Michael Hartl is an American physicist, author, and entrepreneur.[1][2] He is best known as the creator of the Ruby on Rails Tutorial,[3][4][5] founder of Tau Day,[1][6][7][8] and author of The Tau Manifesto.[1][9][10] In The Tau Manifesto, Hartl proposes replacing
pi (π) with
tau (2π).[7][11]
Education
In the 1990s, Hartl attended
Harvard University for his undergraduate studies, graduating with a bachelor's degree in physics.[12] Hartl obtained his
PhD from the
California Institute of Technology (Caltech) in 2003, where he researched
black hole dynamics. His dissertation was titled Dynamics of Spinning Compact Binaries in General Relativity.[13]
Career
After finishing his PhD, Hartl served as Caltech's editor on a corrected and expanded version of The Feynman Lectures on Physics at the request of
Kip Thorne.[14][15] Explaining in the preface why he chose Hartl for the task, Thorne noted that "Hartl understand physics deeply, he is among the most meticulous physicists I have known, and like
Feynman he is an outstanding pedagogue."[14][15] Thorne also noted that Hartl is the only Caltech graduate student to be granted a "lifetime achievement award for excellence in teaching" by Caltech's undergraduates.[14][15][16]
As an entrepreneur, Hartl participated in the
Y Combinator program in 2008.[17] In 2010, he published the first edition of the Ruby on Rails Tutorial book[18][19] and screencasts[20], which teach
web development using the
Ruby on Rails web application framework. The Ruby on Rails Tutorial quickly became both a critical and commercial success,[3][21] eventually going through seven editions.[22] In 2011, Hartl received a Ruby Hero Award for his service to the
Ruby community, with the citation mentioning both the Ruby on Rails Tutorial and his first book, RailsSpace.[23][24] In 2013, Wikipedia co-founder
Jimmy Wales described the Ruby on Rails Tutorial as his "favorite book."[25]
Hartl later co-founded the online education company Learn Enough to expand on the Ruby on Rails Tutorial, adding tutorials on other computer technologies and including online courses.[26][27][28] In partnership with
Pearson Education, Hartl authored or co-authored five books published under the brand Learn Enough to Be Dangerous.[29][30][31][32][33] Learn Enough was acquired by a tech private equity group in 2022.[34]
The Tau Manifesto
In 2010, Hartl published The Tau Manifesto, in which he proposed using the Greek letter
tau to represent the circle constant τ = C/r = 2π,[35] the first time tau was publicly proposed for this purpose.[1][6]The Tau Manifesto proved popular,[36] and a revised edition was published in 2019,[37] followed by a print edition in 2021.[38][39] With the initial publication of The Tau Manifesto in 2010, Hartl also founded Tau Day as a mathematical celebration and to promote adoption of the new constant.[8] Observed annually on
June 28, or 6/28 (in analogy with the celebration of
Pi Day on 3/14),[6][8] Tau Day has become a widely celebrated mathematical holiday.[1][6][40][41] Hartl's constant has also seen significant adoption, including support for tau in the official Google calculator[42] and inclusion in programming languages such as Microsoft.NET,[43] Java,[44] and Python.[45][46]
Hartl, Michael (2022). Ruby on Rails Tutorial. Boston Columbus New York San Francisco Amsterdam Cape Town Dubai London Madrid Milan Munich Paris Montreal Toronto Delhi Mexico City Sao Paulo Sydney Hong Kong Seoul Sinapore Taipei Tokyo: Addison-Wesley Professional Ruby Series.
ISBN978-0-13-804984-3.
Hartl, Michael (2022). Learn Enough Developer Tools to Be Dangerous. Addison-Wesley Professional.
ISBN978-0-13-784345-9.
Hartl, Michael (2022). Learn Enough JavaScript to Be Dangerous. Addison-Wesley Professional.
ISBN978-0-13-784374-9.
Hartl, Michael (2023). Learn Enough Python to Be Dangerous. Boston: Addison-Wesley Professional.
ISBN978-0-13-805095-5.
^Hartl, Michael (2022). Learn Enough Developer Tools to Be Dangerous: Command Line, Text Editor, and Git Version Control Essentials.
ISBN978-0-13-784345-9.
^Hartl, Michael (2022). Learn Enough JavaScript to Be Dangerous: Write Programs, Publish Packages, and Develop Interactive Websites with JavaScript.
ISBN978-0-13-784374-9.
^Hartl, Michael (2022). Learn Enough Ruby to Be Dangerous: Write Programs, Publish Gems, and Develop Sinatra Web Apps with Ruby.
ISBN978-0-13-784413-5.
^Donahoe, Lee; Hartl, Michael (2022). Learn Enough HTML, CSS and Layout to Be Dangerous: An Introduction to Modern Website Creation and Templating Systems.
ISBN978-0-13-784310-7.
^Hartl, Michael (2023). Learn Enough Python to Be Dangerous: Software Development, Flask Web Apps, and Beginning Data Science with Python.
ISBN978-0-13-805095-5.