On Tue, Oct 29, 2024 at 9:09 AM Alan Grayson <[email protected]> wrote:
> > > On Tuesday, October 29, 2024 at 6:52:12 AM UTC-6 John Clark wrote: > > On Mon, Oct 28, 2024 at 10:59 PM Alan Grayson <[email protected]> wrote: > > *>>> When the luminiferous aether was rejected as non-existing, how was EM > wave motion explained? AG * > > > *>> Vibrations in the electromagnetic field.* > > > *> How are the vibrations created and maintained? AG * > > > *Maxwell's Equations will answer those questions. It turns out that if you > change the intensity or direction of an electric field, that is to say if > you accelerate it, then you create a steady magnetic field, and if you > accelerate the intensity or direction of a magnetic field then you create a > steady electric field. And if you don't just accelerate it but "Jerk" the > field, that is to say accelerate the acceleration, then the corresponding > field it creates is not steady but changes with time. * > > *This obviously leads to the creation of a wave, and Maxwell's equations > will tell you how fast that wave will propagate, and it turns out to be the > speed of light. What Einstein found to be so unusual and interesting is > that the speed of light that Maxwell's equations spits out is not relative > to anything, it is an absolute speed, the only absolute speed in the > universe. Einstein thought deeply about that and it eventually led him to > Special Relativity, and then 10 years later led him to General Relativity.* > > > > *How can anything have a velocity relative to nothing? Calling the > velocity absolute, explains nothing. AG * > The velocity of light is always defined relative to an inertial reference frame which can be constructed out of physical rulers and clocks (synchronized by the Einstein convention). It is "absolute" only in the sense that when you go from one frame to another via the Lorentz transformation, the velocity of a light ray will be unchanged, and in general all the dynamical equations written down by Maxwell are unchanged when you switch coordinates via the Lorentz transformation. This general invariance was discovered just prior to Einstein's 1905 paper, see https://en.wikipedia.org/wiki/History_of_Lorentz_transformations#Larmor_(1897,_1900) which mentions it was 'shown by Lorentz (1904) and Poincaré (1905) that they [Maxwell's equations] are indeed invariant under this transformation to all orders in v/c'. Not sure why they didn't make the leap to discarding the notion of aether, maybe they imagined that other non-electromagnetic laws of physics would not be invariant under the Lorentz transformation, so that by comparing electromagnetic and non-electromagnetic phenomena it might have been possible to discover an aether rest frame? Jesse -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/everything-list/CAPCWU3JGmFH%3DxkRwQP_qGnUK0uuVJaiTW%2BvziBOH_TrRHX2-mw%40mail.gmail.com.
