5 ms·

Calculate but don’t shut up

58 points by Petiver 5y ago

deleted 5y ago
[deleted]
account-5 5y ago
I found that really interesting to read, I have no idea what it was trying to say though. (I'm not a physicist or philosopher)
- icen 5y ago
  My reading of the piece is that it ascribes to the Copenhagen interpretation an anti-realist perspective - that is, the theory is nothing other than the ability to predict the results of experiments. In this view, there is no wave-function in reality: it is just a mathematical tool that appears to predict the dots on the screen well. Scientific Realism holds that in some sense scientific theories approximate the world, not just in what the experiments observe, but also in the content of their explanations (precisely, you gain knowledge not just about observables, but also non-observables: things that the theory requires to be true, but can't show). The article ascribes this view to Einstein, who presumably thought that there was a such thing as space-time, and it does actually curve under the influence of mass - despite only seeing things that are explained by the curvature, and not the curvature, or the space-time, itself. The article then goes on to say that the anti-realist approach (dominated by not-undeserving practical concerns and application) focuses on computation: the mathematics is good so long as it gets the right answers in the end, and the end justifies the means. Therefore, it doesn't matter what contrivances must be dealt with in-between: if you get a better prediction, or can do a new exciting thing, then that was always the aim. Thus, I read the article as advocating a stepping back from this view: it blames this focus on sheer mathematical sophistication as the route to truth as the source of profound disinterest in philosophy by physicists (it is important to note that I think that aeon is a philosophy newsletter!). Earlier and contemporary physicists (prominently, Einstein) had an interest in not just what their theories produced, but what they explained the world to be, and the article decries the modern lack of this. I recommend the SEP article on scientific realism, which is dense but on a brief reading gives enough of the context to recognise the article. https://plato.stanford.edu/entries/scientific-realism/ https://plato.stanford.edu/entries/scientific-realism/ (Although it is even more philosophically focused). NB. I'm not a physicist or philosopher either, so grains of salt! My only self-endorsement is that I spent the last year reading a bit of philosophy, so perhaps I can be at least a stepping-stone to better resource.
  - account-5 5y ago
    Thanks for taking the time, around new years to boot, to explain it better for me; much appreciated. So my take now is that as long as it works no one is questioning why or how it works. Which is what you'd expect scientists to be doing.
    - nelgaard 5y ago
      You should question how it works. And test whether it works. Or find a simpler theory that works as well. Or a theory that can explain more. Postulating that there must be a better theory is pointless. Bell's theorem was never a pointless philosophical issue. It is physics and that is why it can be tested experiementally.
  - nelgaard 5y ago
    First: no one presumed Einstein to be senile. He was sceptical about qm, and being sceptical is good. He also agreed with Bohr that what mattered was results of experiements. That is why they came up with all those brilliant thought-experiements that could only become real experiements much later. Theories that cannot predict anything in the real world might be interesting, but it is not physics. ( I did study at the Niels Bohr institute in Copenhagen a long time ago)
nopenopenopeno 5y ago
Bohr’s perspective sounds a lot like Kantian idealism.
- ogogmad 5y ago
  Explain.
  - nopenopenopeno 5y ago
    I don’t think Kantian idealism is really idealism in the traditional sense, but it’s essentially just the idea that the world humans can know is not the world as it is, but rather just a subset or interpretation which, in all likelihood, bares little resemblance to the world as it is.
whatshisface 5y ago
The purpose of fluffy thinking in science is clear to anyone who's heard even a few original thinkers talk about where they got their hard theories from, which is as a way for a worker to be slightly more likely to guess the right equation than if they were literally just guessing.
sam-2727 5y ago
Perhaps I'm misunderstanding some of the philosophical aspects here, but the Copenhagen interpretation seems to just a label for the (now) undisputed basic facts of quantum mechanics, so the "interpretation" part of it seems to be a bit historical now. The Wikipedia page gives the following "principles" of the interpretation: > Quantum mechanics is intrinsically indeterministic. > The correspondence principle: in the appropriate limit, quantum theory comes to resemble classical physics and reproduces the classical predictions. The Born rule: the wave function of a system yields probabilities for the outcomes of measurements upon that system. > Complementarity: certain properties cannot be jointly defined for the same system at the same time. In order to talk about a specific property of a system, that system must be considered within the context of a specific laboratory arrangement. Observable quantities corresponding to mutually exclusive laboratory arrangements cannot be predicted together, but considering multiple such mutually exclusive experiments is necessary to characterize a system. These are universally accepted facts now (it would be silly for any physical theory to contradict the second one). Even a kind of "out there" theory like many worlds theory (https://en.wikipedia.org/wiki/Many-worlds_interpretation https://en.wikipedia.org/wiki/Many-worlds_interpretation) would not dispute these facts (it just reinterprets the indeterminism of quantum mechanics as taking different "branches" in a multiverse). The "interpretation" part of it is a bit historical, as no "interpretation" should contradict these facts (a la Bell's theorem). Edit: As a philosophy, any "interpretation" built off of these facts is cool, but until you calculate anything, it's essentially useless as a physical theory.
- DebtDeflation 5y ago
  The collapse of the wave function upon measurement is the interpretation part that is disputed by other interpretations.
  - deleted 5y ago
    [deleted]
  - sam-2727 5y ago
    Interesting, although I struggle to see how this could be. The collapse (from our point of view, at least) of the wave function is pretty necessary in the math of QM. You can only observe the eigenstates of a wavefunction, which is what collapse is. To me, it seems that other theories are just disputing what the "collapse" fundamentally means. For example, Many Worlds theory (from my admittedly limited understanding) says that the wave function's eigenstates each become the new reality in different universes. Please correct me if I'm wrong here though.
lordnacho 5y ago
Has anyone thought about this in a classical context? It's it only the weirdness of quantum that makes this relevant?
davidgtl 5y ago
Not sure if it applies here, also not a physicist, so just some food for thought: I've noticed that many of humanity's models try to simplify things into neat models and that results in either - many specific models, each focusing on a specific macro-behaviour - one statistical model which basically describes the underlying process as non-deterministic Couple that with performance debugging 101: Measuring the performance of a function changes the performance of a function (Fudamentally because you can't see without interacting, and sometimes that interaction creates weird results) And the conclusion is that Quantum Mechanics is a statistical model of a complex hot path which we're trying to measure, so of course it's going to be weird and hard to so.
scotty79 5y ago
It's painfully easy to have a clear intuitive picture of quantum physics. You just have to ditch one concept. Universe is not made of little balls. Particles ARE their wave functions. Nothing less, nothing more. Sometimes those two wavevy objects interact as if two little balls bounced at one point, but that's only "accidental" similarity between the way they exchange the energy (and momentum) and the way macroscopic balls exchange the energy. Yes. It's not deterministic, what will be the parameters of that interaction. At what spot exactly will it seem to have happened, how much energy will be exchanged and how will it reshape and redirect the inital wavy objects. But thanks to our math we can predict likelyhood of everything that might happen. Well, not exactly accidental because the way macroscopic balls bounce comes out of the exchange of energy by microscopic wavy objects bound tightly together. Same way that macroscopic magnetic interactions come from microscopic interactions of many thightly bound and oriented particles. Wave functions never collapse into little balls, they just interact as if two balls bounced, and they get reshaped to be smaller and less fuzzy, but that's it. You can easily spread them back by interacting with them again in a different manner. There's no such thing as a measurement. Measurement is just interaction with large rigidly bound chunk of matter which reshapes the measured particle because any interaction always reshapes. There's really no reason to think that particles are little balls or matrial points or anything similar. Initially people thought that because of photoelectric effect. That energy is transferred in quanta. But it's not hard to imagine this as purely fuzzy, wavy phenomenon where electrons are stuck around the nucleus in a sort of "harmonic" and they can't jump up to the place half-way to their next more energetic harmonic. Check out how orbitals look (and Chladni figures) if what I wrote seems unclear. If you know any reason to think particles are little pointlike objects please let me known because I couldn't find any.

58 points by Petiver 5y ago

deleted 5y ago

[deleted]

I found that really interesting to read, I have no idea what it was trying to say though. (I'm not a physicist or philosopher)

icen 5y ago
My reading of the piece is that it ascribes to the Copenhagen interpretation an anti-realist perspective - that is, the theory is nothing other than the ability to predict the results of experiments. In this view, there is no wave-function in reality: it is just a mathematical tool that appears to predict the dots on the screen well. Scientific Realism holds that in some sense scientific theories approximate the world, not just in what the experiments observe, but also in the content of their explanations (precisely, you gain knowledge not just about observables, but also non-observables: things that the theory requires to be true, but can't show). The article ascribes this view to Einstein, who presumably thought that there was a such thing as space-time, and it does actually curve under the influence of mass - despite only seeing things that are explained by the curvature, and not the curvature, or the space-time, itself. The article then goes on to say that the anti-realist approach (dominated by not-undeserving practical concerns and application) focuses on computation: the mathematics is good so long as it gets the right answers in the end, and the end justifies the means. Therefore, it doesn't matter what contrivances must be dealt with in-between: if you get a better prediction, or can do a new exciting thing, then that was always the aim. Thus, I read the article as advocating a stepping back from this view: it blames this focus on sheer mathematical sophistication as the route to truth as the source of profound disinterest in philosophy by physicists (it is important to note that I think that aeon is a philosophy newsletter!). Earlier and contemporary physicists (prominently, Einstein) had an interest in not just what their theories produced, but what they explained the world to be, and the article decries the modern lack of this. I recommend the SEP article on scientific realism, which is dense but on a brief reading gives enough of the context to recognise the article. https://plato.stanford.edu/entries/scientific-realism/ https://plato.stanford.edu/entries/scientific-realism/ (Although it is even more philosophically focused). NB. I'm not a physicist or philosopher either, so grains of salt! My only self-endorsement is that I spent the last year reading a bit of philosophy, so perhaps I can be at least a stepping-stone to better resource.
- account-5 5y ago
  Thanks for taking the time, around new years to boot, to explain it better for me; much appreciated. So my take now is that as long as it works no one is questioning why or how it works. Which is what you'd expect scientists to be doing.
  - nelgaard 5y ago
    You should question how it works. And test whether it works. Or find a simpler theory that works as well. Or a theory that can explain more. Postulating that there must be a better theory is pointless. Bell's theorem was never a pointless philosophical issue. It is physics and that is why it can be tested experiementally.
- nelgaard 5y ago
  First: no one presumed Einstein to be senile. He was sceptical about qm, and being sceptical is good. He also agreed with Bohr that what mattered was results of experiements. That is why they came up with all those brilliant thought-experiements that could only become real experiements much later. Theories that cannot predict anything in the real world might be interesting, but it is not physics. ( I did study at the Niels Bohr institute in Copenhagen a long time ago)

nopenopenopeno 5y ago

Bohr’s perspective sounds a lot like Kantian idealism.

ogogmad 5y ago
Explain.
- nopenopenopeno 5y ago
  I don’t think Kantian idealism is really idealism in the traditional sense, but it’s essentially just the idea that the world humans can know is not the world as it is, but rather just a subset or interpretation which, in all likelihood, bares little resemblance to the world as it is.

whatshisface 5y ago

The purpose of fluffy thinking in science is clear to anyone who's heard even a few original thinkers talk about where they got their hard theories from, which is as a way for a worker to be slightly more likely to guess the right equation than if they were literally just guessing.

sam-2727 5y ago

Perhaps I'm misunderstanding some of the philosophical aspects here, but the Copenhagen interpretation seems to just a label for the (now) undisputed basic facts of quantum mechanics, so the "interpretation" part of it seems to be a bit historical now. The Wikipedia page gives the following "principles" of the interpretation: > Quantum mechanics is intrinsically indeterministic. > The correspondence principle: in the appropriate limit, quantum theory comes to resemble classical physics and reproduces the classical predictions. The Born rule: the wave function of a system yields probabilities for the outcomes of measurements upon that system. > Complementarity: certain properties cannot be jointly defined for the same system at the same time. In order to talk about a specific property of a system, that system must be considered within the context of a specific laboratory arrangement. Observable quantities corresponding to mutually exclusive laboratory arrangements cannot be predicted together, but considering multiple such mutually exclusive experiments is necessary to characterize a system. These are universally accepted facts now (it would be silly for any physical theory to contradict the second one). Even a kind of "out there" theory like many worlds theory (https://en.wikipedia.org/wiki/Many-worlds_interpretation https://en.wikipedia.org/wiki/Many-worlds_interpretation) would not dispute these facts (it just reinterprets the indeterminism of quantum mechanics as taking different "branches" in a multiverse). The "interpretation" part of it is a bit historical, as no "interpretation" should contradict these facts (a la Bell's theorem). Edit: As a philosophy, any "interpretation" built off of these facts is cool, but until you calculate anything, it's essentially useless as a physical theory.

DebtDeflation 5y ago
The collapse of the wave function upon measurement is the interpretation part that is disputed by other interpretations.
- deleted 5y ago
  [deleted]
- sam-2727 5y ago
  Interesting, although I struggle to see how this could be. The collapse (from our point of view, at least) of the wave function is pretty necessary in the math of QM. You can only observe the eigenstates of a wavefunction, which is what collapse is. To me, it seems that other theories are just disputing what the "collapse" fundamentally means. For example, Many Worlds theory (from my admittedly limited understanding) says that the wave function's eigenstates each become the new reality in different universes. Please correct me if I'm wrong here though.

lordnacho 5y ago

Has anyone thought about this in a classical context? It's it only the weirdness of quantum that makes this relevant?

davidgtl 5y ago

Not sure if it applies here, also not a physicist, so just some food for thought: I've noticed that many of humanity's models try to simplify things into neat models and that results in either - many specific models, each focusing on a specific macro-behaviour - one statistical model which basically describes the underlying process as non-deterministic Couple that with performance debugging 101: Measuring the performance of a function changes the performance of a function (Fudamentally because you can't see without interacting, and sometimes that interaction creates weird results) And the conclusion is that Quantum Mechanics is a statistical model of a complex hot path which we're trying to measure, so of course it's going to be weird and hard to so.

scotty79 5y ago

It's painfully easy to have a clear intuitive picture of quantum physics. You just have to ditch one concept. Universe is not made of little balls. Particles ARE their wave functions. Nothing less, nothing more. Sometimes those two wavevy objects interact as if two little balls bounced at one point, but that's only "accidental" similarity between the way they exchange the energy (and momentum) and the way macroscopic balls exchange the energy. Yes. It's not deterministic, what will be the parameters of that interaction. At what spot exactly will it seem to have happened, how much energy will be exchanged and how will it reshape and redirect the inital wavy objects. But thanks to our math we can predict likelyhood of everything that might happen. Well, not exactly accidental because the way macroscopic balls bounce comes out of the exchange of energy by microscopic wavy objects bound tightly together. Same way that macroscopic magnetic interactions come from microscopic interactions of many thightly bound and oriented particles. Wave functions never collapse into little balls, they just interact as if two balls bounced, and they get reshaped to be smaller and less fuzzy, but that's it. You can easily spread them back by interacting with them again in a different manner. There's no such thing as a measurement. Measurement is just interaction with large rigidly bound chunk of matter which reshapes the measured particle because any interaction always reshapes. There's really no reason to think that particles are little balls or matrial points or anything similar. Initially people thought that because of photoelectric effect. That energy is transferred in quanta. But it's not hard to imagine this as purely fuzzy, wavy phenomenon where electrons are stuck around the nucleus in a sort of "harmonic" and they can't jump up to the place half-way to their next more energetic harmonic. Check out how orbitals look (and Chladni figures) if what I wrote seems unclear. If you know any reason to think particles are little pointlike objects please let me known because I couldn't find any.