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Originally Posted by Thanatos
The CMB was hotter in the past. This is very difficult to explain without an expanding universe model:
Molecular Hydrogen in a Damped Lyman-alpha System at z_abs=4.224
http://www.arxiv.org/abs/astro-ph/0602212 |
We have a static observation of 2.73 K for the CMB. How do we know that it was once hotter? Has anyone observed a temperature change?
We know the CMB was once hotter because the universe is expanding and we know the universe is expanding because the CMB was once hotter but is there any evidence for change outside this circular loop?