Learn about the way your eyes and brain work together to help you see, and discover why you have two eyes.
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.
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!
You know that your eyes are what you see with. But how do they work, and what are the different parts of your eye? Take a closer look at your eyes with this science project.
Your eye has many parts. Some of them are on the outside, and so you can see them, and some of them are inside your eye where you cannot see them. Eye color (blue, brown, green) happens because of our iris. The magnifying glass you used helped you see close up. Our eyes sometimes need help - glasses or a magnifying glass can help us see better.
Our eyes are able to tell the difference between light and dark. After picking out where the light is, our eyes send a picture to our brain, which is how we see. Have you ever looked closely at something and noticed that what you are looking at gets clearer, or more in focus? The part of our eye that focuses on something is called a lens. Eyeglasses have lenses, and a magnifying glass is a large lens. The lens of our eye is right behind the pupil (dark center) and iris (colored part of your eye). The iris controls the size of your pupil, and the pupil is the part of the eye that lets light in. The lens focuses the light, where it reaches the back of the eye, called the retina. The retina is the "camera" of the eye - it takes all the information being taken in by your eyes, and makes it into a picture. The retina is connected to your optic nerve, which connects your eyes to your brain. From the retina, information travels very quickly to your brain, which processes it, so that you see.
We don't have to think about seeing - we just see. As soon as our eyes pick up light, they send that information along the optic nerve, where it is received by the brain, and creates a picture for you to see. Imagine you and your friend are trying to draw a picture. You are blindfolded, so only your friend can see. But your friend can't move his or her hands. What would you do? If your friend told you where to move the pencil, you would be able to draw! The way we see is similar. The eyes are getting all of the information - like your friend who can see the pencil and paper while you can't. But our eyes can't do anything with this information, so they send it on to the brain. The way our eyes and brain communicate in order to see is sort of like how your friend told you where to move the pencil, only it happens very quickly - so quickly we don't even notice it!
How are human eyes different from animal eyes? Well, some animals have eyes that work very similarly to ours. Dogs take in light with their pupil and iris the same way we do, but their retina is different than ours. Dogs can see fewer colors than we can. Insects have very special eyes called compound eyes. Insect eyes are made up of lots of tiny lenses rather than one large lens. This lets them see in many directions at once! Another animal that has unique vision is the owl. Owls cannot move their eyes up and down and side to side like we can. Instead, their necks are very flexible, and they can rotate their heads almost in a full circle! Animals have eyes of many different sizes. The ostrich has very large eyes - in fact, their eyes are bigger than their brains!
Our eyes are very important! To protect our vision there are a few things we should always do. When you are out in the sun, you protect your skin by wearing sunscreen. The way to protect your eyes from the sun is by wearing sunglasses. Even with sunglasses, you should never look directly at the sun! The sun is so bright that it can hurt our eyes when we look right at it. Sharp objects can also hurt or damage our eyes. When you carry sharp objects such as scissors, keep them closed by holding the point in the palm of your hand, and walk - do not run. The other important thing that you can do to protect your eyes is to wear the right equipment when you play sports. If you are skiing, wear ski goggles and a helmet. Wearing a bike helmet also protects your head, and keeps your eyes safe. If you play baseball, it's a good idea to wear protective glasses. Because our eyes are so important, we need to work hard at keeping them safe.