Thanks For The Pi

"If you wish to make an apple pie from scratch, 

you must first invent the universe." -Carl Sagan

Look! There's a pie on my kitchen shelf.

The circumference of this pie - the distance around the outer edge - is 34.5575 inches, rounded to the nearest ten-thousandth. 

And the area of the top of the crust is about 95.0332 inches square.

Or, should I say, was. 

Approximately half of it has already disappeared. 

This, my friends, is the gift of pi.

Pi is a fantastically useful mathematical constant that relates the radius of any circle to its circumference and its area. 

It comes in handy in other, more advanced uses too, across the spectrum of the maths and the sciences, but this is circle business is pi's stock and trade. 

Commonly rounded to 3.14, pi is actually an endlessly non-repeating decimal number. Irrational, as we say in the trade. Current mathematicians have locked down over 31 trillion digits in that infinite sequence. 

No, you are not required to memorize them. But many have, often up to 70,000 digits. 

Pi was first explored in ancient Egypt and Babylonia; like many other mathematically-minded civilizations who followed, they grasped the concept of pi and came up with fairly accurate approximations of its value. With the invention of calculus and the computer, modern-day math professionals have exploded the number of known digits, and with those newsworthy developments, pi's fame and fortune has flourished. 

For twenty-one delicious years now, I've been introducing novice mathematicians - also known as seventh-graders - to the magic of pi, coaxing them to memorize key formulas, and convincing them that multiplying by 3.14 is not all that bad. Though their mission is not to innovate new uses for pi but to simply replicate our forefathers' calculations, my students always impress me with their willingness to roll up their sleeves and tackle the study of this peculiar little number,

So on March 14, as I bake a pie to share with my family in our annual observance of Pi Day, I am thankful for all the clever minds and curious souls throughout the history of mathematics, laboring over their papers or their computer programs - or even their endless heaps of homework - who make this day something to celebrate. . 

Thanks for the pi!