A Particle Soup - 10 -12 to 10 Seconds
After inflation, and the collapse of the inflaton field, at around 10-12 seconds, the Electromagnetic and Weak Nuclear forces separate, so we now have our four familiar, separate forces in play. The temperature has fallen to about 1016ºK.
Quark Epoch - 10 -12 to 10 -6 Seconds
Astronomy & Cosmology -
The Early Universe
(or "What Banged in the Big Bang?")
After the annihilation of proton/anti-proton pairs, the mass of the Universe is concentrated in the leptons. The temperature remains high enough for the production of lepton/anti-lepton pairs. After ten seconds, known as the Lepton epoch, when the temperature falls to "only" a billion degrees, a similar annihilation process, called Leptogenesis, occurs for electrons and positrons, resulting in about the same number of electrons as protons.
The Universe is now a hot, particle soup of photons, quarks, electrons, and neutrinos. This is known as the Quark epoch, and lasts for about a millionth of a second. The Universe has grown to about the same size as our solar system is today; perhaps 12 billion km (7.5 billion miles) across.
Hadron Epoch - 10 -6 to 1 Seconds
Over another second or so, known as the Hadron epoch, the temperature drops enough to permit quarks to combine to form protons and anti-protons. For reasons not yet understood fully, there was an imbalance between protons and anti-protons at the end of the Hadron epoch resulting in 1,000,000,001 protons for every 1,000,000,000 anti-protons. Thus, when they annihilate, the result is 1,000,000,000 photons and one solitary proton; this process is known as Baryogenesis. After the annihilation, for about every seven protons there is one neutron. In addition, during this highly energetic phase, another type of hadron appears; that is Mesons. Mesons comprise a quark/anti-quark pair. In May 2010, analysis of results from the Tevatron seem to imply that nature may prefer matter to anti-matter. Scientists there discovered a 1 percent difference between the number of pairs of muons and anti-muons resulting from the decay of B mesons. B Mesons comprise an up, down, charm or strange quark combined with a bottom anti-quark. More evidence is needed before this can be confirmed.
By the end of this epoch, the temperature has dropped to around 1010K and neutrinos no longer interact with matter, so they decouple and start to move freely through the Universe as they do to this day.
Lepton Epoch - 1 to 10 Seconds