The ratio of a circle’s circumference to its diameter is always the same: 3.14159… and on and on (literally!) forever. This irrational number, pi, has an infinite number of digits, so we’ll never figure out its exact value no matter how close we seem to get. Reynaldo Lopes explains pi’s vast applications to the study of music, financial models, and even the density of the universe.

Learn more about π (pi) in The infinite life of pi from TED Ed by Reynaldo Lopes and animated by Igor Coric. Plus:

And if you’re interested in memorizing pi

Piphilology comprises the creation and use of mnemonic techniques to remember a span of digits of the mathematical constant π. The word is a play on the word “pi” itself and of the linguistic field of philology.

There are many ways to memorize π, including the use of piems (a portmanteau, formed by combining pi and poem), which are poems that represent π in a way such that the length of each word (in letters) represents a digit.

The record for memorizing digits of π, certified by Guinness World Records, is 70,000 digits, recited in India by Rajveer Meena in 9 hours and 27 minutes on 21 March 2015. In 2006, Akira Haraguchi, a retired Japanese engineer, claimed to have recited 100,000 decimal places, but the claim was not verified by Guinness World Records…

Try starting with the first 50 decimal digits: 3.14159 26535 89793 23846 26433 83279 50288 41971 69399 37510… or check out One Million Digits of Pi.

Next: Calculating Pi (π) with Darts.

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