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Overview
Big Bang cosmology holds that the universe has expanded from an extremely hot, dense early state and has been cooling ever since. Current measurements put the age of the universe at about 13.8 billion years. The theory is supported by the observed expansion of space, the relative abundance of light elements and the faint afterglow known as the cosmic microwave background. It changed the universe from an eternal backdrop into an object with a history.
Context
Until the 1920s many scientists, Einstein among them, assumed the universe was static and eternal, and the Milky Way was thought to be much of what existed. Einstein's general relativity of 1915 allowed expanding or contracting solutions, but he initially added a term to keep the universe static. Observational astronomy was also changing, with larger telescopes in the United States.
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Curator's notes
- Why it matters
- The universe had a beginning about 13.8 billion years ago
- What to read
- Hawking, A Brief History of Time
- Breakthrough
- Big Bang cosmology
- Who (date)
- Lemaitre, Hubble (1927 – 29)
- What it changed
- The universe had a beginning about 13.8 billion years ago
- Accessible reading
- Hawking, A Brief History of Time
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