This may be the ultimate geek holiday.

Tomorrow will be 3/14/15 — which just happen to be the first 5 digits of the transcendental number Pi (3.1415). Pi, as we all know from high school geometry class (hope you weren’t snoozing that day) is the ratio of a circle’s circumference to its diameter. It’s an extremely useful mathematical constant for many scientific disciplines.

As one might expect, any excuse for a party. My hometown newspaper, the *Pantagraph*, explains:

It’s 3-14-15 — as any good geek KNOWS, a date that corresponds with 3.1415, the first five digits of the infinite number pi. That calendar coincidence has math fans practically wriggling with glee, not to mention those who just appreciate the whimsy of celebrating a number that sounds like pastry.

You might say that’s irrational. Mathematicians would agree.

And therein lies the delight of Pi Day.

You probably remember pi from grade school, but here’s a quick refresher: Pi is the number that approximates the ratio of a circle’s circumference to its diameter. In other words, if you divide the circumference of any circle by its diameter, you always get pi, an irrational number that starts with 3.1415 and goes on forever. It shares its name with the 16th letter of the Greek alphabet.

The idea of celebrating Pi Day on March 14 — coincidentally, Albert Einstein’s birthday — started in the 1980s. The first large-scale celebration was organized in 1988 at the Exploratorium museum in San Francisco, and Pi Day got a boost two decades later when the U.S. House of Representatives passed a resolution supporting its celebration in 2009.

“It’s mind-blowing to think about a number that’s infinite and non-repeating,” said Dante Centuori, director of creative productions at Cleveland’s Great Lakes Science Center. Add to that the fact that pi sounds like pie, and you have a sweet connection the ancient Greeks couldn’t possibly have dreamed up, Centuori said.

Some just couldn’t wait for the big day. The members of the Undergraduate Mathematics Club at Kent State University celebrated at its biweekly meeting earlier this week with activities that included a talk on the history of pi, a debate on the merits of pi vs. tau (that’s 2 times pi, for you English majors) and a beauty contest comparing the complexity of the various fractions and formulas used to approximate pi.

Club secretary Courtney Augustine said before the meeting that the members would also be guessing the circumference of the pizzas being served.

Who said math can’t be fun?

Math is torture for some of us, but that’s beside the point. Pi is one of those things in science where you feel you are actually glimpsing a small part of creation. Carl Sagan, the late great astronomer, figured that as well and his book *Contact* (not the silly film adaptation) ends with a surprising revelation about Pi. I won’t give any spoilers but if you want to know what I’m referring to, you can find the answer here.

Pi Day is for everyone, not just geeks. Why not celebrate by ordering pizza for dinner tonight, or pancakes, or break out that round of cheddar cheese. The circle is trending today so get in on the fun.