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Hair helps keep you warm, right? But hair can also keep you cooler than bare skin, as long as the hair is not too thick. So says a study in the journal PLoS ONE.
毛发能帮助身体保暖，对吗？然而只要毛发不是太厚，其散热效果甚至比裸露的皮肤更强。一项发表在《公共科学图书馆·综合》杂志上的研究如是说道。
Researchers studied elephants, which have very thin coats of hair. It's easy for the beasts to overheat: they may face temperatures of up to 120 degrees Fahrenheit, and they don't have much skin surface area to radiate the heat relative to their big body volume.
研究人员以毛发稀疏的大象作为研究对象。野生动物总是很容易就身体过热：它们的体温可能超过120华氏摄氏度，而且能够辐射热量的皮肤表面积也不多。
That's where the hair comes in. The researchers wrote equations modeling the elephants' hairy skin. As they expected, thick hair traps air and keeps the body warm. But below a certain density, hair stops insulating and wicks heat off the body instead—helping the elephants get rid of an extra 20 percent of their body heat, especially on windless days.
这时毛发就派上用场了。研究人员编写了程序，建立了大象的体表毛发模型。正如他们所预期的，厚毛发隔绝空气，使身体保持温暖。但当毛发密度低于一定程度时就不再隔热，而是散发身体的热量——大象可通过这种方式散发20%的身体热量，尤其是在无风的日子里。
Heat sinks inside computers work in a similar way, with pins sticking up to help dissipate the interior heat.
电脑内部的散热器就是以类似的方式，利用突出的插脚帮助内核散热。
The researchers speculate that hair may have actually evolved to help animals stay cool, because it first sprouted in mammals over a hundred million years ago in a hot climate. Hair-raising times, indeed.
研究而人员推测，进化出毛发是为了保持身体凉爽，因为毛发是在一亿年前炎热的季节首次在哺乳动物身上生长的。真是“毛骨悚然”的时代。
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