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SEEING THE LIGHT : Understanding the true nature of light, says a physicist, requires not looking only throught the eyes but with the soul.

July 25, 1993|ARTHUR ZAJONC | This article is adapted from "Catching the Light," recently published by Bantam Books, 1993 by Arthur Zajonc. Zajonc is a professor at Amherst College

IN 1910, TWO FRENCH SURGEONS WROTE about their successful operation on an 8-year-old boy who had been blind since birth because of cataracts. When the boy's eyes were healed, they removed the bandages, eager to discover how well the child could see. Waving a hand in front of the boy's physically perfect eyes, they asked him what he saw. He replied weakly, "I don't know."* "Don't you see it moving?" they asked. * "I don't know" was his only reply. * The boy's eyes were clearly not following the slowly moving hand. What he saw was only a varying brightness in front of him. He was then allowed to touch the hand as it began to move; he cried out in a voice of triumph: "It's moving!" He could feel it move, and even, as he said, "hear it move," but he still needed laboriously to learn to see it move. Passing through the now-clear black pupil of the child's eye, that first light called forth no echoing image from within. The child's sight began as a hollow, silent, dark and frightening kind of seeing. The light of day beckoned, but no light of mind replied within the boy's anxious, open eyes.

The lights of nature and of mind entwine within the eye and call forth vision. Yet separately, each light is mysterious and dark. Even the brightest light can escape our sight.

AS PART OF WHAT I CALL "PROJECT EUREKA," A FRIEND AND I HAVE designed and constructed a science exhibit in which one views a region of space filled with light. It is a simple but startling demonstration that uses only a carefully fabricated box and a projector whose light shines directly into it. We have taken special care to ensure that light does not illuminate any interior objects or surfaces in the box. Within the box, there is only pure light and lots of it. The question is: What does one see? How does light look when left entirely to itself?

Approaching the exhibit, I turn on the projector, whose bulb and lenses can be seen through a Plexiglas panel. The projector sends a brilliant light through optical elements into the box beside it. Moving over to a view port, I look into the box and at the light within. What do I see? Absolute darkness! I see nothing but the blackness of empty space.

On the outside of the box is a handle connected to a wand that can move into and out of the box's interior. When I pull the handle, the wand flashes through the dark space before me, and I see it brilliantly lit on one side. The space clearly is not empty but filled with light. Without an object on which the light can fall, one sees only darkness. Light itself is always invisible. We see only things, only objects, not light.

TWO LIGHTS BRIGHTEN OUR WORLD. ONE IS PROVIDED BY THE SUN, but another answers to it--the light of the eye. Only through their entwining do we see; lacking either, we are blind.

Arguably the best-studied case of recovery from congenital blindness is the case of S.B. On Dec. 9, 1958, and Jan. 1, 1959, a blind British man, 50 years old, received cornea transplants. A boot repairman, he had lived a life that was unusually independent for a blind adult, for example going for long bicycle rides by holding onto the shoulder of a friend. He enjoyed gardening and especially any kind of work with his hands, and was a confident, cheerful and clearly intelligent man. Now, for the first time since he was 10 months old, he had complete functional use of his eyes. What did he see?

Examining him about a month after the transplants, researchers R.L. Gregory and J.G. Wallace asked him about his first visual experience following the operation. S.B. replied that he had heard his surgeon's voice, and turning toward the sound, saw a "blur." S.B. was unsure what the blur was but reasoned that since he had heard the voice of his physician, and knew that voices come from faces, the blur in front of him must be his doctor. Faces, even long after the operation, were "never easy," S.B. reported. Nor were his struggles with seeing confined to faces. Gregory and Wallace's research with S.B. (and similar research before and since) has made it clear that learning to see as an adult is not easy at all.

The researchers took S.B. to a museum of technology and science, and because he had a longstanding interest in tools, he was clearly excited at the prospect of seeing what he had only handled or heard described. Stopping at a fine screw-cutting lathe, they asked him to tell them what stood before him. Obviously upset, S.B. could say nothing. He complained that he could not see the metal being worked. Then he was brought closer and allowed to touch the lathe. He ran his hands eagerly over it with his eyes shut tight. Standing back a little and opening his eyes, he declared, "Now that I've felt it I can see it."

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