'An electron and a positron walked into a bar…' Scientists tell us their favourite jokes [View all]

Heisenberg and Schrödinger are out for a drive when they get stopped by the police. The policeman asks Heisenberg "Sir, do you know how fast you were going?" and Heisenberg says "No, but I know where I am!". Confused, the officer says "Sir, you were doing 80 mph", and Heisenberg throws his hands in the air and huffs "Great, now I don't know where I am anymore!".
The policeman thinks something is going on, and orders the pair out of the car so that he can search it for contraband. He looks under the seats, in the glove compartment, in the back, and then walks around the car and opens the boot. He stares into it for a moment, turns to Schrödinger and says "Sir, did you know there's a dead cat in here?!", so Schrödinger rolls his eyes and snorts "Yeah, we do now!".

http://www.theguardian.com/science/2013/dec/29/scientists-favourite-jokes