Then, as the universe expanded and cooled, the antiquarks would annihilate with the quarks, but since there would be more quarks than antiquarks, a small excess of quarks would remain.

As the universe expanded and cooled, the vacuum underwent a series of symmetry-breaking phase transitions.

As the universe expanded and cooled, it would have continued to resonate.

During this epoch, as the universe expanded and cooled after its explosive start, hydrogen atoms permeating the cosmos formed a thick fog that was opaque to ultraviolet light.

The temperature of the universe cooled and the things inside the universe began to clump together.

As the universe expanded and cooled, the clouds would begin to collapse of their own gravity.

As the universe expanded and cooled, symmetries in the laws of physics began breaking down in regions that spread at the speed of light; topological defects occur where different regions came into contact with each other.

It was then that the sound waves were humming through the young cosmos; astronomers believe the microwave background radiation was emitted as the universe cooled below a critical temperature when it was about 400,000 years old.

As the universe expanded and cooled, interactions became less energetic and when the universe was about 10 seconds old, W and Z bosons ceased to be created.

But as the universe expanded and cooled, large amounts of that gas remained wafting through space like a thick fog or haze, in the form of hydrogen atoms.