“Tackling Wired Waves in Heinrich Hertz’s Electromagnetic Experiment: Theory, Materiality, and Exploratory Trial”

Chen-Pang Yeang (University of Toronto)

Heinrich Hertz’s “discovery” of electromagnetic waves in 1887 is one of the most famous historical experiments. In the popular account, key to this experiment was detection of the induced spark intensity’s spatial variation between a spark-gap generator and a metal reflector. This variation not only demonstrated the wavelike feature of the induced sparks, but also helped determine their speed of propagation, which confirmed James Clerk Maxwell’s theory. In this paper, we focus on a trial Hertz undertook right before his reflector-instigated experiment: production of interference between the electromagnetic action in air and that along a metal wire. Hertz first identified the wavelike features of the induced sparks from this “wired-wave” trial. But the experimental result showed different speeds of propagation for the wireless and wired waves. According to the standard narrative, this result was wrong; Hertz quickly moved to the reflector setup; and Édouard Sarasin and Lucien de la Rive in Geneva showed the equivalence of both wave velocities in 1893. We argue that Hertz’s wired-wave experiment warrants a closer historical investigation for three reasons. First, the different speeds of propagation encouraged Hertz to modify, not vindicate, Maxwell’s theory. Second, Hertz’s shift from the wire-based to the reflector-based apparatus was motivated by different material conditions of the two experimental systems. Third, this shift also marked the evolving nature of Hertz’s electromagnetic experiment as an exploratory tool for novel scientific effects. To examine these historical aspects, we will supplement studies of textual sources with hands-on work to replicate Hertz’s wired-wave experiment.

“Some Overlooked Mathematical Issues in the 1905 paper on Special Relativity”

Jon Freeman (Retired from NASA-Glenn Research Center)

There is both uncertainty and confusion concerning the historic development of the special theory of relativity. We analyze the derivation of the Lorentz Transformations given by Einstein in 1905. After sufficient detailed study, we conclude that the derivation is internally inconsistent; therefore, he was aware of the transformations at the time of writing of his remarkable paper. Though the derivation is flawed, it does not affect the concepts he put forth. The observations given here will help resolve a long-standing dispute over the priority of the discovery of various parts of the theory. The priority (which is presently concentrated with Einstein), may need to be slightly redistributed between Einstein, Lorentz, Poincaré, Larmor, Voigt, and perhaps others.

“Einstein and the Michelson-Morley Experiment: The Context of Justification Revisited”

Shannon Abelson (Indiana University, Bloomington)

John Stachel has argued that within the context of justification, Einstein regarded the 1887 Michelson-Morley interferometer experiment as evidence for the special theory of relativity. While I concede that Stachel has offered a strong prima facie case for this reading of Einstein’s position, I think that much more may be said on this matter. I revisit the question of whether Einstein regarded the experiment in this way, making substantial reference both to the structure of the special theory as it is presented in his 1905 paper and to Einstein’s philosophical views and what they reveal about his dispositions toward theory, evidence, and justification throughout his life. I argue that there are three grounds on which one may call into question Stachel’s interpretation: 1) the special theory renders the luminiferous ether superfluous, and thus an experiment that suggests the nonexistence of such a substance is evidentially beside the point; and 2) as Don Howard has argued, Einstein’s hybrid positivist and holist views concerning evidence and justification indicate that he would have considered measurements as evidence only insofar as they bear on the theory as a whole; and 3) as Harvey Brown has shown, the structure of the special theory did not include an explanatory picture of the dynamics underlying rods and clocks, a fact of which Einstein was aware. I argue that it therefore did not fully explain the results of the Michelson-Morley experiment. The picture that emerges from these examinations is considerably more complex than previously thought.