# A scientist observes two distant galaxies, Galaxy P and Galaxy Q. Galaxy P is twice as far from Earth as Galaxy Q. Compare the red-shift of light from Galaxy P with that from Galaxy Q, and explain what this tells us about the motion of the two galaxies.

> Pearson Edexcel International GCSE Physics (4PH1) — 8.3 Cosmology · Compare · 4 marks

## Mark scheme (4 marks)

1. Galaxy P shows a greater red-shift than Galaxy Q
2. Both galaxies are moving away from Earth / the observer
3. Galaxy P is moving faster / at a greater speed than Galaxy Q
4. The greater the distance of a galaxy, the faster it moves away / this supports the Big Bang theory / 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 Pearson Edexcel International GCSE Physics (4PH1)](https://www.gradenine.co.uk/learn)
- [How to answer "Compare" 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-two-distant-galaxies-ce6b0b02) · Published by Druglandscape Ltd.