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.
370,000 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.
== See also ==
Timeline of the Big Bang
Big Bang
