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# It’s Pi Day! Let’s have some pie. (+video)

## One seemingly simple number – 3.14 – has been essential to geometric calculations involving circles dating back to Archimedes. It’s celebrated this day – 3/14 – as Pi Day with that common circular dessert.

What's so special about Pi Day?

Pi, as anyone who got past 8th grade math remembers, is the ratio of a circle’s circumference to its diameter – typically expressed as the simple decimal 3.14, the fraction 22/7, or the Greek letter π.

So naturally, 3/14 – the 14th of March – is celebrated as “Pi Day.” And since 3.14 is the beginning, not the end of Pi – it can be decimaled on out to infinity – and since the next two numbers are 1 and 5 voila! today’s date 3/14/15 is really special.

So let’s all have some pie!

What? Yes, the merging of Pi and dessert has become tradition – including pie-eating contests where kids end up with faces covered in whipped cream.

As Kelly Dickerson of Business Insider points out, the holiday might be silly, but the number itself is really fascinating.

“The number also shows up in a lot of unexpected places,” Dickerson writes. “It shows up in the measurements of the Great Pyramid of Giza. It shows up in the angular distance between stars. Pi shows up in literally thousands of equations.”

Before we get to dessert (I’m wavering between the caramelized banana cream and the key lime … maybe some of each), let’s move on over to www.piday.org and find out more about π.

Here’s a brief history, according to these folks:

“By measuring circular objects, it has always turned out that a circle is a little more than 3 times its width around. In the Old Testament of the Bible (1 Kings 7:23), a circular pool is referred to as being 30 cubits around, and 10 cubits across. The mathematician Archimedes used polygons with many sides to approximate circles and determined that Pi was approximately 22/7. The symbol (Greek letter “π”) was first used in 1706 by William Jones. A ‘p’ was chosen for ‘perimeter’ of circles, and the use of π became popular after it was adopted by the Swiss mathematician Leonhard Euler in 1737. 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.”

Challenging? Sure. But fun? Maybe….

I’d rather listen to Greg Ristow’s “Fugue on Pi,” which he describes thusly: “I had a spare hour this morning, so I decided to toss off a quick fugue on Pi. If you translate the numbers of Pi to degrees of a scale (I use low 7 for 0, and high 2 for 9), you get a pretty nice fugue tune.”

Geometry students will remember the usefulness of Pi. The area of a circle is found with the formula A = πr2. The volume of a cylinder? V = πr2h.

When it comes to pies and π, imaginations (aided by a calculator) go wild. My colleague Eoin O’Carroll (who has a  Master of Science in journalism and has been a restaurant critic) has punched a bunch of numbers to conclude that the recent heist of an estimated \$85,000 worth of shredded mozzarella in Florida could cover a pizza that is just over 275 feet in diameter – a world record that would fill most of Safeco Field in Seattle.

Something to contemplate as we divvy up the hand-tossed everything-but-anchovies lunch and listen to Amy McConnell’s Pi rap.

I write this, by the way, in honor of Elsie O’Hara Stout, my 8th grade math teacher, who remained vigorous into triple digits. And of my high school math teacher Mr. Hall – whose first name we were not allowed to know, and who always called me “Mr. Knickerbocker.”