What is it about this one irrational number that makes tech geeks go nuts? Every year on Pi Day – that’s today, March 14 (you know, 3.14) – there are Pi parties, Pi recitation contests and, of course, pie for Pi.

The whole thing really goes nuts on March 14 at 1:59 a.m. and p.m. local time – because, after all, Pi is 3.14159… The festivities – particularly the big mama of them all at the San Francisco Exploratium museum going on today – would make Archimedes proud. The ancient Greek mathematician gets credit for popularizing the mathematical constant, of which references can be found as early as biblical times. And Albert Einstein, born March 14, would be psyched, too. He couldn’t have calculated gravitational field theories without Pi, now could he?

Check out the infographic below for a ton of facts about pi – the only error I found in it is the fact that Archimedes was its publicist, not its identifier. Pi is far, far older than even that ancient Greek. (And don’t stop there, more Pi stuff below…)

Can’t get enough? Try these Pi facts size on for size. There are Pi clubs around the world – including Japan – where people competitively recite as many digits of Pi as they can. I actually saw a guy named Koroyuki Gotu recite Pi from memory on stage at the NHK Broadcasting Center in Tokyo. It was at once fascinating and boring. In 112 hours, he recited Pi accurately to 42,195 places.

Did you know you can use Pi to calculate everything from the circle the size of the universe to the height of an elephant to your hat size?

## Hats, Elephants And The Entire Universe

For the hat size, measure the circumferance of your head and divide the result by Pi and round it off to an eighth of an inch.

To figure out how tall a particular elephant is, just measure the diameter of its foot and multiply the result by two. Then multiply that result by Pi.

As for the universe, a mathematician I interviewed years ago told me it was possible to calculate a circle the size of the entire known universe down to a proton. And supposedly you’d need only the first 39 digits of Pi to do it. You can’t make this stuff up.

There are also plenty of conspiracy theories surrounding Pi. With a number infinitely long, geeks are always looking for their own social security numbers, password ideas and repetitive structures that might suggest something strange is going on with this crazy constant. Some readers will be relieved to learn that Satan — if indeed the signature for the demon is 666 — doesn’t make an appearance until position 2240.

The most interesting thing to note about Pi is its amazing flexibility. Pi is employed in harmonic motion theory, superstring equations and, as mentioned above, Einstein’s gravitational theory.

## Pi Videos

As promised, here are a two videos that are perfect for celebrating Pi. The first shows Pi as it would sound to music. The second is an explainer of Einstein’s relativity theory and its real-llfe applications. It is, after all, not just Pi Day. It’s Einstein Day, too.

The sound of Pi:

Here’s Einstein and the theory of relativity explained, excellently, by the fine folks at The Science Channel.

Happy Pi Day. And Happy Birthday, Dr. Einstein. Wish you were here.

*Lead image courtesy of Shutterstock.*