Happy Pi Day of the century!

Every March 14, math enthusiasts around the world celebrate the mathematical constant known as pi, often written simply as 3.14.

Pi describes the ratio of a circle's circumference to its diameter, and it represents an infinite string of numbers. Computers have calculated pi out to 10 trillion digits, but the first 10 go like this: 3.141592653

What makes 3/14/15 so special for pi fans is that it is the only day this century that will have the first five digits of pi -- 3.1415. Since the next digits are 92653, most people have chosen 9:26 p.m. to mark the ultimate pi moment. (Sticklers can wait for the clock to read 53 seconds.)

Humans have been thinking about pi for nearly 4,000 years. The ancient Babylonians figured out that pi's value was roughly 3 as far back as 1900 BC. Ancient Greek mathematician Archimedes determined that pi was slightly bigger than 22/7.

The annual celebration of pi is a much more recent invention, however. Larry Shaw, a physicist at the Exploratorium science museum in San Franciso is credited with creating Pi Day in 1988.

A traditional way to honor Pi Day is to make pie, but we've got some other ideas too.

The education department at

You can also find out where in the string of pi numbers your birthday falls with this nifty Find Your Pi Day website created by the team at

If you prefer to honor Pi Day in the real world, you can head over to the Griffith Observatory, where the cafe will offer pie for sale and program staff will be outfitted in full on Pi regalia. Demonstrations during the day will show how you can calculate pi by dropping sticks on the ground, and there will be a countdown to the pi moment 9:26 p.m.

"We'll have more pi than you can swallow," said Ed Krupp, director of the observatory.

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