In this activity, you use the power of science to create the illusion of seeing though your hand. Its really binocular vision, but your friends don’t know that.
Here’s What You Need
- A cardboard paper towel tube or toilet paper tube (you can also use a rolled-up sheet of paper)
- A hand
Here’s What You Do
Grab the cardboard tube and hold it up to your eye (like you were looking through a telescope). Now, place your free hand next to the tube with the palm open and facing you (it should be touching the side of the tube). Keep both eyes open and slowly move your free hand back and forth along the side of tube. With one eye look through the tube and with the other at your hand. After a while, you should perceive what appears to be a large hole through your hand. Pretty cool, huh?
The Science Behind the Hole in Your Hand
Similar to other primates, our brains are designed to work with binocular vision. The word binocular comes from the Latin words bini (meaning double) and oculus (meaning eye). In other words, our brain knows how to utilize information it receives from two eyes. For example, when most people look at an object, they are seeing it with two eyes and consequently, from two slightly different perspectives. When these two signals reach the brain, they are merged into one image. The brain also assumes that the picture from each eye is of the same thing. The Hole-in-the-Hand demonstration illustrates this. In the activity, the two eyes see very different things. However, the brain merges the two images into one and gives the illusion that there is a hole in your hand.
Binocular vision has some other great benefits. For example, organism with two eyes will still have the ability to see if one eye is damaged. Binocular vision also helps us to judge distances accurately. Here’s a little experiment for you to try. Place an eye patch or blindfold over one of your eyes. Now, grab a buddy and a ball and head outside for a friendly game of catch. Try catching and throwing the ball with one eye. Do you notice anything? Is it harder or easier? Try shooting baskets or hitting a baseball. You will quickly realize that having two eyes definitely comes in hand-y!
