# Happy Tau Day, everybody!

Celebrate June 28, tau converts. Since tau is the ratio of circumference to radius of a circle, it's simpler than pi, say those who are marking today as a math holiday.

There's a celebration for everything these days--National Yo-Yo Day, Ice Cream Day, even Corduroy Day. March 14 was Pi Day--3.14... get it? On Pi Day, which celebrates the number that represents the ratio of circumference to diameter of a circle, enthusiasts had pie-eating contests and played educational games.

(Credit: iStockphoto)

Guess what today is! It's Tau Day. Tau represents the circumference of a circle divided by the radius, which is approximately 6.28. Today is June 28... get it?

Apparently, people have been celebrating this day for 10 years. On Tau Day last year, theoretical physicist Michael Hartl launched the Tau Manifesto, which explained why pi is confusing and instead should be replaced with tau.

One of his reasons: Since tau is the ratio of circumference to radius of a circle, circles are more naturally defined by their radius than diameter. (Are you still following this?)

In Hartl's manifesto, which is dedicated to what he believes to be one of the most important numbers in mathematics, he claims that radians and their factors of 2 are confusing to new learners, and tau makes matters more simple--a half-turn of a circle is naturally a 1/2 tau radians, after all. (Hartl is giving a lecture on his Tau Manifesto today at the California Institute of Technology in Pasadena.)

Kevin Houston, a mathematician from the University of Leeds agrees with Hartl. "It was one of the weirdest things I'd come across, but it makes sense," he told BBC News.

Essentially, the constant tau makes calculations easier; it's the more convenient formulation so we should celebrate it, say Hartl and tau converts (Michael John Blake even wrote a tau song; listen to it in the video below). Hail the almighty tau!

OK, so some of us still don't quite get why tau trumps pi. But today, just go with it. If anything, it sure makes you sound smarter.