5 ms·

From other sections it seems clear that the author is a devout adherent of The Copenhagen Interpretation, aka objective wavefunction collapse; this is a close r

From other sections it seems clear that the author is a devout adherent of The Copenhagen Interpretation, aka objective wavefunction collapse; this is a close relative of the baseline non-Interpretation “Shut Up And Calculate.” People like that are generally utterly unmoved by anything short of a rigorous mathematical formulation, which works for them in QM where “rigorous mathematical formulation” is pretty much all of what matters. While I respect the adherence to formalism, the notion that our imperfect view of QM (it doesn’t mesh with GTR after all) represents an ontology to hang your hat on is less respectable. Wavefunction collapse seems like a massive cop-out, and it won’t satisfy anyone except the most rigid logical positivist. Something like MWI is on the other end of the philosophical spectrum, so the hostility is not surprising. At the end of the day though, it comes down to this: If you want to build something based on QM, you need someone like this guy. If you want to satisfy your human need for an ontology, he won’t help you.

Retra 9y ago
I would argue that expecting QM to satisfy a human need for ontology is about as useful as expecting general relativity to satisfy a human need for sexual gratification. It's easy to find a way to be dissatisfied: just want more out of things. But it doesn't make sense to always expect to get what you want. Some things simply won't provide. As long as QM is providing a means to achieve accurate predictions and precise language, it is doing its job perfectly. It is not responsible for satisfying a (potentially irrational) need for ontological interpretation.
- IntronExon 9y ago
  And if QM and GTR agreed in their predictions I’d be right there with you, telling people to suck it up. I’m a bit there with you anyway, because nature has no obligation to us, and the predictive power of QM is just incredible. But... in the absence of a complete theory including gravity, there are huge gaps. It’s just human nature to try and fill those gaps, for better or worse. For worse when people stuff those gaps with god, but for better when they’re uncomfortable with overly pat explanations like objective collapse.
  - Koshkin 9y ago
    > nature has no obligation to us This is an excellent point indeed, but what if it also applies to the disagreement between QM and GR? That is, does Nature have an obligation that QM and GR, both being mere reflections, in the human mind, of its particular aspects, should ever become in agreement with each other? What if mathematics (the human logic) can in principle only provide models that are local approximations of reality?
    - IntronExon 9y ago
      It’s possible, but maybe not likely. I’ll tell you though, if reality is that unpredictable, thst unfriendly to rules, expect a rash of suicides in the physics community the day it’s confirmed.
      - whatshisface 9y ago
        These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical), and innocent bystanders posing reasonable what-if questions that really can't be answered with (present) empirical knowledge. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else. Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms.
        IntronExon 9y ago
        These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical) That seems needlessly judgmental. ...and innocent bystanders posing reasonable what-if questions... They’re rarely reasonable. You get a lot of questions which are philosophical in nature, but which people believe are scientific. “What is time like for a photon?” “What was there before the Big Bang?” “What is spacetime expanding into?” “What’s inside of the event horizon of a black hole?” “Why are the physical constants what they are?” When you give the scientific answer, “Bad question, like asking what’s North of The North Pole?” People are unhappy. Plus you’re a dick, because you can figure out what they’re asking and try to give a complete and accessible answer, complete with warnings as to the philosophical/metaphysical nature of both question and answer. ...that really can't be answered with (present) empirical knowledge. Often the questions themselves are essentially unanswerable in principle. It’s not easy to ask good, relevant, scientific questions about QM or STR/GTR. The lack of knowledge is more of a factor when the questions are insightful. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else. Depends on the audience... try that in a rigorous environment and be crucified, but on HN the rigor is absent. It’s a good thing too, because it’s Hacker News, not PhysicsForums. Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms. And? You seem to be complaining that on a site full of non-physicists, people don’t act like physicists. Besides, ontologies of QM are philosophical, not scientific, and hardly limited to laypeople.
- naasking 9y ago
  > As long as QM is providing a means to achieve accurate predictions and precise language, it is doing its job perfectly. It is not responsible for satisfying a (potentially irrational) need for ontological interpretation. What a strange position. Clearly some things exist, since we're here, we're discussing the subject itself, and so on. Defining what "to exist" actually means would seem to be the central rational pursuit of physics. This is an ontology. The focus on prediction is merely a proxy to the ultimate goal.
balfirevic 9y ago
I am not a physicist, but this seems backwards to me. If anything, it is the Copenhagen interpretation that comes with the largest amount of extra-mathematical baggage while many-worlds interpretation came out of effort to add the least amount of additional assumptions on top of the math.
- millstone 9y ago
  The price that MWI pays for this minimalism is that it loses some contact with reality, i.e. physical experiments. Basic physical observations like "some measurements are non-deterministic" are quite difficult to explain in the MWI. Reality is inconvenient.
  - fossuser 9y ago
    I don't think that's true - it takes that into account, it just looks like it collapses because you're in the world with that state - not seeing the entire picture. MWI accounts for it appearing that way while in actuality the wave function never collapses. Max Tegmark gives a pretty accessible description of this in his book - Our Mathematical Universe, and Eliezer Yudkowsky does a decent job with a general explanation here (though he avoids talking about MWI): http://lesswrong.com/lw/pd/configurations_and_amplitude/ http://lesswrong.com/lw/pd/configurations_and_amplitude/ I think the Copenhagen interpretation is now considered wrong by most physicists. It's strange to me that it was ever really thought of as true - though it makes sense that it would look like what's happening at first. It's less that MWI is a predictive theory and more that MWI is something that comes out as a result of the theory's prediction (Schrodinger's wave equation that doesn't collapse).
    - naasking 9y ago
      > I think the Copenhagen interpretation is now considered wrong by most physicists. Recent surveys suggest that most practicing physicists still pick Copenhagen as their default, mainly because that's what they were taught and QM foundations have no implication on their actual work.
phayes 9y ago
"Objective wavefunction collapse" is not a good "aka" for the CI. There is a great deal of objectivity in it but there's an essential element of subjectivity (shared by neo-CI descendants of the CI such as QBism and Rovelli's relational interpretation) too. Streater's discussion of EPR explains why: https://web.archive.org/web/20151117174141/http://www.mth.kcl.ac.uk/~streater/EPR.html https://web.archive.org/web/20151117174141/http://www.mth.kc... Broadly speaking, the CI and its "radical" psi-epistemic* relatives interpret QM as (generalised) probability theory applied to mechanics: https://telescoper.wordpress.com/2017/06/23/the-quantum-mechanics-of-voting/#comment-219425 https://telescoper.wordpress.com/2017/06/23/the-quantum-mech... It's hardly a cop-out. See e.g. Rovelli's take on what the ontological ramifications are: https://arxiv.org/abs/1712.02894 https://arxiv.org/abs/1712.02894 * https://www.sciencedirect.com/science/article/pii/S1355219815300095 https://www.sciencedirect.com/science/article/pii/S135521981...

Retra 9y ago

I would argue that expecting QM to satisfy a human need for ontology is about as useful as expecting general relativity to satisfy a human need for sexual gratification. It's easy to find a way to be dissatisfied: just want more out of things. But it doesn't make sense to always expect to get what you want. Some things simply won't provide. As long as QM is providing a means to achieve accurate predictions and precise language, it is doing its job perfectly. It is not responsible for satisfying a (potentially irrational) need for ontological interpretation.

IntronExon 9y ago
And if QM and GTR agreed in their predictions I’d be right there with you, telling people to suck it up. I’m a bit there with you anyway, because nature has no obligation to us, and the predictive power of QM is just incredible. But... in the absence of a complete theory including gravity, there are huge gaps. It’s just human nature to try and fill those gaps, for better or worse. For worse when people stuff those gaps with god, but for better when they’re uncomfortable with overly pat explanations like objective collapse.
- Koshkin 9y ago
  > nature has no obligation to us This is an excellent point indeed, but what if it also applies to the disagreement between QM and GR? That is, does Nature have an obligation that QM and GR, both being mere reflections, in the human mind, of its particular aspects, should ever become in agreement with each other? What if mathematics (the human logic) can in principle only provide models that are local approximations of reality?
  - IntronExon 9y ago
    It’s possible, but maybe not likely. I’ll tell you though, if reality is that unpredictable, thst unfriendly to rules, expect a rash of suicides in the physics community the day it’s confirmed.
    - whatshisface 9y ago
      These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical), and innocent bystanders posing reasonable what-if questions that really can't be answered with (present) empirical knowledge. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else. Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms.
      - IntronExon 9y ago
        These discussions are always composed of people who don't know very much laying down philosophical assertions (that they very rarely realize are philosophical) That seems needlessly judgmental. ...and innocent bystanders posing reasonable what-if questions... They’re rarely reasonable. You get a lot of questions which are philosophical in nature, but which people believe are scientific. “What is time like for a photon?” “What was there before the Big Bang?” “What is spacetime expanding into?” “What’s inside of the event horizon of a black hole?” “Why are the physical constants what they are?” When you give the scientific answer, “Bad question, like asking what’s North of The North Pole?” People are unhappy. Plus you’re a dick, because you can figure out what they’re asking and try to give a complete and accessible answer, complete with warnings as to the philosophical/metaphysical nature of both question and answer. ...that really can't be answered with (present) empirical knowledge. Often the questions themselves are essentially unanswerable in principle. It’s not easy to ask good, relevant, scientific questions about QM or STR/GTR. The lack of knowledge is more of a factor when the questions are insightful. Like politics, the content of what is said is dominated by the dynamics of the discussion, with English skills "winning" arguments more often than anything else. Depends on the audience... try that in a rigorous environment and be crucified, but on HN the rigor is absent. It’s a good thing too, because it’s Hacker News, not PhysicsForums. Physics is already approximate; experiments don't have access to infinity significant figures. If you'd prefer a more complicated example then ask anyone who has ever calculated a QED problem to less than infinity terms. And? You seem to be complaining that on a site full of non-physicists, people don’t act like physicists. Besides, ontologies of QM are philosophical, not scientific, and hardly limited to laypeople.
naasking 9y ago
> As long as QM is providing a means to achieve accurate predictions and precise language, it is doing its job perfectly. It is not responsible for satisfying a (potentially irrational) need for ontological interpretation. What a strange position. Clearly some things exist, since we're here, we're discussing the subject itself, and so on. Defining what "to exist" actually means would seem to be the central rational pursuit of physics. This is an ontology. The focus on prediction is merely a proxy to the ultimate goal.

balfirevic 9y ago

I am not a physicist, but this seems backwards to me. If anything, it is the Copenhagen interpretation that comes with the largest amount of extra-mathematical baggage while many-worlds interpretation came out of effort to add the least amount of additional assumptions on top of the math.

millstone 9y ago
The price that MWI pays for this minimalism is that it loses some contact with reality, i.e. physical experiments. Basic physical observations like "some measurements are non-deterministic" are quite difficult to explain in the MWI. Reality is inconvenient.
- fossuser 9y ago
  I don't think that's true - it takes that into account, it just looks like it collapses because you're in the world with that state - not seeing the entire picture. MWI accounts for it appearing that way while in actuality the wave function never collapses. Max Tegmark gives a pretty accessible description of this in his book - Our Mathematical Universe, and Eliezer Yudkowsky does a decent job with a general explanation here (though he avoids talking about MWI): http://lesswrong.com/lw/pd/configurations_and_amplitude/ http://lesswrong.com/lw/pd/configurations_and_amplitude/ I think the Copenhagen interpretation is now considered wrong by most physicists. It's strange to me that it was ever really thought of as true - though it makes sense that it would look like what's happening at first. It's less that MWI is a predictive theory and more that MWI is something that comes out as a result of the theory's prediction (Schrodinger's wave equation that doesn't collapse).
  - naasking 9y ago
    > I think the Copenhagen interpretation is now considered wrong by most physicists. Recent surveys suggest that most practicing physicists still pick Copenhagen as their default, mainly because that's what they were taught and QM foundations have no implication on their actual work.

phayes 9y ago

"Objective wavefunction collapse" is not a good "aka" for the CI. There is a great deal of objectivity in it but there's an essential element of subjectivity (shared by neo-CI descendants of the CI such as QBism and Rovelli's relational interpretation) too. Streater's discussion of EPR explains why: https://web.archive.org/web/20151117174141/http://www.mth.kcl.ac.uk/~streater/EPR.html https://web.archive.org/web/20151117174141/http://www.mth.kc... Broadly speaking, the CI and its "radical" psi-epistemic* relatives interpret QM as (generalised) probability theory applied to mechanics: https://telescoper.wordpress.com/2017/06/23/the-quantum-mechanics-of-voting/#comment-219425 https://telescoper.wordpress.com/2017/06/23/the-quantum-mech... It's hardly a cop-out. See e.g. Rovelli's take on what the ontological ramifications are: https://arxiv.org/abs/1712.02894 https://arxiv.org/abs/1712.02894 * https://www.sciencedirect.com/science/article/pii/S1355219815300095 https://www.sciencedirect.com/science/article/pii/S135521981...