Once the universe cooled enough for the electrons and nuclei to form atoms this changed.

If so, the universe will cool as it expands, eventually becoming too cold to sustain life.

As the universe cools, the quarks slow down.

When the galaxies had formed and the universe had cooled, Corona appeared much less frequently.

An expanding universe cools, just as a gas does.

When the universe cooled enough, protons and electrons combined to form neutral atoms.

As the universe grew and cooled, some of this energy transformed into matter.

As the universe expands and cools, it crosses transition temperatures at which forces separate from each other.

At that time, according to theory, space expanded and the universe cooled too rapidly for hydrogen to completely fuse into heavier elements.

Once the universe had cooled enough for atoms to form, the scattering was very much reduced (because atoms are neutral).