How we see depends primarily on physiology. While there are differences in the way people and cows see, the basic structures are the same for both. Light reflects off objects around us and leaks into the brain through the pupil in the eye. The light then triggers a chemical reaction that sends electrical impulses to the visual cortex. You can learn all about this process by watching the full cow's eye dissection .

The Zoetrope was invented in the mid-19th century. With a Zoetrope, a series of slightly different pictures revolve inside a spinning drum. To view the motion, you must look through slots. What you brain "sees" is one picture, then a slightly different picture. It has the same effect at the flip stick: Your brain "fills in" the missing motion. Learn more about how we built our Zoetrope .