Electrodynamics and rational thermodynamics
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Abstract
The electromagnetic fields (D, H) represent contravariant components of an antisymmetric 4‐tensor, while the fields (E, B) represent covariant components of the same 4‐tensor. Both sets are identical in Lorentz frames. The governing equations for them represent equations of balance for the flux of D and the flux B across open surfaces and they are invariant under arbitrary analytic transformation of space and time. This convenient property has motivated mechanicians to reformulate mechanics and thermodynamics in terms of the symmetric 4‐tensor of energy‐momentum so as to exhibit, perhaps, the same invariance as electromagnetism: general relativity. The interpretation of electromagnetism in terms of fields carries the theory a long way. But it breaks down when absorption and emission of radiation by bodies is concerned. In this case the proper view is that of a photon gas.