On 12/2/07, Patrick Mullen <[EMAIL PROTECTED]> wrote: > But there IS an upward force, at least as far as my memory of the > physics I learned. The whole every action has a reaction business. Right. Newton's third law. Pushing on a table should move it, if the force is unbalanced, but it doesn't, so the force is balanced by another force, thus action = reaction. > If the ground were mobile, that gravity force down would cause the > earth to move down with that same force. Since the earth can't move, > it pushes back with the force of gravity. But the Earth does move. If you drop a 1kg. ball from a height of one meter, then both objects (the ball and the Earth) accelerate towards each other. The reason we see the ball fall is because 1), we move with it, and 2) the Earth is more massive and so is accelerated very little by the force. (In fact, the Earth accelerates: (1 kg.)/(5.9736×1024 kg.) = .1674^ -1024th as much. Not even a trillion trillion trillionth of a millimeter. Still much smaller than even that. As soon as I get a minute, I'll do some more demos... > It has been quite a while since I was in physics, but that's how I remember > it. You remember much rightly. I'm currently in Physics.
Ian
