KEEPING WARM 
The structure of a polar bear 
hair , magnified hundreds of times 
in this scanning electron micrograph, 
may hold the key to new ways of 
designing protective clothing. 
were lying. But when the photographers 
used ultraviolet film, the results were 
startlingly successful. The bears and 
harp seals showed up as black objects on 
the white ice, indicating that the ani- 
mals were thoroughly absorbent in the 
ultraviolet range. This phenomenon was 
intriguing enough to prompt a study of 
polar bear skin and hair. 
Analysis showed that the tapered 
bear hair is not really white but is a 
pigmentless structure with a core of 
such low density that it is nearly hollow. 
In simple terms, the polar bear’s white 
appearance is caused in large part by 
internal reflections in the polar bear 
hairs. This is analogous to the way in 
which the whitish appearance associ- 
ated with ice derives from light reflec- 
tion off of many internal surfaces. With 
photographic evidence showing that the 
polar bear was absorbing energy in the 
ultraviolet range, there was another 
question to be answered: Was the low- 
density core of the bear's hair acting as a 
“light pipe,” permitting the absorbed 
ultraviolet energy (perhaps now trans- 
formed into another form of energy) to 
be transmitted into the bear’s hide 
through internal reflections? A math- 
ematical model of polar bear hair 
showed that this was entirely possible. 
That may mean that in addition to pro- 
viding useful insulation, polar bear hair 
may be even more valuable in energy 
gathering, functioning as a special kind 
of solar cell. Perhaps tomorrow’s cold 
weather clothing will be made of materi- 
als that go far beyond today’s “trapped 
air” insulation techniques and emulate 
instead the hair of the polar bear. It’s 
something to think about. □ 
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Good Housekeeping 
THE PROOF IS 
IN THE WEARING! 
damart 
Thermawear 
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