← nuclearjs Hydrogen burning s and r process
Big-Bang nucleosynthesis
In its first minutes the universe was a hot, expanding gas of photons, electrons, positrons, neutrinos and a trace of neutrons and protons. As it cooled, the weak interactions let go of the neutron-to-proton ratio, the neutrons began to decay, and the photons kept breaking every deuteron apart until it was cool enough for deuterons to survive. Then almost every neutron left ended in ⁴He, with traces of D, ³He and ⁷Li.