Current statistical mechanics explains why the equipartition of energy principle is false. This law states that in a system of thermal equilibrium, an equal amount of energy is associated with each independent energy state. Using the equipartition of energy principle, scientists of the late 1800s calculated specific heats of polyatomic gases. However, these calculated values of specific heat did not correspond to the values obtained from experiments. The equipartition of energy principle failed because it used the classical mechanical expression for the molecular energy, but molecular vibrations and rotations obey quantum mechanics, not classical mechanics. After the formulation of quantum mechanics in the early part of the 1900s, the necessary modifications in statistical mechanics were easily made and the correct calculated values of specific heat were determined.

Statistical mechanics, the link between quantum mechanics and thermodynamics, provides a method of...