Why Moon?

Answer 1

Are you asking 'why does earth have a moon'? There are several theories as to how the Moon was formed, but the prevalent one is called the 'giant impact' theory. What this says is that in the early days of the Earth's existence about 4.6 billion years ago, when it was mostly composed of molten rock and lava, another planetary body referred to by astronomers as Theia (that was about the same size as Mars) collided with the earth. This caused the destruction of Theia as well as a massive ejection of the Earth's composite matter out into space, some of it escaping into the void as dust particles but much of it remaining to gradually coalesce and clump together to form the solid natural satellite that we now know as the moon.

Other theories suggest that the Moon may have originally been a very large asteroid which was 'captured' into the Earth's orbit and has remained there ever since- this is certainly thought to be what happened with Mars's two moons, Phobos and Deimos. But one thing is certain though- the Moon is as essential to life on Earth as the Sun. The effect of it's orbit around the Earth is responsible for the ocean tides, for winds, and also for alterations and fluctuations in our own body chemistry- chronobiologists, who study 'body clocks', have much to say about the influence that the moon has upon the regular variations within our own biochemistry.