A cosmologist runs two computer models backwards from the present Universe.
| Model | Output when run backwards |
|---|---|
| K | The separation between galaxies decreases until the Universe reaches a very small, hot and dense state after a finite time. |
| L | The separation between galaxies decreases, but the model continues indefinitely with no starting point. Matter is removed as the model runs backwards, so the average density remains constant. |
The cosmologist considers two telescope measurements.
| Measurement | Result |
|---|---|
| G | Absorption lines from nearly all distant galaxies have longer wavelengths than the same lines measured in a laboratory. The increase in wavelength is greater for more distant galaxies. |
| M | Faint microwave radiation of almost the same intensity reaches the Earth from every direction in space. |
Before measurement M was made, Model K had been used to predict that radiation from the earliest stage of the Universe would have its wavelength stretched as the Universe expanded.
A student says, "Measurement M proves that Model K is correct, so measurement G is not useful."
Evaluate the student's statement. Identify the theory represented by each model and use both measurements in your answer.
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.