The Earth
The Earth is the third planet from the Sun. It is the largest of the four rocky planets. It is also the only place in the Universe where we know there is life.
The Earth's has an atmosphere. We call it 'the air'. Earth's atmosphere is mostly made of the gases, nitrogen (78%) and oxygen (21%). It also contains tiny amounts of water vapour and carbon dioxide.
About 70% of Earth's surface is liquid water. This creates large oceans and seas. The rest is continents and islands. The areas near the north and south poles of the Earth are mostly covered with ice.