Have you ever heard of optical illusions? That’s when things look differently from what they actually are. And that’s how the movie business began—a world of make-believe.
The thaumatrope is an optical toy made popular in 1826 by Dr. John A. Paris, a London physicist. Like all animation devices, the thaumatrope works on the principle of persistence of vision, which is the eye's ability to retain an image for a fraction of a second after the object is gone. In this case, the eye continues to see the two images on either side of the thaumatrope for a split second after each has appeared.
As the thaumatrope spins, it is perceived as one continuous image.