# Explain why the Big Bang Theory is the currently accepted model for the origin of the universe, whilst the Steady State Theory has been rejected.

> Edexcel GCSE Physics (1PH0) — 7.1 Astronomy (Phys only) · Explain · 4 marks

## Mark scheme (4 marks)

1. Red-shift shows that distant galaxies are moving away from Earth / the universe is expanding
2. An expanding universe means it must have originated from a single point, supporting the Big Bang Theory
3. Cosmic microwave background radiation (CMBR) is detected in all directions and supports the Big Bang Theory
4. The Steady State Theory cannot explain CMBR / is rejected because it does not account for CMBR

## Key terms

- [Big Bang Theory](https://www.gradenine.co.uk/glossary/big-bang-theory)
- [Steady State Theory](https://www.gradenine.co.uk/glossary/steady-state-theory)

## Related

- [Revision notes for Edexcel GCSE Physics (1PH0)](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-big-bang-theory-4e50efc9) · Published by Druglandscape Ltd.