Friday, May 10, 2024

Wilczek says Falling Cats have Free Will

Physicist Frank Wilczek is famous for helping explain the short range nature of the strong force, and now he wrote a strange paper on cats. No, not Schroedinger cats.
Free Will and Falling Cats

If we consider a cat to be an isolated mechanical system governed by T-invariant mechanics, then its ability to land on its feet after being released from rest is incomprehensible. It is more appropriate to treat the cat as a creature that can change its shape in order to accomplish a purpose. Within that framework we can construct a useful and informative of the observed motion. One can learn from this example.

He seems to be saying that it is impossible for a falling cat to land on its feet, unless it has free will.

He proves it is impossible, but then says cats have a loophole because "They can readily and selectively consume stored energy, notably by converting ATP into ADP, empowering mechanical motion accompanied by radiation of heat."

This is bizarre. The physics of falling cats is well-understood, and does not require free will or ATP or heat or anything like that. See A simple model for the falling cat problem. There is even a Wikipedia article on it.

The paradox is that the cat falls with zero angular momentum, a conserved quantity, and it is hard to see how it can get its feet down without some angular momentum. But as the above paper explains, the cat can twist its body without any net angular momentum.

Wilczek has some philosophical comments that went over my head, so maybe I am not fully appreciating his paper. After all, he has a Nobel Prize and I don't. What am I missing? He does cite a book on "Falling Felines and Fundamental Physics", so he must know that this is understood.


  1. It's a bit of an odd paper certainly.
    This passage:
    "But, as articulated most clearly in the many-worlds interpretation of quantum theory, the relationship between the wave-function and experienced reality is not deterministic"
    is a bit daft. The lack of determinism is clear in conventional QM, I don't know why silly ideas like MWI need to be mentioned at all.

    1. Good point. Some MWI advocates say that it is deterministic, as the branches are all determined by the initial conditions. So it is hard to see how citing MWI helps make his point. Furthermore, the next sentence says "measurements inevitably change the wave-function", which is contrary to what MWI teaches.

  2. Does Prof. Wilczek have any philosophical / metaphysical / ontological ideas about QM? Just curious...