Today is Pi Day.
Apple? Blueberry? or Chocolate?
No, not that kind of pie – it’s Pi Day – a day for a little fun with math. Pi is some math dude’s shorthand for writing today’s date: 3-14, which is also the number used in math class for the shortest version of Pi or 3.14 – the number used to calculate the circumference of a circle. The name comes from a letter in some ancient alphabet, but don’t ask me ‘why’, it’s all Greek to me.
The thing about Pi is that anyone can figure out Pi for any perfectly round circle whether the size of the period at the end of this sentence or the earth’s equator (although what with mountains and ocean waves the equator is probably not a perfect circle.)
But, since the period is too small and the equator is too big, let’s use real pie. Real pies are always round. Measure the distance around the outside edge of the pie (The pie, not the pan.) Write it down. On Pi day we don’t call it the crust, we call it the circumference.
Now cut across the center of the pie. And, make sure you cut it exactly through the middle – you know how the kids fuss about getting their fair share of the pie. After you half the pie, measure the length of the straight side on one half of the pie – that’s the diameter. Write down the measurement you get. Look at the two numbers.
The cool thing is this: no matter what size the pie is: a small individual pie or large, 10-inch pie – whatever the size of the pie – the length of the circle (the circumference of the crust) will be a bit more than three times the measured length of the diameter, (that cut we made across the middle of that pie).
You can do the same thing with a big, round barrel, a bean pole, a dime or any circular object. Find the measure of the outside circle and then the length of the diameter from one side of the circle straight through the exact middle of that barrel, bean pole or dime.
The circle will always be a bit more than three times the length across its middle.
So on this official day for celebrating Pi, let’s do a little bit of math. Let’s divide the circumference by the diameter. The fastest way is to pull out your calculator and key in the length of the circle (the circumference or crust), hit the divide key (sometimes it looks like a slanty line, sometimes it is a line with two dots – one on top and one the bottom, sometimes it looks like a backwards C with a line off the top to the right) and then key in the length of that circle’s diameter and hit equal. If you did a really great job of measuring, the calculator will respond that the answer is 3.14, followed by a whole bunch of other numbers.
Somebody with a lot of time on their hands, or access to a tireless computer, has actually figured out the numbers that follow 3.14 to the millionth digit. On Pi Day 2004, Daniel Tammett quoted, from memory, the first 22,514 digits of Pi in five hours and nine minutes.
Youtube has a 90-second video of a girl quoting the first 500 digits in 90 seconds. She said she knows over 2,000 digits. Her dad said she now attends college on a National Merit Scholarship.
But, regular folks, the kind that eat apple pie and lemon meringue pie, don’t need all those other digits to Pi. All those extra digits are for the kind of people who eat zucchini pie, chess pie or maybe even Kool-Aid pie. For the rest of us … happy Pi Day, go have some fun with numbers.
(Joan Hershberger, who prefers apple or lemon pie, is a reporter at the News-Times. E-mail her at
Find the Pi of the pie on Pi Day
Today is Pi Day.