“The Second Law of Thermodynamics is a consequence of a theorem which can be proven in the standard model of physics: If you take a volume of phase space, and develop it forward in time using standard physics, the total volume of the phase space is conserved. For example, let there be two systems, X and Y, where X has 8 possible states, Y has 4 possible states, and the joint system (X,Y) has 32 possible states. The development of the joint system over time can be described as a rule that maps initial points onto future points. For example, the system could start out in X7Y2, then develop (under some set of physical laws) into the state X3Y3 a minute later. Which is to say: if X started in state X7, and Y started in state Y2, and we watched it for 1 minute, we would see X go to X3 and Y go to Y3. Such are the laws of physics.” (Eliezer Yudkowsky, Rationality)