# Explain how red-shift and cosmic microwave background radiation (CMBR) each provide evidence for the Big Bang Theory.

> OCR GCSE Physics A: Gateway Science (J249) — P6.3 Astronomy · Explain · 4 marks

> Astronomers studying light from distant galaxies notice that the wavelength of the light received is longer than expected. Separately, sensitive detectors pick up low-level microwave radiation arriving from all directions in space.

## Mark scheme (4 marks)

1. Red-shift shows that the wavelength of light from distant galaxies is increased / shifted towards the red end of the spectrum
2. Red-shift indicates galaxies are moving away from Earth / the universe is expanding, so it must have originated from a single point
3. CMBR is low-level microwave radiation detected in all directions throughout space
4. CMBR is the remnant high-energy radiation from the very hot early universe / Big Bang, whose wavelength has since increased / stretched as the universe expanded

## Key terms

- [red-shift](https://www.gradenine.co.uk/glossary/red-shift)
- [cosmic microwave background radiation (CMBR)](https://www.gradenine.co.uk/glossary/cosmic-microwave-background-radiation-cmbr)
- [Big Bang Theory](https://www.gradenine.co.uk/glossary/big-bang-theory)

## Related

- [Revision notes for OCR GCSE Physics A: Gateway Science (J249)](https://www.gradenine.co.uk/learn)
- [How to answer "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/explain-how-red-shift-and-cosmic-microwave-0c4a0640) · Published by Druglandscape Ltd.