(Ned Wright) wrote in message ...
The problem with this idea is that the motivation for a tired light model
is to preserve a static Universe. In a static Universe the light travel
time between the supernova and the observer has to be constant, and thus
the observed duration of the lightcurve has to be the same as the emitted
duration of the lightcurve. To say otherwise is to throw out the baby
with the bathwater.

However, it is true that if you halve all frequencies you double all
durations including the lightcurve duration. This is exactly what the
standard Doppler or expansion model for the redshift does. But you
really need an expanding Universe then to accommodate the greater
light travel time seen at the end of the lightcurve.

--Edward L. (Ned) Wright, UCLA Professor of Physics and Astronomy
See http:www.astro.ucla.edu/~wright/cosmolog.htm

Your argument would be correct for light propagating through a perfect
vacuum, but not if you have a kind of dispersive medium. In this case,
the lightcurve would correspond to the group velocity of the wave but
not the phase velocity, and, as you have realized yourself on your
page http://www.astro.ucla.edu/~wright/an...ispersion.html in a
different context, you can then not strictly apply the 'propagation
time' argument anymore.
I don't want to push the comparison with dispersion too far though at
this stage, yet it should be clear that a 'stretching' of the
wavetrains of light between the charged particles in the intergalactic
plasma (as suggested on my webpage
http://www.plasmaphysics.org.uk/research/#A11) should redshift the
frequency as well as broaden the lightcurve, even in a static universe
(as indicated in my opening post above).


[[Mod. note -- It seems to me that a plasma effect would be (strongly)
frequency-dependent. Astronomical redshifts are independent of frequency,
so I don't see how a plasma effect could produce them. -- jt]]