Share it! Science : Just the Right Length: Eyelash Physics

Just the Right Length: Eyelash Physics

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     Those long, lush eyelashes mascara commercials are pushing for my actually be putting women at an evolutionary disadvantage. Eyelashes serve an important purpose, keeping small debris out of one of our most important mucous membranes. They also let us know when something is close to our eyes so that they are not poked! Researchers have found that there is an optimum length for eyelashes. This Goldilocks length of about one-third the length of the eye appears to provide the best protection for animal peepers.
     David Hu, a scientist at the Georgia Institute of Technology in Atlanta, studies how air flows around an animals body parts. He found that when eyelashes are long they actually funnel air, and consequently the dust and particles in the air, directly into the eye. If the eyelashes are too short, they don't provide enough protection. The medium length eyelashes deflect about half of the particles from entering the eye.
     Hu and his team completed several experiments, surveyed actual animal eyelashes and used computer models to come to their conclusions. Through experimentation they found that eyelashes mostly deflect air to keep debris out, rather than actually catching the debris. Therefore, the eye is working more as a particle diverter, rather than a filter. They measured the eyelashes on animal pelts of 22 species, from hedgehogs to giraffes. The one-third of the eye length ration held true in these specimens just as computer models predicted.
     This new information might be useful to engineers in improving products such as protective gear for camera lenses and sensors. It might even have some implications in battling conditions such as dry eye in humans.
     This study would be a great addition to many science topics- ratios in the body and in nature, animal adaptations and a study of the eye. There are resource links and book suggestions for lessons on the eye below. We'd love to hear how you incorporate this into your science lessons! Comment below, or e-mail me at:

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Resources for Eye activities and Lessons:
Book Suggestions:
(Click images for more information about books. Please see disclosure statement on sidebar about affiliate links.)
For book reviews on "Eye to Eye: How Animals See the World" and "Animal Eyes" check out "Looking at Eyes" by Sue Heavenrich on the STEM Friday blog.

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