2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/34361Recent observations of the fine structure of spectral lines in the early universe have been interpreted as a variation of the fine structure constant. From the assumed validity of Maxwell equations in general relativity and well known experimental facts, it is proved that $e$ and $\hbar$ are absolute constants. On the other hand, the speed of light need not be constant.3 pages revtex, comments welcomeGeneral Relativity and Quantum CosmologyHigh Energy Physics - TheoryQuantum Physicstext