This isn't exactly a programming joke but considering how many of us physics majors become programmers, I think it works:

Heisenberg, Shrodinger and Ohm were driving down a highway when they get pulled over by a cop. The cop asks Heisenberg if he knew how fast he was going, as you can surmise, he claimed he didn't know because he knew exactly where they were. The cop, finding this suspicious (and because this is not USA and 4th amendment does not apply) decides to search the car. He comes back to the front and asks them why they have a dead cat in the trunk, Shrodinger responds, "because you opened the trunk you fool!!". The cop is now irritated and promptly moves to arrest all three. Ohm, resisted.