It's so interesting. This isn't the only paper written about this, because I actually came across this same idea last month in a much older paper. Here's an extract from it:
> It might have been thought, by some scientists in the 1890's, that refined mathematical analysis of this kind would play a role in resolving the fundamental problems of classical physics associated with the apparent failures of the equipartition theorem. But that is not what happened.
> Although the quantum hypothesis did dispose of the paradox of specific heats of polyatomic gases, and eliminated the possibility that ether-vibrations (having an infinite number of degrees of freedom) would drain an indefinite amount of energy out of material systems at any finite temperature, these were not the anomalies that provoked the introduction of the quantum hypothesis in the first place. Max Planck was not one of the physicists who worried about the validity of the equipartition theorem before 1900, and the myth that his distribution law for blackbody radiation was concocted merely to escape from an "ultraviolet catastrophe" predicted by the Rayleigh-Jeans law has now been thoroughly demolished. It was Paul Ehrenfest who invented the ultraviolet catastrophe (eleven years after the publication of Rayleigh's and Planck's papers in 1900) in order to dramatize what would have been the consequences of the equipartition theorem if it had been valid for all classical dynamical systems (though neither Rayleigh nor Planck believed that it was).
I have this saved as a note, but can't find the exact source atm. Here's another source though, from the 60s:
I would be very interested to read this. I found one comment in the abstract a little bit off-putting:
> Planck did not consider this a quantization, but merely a mathematical trick to be able to calculate the entropy of the oscillators.
My understanding was that Planck absolutely understood that his approach would have been a mathematical trick if he took the limit h → 0, but that in stopping at a nonzero small number he was explicitly aware that he was saying something peculiar about the energies in the system, and had strayed far away from that realm of pure mathematics into something that we would today effortlessly identify as quantum, even if that word did not exist at the time.
Often, when inventing something new - it can be difficult to assess how novel the "new" thing is. Particularly when there isn't yet a word for it. Planck may have simply believed that this hinted towards something equivalent of an "atom" of light. Atom's were after all a relatively recent discovery in 1827, why couldn't you have an atom-like construct for light? and why would light atoms be any different regular atoms?
While we now know a great deal about this topic - placing such speculation in a paper would be problematic. Hypothesizing that such quantizations are common for other quantities would be even more problematic.
EDIT: Removed eroneous mention of michelson-moorly instead of milikan oil drop experiment.
> Atom's were after all a relatively recent discovery in 1827
Atoms were controversial well past that. Their existence was not definitively settled until Einstein's work on Brownian motion in the early 20th century (which, incidentally, is what he won the Nobel Prize for, not relativity — Update: turns out I got that wrong. See child comment.). The controversy around the atomic theory was so intense it drove Ludwig Boltzmann to suicide [1].
The question of whether light is a particle or a wave dates back to at least Newton (who thought it was a particle) and Hyugens (who thought it was a wave). By the end of the 19th century, before Einstein brought up the photoelectric effect, the consensus opinion was pretty firmly on the "wave" side of the dispute, and apparently Planck was not an outlier. See another comment: https://news.ycombinator.com/item?id=39349027
Even though this is tangential, I think it's important to note that this experiment should be called as the Millikan-Fletcher oil drop experiment to acknowledge Harvey Fletcher's contribution to this experiment as a grad student which he was coerced into relinquishing to receive his PhD
> It might have been thought, by some scientists in the 1890's, that refined mathematical analysis of this kind would play a role in resolving the fundamental problems of classical physics associated with the apparent failures of the equipartition theorem. But that is not what happened.
> Although the quantum hypothesis did dispose of the paradox of specific heats of polyatomic gases, and eliminated the possibility that ether-vibrations (having an infinite number of degrees of freedom) would drain an indefinite amount of energy out of material systems at any finite temperature, these were not the anomalies that provoked the introduction of the quantum hypothesis in the first place. Max Planck was not one of the physicists who worried about the validity of the equipartition theorem before 1900, and the myth that his distribution law for blackbody radiation was concocted merely to escape from an "ultraviolet catastrophe" predicted by the Rayleigh-Jeans law has now been thoroughly demolished. It was Paul Ehrenfest who invented the ultraviolet catastrophe (eleven years after the publication of Rayleigh's and Planck's papers in 1900) in order to dramatize what would have been the consequences of the equipartition theorem if it had been valid for all classical dynamical systems (though neither Rayleigh nor Planck believed that it was).
I have this saved as a note, but can't find the exact source atm. Here's another source though, from the 60s:
https://sci-hub.ru/https://doi.org/10.1007/BF00327765