eli5, How’s the CMB still here and Does light carry multiple information at one time?


Photons can carry information by reflecting off of something or outright being generated by something. My question is how can we see the CMB if photons change the information they’re holding. For example if i shine a light for 2 seconds inside a room at something a bit reflective, but keep my eyes on something else, say a table which is say in the opposite direction, how can i come to the understanding to the prior information that, that light was holding aka the reflective matter? I can see the table, but the light coming off of it doesn’t carry the information about that reflective matter.

In the case of the universe, the CMB is light that has been created by the big bang and has been traveling ever since. If it bounces of my body, it would lose the information about the CMB and would then catch the information about my body and carry that with it, if you have some special goggles you can see me but not the CMB. Basically my question is how did the light from the CMB survived and how it’s still here? I understand that the further we look, the more we’re looking in the past and where it all came from and that’s why Hobble could see it. But how can that light be here and still carrying that information? Also Does my question even make sense?

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3 Answers

Anonymous 0 Comments

Because the light we are seeing from the CMB is light directly created by the early universe that hasn’t yet interacted with anything else yet. When we analyze it with our telescopes, that will be the first thing those photons have hit for billions of years. These are primordial photons we are dealing with here.

Anonymous 0 Comments

Light waves have frequency, position, and direction.

If we absorb a bunch of frequencies, the leftover frequencies that are not absorbed tell us what color was seen. This is why if your room has an orange wall and you illuminate the room by lighting that wall, everything appears orange.

The position of the object is discerned by the direction the light came from.

The CMB is still there because it’s been traveling through space and hasn’t hit anything.

Anonymous 0 Comments

The CMB wasn’t created by the Big Bang directly. It was created about 380,000 years later. Before then the universe just full of hot dense plasma that was opaque to light.