Today is Cinco de Mayo. And this year, the fifth of May is filled with mathematical joy. It is — Square Root Day!
It all started in 1981. "I was writing a check in late August," says Ron Gordon, who originated bringing the day to fame. He said to himself, "Wait a minute, in the next couple weeks, it's going to be 9-9-81."
That is, September 9th, 1981. The number of the month (9) multiplied by the day (9) equaled the year — 81. In other words, the square root of 81 is 9.
So Gordon called the day Square Root Day. He drummed up a fair amount of press for it.
"I probably rolled my eyes and thought, 'Oh, here we go!,' " chuckles Linda Gordon, Ron's wife. She draws cartoons for the website that Ron put together where he has a handful of other mathematically themed days he's come up with.
"When it was 11-11-11 with all the ones," recalls Ron, "we called it "Ones Upon a Day." Then, on February 2, 2022, he says, they called it "Trumpet Day because it goes 'To-to-to-toooo.' So for me, each of these, it's just a little math, a little smile, and a little fun."
Ron's daughter, years ago in elementary school, wasn't so sure, however. He says, she said, " 'Dad, if these are really holidays, how come we have to go to school?' "
Out of all his math-themed calendar joy, he says Square Root Day comes along nine times each century, and each one is worth celebrating. And the Gordons do celebrate!
"We will have square steak with root vegetables cut up in cubes," says Linda. She says that Ron will drink root beer and that she'll only sip it. "It's not my favorite, but don't tell anybody."
"It's a good day to get things squared away, to try to fit a square peg into a round hole, go square dancing, root for the underdog, or watch the pigs root around," says Ron.
Today is extra special because the year also happens to be a perfect square. That is, 45 times 45 is 2025.
Square Root Day is a reminder that math is all around us, says Terrence Blackman, chair of the mathematics department at Medgar Evers College in the City University of New York. "It allows us to, in a way, wonder about the world in which we live and the patterns that inform our lives," he explains.
In fact, he says, square roots go beyond interesting math, they matter quite a lot in cybersecurity.
"[The] square root is a very powerful thing," says Blackman. "It helps with encryption, decryption, absolutely. It makes a number of the things that we do in our electronic world work and work efficiently."
Back in 1981, when Ron launched Square Root Day, Ron was a high school science and social studies teacher in Redwood City, California. He's since retired. Today marks the sixth time he's actively championed the day.
"I'm still feeling young," says Ron, "but I'm afraid this is my last mathematical hurrah because I'll be 90 on 6-6-36. I need somebody to really take it over."
So here's to Ron Gordon — the-square-root-of-nine cheers to him.
Copyright 2025 NPR
