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I would characterize these fluid dynamics experiments as "very cute", but nothing more. One of the sad things about physics these days is that it has become mo

I would characterize these fluid dynamics experiments as "very cute", but nothing more. One of the sad things about physics these days is that it has become more like religion in a bad way. I first heard about Bohmenian mechanics, which this article is about, 8 years ago. I never believed in it, and always thought it was silly. I say "believe" because at this point it really is a question of faith. It was amusing to me to read this article, it makes all the same points I used to argue against but in a very clever and well written way. What the Bohmeanian mechanics people used to say was the only reason they couldn't respond to this or that problem with the theory was "not enough people were working on it". From the article: "Some researchers said that [Bohmean Mechanics] has trouble dealing with identical particles, and that it becomes unwieldy when describing multiparticle interactions. They also claimed that it combines less elegantly with special relativity. But other specialists in quantum mechanics disagreed or said the approach is simply under-researched."

jessaustin 12y ago
I say "believe" because at this point it really is a question of faith. Science. We're doing it wrong.
theophrastus 12y ago
There is no need for "belief". There is only support by predictions validated, or skepticism borne of predictions disproved. The important work should discover predictions which distinguish these two models of the interactions of the very small and then put them to the test. Anyone who remains satisfied with self consistent mathematics alone is, as you say, approaching "religion", (unless it's a thesis in pure mathematics [smile]).
- pmoriarty 12y ago
  Virtually all science relies deeply on belief and trust. Show me the scientist who has replicated every experiment in the scientific texts and journals they read. They don't exist. At some point, you have to trust the system, trust other scientists, trust what you're reading, and believe that the system works. Sure, in principle you might be able to verify any experiment (given enough time and resources, which no one has), but in practice you can't even get close.
dnautics 12y ago
Bohmian mechanics has been mathematically proven to be identical except for certain nonlocal effects, iirc. Interestingly there is also a nonstandard relativity - tangherlini relativity - which is also experimentally indistinguishable from lorentzian relativity except for certain nonlocal effects.
- mtrimpe 12y ago
  What does "certain nonlocal effects" actually mean when put into layman's terms? It sounds convincing but I'm having trouble figuring out what it would actually mean....
  - condnsdmatters 12y ago
    Non-local, in layman's terms, means things in vastly different places being able to affect each other instantaneously. The implication is that it is impossible for one particle to very quickly affect the other by sending a virtual particle (or even message), as this would mean the particle travelling faster than the speed of light (and that would be 'a bad thing'!). So instead of breaking c, we assume things with non-locality that particles 'spookily know'/are affected by things that may possibly be on the other side of the universe. This causes a myriad of problems in the actual physical interpretations. I remember thinking as well, hey why don't we just accept non-locality, but, actually doing physics with it you end run into myriad headscratchers that even make the broken Copenhagen look attractive! One that I did for my MSc was for the case of an single electron in a (harmonic was it?) potential well and solving for a stationary state. By dealing with the Bohmian waveguide model you end up getting that electron is experiencing no overall force - therefore it is literally stationary (serious problems there!) or moving at a constant speed, and could be ANYWHERE in space (non-locality). So your could have 'bound electrons' that are over in Mars or... aren't moving? I'll put up a work through of that if anyone wants to check! Just one example, but my professor (a very thoughtful guy) thought it was cute, had its uses in some applications, but sadly probably not the right story.
    - mtrimpe 12y ago
      I already knew what non-local was, but the examples of no force hence stationary and completely non-local is indeed what I was interested in. Would love to see that worked through in more detail!
simonh 12y ago
Until it is proven experimentally, every scientific theory is just based on belief. Even relativity had to go through this phase. That doesn't mean that theoretical speculation is 'unscientific'. Each individual step in 'doing science' by itself is not the whole of science, but that doesn't make them unscientific. The key is that we distinguish between theories that have experimental evidence and proven predictive power and ones that don't yet have that distinction. Until last year the theoretical framework for the existence of the Higgs Boson could reasonably have been described as 'under-researched'. I do of course completely agree that those fluid dynamics experiments don't count as experimental evidence.
SpaceManNabs 12y ago
Every time I hear people say that physics has become has become a religion I want to stab myself. Every day, I sit at Peyton Hall at Princeton and discussions at the IAS where people are consistently debated. There is nothing dogmatic. If you are wrong, you will get corrected. See BICEP2.
- deleted 12y ago
  [deleted]
- TheOtherHobbes 12y ago
  "Bohmian mechanics has never been widely accepted in the mainstream of the physics community. Since it is not part of the standard physics curriculum, many physicists—probably the majority—are simply unfamiliar with the theory and how it works. Sometimes the theory is rejected without explicit discussion of reasons for rejection. One also finds objections that are based on simple misunderstandings; among these are claims that some no-go theorem, such as von Neumann's theorem, the Kochen-Specker theorem, or Bell's theorem, shows that the theory cannot work. Such objections will not be dealt with here, as the reply to them will be obvious to those who understand the theory. In what follows only objections that are not based on elementary misunderstandings will be discussed." http://plato.stanford.edu/entries/qm-bohm/#o http://plato.stanford.edu/entries/qm-bohm/#o It's true that Bohmian mechanics has never been extended to a full QFT. But considering how little time has been spent on it, isn't it possible this is a result of observed bias against it, and not because it's fundamentally intractable? For comparison, other theories that have ended up in more intractable places (such as string theory) seem to be considered mainstream.
jostylr 12y ago
About identical particles, see my other comment at https://news.ycombinator.com/item?id=8556052 https://news.ycombinator.com/item?id=8556052 But the main point of why Bohmian mechanics over standard quantum mechanics is that the standard one is ill-defined. "Collapse happens when a measurement occurs, but not before." What is a measurement? Trying to make this precise is a problem. Collapse too early and you get the wrong results while collapse too late and you get into the cat paradox. Bohr, I believe, understood this which is why he advocated for a split between classical and quantum with a statement not to worry about the split. There are other ways of dealing with this problem, but Bohmian mechanics is the simplest in my opinion. Instead of something that is sometimes wave-like and sometimes particle-like, we have two things: a wave and a set of particles. The evolution of the particles is governed by the wave. Everything in standard quantum mechanics can be deduced by this picture.

jessaustin 12y ago

I say "believe" because at this point it really is a question of faith. Science. We're doing it wrong.

theophrastus 12y ago

There is no need for "belief". There is only support by predictions validated, or skepticism borne of predictions disproved. The important work should discover predictions which distinguish these two models of the interactions of the very small and then put them to the test. Anyone who remains satisfied with self consistent mathematics alone is, as you say, approaching "religion", (unless it's a thesis in pure mathematics [smile]).

pmoriarty 12y ago
Virtually all science relies deeply on belief and trust. Show me the scientist who has replicated every experiment in the scientific texts and journals they read. They don't exist. At some point, you have to trust the system, trust other scientists, trust what you're reading, and believe that the system works. Sure, in principle you might be able to verify any experiment (given enough time and resources, which no one has), but in practice you can't even get close.

dnautics 12y ago

Bohmian mechanics has been mathematically proven to be identical except for certain nonlocal effects, iirc. Interestingly there is also a nonstandard relativity - tangherlini relativity - which is also experimentally indistinguishable from lorentzian relativity except for certain nonlocal effects.

mtrimpe 12y ago
What does "certain nonlocal effects" actually mean when put into layman's terms? It sounds convincing but I'm having trouble figuring out what it would actually mean....
- condnsdmatters 12y ago
  Non-local, in layman's terms, means things in vastly different places being able to affect each other instantaneously. The implication is that it is impossible for one particle to very quickly affect the other by sending a virtual particle (or even message), as this would mean the particle travelling faster than the speed of light (and that would be 'a bad thing'!). So instead of breaking c, we assume things with non-locality that particles 'spookily know'/are affected by things that may possibly be on the other side of the universe. This causes a myriad of problems in the actual physical interpretations. I remember thinking as well, hey why don't we just accept non-locality, but, actually doing physics with it you end run into myriad headscratchers that even make the broken Copenhagen look attractive! One that I did for my MSc was for the case of an single electron in a (harmonic was it?) potential well and solving for a stationary state. By dealing with the Bohmian waveguide model you end up getting that electron is experiencing no overall force - therefore it is literally stationary (serious problems there!) or moving at a constant speed, and could be ANYWHERE in space (non-locality). So your could have 'bound electrons' that are over in Mars or... aren't moving? I'll put up a work through of that if anyone wants to check! Just one example, but my professor (a very thoughtful guy) thought it was cute, had its uses in some applications, but sadly probably not the right story.
  - mtrimpe 12y ago
    I already knew what non-local was, but the examples of no force hence stationary and completely non-local is indeed what I was interested in. Would love to see that worked through in more detail!

simonh 12y ago

Until it is proven experimentally, every scientific theory is just based on belief. Even relativity had to go through this phase. That doesn't mean that theoretical speculation is 'unscientific'. Each individual step in 'doing science' by itself is not the whole of science, but that doesn't make them unscientific. The key is that we distinguish between theories that have experimental evidence and proven predictive power and ones that don't yet have that distinction. Until last year the theoretical framework for the existence of the Higgs Boson could reasonably have been described as 'under-researched'. I do of course completely agree that those fluid dynamics experiments don't count as experimental evidence.

SpaceManNabs 12y ago

Every time I hear people say that physics has become has become a religion I want to stab myself. Every day, I sit at Peyton Hall at Princeton and discussions at the IAS where people are consistently debated. There is nothing dogmatic. If you are wrong, you will get corrected. See BICEP2.

deleted 12y ago
[deleted]
TheOtherHobbes 12y ago
"Bohmian mechanics has never been widely accepted in the mainstream of the physics community. Since it is not part of the standard physics curriculum, many physicists—probably the majority—are simply unfamiliar with the theory and how it works. Sometimes the theory is rejected without explicit discussion of reasons for rejection. One also finds objections that are based on simple misunderstandings; among these are claims that some no-go theorem, such as von Neumann's theorem, the Kochen-Specker theorem, or Bell's theorem, shows that the theory cannot work. Such objections will not be dealt with here, as the reply to them will be obvious to those who understand the theory. In what follows only objections that are not based on elementary misunderstandings will be discussed." http://plato.stanford.edu/entries/qm-bohm/#o http://plato.stanford.edu/entries/qm-bohm/#o It's true that Bohmian mechanics has never been extended to a full QFT. But considering how little time has been spent on it, isn't it possible this is a result of observed bias against it, and not because it's fundamentally intractable? For comparison, other theories that have ended up in more intractable places (such as string theory) seem to be considered mainstream.

jostylr 12y ago

About identical particles, see my other comment at https://news.ycombinator.com/item?id=8556052 https://news.ycombinator.com/item?id=8556052 But the main point of why Bohmian mechanics over standard quantum mechanics is that the standard one is ill-defined. "Collapse happens when a measurement occurs, but not before." What is a measurement? Trying to make this precise is a problem. Collapse too early and you get the wrong results while collapse too late and you get into the cat paradox. Bohr, I believe, understood this which is why he advocated for a split between classical and quantum with a statement not to worry about the split. There are other ways of dealing with this problem, but Bohmian mechanics is the simplest in my opinion. Instead of something that is sometimes wave-like and sometimes particle-like, we have two things: a wave and a set of particles. The evolution of the particles is governed by the wave. Everything in standard quantum mechanics can be deduced by this picture.