I watched The Elegant Universe (on an episode of NOVA) on PBS the other night. The show gives a quick run through of gravity, electromagnetism, strong nuclear force and weak nuclear force and the conflict involved in trying to come up with the grand unification theory. The focus then turns to string theory as a possible explanation for how everything works. You can watch the show online.
I’m not a theoretical physicist, but I remember enough from physics classes to make this fun to watch. I didn’t realize how involved Einstein was with developing the theory of space time. He was apparently quite driven to come up with a grand unification theory, but it never happened. Just like in everything else there have been trends in what is and isn’t popular to research in scientific circles.
Looking around the NOVA site, there will be an episode about Einstein’s most famous equation in October.