How do astronomers hear the Big Bang in the sky?
Quick Answer
They study the cosmic microwave background, the afterglow of the early universe. It is a faint microwave signal that fills all of space and dates from about 380,000 years after the Big Bang.
The Full Story
The cosmic microwave background, or CMB, is radiation left over from when the universe first became transparent. Before then, the universe was a hot plasma that scattered light constantly; after electrons and nuclei formed neutral atoms, light could travel freely. The CMB is now cooled by expansion to about 2.7 kelvin. Measurements of tiny temperature variations in the CMB give clues about the universe’s age, composition, and geometry.
Key Facts
YouTube Angle
Suggested video title for this topic:
"The universe still has a baby picture."
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