A number of years ago I became aware of the large number of physics enthusiasts out there who have no venue to learn modern physics and cosmology. Fat advanced textbooks are not suitable to people who have no teacher to ask questions of, and the popular literature does not go deeply enough to satisfy these curious people. So I started a series of courses on modern physics at Stanford University where I am a professor of physics. The courses are specifically aimed at people who know, or once knew, a bit of algebra and calculus, but are more or less beginners.
The Theoretical Minimum is a series of Stanford Continuing Studies courses taught by world renowned physicist Leonard Susskind. These courses collectively teach everything required to gain a basic understanding of each area of modern physics including all of the fundamental mathematics.
The sequence begins with the modern formulations of classical mechanics discovered by Lagrange and Hamilton in the late 18th and 19th centuries, and then moves on to the radical new theories of relativity and quantum mechanics discovered by Albert Einstein and others in the early 20th century. The sequence concludes with a study of modern cosmology including the physics of black holes.