# Celebrating Pi Day

Yesterday, March 14, more commonly known as pi day, is celebrated each year by mathematicians and pun lovers around the globe because not only is it the birthday of Albert Einstein, but the date resembles the first three digits of the infamous mathematical number pi when the month and day are numerically written.

Beginning with 3.14 and continuing in an infinite string of numbers, Pi was first calculated in the 200s BC by the early mathematician Archimedes of Syracuse to represent the ratio of a circle’s circumference to its diameter_{2}. Pi was given its name much later than it was discovered in 1647 when William Oughtred and became adopted by the mathematical community even later in 1737 when Leonhard Euler first used the Greek letter p to represent the number_{2}.

Pi, the number, was first linked with March 14 in 1988 when physicist Larry Shaw of San Francisco’s Exploratorium, a learning lab open to the public for exploratory educational opportunities and events, organized a staff event_{1, 2}. Shaw decided to provide the Exploratorium staff pies and tea at exactly 1:59 p.m. in honor of the fourth, fifth, and sixth letters of pi. This event grew into a tradition that was gradually adopted by more and more people until it was declared an official U.S. holiday by Congress in 2009_{2}.

Because pi is an irrational number with infinite digits, many brilliant mathematical minds have become fascinated over the number, its representation, and getting as close as possible to the exact number. According to the test prep company Mometrix’s Pi Day website, ancient civilizations used measurements to estimate the value of pi with the two most notable calculations being 3.125 from the Babylonians who used rope to mark determine their estimated and the Egyptians’ conclusion of 3.163 as numerical representation of pi_{3}.

To determine the value we currently know to be pi, Archimedes used a different approach. Instead of using physical measurements, Archimedes used an algorithm to complete his calculation by drawing a circle with a polygon inside and a second circle on the outside of the polygon_{3}. He then continually drew more sides to the polygons until he was as close as possible to the shape of the circle_{3}. This allowed him to approximate the value of pi by calculating the length of the perimeter of each polygon he drew, the external of which is greater than the circumference of the circle and the internal of which is less than the circle’s circumference_{3, 4}. Through this method, Archimedes determined that pi was between 3.1429 and 3.1408, an extremely close calculation to 3.1416, the number we now know as pi, using a rudimentary algorithm_{3, 4}.

The fascination with pi continues into the modern era with competitions around the globe to find the person who can memorize the most digits of the mythical number. As of 2015, Akira Haraguchi was able to recite 111,700 digits of pi making him the world record holder for most pi digits memorized_{5}. While this is an impressive feat, Haraguchi wasn’t even close to memorizing all known numbers of pi, which is still unable to be calculate in its entirety. In 2019, Google employee Emma Haruka Iwao calculated the most digits of pi ever known—a mind bending 9 trillion digits_{6}.

While for most people and most purposes knowing pi to be 3.14 will suffice, mathematicians will continue to calculate pi to reveal more of its digits and pi fanatics continue to memorize more of those revealed numbers.

Are fascinated with pi? Would you call yourself a pi expert? Prove it by acing a Pi Day quiz!

References

- Exploratorium. (2021). Pi (π) Day - March 14, 2021. Retrieved from https://www.exploratorium.edu/pi#:~:text=Founded%20in%201988%20at%20the,online%20all%20around%20the%20world.
- National Today. National Pi Day – March 14, 2021. Retrieved from https://nationaltoday.com/national-pi-day/.
- Mometrix. (2021). What is Pi?. Retrieved from https://www.piday.org/learn-about-pi/.
- Groleau, R. (2003, September 1). Approximating Pi. Retrieved from https://www.pbs.org/wgbh/nova/physics/approximating-pi.html#:~:text=Archimedes'%20method%20finds%20an%20approximation,is%20greater%20than%20the%20circumference).
- Bellos, A. (2015, March 13). He ate all the pi : Japanese man memorises π to 111,700 digits. Retrieved from https://www.theguardian.com/science/alexs-adventures-in-numberland/2015/mar/13/pi-day-2015-memory-memorisation-world-record-japanese-akira-haraguchi.
- Roeder, O. (2019, March 14). Even After 31 Trillion Digits, We’re Still No Closer To The End Of Pi. Retrieved from https://fivethirtyeight.com/features/even-after-31-trillion-digits-were-still-no-closer-to-the-end-of-pi/.