When cats fall, they flip themselves upside down with seemingly little effort – which has perplexed scientists for decades. Our feline friends seem to defy the laws of physics by reconfiguring themselves in the air without the intervention of another force. So how do they do it?
Several factors affect how well a cat can land on all fours, but simply put, there are two main forces at play: physics and neurology.
“One of the reasons physicists were surprised that cats could spin around to always land upright is the conservation of angular momentum,” Greg Gbur, a physicist at the University of North Carolina at Charlotte, told Live Science.
Essentially, this means that if something rotates clockwise, something else will have to rotate counterclockwise. Imagine a cat falling upside down from a stationary position. By bending at the waist, the cat can twist the front half of its body in one direction and the back half in the opposite direction. By the time it unfolds at the waist, the cat is right side up. Gbur dubbed this the “bend and twist” model in his book, “Feline Fall and Fundamental Physics” (Yale University Press, 2019).
But There are other techniques This can help cats right themselves in the air, and they are likely to employ more than one. In the “bend and turn” method, a cat extends its front paws and bends its back paws, giving the rear a lower moment of inertia, which means less resistance to changes in rotational motion. Then do the opposite, bending the front legs and extending the back ones. It has a similar effect to a spinning figure skater: Extending your arms wide increases the moment of inertia, while bringing your arms closer to your body decreases it. This inversely correlates with speed. As inertia increases, speed decreases and vice versa. Cats can also use what Gbur calls a “propeller tail,” which works in a similar way. As the tail rotates in one direction, the body can rotate in the other.
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Such contortions are possible thanks to cats’ flexible lumbar region – the space between the pelvis and the rib cage –. John Hutchinson, professor of evolutionary biomechanics at the Royal Veterinary College of the University of London, told Live Science. Cats have thin vertebrae, which makes them more flexible than other four-legged vertebrates.
This ability to fall on all fours also has a neuroanatomical explanation: the righting reflex or response. Unlike a simple reflex like a knee jerk, righting in animals is a complex reflex, meaning it’s linked to the conscious brain, Gbur said.
Righting is a behavioral response to gravity that depends on the vestibular system, which controls the balance. semicircular canals and sensors called otoliths in a cat’s inner ear detect changes in its acceleration and position relative to the ground, causing its muscles to move in a way that helps it land on its paws. Interestingly, experiments carried out in the 1950s showed that this correction response is not simply ingrained in cats from birth. When adult cats and newborn kittens were flown in jets in zero gravity conditions, the kittens were unable to right themselves, but the adult cats were able to. Because otoliths are made of dense bone, it’s possible they need to fully develop before an animal can properly right itself, Hutchinson noted, but scientists aren’t sure.
However, the height of the fall is also important. Studies It has shown that cats land with less impact when falling from heights greater than the seventh floor, for example, than from lower heights. This is mainly due to air resistance, which slows the cat’s body enough to allow it to turn. Additionally, cats are unlikely to turn properly within 0.3 to 0.6 meters (1 or 2 feet), according to research published in Annals of Improbable Research. (That’s it it’s not safe for cat owners to purposely drop their cats to test their correction response; they can get hurt, especially whether they have a vestibular disease.)
Correction responses are not exclusive to domestic cats. Many wild cats exhibit the same behavior, as do rats and rabbits. For cats, the most plausible evolutionary explanation is their tendency to climb trees and other places above the ground. For rabbits, predation is a likely evolutionary force. When a hawk darts horizontally toward a rabbit, for example, the rabbit will jump vertically, causing the hawk to scramble toward the rabbit, knocking it off its linear path. Thus, the rabbit developed a way to land upright and unharmed.
For a behavior that scientists considered just instinct for many years, Gbur said multiple techniques may be the answer.
“We have something built into our DNA to look for the simplest solution to a problem, but nature only cares about the most effective solution,” he said. “Anything that rises faster is better.”
