Julian Kalmar wrote:
"Kevin Aylward" wrote in message
...

François Guillet wrote:

"Kevin Aylward" a écrit dans le message de news:
...

Julian Kalmar wrote:

Hello All:

I wonder, is the permittivity and permeability of free space
considered to be the same in all reference frames... inertial and
non-inertial?


Yes. If they weren't, then the speed of light would not be invariant
wrt. inertial frames.

Not enough. If they weren't but their product constant, the speed of
light would remain invariant.


But the "impedance", i.e E/M, of space would then also be non constant
in that case. This would case some issues.


Hello Kevin:

This is precisely what I'm after... does the impedance change and, what are
the issues?

The quantity in question is Zsub0 which is pretty nearly
377 ohms IIRC. Among other things, it's the starting point
for antenna design, IOW the impedance you have to match (in
a manner of speaking) to get a signal to propagate from a
source/into a load. For starters, think about an atom trying
to radiate away excess energy, or a bunch of them trying to
come into equilibrium with their surroundings. For that
matter, consider how the Coulomb force between a nucleus and
orbital electrons will be affected, or between protons in a
nucleus.

377 ohms/square is also the equivalent sheet resistance
of the "surface" of a black hole, for fairly obvious reasons
BTW.

To go a bit deeper, look up how Zsub0 is defined. Will c
be the same?

It looks like you'd need something like a 3D spatial
discontinuity (analogous to cosmic strings, except over a
volume) which would amount to a different "phase" of vacuum
from what we live in. There'd have to be an interface
between this volume and ordinary space; think about what
would happen to photons or matter trying to cross the interface.

There are other issues. See what you can come up with.

Mark L. Fergerson