The Tao of τ

Today is 6/28 in Australia. Happy Tau day.

Tau (τ) is a mathematical constant derived from the proportions of a circle, the ratio of a circle's circumference to its radius, approximately 6.28. This is twice the value of the more famous constant Pi (π), approximately 3.14, or the ratio of a circle's diameter to its circumference.

If you like π you will love Tau because it is two π's. But τ doesn't seem to be as popular as π; nobody seems to be memorizing τ to 1000 places. Yet τ has its uses, especially in the solid geometries used in 3D graphics, where circles are less important than spheres, and if you use π you get knee deep in powers of and divisions and multiplications by two.

Physicist Michael Hartl writes in the Tau Manifesto

For millennia, the circle has been considered the most perfect of shapes, and the circle constant captures the geometry of the circle in a single number. Of course, the traditional choice of circle constant is π—but, as mathematician Bob Palais notes in his delightful article “π Is Wrong!”, π is wrong. It’s time to set things right.

The Tau Manifesto, launched on Tau Day 2010, embraces the Tao of τ by doing away with all those inconvenient powers, multiplicands and divisors of two at the heart of quadratic equations and replace them with twice the number of π's.

The Tau of more Pi sounds good to me. But perhaps that is a bit pious. Or 2π -ous!