7 ms·

Most popular science articles on quantum physics are nonsense, but this one is especially confused. Not worth reading at all.

elorant 11y ago
Care to elaborate? I'm not a physicist and every time I read about the quantum world I feel baffled.
- Cshelton 11y ago
  Even to physicist, the quantum world baffling.
- spacehome 11y ago
  That's not your fault; most anybody who reads about quantum physics from most sources will be baffled by it because most authors are thoroughly confused themselves. Look up the Many-Worlds Interpretation. I won't say it's the truth, but it's the most plausible theory available. The math is relatively straightforward, and it gives a deterministic and understandable explanation of what's going on. Denying Many-Worlds necessitates the invention of the philosophical equivalent of epicycles upon epicycles. I've learned that any article or paper that posits something strange going on without even mentioning Many-Worlds is simply not worth the ink it's written with.
  - ThomPete 11y ago
    But doesn't many-world interpretation still require a leap of faith though?
    - spacehome 11y ago
      No? At least not any more than any other theory in science. It's a mathematical model that makes predictions. When the predictions stop matching experiment, then we can throw it away.
      - ThomPete 11y ago
        Maybe I am wrong but as far as I understand thats not really the issue here. As far as I understand there are 3 types of competing interpretations all trying to deal with the local universe vs. the non-local one and trying to explain them in a way that make sense. 1) Logically consistent, allow us to make predictions but which requires a leap of faith (Many World interpretation) 2) Mathematically correct but does not allow us to make predictions (string theory) 3) Allow us to make predictions, doesn't require leap of faith but isn't logically consistent all the way (Copenhagen interpretation) There is also a couple of outsiders like the electrical universe and plasma universe which completely ignores the idea of quantum weirdness but as far as I understand they also require some leap of faith.
        gizmo686 11y ago
        Copenhagen requires a leap of faith to accept wavefunction collapse.
        deleted 11y ago
        [deleted]
      - guscost 11y ago
        The difference with an interpretation like MWI is that no experiment can disprove it, even in theory. The interpretation requires that the many worlds do not interact, and unless that changes, there is no way to observe anything contradictory to the interpretation that doesn't also contradict QM. Most other famous science theories are falsifiable (I would say it is a necessary condition to qualify as science).
        pjscott 11y ago
        It's a mathematical model that makes observable predictions. It's easily falsifiable: just show that its predictions are false. Now, you could argue that there's no test to distinguish it from other interpretations of quantum mechanics, but that applies to them as well.
    - marcosdumay 11y ago
      Only if you believe in it. It's the easiest to understand interpretation of QM, and completely equivalent to all others. So, why not use it?
      - danharaj 11y ago
        Because it gets rather complicated to formalize when you try to reconcile universe splitting with special relativity. There is an even simpler interpretation of quantum mechanics: the relational interpretation. It does not speak of any states and therefore no wavefunction collapse. 0 is ontologically better than infinity.
        spacehome 11y ago
        > it gets rather complicated to formalize when you try to reconcile universe splitting with special relativity Why? And why is it more of a problem for MWI than other interpretations?
        danharaj 11y ago
        When does a universe split? The relativity of simultaneity causes problems: one observer will have to interpret the universe as splitting in one way and then the other, while another will observe the opposite ordering. My personal favorite interpretation is the relational interpretation [1], where we just stop asking nonsensical questions about the universe. It does away with problematic notions that arise from our biases as human beings. [1] http://plato.stanford.edu/entries/qm-relational/ http://plato.stanford.edu/entries/qm-relational/
    - Jach 11y ago
      No. Check out http://arxiv.org/abs/astro-ph/0302131 http://arxiv.org/abs/astro-ph/0302131
  - AgentME 11y ago
    I learned a lot from and really enjoyed the Quantum Physics posts at Less Wrong: http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ . The author starts out focusing on the Many-Worlds interpretation and later defends that point, apparently sharing your criticisms. Early on, the author has a lot to say against other teaching approaches that present Quantum Physics as fundamentally mysterious ("No one really understands it anyway, just use these equations") or leave out the Many-Worlds interpretation: >I am not going to tell you that quantum mechanics is weird, bizarre, confusing, or alien. QM is counterintuitive, but that is a problem with your intuitions, not a problem with quantum mechanics. [...] It is always best to think of reality as perfectly normal. >Dragging a modern-day student through all this [initially teaching the subject in the order it was discovered] may be a historically realistic approach to the subject matter, but it also ensures the historically realistic outcome of total bewilderment. Talking to aspiring young physicists about "wave/particle duality" is like starting chemistry students on the Four Elements. [...] The universe is not wavering between using particles and waves, unable to make up its mind. It's only human intuitions about QM that swap back and forth.
    - spacehome 11y ago
      Yea, that's a good sequence for its philosophical views, though it's a little light on mathematics and calculations for my taste. It works well as a companion to a more rigorous work. I wish there were a rigorous textbook written from a Many-Worlds perspective.
  - jorgecurio 11y ago
    explain why many world interpretation is deserving of so much predisposed legitimacy when no evidence of it exists and no way to properly measure it.
  - n4r9 11y ago
    Many-Worlds has flaws comparable to many other leading interpretations, which is why it's not a large majority view among quantum information and foundations researchers. Explaining why the observable universe is Born-rule typical is a major issue for Many-Worlds. http://arxiv.org/pdf/gr-qc/9703089.pdf http://arxiv.org/pdf/gr-qc/9703089.pdf is a good discussion of this issue, which I don't think has yet had a satisfactory rebuttal. A more up to date version is at http://arxiv.org/abs/0905.0624 http://arxiv.org/abs/0905.0624 It's silly to insist that every article about quantum phenomena should refer to any particular interpretation of the mathematics.
    - spacehome 11y ago
      I thought that explaining the Born rule is a problem for every interpretation.
      - n4r9 11y ago
        It is for many, but not all. Generally speaking, it's less of an issue for interpretations that give an epistemic role to the wavefunction. Perhaps an extreme example, but in the "QBist" interpretation the wavefunction and Born rule are merely a convenient calculus for the prediction of future interactions with the system. It's not the only way to encode this probabilistic information, but it's nice and compact. The issue is then not "why the Born rule?" but "why this particular set of probabilities over potential outcomes?". Then again, a lot of people find the very idea of epistemic interpretations of quantum theory distasteful, especially in light of the Bell, Kochen-Specker and PBR type inequalities.
- jeffwass 11y ago
  You're not alone : "I think I can safely say that nobody understands quantum mechanics." Richard Feynman, The Character of Physical Law (1965)
  - spacehome 11y ago
    And when he said it, it was true.
    - jeffwass 11y ago
      Are you disputing it's not true now? Btw, I can safely tell you that having studied QM in some depth, I usually avoid these types of HN threads. Ie, quite often they're dominated by people who think they know what they're talking about, and throw around buzzwords and make seemingly convincing arguments based on logically or physically unsound bases.
      - spacehome 11y ago
        Yes, I'm claiming that it's not true now and that MWI, while it may not be captial-T Truth, is a concise and deterministic explanation of experimental results.
  - s-macke 11y ago
    I was never happy with this statement. Because obviously we can make very accurate predictions by applying quantum mechanics. The problem with this statement is, that the meaning of "understanding" is unclear here. When I say "I understand that, when I drop an apple it falls on the floor", What exactly do I "understand" here? Does "understanding" mean here, that our brain is trained to predict what would happen? Actually there is a huge understanding on the mathematical level of quantum mechanics. To apply these equations to what we call "reality" is a problem. But then again, what do we mean exactly with "reality" here? If some of the effects of quantum mechanics would be visible for us somehow from birth on, would we "understand" quantum mechanics then?
    - 11y ago
WhitneyLand 11y ago
Disagree. What's wrong with it? Seemed quite interesting.
Strilanc 11y ago
The linked papers are at least interesting. I liked the one about finding a sequence of measurements that can detect if you're trying to emulate an n qubit quantum state with just n classical bits (there's also some other restrictions; if you could just create entanglement with some side-channel qubits and run bell tests then it would be trivial to do). But yeah, skip the article's "interpretation" of the papers.
robinsloan 11y ago
It's worth saying that, in general, Quanta is exemplary; not really "popular science" at all but something much deeper. I see that this writer, George Musser, isn't one of their staff regulars, so this piece might be an exception. But their other (staff?) reporting is absolutely worth following; there's nothing else like it.
dang 11y ago
Drive-by dismissals don't make for good HN comments. Assuming you're right, explaining how the article is confused would be better—we would all learn something. A mere declamation doesn't teach us anything.
jorgecurio 11y ago
I'd downvote this so hard if I could

elorant 11y ago

Care to elaborate? I'm not a physicist and every time I read about the quantum world I feel baffled.

Cshelton 11y ago
Even to physicist, the quantum world baffling.
spacehome 11y ago
That's not your fault; most anybody who reads about quantum physics from most sources will be baffled by it because most authors are thoroughly confused themselves. Look up the Many-Worlds Interpretation. I won't say it's the truth, but it's the most plausible theory available. The math is relatively straightforward, and it gives a deterministic and understandable explanation of what's going on. Denying Many-Worlds necessitates the invention of the philosophical equivalent of epicycles upon epicycles. I've learned that any article or paper that posits something strange going on without even mentioning Many-Worlds is simply not worth the ink it's written with.
- ThomPete 11y ago
  But doesn't many-world interpretation still require a leap of faith though?
  - spacehome 11y ago
    No? At least not any more than any other theory in science. It's a mathematical model that makes predictions. When the predictions stop matching experiment, then we can throw it away.
    - ThomPete 11y ago
      Maybe I am wrong but as far as I understand thats not really the issue here. As far as I understand there are 3 types of competing interpretations all trying to deal with the local universe vs. the non-local one and trying to explain them in a way that make sense. 1) Logically consistent, allow us to make predictions but which requires a leap of faith (Many World interpretation) 2) Mathematically correct but does not allow us to make predictions (string theory) 3) Allow us to make predictions, doesn't require leap of faith but isn't logically consistent all the way (Copenhagen interpretation) There is also a couple of outsiders like the electrical universe and plasma universe which completely ignores the idea of quantum weirdness but as far as I understand they also require some leap of faith.
      - gizmo686 11y ago
        Copenhagen requires a leap of faith to accept wavefunction collapse.
        deleted 11y ago
        [deleted]
    - guscost 11y ago
      The difference with an interpretation like MWI is that no experiment can disprove it, even in theory. The interpretation requires that the many worlds do not interact, and unless that changes, there is no way to observe anything contradictory to the interpretation that doesn't also contradict QM. Most other famous science theories are falsifiable (I would say it is a necessary condition to qualify as science).
      - pjscott 11y ago
        It's a mathematical model that makes observable predictions. It's easily falsifiable: just show that its predictions are false. Now, you could argue that there's no test to distinguish it from other interpretations of quantum mechanics, but that applies to them as well.
  - marcosdumay 11y ago
    Only if you believe in it. It's the easiest to understand interpretation of QM, and completely equivalent to all others. So, why not use it?
    - danharaj 11y ago
      Because it gets rather complicated to formalize when you try to reconcile universe splitting with special relativity. There is an even simpler interpretation of quantum mechanics: the relational interpretation. It does not speak of any states and therefore no wavefunction collapse. 0 is ontologically better than infinity.
      - spacehome 11y ago
        > it gets rather complicated to formalize when you try to reconcile universe splitting with special relativity Why? And why is it more of a problem for MWI than other interpretations?
        danharaj 11y ago
        When does a universe split? The relativity of simultaneity causes problems: one observer will have to interpret the universe as splitting in one way and then the other, while another will observe the opposite ordering. My personal favorite interpretation is the relational interpretation [1], where we just stop asking nonsensical questions about the universe. It does away with problematic notions that arise from our biases as human beings. [1] http://plato.stanford.edu/entries/qm-relational/ http://plato.stanford.edu/entries/qm-relational/
  - Jach 11y ago
    No. Check out http://arxiv.org/abs/astro-ph/0302131 http://arxiv.org/abs/astro-ph/0302131
- AgentME 11y ago
  I learned a lot from and really enjoyed the Quantum Physics posts at Less Wrong: http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ http://lesswrong.com/lw/r5/the_quantum_physics_sequence/ . The author starts out focusing on the Many-Worlds interpretation and later defends that point, apparently sharing your criticisms. Early on, the author has a lot to say against other teaching approaches that present Quantum Physics as fundamentally mysterious ("No one really understands it anyway, just use these equations") or leave out the Many-Worlds interpretation: >I am not going to tell you that quantum mechanics is weird, bizarre, confusing, or alien. QM is counterintuitive, but that is a problem with your intuitions, not a problem with quantum mechanics. [...] It is always best to think of reality as perfectly normal. >Dragging a modern-day student through all this [initially teaching the subject in the order it was discovered] may be a historically realistic approach to the subject matter, but it also ensures the historically realistic outcome of total bewilderment. Talking to aspiring young physicists about "wave/particle duality" is like starting chemistry students on the Four Elements. [...] The universe is not wavering between using particles and waves, unable to make up its mind. It's only human intuitions about QM that swap back and forth.
  - spacehome 11y ago
    Yea, that's a good sequence for its philosophical views, though it's a little light on mathematics and calculations for my taste. It works well as a companion to a more rigorous work. I wish there were a rigorous textbook written from a Many-Worlds perspective.
- jorgecurio 11y ago
  explain why many world interpretation is deserving of so much predisposed legitimacy when no evidence of it exists and no way to properly measure it.
- n4r9 11y ago
  Many-Worlds has flaws comparable to many other leading interpretations, which is why it's not a large majority view among quantum information and foundations researchers. Explaining why the observable universe is Born-rule typical is a major issue for Many-Worlds. http://arxiv.org/pdf/gr-qc/9703089.pdf http://arxiv.org/pdf/gr-qc/9703089.pdf is a good discussion of this issue, which I don't think has yet had a satisfactory rebuttal. A more up to date version is at http://arxiv.org/abs/0905.0624 http://arxiv.org/abs/0905.0624 It's silly to insist that every article about quantum phenomena should refer to any particular interpretation of the mathematics.
  - spacehome 11y ago
    I thought that explaining the Born rule is a problem for every interpretation.
    - n4r9 11y ago
      It is for many, but not all. Generally speaking, it's less of an issue for interpretations that give an epistemic role to the wavefunction. Perhaps an extreme example, but in the "QBist" interpretation the wavefunction and Born rule are merely a convenient calculus for the prediction of future interactions with the system. It's not the only way to encode this probabilistic information, but it's nice and compact. The issue is then not "why the Born rule?" but "why this particular set of probabilities over potential outcomes?". Then again, a lot of people find the very idea of epistemic interpretations of quantum theory distasteful, especially in light of the Bell, Kochen-Specker and PBR type inequalities.
jeffwass 11y ago
You're not alone : "I think I can safely say that nobody understands quantum mechanics." Richard Feynman, The Character of Physical Law (1965)
- spacehome 11y ago
  And when he said it, it was true.
  - jeffwass 11y ago
    Are you disputing it's not true now? Btw, I can safely tell you that having studied QM in some depth, I usually avoid these types of HN threads. Ie, quite often they're dominated by people who think they know what they're talking about, and throw around buzzwords and make seemingly convincing arguments based on logically or physically unsound bases.
    - spacehome 11y ago
      Yes, I'm claiming that it's not true now and that MWI, while it may not be captial-T Truth, is a concise and deterministic explanation of experimental results.
- s-macke 11y ago
  I was never happy with this statement. Because obviously we can make very accurate predictions by applying quantum mechanics. The problem with this statement is, that the meaning of "understanding" is unclear here. When I say "I understand that, when I drop an apple it falls on the floor", What exactly do I "understand" here? Does "understanding" mean here, that our brain is trained to predict what would happen? Actually there is a huge understanding on the mathematical level of quantum mechanics. To apply these equations to what we call "reality" is a problem. But then again, what do we mean exactly with "reality" here? If some of the effects of quantum mechanics would be visible for us somehow from birth on, would we "understand" quantum mechanics then?
  - 11y ago

WhitneyLand 11y ago

Disagree. What's wrong with it? Seemed quite interesting.

Strilanc 11y ago

The linked papers are at least interesting. I liked the one about finding a sequence of measurements that can detect if you're trying to emulate an n qubit quantum state with just n classical bits (there's also some other restrictions; if you could just create entanglement with some side-channel qubits and run bell tests then it would be trivial to do). But yeah, skip the article's "interpretation" of the papers.

robinsloan 11y ago

It's worth saying that, in general, Quanta is exemplary; not really "popular science" at all but something much deeper. I see that this writer, George Musser, isn't one of their staff regulars, so this piece might be an exception. But their other (staff?) reporting is absolutely worth following; there's nothing else like it.

dang 11y ago

Drive-by dismissals don't make for good HN comments. Assuming you're right, explaining how the article is confused would be better—we would all learn something. A mere declamation doesn't teach us anything.

jorgecurio 11y ago

I'd downvote this so hard if I could