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Stoke's model of the luminiferous aether

  1. Dec 9, 2012 #1
    I have been reading up on the luminiferous aether as a background to the Michelson-Morley experiment of 1887. I am currently stuck on understanding a point in Stoke's model of the aether ( The "Silly-putty model")

    Everywhere I have searched online mentions how he proposed that the aether should be rigid at high frequencies yet fluid at lower velocities. I understand why the model needed to be fluid for objects at lower speeds - to not impede the passage of planets. However I don't see why it needed to be postulated that the aether must be solid and incompressible to allow for light waves to pass through it?
     
  2. jcsd
  3. Dec 9, 2012 #2

    Bobbywhy

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    This is from http://www.sinequanonthebook.com/AetherHistory2.html

    “Stokes and the Dragged Aether

    In 1845 George Gabriel Stokes (1819–1903) nonetheless attempted to account for stellar aberration on the basis of a theory in which the earth drags along the ether in its vicinity. The attempt involves careful consideration of how the wave fronts of stellar light change direction upon entering the earth’s ether atmosphere. On Stokes’ account, rather than an apparent motion, the light ray really is “refracted” during its passage through the ether. Stokes was interested in such an alternative account of aberration because he believed the hypothesis of an immobile ether to be highly implausible. The new picture of the aether after Young and Fresnel--the aether as a solid to restore the distortions of a transverse wave--is difficult to reconcile with the hypothesis of an immobile ether undisturbed by the motion of matter. It was much more natural to assume that matter drags along the ether. It was Stokes who became the champion of this view. He put forward a model of the aether that has been described as the “Silly Putty” model. Stokes’ aether behaves as a rigid solid for the high-frequency oscillations constituting light and as a fluid for the relatively slow motion of celestial bodies travelling through it. The latter motion, however, no longer leaves the ether undisturbed. At the earth’s surface, the ether will be at rest with respect to it. The price that Stokes had to pay for his more realistic model of the ether was therefore a more complicated explanation of aberration.

    Although many attempts were, and still are being, made to explain stellar aberration in terms of a monolithic aether, primarily because of "aether drag"--they all are flawed. A monolithic aether, or aether drag on earth, cannot account for the phenomenon of stellar aberration.”

    Stokes’ “Silly-Putty” aether proposal was designed to explain stellar aberration, and not about the Michaelson-Morely experiment. So why do you want to learn about a flawed and failed proposal shown to not conform to reality? Are you interested in why his explanation failed?

    Cheers,
    Bobbywhy
     
  4. Dec 10, 2012 #3
    When someone states that a material is "solid" you need to realize that the material must still be elastic at some local level, otherwise any force perturbing it would necessarily perturb the material as a whole. If a material were entirely solid, the remote ends would propagate instantaneously in phase with the end that encounters the disturbance, i.e. it no longer functions as a medium.

    The molecules in a steel bar, for instance, are locally elastically bound and therefore sound propagates through the material as a medium.

    The problem with a highly elastic material, or medium that is elastic in beyond a local scope, is that energy disperses quickly and the medium becomes absorbing. Electric and magnetic energy though, shows no signs of absorption or dispersion in a vacuum. That indicates that on a larger scope, any medium that sponsors EM propagation (in a vacuum) would need to have that characteristic of a solid material.
     
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