What Tom said. If physics programming or graphics programming are things you're interested in, definitely learn about them! Build a great portfolio that shows off your physics or graphics programming skills. It will help you a lot when you apply for jobs. But don't bother teaching yourself anything you're not excited about learning. If you don't enjoy learning it, you probably won't enjoy doing it in any of the jobs you would get with those skills.
Programmer at Irrational Games