## A Brief History

On March 14, 1988, the earliest known reference to Pi Day was declared by physicist Larry Shaw at the San Francisco Exploratorium (a science museum along the lines of the Ontario Science Center in Toronto or the Great Lakes Science Center in Cleveland). Unlike many of the so called “National” or “International” days of the year listed as dedicated to a particular thing or activity, we at least have some of the origin story for this one.

### Digging Deeper

Celebrating the numerical ratio of “Pi,” a mathematical constant, the relationship between the diameter/radius of a circle and that circle’s area and circumference, using March 14th as the Pi Day is a clever take off on the way the date can be displayed, 3/14, as the first three numbers in Pi are 3.14. The rest of Pi goes on for infinity as it is what is known as an irrational number, one that stretches on with an infinitely repeating numerical sequence, with some efforts reaching over 70,000 places without finding an end!

Mathematically Pi times the diameter of a circle will yield the circumference of that circle, and Pi times the radius squared of a circle will tell you the area of that circle. The discovery of Pi (**π**, a Greek alphabet letter used to represent the numerical ratio) dates back to Archimedes in 250 BC, and can also be approximated by the fraction 22/7, leading some to celebrate Pi Approximation Day on the 22nd of July. Modern mathematicians and scientists have found other applications for the Pi constant.

So how do people celebrate National Pi Day? After all, the US Congress voted to recognize National Pi Day in 2009! Massachusetts Institute of Technology (MIT) usually sends it acceptance letters out on Pi Day, a clever use of the day. Others combine Pi Day with the celebration of Albert Einstein’s birthday. (By the way, do you think Einstein would be irritated that we often refer to idiots as “Einstein?”) Other people use the pronunciation of “Pi” which is the same as “pie” to make the day a celebration about the delicious dessert treat, either eaten, baked, or thrown at other people! Some folks go as far as to bake a pie with the symbol Pi on the top crust.

On March 14, 2015, a special Pi Day occurred when the numbers serendipitously lined up to represent the first 10 numerals in Pi, 3.141592653, as represented by 3/14/15 for the date and 9:26:53 for the time (either am or pm).

How will ** you** celebrate Pi Day? Please tell us your best ideas. I think we will stay with the tried and true gobbling of our favorite pies!

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### Historical Evidence

For more information, please see…

Andrews, George E.; Askey, Richard; Roy, Ranjan. *Special Functions*. Cambridge University Press, 1999.