by Ned Rozell
May 03, 2005
Daniel Koon, an associate professor of physics at St. Lawrence University in New York, became fascinated by the subject when he first read about it in a physics text book. His interest led him to assemble an Internet site that holds a few dozen newspaper and magazine articles that describe how light can travel the length of a polar bear hair in the same way water flows through a pipe. The theory goes like this: sunlight is captured by each hair, directed to the bear's black skin, and converted there to heat, thereby providing warmth to the polar bear.
Photographer: Captain Budd Christman, NOAA Corps - Photo courtesy NOAA
Koon decided to test if a polar bear's hair could actually conduct light. Koon and a student, Reid Hutchins, got a few hairs from a male polar bear that lives at a zoo in Rochester, New York. Their research revealed that the popular notion was not correct, they found that less than .001 percent of red light and less than a trillionth of the violet light transmitted traveled the length of a typical, inch-long hair. Even less ultraviolet light made it from the tip to the base of the hair.
Koon compared a polar bear hair to a pane of window glass. We can see through a window, but if that same sheet of glass is stacked like plywood and viewed through its edge, the glass appears green. In the same way, a polar bear hair looks transparent when lying on a table, but if you picked it up and tried to see through it lengthwise, as you would look through a telescope, the hair would no longer be transparent.
If a polar bear's skin is not absorbing ultraviolet light, where is the light going? Researchers at Penn State University had long ago suggested that the ultraviolet absorption of polar bears was due to keratin, the protein from which hair is made. Koon agrees that keratin is probably the substance that prevents polar bear hairs from carrying light to the skin. More importantly, he thinks the widespread belief in polar bear hairs as light carriers illustrates a problem in science: people want to believe in the fantastic and the fantastic is often accepted without being tested.
As writer Bertrand Russell pointed out, even Aristotle--the most famous scientist of his day--claimed that women have fewer teeth than men, though it never occurred to him to check Mrs. Aristotle's mouth. The moral of Koon's study is that a little dose of skepticism never hurts.
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