Therefore, the southern edge is being carried eastward by the earth's rotation faster than the northern edge. Hence the dial must twist around continually like a 'postage stamp fastened to a rotating globe. This twisting is in a counterclockwise direction in the northern hemisphere, making the plane of vibration of the pendulum appear to deviate in a clockwise direction. So much for the theory of the experiment. Let us turn now to a description of this particular pendulum and the method of keeping it swinging.
Some people have the idea that the rotation of the earth causes the pendulum to swing.
That is not true. When our Hall of Science is closed, the pendulum is not moving. Just before the building is opened, the pendulum is started by moving the ball to one side and letting it swing back and forth. The pendulum seems to keep swinging without any help. This leads some people to believe that this is perpetual motion.