Today is a special day for math geeks. For one thing, they can get $3.14 off the final bill for a pizza in South Tampa. But really, it's the calendar.
March 14 is also known as Pi Day because 3.14 represents the first three digits of pi, our favorite irrational number. It's also Albert Einstein's birthday, so geeks have heartily embraced the squiggly Greek letter's special day.
It's one of the few mathematical principles to show up in pop culture and on T-shirts. It's well-known enough that it's in The Simpsons episode "Bye Bye Nerdie." Bumbling professor Frink tries to get a rowdy crowd of scientists at Springfield's 12th Annual Big Science Thing to quiet down, shocking the room into silence by yelling, "Pi is exactly three!"
If anyone asks, here's the short answer for what pi really is: No matter how big or small a circle is, if you calculate the distance around it, divided by the distance across it, you will get pi, or 3.14159 — and trillions more decimal places after that. Computers have yet to find an end to it.
In the Tampa Bay area, some Anthony's Coal Fired Pizza locations will celebrate by baking pizzas in the shape of a pi symbol, said company spokeswoman Sasha Blaney.
And Your Pie, the fast-casual pizza place at 2217 S Dale Mabry Highway in Tampa, is taking $3.14 off your bill today on any pizza you order. Pizzas start at $7.49.
Pi is used in math, physics, engineering and the space program. Some schools, including the Massachusetts Institute of Technology, also embrace the day. MIT prospects find out on Pi Day whether they've been accepted by logging onto the admissions website at 6:28 p.m. This time represents another pi reference, 6.28, or "tau" (two times pi).
Retired University of South Florida engineering professor Arthur David Snider said he is sometimes asked if there any practical reasons to compute pi to so many decimals.
"In a way, yes," he said.
About 15 years ago one of USF's electrical engineering professors was trying to simulate microwave radiation on a computer, using a technique called the Finite Difference Time Domain algorithm.
"The results were absurdly wrong," he said. "The problem was that a computer needs pi for these calculations. The standard software at that time used the value 3.14159265, and the answers were way off."
It took a 16-digit value to get the correct answer, he said.
"But if some futuristic engineer tried to simulate light waves, a 19-digit value would be required for sensible answers. And for gamma rays, the computer needs to use 3.1415926535897932384626433832."
Contact Sharon Kennedy Wynne at email@example.com. Follow @SharonKWn.