🚀 go-pugleaf

In article <3NOV199215121855@csa2.lbl.gov> sichase@csa2.lbl.gov (SCOTT I CHASE) writes:

>> Regardless of whether [ neutrinos ] have mass, they definitely have 
>> energy, and that's all that counts, right?
>
>Yes.  But the neutrinos have so little kinetic energy that even a small
>mass (a fraction of an eV) would dominate the total energy of the 
>cosmic neutrino background, which if I remember correctly, is at even
>lower temperature than the 3K photon background.  Even if this is not 
>correct, you can easily see that a reasonable mass would dominate if 
>you remember that room temperature corresponds to kT = 1/40 eV.


Thanks for the explanation.  Just to continue as devil's advocate... If the
neutrino and photon backgrounds are at different temperatures, then might
not the background for at least some variety of neutrino be at a HIGHER
temperature?  Taken to extremes, this would allow any amount of energy in
massless neutrinos.

I'm a bit surprised that the temperatures are different.  I can believe
that present photon/neutrino interactions are not sufficient to produce 
equilibrium, but wouldn't it be sufficient for equilibrium to have been
present in the early universe?  I'd think that both backgrounds would then
cool at the same rate, as the universe expands.  Hmmm... maybe the two 
backgrounds both cease to have significant interactions with anything 
else at some point, but the points are different for the two...?

    Radford Neal