BRAINCAKEThe Big Bang Theory and the Age of the Universe
The Big Bang theory states that the universe began about 14 billion years ago from an extremely hot, dense state and has been expanding and cooling ever since. Space itself expanded; there was no centre and no pre-existing space for it to expand into.
Evidence for the Big Bang:
• Hubble's law: galaxies are receding with speeds proportional to distance, so they were once much closer together.
• Cosmic microwave background radiation (CMB): microwave radiation reaching us almost equally from all directions, with a black-body spectrum at about 2.7 K. It is radiation from the hot early universe, stretched to microwave wavelengths by the expansion.
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More in Astrophysics
- Evolution of a Star
- Supernovae, Neutron Stars and Black Holes
- The Schwarzschild Radius
- Type Ia Supernovae as Standard Candles
- The Doppler Effect and Red Shift
- Hubble's Law
- Quasars
- Detecting Exoplanets
All 24 lessons in Astrophysics · All AQA A-level Physics topics