The solar system contains planets, their satellites, asteroids and comets. The planets orbit the Sun and take different amounts of time to do this.
We have night and day on Earth because the Earth spins on its axis. The tilt of the Earth's axis causes the seasons to change as we orbit the Sun in one Earth year.
This Revision Bite covers:
BBC © 2012 The BBC is not responsible for the content of external sites. Read more.
This page is best viewed in an up-to-date web browser with style sheets (CSS) enabled. While you will be able to view the content of this page in your current browser, you will not be able to get the full visual experience. Please consider upgrading your browser software or enabling style sheets (CSS) if you are able to do so.