From: helbig@asclothestro.multivax.de   
      
   In article , Gary   
   Harnagel  writes:   
      
   > On Saturday, January 13, 2018 at 12:56:39 AM UTC-7, Phillip Helbig   
   (undress to reply) wrote:   
   >   
   > > The density of a galaxy is, on average, about 1 proton per cubic   
   > > centimetre.  So even at quite large redshifts---certainly at the   
   > > redshifts where we can see individual galaxies---the density is quite   
   > > low, and the gravitational redshift is negligible compared to the   
   > > cosmological redshift.  The entire observable universe would fit inside   
   > > a ball with the radius of the asteroid belt and be no denser than a   
   > > neutron star.  This is an appreciable density, but the cosmological   
   > > redshift would again be much larger.   
   >   
   > But a mass with neutron star density only slightly larger than a neutron   
   > star would be a black hole ... with infinite red shift :-)   
      
   Yes.  This is just an example to show how thinly spread out the universe   
   is: everything we can see---with our largest telescopes---would fit   
   inside the solar system if compressed to nuclear density.  Of course,   
   this wouldn't be stable, and of course if we imagine the universe itself   
   this size, then one can't really talk about a black hole.   
      
   > > In short, there is no mystery here.  The evidence for the big bang from   
   > > regions with negligible gravitational redshift is sufficient.   
   >   
   > I'm having trouble picturing why we should see the CMBR at all.  Since it's   
   > traveling at the speed of light but we're moving somewhat slower, shouldn't   
   > it have passed us long ago?  I know, the FLWR metric must have something to   
   > do with it, but ...   
      
   We can think of ourselves as not moving at all.  By definition, light   
   moves at the speed of light.  But the CMB was produced at every point in   
   space.  So today we can detect photons which were produced (or last   
   scattered) at a certain distance, tomorrow we detect ones from slightly   
   farther away, and so on.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)