November 15, 2015 | David F. Coppedge

Hair Makes You Bigger and Warmer

Scientists found that hair increases a beast’s surface area by a factor of 100.

“The hairier it is, the larger the creature’s true surface area,” Science Daily says. “In fact, the team says it’s 100 times greater than its skin surface area.”

Hair insulates the creature, keeping it warm. But you may be surprised to learn, according to Live Science, that mammals are not the hairiest of creatures. Researchers at Georgia Tech estimate that luna moths and butterflies have 10 billion hairs, compared to 3 million on a squirrel.

Summing the combined surface area of skin and hair increases the total surface area dramatically. A house cat, for instance, has the surface area of a ping-pong table. A honeybee grows to the size of a piece of toast. The mammal surface-area champion mentioned in the article is the sea otter. Its dense hair gives it a total surface area the size of a hockey rink.

The Georgia Tech team is particularly interested in how animals clean their hair. It’s giving them ideas for biomimetics. Different animals use active or passive methods:

Amazing FactsDogs shake water off their backs, just like a washing machine,” said Amador, who recently graduated. “Bees use bristled appendages to brush pollen off their eyes and bodies. Fruit flies use hairs on their head and thorax to catapult dust off of them at accelerations of up to 500 times Earth’s gravity.

Other animals and insects use more efficient, renewable cleaning tactics.

“They don’t do anything extra to stay clean. It just happens,” said Amador.

Eyelashes, for example, protect mammals by minimizing airflow and funneling particles away from eyes. Cicadas have sharp points on their wings that act as pincushions, essentially popping airborne bacteria like water balloons.

These strategies may inspire self-cleaning technologies for drones, Mars rovers or machines that need to operate in dusty environments.

Very interesting research, but the articles didn’t mention the various functions of hair. Many mammals seem comfortable in both summer and winter with full coats of hair, so there must be more going on than just warmth. Have you considered how your eyelashes protect your eyes, and eyebrows provide some protection from bright sun?  (Think of how extra black is smeared on to prevent snow blindness.)

Watch this cat video to see how hair may provide cats a soft landing when frightened.

Presumably individual humans’ surface areas can vary dramatically depending on how they cut their hair, and whether men are bald or bearded.



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