After the big bang, the main agenda of the cosmos was expansion, ever diluting the concentration of energy that filled space. With each passing moment the universe got a little bit bigger, a little bit cooler, and a little bit dimmer. Meanwhile, matter and energy co-inhabited a kind of opaque soup, in which freerange electrons continually scattered photons every which way.

After the big bang, the main agenda of the cosmos was expansion, ever diluting
the concentration of energy that filled space. With each passing moment the
universe got a little bit bigger, a little bit cooler, and a little bit dimmer.
Meanwhile, matter and energy co-inhabited a kind of opaque soup, in which freerange
electrons continually scattered photons every which way.