What irrational number has its own holiday? Pi! Every year on March 14, mathematicians, scientists, engineers, and math students celebrate “Pi Day.” It’s impossible to calculate the exact value of pi. Many people use 3.14 as an estimate. So, each year on 3/14, we celebrate this odd, important, irrational number.

#### A Long History and a Longer Train of Digits

4,000 years ago, the ancient Babylonians noticed that all circles had something in common. If you measured the circumference of a circle and divided it by the circle’s diameter, you always arrived at the same number. The Babylonians didn’t have the math or the measuring tools to get an exact value for this number, but they knew it was approximately equal to 3. We call this number pi. Mathematicians in China, India, Arabia, Egypt, and Europe came up with their own estimates for pi. They thought that pi might be a rational number. They tried to find more exact estimates, hoping to discover its true value.

Eventually, mathematicians proved that pi is irrational. We’ll never be able to find the exact value of pi. However, the more digits we compute, the closer we’ll get. Currently, mathematicians have calculated more than 68 billion digits for pi. With only the first 30 digits, we can accurately measure anything in the universe, but scientists continue on calculating more digits. They hope to find a pattern hidden within pi. So far, it seems to be the most random number on the planet. Pi is unique, even among irrational numbers. And that’s why it gets its own holiday.

See for yourself: http://www.youtube.com/watch?v=fHxY41iDvzs

#### Explore More

Take a moment to watch the following fun, pi-themed videos!

http://www.youtube.com/watch?v=bFNjA9LOPsg

http://www.youtube.com/watch?v=YOQb_mtkEEE

http://www.youtube.com/watch?v=ZNiRzZ66YN0