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.

But then records are made to be broken. In 2021, scientists at the University of Applied Sciences of the Grisons calculated another 31.4 trillion digits of the constant, bringing the total up to 62.8 trillion decimal places. Today Google announced yet another record: 100 trillion digits of π. The crunching program (using the Chudnovsky algorithm) ran for 57 days, 23 hours, 31 minutes and 7.651 seconds. Want to see the entire string of decimal places? You can also access the entire sequence of numbers on Google’s demo site. Any guesses what was the 100 trillionth decimal place number? It was 0 (zero).

Why would Google take on such a project… well, it’s like Everest. It was there. But also it was a demonstration of the Google Cloud Services because calculating π is compute-, storage-, and network-intensive. The calculation ran on 128 virtual CPUs with 864 GB of memory all sitting atop a 100 Gbps network… similar to your home computer… well, similar in that they both use electricity and a few other items. Think of them as very distant cousins, once or twice removed.

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.

But maybe 100 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.

As a former Math teacher, thanks for the post. My Math Honor Society at South County High School ran a competition on Pi Day one year to see how many digits the students could remember correctly. The most: 108 digits!! And he told me he actually knew more but flubbed up on the 109th digit.