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.
A mathematician, a physicist, an engineer went again to the races and laid their money down. Commiserating in the bar after the race, the engineer says,
"I don't understand why I lost all my money. I measured all the horses and calculated their strength and mechanical advantage and figured out how fast they could run..."
The physicist interrupted him: "...but you didn't take individual variations into account. I did a statistical analysis of their previous performances and bet on the horses with the highest probability of winning..."
An engineer, a physicist, and a mathematician are trying to set up a fenced-in area for some sheep, but they have a limited amount of building material. The engineer gets up first and makes a square fence with the material, reasoning that it's a pretty good working solution. "No no," says the physicist, "there's a better way." He takes the fence and makes a circular pen, showing how it encompasses the maximum possible space with the given material.