Astronomers used the brightness of supernovae to estimate the distances to galaxies and the red-shift of their light to infer their recession speeds. The table shows the speeds predicted by the previously expected model in which the expansion of the universe was slowing down, and the speeds inferred from observations.
| Galaxy | Predicted recession speed (km/s) | Observed recession speed (km/s) |
|---|---|---|
| A | 12 000 | 13 200 |
| B | 18 000 | 20 100 |
| C | 24 000 | 27 500 |
Compare the observed recession speeds with the predicted speeds. Explain what the results suggest about the expansion of 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.