Text: A photon rest mass and the propagation of longitudinal electric waves in interstellar and intergalactic space." Non-zero photon rest mass, propagation of longitudinal electric waves in a plasma. Proca equations and two types of longitudinal waves. Longitudinal electric waves can propagate if their mass is non-zero. Important observation of core importance in scalar electromagnetics. Journal of Physics. A. Mathematical, Nuclear, and General. 6(3), Mar. 1973. p. 434-444.

See Also: Photons, longitudinal waves, plasmas, Proca equations, Maxwell's equations, electromagnetic theory.

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