• STEAM Day Video


    Apparent Motion and Animation


    Do optical illusions trick your eyes or your brain? That is a question scientists were trying to answer for centuries. The answer is, it is a little bit of both since the eyes and the brain work together during the perception of vision. When you visually perceive an object, what is happening, put in the simplest way, is that the image of that object is projected onto the back of your eye and this information is sent to the brain, where it is processed and interpreted, forming the image that you see.


    Optical illusions are scientific, but also just plain fun! One optical illusion that has had a huge impact on our culture is the illusion of apparent motion . You perceive this illusion every time you watch cartoons or a movie. You perceive that the characters on the screen are moving around, but in fact you are seeing many still pictures flashing before your eyes! How does this work? Our brains are trying to make sense of what we are looking at, by, for example, making the motions in a cartoon look smooth. To do this it is thought that our brains put all of the pieces together and fill in blanks, or missing images, based on what we have already seen. Thus we have the illusion of objects moving. Our brains do this all the time, not just when we watch cartoons. For example, when someone blinks they do not see a brief black screen because their brain fills in an image that is an assumption of what they would see if their eyes were not closed. This phenomenon is called persistence of vision.


    Have you ever heard the phrase, "Seeing is believing"? Well, it is more accurate than you might think! In this science project, you can investigate the phenomenon of apparent motion by making your own

    • Flip-books are stacks of heavy-weight paper that are held together, such as with staples or binder clips. Each page in the stack has a slightly different variation of the image on the previous card. When you quickly thumb through the stack, your brain assembles the series of images into movement.
    • Thaumatropes (THAW-muh-tropes) are made by mounting two images on either side of a disc. Usually the two images go together, like a bird and a cage, or a fish and a bowl. When you rotate the disc, the images from the two sides come together into one image! Figure 1 below shows an example of a thaumatrope that uses an image of a cage on one side of the disc and an image of a mouse on the other side.