Quote:
Originally Posted by batema
Thers was a suggestion that the post I put in the general chat section be moved here so I thought I would move it.
I need some clarification please as I think I am misunderstanding this completely when I thought I had it under some sort of control.I think I was of the understanding that the radiation being received has come/travelled across from 13.7 billion light years and as a result of the universe expanding has undergone a red shift stretch factor that has put this radiaiton into the microwave zone. But I have read that this radiation is the same everywhere and distributed evenly through the universe and I don't get it know. Can anyone simply explain this concept to a simple mind. I find this facinating and would like to clear my confusion. I listened to a 365 days podcast that talked about the background radiation being like a blueprint of the structure of the universe that exists today that is found in the radiation itself.
Mark  |
Hi Mark;
You seem to have the gist of it, just fine. I'm not quite sure of where your confusion might be.
The theorised time sequence of the Big Bang proposes that radiation (photons) decoupled from matter, when all the electrons finally recombined after the initial enormous energy involved, to form the first atoms. This is referred to as the time of last scattering, about 380,000 years after the Big Bang (BB).
The CMBR, is due to the extreme redshift of these photons which highlights their age. Its electromagnetic spectrum also corresponds nicely with the BB prediction. The observed patterns (slight intensity changes) in the CMBR today, is then thought to correspond roughly to the way the universe looked at the time of last scattering.
Under the BB theory, after the time of last scattering, the energy of the photons would have been stretched by the expansion of the universe, which would have left the spectrum with the same shape as it has today, (ie: a near blackbody spectrum profile).
The theory also predicts the temperature drop to present day, (down by a factor of about 1,100), as everything cooled over the eons. The CMBR photons now measure in the microwave range of the EM spectrum, as predicted.
CMBR comes from all parts of the sky, with almost equal intensity and has a pattern the same as would be expected if a uniform, hot, evenly distributed gas was expanded to the size of the observable universe. The observation would look the same no matter where it was viewed from, because the universe expands evenly in all directions, the further the object is, the bigger the redshift, (the faster it is receding - Hubble's Law), and the CMBR presently has the largest observable redshift (z =1089 approx).
Hope this helps.
Cheers