Triumphs of science and math!

A Mathematician, a Biologist and a Physicist are sitting in a street cafe watching walk by the empty house on the other side of the street. First they see two people going into the house. Time passes. After a while they notice three people coming out of the house.

The Physicist says: "The measurement wasn't accurate."

The Biologist concludes: "They have reproduced."

The Mathematician says: "Now if another person enters the house, it'll be empty again!"