Why do we have 2 eyes

Why do you have two eyes?

People have many parts of the body twice: arms, legs, ears, eyes and much more. There is usually a good reason that this is the case. We couldn't walk on one leg, carry things poorly with only one arm, and with only one ear we couldn't locate the direction from which a sound was coming. And with only one eye? What would happen then, you can try out here.

You take:

  • pen
  • Washer through which the pin must fit
  • Modeling clay
  • eye patch

Put the washer upright in the modeling clay so that you can easily push the pin through the hole. The modeling clay is only there to help you hold the washer better. Now put on the eye patch or cover your eye. Do not cheat! Hold the plasticine and washer away from you with your arms outstretched and try to push the pin through the washer. You probably won't be able to do this right away. Why is that?

No fear! Everything is fine with your eyes. However, it is difficult to do certain things without a second eye. Both eyes work together wherever distances have to be assessed. They enable spatial vision. Each eye reports a slightly different image to the brain. In the brain, these two images are put together to form a single, spatial image - namely, what you see. You can gauge how far away the table is so that you don't bump into it.
You know where to grab the glass so you don't throw it down, and you also know where to put the pen through the washer. With only one eye you are usually wrong when estimating distances.

You can easily check for yourself that each eye delivers a different picture to the brain. Hold one thumb up with an outstretched arm and fix it with one eye. Close the other. Make a note of what can be seen behind the thumb (e.g. a flower vase, a tree, a picture on the wall ...). Now alternately look at the thumb with the left and the right eye.

Always close the other. Even if you keep your thumb very still: you will see that the background jumps back and forth. If you look with the right eye, for example, the thumb is flush with a tree trunk, if you look with the left eye, the thumb is a good distance away from it. This proves: the right and left eyes see slightly different things. And the brain ensures that the two images become spatial.