
The first few hundred thousand years are mysterious indeed. Nothing in our experience helps us understand that early universe.In our world things move back and forth through dimensions which are constant. Forward and back, left and right, up and down. (The exception is time. We cannot move back in time.) In the world we encounter, over vast distances, units of length are constant.
In the first millennia the Laws of Physics are stranger than anything we can imagine. Dimensions, mass and energy are very odd.
There was a spectacular event called the Cosmic Inflation during which the entire Universe dispersed over incredible distances in an instant. Another way of looking at this is that the notion of distance itself began, and when it did matter filled what we call space in a fraction of a second.
What we know as matter, composed of subatomic particles bound together, did not begin until late. As matter and energy diverged, the infinitesimal and the infinite came into being. It was strange indeed.
In time things cooled, and the great cycles began.