The Zoetrope was invented in the mid-1800’s, long before the development of the movie camera and animated cartoons, as a way of deriving motion from still pictures. Look through the slits at the drawings and turn the crank at the side of the exhibit as fast as you can. Turn the crank the other way and notice that the balls roll in the opposite direction. As the cylinder rotates, you see a fragment of the picture on the far side of the cylinder. When the next slit passes your eye it reveals a slightly different part of the picture. Each image lingers in your eye and brain long enough to merge with the next image. This phenomenon, called persistence of vision, creates the illusion of a continuously moving picture.