Michael Hartl

Welcome to Michael Hartl’s home on the Web! I’m a theoretical physicist with a background as a technology entrepreneur. You might know me as the founder of Tau Day and author of The Tau Manifesto, as the creator of the Ruby on Rails Tutorial, or as cofounder and principal author at Learn Enough (acquired 2022). I’m currently working on a math learning project; see my Substack posts and my /now page for more on what I’m up to now.

I’m the author of over a dozen books, including Learn Enough Python to Be Dangerous and the Ruby on Rails Tutorial, published jointly by Learn Enough (online courses) and Pearson Education (print editions, ebooks, and video bundles). Since the acquisition of Learn Enough in 2022 and the completion of my final Learn Enough tutorial, I have been focusing on reconnecting with my physics roots, beginning with a systematic course of study in mathematics. Check out Michael Hartl’s Substack posts and follow @mhartl on 𝕏 for more.

I’m an alumnus of Harvard (A.B. in Physics), Caltech (Ph.D. in Physics), and Y Combinator (with a company that is long, long defunct). As a graduate student and postdoc at Caltech, I studied black hole dynamics and was an instructor in theoretical and computational physics, receiving a Lifetime Achievement Award for Excellence in Teaching. At the request of Kip Thorne, I also served as Caltech’s editor for an update to The Feynman Lectures on Physics. (You can read more about this remarkable project here.)

Other interests include old books, natural and computer languages, nutrition, physical fitness, singing, and martial arts (including MMA, BJJ, and Krav Maga Level 5, a “black belt in self-defense”).