A small planet within a vast Solar System the Earth is unique in several ways. It has life it has water and it has a surface that is continually being renewed. The parts of the Earth that can be seen are just a tiny proportion of the whole planet. Beneath the Earth's crust lies the thick rocky mantel and at the centre there is a metal core which is partly solid and partly liquid. A magnetic field protects the Earth from the Sun's harmful radiation. Over three-quarters of the Earth's surface is covered by water. Of all the rain that falls on the land one-third runs off into rivers and returns to the sea. The rest soaks into the soil where it remains for years as ground water which keeps rivers flowing in times of drought. Featuring historic scientific apparatus and ground-breaking experiments Earth is an intriguing look at the world in which we live.