Earth and Space Science / Unit 10: Stars, Galaxies and the Universe
10.7 Evidence for the Big Bang
Notes
- Expansion and redshift of galaxies (Hubble).
- Cosmic microwave background (CMB): faint microwave glow from all directions, leftover from when the universe cooled enough (about 380,000 years old) for light to travel freely. Temperature is about 2.7 K.
- Abundance of light elements: about 75% hydrogen and 25% helium by mass, matching predictions.
- Observations of distant galaxies show the early universe looked different.
- Dark energy appears to be accelerating the expansion.
Practice
The cosmic microwave background is:
It is a key evidence for the Big Bang.
The observed ratio of hydrogen to helium in the universe, about 3 to 1 by mass, supports:
The Big Bang predicted that ratio.
Which is NOT evidence for the Big Bang?
Moon phases are unrelated.
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