# The Big Bang theory is the scientific model used to explain the origin and development of the universe. Describe the evidence that supports the Big Bang theory and explain how this evidence links to the theory.

> WJEC A-Level Physics (Wales) — 4.3 Orbits and the wider universe · Describe · 5 marks

## Mark scheme (5 marks)

1. The universe shows red-shift (light from distant galaxies is shifted towards longer/red wavelengths)
2. Red-shift indicates that galaxies are moving away from us / the universe is expanding
3. More distant galaxies show greater red-shift, meaning they are moving away faster
4. Cosmic Microwave Background (CMB) radiation is detected from all directions in space
5. CMB radiation is the remnant energy / afterglow from the initial hot, dense Big Bang event, supporting the idea the universe began from a single point

## Key terms

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

## Related

- [Revision notes for WJEC A-Level Physics (Wales)](https://www.gradenine.co.uk/learn)
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Source: [GradeNine](https://www.gradenine.co.uk/q/the-big-bang-theory-is-the-93efb243) · Published by Druglandscape Ltd.