# The Big Bang Theory describes the origin of the Universe. State two pieces of observational evidence that support the Big Bang Theory and, for each piece of evidence, explain how it supports the theory.

> Cambridge International IGCSE Physics (0625) — 6.2 Stars and the Universe · State and Explain · 4 marks

## Mark scheme (4 marks)

1. Redshift is observed in light from distant galaxies (accept: light from distant galaxies has a longer observed wavelength than expected)
2. Redshift shows that galaxies are receding / moving away, indicating the Universe is expanding, consistent with originating from a single point (Big Bang)
3. Cosmic microwave background radiation (CMBR) is detected at all points in space
4. CMBR was predicted by the Big Bang Theory and its existence confirms that the Universe was once extremely hot and dense / originated from a very hot dense region

## Key terms

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

## Related

- [Revision notes for Cambridge International IGCSE Physics (0625)](https://www.gradenine.co.uk/learn)
- [How to answer "State and Explain" 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/the-big-bang-theory-describes-the-1117d79b) · Published by Druglandscape Ltd.