Early Big Bang Processes

From the very beginning the universe had a very precise expansion rate that made possible the formation of galaxies and stars.

The universe is observed to be essentially "flat" in the sense that it is almost at the critical density at which it would expand forever. At that critical expansion rate it could form helium, whereas with a much faster rate only hydrogen would form. That rate also makes galaxies and stars possible, so that the heavier elements we are made from could be "cooked" in the nuclear fusion furnaces at the centers of stars. The universe retains the overall hydrogen-helium abundance from this early process.