# Explain how observations of red-shift from distant galaxies provide evidence for the Big Bang theory.

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

> Astronomers observe that the light reaching Earth from distant galaxies has a longer wavelength than the same light produced in a laboratory on Earth. Galaxies that are further away show a greater increase in wavelength than those that are closer.

## Mark scheme (4 marks)

1. Red-shift means the wavelength of light from distant galaxies is increased / longer than expected
2. Red-shift shows that galaxies are moving away from us / Earth (due to the Doppler effect)
3. The further the galaxy, the greater the red-shift / the faster it is moving away
4. This pattern is consistent with the universe expanding from a single point / supports the Big Bang theory

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/explain-how-observations-of-red-shift-from-c72c8b11) · Published by Druglandscape Ltd.