Have you ever wondered why we have two eyes? In this project you will try using just one eye, and then see if two eyes are better than one. Ask a friend or family member to be your partner so they can learn about the science of seeing with you.
What You Need:
- A small cup or glass
- 5 pennies
- A friend to help you
- Paper and a pen or pencil
What You Do:
- Hold one penny in each hand, using your index finger and thumb. Stick your arms straight out in front of you, with your thumbs pointing towards each other.
- Close one eye. Slowly bring your hands together, and try to make the pennies touch edges with each other. Let your friend try it too, and see if the same thing happens.
- Try it again with the eye that was closed open and the other eye closed. You and your partner can both try several times, if you like.
- Try to make the coins' edges touch with both of your eyes open. Does the same thing happen when your friend does it? You can also try using two pencils instead of pennies, and try to make the erasers touch while having one eye closed.
- For the next part of the experiment you and your partner need to be sitting at a table across from each other. Put the cup about two feet away from your partner.
- Hold a penny with your index finger and thumb, and move it back and forth above the cup. Your hand should be about 18 inches (more than one foot) above the top of the cup.
- Tell your partner that you will keep moving your hand slowly back and forth, until they say stop, then you will drop the penny. Your partner's goal is for your hand to stop directly above the cup so the penny drops right in. Try it five times with your partner closing one eye. Try it again with your partner having both eyes open.
- Switch places with your partner, so you can have a turn trying to get the pennies in the cup. Be sure to keep one eye closed for the first five tries, then use both of your eyes for five more tries.
It was much harder to tell where the pennies were with one eye closed, wasn't it? We see differently with one eye than we do with two. Having both of our eyes open helps us see where things really are. Having both eyes open made it easier for your friend to judge when the penny was above the cup. We are used to having both eyes open, and so when we close one eye our brain is getting a different kind of picture of what things look like and gets confused. How many times was your partner able to get the penny into the cup with one eye closed? How many times did you do it? How many times did you and your partner get the penny in the cup with both eyes opened? Being able to tell where things really are is called depth perception. Depth means how deep something is, or where it is located. Perception means what you see. Sometimes what you see with your eyes, or your perception, can be different from what is really there!