From: vitalmis@bigpond.net.au   
      
   Roger wrote:   
      
   > I was hoping someone could help me with the following   
   > question. I am trying to understand something of the size   
   > of the universe, and I came accross a quote that said "the   
   > universe is expanding in all directions, and that the   
   > 'Cosmic Microwave Background' (the remaining heat from the   
   > Big Bang, is found at a distance of 15 billion light years   
   > from us in all directions."   
   >   
   > Tow questions result from this:   
   > - does this not suggest the universe is ball-shaped, and   
   > - that the earth is pretty much at the centre of the   
   > universe, near where the Big Bang occurred?   
      
   While the ballon analogy is good with regard to the geometry   
   of the cosmic expansion, it's not terribly good for the   
   physics. It suggests that there is some sort of expanding   
   entity that the material bits of the universe are attached   
   to and that isn't so. Basically the Big Bang was an   
   explosion and in an explosion all the bits are rushing away   
   from all the others, and the relative speed between any two   
   bits depends on how far apart they are. However, the   
   explosion analogy suffers because that suggests there is an   
   edge to the exploding material and that isn't so either.   
      
   For your particular problem here consider that when you look   
   at something what you see is not what the thing looks like   
   now, but how it looked when the light you are seeing left   
   it. So when you look into the night sky you see things not   
   so much a long way away, but rather a long time ago. And a   
   very long time ago the entire universe was filled with a   
   glowing plasma. So it doesn't matter which direction you   
   look, when you look past the more recent objects you see   
   that plasma. The light from that plasma is the microwave   
   background.   
      
   K Harwood.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)