ABSTRACT
Immediately a er the Big Bang, the universe was extremely hot. At this stage, nuclear reactions were converting protons into neutrons and neutrons back into protons. At these high temperatures (~1011 K), there were an equal number of protons and neutrons. ese protons and neutrons were also continually combining to form deuterium (one proton and one neutron) and helium (two protons, two neutrons). However, at this stage, it was too hot for these elements to survive for very long.
