Schroedinger's cat is always dead

PhilGoetz

Suppose you believe in the Copenhagen interpretation of quantum mechanics. Schroedinger puts his cat in a box, with a device that has a 50% chance of releasing a deathly poisonous gas. He will then open the box, and observe a live or dead cat, collapsing that waveform.

But Schroedinger's cat is lazy, and spends most of its time sleeping. Schroedinger is a pessimist, or else an optimist who hates cats; and so he mistakes a sleeping cat for a dead cat with probability P(M) > 0, but never mistakes a dead cat for a living cat.

So if the cat is dead with probability P(D) >= .5, Schroedinger observes a dead cat with probability P(D) + P(M)(1-P(D)).

If observing a dead cat causes the waveform to collapse such that the cat is dead, then P(D) = P(D) + P(M)(1-P(D)). This is possible only if P(D) = 1.

If you don't say that only conscious agents can collapse waveforms, then you have to agree that something in the box collapses the waveform as seen from inside the box, while it's still uncollapsed to Schroedinger. And Schroedinger's opening the box collapses that waveform for him; but it is still uncollapsed for someone outside the room. This seems like it might be equivalent to many worlds - all possibilities already exist; you just haven't chosen which one you're going to access until you open the box.

But if you do say that only conscious agents can collapse waveforms, then it's something about their mental processes that does the collapsing. This could mean their beliefs matter. And then, the cat is always dead.

ADDED: People. Read the entire post before responding. I am not claiming that the cat is always dead. I am not claiming that consciousness collapses waveforms. I am claiming that there are only 2 known alternatives:

Interactions collapse waveforms, regardless of whether conscious entities are involved. It is not possible, under this view, for any waveform to be either collapsed or not collapsed, because there will be some viewpoints from which it has collapsed, and some from which it hasn't. So this appears to be equivalent to many-worlds.
Consciousness collapses waveforms. Leading to weirdness such as, potentially, the cat always being dead.

If you can't produce another alternative, and you don't believe in many-worlds, you owe me an upvote.

Finally, this post is supposed to be fun! You are crushing all whimsy and playfulness on LessWrong when you pile downvotes like bricks on anything playful because it does not provide a complete and satisfactory resolution.

So if the cat is dead with probability P(D) >= .5, Schroedinger observes a dead cat with probability P(D) + P(M)(1-P(D)).

If observing a dead cat causes the waveform to collapse such that the cat is dead, then P(D) = P(D) + P(M)(1-P(D)). This is possible only if P(D) = 1.

Interactions collapse waveforms, regardless of whether conscious entities are involved. It is not possible, under this view, for any waveform to be either collapsed or not collapsed, because there will be some viewpoints from which it has collapsed, and some from which it hasn't. So this appears to be equivalent to many-worlds.
Consciousness collapses waveforms. Leading to weirdness such as, potentially, the cat always being dead.

If you can't produce another alternative, and you don't believe in many-worlds, you owe me an upvote.

Thanks for the additional info and explanation. I have some books about QM on my desk that I really ought to study in depth...

I should mention though that what you state about needing only a single-world is in direct contradiction to what EY asserts: "Whatever the correct theory is, it has to be a many-worlds theory as opposed to a single-world theory or else it has a special relativity violating, non-local, time-asymmetric, non-linear and non-measurepreserving collapse process which magically causes blobs of configuration space to instantly vanish [...] I don't see how one is permitted to hold out any hope whatsoever of getting the naive single world back."

My level of understanding is insufficient to debate QM on a serious level, but I'd be very interested in a high level exchange about QM here on LW. If you disagree with Eliezer's views on QM I think it is a good thing to say that explicitly, because when you study the different interpretations it's important to keep them apart (the subject is confusing[1] enough as is).

[1] a property of yours truly

My level of understanding is insufficient to debate QM on a serious level, but I'd be very interested in a high level exchange about QM here on LW. If you disagree with Eliezer's views on QM I think it is a good thing to say that explicitly, because when you study the different interpretations it's important to keep them apart (the subject is confusing[1] enough as is).

I agree that such an exchange would be useful. Unfortunately it would be hard to have with Mitchell_Porter because of the reputation he has gained for his evangelism of qualia and Quantum... (read more)

4Mitchell_Porter15y

I have posted here, on this topic (MWI), perhaps a hundred times. There are many comments from me in the Quantum Physics sequence. Two years ago I made a top-level post in favor of the rather anodyne position that MWI is not the favored interpretation, it's just one among many. Now I would take a much stronger line, that MWI has very little going for it. It cannot even reproduce the predictions of QM, which derive from the "Born rule" that MWI discards, in favor of having only the Schrodinger equation. Instead, the ideological stance is adopted that Only The Wavefunction Exists, and the recovery of the Born probabilities, which contain the whole of QM's empirical content, is left for future research. Or, even worse, it's just assumed. But this is a problem because, if you count the branches of the wavefunction, they should all count for the same, which would mean that the probabilities of all outcomes are equal, which would mean that MWI is falsified. Robin Hanson dreamed up an idea for how to get the right multiplicities of worlds, but it means that the individual worlds are somewhat messy superpositions. There are various other claims in the physics and philosophy literature of having recovered the Born rule, none of them satisfactory. One should be aware, especially in the era of arxiv.org - which is not peer-reviewed - that bad papers are available in abundance; though in this area, even good physicists produce bad papers advancing bogus arguments. In the quotation above, Eliezer is once again assuming that wavefunctions exist and that the only alternative to MWI is wavefunction collapse. "Blobs of configuration space" don't "vanish" if they were only ever domains in a probability distribution; see my remarks elsewhere on this page on the necessity of understanding that wavefunctions need not exist. I have made these points in the past ( 1 2 3 ). Let me unearth a few other discussions for you... Counterfactual measurement. A supposed derivation of the Born rul

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