Our earth is the third planet in the solar is the only planet where life is known to consists one and only one natural sattelite and we call it as ''moon".the the solar system there is no air and it has no when we see moon from the earth we see only half of it because the other half is behind it.the reason is in the solar system it is very dark and the moon is not able to give its own light, so it takes the light from the sun and reflects it back to the that is why we are not able to see the other side of the moon.