Pi Day

Pi Day

Introduction What's your favorite kind of pie? Apple? Pumpkin? Lemon cream? If you're a mathematician or someone who uses math in your work, it might be something very different. Pi sounds just like pie, but it's the name of a special number that allows people around the world to do many interesting things.

What Is Pi? The idea of pi was discovered more than two thousand years ago by a Greek mathematician named Archimedes (ark-uh- MEE-deez). He was experimenting with shapes and discovered something strange. He measured the length around a circle, called the circumference. Then he measured the distance across the circle from one side to the other through the middle, called the diameter. When he divided the circumference by the diameter, he got the same number every time. It didn't matter what size the circle was.

In 1706, a math teacher in England named William Jones was the first to call this special number pi. It is the name of the Greek letter π. Now all mathematicians and teachers use that symbol when they talk about pi.

The value of pi is often given as 3. 14 (three point one four), but that is just an approximate value. The numbers to the right of the decimal point actually go on forever. No matter how you calculate it, there are more digits to find. In fact, computers have calculated pi to at least eight quadrillion digits to the right of the decimal point. If you tried to write down all those numbers of pi, you'd use enough paper to go around Earth over a million times! There would still be no end in sight!

What can we do with the number pi? It comes from the shape of a circle and has lots of uses. One use is to figure out the area of a circle. Area is the amount of space inside something that is flat. Landscapers use pi to figure out how much area a lawn sprinkler can cover. That amount tells them how many sprinklers they need in order to water a lawn evenly.