The magic number

Here at Google, we're getting ready to celebrate Pi Day, which culminates tomorrow, March 14 at 1:59pm, a date and time that correspond to the first six digits of pi: 3.14159. (Some people celebrate at 1:59am.) Of course, since pi is a member of a select group of irrational numbers, meaning they can't be expressed as a fraction, there are an infinite number of digits in pi. You can even set a world record for reciting pi from memory if you have the spare brain cells to remember 100,000 or so digits. Odds are, you certainly won't remember the one trillion digits past the decimal point that computers have calculated.

What is pi, anyway? It's a mathematical constant representing the ratio of any circle's circumference to its diameter. It sounds abstract, but there's a real-world example right under your feet: the circumference of the earth equals the diameter of the earth times pi. And pi is all over the place in math, science and engineering. It's even part of Einstein's theory of relativity, which is fitting since March 14 also happens to be Einstein's birthday. Maybe pi's essential place in our world is why every March around Pi Day searches for [pi] spike upwards.

A quick Google search reveals a lot of options for celebrating this "nerd holiday." For starters, you could do some math (now that's an irrational number!). If you're at the Exploratorium in San Francisco, where Pi Day began in 1987, you might be circumnavigating a "Pi Shrine" or singing a Pi Day song. Others suggest watching the movie π or going on a "pi run" (you can stop at 3.14 miles). You can hold your own pi recitation contest, or mix it up and make it tougher by asking people to recite pi in binary (hint: it's a lot of ones and zeros). Finally, don't forget the best part of Pi Day: eating pie! Either make your own, or, if you're too dizzy to bake after circumnavigating Pi Shrines all day, find one to buy nearby. I'll have apple.

Posted by Emily Wood, Google Blog team