The infinite life of pi (video 3:45) – 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.

**Pi Day** – People generally celebrate March 14 as Pi Day because March 14 is also written as 3/14, which represents the first three numbers 3.14 in the approximation of pi.

A Once-Every-Century Pi Day – Pi Day holds special significance on **3/14/15 at 9:26:53** a.m. and p.m., the date and time represents the **first 10 digits of pi**.

**Do It**

Challenges for you to work on…

- Pi Day activities – hat sizes, links
- Pi activities – more than 50 ideas for ways to make Pi Day entertaining, educational, tasty, and fun.

**Learn more…**