The era some 380,000 years after the → Big Bang
(at a → redshift of about 1,100),
when the Universe had cooled sufficiently so that protons and electrons combined
to form → neutral hydrogen in a process called
→ recombination.
The temperature was about 3,000 K and the ionization fraction low enough for Universe
to become transparent to light. Consequently matter and radiation decouple from one
another because no further → scattering of the radiation occurs.
The observation of the
→ cosmic microwave background radiation provides
a means of studying the Universe at the recombination era.
Also called recombination epoch and
→ decoupling era.
See also: → recombination; → era.
