When Bohr got it wrong: the impact of a little-known paper on quantum theory | Hacker News Reader

When Bohr got it wrong: the impact of a little-known paper on quantum theory

physicsworld.com

65 pointssohkamyung26 comments

This is an interesting article due to the historical connections it makes. I mention the paper in question on p. 120 of my book about Noether’s Theorem (https://lee-phillips.org/noether) and quote Heisenberg on why violation of energy conservation, and therefore the paper, was unacceptable (something that the article doesn’t really discuss—after all, other conservation laws were abandoned or modified as needed): it’s because Noether’s Theorem shows that energy conservation is equivalent to invariance with regard to time translation, something that no one would be willing to give up. This means that energy must be conserved in every interaction, not just statistically.

Your book is on my to-read list. :-)

Glad to hear it! I hope you enjoy it.

Michelson–Morley got it wrong too, but getting things wrong, when you know its wrong, its an advancement.

LIGO is better version of Michelson–Morley experiment.

No. Both use Michelson interferometry techonology and that's all, but they differ significantly in purpose and outcome. They're literally different experiments, not one "a better version" of the other.

Michelson and Morley had no chance to find deviations of speed of light in vacuum with their tech, but LIGO did it.

I’d never heard of that… do you have an article about it so I can read up?

The experiment disproved the existence of an ether by measuring that the speed of light was constant regardless of direction…

https://en.wikipedia.org/wiki/Michelson%E2%80%93Morley_exper...

(And special relativity soon showed that if the speed of light is constant, then time itself must be variable.)

The experiment disproved the existence of stationary aether; it didn't disprove the existence of an aether dragged by the Earth.

Relativity is radical. If we interpret it through the concept and language aether, it says that when two observers traveling at different velocities briefly meet at the same time and place, they will each observe an aether that appears to be dragged with them. That is a contradiction: how can the aether be simultaneously dragged in multiple directions at the same spot? So there cannot be an aether. But there must be something else, all the new cruft contained in Relativity, like dilation of time and space.

>But there must be something else, all the new cruft contained in Relativity, like dilation of time and space.

Why must there be something else?

To explain why everyone's interferometer measures the same light speed regardless of its orientation, or their relative motion past the same point.

Ah ok got it.

Thought you were talking about something else entirely. Didn’t realize you meant the specialties of space-time in "special relativity".

I believe GP refers to the fact that they set out to measure the speed of the earth relative to the aether only to discover there was no such thing.

Sorry to come off as a crackpot, but pilot-wave theory did try to fix the problems of BKS by forcing the conservation of energy-momentum in their updated version of the "virtual field".

Of course, Bohm also tried to do a sleight of hand with causality

BKS virtual field -> pilot wave?

https://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory

> “Its radically new approach paved the way for a greater understanding, that methods and concepts of classical physics could not be carried over in a future quantum mechanics.”

This is incorrect. The Hamiltonian in both statistical and quantum mechanics has the same basic structure. Quantization is the only real difference, but the other methods and concepts are structurally the same.

> It was also a crucial factor in Heisenberg’s argument that the probabilistic character of his matrix mechanics (and also of Schrödinger’s 1926 version of quantum mechanics, called wave mechanics) couldn’t be explained away as a statistical expression of our ignorance about the details, as it is in classical statistical mechanics.

Too bad that's an incorrect inference. Bohmian mechanics proves that this inference is incorrect, and it's not the only possibility either.

Quantisation is a pretty big difference: it turns the observables into completely different mathematical objects. Also the Hamiltonian itself only has the same form as in classical physics if at most quadratic in the canonical variables

The parent commenter was talking about Von Neumann mechanics.

That makes no difference

I'm sorry but I think I'm going to believe the man who wrote the article, who is an editor of Nature and has a Physics PhD[1], over someone who has made it their life's work to argue against established scientists on a website for Venture Capitalists :)

[1]: https://en.wikipedia.org/wiki/Philip_Ball

Would you believe two? :-) Bohmian mechanics describes a classical pseudo random number generator that deterministically decides the outcome of quantum measurements, using instant communication between measurements so that conditional probability works. The modern rejection of classical uncertainty as an interpretation of quantum uncertainty stems from Bell's theorem, which shows that any model that achieves a similar philosophical goal as Bohmian mechanics has a similarly dissatisfactory reliance on instant communication. People of Heisenberg's generation had the right intuitions and were guessing in the right directions but they did not know Bell's theorem, or even that it was a worthwhile question.

EPR demonstrated that if you insist on locality and experiments having results in accordance with quantum predictions, then there must be pre-existing elements of reality that determine the results. Bell demonstrated that pre-existing elements of reality and the quantum results of experiments are incompatible with locality. The two together imply that if you assume experiments have results when we say they do in the way quantum mechanics predicts, then there is something nonlocal going on. Hidden variable theories do not add to nor remove the problem of non locality though Bohmian mechanics makes it very clear what the mechanism is.

Many worlds gets around this since experiments do not have definite results in that theory. Instead, the experimenter splits into multiple copies, each of which thinks there is a result of the experiment, but that is an illusion.

No, that is only the case if you assume the experimenter is free to choose the experiment. Bell shows that in that case either locality or realism is violated.

However, there is a simpler explanation, namely superdeterminism. You are in fact not free to choose the experiment, this choice also has physical causes.

If you look at polls of physicists over the past few decades, many believed that Von Neumann's proof ruled out all hidden variable theories. This was wrong. Many others also believed that Bell's theorem ruled out hidden variable theories. This was also wrong, and Bell himself was actually a fan of Bohmian mechanics, which is a non-local hidden variable theory, and one of his motivations for deriving his famous theorem.

All of this is to say that being a physicist doesn't make you an expert in quantum foundations. Neither am I, but I've read a diversity of literature from experts that work on quantum foundations, so I am aware of the range of misconceptions on this.

See here for one of the surveys I mentioned:

https://arxiv.org/abs/1612.00676

To "What is the message of the observed violations of Bell's inequality?", a whopping 37% believed that it ruled out hidden variables entirely, even though Bohmian mechanics has been a thing since the the 1950s. 21% said Bohmian mechanics was explicitly incompatible with Bell's theorem in answering the question "What are your reasons for NOT favoring De Broglie - Bohm theory?", which is clear nonsense.

There's still a lot of confusion about quantum foundations, even among physicists. The fight over superdeterminism has only just begun, even though de Broglie's "double solution" to QM has been around for almost a century as the first superdeterministic theory. And this is ironic given GR is a theory of deterministic evolution of objects over a 4D manifold, eg. the future is already written, but taking this same approach to QM is heresy, even though this would provide some conceptual unity that might bear fruits towards unification.

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