Poor Pi

There are two kinds of people who get excited about Pi Day, celebrated on March 14 (3.14, get it?): People who like pie, and people who may have somewhat nerdy predispositions.

I’m more of a cake person.

That being said, I wasn’t sure just how to commemorate Pi, that ever-present number forever associated with circles and spheres. Who on earth, I wondered, uses Pi in the course of a day’s work?

“Yes, that would be a stretch,” Phyllis Cook said when I asked if she used Pi in her daily work. She’s a principal architect at in Ellicott City.

“I’m trying to rack my brain to think if I’ve ever used it in my whole career.”

“The only thing that would be obvious,” she said, “is if you’re calculating the area of a circle. And since we’ve gone into the computer age, if you ask the computer to calculate the area of a certain room … the computer would plug it in for us.”

The computer would plug in that equation we all remember from high school: a=πr^{^2}, or area of a circle equals Pi times the radius of the circle squared.

Pi is an irrational number – it cannot be expressed as the ratio of two integers (-3, -2, -1, 0, 1, 2, 3, etc.), and it goes on and on.

Forever.

Here are just a few digits:

3.1415926535 8979323846 2643383279 5028841971 6939937510 5820974944 5923078164 0628620899 8628034825 3421170679 8214808651 3282306647 0938446095 5058223172 5359408128 4811174502 8410270193 8521105559 6446229489 5493038196 4428810975 6659334461 2847564823 3786783165 2712019091 4564856692 3460348610 4543266482 1339360726 0249141273 7245870066 0631558817 4881520920 9628292540 9171536436 7892590360 0113305305 4882046652 1384146951 9415116094 3305727036 5759591953 0921861173 8193261179 3105118548 0744623799 6274956735 1885752724 8912279381 8301194912 9833673362 4406566430 8602139494 6395224737 1907021798 6094370277 0539217176 2931767523 8467481846 7669405132 0005681271 4526356082 7785771342 7577896091 7363717872 1468440901 2249534301 4654958537 1050792279 6892589235 4201995611 2129021960 8640344181 5981362977 4771309960

So when Cook plugs Pi into a computer, she can get a level of accuracy far beyond what she would get if she used the first few numbers. The sad truth for Pi is that not even an architect really uses the number itself for calculations.

“People always tell me, ‘You must be great at math because you’re an architect,’” Cook said. “We do use math, but you definitely don’t have to have Pi memorized."

Still, I couldn’t help but ask: How many numbers of Pi can you recite?

“3.1415,” she rattled off. “That’s as much as I remember. And that will get me as far as I need to go.”

If you want to know more, check out the New Scientist Pi Day Special.