Earth and Its Moon

Earth is unique amongst the planets in our solar system. It is the only one with all the conditions needed for life to exist.

Earth is the only planet with a temperature that allows liquid water to exist. The other planets are either too close to the Sun or too far away. It is also the only planet to have an atmosphere that contains 21% oxygen which we need to breathe and 78% nitrogen. This atmosphere protects Earth from the Sun's ultraviolet rays. It also traps some of the Sun’s heat and transports

liquid around the planet in the form of rain.

Earth only has one satellite - the Moon. It is about one-quarter the size of Earth and has no water, wind, air or atmosphere. The Moon is held in orbit by Earth's gravity. On Earth, we only ever see the same side of the Moon. This is because the Moon takes the same time to spin on its axis as it does to orbit the Earth.

Although the Moon only has weak gravity, it is close enough to Earth to affect our oceans. It is the Moon that causes the rise and fall of our tides.