The Photon Epoch? New to this tour in physics? Start at THE BIG BANG.
“Between 10 seconds and 380,000 years after the Big Bang.
A photon is an elementary particle, the quantum of light and all other forms of electromagnetic radiation, and the force carrier for the electromagnetic force.
In physical cosmology, the photon epoch was the period in the evolution of the early universe in which photons dominated the energy of the universe.
The photon epoch started after most leptons and anti-leptons were annihilated at the end of the lepton epoch, about 10 seconds after the Big Bang.
Atomic nuclei were created in the process of nucleosynthesis which occurred during the first few minutes of the photon epoch.
For the remainder of the photon epoch the universe contained a hot dense plasma of nuclei, electrons and photons.
About 380,000 years after the Big Bang the temperature of the universe fell to the point where nuclei could combine with electrons to create neutral atoms.
As a result, photons no longer interacted frequently with matter, the universe became transparent and the cosmic microwave background radiation was created and then structure formation took place.”
Next lecture NUCLEOSYNTHESIS.