Cosmic Dark Ages
The Cosmic Dark Ages of the universe began around 370,000 years after the Big Bang and lasted hundreds of millions of years. During this period, the temperature of the universe cooled from about 4000 K to about 60 K, and only two sources of photons existed: the photons released during recombination/decoupling (as neutral hydrogen atoms formed), which we can still detect today as the cosmic microwave background, and photons occasionally released by neutral hydrogen atoms, known as the 21 cm spin line of neutral hydrogen.
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Type:🔵 Tags: Astronomy / Physics / Astrophysics Status:⛅️