(History of science/physics) sources for the "elastic ether" theory of light?

by Themoopanator123

Before the presence of electromagnetism, speculative work was done on the possible mechanics of the hypothesised "elastic ether", believed by some to be the medium of light waves which oscillated elastically.

Philosopher of science Philip Kitcher cites Augustin-Louis Cauchy, George Green, and James MacCullagh as physicists who proposed mathematical models of the elastic ether.

I was wondering if anyone knew of good secondary sources where I can read about their models? I'm looking primarily for secondary sources which couch things in terms which are more familiar to modern physicists/physics students, as I want to be able to have some grip on what's being written and, honestly, I find myself completely lost when reading the firt-hand writings of historical physicists.

Thanks.

wotan_weevil

A good book covering the major ether theories is Whittaker's A History of the Theories of Aether and Electricity. The first edition,

  • Whittaker, E. T. (1910). A History of the Theories of Aether and Electricity: from the Age of Descartes to the Close of the Nineteenth Century. Longmans, Green and Co.

is available online at https://archive.org/search.php?query=%22History%20of%20the%20Theories%20of%20Aether%20and%20Electricity%22

The 2nd edition was split into two volumes:

  • Whittaker, E. T. (1951). A History of the Theories of Aether and Electricity. Volume 1: The Classical Theories. Thomas Nelson and Sons.

  • Whittaker, E. T. (1953). A History of the Theories of Aether and Electricity. Volume 2: The Modern Theories. Thomas Nelson and Sons.

The second volume in notorious for Whittaker's description of Einstein's first 1905 paper on special relativity as Einstein "set forth the relativity theory of Poincaré and Lorentz with some amplifications, and which attracted much attention". The first volume is the one relevant to your question, but the 1st edition is fine.

For the simple case of the propagation of electromagnetic waves in a homogeneous isotropic medium, the various models of the ether as an elastic solid work well (and are largely identical). Where problems arise is where media are inhomogeneous or anisotropic, and in particular at interfaces between two media. For example, the vector quantities in the partial differential equations describing the motion of the elastic ether are usually interpreted as displacements and/or velocities (or momentum density) of the ether. Such interpretations were typically incompatible with the boundary conditions required to make reflection and refraction work - in particular, the boundary conditions needed to preserve the waves as purely transverse, not generating a longitudinal component through refraction. For example, this was a serious logical problem with Cauchy's theory.

For an excellent and detailed coverage of Maxwell's ether theory (which led to the equations for his electromagnetic theory), see:

  • Malcolm S. Longair, Theoretical Concepts in Physics: An Alternative View of Theoretical Reasoning in Physics, 3rd ed, Cambridge University Press, 2020. https://doi.org/10.1017/9781108613927

The older editions are fine.

One interesting ether paper that Whittaker doesn't discuss is Euler's work:

  • Euler, L., 1746. "Memoire sur l’effet de la propagation successive de la lumiere dans l’apparition tant des planetes que des cometes". Memoires de l’academie des sciences de Berlin 2, 141–181.

This is notable for its early derivation of radiation pressure; in the 19th century wave vs particle debate about light, those who argued that light must be a wave because "we don't observe radiation pressure" should have read it (but clearly didn't). Euler models light as acoustic waves in a gas, rather than an elastic solid. Alas, I don't know of an English translation of this paper.

Finally, for a short (4 page) non-mathematical summary of the life and death of ether theories, see: