Welcome to Michael Hartl's Home on the Web! You found your way here—you might as well stay a while. I wear several different hats, and if you poke around this site you'll get to know about a few of them.
These days I mainly work as an educator and entrepreneur. I'm the author and presenter of Ruby on Rails Tutorial: Learn Web Development with Rails, which consists of the Ruby on Rails Tutorial book and the Ruby on Rails Tutorial screencasts. The book is available for free online, and both the PDF and the screencasts are available for purchase at railstutorial.org; in addition, the print edition of the Ruby on Rails Tutorial is available at Amazon.com. I am also the founder of Tau Day and author of The Tau Manifesto, which argues that "No, really, pi is wrong." Previously, I taught and studied theoretical physics at Harvard and Caltech.
Incidentally, I have a sister, Dr. Katherine Johnson, who is an ophthalmologist in Fairbanks, Alaska. If you ever need cataract surgery in Fairbanks, she's the one to see. (My sister helps take care of my eyes, and sometimes I help her with search-engine optimization.)