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Schrödinger's cat

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the paradox of Schrödinger's cat

Well, there isn't one. Reality is not determined by the observer or the observer's knowledge. The notion that a probability function is somehow a real physical property of nature is entirely incoherent.

Edited by brian0918
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I'm not looking for a long discussion. I just want to know the Objectivist's rebuttal to the paradox of Schrödinger's cat.

Interactions with other existents form the boundary conditions of any particular existent. There is nothing special about human consciousness that collapses wavefunctions, the cat itself or the interior surface of the box do so as well.

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Schrödinger himself described the thought experiment as an example of the absurdness of quantum mechanics and the mathematics necessary to describe quantum states. His intentions were that the mathematics had to have been flawed and gave an example of how it contradicts reality. However, many people have seemed to have taken his thought experiment to mean the exact opposite; if your calculations lead to bizarre conclusion that contradict reality then your math must be correct and its reality that must be wrong.

Schrodinger was trying to demonstrate that if your conclusions lead to an obvious contradiction then your premise must be incorrect.

Edited by Rearden_Steel
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Schrodinger was trying to demonstrate that if your conclusions lead to an obvious contradiction then your premise must be incorrect.
Schrödinger was trying to apply QM to a specific system. The indisputably convincing method would have been to write and solve the QM equations for that system. But he couldn't and didn't do this, because the system was macroscopic, that is extremely complex. Therefore, he didn't make any quantum mechanical computation, but only a speculation ("thought experiment") about what the result of the computation would be.

But in order to arrive at his paradoxical conclusion, he had to make a lot of assumptions: that it is legitimate to apply QM to such a system, that the system is indeed described by a wave function (and not by a density matrix, for example), that the interference between the "dead" and "alive" states is not null (this is the precondition of the paradox), etc.

Until all these assumptions are confirmed to be true, the claim that the QM itself is the culprit of the paradox is premature.

There are good reasons to believe that, for example, the interference term is in fact null, because the two states are so radically different, that they never overlap (overlapping in the space of the quantum parameters is necessary for interference).

Sasha

Edited by AlexL
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There are many interpretations of quantum mechanics, many of which do not contain anything like Schrodinger's Cat. The Bohm interpretation, the transactional interpretation, and the many world interpretation are my personal favorites, just from a conceptual standpoint. In any case, very few physicists subscribe to the Copenhagen interpretation anymore. Decoherence is in vogue now. In fact, apparently a few days ago a few physicist's published a paper describing how gravity waves might serve the purpose of causing decoherence and/or wavefunction collapse in macroscopic objects, thereby keeping the macroscopic world classical, even for Schrodinger's Cat. In any case, my point is that quantum mechanics has many interpretations, only some of which are obviously wrong like the Copenhagen interpretation. And, lets not forget, quantum mechanics isn't a full description of the material world, so there may be effects which we have not been able to see yet. And, finally, there may be another, better, theory out there, waiting to be discovered.

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Couldn't an experiment be performed? Not with a cat, of course, but with some other, lesser, type of animal, like a lab rat or a fly.

In fact, it could never be performed. Determining the truth of the claim requires one to obtain knowledge without obtaining knowledge. That's why it's not science.

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"Determining the truth of the claim requires one to obtain knowledge without obtaining knowledge. That's why it's not science." - brian

This nails it for me. Because the issue I have is how do we determine whether the cat is alive or dead (Now I understand it is not possible to). And The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead is a contradiction.

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"Determining the truth of the claim requires one to obtain knowledge without obtaining knowledge. That's why it's not science." - brian

This nails it for me. Because the issue I have is how do we determine whether the cat is alive or dead (Now I understand it is not possible to). And The Copenhagen interpretation of quantum mechanics implies that after a while, the cat is simultaneously alive and dead is a contradiction.

It's a simple inversion of reality, primacy of consciousness over primacy of existence. Contrary to what they would have you believe, reality is not determined by our knowledge (knowledge of what? - blank out).

Edited by brian0918
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Couldn't an experiment be performed? Not with a cat, of course, but with some other, lesser, type of animal, like a lab rat or a fly.

Rats and flies are still much too large, but such experiments have been done successfully with atoms and even relatively large molecules. Those can be brought in a superposition of states, also called 'cat states'. For larger systems the phenomenon of decoherence makes the existence of such states practically impossible. That is also the modern answer to the riddle of Schrödinger's cat: QM does not predict that a macroscopic system like a cat can exist in a superposition of two different states (alive and dead), it will always be either alive or dead. At Schrödinger's time this was not yet known, but today the fate of his cat is no longer a riddle, it has been solved years ago. But of course popular books still like to present such old ideas because they sound so mysterious. The same for the problem of a consciousness that seems to seal the fate of the cat (Wigner's friend theories), thanks to the decoherence explanation consciousness is no longer needed in the explanation, the cat is already dead or alive before anyone looks, in accordance with our macroscopic intuition (which works well for macroscopic systems, but fails at atomic scales, as we've never experienced those directly in our lives).

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