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Big Bang theory
Beginner
The universe began hot and dense 13.8 billion years ago.
The universe began about 13.8 billion years ago from a hot, dense state and has been expanding and cooling since. Supported by the CMB, light element abundances and the Hubble flow.
Not an explosion in space.
Doesn't describe t = 0 itself.
In more detail
The Big Bang theory describes the universe expanding from a hot, dense early state about 13.8 billion years ago. It explains the expansion, the cosmic microwave background and the abundance of light elements.
Real-world uses
- The Big Bang model is the framework for modern cosmology.
- It explains observational evidence such as the CMB and Hubble's law.
- Astronomers date the universe to about 13.8 billion years using the cosmic microwave background and the expansion rate.
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Frequently asked questions
Did the Big Bang happen at a point in space?
No, it describes the expansion of space everywhere, not an explosion in existing space.
How old is the universe?
About 13.8 billion years, measured from the CMB and expansion rate.
Did the Big Bang happen in a place?
It happened everywhere at once, filling all of space, rather than at a single point in an existing space.
Related topics in Particle Physics & Cosmology
Milky Way · Hubble's law · Expansion of the universe · Cosmic microwave background · Big Bang nucleosynthesis · Inflation