I’ve never been able to understand this phenomenon. How is it proof of the Big Bang?
In: 7
Oh… So many wrong explanations…
First, what is CMBR?
After the big bang, the universe was a lot denser than today. If there’s more energy at less space, than the temperature at that space is higher. In fact, it was so hot, that atoms didn’t exist (actually, as you go back, even baryons didn’t exist, because there was so much energy at one place, that quarks couldn’t combine).
So, at some point we have a bunch of free electrons and protons, and the radiation scatters like crazy when it hits an electron. Think of it as a lamp behind a really thick fog. In other words: The Universe wasn’t transparent to those remnants of the big bang.
But as the universe expanded, it also cooled down, allowing those electrons and protons to combine into hydrogen atoms. And Hydrogen atoms don’t really interact with that radiation, so, the universe became transparent to the radiation, so the radiation follows a straight path now, like a ray of light. That’s what CMBR is: Radiation that we can see after the universe was cold enough to allow the formation of atoms. (One analogy is comparing to a cloudy sky: The Sun is the heat from the big bang, the clouds are the “soup” of particles before the formation of atoms, and the light that pass those clouds is the CMBR).
Why is it evidence for big bang?
1. Redshift indicates expansion of the universe.
2. In theory, you would expect a certain amount of radiation, at a certain temperature and energy distribution. Guess what? The measurements made of the CMBR fits those predictions (and to a scary level of accuracy).
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