An absorption line has a wavelength of 486 nm486\ \mathrm{nm}486 nm when measured in a laboratory.
An astronomy team measures the mean observed wavelength of this line for groups of galaxies at different distances.
| Galaxy group | Mean distance / million light-years | Mean observed wavelength / nm\mathrm{nm}nm |
|---|---|---|
| A | 120 | 490 |
| B | 360 | 498 |
| C | 600 | 506 |
Explain how the results support the conclusion that space is expanding.
The same line from another galaxy group is observed at 502 nm502\ \mathrm{nm}502 nm.
Use the results in the table to estimate the distance to this galaxy group.
The team also detects faint microwave radiation of almost the same intensity arriving from every direction in space.
Explain how this observation can distinguish between the Big Bang theory and the Steady State theory.
94 exam-style questions on Edexcel GCSE Physics 7.2 The Universe and red-shift, covering 7.2.1 Big Bang and Steady State theories, 7.2.2 Evidence for the Big Bang, 7.2.3 The Doppler effect and red-shift, 7.2.4 Red-shift as evidence for an expanding Universe, and 7.2.5 The CMB and the accepted model. Each one has a worked solution and a mark scheme showing where the marks go.