turbo-1 said:
Back to my initial question - through what medium does EM propagate across empty space? You know what I believe that medium to be. Are there alternative views?
There is a lot more one can say here, by using first principles.
This is my personal take on “The Medium” :
EM propagation is only a degenerated (mass less) case of the more general
quantum field. Any explanation in terms of media should take in account
that all fields/forces are equally subject to SR/GR. If SR/GR is determined
by a medium then this mechanism is more likely to occur at a level "deeper",
that is, where there is unification.
The clues from e^{-iEt/\hbar}\ \ ….
One can try to assign a physical interpretation to the term above like
vibration, spin or precession. A free relativistic (say Klein-Gordon) wave-
packet in its rest-frame will have a phase which is equal over all of space.
The deBroglie wave length is infinite at rest. A finite deBroglie wave-
length is only seen in reference frames other then the rest frame as a
result of the non simultaneity of SR.
( see for instance here, in tutorial style ) :
the relativistic kinematics of the wave packet
It is this synchronization of phase over all space which gives us important
clues. Such a synchronization is only possible with a repetitive signal. This
leads us to the investigation of spin-lock in 3 dimensions. The (discrete)
components of a medium propagate their own phase to all their neighbors
with velocity c. The neighbors must all lie at distances which are integer
multiples of the wavelength in order to establish synchronization. Only in
this case they will all have equal phase.
This requirement of integer multiples is trivial to fulfill in 1D but impossi-
ble in 2D and 3D. There’s simply no regular grid in 3D that fulfills this.
It becomes easier however if the average distance is much larger then the
wave-length (n >> 1) and its easier to find an optimal location. This leaves
precession as the only physical interpretation of phase (from the three
mentioned) since the Compton wavelength is much to coarse to fulfill this
requirement.
So we could interpret the phase frequency as a precession of a spin at
much higher frequency and much shorter wave length somewhere in the
direction of Planck’s scale and Planck’s frequency. A (single?) spin
frequency at Plank scale might give rise to the multiplicity of (precession)
frequencies as we see them. There are at least 3 space dimensions
required for precession to occur.
Then there is a second prescription required by phase synchronization:
All components of the medium (say particles) that are synchronized to
each other, and have the same phase, must be at rest in respect to each
other! Now in a typical vacuum however you would expect to see
things at all kinds of speeds ranging from zero to c.
The second prescription splits the single medium into many media, one
for each velocity and its direction. Two waveforms of different energy can
coexist both synchronized in their own rest frame while perceiving the
synchronization signals of the other as high frequency noise. We can see
here a physical explanation of Pauli’s exclusion principle for particles
with the same energy.
One can show, just using standard SR and QM math that if a wave-packet
Has any physical meaning that the medium incorporating it should have
The same physical speed a the particle embodied by the wave-packet.
The synchronization requirement simply picks those elements of the
media which happen to have a near equal speed.
Again, see here:
the relativistic kinematics of the wave packet
This directly satisfies the requirement of SR that the laws of physics are
equal in different reference frames even though we have a medium. In a
different reference frame a different subset of the medium is selected:
The subset that moves at the required speeds and directions to enable the
synchronization of the QM phases.
If we now go back to EM propagation then it would be no more than logical
to expect that photons and their EM wave function (and thus their medium)
also move at the same speed, that is, the speed of light. This presents us
the typical Einsteinian picture where particles, including photons, move
with the speed they have (including their wave-packet) instead of being
waves in a medium.
The *propagation* through a medium nevertheless plays an essential role,
but indeed at a level lower at which we can assume that unification has
occurred. We need something to communicate the phases for our subsets
of the vacuum in order to achieve synchronization. This has to be a level
lower since it communicates phase *between* the constituents of what
we have called “the medium” until now.
This finally would then be what bestows the limit of c upon us. Physical
wave-packets can not move faster then c because the synchronization
mechanism falters beyond it.
Regards, Hans