The Earth is the only planet in the Solar System that has an atmosphere containing appreciable amounts of oxygen to support life. It also has a surface with rivers, lakes and oceans and the ability to support a huge range of living things such as plants and animals. 5,000 million years ago the Earth did not exist, it was simply a spinning cloud of gas and dust. Over millions of years, the gas clumped together, cooled and formed a planet. The atmosphere formed and over time, plants and animals evolved. It is thought that the Earth has a dense core of molten iron, with a temperature of 4,000oC, a less dense mantle with temperatures between 1500 and 4,000oC and then a crust that is about 50km thick. The Earth spins on its own axis once every day, orbits the Sun once a year and has a satellite in orbit around it called the Moon.
