Earth

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The Earth is the only planet with life in the solar system. This is most likely because of the moderate temperatures, and the existence of water. The atmosphere of the earth was been transformed several times by the presence of lifeforms. Now it contains 21% oxygen.

Earth has a diameter of around 12,750 km, because of Earth rotation the equator is around 43 km thicker than the poles. Earth has an outer silicate solid shell, a liquid mantle, a fluxional outer core with less viscosity than the mantle, and a solid inner kernel. Temperatures inside Earth reach around 6000°K.

71% of Earths surface is covered with water. But only 2.5% of that is freshwater, the rest are oceans and seas.

The Moon

The Earth has a satellite, the Moon. Actually the Moon has many attributes like the other planets, but no atmosphere and no iron core. The Moons gravity causes tides and has effects on the weather on Earth.

The Moon is around 3,500 km thick. It is in synchronous rotation, keeping nearly the same face pointing to Earth at all times.

The Moon sometimes is called "Luna" from the Latin Word for Moon.

3753 Cruithne is a near Earth asteroid with an orbit around the sun very close to the Earth, so that it is sometimes referred as a second moon, but that is technically not correct. It is only about 5 km thick.