A bunch of jokes about the theory of relativity:
A student recognizes Einstein in a train and asks: Excuse me, professor, but does New York stop by this train?
Why did the chicken cross the road? Albert Einstein: Whether the chicken crossed the road or the road crossed the chicken depends on your frame of reference.
Q: How many theoretical physicists specializing in general relativity does it take to change a light bulb?
A: Two. One to hold the bulb and one to rotate the universe.