Why do cats always fall on their paws? Knowing this is also useful for astronauts and robots

To make a long story short, he confirmed with his films that, falling from a certain height and on their backs, cats could turn around and land on their paws. And therein lies the problem because this manoeuvre apparently requires violating one of the fundamental principles of classical physics: the conservation of angular momentum, which is well exemplified by ice skaters, for example, when they rotate on themselves and increase or decrease their rotational speed simply by extending or retracting their arms.

But back to cats: at the University of North Carolina at Charlotte, in America's famous 'Research Triangle', scholars have offered a new perspective on the fall of felines, published after a couple of years of research in a paper published in February in the journal 'The Anatomical Record'.

Part of the difficulty lies in the fact that the cat's anatomy had not been studied in detail, explained Yasuo Higurashi, physiologist at Yamaguchi University in Japan and lead author of the study. And the solution lies in the spine, which had not been given due consideration. It is she who explains how the beloved feline can turn in flight without sending a fundamental principle of classical mechanics into the dustbin.

In their study, Higurashi and colleagues examined, from an anatomical point of view, the various spinal column segments of cats, on naturally dead specimens, and also by dropping a pair of cats in various ways from a height of one metre, without any danger as they landed on a cushion.

The secret lies in the hitherto unknown fine anatomy of the cat: the feline spine has variable flexibility, greater at the top and much stiffer and heavier at the bottom.

The videos taken of the two cats who patiently 'collaborated' in the research show exactly this: first they easily rotate their front paws, and so also see where they are falling, and then their lower body, more slowly.

It is not the ultimate solution to the problem, but a good step forward: the cat is more complicated than the equations we currently know how to put down on paper to describe it: cats are always eluding us, but less and less, and we will soon be able to 'cage' them in four definitive equations.

One might wonder what the point is of studying the fall of cats for almost two centuries. Research is certainly not an end in itself: there is much to be improved in mathematical models of animal movement, useful for helping veterinarians to treat fractures, but also for analysing the movements of astronauts in space in microgravity or for having more agile robots than those of today.