When Joe O’Connell was in the third grade, he liked to make things.

His parents bought him materials, a workbench and tools instead of toys. One day, he was measuring all the circles in the house, and noticed a pattern.

“My dad came home and I said, ‘Hey, I figured something out.’”

He had discovered that you could figure out how much you’d need to cover the edge of a circle if you measure across it and multiply by a constant.

“It’s a little more than 3!” he said.

O’Connell, at age 8, had discovered pi — the number you use to calculate the circumference and area of a circle.

Of course, he wasn’t the first.

The infinite number, a little more than 3.14, has been around since the 14th century. It was discovered independently on most continents, and Europeans added the symbol pi in the 18th century.

Most of us simply use it without appreciating its significance, but its aficionados would like to change that.

“Pi is too much fun to be left just to the mathematicians,” said Bruce Bayly, an associate professor of mathematics at the University of Arizona.

And so, every March 14, mathematicians and scientists across the world celebrate Pi Day to interest the public in the number. This year is particularly special because it’s Super Pi Day: The date represents the first digits of pi, 3.1415.

O’Connell still thinks about pi every day.

Today, O’Connell, 47, is the owner of Creative Machines Inc., a company that makes public art and interactive exhibits.

“I use pi a lot, I guess … ” O’Connell said. He’s currently using pi to figure out how much shrink wrap he needs to cover sculptures he makes based on marine organisms.

Bayly, who runs the Arizona Math Road Show and Physics Factory outreach programs, finds pi and circles everywhere.

During a recent interview at Sky Bar on North Fourth Avenue, he went on a riff about why mathematicians have gone crazy looking for a pattern in the number. Then his food arrived.

“Oh my gosh!” he said, delighted. “I’m getting a round calzone on a round tray!”

Bayly had been talking about round objects earlier because he was attempting to explain what makes pi so special, and why it’s so significant that there’s an entire day devoted to celebrating it.

He talked about how we wouldn’t be here if the Earth weren’t round, and how early containers were spherical in design because those containers could hold the most while using the least amount of material to construct them. Then he talked about satellites, before moving onto soap bubbles.

“Not only is the world full of circles,” Bayly said, “but there’s a reason the world is full of circles. And the reason is that they’re great problem-solvers.”

Circles might be related to pi, but the number isn’t limited to round objects.

“Pi is cool because you can give a bazillion answers about where it shows up all over the place,” said DaNel Hogan, director of the STEMAZing Project for the Pima County school superintendent.

Hogan is organizing two pi events for Super Pi Day: one at the Tucson Festival of Books at 9:26 a.m. (the next three digits of pi after 31415) and one downtown at 9:26 p.m.

Over the years, mathematicians have gotten the sense that pi is everywhere.

“We’ve gotten in the habit of kind of looking over our shoulders because the number pi might be lurking there where we least expect it,” Bayly said.

It’s in physics equations, in computer code, even in electricity.

“When you look at the energy of the force between two charges, the equation includes the value of one-quarter times the value of pi,” said Elliott Cheu, the associate dean of science at the UA and a guy who spends his time looking for elemental particles at the biggest particle accelerator in the world.

“So basically, anything you do with electricity, pi kind of shows up in a very fundamental way,” he said in a phone interview.

While the origin of the Pi Day celebration is uncertain, the earliest official celebration of the day was in San Francisco in 1988. Since then, and with the rise of the Internet, the day has taken off.

There are a lot of other numbers in math that could be celebrated, like i, the imaginary number that represents the square root of negative one, and e, the base of the natural logarithm. But, according to Bayly, they don’t have the same panache as pi.

“I does not quite have it,” he said. “E, which is 2.7 and then a bunch of digits, does not quite have it. Mathematicians use e all the time — in fact, even more than pi sometimes. But the number e does not run into our daily lives in the same sort of in-your-face way as pi.”

Pi Day also serves as a way to get regular folks interested in mathematics.

“I think in general, scientific organizations are always looking for ways to promote science and scientific thinking because it’s so important to our society,” said John Pollard, a chemistry professor at the UA.

His special day is Mole Day: Oct. 23. A mole is chemistry’s equivalent to pi. It is a constant that allows a chemist to figure out the number of atoms in a particular substance.

Mole Day originated a few years before Pi Day, but shares the same appreciation for a number, with Mole Day’s being 6.02X1023.

“I think it’s great,” Bayly said about celebrating a number. “I think the math profession could use a little goofiness. And we can take it, because no one’s ever going to look at math and say, ‘That stuff is silly.’ ”

But for O’Connell, Pi Day is deeper than just a goofy celebration of a number — it’s celebrating an achievement that has been made by humanity.

“We’re not going to unlearn pi,” O’Connell said, “even if humanity bombs itself to the Stone Age.”

### Santa Cruz River flows on a triple-digit day

Dan Desrochers is a NASA Space Grant intern at the Arizona Daily Star.