Statistical physics is basically counting. In the words of E. Schrödinger,'There is, essentially,
only one problem in statistical thermodynamics, the distribution of a given amount of energy
E over N identical systems. Or perhaps better, to determine the distribution of an assembly of
N identical systems over the possible states in which the system can find itself, given that the
energy of the assembly is a constant E'. 1 The calculation of the microscopic energy levels
per se is not the problem of statistical mechanics. That problem is of course very important …