show/hide this revision's text 1 [made Community Wiki]

A biologist, a physicist and a mathematician were all drinking coffee and tea and observing a house across the street from them. They notice that two people walk into the house and then an hour later, three people walk out.

Physicist: An experimental error. Our first measurement was incorrect.

Biologist: No, they've obviously reproduced.

Mathematician: No, now when a one person enters the house, it'll be empty again.

http://www.physicsforums.com/archive/index.php/t-4409.html