Dear Craig Franck:
"Craig Franck" <craig.franck@xxxxxxxxxxx> wrote in message
> Since most red shift is produced by space expanding
> rather than the speed of a galaxy at the time a photon
> was emitted, how does the relativistic effect of
> supernova periods slowing down get introduced?
If something is moving away from you via:
- kinetic velocity, or
- Universal expansion, ...
all time-based phenonmenon are red-shifted. As far as the
"stretching" of the duration of a supernova, you can think of a
series of trains heading for Earth, representing the arriving
photons. As the distance gets greater, it takes longer for the
"train load" of photons to arrive for each successive time
It doesn't *matter* what causes the increase in distance.
> If light is getting stretched it seems the information in
> a pencil of light would take longer to get here (silly
> puddy effect), but that explanation seems a bit off for
> some reason.
Agreed. "Stretching of light" implies a mechanism that can
affect individual photons other than the handfull of mechanisms
we know. We can lose all of the energy of a photon (to gain it
back in some other way), but we can't remove just a little of it
and still stay specular.
Individual photons do appear redshifted by Universal expansion.
But it is "stretching" of the succession/procession of photons
that explains the stretching of supernova light curves.
David A. Smith