# Ruby and the Tau Manifesto

##### Jun 28, 2010 • posted by Michael Hartl

Many of you are probably aware of "Pi Day", an annual celebration of the number π (pi) that takes place on March 14 (3/14). Some of you may also be aware that there are serious problems with π, which is defined as the ratio of a circle's circumference to its diameter. This definition is in many ways a confusing and unnatural choice for the circle constant. I have just launched a new project called The Tau Manifesto, which argues in favor of the *true* circle constant, the ratio of a circle's circumference to its *radius*, and proposes that we call this number τ (tau). And, since numerically τ is 2π, you might note that today is June 28 (6/28)—that is, today is Tau Day.

The *Tau Manifesto* was written using the same typesetting system (which I call PolyTeXnic) used to write the Ruby on Rails Tutorial book, and PolyTeXnic itself is written in Ruby. I hope the more mathematically inclined Rubyists out there will be interested to read the *Tau Manifesto*, which can be found at tauday.com.

Happy Tau Day!