That cat in the box again

[Aitch]

I don't care whether the cat is alive or dead, I'm still going to report Mr Schrödinger to the RSPCA for locking it in that box!

 

[Fredrik]

And, of course, the cat being dead and alive only "happens" (in some sense of the word) if you subscribe to the Copenhagen interpretation, right? In the many-worlds view, that problem disappears (as does the one that started this thread).

Not really. Even if you prefer Copenhagen, you can't just assume that the cat is always either dead or alive. That sort of assumption leads to Bell inequalities, which have been shown to be violated in experiments.

You can take the point of view that quantum mechanics is just an algorithm that lets us calculate the probabilities of possible results of experiments, rather than a description of reality. This would "remove" the problem, but is it the solution of the problem, or just a way to ignore it? No one knows.

The view that quantum mechanics describes reality (which is a much stronger statement than saying that it merely lets us calculate probabilities of possibilities), along with the statement that the time evolution of every isolated physical system is described by the Schrödinger equation, is the many-worlds interpretation. So I'd say that the problem is even worse in the MWI.

 

[Cuddles]

I thought the whole point of the thought experiment was to demonstrate how absurd some of the conclusions people claimed were a result of QM?

Exactly. The whole point of the cat was to point out that quantum mechanics is irrelevant in cases like this, the cat knows damn well whether it is alive or dead. Quantum mechanics only applies to things on a very small scale (with a few exceptions, mostly in extreme conditions, where macroscopic effects can be seen, in superconductors for example). It's exactly the same sort of situation as with relavtivity. Unless you squash the cat down to the size of an atom or accelerate it to the speed of light, neither quantum mechanics or relativity are in any way relevant to its health.

 

[blutoski]

If the experimenter opens the box, but does so inside a sealed room, how does the outside world know if the experimenter knows if the cat is dead or not?
And if he announces the result on the Internet, but nobody tells the universe at large, how do the Martians know if Earth knows if the experimenter knows if the cat is dead or not?

I mean , where does the whole thing stop?

This question has a name: "The von Neumann Catastrophe" aka "The Paradox of Wigner's Friend."

 

[Soapy Sam]

No, no. That's in the Universe Next Door. In this one, it came to me in a fever dream.

 

[Mojo]

I'm so sorry. Didn't mean to make a sore spot worse, even if inadvertently.

Sorry - I was a bit at a low ebb last night after an emergency trip to the vet, and had probably had a beer or two too many.

 

[Mojo]

Exactly. The whole point of the cat was to point out that quantum mechanics is irrelevant in cases like this, the cat knows damn well whether it is alive or dead. Quantum mechanics only applies to things on a very small scale (with a few exceptions, mostly in extreme conditions, where macroscopic effects can be seen, in superconductors for example). It's exactly the same sort of situation as with relavtivity. Unless you squash the cat down to the size of an atom or accelerate it to the speed of light, neither quantum mechanics or relativity are in any way relevant to its health.

Unless it uses homoeopathy...

 

[Third Eye Open]

This month's SEED has an interesting article on acausality: [The Reality Tests: A team of physicists in Vienna has devised experiments that may answer one of the enduring riddles of science: Do we create the world just by looking at it?]

More evidence that we are living in a computer simulation. The computer only 'loads in' the parts of the world that we are looking at.

 

[Soapy Sam]

And it refreshes when you blink.