Statistical mechanics is the study of large groups of particles in equilibrium. While the individual behavior of each particle can be described with classical or quantum mechanics, this becomes unfeasible with large numbers of particles. Statistical mechanics deals with observable behaviors that can be deduced from the nature of the different particles by using probability. It is the link from the world of single photons and electrons to the world of our everyday lives.

Some elements of statistical mechanics are useful for any type of system. The concept of equipartition of energy states that for each degree of freedom, the system will have energy proportional to 1/2kT, where k is Boltzmanns' constant and T is the temperature. That is, for each way in which the system can be changed in position or momentum, the energy will increase according to the above rule. The equipartition of energy...