A research team surveys 300 galaxies and places them into three groups according to their distance from the Earth. Each group contains 100 galaxies.
The table shows the results.
| Distance from the Earth in millions of light years | Number with a spectral pattern shifted to longer wavelengths | Mean increase in wavelength for these galaxies in % |
|---|---|---|
| 20–80 | 78 | 0.4 |
| 200–400 | 96 | 2.1 |
| 800–1200 | 99 | 7.2 |
A scientist makes this claim:
‘Galaxies are simply moving in random directions. The results do not support the idea that space itself is expanding.’
Evaluate the scientist’s claim. Use the data to explain what they suggest about the motion of the galaxies and about the universe.
79 exam-style questions on AQA GCSE Physics 8.2 Red-shift, covering 8.2 Red-shift. Each one has a worked solution and a mark scheme showing where the marks go.