Post by nickrr on Aug 14, 2016 13:43:28 GMT 1
Yes - a few microseconds or 380,000 years, amounts to the same thing doesn't it? Why is it only arriving here now?
I think that the key is to realise that the CMB didn't originate at some specific place it originated everywhere - we were inside the area where it originated. So we always have and always will receive CMB as there will always be a set of points in the universe that are just the right distance away from us such their CMB is just arriving. Close to the point in time when the CMB originated this radiation will have been from somewhere relatively close to us. Now we are receiving CMB from parts of the universe much more distant. And of course there will be distant areas of the universe that are just now receiving CMB from our point in space.
For how long was this continual emitting process supposed to have lasted? And are you saying that were we or some alien race able to detect the CBR at, say, 400,000 years ago, they wouldn;t have detected any such radiation?
The CMB originated as the universe cooled enough to allow charged electrons and nuclei (vast majority of which were protons and helium nuclei) to combine to produce neutral atoms. This allowed electromagnetic radiation to travel freely and it's this radiation that forms the CMB. I guess that the time it took for this process to occur depends on how even the temperature was through the universe at that time. No doubt some parts of the universe cooled slightly more quickly than others but I suspect that the time it took for the whole universe to pass through this stage was small compared to the age of the universe.
As I argued above my understanding is that all parts of the universe will always be receiving CMB as every part of the universe is a source of CMB and so there will always be part of the universe that is just the right distance away for us to be receiving CMB from it.
Yes - that's what I said the theory must imply. That we are travelling away from that origin at very very close to the speed of light. But, unfortunately, that is not the theory.
But bear in mind that the origin is everywhere, not a specific place.
I'd stress that all of this is how just I understand these things.