* The sequence of planets starting from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
* The planets differ in size and distance from the Sun.
* The planets have very different conditions on their surface.
* The Sun is in the centre of the Solar System.
* The Sun is very big compared to the planets.
* All planets move round the Sun.
* The ratio of the size of the Moon to Earth and to the Sun is 1 : 4 : 400.
* The distance from Earth to the Sun is 400 times the distance from the Moon to Earth.
* Earth has water, air and suitable temperature to support life.
* If Earth is too near the Sun, it will be too hot to support life.
* If Earth is too far from the Sun, it will be too cool to support life.
* Earth is the only planet in the Solar System that has life on it.