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 ofTau Day and author ofThe Tau Manifesto, as the creator of theRuby on Rails Tutorial, or as cofounder and principal author atLearn Enough (acquired 2022). I’m currently working on amath learning project; see mySubstack posts and my/now page for more on what I’m up to now.

I’m the author of over a dozen books, includingLearn Enough Python to Be Dangerous and theRuby on Rails Tutorial, published jointly by Learn Enough (online courses) and Pearson Education (print editions, ebooks, and video bundles). Since theacquisition of Learn Enough in 2022 and the completion ofmy final Learn Enough tutorial, I have been focusing on reconnecting with my physics roots, beginning with a systematiccourse of study in mathematics. Check outMichael Hartl’s Substack posts andfollow @mhartl on𝕏 for more.

I’m an alumnus ofHarvard (A.B. in Physics),Caltech (Ph.D. in Physics), andY Combinator (with a company that is long, long defunct). As a graduate student and postdoc at Caltech, I studiedblack hole dynamics and was an instructor in theoretical and computational physics, receiving aLifetime Achievement Award for Excellence in Teaching. At the request ofKip Thorne, I also served as Caltech’s editor for an update toThe Feynman Lectures on Physics. (You can read more about this remarkable projecthere.)

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