Many people are looking forward to St. Patrick’s Day, with it’s green shamrocks, corned beef and pub crawls. But, there’s another day of celebration just a couple of days before that which is worth noting.

Today, March 14 (3/14), is Pi Day. Yep. π Unfortunately, many Arizona schoolkids are out on Spring Break, so they won’t be able to celebrate in class. What a missed opportunity! (Note to district administrators everywhere: Make sure kids are in school on Pi Day from now on.)

So, what the heck is π, anyway?

1. Pi = The Circumference of a circle, divided by the the diameter of the circle.

2. It doesn’t matter what circle you’re talking about, the answer is always the same. It ends up being 3.14 - but that’s the shortened number, only to two decimals. If you do the math, you’ll find that the division problem goes on and on and on. It’s the division problem that never ends. Ever. Kind of a nightmare for math-challenged people, but for geeks, it’s absolutely fascinating!

3. That never ending math problem? It represents an “irrational” number. Seriously. Official definition (from Wikipedia):

An irrational number is a real number that cannot be expressed as a ratio of integers, i.e. as a fraction. Therefore, irrational numbers, when written as decimal numbers, do not terminate, nor do they repeat. For example, the number π starts with 3.14159265358979, but no finite number of digits can represent it exactly and it does not end in a segment that repeats itself infinitely often. The same can be said for any irrational number.

4. So, just how many digits of pi are there? Well, one computer gave up after going eight quadrillion places to the right of the decimal point.

5. The official celebration of Pi Day starts at 1:59 PM. That’s because if you carry out the math, your first few digits will be 3.14159

6. The first known celebration of Pi Day was in 1988, by physicist Larry Shaw at the San Francisco Exploratorium. The staff and public marched around one of its circular spaces and then ate fruit pies. If you can get to the Exploratorium today, they will still be celebrating. Try to make it before 1:59 PM, ok?

*Larry Shaw, the founder of Pi Day. Thanks, Larry. Photo by Ronhip.*

7. Did you know that Albert Einstein was born on Pi Day in Germany? That was before anyone thought to celebrate Pi Day, but hey, it’s an easy way to remember Einstein’s birthday. In case anyone asks you the trivia question, “Which famous scientist was born on Pi Day?” Now you’ll know. In Princeton, New Jersey, they throw an annual Einstein look-alike contest on March 14 while they’re celebrating Pi Day.

8. Just so you don’t think that Pi Day is some secret celebration only for mathematical geniuses, on March 12, 2009, the US Government officially recognized March 14, 2009 as National Pi Day. No worries, it was a non-binding resolution. (So, what’s the point? Who knows? It’s Congress.)

9. How to celebrate? Eat pie. Or throw pies. Or, better yet, have a pizza.

10. If you like celebrating Pi Day, just wait until Square Root day comes along. But, ‘wait’ is the operative word here - there won’t be another Square Root day until May 5, 2025 (5/5/2015) - that’s the next time the day of the month and the month are the square root of the last two digits of the year. (I wonder what you eat on Square Root day?)

11. Remember, just 3 days after today comes St. Patrick’s Day. Then you can wash away all that math geekiness with a nice cold glass of brew.

Raytheon has created this helpful infographic about Pi Day. Hmmm... Maybe it should be required reading for all those students on Spring Break.

*Editor’s Note: Some of the images shown here may be published under the Creative Commons licensing. Images were possibly altered to accommodate the article. http://creativecommons.org/licenses/by-sa/3.0/*