Dark Ages

Context

An article in Hindu about Dark Ages

The Epoch of Darkness: Setting the Stage

• Roughly 380,000 years after the Big Bang, the universe entered the cosmic dark ages, lasting until about 1 billion years later.
• This period was shrouded in darkness because the universe was filled with a thick fog of neutral hydrogen gas.
• This gas acted like a giant light sponge, absorbing most light emitted, leaving the universe essentially invisible and devoid of stars or galaxies.

Clues to the Unseen: Unveiling the Dark Ages

• While directly observing the dark ages is impossible, astronomers use other tools to understand this hidden era.
• The cosmic microwave background (CMB), a faint afterglow from the Big Bang, offers a snapshot of the universe at 380,000 years old.
• Studying the CMB reveals details about the early universe’s conditions, including the temperature and density of the neutral hydrogen fog.
• The large-scale structure of the universe, how galaxies cluster, provides further clues.
• The clustered distribution of galaxies suggests tiny density fluctuations existed even before the first stars formed.

The End of Darkness: The Dawn of a New Era

• The cosmic dark ages ended with the formation of the first stars and galaxies, marking a turning point.
• Light from these celestial bodies eventually reionized the neutral hydrogen gas, making the universe transparent once more.
• This period of reionization is estimated to have begun around 200 to 500 million years after the Big Bang.

While no astronomy was happening during the dark ages itself, it’s a crucial chapter in the universe’s history. Astronomers continue to unravel the secrets of this enigmatic period, piecing together the story of the cosmos’s hidden beginnings.