Maxwell's Demon

In the philosophy of thermal and statistical physics, Maxwell's demon is a thought experiment created by the physicist James Clerk Maxwell to "show that the Second Law of Thermodynamics has only a statistical certainty". It demonstrates Maxwell's point by hypothetically describing how to violate the Second Law: a container is divided into two parts by an insulated wall, with a door that can be opened and closed by what came to be called "Maxwell's demon". The demon opens the door to allow only the "hot" molecules of gas to flow through to a favoured side of the chamber, causing that side to gradually heat up while the other side cools down, thus decreasing entropy.