Although I cannot find the related Q/A, I remember that someone here notified me that the so-called Einstein's light clock was first introduced by Max von Laue or someone but Einstein. Does anybody have any precise information/reference regarding this matter?

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    $\begingroup$ Richard Schlegel, 1980, The light clock: Error and implications,Foundations of Physics vol. 10, pages345–351(1980). On first page mentions Laue and priority, $\endgroup$ – sand1 Nov 25 '20 at 16:55
  • $\begingroup$ @sand1 Thank you so much. Therefore, the light clock priorly belongs to Laue. $\endgroup$ – Mohammad Javanshiry Nov 25 '20 at 17:06

The earliest presentation of this idea that I know of was by Lewis and Tolman in 1909:

Proceedings of the American Academy of Arts and Sciences, 1909, 44: 709–726 https://en.wikisource.org/wiki/The_Principle_of_Relativity,_and_Non-Newtonian_Mechanics

Another early presentation of this concept seems to have been by von Laue in 1917:

von Laue, M. (1917). Jahrbuch der Radioaktivitat und Elektronik, 14,263.

online: https://babel.hathitrust.org/cgi/pt?id=mdp.39015075057870&view=1up&seq=309

I don't read German, and the paper is long, but it actually appears to be about Nordström's theory of gravitation. On p. 293, section 4a is titled "Der Gang der Lichtuhr," which google translate says means "the course of the light clock."

The following 1976 paper by Alex Harvey states that "the use of a shuttling light signal as a timekeeper was introduced by von Laue," giving the reference above.

Harvey, A. (1976). Photon clocks. General Relativity and Gravitation, 7(11), 891–893. doi:10.1007/bf00771021

Either Harvey didn't know about the earlier presentation by Lewis, or he only intended to talk about presentations in the context of gravity.

Von Laue used mirrors attached to the ends of a rigid rod, while a later presentation by Marzke and Wheeler used mirrors moving along geodesics. Harvey criticizes both as having "serious conceptual difficulties," and estimates the rate at which the clock drifts due to recoil from the reflections of the light.


It would be odd that Laue would have thought up the light clock rather than Einstein as this relied upon his physical insight into the nature of gravity - the equivalence principle.

I'd also say that the idea is not 'owned' by Einstein - got ideas are free; but that it is credited to him.


@Ben Crowell: I said it seems 'odd' not that it's impossible. Hence, seeing that you're a man for logic, this is not a contradiction ... as it is, I was actually thinking not of the light clock but light travelling in an elevator - hence the reference to the equivalence principle. As that's the famous thought experiment showing that light travels in a curved trajectory in the presence of gravity.

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    $\begingroup$ This seems to be contradicted by the references discussed in comments. $\endgroup$ – Ben Crowell Nov 25 '20 at 17:22

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