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Move over Pi... today's Tau Day

From composing songs to eating two pies, the internet on Friday celebrates the circle constant, Tau.


For most, pi is a familiar circle constant compared with tau. (Staff Photo by Gregory Rec/Portland Press Herald via Getty Images)

Portland Press Herald

Help yourself to two pies not one. Math enthusiasts on Friday are celebrating Tau Day, an annual occasion dedicated to the humble circle constant τ, which contrasts with the more well-known π.

While π is the answer you get when you divide a circle's circumference by its diameter, τ results from the circumference divided by its radius. Today's date (6/28), connects to the value of Tau which is approximately 6.28.

Math fans are celebrating all over Twitter. Some even composed their own song:

Tau started to get some attention in 2001 after University of Utah mathematician Bob Palais released an article called "π is wrong!" in the Mathematical Intelligencer, a journal known for its accessible and less technical voice. 

According to a previous blog post by Wolfram, a computational search engine, proponents of Pi argue that Tau helps make subjects such as "geometry and trigonometry" easier for students to learn. The post mentions how since we measure angles in radians, and there are 2π radians in a circle, Tau is the way to go. You can also look at it as, two Pi's are equivalent to one τ. 

Another way to think about it that quite a few math formulas, such as circumference, use 2π. By simply using τ we can eliminate using the two altogether and have shorter, simpler expressions. It would also create less room for simple errors. 

Math experts did not immediately respond to a request for comment.