What Heinrich Hertz discovered about electric waves in 1887--1888 (Q2659154)

Heinrich Hertz first attempted to justify Maxwell's equations on theoretical grounds, partly by using arguments of his mentor, Hermann von Helmholtz, and, afterwards, he turned his attention to the possibility of verifying them by direct experiments. The present paper is devoted to a specific aspect of the experiments performed by Hertz in 1888--1889 that proved the generation and detection of electromagnetic radiation. Introductorily, the authors state that, though Hertz's first published experiments did provide evidence of such radiation, they did not provide evidence for Maxwell's (or, in the end, Helmholtz's) electrodynamics, for they gave an apparent difference between wire and air speeds. And the authors ask: ``Was there something about Hertz's apparatus, method of observing, or experimental space that, unbeknownst to him, could have produced such a difference?'' (p. 135). To explore the situation it is described in detail, what they undertook to reproduce Hertz's apparatus as far as possible, which measurements they performed by its means in Florence and Toronto and which failure sources could possibly come into consideration. Their account, first, corroborates the fact that Hertz produced evidence for the existence of electromagnetic radiation -- a fact that is accepted by the physical community since 1888 -- and, second, indicates that the apparent difference of wire and air speeds was due to something that ``Hertz did not expect, and certainly could not have calculated even if he had, namely the very structure and content of his experimental space'' (p. 169). The authors argue further ``that these same factors had lesser effects on the results of the reflection experiments in 1888'' (p. 128).