# The Big Bang theory is the currently accepted model for the origin of the universe. Describe the two pieces of evidence that support the Big Bang theory, explaining in each case how the evidence supports the theory.

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

## Mark scheme (4 marks)

1. Red-shift: light from distant galaxies has an increased (observed) wavelength / galaxies are moving away from us
2. Red-shift shows the universe is expanding (from a single point), consistent with a Big Bang origin
3. Cosmic microwave background radiation (CMBR) is detected in all directions across the sky
4. CMBR is the stretched (longer wavelength) remnant of the high-energy short-wavelength radiation released by the Big Bang as the universe expanded

## Key terms

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

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Source: [GradeNine](https://www.gradenine.co.uk/q/the-big-bang-theory-is-the-186e1868) · Published by Druglandscape Ltd.