By Megan Driscoll
What comes to mind when you think about pie (besides yum, of course)? A circle! That should make it easy to remember the significance of pi, a Greek number that defines the ratio of any circle's circumference to its diameter.
The numerically challenged may want to think back to high school math class. Remember 2πr? That's the formula for the circumference of a circle, where 'r' is the radius of the circle (also known as half the diameter) and π is pi, or 3.14159265....
Wait: That's the formula for the circumference of any circle? Yup - the relationship between the diameter and circumference of a circle is a constant, no matter how big or small the circle may be. And that's the magic of pi.
Pi Day 2011
Math lovers around the world celebrate this special number every year on March 14. This day is designated 'Pi Day' because it can be numerically represented as 3.14, a common abbreviation for pi.
And why is pi abbreviated? Because it's an irrational number, which means that it can't be represented as a fraction where the numerator and denominator are integers. This, in turn, means that pi's decimal representation never ends and never repeats.
Since pi is irrational, Pi Day can get pretty silly. Here are some ways to celebrate the day:
Pi lovers pride themselves on memorizing as many digits past the decimal as they can. Try taking some time today to see how far you can get. The official Guinness World Record for number of pi digits memorized is held by Lu Chao, who recited to the 67,890th decimal place of pi without error in 24 hours and 4 minutes.
Bake a Pie
Today is an excellent day for your love of numbers, pastries and puns to unite. Whip up a perfectly circular pie for some edible math fun - bonus points if you can get the pi symbol (π) into the crust. Don't like fruit pies? Try a pizza pie instead. Meat eaters might consider topping it with circular pepperoni.
March in Circles
The first official Pi Day was celebrated at the San Francisco Exploratorium, when staff led visitors in a march around its circular spaces. Find a large public circle and get your own Pi Day march started with friends, fellow students or hapless passers-by. Consider bringing circular instruments like a tambourine for some more noisy celebrating.
Make a Hat
Did you know that you can use pi to calculate your hat size? Since hat sizes must be related to the circumference of the wearer's head, you can calculate your size by dividing the circumference of your head by pi. Don't feel like walking around with a paper circle on top of your head? Find people wearing hats and try guessing the size by measuring their heads (no peeking at tags).
Draw a Circle
Drawing a perfect circle is hard. Think you've got the skills? Challenge your friends to a freehand circle drawing contest. Winner gets a pie!
Throw a Pi Party
Do you love any excuse to throw a party? Combine all of the activities above in one big pi-fest. You can serve circular foods, start a samba circle, wear round hats (or polka-dotted clothing) and host a circle drawing contest. This is a great way for educators to get their students excited about math, or for older students to host fundraisers for number-related organizations. Who could pass up buying a pie on Pi Day?
Love numbers? Check out these careers for the mathematically inclined.