Third part of BIG BANG Timeline
Cooling The universe continued to decrease in density and fall in temperature, hence the typical energy of each particle was decreasing. Symmetry breaking phase transitions put the fundamental forces of physics and the parameters of elementary particles into their present form. After about 10 −11 seconds, the picture becomes less speculative, since particle energies drop to values that can be attained in particle accelerators . At about 10 −6 seconds, quarks and gluons combined to form baryons such as protons and neutrons. The small excess of quarks over antiquarks led to a small excess of baryons over antibaryons . The temperature was now no longer high enough to create new proton–antiproton pairs (similarly for neutrons–antineutrons ), so a mass annihilation immediately followed, leaving just one in 10 10 of the original protons and neutrons, and none of their antiparticles. A similar process happ...