dark age

In cosmology, the dark age is the time between recombination (when ions and electrons formed neutral hydrogen atoms, around 380,000 years after the Big Bang or a redshift of 1090) and the formation of stars and galaxies (around redshift 20, producing light), a point in time sometimes called the cosmic dawn. During the dark ages, atoms were neutral and space was transparent but without stars, all was relatively dark. The cosmic dawn was essentially the beginning of the epoch of reionization, the latter when ionizing radiation from stars again ionized hydrogen atoms in large numbers, 150 million years after the Big Bang, the ionization occurring from redshift 20 to redshift 6.