# How Pi Day Got Its Pie

For most of its 4,000 year existence, π (also written as pi or 3.14) has had absolutely nothing to do with pie. This shouldn't be surprising given that π is defined as the ratio of a circle's circumference to its diameter, which doesn't sound inherently tasty.

π's earliest documented use appears to have been by Egyptians in 1650 BC, though they were off a few decimals at 3.1605. So were the Babylonians, who seem to have been using 3 or 3.125.

It was Archimedes who finally arrived at a more precise number of 3 and 1/7 (which would generally be rounded to 3.14) in the second century BC. He did so by using the Pythagorean theorem to calculate the areas of a polygon *inside* a respective circle and the one *outside* that circle and then found the ratio of the first area to the second.

Later, the Chinese Zu Chongzi, who was unaware of Archimedes' work, rediscovered π and calculated it as between 3.1415926 and 3.1415927 sometime in the 5th century.

As mathematics continued to advance, conceptions of π advanced with them. For example, in 1760 Johann Heinrich Lambert discovered that π was an irrational number—that is, a number that cannot be fully expressed in a fraction and thus must go on forever.

It was in 1706 that Williams Jones first used the Greek letter π to symbolize this mysterious number, because it was the first letter of the Greek word for circumference—*perimetros*. Mathematician Leonhard Euler popularized the symbol further, and it gradually became the stable signifier it is today.

However, it would be another 2 centuries before π spawned its very own holiday. On March 14th (aka 3/14) 1998, physicist and curator Larry Shaw hosted the first known Pi Day celebration at a San Francisco science museum called the Exploratorium.

This celebration commenced at 1:59 PM, since the next three digits of π's approximation are 159, and it naturally involved the serving of fruit pies. From then on, pi and pie were inextricably linked!

This Pi Day celebration was repeated every year from then on and later grew to include many other festivities, most notably a "Pi Day Parade" that was led by Shaw himself until his death in 2017.

Bolstered by the fact that March 14th also happens to be Albert Einstein's birthday, "Pi Day" spread quickly around the US. It was declared an official national holiday by the US senate in 2009, and is now almost as as big a household name as April Fools or Earth Day!

Pi Day has made its way to many European countries as well, but, because most write their dates day/month rather than month/day, they instead celebrate on 22/7 (July 22nd) after π's fraction approximation.

Unfortunately, Pi Day has not gone unnoticed by many of our ridiculous restaurants, who have made a habit of offering promotions and discounts on both dessert and savory pies for the occasions to ensure maximum profit from our sugar and carbohydrate addictions.Players this year include 7-11, Papa Johns, Diogiorno's, Hungry Howie’s, California Pizza Kitchen, Fresh Market, Whole Foods, Boston Market, and Cheddar’s Scratch Kitchen—and they're just the tip of the iceberg!

So if you plan on reducing your own circumference, we recommend not taking advantage of any of these dastardly "deals." Instead, if you must have pie, check out these two pizza and two pie posts, plus a bonus caramel apple pie recipe here.After all, cooking does involve quite a lot of math—though, admittedly, not a lot of it circumference-focused—so you'd really just be making them in name of science! Or, well, at least pie-ence!

On the other hand, many are of the opinion that Pi Day can actually be celebrated with *any* circular food, which includes a wide variety of super-healthy fruits and vegetables. For instance, oranges, tomatoes, onions, blueberries cabbages, and cucumber slices are all indisputably round, while beans and avocados are at least ovular!

You could also try an entirely non food-related π themed activity, like memorizing a few hundred digits of π, watching the 1998 Darren Aronofsky movie π, dressing like a *pi*rate, or wearing your favorite geeky accessories. Or, of course, you could just treat it like any other day!

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