National Pi Day

Today, March 14th, is the annual celebration of the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in the month/day format) since 3, 1, and 4 are the first three significant digits of π. And it is not just because some mathematicians got together and said so, on March 12, 2009, the U.S. House of Representatives passed a non-binding resolution (111 H. Res. 224), recognizing March 14th as National Pi Day. So, its official… in a non-binding kind of way.

The first 10 digits of π  = 3.141592653 .  So one might see why March 14, 2015 at 9:25:53 am was “Super Pi Day.”  How many digits are there in π ? It is one of those infinitely long numbers. A refresher for those of you who have forgotten your elementary school math lessons: 𝜋, is a mathematical constant equal to the ratio of a circle’s circumference to its diameter — 3.141592653….. It is just keep going. How far? In 2019 Google announced that one of its employees, Emma Haruka Iwao, had found nearly 9 trillion new digits of pi, setting a new record. Humans have now calculated the never-ending number to 31,415,926,535,897 (get it?) — about 31.4 trillion — decimal places. It’s a Pi Day miracle!

People have been interested in the number for basically as long we’ve understood math. The ancient Egyptians, according to a document that also happens to be the world’s oldest collection of math puzzles, knew that pi was something like 3.1. A millennium or so later, an estimate of π showed up in the bible: The Old Testament, in 1 Kings, seems to imply that π equals 3: “And he made a molten sea, ten cubits from the one brim to the other: it was round all about … and a line of thirty cubits did compass it round about.”

Archimedes, the greatest mathematician of antiquity, got as far as 3.141 by around 250 B.C. Archimedes approached his calculation of π geometrically, by sandwiching a circle between two straight-edged regular polygons. Measuring polygons was easier than measuring circles, and Archimedes measured π-like ratios as the number of the polygons’ sides increased, until they closely resembled circles.

Google employee Iwao used over 121 days of computing time. The calculation took up about as much storage space as the entire digital database of the Library of Congress. But maybe 31 trillion digits is just a bit of overkill. NASA’s Jet Propulsion Laboratory uses only 15 digits of 𝜋 for its highest-accuracy calculations for interplanetary navigation.

So why do folks keep calculating the length of 𝜋. Probably because they can. As the chess master like to say: “Life is not long enough for chess — but that is the fault of life, not of chess.” π is too long for humankind. But that is the fault of humankind, not of π.

1 thought on “National Pi Day

  1. When i taught middle-school math, this was a big day. A couple of students always brought in pies, and I would bring in ice cream. Happy memories. Now that i’m retired, I totally forgot about the day!

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