Paul Drude: The Theory of Optics (1900)

In 1900 Drude brought out his book on optics.  Though comprehensive, the aim of the book was to introduce the reader to recent developments in the field and to enable them to follow the new work in the area.  Drude’s book was quickly translated into English by R. A. Millikan and Charles Riborg Mann.  The earliest edition of the translation seems to be from around 1902 and has a foreword by A. A. Michelson dated February 1902.  Michelson notes that the translation of Drude’s book makes the progress of the last ten years (1892-1902) in optics accessible to the English-speaking public and gives the first complete description available in English of “the development of the electromagnetic theory” and “the relation between the laws of radiation and the principles of thermodynamics.”

So, this book and its translation bring together a lot of elements – a kind of time capsule or snapshot of a highly transitional moment.  For example, in 1900, the electron, which had around as electrons, “ions” or “corpuscles” during the 1890s, had already even been officially discovered.  One of Drude’s translators, R. A. Millikan, would go on to measure the charge of the electron most laboriously from 1908 to 1913 with apparatuses like this:

X-rays were being created and misinterpreted sometime as longitudinal vibrations of the aether (says Pais Inward Bound page 41):

But Drude seems to have avoided that particular problem and kept all his electromagnetic waves transverse – at least partly because he usually keeps polarization in mind when discussing waves.  Another angle on the Drude 1900 snapshot is the foreword by A. A. Michelson, who is probably familiar to most people as the Michelson of the 1887 Michelson-Morley experiment that suggested the effects of the earth’s motion through the aether were very hard to detect at all in terms of its direct effect on light (assuming no aether dragging).  Of course, Michelson is also apparently the only physicist to have figured in an episode of Bonanza! (1962).  Drude’s book describes the Michelson interferometer but says little about Michelson’s youth in the Wild West.  Here is Michelson in the 1920s measuring the non-detectability of the aether at a site far from what might one day be the set for Bonanza!

A chess game in the aether:

Larmor’s Rococo Electron

By February 1894 no one felt that Larmor’s theory with its thermodynamically-driven, charged (but otherwise hydrodynamic), core-powered vortices was doing a good job of grappling with the aether, notes Buchwald on page 162 of From Maxwell to Microphysics.  On April 2, Larmor wrote to Fitzgerald:

“My interest in the whole thing is not so keen as it was; but I still claim that as a dynamical analogue of the aether-action it is far wider than any other I ever heard of…”

So Larmor was not too keen on the whole model.  Moreover on March 30, Fitzgerald had pointed out that if you were going to have matter at the core of the vortices, you could just let the matter there do the electromagnetic work that was making the aether stress, pulsate, lose elasticity and rupture or just get whirled around the fizzy edges of the vortices.  You could even have poor old simple, unstressed, unruptured, un-fizzy, non-vorticidal matter just move around and have charges and so on.

By June 14 Larmor had abandoned the “vortex atom – the source of all his problems” notes Buchwald on page 167.  By August, he was working out how electrons worked (mind you, this is three years before J. J. Thomson officially discovered something that we now think of as electrons – though you can see why – given what Larmor was replacing with “electrons” – Thomson wanted to call them something else) which resulted in a much simpler and less “baroque” set of models.  Buchwald calls the final form of Larmor’s “vortex atom” the “baroque mechanism” and it does seem bizarrely convoluted.  The electron that Larmor used to replace the baroque mechanism of the vortex atom is more Rococo and it echoes in some mechanisms that Olafur Eliasson installed as “Baroque Baroque” works in what looks like an incipiently Rococo palace in Vienna in 2015:

So, as Buchwald notes (page 127 of From Maxwell to Microphysics), Larmor was one of the first Maxwellians to give up Maxwellian theory.  The fact that Maxwellian theory was disappearing rapidly in the late 1890s will no doubt come as something of a shock since Maxwell’s basic field equations are correct – at least as they are now understood – what had to be given up was essentially the aether as an overall dynamic engine.  Something aetherial could be retained as microfields and things such as vaguely aetherial “virtual oscillators” and so on were retained as late as 1926 or so even in quantum mechanics, but the aether as a sort of universal “imponderable” luminiferous fizzy medium powered by vortices was disappearing very quickly in the late 1890s.  As Buchwald says on page 127, in 1893, Larmor was a Maxwellian.  By 1895, he was not.  Larmor’s critique of a magneto-optic theory using an elaborated aether in 1895 concludes the theory “retains the dynamical equations and surface conditions which belong to the luminiferous aether under ordinary circumstances, merely adding on to the electric force a new part of magneto-optic origin.  This would hardly be open to objection if it worked, but it is admitted that it does not work…”