LEARN ENOUGH

# 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!

##### Michael Hartl

I’m Michael Hartl—author, educator, and entrepreneur. I’m probably best known as the creator of the Ruby on Rails Tutorial, a book and screencast series that together constitute one of the leading introductions to web development. Once called his “favorite book” by Wikipedia founder Jimmy Wales, the Ruby on Rails Tutorial currently has over 150 5-star reviews at Amazon. I’m also (in)famous for creating Tau Day and The Tau Manifesto, which have inspired an international movement dedicated to the proposition that “pi is wrong.” (For example, as a result of The Tau Manifesto, MIT releases their admissions decisions each year at “Tau Time” (6:28 p.m.), and typing tau/2 at Google yields 3.14159…) Finally, I’m a founder of Softcover, a publishing system and sales platform for technical authors, which among other things powers both The Tau Manifesto and the Ruby on Rails Tutorial.

I’m a graduate of Harvard College and have a Ph.D. in Physics from Caltech, where I studied black hole dynamics and was an award-winning instructor in theoretical and computational physics. I’m also an alumnus of Y Combinator, the entrepreneur program that has produced companies such as Dropbox and Airbnb. (Alas, my own Y Combinator startup was neither Dropbox nor Airbnb.)