Many people believe that you should keep your head covered during cold weather, as most body heat is lost through the head. It’s certainly true that any part of your body that’s exposed to cooler air will lose warmth; heat always moves from something warm to something cooler (that’s called the second law of thermodynamics). And our heads and faces are more sensitive to changes in temperature than other parts of the body.
However, the idea that more heat is lost from our heads isn’t actually true. It seems to date back to an experiment carried out by the US military in the 1950s; volunteers wore Arctic survival suits in very low temperatures as a way of testing their efficiency. Naturally, with the volunteers’ bodies covered but their heads bare, most of the body heat lost was through the head!
The results of this not very scientific test seem to have been misinterpreted and spread. A 1970s survival manual issued by the US army strongly recommends wearing a hat in cold weather because “40 to 45 percent of body heat” is lost from the head; as time passed this idea seems to have become widely accepted as the truth. So by all means, wear a hat when it’s cold – but you won’t suddenly freeze if you take it off!
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Sam blogs about all kinds of science at www.samanthagouldson.com.