On Wed. Feb. 22, Dr. David Hu delivered his talk titled “Animal physics, from the tiger’s tongue to my daughter’s eyelashes” as part of the Natural Science and Mathematics Colloquium series at St. Mary’s College of Maryland (SMCM).
Dr. Hu grew up in Silver Spring, Maryland and studied mathematics and mechanical engineering at the Massachusetts Institute of Technology (MIT). He is currently a professor of mechanical engineering and biology at Georgia Tech.
His talk first focused on the physics of how animals clean themselves, including the functions of eyelashes, hairy legs, and tongues of various animals. Eyelashes are found on many mammals including opossums, kangaroos, giraffes, camels (which have two layers of eyelashes), and birds who have feathers that mimic eyelashes.
Eyelashes are important for animals because they slow the air around the eye and thus reduce particle deposition in and around the eyes. His research about eyelash length has led to the discovery that the ideal average length vs. width of animal eyelashes is L=.34W, and this has been shown true over a variety of animals.
Another discovery of animals cleaning themselves is of the hairy legs on bees. After bees return from collecting pollen, they are covered with five times their weight in pollen. The pollen is wedged into the tips of their hairs, and their leg hairs have the perfect separation so that they can easily remove most of the pollen in just a few swipes.
The tongue of cats (including house cats, bob cats and tigers) all contain angled spines that help them groom themselves. This is especially important for cats because they spend half of their waking time grooming themselves. All of these cleaning mechanisms are examples of renewable cleaning strategies for animals, that have been optimized over time for effective cleaning.
Another important part of Dr. Hu’s research had a more interesting beginning. One day while Dr. Hu was changing his son’s diaper, his son proceeded to pee on him, and Dr. Hu was amazed that his son was peeing for so long, so he counted and it took nearly 23 seconds. This experience helped inspire his research in fluid mechanics about the duration of urination in animals. Dr. Hu and his team discovered that nearly all animals over 3kg urinate for 21+/- 10 seconds.
Dr. Hu won the Ig Nobel Prize for physics in 2015 for his research about the duration of urination in animals. Ig Nobel Prizes are known as the parody of the Nobel Prizes, and are awarded each year for ten achievements “that first make people laugh and then make them think.” Other winners of the Ig Nobel Prize include Thomas Thwaites, who built prosthetics to allow him to live among goats, and Mark Avis who studied “the brand personality of rocks.” In 2014, the prize was awarded in physics to several scientists who measured the amount of friction between a person stepping on banana skin on the floor.
According to a report from Senator Jeff Flake of Arizona, Dr. Hu is responsible for 15% of the most wasteful scientific studies, but Dr. Hu stressed that anti-science attitudes “should never prevent people from taking risks.” He was proud of this accomplishment even if it had been criticized by others, because his studies and other studies listed provide valuable scientific discoveries. Dr. Hu closed his talk by encouraging the audience to “be fearless in [their] research and celebrate science humor.”