CMBR is electromagnetic radiation within microwaves zone of the spectrum and coming from all the parts of sky. It is right to think of it as a form of (invisible) light coming from everywhere. Source of CMBR is said to be the state of Universe as it existed some 380,000 years after Big Bang. At that time, according to the Big Bang Model, diameter of Universe was 43 million light years.
This state of Universe is said to emit light for the first time. Originally it was compressed radiation of visible glow. But it is said that Universe was expanding and light was also expanding. That light is now reaching us in expanded (invisible) form and now lies within microwaves zone of spectrum and we call it CMBR.
But that early state of Universe lasted for a maximum period of only 600 million years as after this time, galaxies appeared. It means that source of CMBR lasted for only 600 million years. If we assume or accept a non-expanding universe then we are living in a perfect age where we can observe this radiation.
But Big Bang defenders argue that universe is not static. Universe is expanding faster than speed of light and redshifted light is chasing the Universe. So they conclude that CMBR shall stay for ever.
The point to be considered is that CMBR has been explained only in the expanding Universe context – and that also in such an expanding Universe that is expanding faster than light itself. If these assumptions are not true then Big Bang supporters have no alternative justification for the CMBR.
Image credit: ESA and the Planck Collaboration.
In fact our Universe is static. CMBR is redshifted light of very remote areas of Universe that extends like infinity. It is in accordance with Olbers’ ‘paradox’ which is not a paradox as such. Olbers’ simply did not know Hubble’s law in his time (19th century) so he did not know that light coming from far off distances was to be more redshifted. Exactly in accordance with Olbers’ paradox, our night sky is actually fully bright. But it is bright in redshifted to invisible spectrum zone. That’s why our night sky is not really bright. And this CMBR is actually the proof that we live in an infinite universe. Olber’s ‘paradox’ already contained prediction of CMBR and thus credit of prediction of CMBR does not exclusively belongs to the Big Bang Model. Further details have been explained in the book.