"Newton goes on to point out the consequence of denying the truth of this [third] law. For instance, if the attraction of any part of the earth, say a mountain, upon the remainder of the earth were greater or less than that of the remainder of the earth upon the mountain, there would be a residual force acting upon the system of the earth and the mountain as a whole, which would cause it to move off, with an ever increasing velocity, through infinite space."