* In physics, a thought experiment is an hypothetical scenario developed to help conceptualize a phenomenon. Maxwell's Demon is a thought experiment exploring the Second Law of Thermodynamics, which states:

The entropy of a closed system will never decrease.

Entropy is a measure of the disorder in energy, and correspondingly of the decrease in usability of energy over time. Energy is never lost, but it can be converted into such a state that it cannot be used to do work. Increased heat is a sign of increased entropy somewhere in the universe.

In the 19th century, when statistical gas laws were beginning to be understood, Scottish physicist James Clerk Maxwell formulated his famous thought experiment:

... if we conceive of a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are as essentially finite as our own, would be able to do what is impossible to us. For we have seen that molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the slower molecules to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics.

The temperature of a gas molecule is directly related to its velocity, so molecules in an isolated box that were sorted from a mixture of all velocities to a "high velocity" chamber and a "low velocity" chamber would result in the high velocity chamber being hotter than the low velocity one - a violation of the Second Law.

The Second Law is a statistical observation, and thus it is theoretically possible that it could be violated, though the probability of such is so low as to make it essentially impossible.

Hence the Probabilator.