Post created by: Anna
When I first think of physics, an image of little model cars comes to mind. I picture teams of students huddled around a ramp where they’d place their 4-wheeled contraptions and watch them as they sped downward, timers in hand. Who could make the fastest car with the limited materials available? That was my fifth grade introduction to physics. Back then, I thought physics was a field of its own, almost entirely concerned with the study of motion, energy, and matter. Until very recently, I hadn’t put much thought into why physics might be of any importance for a biology degree. But now I am beginning to see the inter-connectivity between physics and other fields, namely, biophysics, chemical physics, astrophysics, and geophysics. And, I am beginning to see how this type of science will affect me in my hopes to someday be a veterinarian.
Although biology is concerned with the study of life and living organisms, physics plays a key role in explaining how bodily functions operate. As an integral part of that system, the immune system transports white blood cells through the body to ward of disease and inflection. Simple enough. But in an experiment by Georgia Tech, researchers have concluded that white blood cells use physics to transport themselves in such a manner. The body utilizes the white blood cell’s mechanical properties--its relative softness or stiffness--to regulate the cell’s activity and location. According to Wilbur Lam, an assistant professor in the Department of Biomedical Engineering at GT, “The soft cells are always flowing in the middle of the bloodstream, while the stiff ones are sequestered on the edges” (Toon, “Horizons”). As billions of cells collide, a process occurs in which the cells are effectively “sorted” to wherever the body most needs them--either along cell walls or in the bloodstream. This physics-centered phenomenon has a chemical inspiration, however. The manipulation in a white blood cell’s actin level is what causes the change in firmness that the white blood cell undergoes (Toon, “Horizons”). So in changing from a dormant to an active state, the white blood cell changes its chemical makeup, which in turn allows it to manipulate its whereabouts in the body through its ability to alter location depending on relative how firm it is.
As we zoom out from the microscopic and inter-bodily world, I feel like it’s necessary for me to reiterate that physics is not something we witness only in our labs and classrooms. It’s commonplace in our everyday lives, albeit in very unexpected ways. You know the way your dog habitually dries itself off using a high-speed shaking motion that covers the entire bathroom with water droplets? Or maybe you’re one of the smart ones who bathes their dog outside. Regardless, there is a great deal more involved in that shake that what you may initially think. The shake is based in the mechanics of a mammal’s loose skin. Because their backbone is relatively inflexible, it’s the looseness of their skin that enables dogs to rotate their bodies so far to either side. While the backbone can only move 30 degrees to the left and right from its center, the skin, on the other hand, can swing 90 degrees like a pendulum from the backbone (Madrigal, “Technology”). This phenomenon takes very little energy from a dog. As an animal whips from side to side, centripetal force is created, allowing a wet dog to remove 70% of its coat’s water in four seconds with ease (Cole).
Why is this so useful for mammals? Water destroys fur’s insulation properties. Humans typically use body heat to evaporate the water from our hair, but an animal’s fur can trap much greater amounts of water. In their most recent paper, the George Tech team wrote that “A wet 60-pound dog, with one pound of water in its fur, would use 20 percent of its daily caloric intake simply to air-dry” (Cole, “The Physics…”) Thus, shaking is far more energy-efficient.
Our bodies our incredible. The way creatures, as small as a mouse and as large as a grizzly bear share such incredible characteristics--from preventing illness through strategizing white blood cell usage to engaging in a shaking motion to prevent loss of calories, animals are uniquely designed for survival. And although humans avoid the latter, if not simply because we would look funny doing it, physics is pervasive throughout our lives. Our lives revolve around physical phenomena--the forces of gravity that dictate how high we jump, the differences in pressure that allow our lungs to breathe, and the momentum it takes to throw a discus, are all examples of such. So while my fifth-grade self doubted whether physics would ever get me very far in life, my thirteenth-grade self knows that it is what life relies upon.
Works Cited
Cole, Linda. “The Physics of a Wet Dog Shake.” CANIDAE. 26 Aug. 2015, www.canidae.com/blog/2015/08/the-physics-of-a-wet-dog-shake/.
Madrigal, Alexis C. “Technology: Science: Dogs Can Shake 70% of the Water from Their Fur in 4 Seconds, Here’s How.” The Atlantic. 15 Aug. 2012, www.theatlantic.com/technology/ archive/2012/08/science-dogs-can-shake-70-of-the-water-from-their-fur-in-4-seconds-heres-how/261191/.
Toon, John. “Horizons: Physics: It’s What’s Happening Inside Your Body Right Now.” Georgia Tech. 8 Feb. 2016, rh.gatech.edu/news/496271/physics-its-whats-happening-inside- your-body-right-now.
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