Question

why does light we see today tell us something what happened earlier in the history of the univer?

Answer 1

This was the moment of first light in the universe, between 240,000 and 300,000 years after the Big Bang, known as the Era of Recombination. The first time that photons could rest for a second, attached as electrons to atoms. It was at this point that the universe went from being totally opaque, to transparent.

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