Why a cat always lands on its feet


Picture this: It’s the 19th century, and scientists are driven to the brink of madness by a perplexing question — why do cats always land on their feet?

Despite countless theories, no one could quite crack the code.

That is until one inventive mind decided to turn to an unexpected tool: the camera.

Enter Étienne-Jules Marey

Étienne-Jules Marey was a scientist and inventor obsessed with understanding motion.

At a time when photography was mostly used to capture static scenes, Marey had a different idea. He wanted to capture motion itself.

Using a basic photography principle, Marey created a technique to record movement. He exposed photosensitive material to light and then covered it in darkness.

But his method was ingenious — he used a disc with slots to control the light as his subject moved, allowing him to record the movement onto a single glass plate.

This technique, known as chronophotography, revealed individual stages of motion, something the human eye could never see on its own.

The Birth of the Movie Camera

A few years later, Kodak introduced celluloid film, and Marey updated his camera. Instead of using a single glass plate, he used a roll of film that moved between exposures.

Light would create an image, then darkness would allow the film to move, creating a sequence of images — essentially, a movie camera.

Marey used this technique to study various subjects, even dropping animals like rabbits and chickens to see if they, too, would land on their feet.

But it was his work with cats that truly stood out.

The Cat’s Secret Revealed

Marey’s films showed that cats could right themselves mid-air without any external push, seemingly defying the law of conservation of angular momentum.

This law, one of Newton’s laws of motion, states that an object in motion cannot change its motion without an external force. But to the naked eye, cats seemed to break this rule.

Most people assumed cats kicked off from the hands of the person dropping them, but Marey’s films proved otherwise.

In the first few frames, it was clear that cats didn’t start their rotation with a kick.

Instead, they arched their backs, dividing their bodies into a front part and a back part, allowing each part to move independently.

The Science of the Cat’s Fall

Here’s how it works: Early in the rotation, the cat pulls its front legs in and leaves its back legs splayed out.

This allows the front half to rotate quickly while the back half stays relatively still. Then, halfway through the fall, the cat does the opposite.

It stretches out its front legs and tucks in its back legs, flipping the other half of its body around. By the time the cat is ready to land, all four legs are stretched out to slow the rotation.

The two halves of the cat’s body work in opposite directions, canceling out each other’s motion and adhering to Newton’s law.

A Milestone in Scientific Photography

Marey published his findings in Nature in 1894, breaking down the falling cat problem for the first time.

His work is an early example of using photography for scientific discovery. Photography, as Marey demonstrated, can record moments that the human eye can never see, making them permanent for analysis and sharing.

The Legacy of Motion Photography

Marey’s work paved the way for future innovations.

Another famous example is Eadweard Muybridge, who in 1878 used 12 cameras connected to tripwires to prove that a horse lifts all four feet off the ground at some point in a gallop.

Through their pioneering efforts, Marey and Muybridge showed the world that photography could do more than capture still moments.

It could unlock the secrets of motion, helping us understand the fundamental principles of physics that govern our world — and, of course, the graceful acrobatics of our feline friends.