9 ms·

The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. The article seems really upset by that, but is it any reason to label

The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. The article seems really upset by that, but is it any reason to label it a lost cause? I guess you can’t really study it or preform experiments on it but that shouldn’t be any suprise for any interpretation of quantum mechanics. I might be missing something here...

ajkjk 9y ago
After skimming the whole thing, I was relieved to see that the argument against Many Worlds was the only one I considered invalid. It took the form of "It's not even a testable theory", rather than "it has mathematical deficiencies". Well, of course, no one's saying it's testable necessarily, but for various aesthetic and intuitive reasons it still seems valid. Just don't expect predictions from it and you'll be fine.
- whatshisface 9y ago
  Valid and true are two very different things - and we've seen from history that the human brain can be lead into believing that essentially anything is intuitive or aesthetic.
  - ajkjk 9y ago
    Sure, hence the reason physicists tend to say MWI is valid and good, rather than 'true'.
- naasking 9y ago
  > After skimming the whole thing, I was relieved to see that the argument against Many Worlds was the only one I considered invalid. You should consider the Bohmian criticisms invalid as well then. Many have argued that de Broglie-Bohm is "many worlds in disguise", so if the criticisms the author levels against Bohmian mechanics are true, then they apply to MWI, but if they don't apply to MWI, then they don't apply to Bohmian mechanics either. Not because they are the same theory, because they are not ontologically the same, but the formalisms are interchangeable.
  - ajkjk 9y ago
    Oh yeah. Probably, yeah. I glossed over that one because its criticisms were strangely technical for a theory that, iirc, just rephrases regular quantum theory.
IntronExon 9y ago
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.
omazurov 9y ago
> The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. How does the many worlds interpretation INTERPRET the Born rule? Shouldn't that be a key feature of any QM interpretation?
whereismypwd 9y ago
His argument is that it's useless as a research topic because you cannot perform experiments about it. You can still believe it if you like, but its slightly less useful than trying to convince everyone to replace pi with tau..
- hawkice 9y ago
  I mean, the pi/tau thing is _purely_ aesthetic. That's a big waste of time for sure. Having a more coherent metaphor for the evolution of quantum systems might help with physical insight, though. If e.g. the universe isn't differentiable across spacetime, we need a better understanding of GR. Many worlds insists it is differentiable (and local), so thinking that way could help integrate the two. It isn't an important thing, but pi/tau is an unrealistically silly thing to compare it to.
- gizmo686 9y ago
  QM is a mathematical model. Many worlds is an intuition to understand that model. There is a pedagogical question on if many worlds is a useful mental model to have. There is also a philosophical question of if many worlds better captures the essence of the model relative to Copenhagen. We can also flip it around. Why should we think of QM in terms of the Copenhagen when it makes to testable predictions.
  - millstone 9y ago
    Wouldn't you consider the Born rule to be a testable prediction (though in an admittedly weak sense of simply being postulated)? If the Born rule were found to be violated, it would invalidate Copenhagen but not MWI, which IMO means Copenhagen is more falsifiable.
    - naasking 9y ago
      > If the Born rule were found to be violated, it would invalidate Copenhagen but not MWI, which IMO means Copenhagen is more falsifiable. All quantum mechanical interpretations depend upon the Born rule. A violation of the Born rule would rule them all out, except perhaps Bohmian mechanics which allows the possibility of non-equilibrium states, but we have no idea if those can be created.
zombieprocesses 9y ago
If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable, then the theory isn't truly scientific. This is a major issue/concern in advanced theoretical physics. Is it really physics if you can't experiment or is it just mathematics? The foundation of science is falsiability within the scientific method. It's the core tenet.
- sgillen 9y ago
  For sure, I’m by trying to say it’s a real theory, it’s just a way to interpret the quantum mechanics that we can test in a way that provide us with some sort of intuition when working with the physics.
- jamesrcole 9y ago
  But what if, after spending more time working on and thinking about it, someone does find a way to make predictions based on it or on an extension/modification of it? If that's a possibility (I can't say, I'm not a physicist) then I'd be a mistake to discard it on the basis that it's just not predictive now.
- TheOtherHobbes 9y ago
  But you need to do a lot of speculative work before falsifiability becomes possible. And that speculative work is going to involve groping around in the dark being guided by mathematical logic (and a certain amount of politics, fashion, and wishful thinking.) Considering physics as if MWI could be true has the potential to lead to mathematical elaboration and eventual falsifiability. Considering physics as if there's no need to interpret QM because there's nothing to interpret (because Copenhagen is the correct interpretation) is a statement of faith, not rigour - because as a position, it's no more falsifiable than MWI, or Bohm, or any of the other interpretations. The point of mathematical physics is to generate new falsifiable predictions. It's still science, it's just embryonic proto-knowledge - which is why it's called research, not teaching.
- naasking 9y ago
  > If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable, then the theory isn't truly scientific. That's an overly anemic view of science. Scientific theories have both predictive and explanatory power. Interpretations of QM don't change the former, but they do change the latter. Copenhagen, favoured by this article's author for some unfathomable reason, has little explanatory power. Many worlds and Bohmian mechanics have excellent explanatory power, and their predictive power equals Copenhagen.
akvadrako 9y ago
It does make different predictions though. WMI essentially says there is only unitary evolution and nothing like a physical collapse. That means everything unitary evolution predicts will happen, unlike other "interpretations". This matters in at least two cases: (1) In a finite system (perhaps our universe, but doubtful), those other worlds will eventually come back into contact. They never go away and with only a finite number of states available, the splitting of worlds can't continue forever. (2) From a subjective perspective, there is always a future version of yourself in some "branch". Since you will become all future versions, you are subjectively immortal.

ajkjk 9y ago

After skimming the whole thing, I was relieved to see that the argument against Many Worlds was the only one I considered invalid. It took the form of "It's not even a testable theory", rather than "it has mathematical deficiencies". Well, of course, no one's saying it's testable necessarily, but for various aesthetic and intuitive reasons it still seems valid. Just don't expect predictions from it and you'll be fine.

whatshisface 9y ago
Valid and true are two very different things - and we've seen from history that the human brain can be lead into believing that essentially anything is intuitive or aesthetic.
- ajkjk 9y ago
  Sure, hence the reason physicists tend to say MWI is valid and good, rather than 'true'.
naasking 9y ago
> After skimming the whole thing, I was relieved to see that the argument against Many Worlds was the only one I considered invalid. You should consider the Bohmian criticisms invalid as well then. Many have argued that de Broglie-Bohm is "many worlds in disguise", so if the criticisms the author levels against Bohmian mechanics are true, then they apply to MWI, but if they don't apply to MWI, then they don't apply to Bohmian mechanics either. Not because they are the same theory, because they are not ontologically the same, but the formalisms are interchangeable.
- ajkjk 9y ago
  Oh yeah. Probably, yeah. I glossed over that one because its criticisms were strangely technical for a theory that, iirc, just rephrases regular quantum theory.

IntronExon 9y ago

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.

omazurov 9y ago

> The many worlds interpretation is just that, and INTERPRETATION, not a predictive theory. How does the many worlds interpretation INTERPRET the Born rule? Shouldn't that be a key feature of any QM interpretation?

whereismypwd 9y ago

His argument is that it's useless as a research topic because you cannot perform experiments about it. You can still believe it if you like, but its slightly less useful than trying to convince everyone to replace pi with tau..

hawkice 9y ago
I mean, the pi/tau thing is _purely_ aesthetic. That's a big waste of time for sure. Having a more coherent metaphor for the evolution of quantum systems might help with physical insight, though. If e.g. the universe isn't differentiable across spacetime, we need a better understanding of GR. Many worlds insists it is differentiable (and local), so thinking that way could help integrate the two. It isn't an important thing, but pi/tau is an unrealistically silly thing to compare it to.
gizmo686 9y ago
QM is a mathematical model. Many worlds is an intuition to understand that model. There is a pedagogical question on if many worlds is a useful mental model to have. There is also a philosophical question of if many worlds better captures the essence of the model relative to Copenhagen. We can also flip it around. Why should we think of QM in terms of the Copenhagen when it makes to testable predictions.
- millstone 9y ago
  Wouldn't you consider the Born rule to be a testable prediction (though in an admittedly weak sense of simply being postulated)? If the Born rule were found to be violated, it would invalidate Copenhagen but not MWI, which IMO means Copenhagen is more falsifiable.
  - naasking 9y ago
    > If the Born rule were found to be violated, it would invalidate Copenhagen but not MWI, which IMO means Copenhagen is more falsifiable. All quantum mechanical interpretations depend upon the Born rule. A violation of the Born rule would rule them all out, except perhaps Bohmian mechanics which allows the possibility of non-equilibrium states, but we have no idea if those can be created.

zombieprocesses 9y ago

If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable, then the theory isn't truly scientific. This is a major issue/concern in advanced theoretical physics. Is it really physics if you can't experiment or is it just mathematics? The foundation of science is falsiability within the scientific method. It's the core tenet.

sgillen 9y ago
For sure, I’m by trying to say it’s a real theory, it’s just a way to interpret the quantum mechanics that we can test in a way that provide us with some sort of intuition when working with the physics.
jamesrcole 9y ago
But what if, after spending more time working on and thinking about it, someone does find a way to make predictions based on it or on an extension/modification of it? If that's a possibility (I can't say, I'm not a physicist) then I'd be a mistake to discard it on the basis that it's just not predictive now.
TheOtherHobbes 9y ago
But you need to do a lot of speculative work before falsifiability becomes possible. And that speculative work is going to involve groping around in the dark being guided by mathematical logic (and a certain amount of politics, fashion, and wishful thinking.) Considering physics as if MWI could be true has the potential to lead to mathematical elaboration and eventual falsifiability. Considering physics as if there's no need to interpret QM because there's nothing to interpret (because Copenhagen is the correct interpretation) is a statement of faith, not rigour - because as a position, it's no more falsifiable than MWI, or Bohm, or any of the other interpretations. The point of mathematical physics is to generate new falsifiable predictions. It's still science, it's just embryonic proto-knowledge - which is why it's called research, not teaching.
naasking 9y ago
> If a theory isn't predictive, it isn't falsifiable. If it isn't falsifiable, then the theory isn't truly scientific. That's an overly anemic view of science. Scientific theories have both predictive and explanatory power. Interpretations of QM don't change the former, but they do change the latter. Copenhagen, favoured by this article's author for some unfathomable reason, has little explanatory power. Many worlds and Bohmian mechanics have excellent explanatory power, and their predictive power equals Copenhagen.

akvadrako 9y ago

It does make different predictions though. WMI essentially says there is only unitary evolution and nothing like a physical collapse. That means everything unitary evolution predicts will happen, unlike other "interpretations". This matters in at least two cases: (1) In a finite system (perhaps our universe, but doubtful), those other worlds will eventually come back into contact. They never go away and with only a finite number of states available, the splitting of worlds can't continue forever. (2) From a subjective perspective, there is always a future version of yourself in some "branch". Since you will become all future versions, you are subjectively immortal.