# Explain why the red-shift observed from a galaxy that is twice as far away as another galaxy is expected to be greater.

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

> Scientists have found that the further away a galaxy is, the faster it appears to be moving away from us.

## Mark scheme (4 marks)

1. Red-shift is the stretching of wavelengths of light (towards longer/redder wavelengths) caused by a source moving away from the observer
2. A greater red-shift indicates the galaxy is moving away faster / at a greater speed
3. More distant galaxies are moving away from us faster (speed increases with distance)
4. Therefore the galaxy twice as far away is moving faster, so produces a greater red-shift / greater increase in wavelength

## 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/explain-why-the-red-shift-observed-from-66611a36) · Published by Druglandscape Ltd.