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The most sensible explanation I've heard came from sir Arthur Eddington. His claim (roughly) is that probabilities in quantum theory model our knowledge of the

The most sensible explanation I've heard came from sir Arthur Eddington. His claim (roughly) is that probabilities in quantum theory model our knowledge of the quantum system, rather than indicating anything intrinsically probabilistic in the system itself. In that case, our knowledge allows for more possibilities before making a measurement (observation), and collapses into something more definite after the measurement. That's probably not the best description, but I think the basic idea about modeling knowledge makes a lot of sense. Eddington was primarily a physicist, but also a philosopher. I read this account of his in 'The Philosophy of Physical Science.' If I'm not mistaken, it's pretty much in line with the 'Pilot Wave' interpretation which is getting more attention these days.

Koshkin 9y ago
The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. It does not. Anything we measure is essentially an artifact of the measurement process itself, and the randomness of the result comes from bringing together two incompatible worlds - quantum and classical. All we are left with at the quantum level is wave-functions; but what matters for us is, of course, what we can experience, being ourselves classical, and QM has so far provided us with a perfectly good way of finding that out.
- westoncb 9y ago
  Would you mind either arguing for the superiority of that interpretation or showing flaws with the alternative I pointed out? I know that what you've stated is nearly cannon at the moment, but the issue isn't actually settled, which is why a discussion of it here is still potentially interesting, and why merely re-asserting the supposed truth of the most common interpretation isn't. Edit: in other words, when you say: > The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. It does not. You are only asserting that's the case, not defending it. The rest of your post operates on the opposite, undefended assumption that a quantum system does not possess a certain property prior to or independent from a measurement.
  - Koshkin 9y ago
    It is untenable even from a purely philosophical standpoint that we could bring all this classical baggage into the world of which we already know well enough to behave nothing like what we have seen before and hope that we would end up with something other than a mess in our understanding what is really going on. All we have ended up with is a theory telling us how a quantum system interacts with what we must think of as a classical object so we could conveniently, albeit probabilistically, extrapolate the notions (e.g. those of "properties") of the familiar classical world to the world that is and will forever remain out of reach to our senses.
    - westoncb 9y ago
      If I understand correctly you're saying the interpretation I've pointed out is not tenable because it carries classical baggage, and yet we've already observed quantum systems to not behave classically, so if we proceed that way we get a mess. But the whole point of the alternative interpretation I pointed out is a way of reconciling the observations with an essentially classical world (at least in the sense that there is a single objective reality which exists independent of observation)—do you see a way in which it fails to do that? My understanding is that considering the probabilistic aspect of the theory to be modeling our knowledge of the system instead, successfully accounts for the fundamentally 'non-classical' observations. It just seems hasty to throw out such a seemingly well-supported hypothesis (single objective reality independent of viewer), if there are two effective interpretations, one of which conflicts with it, the other of which does not. From my reading, the primary reasons for the mainstream physics community having adopted the stance which competes with the 'objective reality' hypothesis (i.e. Many Worlds or Copenhagen interpretations), are historical accident and political, while the intrinsic merits of the alternatives are near equivalent.
      - Koshkin 9y ago
        You seem to be conflating 'being real', or 'objective', with 'being classical', or 'possessing measurable properties prior to measurement'. That is the mistake I was arguing against, and the Copenhagen interpretation is what keeps one from making it.
- platz 9y ago
  QM is a model. it may have some basis in reality, but we don't know if "amplitudes" are fundamentally real or not. Just because it predicts outcomes (probabilistically!) very accurately doesn't mean we have the full picture. (how does gravity fit into this picture? it's completely let out of QM!)
  - goatlover 9y ago
    It definitely has some basis in reality, because it fits experimental results. The exact nature of that fit is up for debate, but the experiments are certainly part of the real world we try to make sense of.
- BoiledCabbage 9y ago
  > The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. Your comment is wrong. In the 3rd of the 3 interpretations of QM (Debroglie Bohm) this is exactly the case. The world is at all times in a well defined state. We just don't know it until we measure so we use probabilities to desceibe. All 3 QM interpretations are mathematically indistinguishable.
  - akvadrako 9y ago
    The point is a bit more subtle that than. Both WMI and Bohm's theory are deterministic, so the world is in a well-defined state. But any property we can measure is not well-defined, in the sense that before we have actually measured it, it doesn't exist.
coldtea 9y ago
>The most sensible explanation I've heard came from sir Arthur Eddington. His claim (roughly) is that probabilities in quantum theory model our knowledge of the quantum system, rather than indicating anything intrinsically probabilistic in the system itself. That's counter to a century of experiments and theories. If that was the case, QM would be a trivial classical theory.
- westoncb 9y ago
  You should check out the Debroglie Bohm/pilot wave interpretation. What I have described does not go counter the experimental data we have.
  - lmm 9y ago
    The pilot wave does all the work of physical reality in that interpretation. Imagining there is this extra downstream classical reality is just a bunch of extra work for no benefit, and should be discarded per Occam.
alok-g 9y ago
>> His claim (roughly) is that probabilities in quantum theory model our knowledge of the quantum system, rather than indicating anything intrinsically probabilistic in the system itself. Note "our" knowledge there. If I am making a measurement, and you are disconnected to me, how and when does it become our knowledge? How is it that one human measuring results in a collapse, with no other human knowing about it. Does something more happen when this first human tells about it to others?

Koshkin 9y ago

The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. It does not. Anything we measure is essentially an artifact of the measurement process itself, and the randomness of the result comes from bringing together two incompatible worlds - quantum and classical. All we are left with at the quantum level is wave-functions; but what matters for us is, of course, what we can experience, being ourselves classical, and QM has so far provided us with a perfectly good way of finding that out.

westoncb 9y ago
Would you mind either arguing for the superiority of that interpretation or showing flaws with the alternative I pointed out? I know that what you've stated is nearly cannon at the moment, but the issue isn't actually settled, which is why a discussion of it here is still potentially interesting, and why merely re-asserting the supposed truth of the most common interpretation isn't. Edit: in other words, when you say: > The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. It does not. You are only asserting that's the case, not defending it. The rest of your post operates on the opposite, undefended assumption that a quantum system does not possess a certain property prior to or independent from a measurement.
- Koshkin 9y ago
  It is untenable even from a purely philosophical standpoint that we could bring all this classical baggage into the world of which we already know well enough to behave nothing like what we have seen before and hope that we would end up with something other than a mess in our understanding what is really going on. All we have ended up with is a theory telling us how a quantum system interacts with what we must think of as a classical object so we could conveniently, albeit probabilistically, extrapolate the notions (e.g. those of "properties") of the familiar classical world to the world that is and will forever remain out of reach to our senses.
  - westoncb 9y ago
    If I understand correctly you're saying the interpretation I've pointed out is not tenable because it carries classical baggage, and yet we've already observed quantum systems to not behave classically, so if we proceed that way we get a mess. But the whole point of the alternative interpretation I pointed out is a way of reconciling the observations with an essentially classical world (at least in the sense that there is a single objective reality which exists independent of observation)—do you see a way in which it fails to do that? My understanding is that considering the probabilistic aspect of the theory to be modeling our knowledge of the system instead, successfully accounts for the fundamentally 'non-classical' observations. It just seems hasty to throw out such a seemingly well-supported hypothesis (single objective reality independent of viewer), if there are two effective interpretations, one of which conflicts with it, the other of which does not. From my reading, the primary reasons for the mainstream physics community having adopted the stance which competes with the 'objective reality' hypothesis (i.e. Many Worlds or Copenhagen interpretations), are historical accident and political, while the intrinsic merits of the alternatives are near equivalent.
    - Koshkin 9y ago
      You seem to be conflating 'being real', or 'objective', with 'being classical', or 'possessing measurable properties prior to measurement'. That is the mistake I was arguing against, and the Copenhagen interpretation is what keeps one from making it.
platz 9y ago
QM is a model. it may have some basis in reality, but we don't know if "amplitudes" are fundamentally real or not. Just because it predicts outcomes (probabilistically!) very accurately doesn't mean we have the full picture. (how does gravity fit into this picture? it's completely let out of QM!)
- goatlover 9y ago
  It definitely has some basis in reality, because it fits experimental results. The exact nature of that fit is up for debate, but the experiments are certainly part of the real world we try to make sense of.
BoiledCabbage 9y ago
> The mistake in this line of thinking is in the tacit assumption that a quantum system possesses a certain property prior to or independent from a measurement. Your comment is wrong. In the 3rd of the 3 interpretations of QM (Debroglie Bohm) this is exactly the case. The world is at all times in a well defined state. We just don't know it until we measure so we use probabilities to desceibe. All 3 QM interpretations are mathematically indistinguishable.
- akvadrako 9y ago
  The point is a bit more subtle that than. Both WMI and Bohm's theory are deterministic, so the world is in a well-defined state. But any property we can measure is not well-defined, in the sense that before we have actually measured it, it doesn't exist.

coldtea 9y ago

>The most sensible explanation I've heard came from sir Arthur Eddington. His claim (roughly) is that probabilities in quantum theory model our knowledge of the quantum system, rather than indicating anything intrinsically probabilistic in the system itself. That's counter to a century of experiments and theories. If that was the case, QM would be a trivial classical theory.

westoncb 9y ago
You should check out the Debroglie Bohm/pilot wave interpretation. What I have described does not go counter the experimental data we have.
- lmm 9y ago
  The pilot wave does all the work of physical reality in that interpretation. Imagining there is this extra downstream classical reality is just a bunch of extra work for no benefit, and should be discarded per Occam.

alok-g 9y ago

>> His claim (roughly) is that probabilities in quantum theory model our knowledge of the quantum system, rather than indicating anything intrinsically probabilistic in the system itself. Note "our" knowledge there. If I am making a measurement, and you are disconnected to me, how and when does it become our knowledge? How is it that one human measuring results in a collapse, with no other human knowing about it. Does something more happen when this first human tells about it to others?