Scientists can’t escape the charm of cats, from Schrodinger’s cat, to physicist Jack Hetherington’s paper with siamese cat named Chester, to physicist Greg Gbur’s recently published Fall Felines and Fundamental Ph ysics, Falling Cats and Basic Physics.
Cats provide an important entry point for physics, mathematics, neuroscience, and even the challenges of space exploration.
Greg Gbur’s book explores an interesting topic: Why do cats always get to the ground when they fall from a high place? This is a “Falling Cat problem”.
Figures . . . Cat Falling problem (Source: Fine Art American)
A little bit of physics people will think, the cat in the air turn edmalland and do not have any fulcrum, then how it achieves the turn without violating the angular momentum conservation?
So far, there are at least four different hypotheses that explain this phenomenon: the “tuck and turn” model, in which a cat shrinks a pair of claws to rotate when it falls; the “falling figure skater” hypothesis that the cat shrinks or stretches its paws as needed to adjust its angular momentum; and the “bend and rotate” hypothesis. The cat bends over and spins back to separate the body by the waist; the last is the “propeller tail”, in which the cat can use its tail to turn around in the air.
People who have kept cats must have observed that when the cat falls, the tail and body are turned in reverse, so they will feel that the tail plays an important role. But it was later discovered that cats without tails could also get their feet on the ground first. On the other hand, in order for the torso to turn 180 degrees in a short period of time, the tail must turn dozens of times in the opposite direction at the same time in order to maintain the system’s momentum moment is zero. This speed is basically close to the speed of the aircraft’s propellers, thus denying the decisive effect of the cat’s tail.
Some scholars believe that the presence of vestibular organs in the cat’s inner ear can act as a balance and a compass-like one, which may also be an important reason. But what is the fundamental principle?
Greg Gbur says in the book that the cat’s ability to rotate from four feet to the ground in the air should take advantage of all the principles of the combination. But the most basic and important explanation is the “bend and rotate” hypothesis, whereby the cat bends down and then rotates the upper and lower half in the opposite direction to counteract these movements. Other aspects will make minor corrections, such as using a tail or claws as another lever.
Figures . . . A photo of the cat dropping with a high-speed camera (Source: Wikipedia)
The study of the “falling cat problem” can not be separated from the high-speed camera. Back in 1894, the French scientist, Stienne-Jules Marey, published a photo of a cat falling with a high-speed camera on Nature, showing that the cat had completed the turn in the first 1/8 seconds of its fall.
He thinks cats are taking advantage of their mass inertia to turn over. The twisting force of the spinal muscle activity acts first on the front leg, which has a very small inertial movement because the front leg is shortened and close to the neck. But the hind legs are stretched and almost perpendicular to the body’s axis, and its rotational inertia and torsional force are in the opposite direction. In the second stage of motion, the posture of the foot is opposite, and the inertia generated by the first stage provides a fulcrum for the rotation behind.
Videos . . . The U.S. Air Force experiment, “space cat” can still foot first on the ground? (Source: YouTube)
But many physicists at the time believed that the cat-throwing movement must have had an impact on the study, otherwise the experiment suggested that free fall might have gained angular momentum.
In 1969, Kane and Scher, two researchers, built the Kane-Scher model, modeling the cat as a pair of connected cylinders that could change the relative direction, representing the cat’s upper and lower half, which rotate with zero angular momentum.
Is the “cat-dropping problem” a perfect solution? In fact, not.
It has also been found that cats fall from a height of less than 30 cm can not be four feet on the ground, falling from a height can not always be four feet on the ground, beyond a certain height, the cat will open four, like a parachute, and then with a stomach to the ground. A cat fell off the 32nd floor and was hospitalized for two days, which involved some other physics problems.
Figures . . . Kane-Scher model (Source: Wikipedia)
Fat cats and thin cats, long cats and short cats, different kinds of cats each twist, bend is not the same, lions, tigers and other cats do not have the same skills? Have we mastered the above principles to create a robot that is cat-like and can be thrown into the air at will but always perfectly landed?
There are still many issues to be explored, so the “cat-dropping problem” is still an active area of research.
Figures . . . “Cat’s Confusion” (Source: DeepTech)
Warm Tip: Please do not throw the cat from a height at will, this is extremely irresponsible behavior.
Although for cats, they don’t know what humans are doing, they were locked up decades ago in a black room with “bombs” and now being repeatedly thrown down to see if they fall or die.
There may be a kind of confusion, called “cat confusion”.