## Happy Tau Day

Blogging’s been very light of late, but I couldn’t let June 28th slip by without commemorating Tau Day.

Math aficionados often celebrate March 14 as Pi day, since Pi starts 3.14. All good fun. But as Michael Hartl argues over at the Tau Manifesto, Pi was likely a mistake. If we could rewrite math history, we’d do better to venerate tau, which equals 2 times pi, or about 6.28. So Happy Tau Day!

Hartl marshals multiple arguments in his manifesto. But the best reason is likely the simplest. The two most interesting things about a circle are its radius and its perimeter (aka circumference). If you divide the perimeter by the radius, you get tau. Nice and simple, without that pesky 2 that pops up through math and physics when pi rears its head.