The Very Early Universe

At the time of nucleosynthesis, the primordial fireball consisted of electronsElectrons, protonsProtons, neutronsNeutrons, photonsPhotons and neutrinosNeutrinos. As we get closer to the big bang, the fireball gets hotter and denser, and other types of particles emerge. They move at nearly the speed of light, colliding frequently and violently. As we shall see, some of the most dramatic events in the history of the universe occurred within a small fraction of a second after the big bang.