# Explain why scientists believe the universe began with a Big Bang. Your answer should refer to evidence from the motion of distant galaxies and the nature of background radiation detected throughout space.

> Eduqas GCSE Physics — 2.6 Particle physics and using physics to investigate the universe · Explain · 4 marks

> Astronomers observe that light from distant galaxies is shifted towards the red end of the spectrum. Scientists have also detected a faint microwave radiation coming from all directions in space.

## Mark scheme (4 marks)

1. Light from distant galaxies is red-shifted, meaning the wavelength of light is stretched/increased
2. Red-shift shows that distant galaxies are moving away from us, indicating the universe is expanding
3. Cosmic microwave background (CMB) radiation is detected uniformly from all directions in space
4. CMB radiation is the remnant energy/heat from the Big Bang, supporting the idea that the universe started from a single, very hot, dense point

## Key terms

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

## Related

- [Revision notes for Eduqas GCSE Physics](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-scientists-believe-the-universe-115e3967) · Published by Druglandscape Ltd.