How do cats always land on their feet?

Through a reflex called the righting reflex, which lets a falling cat rotate its body without anything to push against — a manoeuvre that looks like it should violate the laws of physics and does not.

The problem is that in free fall there is nothing to push off. Angular momentum is conserved, so a cat cannot simply "turn". What it does instead is change its shape in a sequence that rotates the body without changing total angular momentum.

The sequence, which happens in a fraction of a second:

The cat determines which way is up, using the vestibular system in the inner ear and its vision. It then bends at the waist, effectively splitting the body into two halves that can rotate independently. It tucks the front legs in tight and extends the rear legs out — a tucked mass rotates faster than an extended one, exactly as a spinning skater speeds up by pulling their arms in. The front half turns a long way while the back half turns only slightly. Then it reverses the configuration, tucking the rear and extending the front, and the back half catches up.

Repeated as necessary, this brings all four feet downward. The tail assists with fine balance but is not essential — cats without tails manage it.

The reflex develops at around three to four weeks and is usually fully functional by six or seven.

Importantly, it is not a guarantee of safety. Landing feet-first does not prevent injury, and falls from any height can cause serious harm. Short falls can be more dangerous than slightly longer ones, because there is insufficient time to complete the rotation. Cats are not immune to falling, and open upper-floor windows are a genuine hazard.