The Solar System and Gravity
- Earth & Space
- Ages 11–14 · Grades 6–8
What you’ll find out
- The Solar System is the Sun and everything held in orbit around it: planets, moons, dwarf planets, asteroids and comets.
- Inner planets are small and rocky; outer planets are giants of gas and ice.
- Gravity depends on mass and distance, bends moving planets into orbits, and formed the Solar System.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
The Sun’s family
The Solar System is made up of the Sun and everything that orbits it. There are eight planets. The four inner planets, Mercury, Venus, Earth and Mars, are small and rocky. The four outer planets, Jupiter, Saturn, Uranus and Neptune, are giants made mostly of gas and ice. Between Mars and Jupiter lies a belt of rocky asteroids, and far beyond Neptune are dwarf planets such as Pluto and countless icy comets. The Sun holds more than 99 per cent of the Solar System’s mass.
Gravity holds it together
Gravity is a force of attraction between any two objects that have mass. The more massive an object, the stronger its pull, and the pull weakens with distance. The Sun is so massive that its gravity keeps all the planets in orbit. Each planet is moving very fast; without gravity it would travel off in a straight line. Instead, the Sun’s pull continually bends its path into a curved orbit. Gravity also holds moons around planets and keeps our feet on the ground.
Curriculum links: NGSS MS-ESS1-2 · NGSS MS-ESS1-3 · England KS3: Space physics · Cambridge Lower Secondary Stages 7–9: Earth and space · NCERT Science, Classes 6–8