Around 4.6 million years ago, neither the Earth nor any of the other planets existed. There was just this vast, dark, very hot cloud of gas and dust swirling around the newly formed sun. Gradually, the cloud cooled and the gas began to condense into billions of droplets. Slowly these droplets were pulled together into clumps by their own gravity – and they carried on clumping until all the planets, including the Earth, were formed. But it took another half a billion years before the Earth had cooled enough to form a solid crust with an atmosphere around it.
Satellite measurements show it is 24,901 miles (40,075 km) around the equator and 7,297 miles (12,577 km) across. The diameter at the Poles is slightly less, by 26.7 miles (43 km).
The Earth is about 4.6 billion years old. The oldest rock is about 3.8 billion years old. Scientists have also dated meteorites that have fallen form space, and must have formed at the same time as the Earth.
The Earth has a core of iron and nickel, and a rocky crust made mostly of oxygen and silicon. In between is the soft, hot mantle of metal silicates, sulphides, and oxides.
The Earth is not quite a perfect sphere. Because it spins faster at the equator than at the Poles, the Earth bulges at the equator. Scientists describe Earth’s shape as “geoid”, which simply means Earth-shaped!
The Earth is the only planet with temperatures at which liquid can exist on the surface and is the only planet with an atmosphere containing oxygen. Water and oxygen are both needed for life.
Earth spins because there is nothing to stop it spinning. The Sun’s gravity keeps it in orbit.