Ask professors about important physics lectures, and they'll probably point you toward Richard Feynman's famous 1964 talks. They led to one of the most popular physics books ever (over 1.5 million English copies sold) and helped generations understand concepts like quantum mechanics. They've been available to the public for a few years now, but there hasn't been an easy, legal way to read them online... until now, that is. The California Institute of Technology has finished publishing Feynman's lectures in a free, HTML5-based viewer that lets you read on any device with a modern web browser. Even the equations and diagrams are visible on small screens. You're sadly not allowed to grab offline copies, but these web versions may be perfect for brushing up on the fundamentals of energy and matter before a big test -- even if you have to study on your smartphone.
[Image credit: Associated Press]