Change in the value of 'g'

The value of g decreases with increase in the height above the earth. this means that the weight of a given mass , ie the pull of the earth on a certain mass, decreases as it attains height above the earth's atmosphere. As an object leaves the earth and travels towards the moon it reaches the point where the small pull the earth exert on it exactly equal to the pull by the moon. This point, where the rwo gravitational forces are equal and opposite , is called NEUTRAL or NULL POINT