Maxwell recognizes that the equations foresee that Faraday’s lines can also vibrate at much lower frequencies, that is to say, more slowly than light. Therefore, there must be other waves which nobody had yet seen, produced by the movement of electrical charges, which in turn move electrical charges. It must be possible to shake an electric charge here, and to produce a wave which will drive an electric current there. Only a few years later, these waves, anticipated theoretically by Maxwell, will be revealed by the German physicist Heinrich Hertz; and just a few years later still, Guglielmo
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