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matter era (recombination era, decoupling era)
subject			fact

matter era	has duration > 1010 years
	has synonym recombination era
	has synonym decoupling era
	is preceded by radiation era
	has start time 1012 s
	has temperature 3 K to 3000 K
	has definition The Big Bang era when the temperature had dropped to 3000 K, at which time the recombination of hydrogen became possible. The plasma of free electrons and nuclei condensed to form a neutral gas. Matter and radiation consequently decouple from one another because no further scattering of the radiation occurs.
	has definition Separation of classes of particles from regular interaction with one another, as in the decoupling of photons from particles of matter that produced the cosmic background radiation.
	has definition The rapid transition from an ionized state at a redshift of 1000, when the blackbody radiation is scattered by the free electrons, to an unionized state, when the matter is predominantly in the form of hydrogen atoms that do not scatter the radiation appreciably. Radiation subsequently does not interact with matter unless the matter becomes reionized at a later epoch by radiation from quasars or forming galaxies.
	has definition The epoch at t ≈ 1013 s after the big bang (T ≈ 3000 K) when matter and radiation decoupled.
	has definition The era some 3 × 105 years after the Big Bang when the cosmic blackbody radiation was last scattered by the matter. At this era, at a redshift of about 1,000 and a temperature of about 3,000 K, the protons and electrons combined to form hydrogen atoms, which are effectively transparent to the radiation.
	has definition A cosmic epoch during which the matter content of the Universe ceased to be ionized. This led to a decrease in the optical depth of the Universe, and the photons of radiation (which we now observe as the cosmic microwave background) became able to travel large distances without interacting with matter.
	has definition The release of photons from constant collisions with massive particles as the universe expanded and its matter density diminished. See decoupling.
	is a kind of Big Bang era
Big Bang era	is followed by
event	has time of occurrence

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