Astronomers notice that measurements of Uranus's position do not agree with an existing model of the Solar System.
Model P includes only the planets already known to the astronomers. Model Q also includes the gravitational effect of an additional planet.
The table compares the angular position of Uranus predicted by each model with its measured position. Each angle is measured from the same reference direction.
| Year | Position predicted by Model P in degrees | Position predicted by Model Q in degrees | Measured position in degrees |
|---|---|---|---|
| 1 | 82.0 | 81.4 | 81.5 |
| 2 | 86.1 | 85.2 | 85.1 |
| 3 | 90.2 | 89.0 | 89.1 |
A scientist claims, ‘Model Q should replace Model P immediately.’
Evaluate this claim.
80 exam-style questions on Edexcel GCSE Physics 7.1 The Solar System and gravity, covering 7.1.1 Weight and g on different bodies in space, 7.1.2 The Solar System, 7.1.3 Changing ideas about the Solar System, 7.1.4 Orbits of moons, planets, comets and satellites, and 7.1.5 Gravity and orbital motion. Each one has a worked solution and a mark scheme showing where the marks go.