March 14 is Pi Day (3.14) and Albert Einstein’s birthday. (And also my mom’s, but that’s another blog post entirely.) Here are my favorite points about π:

It’s Irrational

I’m a poet by training, so I always hope an “irrational number” might be metaphorically more my type than all those “rational” numbers my accountant throws at me. “Irrational,” however, is simply a prosaic description of numbers that cannot be represented as a ratio—you know, the familiar fractions: 3/4, 1/3, 12/30. Pi just doesn’t work that way. It’s a number, but never a ratio. Except it’s a constant drawn from the stable relationship (ratio) between a circle’s diameter and its circumference. So it is a ratio. Just not a rational one.

Pies Depend Upon It

Whether pizza or apple, every delectable dish that ever came out of a battered round tin is an ooey-gooey embodiment of the geometry of a circle—A = nr2, for example. One poet and baker, Kate Lebo, has combined prose poems with recipes to produce TheCommonplace Book of Pie, as well as social/culinary events around pie. And although the reading I went to never got around (ahem) to π, it did make me think about social circles. Even the Pi Chart on our home page couldn’t be built without those two columns holding up a squiggly roof.

Cruise with It

Pi is also used in the math behind the math that is used to engineer self-controlling systems like the cruise control on my car. (Cauchy’s integral leads to Poisson kernels that get applied to control theory problems that are used to build the cruise control.) This is math that is way-way beyond my long-ago, single semester of calculus, but I know people who can talk me down from the ledge. Once down, I can appreciate the coolness. Pi is everywhere.

It’s Transcendental

Apparently, this has very little to do with Henry David Thoreau, so maybe Walden Pond wasn’t round. “Transcendental” is either about the infinite, non-repeating pattern of the number, or the state Pi enthusiasts enter as they memorize more and more digits. As piday.orgsays, “In recent years, Pi has been calculated to over one trillion digits past its decimal. Only 39 digits past the decimal are needed to accurately calculate the spherical volume of our entire universe, but because of Pi’s infinite & patternless nature, it’s a fun challenge to memorize, and to computationally calculate more and more digits.” See? Transcendental fun. Just as Ralph Waldo Emerson wrote inNature, about the “radical correspondence of visible things and human thoughts.” Infinite and patternless, yet going in circles—on cruise control. Meditate on that.

It’s Pi Day this week, even for the poets among us.

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