Physics 0625 · syllabus 6.1
Cambridge IGCSE Physics 0625 — The Earth and the Solar System topical past papers
Day and night, the seasons and the Moon's phases, the planets and smaller bodies of the Solar System and how it formed, gravity and orbits, and average orbital speed.
- Questions
- 206
- Years
- 2023–2026
- With mark scheme
- 100%
- Questions 2022–2026
- 206
Anyone can browse these pages. Opening the questions and their mark schemes takes a free Momentum account.
What The Earth and the Solar System covers
The Earth spins once on its tilted axis in about 24 hours, which gives day and night and makes the Sun appear to cross the sky from east to west. It orbits the Sun once in about 365 days, and because its axis is tilted, each hemisphere leans towards the Sun for part of the year and away from it for the rest, which gives the seasons. The Moon orbits the Earth in about a month, and as it does we see different amounts of its sunlit half: its phases. Extended candidates calculate an average orbital speed with v = 2πr/T, taking r as the mean radius of the orbit and T as the time one orbit takes.
The Solar System contains one star, the Sun; eight planets, in order Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune; smaller worlds, among them dwarf planets like Pluto and the rocky asteroids between Mars and Jupiter; moons orbiting the planets; and comets. The four inner planets are small and rocky, the four outer ones large and gaseous. An accretion model explains the difference: the Solar System formed from a rotating cloud of gas and dust containing many elements, gravity pulled the material into a spinning disc around the young Sun, and close to the hot Sun only rocky material could clump together, while further out gases could gather into giant planets.
The Sun contains most of the Solar System's mass, and its gravitational pull keeps the planets in orbit. A planet's surface gravitational field strength depends on its mass, and the field around any body weakens with distance. Light needs time to cross the Solar System — about 8 minutes from the Sun to the Earth — found from distance ÷ speed of light. Extended candidates also know that the orbits of planets, minor planets and comets are ellipses, with the Sun off-centre unless the orbit is nearly circular, that planets further out orbit more slowly, that a comet speeds up as it falls towards the Sun, gaining kinetic energy as it loses gravitational potential energy, and how to analyse tables of planetary data. Space physics was added to the syllabus for the 2023 examinations, so only papers from 2023 onwards examine it.
In the syllabus
The headings this topic has in the Cambridge International 2026–2028 syllabus, as the board prints them.
- 6.1 The Earth and the Solar System
What you should be able to do
- Explain day and night, the Sun's apparent daily motion, the seasons and the Moon's phases
- Use v = 2πr/T to find an average orbital speed (Extended)
- Name the planets in order from the Sun and describe the other bodies in the Solar System
- Use the accretion model to explain why the inner planets are rocky and the outer planets gaseous
- Calculate how long light takes to travel between bodies in the Solar System
- Interpret planetary data, and explain how orbital speed changes with distance from the Sun and around an elliptical orbit (Extended)
Key ideas
- The Earth spins on its tilted axis in about 24 hours and orbits the Sun in about 365 days; the Moon orbits the Earth in about a month
- Average orbital speed v = 2πr/T (Extended)
- A planet's surface gravitational field strength depends on its mass; the field weakens with distance from the planet
- The Sun's gravity keeps the planets in orbit; the Sun holds most of the Solar System's mass
- In an elliptical orbit a body moves fastest when it is nearest the Sun (Extended)
How The Earth and the Solar System has been examined
From 2022 to 2026, The Earth and the Solar System was on Paper 4 · Theory (Extended) in 11 of 14 exam series, worth about 10% of that paper’s marks.
| Paper | Questions | Share of marks | Series |
|---|---|---|---|
| Paper 1 · Multiple Choice (Core) | 72 | 6% | 11 of 14 |
| Paper 2 · Multiple Choice (Extended) | 76 | 6% | 11 of 14 |
| Paper 3 · Theory (Core) | 25 | 7% | 11 of 14 |
| Paper 4 · Theory (Extended) | 33 | 10% | 11 of 14 |
Momentum’s own count, over the questions in its bank for these years: a series is one exam session, every zone included, and a question filed under two chapters counts in both. Median marks per question: 1. The bank files this topic together with neighbouring ones, so these figures count every question in its chapters, including some on those topics.
Filed in Momentum under: Space Physics.
A worked example
Io, one of Jupiter's moons, orbits Jupiter at an average radius of 4.22 × 10⁸ m, taking 1.77 days for each orbit. Find Io's average orbital speed. When Jupiter is 6.3 × 10¹¹ m from the Earth, how long does sunlight reflected from Io take to reach us? (Speed of light = 3.0 × 10⁸ m/s)
- T = 1.77 × 24 × 3600 = 1.53 × 10⁵ s
- v = 2πr/T = 2π × (4.22 × 10⁸) / (1.53 × 10⁵) = 1.73 × 10⁴ m/s
- Time for the light = distance ÷ speed = (6.3 × 10¹¹) / (3.0 × 10⁸) = 2100 s, which is 35 minutes
- Check: 1.73 × 10⁴ m/s for 1.53 × 10⁵ s covers 2.65 × 10⁹ m, the circumference of the orbit, 2π × 4.22 × 10⁸ m
Answer: About 1.7 × 10⁴ m/s (17 km/s); the light takes about 2100 s, or 35 minutes
Written by Momentum for this page, with its own numbers; it is not taken from a past paper.
Mistakes that cost marks
- Explaining the seasons by the Earth's distance from the Sun — they are caused by the tilt of its axis, which is why the two hemispheres have opposite seasons at the same time
- Explaining the Moon's phases with the Earth's shadow — that is a lunar eclipse; the phases come from seeing different amounts of the Moon's sunlit half as it orbits
- Saying day and night happen because the Earth orbits the Sun — they come from the Earth's spin on its axis; the orbit gives the year
- Using a diameter, or a period in days, in v = 2πr/T — r is the radius, and for an answer in m/s it must be in metres with T in seconds
- Putting the Sun at the centre of an elliptical orbit — it is off-centre, so a planet's or a comet's distance from the Sun changes around the orbit
Exam technique
- In orbital-speed and light-time questions, convert days into seconds and kilometres into metres on lines of their own
- When reading planetary data, quote the figures you use and state the pattern, such as 'the further from the Sun, the longer the orbital period'
- For the accretion model, mention gravity, the cloud of gas and dust, its rotation and the disc that forms
Practising in Momentum
- Every question in a chapter as one list, from every paper and year in the bank, newest first or shuffled.
- Each question turns over to its own part of the mark scheme, where the board published one.
- Narrow by paper, year, session, zone and marks, and star the questions worth keeping.
- Pick chapters, a number of questions and a time, and the exam builder draws a mock to sit and mark.
Past-paper questions and mark schemes are the copyright of Cambridge International. Momentum shows them to signed-in learners for revision and does not publish them on these pages.