Objects that are free to move "fall" towards the center of the Earth because of
the gravitational forces that attract the Earth and the object toward each other.
An object on or near the surface of the Earth that has only the force of gravity
and no other forces acting on it accelerates steadily toward the center of the
Earth at the rate of 9.81 meters per second every second.
At the same time, of course, the Earth accelerates toward the object, although
at a considerably lower rate.
