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.

Click on any part for further details.

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.

Division of energy between photons and massive particlesExpansion time.
Particle population tableExample of energy and time calculation

Big Bang scenario

Weinberg, First Three Minutes
HyperPhysics***** Astrophysics R Nave
Go Back