Once I got a sheet of paper listing out 10,000 digits of pi, with all the ‘42’s circled. Other people have used pi as a constant for writing poetry.”

Like this poem, where the number of letters in each word corresponds to a digit in pi.

That there, obstinate in you, O Strange Constant,

A Divine Sign O exists is unlikely unless

Is O revealed Something Brilliant, negating belief!

“It’s just abstract,” says Shaw.

And for centuries, it’s been inspirational. So on Wednesday, if you think of it, take a moment for pi. But remember, this year’s celebration is only accurate to two digits. If you want to really celebrate, wait three years: for Saturday, March 14, 2015. At 9:26PM. And 35 Seconds.

The Exploratorium is hosting Pi Day activities beginning at 1 pm this coming Wednesday, March 14. It will be the last Pi Day celebration at the museum's current location at the Palace of Fine Arts.

*Audio available after 5pm P.S.T. on March 12, 2012. *