Re: Old Stars/Olber's Paradox

[Bowman_David/tiger_mpc@tiger.gtc.georgetown.ky.us]

Jack U. wrote:

> because the sky is obviously not "dark"; it is in fact quite "bright",
> as a couple of guys from Bell Labs discovered, but at a temperature of
> about 2.7 degrees K (black body).  I would, however, modify the
> statement by excising the words "(& dimmer)".

The reason that I included the words "(& dimmer)" is that since the
universe has expanded by a factor of about 1000 since the cosmic photons
were created, this means that now their temperature is 10^-3 times their
initial value, their number density is 10^-9 times their initial value,
and their energy density and energy flux are 10^-12 times their initial
values.  I would call such an effect "dimming".

David Bowman
dbowman@gtc.georgetown.ky.us