Flexible feline spines shed light on 'falling cat' problem

Source: Ars Technica

Why do falling cats always seem to land on their feet? Scientists have debated the precise mechanism for centuries—since at least the 1700s—conducting experiments to pinpoint the underlying physics. A recent paper published in The Anatomical Record reports new experiments analyzing the flexibility of feline spines link.

We previously covered this topic in depth in 2019 Ars Technica article, when University of North Carolina, Charlotte physicist Greg Gbur published his book Falling Felines and Fundamental Physics. For a long time, scientists believed it would be impossible for a cat in free fall to turn over, making Etienne‑Jules Marey’s 1894 high‑speed photographs of a falling cat landing on its feet especially shocking. Gbur emphasized that cats are living creatures, not idealized rigid bodies, so the motion is more complicated than simple rigid‑body dynamics.

Historical hypotheses

1. Tuck‑and‑turn – the cat pulls in one set of paws, allowing different body sections to rotate relative to each other.
2. Falling figure‑skater – inspired by James Clerk Maxwell’s idea that a cat can adjust its angular momentum by extending or retracting its limbs, analogous to a figure skater pulling in arms to spin faster.
3. Bend‑and‑twist – the cat bends at the waist, causing the two body segments to counter‑rotate.
4. Propeller tail – the cat reverses its body’s rotation by spinning its tail like a propeller.

Gbur told Ars Technica that, while all these motions contribute, he originally considered the bend‑and‑twist mechanism the most fundamental link. He noted that “there are all these little corrections on top of that: using the tail, or using the paws for additional leverage, also play a role.”

Recent research

The new study re‑examines feline spinal flexibility and suggests a shift in emphasis toward the tuck‑and‑turn mechanism. Gbur discusses this updated perspective in his recent blog post link, giving more credence to the idea that the cat’s ability to tuck its front half and turn its rear half is central to the righting reflex.