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> Therefore it is in a very real sense the most austere interpretation, even though it posits all those worlds. I strongly disagree. Wave function collapse is

> Therefore it is in a very real sense the most austere interpretation, even though it posits all those worlds. I strongly disagree. Wave function collapse is the best description for a randomized phenomena we can observe. That exact same phenomena exists in many worlds as well, just that many worlds invent whole different universes to try to get away from the fact that to us the event is random. So instead of saying "our universe is random" you say "Our universe is not random, we just observe a random part of the universe and can never observe the real whole part of it", that isn't solving anything at all, its just a more elaborate way to say "the universe is random".

mort96 4y ago
Wave function collapse is an additional mechanism. If you remove the wave function collapse, you get many worlds.
- Jensson 4y ago
  But we observe a random phenomena and call that wave function collapses, we don't observe many worlds. Many worlds is outside of observation, it is an additional feature of the universe that isn't based on any observations.
  - mort96 4y ago
    I mean you're right of course, if this was easily experimentally testable we would've done so already. So we're left to choose between two theories: one in which the rules for macro systems and quantum systems are completely different and quantum systems collapse into a state consistent with the rules for macro systems when they interact with a macro system -- and one where there is only the one set of rules and no collapse. That doesn't mean you should choose to believe one or the other, but it means that one model requires fewer mechanisms than the other. At least that's my understanding.
    - Jensson 4y ago
      > one in which the rules for macro systems and quantum systems are completely different and quantum systems collapse into a state consistent with the rules for macro systems when they interact with a macro system That is wrong, quantum state collapse just makes the quantum wave take the shape of another quantum wave, nothing in it requires it to be related to macro state nonsense like pointwise particles etc. If that is the reason you don't like wavefunction collapse then you just misunderstood quantum mechanics basics, all wave function collapse is is that it is a rule for how quantum waves can transform, there is nothing about it that connects it to our macro world view. > and one where there is only the one set of rules and no collapse. MWI still has wave function collapse, the "we observe random part of the universe" part is the wave function collapse, that remains unexplained, why do we only see a random subset? You can't explain that. Many worlds make it harder to see that this part is unexplained, that makes it strictly worse as an interpretation in my opinion.
      - mort96 4y ago
        I was assuming you were arguing for something like the copenhagen interpretation. It now sounds like you're not, but I don't understand what interpretation you're referring to where the wave function takes the shape of another wave function. Do you mean that there is one universal wave function, but the "collapse" is one where the universal wave function discontinuously changes to reflect a probability distribution where (say) a particle's position has much less uncertainty? What is this interpretation called? Anyways, that's still an additional mechanism. > MWI still has wave function collapse, the "we observe random part of the universe" part is the wave function collapse, that remains unexplained, why do we only see a random subset? You can't explain that. That's not wave function collapse. The wave function just keeps evolving as normal. I don't know enough about this to explain how the MWI maps on to our subjective experiences, I could probably find some links but I'm sure you're as good at that as I am. I'm not arguing that MWI is a better interpretation here, just that it has fewer mechanisms.
        Jensson 4y ago
        > I was assuming you were arguing for something like the copenhagen interpretation. It sounds like you're not, but I don't understand what interpretation you're referring to where the wave function takes the shape of another wave function. Do you mean that there is one universal wave function, but the "collapse" is one where the universal wave function discontinuously changes to reflect a probability distribution where (say) a particle's position has much less uncertainty? What is this interpretation called? Wave function collapse is an observed phenomena, this has no interpretation at all, its just taking what we observe and say "this is what we observe". I'm not sure why you call out "wave function collapse" as something strange or alien to quantum mechanics, it is one of the core parts. In the basic quantum mechanic course every physics student takes nowhere do they say "quantum waves collapses to pointwise particle states", they say "quantum waves collapses to eigenstates of quantum waves". So, wave function collapse is just what we call the observed phenomena that when we measure a quantum wave it takes the shape of one of the eigenstates of the measurement. That is all it is, and that is true regardless if you have a MWI or a Copenhagen, or like me a "quantum waves behave weirdly during some interactions" interpretations of quantum mechanics. And I think my interpretation makes the least assumptions, we have quantum waves, and during some interactions they collapse to one of its eigenstates of that interaction. That is the purest form of quantum mechanics, no need to do more than that. Edit: And trying to argue about more interpretations than that is like trying to invent some divine interpretation of Newtons laws of motions etc. Those are just descriptions of how things behaves.
  - d0mine 4y ago
    We don't observe almost all real number either. We observe some rational numbers. All these infinite number of unobservable real numbers is just waste /s
  - akvadrako 4y ago
    The many worlds are not an additional feature of MWI compared to other interpretations. They all have them in the math. In pilot wave theories they are just claimed to not be real, yet they affect things. In objective collapse theories they disappear when measured.
kanzenryu2 4y ago
Consider just the aspect of randomness alone. How can the universe implement it? It seems like a really awkward problem. [But the Everett interpretation gives it to us for free](https://www.preposterousuniverse.com/blog/2014/07/28/quantum-sleeping-beauty-and-the-multiverse/ https://www.preposterousuniverse.com/blog/2014/07/28/quantum...). It really seems like a killer argument to me.
- Jensson 4y ago
  That just deals with the random nature of wave function collapse, not the mechanical nature. Wave function collapse can be used to move around particles, or rotate them etc. A single measurement is just a normal random chance, but you can do a series of measurements over different basis you start to affect the system in non trivial ways, you can use that to control position or rotation or other states of particles, MWI doesn't explain that part at all. A poster above posted something to explain this a bit: http://www.paradise.caltech.edu/~cook/Workshop/Physics/QMQuestion.html http://www.paradise.caltech.edu/~cook/Workshop/Physics/QMQue...
mtlmtlmtlmtl 4y ago
I'm not really in the mood to play the game of figuring out what you're trying to say a second time today, sorry. But you're wrong. Any serious researcher working on the foundations of quantum mechanics agrees that MWI is the most austere. That includes the ones who prefer a different interpretation. You can disagree with the whole field if you want. You do you, I guess.
- Jensson 4y ago
  Most quantum mechanics researchers just ignores waveform collapses entirely because you can do a lot without it. I don't think that they have anything significant to add to this discussion since MWI just has to do with wavefunction collapse., them being experts at wavefunctions when the function doesn't collapse doesn't make a difference. Edit: To add, all quantum mechanics interpretations are equivalent when you ignore wavefunction collapse. So only experts on wavefunction collapses would have a credible say here. But there is very little research in that area, so there aren't many experts on it.
omnicognate 4y ago
Yes, this is the emperor's new clothes of MWI, and it doesn't take any specialist knowledge to see it. Quantum mechanical theories produce probabilities for things happening. We can conduct repeated experiments and verify those probabilities against the results. If every outcome actually happens, there is no longer any place for those probabilities. It is meaningless to talk about the relative probabilities of events A and B happening if both A and B actually happen, deterministically. These probabilities aren't just numbers produced by the theory, they are the predictive content of the theory, the very thing we're supposed to be interpreting, and MWI has no place for them. The way this problem is often discussed is to talk about "recovering the Born probabilities", which frames the problem wrongly. It makes it sound like the problem is that MWI merely isn't producing some numbers we like. MWI proponents respond to this by going through absurd contortions involving things like decision theory as a way of causing the desired numbers to pop out of a calculation. But the problem isn't "recovering the probabilities". The problem isn't finding some way of performing a calculation that results in these particular numbers. The problem is that these probabilities have no physical meaning in MWI, and it's a catastrophic problem because those probabilities have a very real meaning in the actual world as we observe it. It really is as simple as "how can all the things happen at once when we know some of the things are more likely than others?" And, like "why is the emperor naked?" it's a question that can literally be asked by a child. An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time.
- sebzim4500 4y ago
  I agree with a lot of what you have said, but I would strongly disagree with your conclusion. >An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time. Given that the different interpretations do not make different predictions, the only relevant way to judge them is to ask the question "is X interpretation a useful way to think about the universe". This can be answered empirically, practitioners of both MWI and CI have both made important advances in quantum physics, therefore neither are a waste of anybody's time. There is a reason why students generally get taught both, there is nothing wrong with having multiple ways to think about things.
mgraczyk 4y ago
This is not quite right though. In objective collapse theories, there is an "us" to do the observing, and there is a collapse event which samples randomly from the possible outcomes. Both the "us" and the sampling are additional things that we have to add to the theory. In MWI, there is no "us" in an objective physical sense. "We" are on all the "branches" of the wavefunction, spread out in such a way that it isn't possible for any observation to see both events having happened. We don't "observe a random part of the universe", we do observe all parts of it. It's just that "we" aren't classical in the sense that you are implying.

mort96 4y ago

Wave function collapse is an additional mechanism. If you remove the wave function collapse, you get many worlds.

Jensson 4y ago
But we observe a random phenomena and call that wave function collapses, we don't observe many worlds. Many worlds is outside of observation, it is an additional feature of the universe that isn't based on any observations.
- mort96 4y ago
  I mean you're right of course, if this was easily experimentally testable we would've done so already. So we're left to choose between two theories: one in which the rules for macro systems and quantum systems are completely different and quantum systems collapse into a state consistent with the rules for macro systems when they interact with a macro system -- and one where there is only the one set of rules and no collapse. That doesn't mean you should choose to believe one or the other, but it means that one model requires fewer mechanisms than the other. At least that's my understanding.
  - Jensson 4y ago
    > one in which the rules for macro systems and quantum systems are completely different and quantum systems collapse into a state consistent with the rules for macro systems when they interact with a macro system That is wrong, quantum state collapse just makes the quantum wave take the shape of another quantum wave, nothing in it requires it to be related to macro state nonsense like pointwise particles etc. If that is the reason you don't like wavefunction collapse then you just misunderstood quantum mechanics basics, all wave function collapse is is that it is a rule for how quantum waves can transform, there is nothing about it that connects it to our macro world view. > and one where there is only the one set of rules and no collapse. MWI still has wave function collapse, the "we observe random part of the universe" part is the wave function collapse, that remains unexplained, why do we only see a random subset? You can't explain that. Many worlds make it harder to see that this part is unexplained, that makes it strictly worse as an interpretation in my opinion.
    - mort96 4y ago
      I was assuming you were arguing for something like the copenhagen interpretation. It now sounds like you're not, but I don't understand what interpretation you're referring to where the wave function takes the shape of another wave function. Do you mean that there is one universal wave function, but the "collapse" is one where the universal wave function discontinuously changes to reflect a probability distribution where (say) a particle's position has much less uncertainty? What is this interpretation called? Anyways, that's still an additional mechanism. > MWI still has wave function collapse, the "we observe random part of the universe" part is the wave function collapse, that remains unexplained, why do we only see a random subset? You can't explain that. That's not wave function collapse. The wave function just keeps evolving as normal. I don't know enough about this to explain how the MWI maps on to our subjective experiences, I could probably find some links but I'm sure you're as good at that as I am. I'm not arguing that MWI is a better interpretation here, just that it has fewer mechanisms.
      - Jensson 4y ago
        > I was assuming you were arguing for something like the copenhagen interpretation. It sounds like you're not, but I don't understand what interpretation you're referring to where the wave function takes the shape of another wave function. Do you mean that there is one universal wave function, but the "collapse" is one where the universal wave function discontinuously changes to reflect a probability distribution where (say) a particle's position has much less uncertainty? What is this interpretation called? Wave function collapse is an observed phenomena, this has no interpretation at all, its just taking what we observe and say "this is what we observe". I'm not sure why you call out "wave function collapse" as something strange or alien to quantum mechanics, it is one of the core parts. In the basic quantum mechanic course every physics student takes nowhere do they say "quantum waves collapses to pointwise particle states", they say "quantum waves collapses to eigenstates of quantum waves". So, wave function collapse is just what we call the observed phenomena that when we measure a quantum wave it takes the shape of one of the eigenstates of the measurement. That is all it is, and that is true regardless if you have a MWI or a Copenhagen, or like me a "quantum waves behave weirdly during some interactions" interpretations of quantum mechanics. And I think my interpretation makes the least assumptions, we have quantum waves, and during some interactions they collapse to one of its eigenstates of that interaction. That is the purest form of quantum mechanics, no need to do more than that. Edit: And trying to argue about more interpretations than that is like trying to invent some divine interpretation of Newtons laws of motions etc. Those are just descriptions of how things behaves.
- d0mine 4y ago
  We don't observe almost all real number either. We observe some rational numbers. All these infinite number of unobservable real numbers is just waste /s
- akvadrako 4y ago
  The many worlds are not an additional feature of MWI compared to other interpretations. They all have them in the math. In pilot wave theories they are just claimed to not be real, yet they affect things. In objective collapse theories they disappear when measured.

kanzenryu2 4y ago

Consider just the aspect of randomness alone. How can the universe implement it? It seems like a really awkward problem. [But the Everett interpretation gives it to us for free](https://www.preposterousuniverse.com/blog/2014/07/28/quantum-sleeping-beauty-and-the-multiverse/ https://www.preposterousuniverse.com/blog/2014/07/28/quantum...). It really seems like a killer argument to me.

Jensson 4y ago
That just deals with the random nature of wave function collapse, not the mechanical nature. Wave function collapse can be used to move around particles, or rotate them etc. A single measurement is just a normal random chance, but you can do a series of measurements over different basis you start to affect the system in non trivial ways, you can use that to control position or rotation or other states of particles, MWI doesn't explain that part at all. A poster above posted something to explain this a bit: http://www.paradise.caltech.edu/~cook/Workshop/Physics/QMQuestion.html http://www.paradise.caltech.edu/~cook/Workshop/Physics/QMQue...

mtlmtlmtlmtl 4y ago

I'm not really in the mood to play the game of figuring out what you're trying to say a second time today, sorry. But you're wrong. Any serious researcher working on the foundations of quantum mechanics agrees that MWI is the most austere. That includes the ones who prefer a different interpretation. You can disagree with the whole field if you want. You do you, I guess.

Jensson 4y ago
Most quantum mechanics researchers just ignores waveform collapses entirely because you can do a lot without it. I don't think that they have anything significant to add to this discussion since MWI just has to do with wavefunction collapse., them being experts at wavefunctions when the function doesn't collapse doesn't make a difference. Edit: To add, all quantum mechanics interpretations are equivalent when you ignore wavefunction collapse. So only experts on wavefunction collapses would have a credible say here. But there is very little research in that area, so there aren't many experts on it.

omnicognate 4y ago

Yes, this is the emperor's new clothes of MWI, and it doesn't take any specialist knowledge to see it. Quantum mechanical theories produce probabilities for things happening. We can conduct repeated experiments and verify those probabilities against the results. If every outcome actually happens, there is no longer any place for those probabilities. It is meaningless to talk about the relative probabilities of events A and B happening if both A and B actually happen, deterministically. These probabilities aren't just numbers produced by the theory, they are the predictive content of the theory, the very thing we're supposed to be interpreting, and MWI has no place for them. The way this problem is often discussed is to talk about "recovering the Born probabilities", which frames the problem wrongly. It makes it sound like the problem is that MWI merely isn't producing some numbers we like. MWI proponents respond to this by going through absurd contortions involving things like decision theory as a way of causing the desired numbers to pop out of a calculation. But the problem isn't "recovering the probabilities". The problem isn't finding some way of performing a calculation that results in these particular numbers. The problem is that these probabilities have no physical meaning in MWI, and it's a catastrophic problem because those probabilities have a very real meaning in the actual world as we observe it. It really is as simple as "how can all the things happen at once when we know some of the things are more likely than others?" And, like "why is the emperor naked?" it's a question that can literally be asked by a child. An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time.

sebzim4500 4y ago
I agree with a lot of what you have said, but I would strongly disagree with your conclusion. >An "interpretation" that renders the core predictive content of the theory meaningless is a bad interpretation and a waste of everyone's time. Given that the different interpretations do not make different predictions, the only relevant way to judge them is to ask the question "is X interpretation a useful way to think about the universe". This can be answered empirically, practitioners of both MWI and CI have both made important advances in quantum physics, therefore neither are a waste of anybody's time. There is a reason why students generally get taught both, there is nothing wrong with having multiple ways to think about things.

mgraczyk 4y ago

This is not quite right though. In objective collapse theories, there is an "us" to do the observing, and there is a collapse event which samples randomly from the possible outcomes. Both the "us" and the sampling are additional things that we have to add to the theory. In MWI, there is no "us" in an objective physical sense. "We" are on all the "branches" of the wavefunction, spread out in such a way that it isn't possible for any observation to see both events having happened. We don't "observe a random part of the universe", we do observe all parts of it. It's just that "we" aren't classical in the sense that you are implying.