Dark age

A dark age is a period of severe decline within a civilization. Dark ages are usually caused by famine, pestilence, war, or some combination of problems.

A dark age can also be a period where the sources are sparse and little is known.

See also: Dark Ages

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In cosmology, the Dark Age is the period between recombination (when the universe became transparent to radiation) and reionization (when the first stars formed). During this time, the universe was filled with a cooling neutral gas and photons.