Free The Great White Bear by Kieran Mulvaney Page A

heat inside the pelt."
    In other words, polar bear hairs let some of the sun's warming rays pass through, but they don't let the heat radiate back out. Not only that, but because the hairs are hollow, they contain air that is warmed by the heat trapped within the pelt, causing further warming.
    It is the final line of defense against the polar bear's most constant and potentially dangerous enemy, the bitter chill of its Arctic domain, and perhaps the most effective. (Although not, of course, in the very dead of winter, when there is no daylight at all. For the mechanism to work, it needs sunlight.) It is also a line of defense that has been frequently misreported and misunderstood.
    A polar bear hair does not, as Richard C. Davids writes, act as "a miniature light pipe that funnels only ultraviolet light down through its core to be absorbed by the black skin." That idea—that polar bear hairs not only trap heat from sunlight but actively channel the ultraviolet directly to the skin—is a myth, but a persistent one. Its origins lie in a misreading of both Øritsland's research on polar bear fur and another study he conducted with Lavigne.
    In 1974, the two men were attempting to determine a means of counting seal pups from the air that was more effective than searching for white seals on white ice.
    "We discovered that ultraviolet photography turns white seals black, and in the course of doing so, we discovered that ultraviolet photography turns most white animals black," Lavigne recalls. "We were in a hurry and wanted to photograph a white animal from the air, so we went to Churchill, Manitoba, and photographed a polar bear with three cubs, and they all showed up black. That led to a cover story in
Nature
called 'Black Polar Bears.'"
    The reason seal pups and polar bears look black when photographed in ultraviolet is that their fur absorbs UV radiation; conversely, they appear white to us in normal conditions because the fur reflects visible light. There is no obvious benefit to the bears—or the seals—from absorbing UV radiation in this way; as Lavigne noted, it turns out that most white animals do so, and later he discovered that the Canadian military's equipment, painted white to provide camouflage in snowy Arctic environments, did as well. *
    But subsequently, some American military researchers who had not been involved in either study conflated the two findings and, speaking to a reporter for
Time
magazine, described the process differently.
    "Now the ultraviolet hits the polar bear, gets to the hollow pipe which acts as a fiber optic, transmits this high-energy ultraviolet radiation into the skin, and then heats up the bear," says Lavigne, describing the distorted version. "But the problem is that the ultraviolet never gets to travel down the hair because the whole point of what Nils and I described is that it is immediately
absorbed
by the hair."
    Even so, what Lavigne describes as "the myth of the solar polar bear" endures. "Solar energy? Do polar bears hold the secret?" asked the
Washington Post
rhetorically in 1987. "Polar bears' fur holds clue to better lasers," insisted the London
Sunday Times
in 1995. Even the august
Scientific American
got in on the act, headlining a 1988 article simply and succinctly, "Solar Polar Bears."
    It endures partly because distinctions among visible spectrum light, infrared, and ultraviolet, among absorption and reflection and transmission, can be subtle and confusing. It endures because it is hard to fact-check when so many sources have repeated the story as gospel. But it endures also because it seems like something that should be true, that a magnificent animal in an almost impossibly hostile environment should have developed an almost fantastic mechanism for keeping warm.
    The pity of it is that the truth needs no elaboration. Every polar bear is so well insulated that not only does it boast a thick layer of blubber and a warm pelt, but that pelt warms the cold