For your entertainment, I have compiled some of the finest physics jokes available on today's world wide web:
"This message was written entirely with recycled electrons."
"A student recognizes Einstein in a train and asks: Excuse me, professor, but does New York stop by this train?"
"Gravity is a downer"
"Entropy isn't what it used to be..."
"Two neutrinos go through a bar..."
"A bar walks into a man, oops, wrong frame of reference."
"Heisenberg is out for a drive when he's stopped by a traffic cop. The cop says 'Do you know how fast you were going?' Heisenberg says 'No, but I know where I am.'"
OK, I'm really sorry- these are awful. I'm going to conclude that all the smart Physicists are too busy explaining the world to come up with some decent jokes.