Anyone who has lived with a cat has seen it happen. A cat slips off a shelf or tumbles off the arm of a sofa, and a split second later it touches down neatly on all four paws. It looks like a magic trick. So how does a falling cat know which way is down, and how does it turn over with nothing to grab?
The short answer is a built-in skill called the cat righting reflex. A falling cat figures out which way is up using its eyes and the balance organs in its inner ear. Then it twists its body in a quick, clever sequence, front half first and back half second. An unusually flexible backbone and the lack of a working collarbone make the move possible.
The Twist, Step by Step
Here's the puzzling part. A cat in free fall has nothing to push against, and the laws of physics say a body can't just start spinning out of nowhere. The secret is that a cat isn't a stiff object. It can change its shape on the way down.
First, the cat bends in the middle, so its front half and back half can turn on slightly different axes. Next, it tucks its front legs in close and stretches its back legs out. A tucked half spins easily, while a stretched-out half resists turning. That lets the front of the cat rotate as much as 90 degrees while the rear only swings back about 10 degrees.
Then the cat swaps. It stretches its front legs and tucks its back legs, so now the rear half can catch up. Depending on how flexible the cat is, it may repeat these steps until it has turned all the way over. The tail seems to help, but cats without tails can do it too.
Scientists Argued About It for Years
The falling cat puzzled some very big names in science, including James Clerk Maxwell and George Gabriel Stokes. Maxwell once wrote to his wife that people at Trinity believed he used to throw cats out of windows. He insisted the proper method was to drop a cat onto a table or bed from about two inches, and that even then it landed on its feet.
The real breakthrough came from Étienne-Jules Marey, who used rapid-fire photography to capture a cat in mid-fall. His pictures showed that the cat wasn't cheating by pushing off the handler's hand, and that air resistance played no role in turning it over. The cat was doing it all with its own body.
Built In From Kittenhood
Kittens aren't born with the full skill. The righting reflex starts to show up at about three to four weeks of age and is perfected by six to nine weeks. Cats aren't alone, either. Rabbits, rats, lizards, and even some stick insects have been seen righting themselves in mid-air.
Not Quite a Guarantee
Despite the saying, cats don't always walk away from a fall. They can still break bones or be badly hurt, especially from great heights. Vets even have a name for the injuries cats get from falling out of tall buildings: high-rise syndrome.
Cats do have a few extra advantages. Their small size, light bones, and thick fur slow them down, and a falling cat spreads its body out to catch more air. A cat with its legs stretched out tops out at about 60 miles per hour, roughly half the falling speed of an average-sized man. One famous 1987 study of cats that fell from New York buildings even found a cat that fell 40 stories without injury, apparently after bouncing off a canopy into a planter. Still, a screen on an open window is a much better plan than relying on luck.
So the next time your cat lands a perfect ten off the kitchen counter, give it a little credit. It just solved a physics problem that puzzled great scientists, and it did it in less time than it takes to say "here, kitty."
