# Describe the Big Bang theory of the origin of the universe. In your answer, include what the universe was like at the start and how it has changed over time.

> AQA A-Level Physics (7408) — 3.9.3 Cosmology · Describe · 5 marks

## Mark scheme (5 marks)

1. The universe began from a very small / hot / dense initial state (singularity / single point)
2. The universe has been expanding since the Big Bang
3. The universe has been cooling as it expands
4. Cosmic microwave background (CMB) radiation is evidence for the Big Bang
5. The age of the universe is approximately 13.8 billion years / the universe is very old

## Key terms

- [Big Bang theory](https://www.gradenine.co.uk/glossary/big-bang-theory)

## Related

- [Revision notes for AQA A-Level Physics (7408)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-the-big-bang-theory-of-ec7df5df) · Published by Druglandscape Ltd.