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> But Bell's theorem and subsequent experiments show it to be false. I think this is an unfounded conclusion. Sure, Bell's theorem and the experiments it inspi

> But Bell's theorem and subsequent experiments show it to be false. I think this is an unfounded conclusion. Sure, Bell's theorem and the experiments it inspired did make lots of contribution to investigation of these foundational problems. But Bell's theorem is about a specific class of probabilistic descriptions. It does not rule out "classical objective reality" unless you restrict meaning of this term so much as to achieve that. Bell himself and many other people who studied the theorem insisted that the theorem is about local hidden variable models, as opposed to nonlocal models. Nothing general is implied about "objective reality". On the experimental side, I am not aware of any experiment that had ruled out objective reality. How would you even test such a nebulous concept experimentally? We can test only specific predictions.

lisper 8y ago
> Nothing general is implied about "objective reality". I disagree. The fact that nature cannot be described by any local hidden variable theory tells you a lot about the nature of reality. There is a real difference between quantum randomness and classical ignorance, and so there is a real difference -- one which you can experimentally measure -- between a particle whose position you don't know because you haven't looked at the result of a measurement, and a particle whose position you don't know because it hasn't been measured at all. It is still, perhaps, debatable whether that difference lies in the particle or in you. But if you want to argue that the difference lies in the particle then the burden is on you to provide an account of when and how the transition happens. No one has succeeded in this, and it's not for want of trying.
- posix_me_less 8y ago
  > The fact that nature cannot be described by any local hidden variable theory tells you a lot about the nature of reality. If assumed to be true, it means one has to use non-local models such as the quantum theory. Those do not explicitly deny objective reality. Perhaps by "objective reality" you actually mean non-contextual hidden variable theory (a theory that assigns well-defined values to all quantum observables at all times). Then yes, those are incompatible with quantum theory predictions. But I would not use the term objective reality. It is unclear and too general. > there is a real difference -- one which you can experimentally measure -- between a particle whose position you don't know because you haven't looked at the result of a measurement, and a particle whose position you don't know because it hasn't been measured at all. Indeed, but this difference has nothing to do with objective reality, and everything to do with the actions of the experimenter or apparatus. In the first option, there is interaction with the particle but experimenter ignores it, and in the second, there is no interaction with the particle. Of course the two situations are different and can result in different results of other measurements.
  - lisper 8y ago
    I am not denying objective reality, I am denying objective classical reality. There is an objective reality, but it is quantum. > the actions of the experimenter or apparatus You are missing the point. Before you can talk about "the actions of the experimenter or the apparatus" you have to tell me what an experimenter or an apparatus is. AFAICT, these are classical objects. But theory tells us, and experiment confirms, that classical objects do not actually exist. So why do they appear to exist? And the answer to that is: decoherence/QIT. The classical world is an illusion, an approximation. A very good approximation, but an approximation nonetheless. If you have a better theory, you should publish it.
    - posix_me_less 8y ago
      > Before you can talk about "the actions of the experimenter or the apparatus" you have to tell me what an experimenter or an apparatus is. This is a very common error of armchair worldview building. Experiment-based sciences such as physics do not work exclusively that way; we can make progress without being so ambitious as to describe and exhaust the whole world in a single scheme. There are things in the real world that have no useful definition or model in physics, such as matter, or experimenter, or apparatus, or measurement. And this is fine, because we know them by experience, and the subject of the investigation is usually something else and rather more specific. > But theory tells us, and experiment confirms, that classical objects do not actually exist. Which theory, which experiment? The studies in quantum foundations showed that explaining expensive experiments with light and particles in the classical terms is hard, and some naive intuitive models, surprisingly, are not consistent with quantum theory. This is very far from "classical objects do not exist". They can easily exist, just with properties that are contextual and interactions that are non-local. And those are categories we are aware of; the possibilities are endless. If you're thinking about the Everettian viewpoint where indeed no classical objects exist, this is just one possible theoretical scheme of thinking, not an experiment-based physical theory. There is Bohmian mechanics, where particles do exist. There are other theories where particles do exist. > If you have a better theory, you should publish it. A better theory in place of "classical objects don't exist" is "don't try to explain the whole world with a single scheme". There is the statistical interpretation due to Einstein, Ballentine and the Bohmian viewpoint which get us useful models and predictions in the realm of atomic physics. There is the classical theory, which gets us understanding of civil engineering, Earth-scale events and celestial mechanics. There is the general theory of relativity, which gets us accurate description of gravity. None of these overlap very well. Neither is explained by Everettian viewpoint.

lisper 8y ago

> Nothing general is implied about "objective reality". I disagree. The fact that nature cannot be described by any local hidden variable theory tells you a lot about the nature of reality. There is a real difference between quantum randomness and classical ignorance, and so there is a real difference -- one which you can experimentally measure -- between a particle whose position you don't know because you haven't looked at the result of a measurement, and a particle whose position you don't know because it hasn't been measured at all. It is still, perhaps, debatable whether that difference lies in the particle or in you. But if you want to argue that the difference lies in the particle then the burden is on you to provide an account of when and how the transition happens. No one has succeeded in this, and it's not for want of trying.

posix_me_less 8y ago
> The fact that nature cannot be described by any local hidden variable theory tells you a lot about the nature of reality. If assumed to be true, it means one has to use non-local models such as the quantum theory. Those do not explicitly deny objective reality. Perhaps by "objective reality" you actually mean non-contextual hidden variable theory (a theory that assigns well-defined values to all quantum observables at all times). Then yes, those are incompatible with quantum theory predictions. But I would not use the term objective reality. It is unclear and too general. > there is a real difference -- one which you can experimentally measure -- between a particle whose position you don't know because you haven't looked at the result of a measurement, and a particle whose position you don't know because it hasn't been measured at all. Indeed, but this difference has nothing to do with objective reality, and everything to do with the actions of the experimenter or apparatus. In the first option, there is interaction with the particle but experimenter ignores it, and in the second, there is no interaction with the particle. Of course the two situations are different and can result in different results of other measurements.
- lisper 8y ago
  I am not denying objective reality, I am denying objective classical reality. There is an objective reality, but it is quantum. > the actions of the experimenter or apparatus You are missing the point. Before you can talk about "the actions of the experimenter or the apparatus" you have to tell me what an experimenter or an apparatus is. AFAICT, these are classical objects. But theory tells us, and experiment confirms, that classical objects do not actually exist. So why do they appear to exist? And the answer to that is: decoherence/QIT. The classical world is an illusion, an approximation. A very good approximation, but an approximation nonetheless. If you have a better theory, you should publish it.
  - posix_me_less 8y ago
    > Before you can talk about "the actions of the experimenter or the apparatus" you have to tell me what an experimenter or an apparatus is. This is a very common error of armchair worldview building. Experiment-based sciences such as physics do not work exclusively that way; we can make progress without being so ambitious as to describe and exhaust the whole world in a single scheme. There are things in the real world that have no useful definition or model in physics, such as matter, or experimenter, or apparatus, or measurement. And this is fine, because we know them by experience, and the subject of the investigation is usually something else and rather more specific. > But theory tells us, and experiment confirms, that classical objects do not actually exist. Which theory, which experiment? The studies in quantum foundations showed that explaining expensive experiments with light and particles in the classical terms is hard, and some naive intuitive models, surprisingly, are not consistent with quantum theory. This is very far from "classical objects do not exist". They can easily exist, just with properties that are contextual and interactions that are non-local. And those are categories we are aware of; the possibilities are endless. If you're thinking about the Everettian viewpoint where indeed no classical objects exist, this is just one possible theoretical scheme of thinking, not an experiment-based physical theory. There is Bohmian mechanics, where particles do exist. There are other theories where particles do exist. > If you have a better theory, you should publish it. A better theory in place of "classical objects don't exist" is "don't try to explain the whole world with a single scheme". There is the statistical interpretation due to Einstein, Ballentine and the Bohmian viewpoint which get us useful models and predictions in the realm of atomic physics. There is the classical theory, which gets us understanding of civil engineering, Earth-scale events and celestial mechanics. There is the general theory of relativity, which gets us accurate description of gravity. None of these overlap very well. Neither is explained by Everettian viewpoint.