# Happy Pi Day!

## Let’s have some Pi!

Tuesday is March 14, or what we math fanatics know as Pi Day! Pi Day is an excellent time to talk about math with children, and it is observed annually all over the world for the love of math and what we know as Pi. Pi is a mathematical constant which approximates to 3.14. It is the ratio of a circle’s circumference to its diameter, and Pi is the same for all circles regardless of size. 3.14 is just an approximate value – Pi has, to date, 2.7 trillion digits, and there is even a book containing a lot of its digits! Isn’t this fascinating?

I’m pretty sure that picture is not an illusion!

## History of Pi

If you measure circular objects, it has always turned out that a circle is a little more than 3 times its width around. In the Old Testament of the Bible (1 Kings 7:23), a circular pool is referred to as being 30 cubits around, and 10 cubits across. Archimedes used polygons with many sides to approximate circles, and determined that Pi was approximately 22/7. The symbol “π” was first used in 1706 by William Jones, and became popular to use after it was adopted by Swiss mathematician Leonhard Euler in 1737. Out of its 2.7 trillion digits, only 39 digits past the decimal are needed to accurately calculate the spherical volume of our entire universe.

This year, NASA has a whole series of activities specially dedicated to Pi! There are also two interesting math puzzles related to Pi published by The Guardian. Visit their sites for lots of Pi fun!

Meantime, we end this post with a song that you can sing along!