Astronomers test two models using the same observations of planetary positions.
| model | description | number of epicycles used | mean difference between predicted and observed position |
|---|---|---|---|
| A | the Earth is fixed at the centre | 28 | 1.2° |
| B | the planets orbit the Sun on slightly elliptical paths | 0 | 0.2° |
A student says that these data show that every object in the Solar System orbits the Sun directly.
Evaluate which model is better supported by the data and whether the student's conclusion is justified.
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.