This probably has the wrong tag on it, for which I apologize. If I’m not mistaken, this is cosmology not just physics.
Anyways, how exactly does the background radiation suggest a universe with a beginning? Couldn’t the same kind of radiation exist in a more static one?
In: Physics
No. The cosmic background radiation is basically saying: in every direction, *everything* was insanely boiling hot at some point in the past, and it was all basically the same temperature everywhere (with tiny fluctuations). Since we’ve established beyond reasonable doubt that the universe is expanding, the only way that makes any sense is if all the matter was closer together at some point in the past.
Put the two together, and you have a very simple conclusion: the universe used to be really hot, dense soup, and now it’s very not-dense, cold soup.
The cosmic microwave background has a *lot* to say about the past and current state of the universe. This is only the tip of the iceberg.
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