# A scientist observes that a galaxy 500 million light-years away shows a greater red-shift than a galaxy 100 million light-years away. Explain what this difference in red-shift tells us about the motion of these two galaxies.

> AQA GCSE Physics (8463) — 4.8.2 Red-shift (Phys only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Both galaxies are moving away from us / the Earth / our galaxy
2. Red-shift means the wavelength of light from the galaxy has increased / been stretched
3. A greater red-shift indicates a greater recessional speed / the more distant galaxy is moving away faster
4. More distant galaxies move away faster, showing that the universe is expanding

## Key terms

- [red-shift](https://www.gradenine.co.uk/glossary/red-shift)
- [galaxy](https://www.gradenine.co.uk/glossary/galaxy)

## Related

- [Revision notes for AQA GCSE Physics (8463)](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/a-scientist-observes-that-a-galaxy-e31870c8) · Published by Druglandscape Ltd.