I am trying to grasp the concept of cosmic background radiation, specifically why we can still see it today. As the name implies, it is very faint radiation from the very early universe.
What I don’t get: if a very distant star stops emitting radiation then it will disappear from our view.
As far as I understand it, CBR originated with the recombination. That phase took a few hundred thousand years, then it stopped. So why can we still see the photons emitted then?
Thanks for illuminating me.
In: 6
The radiation emitted from that early stage of the universe spread out and is just now after billions of years reaching us. That’s why the term light-year is a thing. It describes how far light travels in a year. The star Sirius is like 8 light-years away from us so the light needs 8 years to reach us. The CMB or CBR is Billion’s of light-years away from us. The further we look into the Universe, the further we also look back in time.
What we see so far out is loong gone, but the light isn’t.
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