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2. Anomalously Low Atomic and Molecular Specific Heats. According to the equipartition theorem of classical physics, each degree of freedom of an atomic or molecular system should contribute $$R/2$$ to its molar specific heat capacity, where $$R$$ is the molar ideal gas constant. In fact, only the translational, and some rotational, degrees of freedom seem to contribute. The vibrational degrees of freedom appear to make no contribution at all (except at high temperatures). Incidentally, this fundamental problem with classical physics was known and appreciated by the middle of the nineteenth century. Stories that physicists at the start of the twentieth century thought that classical physics explained everything, and that there was nothing left to discover, are largely apocryphal (see Feynman, Volume I, Chapter 40).