Seeing in stereo means seeing with two eyes working together,which is called stereoscopic sight.This allows you to view the world in three dimensions,or 3-D.Seeing depth helps you to judge the distance between you and the objects you see and to adjust to the changing angle at which you see something as you move closer to or farther away from it.If images are coming from only one eye, however,only two of these dimensions-height and width-can be perceived.A world seen with one eye is thus two-dimensional,as in a photograph.
Now consider why your two eyes are on the front of your face.Think of other animals with this same arrangement.They are all animals that hunt,like lions and wolves.Their eyes face directly in front of them.This provides a field of sight about 180 degrees wide,which is called binocular sight.On the other hand,animals that are hunted have eyes on the sides of the head,which provides nearly 360-degree field of sight.In order to stay alive,they need to see things coming from the sides and from behind.However,without stereoscopic sight,they have difficulty determining how far a danger is.
With sight both stereoscopic and binocular,humans share with animal hunters the ability to
see from side to side and to accurately determine the distance.If you think it would be great to
have another type of sight,perhaps with hundreds of tiny eyes like many insects do,think again! Each tiny insect eye sees only a tiny part.Besides,what if you needed glasses? Be glad for the
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