Sandbox (4)

Sometimes very active discussions about peripheral issues overwhelm a thread, so this is a permanent home for those conversations.

I’ve opened a new “Sandbox” thread as a post as the new “ignore commenter” plug-in only works on threads started as posts.

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1,903 thoughts on “Sandbox (4)

  1. Allan Miller: No – single points are seen on a detection device. That does not necessarily mean that each scintillation represents the traversal of a single photon. I could produce a replica of apparent single-particle Young’s slit behaviour using water waves alone, for example, with no passage of actual particles. That’s a ‘hidden variable’ model, I know.

    But the interference pattern is observed even if photons are thrown one at a time (with no detection device) so it’s not that photons interfere with other photons, they seem to interfere with themselves. Excuse me if I misunderstood you objection there

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  2. dazz: But the interference pattern is observed even if photons are thrown one at a time (with no detection device) so it’s not that photons interfere with other photons, they seem to interfere with themselves. Excuse me if I misunderstood you objection there

    But how do we know it’s one photon at a time? We see single flashes, but that’s just quantised detection, and not (necessarily) quantised transfer. If I set up a water-based Young’s slit, and my detector was a set of buckets which only ‘fired’ when full, then we would see an approximation of the single-photon setup. Assuming each bucket started off filled to a random, unknown level, detector firing would appear as if single ‘waterons’ were passing through the apparatus.

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  3. Allan Miller: But how do we know it’s one photon at a time? We see single flashes, but that’s just quantised detection, and not (necessarily) quantised transfer. If I set up a water-based Young’s slit, and my detector was a set of buckets which only ‘fired’ when full, then we would see an approximation of the single-photon setup. Assuming each bucket started off filled to a random, unknown level, detector firing would appear as if single ‘waterons’ were passing through the apparatus.

    They set up the experimental equipment so that is all that only one photon is in the apparatus until it is measured at the barrier. The interference pattern emerges from the single photons.

    This is covered in popularizations. It falsifies the “crowd” interpretations of early QM thinkers, who thought that QM effects could be explained by multiple photons interacting with each other.

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  4. dazz: But the interference pattern is observed even if photons are thrown one at a time (with no detection device) so it’s not that photons interfere with other photons, they seem to interfere with themselves. Excuse me if I misunderstood you objection there

    Just so.

    Becker covers in detail how the main interpretations would describe the Delayed Choice version of double slit.

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  5. BruceS: They set up the experimental equipment so that is all that only one photon isin the apparatus until it is measured at the barrier.The interference pattern emerges from the single photons.

    So how is it established that there are any photons in the apparatus? You supply a photon’s worth of energy, and detect a photon’s worth of energy. But it is not clear – not from these raw facts, at least – that a ‘particle’ has gone through a slit, and excited a specific part of the detector. In my water example, the interference pattern arises from waves of energy, not probability, even though the next detector to fire is unknown and hence probabilistic. No particles are involved; there is no wave function collapse or other shenanigans required to instantiate the detection.

    Are you familiar with W. E. Lamb?

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  6. Allan Miller: For anyone with an interest in QM interpretations. The reason is because one of the behaviours commonly cited is that the pattern disappears when it is ‘known’ which slit is passed through. I’m wondering how that knowledge is gained without interfering with the interference

    Do you know about the delayed choice versions? The slit is effectively closed after the photon passes through but before it hits the barrier to be measured. (Speaking intuitively).

    https://en.wikipedia.org/wiki/Wheeler%27s_delayed-choice_experiment

    But closing after the photon has passed through the slits does not affect on the interference pattern depending on the slits status when measurement occurs (ie by the photon hitting the barrier).

    You’re getting off on the wrong foot by thinking about photons “knowing” about stuff. The formalism gives the math. The wave function reflects entanglement with the experimental apparatus. The quantum entity “obeys” the wave function.

    You cannot use the image of a classical particle with a path that is determined by local forces to understand QM. That thinking fails with QM entanglement which is holistic.

    That holism disappears FAPP at measurement, but how is not part of the formalism. The how has no generally agreed answer — that’s the measurement problem. Decoherence gets you part of the way to a solution, but not all the way.

    The holism is usually represented as the quantum entity entering supersoution with measurement apparatus and then the observing system; see the equation at end of 4.1 here:
    https://plato.stanford.edu/entries/qt-issues/#MeasProb

    As I mention to dazz, each interpretation will explain the experimental results after measurement differently. But they all rely on wave function. The wiki article above touches on Bohm interpretation version. For Bohm, the wave function’s role is captured by the “quantum potential”.

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  7. Kantian Naturalist: That would be great. I’m much more interested in biological cognition than machine learning or any of that stuff, but I should know some basics about machine learning for my philosophy of mind course.

    Here are the other papers I was thinking of to complete by previous reply.

    I read the first brief article but the long second one by the same authors is on my “Maybe Someday” list. It got published in BBS, BTW.

    https://science.sciencemag.org/content/350/6266/1332.full

    https://arxiv.org/abs/1604.00289

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  8. BruceS: I don’t see how retrocausality as a solution to the behavior of entangled QM systems gets you the teleological argument for God, which I thought had more to do with the apparent design of the universe and its components.

    I didn’t think the issue was a solution to entaglement per say, but whether something existed unless it was observed, or in the Super Renninger experiments, even thought of.

    Richard Conn Henry (professor at my grad Alma Mater) summarizes some of the body of thought that I draw upon where he mentions the Renninger experiments, but which I don’t necessarily understand. So, I said “interest”, I didn’t mean to suggest I actually could proficiently defend the viewpoint. 🙂 Not at all!

    http://henry.pha.jhu.edu/The.mental.universe.pdf

    As from the link on the Anthropic Principle, the idea is that observers in the present create the past, or equivalently observers in the future create the present and past. That was depicted in this diagram inspired by John Wheeler:

    Probably the best essay for me personally on retro causality and its role in cosmology (and by way of extension the design argument) is:

    https://www.dhushara.com/book/quantcos/qphil/qphil.htm

    As they approached the galactic beam splitter, the photons must have had something like a premonition telling them how to behave in order to satisfy a choice to be made by unbom beings on a still non-exstent planet. The fallacy giving rise to such speculations. Wheeler explains is the assumption that a photon had some physical form before the astronomer observed it. Either it was a wave or a particle; either it went both ways around the quasar or only one way. Actually, Wheeler says, quantum phenomena are neither waves nor particles but are intrinsically undefined until the moment they are measured.

    Actually, Wheeler says, quantum phenomena are neither waves nor particles but are intrinsically undefined until the moment they are measured. In a sense, the British philosopher Bishop Berkeley was right when he asserted two centuries ago that ‘to be is to be perceived.’ Reflecting on quantum mechanics some 60 years ago, the British physicist Sir Arthur Eddingion complained that the theory made as much sense as Lewis Carroll’s poem ‘Jabberwocky’ in which ‘slithy toves did gyre and gamble in the wabe.’

    Well I tried to study textbook QM, and it helped me understand chemistry and a little solid state physics, but I never got closer to feeling comfortable with the wierder Schrodinger Cat and Retrocausality issues of QM. I feel sort of Ok enough with the plain vanilla stuff of QM that explains the periodic table in chemistry, and maybe a little bit about QM and lasers.

    Sorry if what I said isn’t that helpful to clarifying, I’m working through trying to understand the issues myself, and in many respects you’re much farther along than I in understanding this stuff.

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  9. Allan Miller: So how is it established that there are any photons in the apparatus?

    I agree, particle thinking is at best an intuitive approximation. The best we have now is quantum fields. Particles emerge from that fundamental reality, or at least that is the best we have now in terms of an ontology

    (I’m ignoring Bohm, because it has problems with SR and other issues QFT was meant to address, although that view is only popular among the non-Bohemians!).

    My key point is that you cannot think locally when entanglement is involved.

    Pls be more specific about Lamb reference.

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  10. stcordova: Well I tried to study textbook QM, and it helped me understand chemistry and a little solid state physics, but I never got closer to feeling comfortable with the weirder Schrodinger Cat and Retrocausality issues of QM

    Just the reverse for me!

    Chemistry, biology — too many trees, not enough forest for me. I like the big pictures stuff!

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  11. Allan Miller:

    Discussing this stuff was one of the first times I tried to contribute to TSZ. I remember olegt and Sophisticat had a lot of good things to say, and searching for that conversation, it seems you were asking similar questions 5 years ago.

    They are much better at this than me, so if they could not satisfy you, I definitely won’t!
    http://theskepticalzone.com/wp/bohm-lives-again-aka-was-krishnamurti-right/comment-page-4/#comment-52484

    I wonder what Gregory would make of Quantum Darwinism.

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  12. BruceS,

    You’re getting off on the wrong foot by thinking about photons “knowing” about stuff.

    You have completely misunderstood me, if you think that is what I am saying.

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  13. BruceS,

    Discussing this stuff was one of the first times I tried to contribute to TSZ. I remember olegt and Sophisticat had a lot of good things to say, and searching for that conversation, it seems you were asking similar questions 5 years ago.

    OK, you got me. It may well be that I am simply incapable of understanding this stuff, and I should stick to biochemistry.

    Nonetheless, I am still not sure what is fundamentally wrong with the ‘no-particle’ viewpoint in the thought experiment I repeat here. That cleverer people than me exist, I do not dispute. Carroll on Boltzmann Brains, Oleg et al on quantum matters. I also don’t dispute that Young’s slit experiments can be performed on objects whose particulate nature is less disputable – electrons, even sodium atoms. You can follow their tracks in a cloud chamber, for goodness’ sake, of course they are particles! Nonetheless, the fact that one could simulate particle behaviour in a macro scale apparatus with no particles at all seems to be something to which I keep returning. I need trouble no-one else with these considerations, I guess, but nothing about many-worlds or ‘wave function collapse’ seems at all satisfactory.

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  14. Allan,

    But how do we know it’s one photon at a time? We see single flashes, but that’s just quantised detection, and not (necessarily) quantised transfer.

    That the transfer itself is quantized is revealed by phenomena such as the photoelectric effect. Reduce the frequency of the incident light below a certain threshold, and the photoelectric current drops to zero. That’s not what you’d expect if only the detection, and not the transfer, were quantized.

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  15. keiths:
    Allan,

    That the transfer itself is quantized is revealed by phenomena such as the photoelectric effect.Reduce the frequency of the incident light below a certain threshold, and the photoelectric current drops to zero.That’s not what you’d expect if only the detection, and not the transfer, were quantized.

    I don’t think it’s quite that simple though. I see plenty of discussion in which people regard the photoelectric effect (and Compton scattering, and black body radiation) as unanswerable evidence for the reality of the photon, but others still argue the contrary, coming quite close to the position I am musing over regarding quantisation in the detector (or source) being over-extended to indicate quantisation of the EM wave itself, and hence the passage of ‘a thing’ through one slit or the other. Lamb is often dismissed as a kook on this. I’m just not so sure.

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  16. Allan Miller: Nonetheless, I am still not sure what is fundamentally wrong with the ‘no-particle’ viewpoint in the thought experiment I repeat here.

    Thanks for the Lamb citation. I found another one in the Wiki article on quantum interpretations.

    As best I can tell from a Google scholar citations of that second article, no one in the Quantum Foundations field has seen any reason to do any further work on Lamb’s views.

    As I said in previous post, whether photons exist in the fundamental ontology of the world is interpretations, not physics. It is as much philosophy as physics, maybe best thought of as philosophy heavily constrained by the physics. (BTW, you know that double slit experiments have been done with many other quantum entities, right?).

    The big three realist interpretations — GRW, Many Worlds, and Bohm — all have their own view. Lewis’s quantum ontology book that I linked above in post to Sal is a good overview and is one step beyond a popularization. Bohm haw some kind of quantum particle, Many Worlds only the wave function, and GRW either an ontology that flashes in out of of existence or an ontology that says things are smeared over space (“mass density”). Or at least, that’s my best understanding of them.

    I call these the big three because they are the ones I see most often worked on in the primary and secondary literature. I call them realist because there is another popular interpretation, Quantum Bayesianism, which says no quantum entity is real and quantum experiments should be considered simply ways of updating our knowledge for predicting future results .

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  17. Allan Miller: I don’t think it’s quite that simple though. I see plenty of discussion in which people regard the photoelectric effect (and Compton scattering,

    Reading this and some of what Mr Google says on the controversy:
    I don’t think we are talking about the same thing.

    You seem to be interested in best way of interpreting experiments on light only. Since we are looking at experimental results, that’s ignoring the measurement problem. So it is not the same issue that I am concerned with in my posts. I’m interested in what QM theory overall is saying about the nature of the world.

    ETA To expand on my point: Similarly, to your question about photons, we can also ask: Are particles of the standard model real? Are water molecules real? Are genes real? Is biological fitness real? Is economic inflation real?

    In all cases, one answer is to say that any entity which is a necessary part of our best scientific theories in that domain is real.

    So the argument about photons seems to me to be about whether photons are a necessary part of out best EM/QFT theories, based on experiments in that domain of science.

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  18. To me, the problem is not real vs not real, but whether current interpretations are final. When I first encountered particle/wave duality, I chose to believe it’s going to be like that all the way down. Realness is transcendental. To realize is to construct an understanding.

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  19. petrushka:
    To me, the problem is not real vs not real, but whether current interpretations are final. When I first encountered particle/wave duality, I chose to believe it’s going to be like that all the way down. Realness is transcendental. To realize is to construct an understanding.

    I think you are saying metaphysics is philosophy, not science. In which case I agree.

    But when doing metaphysics, you can try to keep the stuff that is not science to a minimum as in eg
    https://www.amazon.com/Scientific-Metaphysics-Don-Ross/dp/019874410

    Or you can make up a lot of stuff and then obsess about that, as in this Thomist thread from PS
    https://discourse.peacefulscience.org/t/a-thomistic-approach-to-chemistry/6894/1

    or this one
    https://discourse.peacefulscience.org/t/aristotelian-thomistic-philosophy-and-scientific-evidence/6953

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  20. Allan,

    Nonetheless, the fact that one could simulate particle behaviour in a macro scale apparatus with no particles at all seems to be something to which I keep returning.

    How would you simulate the photoelectric effect with the water-based setup you’ve been discussing?

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  21. One of the solutions to the Schrodinger equation is a wave-packet, it is particle-like, it is one way to depict a photon:

    The derivation of this “moving” solution to Schrodinger’s equation was in Griffiths book, IIRC.

    My understanding is that this would apply also to “harder” particles like electrons and protons, etc.

    I could be wrong though, but that’s sort of the way I remember it in class.

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  22. From Griffiths page 64, 2nd Ed.

    Figure 2.11 A wave packet. The “envelope” travels at a group velocity, the “ripples” travel at the phase velocity.

    Hence we can get a lot of wave behavior under this model. I believe the “wave” here in Griffiths is the square root of probability amplitude.

    Also, if we presume “harder” particles like electrons also have probability amplitudes (ala de Broglie), then these will also have similar statistics and can be modeled as wave packets. But I think that’s getting into Quantum Field Theory, which I hear is miserably difficult.

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  23. Kantian Naturalist: That would be great. I’m much more interested in biological cognition than machine learning or any of that stuff, but I should know some basics about machine learning for my philosophy of mind course.

    This recent post by Gopnik at Edge is also relevant.
    She says AI should take more heed of how the child’s brain/mind works, and pay less attention to the adult brain/mind.

    Key differences: plasticity, less constrained exploration, more openness to cultural input, more reliance on emotional support and feedback of caregivers
    https://www.edge.org/conversation/alison_gopnik-a-separate-kind-of-intelligence

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  24. “I wonder what Gregory would make of Quantum Darwinism. – BruceS”

    Not much. Using Darwin’s name for many things he never thought, wrote about or discussed has become common. Trying to add appeal to something simply by naming it ‘Darwinist’ or ‘Darwinian’ as if that provides some kind of interdisciplinary validity or authority over it is indeed the aim of some people.

    Quid pro quo:
    Given that he seems to promote (or at least simply express) here a similar ‘naturalism’ (meaning non-theism, irreligion) as KN, I wonder what BruceS makes of ‘religious naturalism’.

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  25. Gregory:
    I wonder what BruceS makes of ‘religious naturalism’.

    What is it?

    In any event, nice to see someone reads my posts.

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  26. stcordova: Also, if we presume “harder” particles like electrons also have probability amplitudes (ala de Broglie), then these will also have similar statistics and can be modeled as wave packets. But I think that’s getting into Quantum Field Theory, which I hear is miserably difficult.

    Yes to second point.
    On first point I think you may have the logic reversed. It’s the quantum fields that are more fundamental. Quantum fields are primary, then particles depend on them for explanation or emerge from them for ontology.

    I don’t know how or even if the waves of the non-relativistic QM are reflected in QFT.

    https://www.forbes.com/sites/startswithabang/2018/11/17/ask-ethan-are-quantum-fields-real/#6bed24fc777a

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  27. BruceS:

    Quantum fields are primary, then particles depend on them for explanation or emerge from them for ontology.

    Yes, thank you for the correction!

    I don’t know how or even if the waves of the non-relativistic QM are reflected in QFT.

    My QM professor said, the more complete description of QM includes relativity, but then we would have to drop the Schrodinger Equation (which is “easier”, ha, “easier”) in favor of Klein Gordon Field equations which include SPECIAL relativity, and which are much harder.

    It is acknowledged that although QM and SPECIAL relativity work well together, QM and GENERAL relativity do not. That’s my meager understanding/misunderstanding anyway…

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  28. BruceS: What is it?

    Ah, so it’s still necessary positions dressed as positionlessness? No will to believe? Surely you know what a search engine is. = P

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  29. Gregory: Ah, so it’s still necessary positions dressed as positionlessness? No will to believe? Surely you know what a search engine is. = P

    Um, I was just trying to understand the phrase “religious naturalism”

    ETA: I did search but could find no consistent definition. The phil of religion stuff I have tends to treat the two words as implying contradictory positions.

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  30. stcordova:

    My QM professor said, the more complete description of QM includes relativity, but then we would have to drop the Schrodinger Equation (which is “easier”, ha, “easier”) in favor of Klein Gordon Field equations which include SPECIAL relativity, and which are much harder.

    It is acknowledged that although QM and SPECIAL relativity work well together, QM and GENERAL relativity do not.That’s my meager understanding/misunderstanding anyway…

    I don’t know how KGF equations fit into QFT; FWIW the named equations do appear in some of the QFT intros I have collected by not read.

    The current incompatibility of BR and QFT is also my understanding of the state of fundamental physics..

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  31. BruceS: Sean C intros many of the topics discussed in above in latest After On Podcast.
    https://after-on.com/episodes-31-60/052

    If you prefer a transcript, it is supposed to be repeated on Sean’s Mindscape at some point, and he includes transcripts.
    https://www.preposterousuniverse.com/podcast/

    Looks like the transcript is up https://www.preposterousuniverse.com/podcast/2019/07/15/55-a-conversation-with-rob-reid-on-quantum-mechanics-and-many-worlds/

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  32. Just as an FYI for completeness (not that I understand how this works), there is the field of Relativistic Quantum Chemistry:

    https://en.wikipedia.org/wiki/Relativistic_quantum_chemistry

    Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to explain elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example of such an explanation is the color of gold: due to relativistic effects, it is not silvery like most other metals.

    The term relativistic effects was developed in light of the history of quantum mechanics. Initially quantum mechanics was developed without considering the theory of relativity.[1] Relativistic effects are those discrepancies between values calculated by models that consider and that do not consider relativity.[2] Relativistic effects are important for the heavier elements with high atomic numbers. In the most common layout of the periodic table, these elements are shown in the lower area. Examples are the lanthanides and actinides.[3]

    Relativistic effects in chemistry can be considered to be perturbations, or small corrections, to the non-relativistic theory of chemistry, which is developed from the solutions of the Schrödinger equation. These corrections affect the electrons differently depending on the electron speed relative to the speed of light. Relativistic effects are more prominent in heavy elements because only in these elements do electrons attain sufficient speeds for the elements to have properties that differ from what non-relativistic chemistry predicts.[citation needed]

    Again the chemistry relativity here (as I understand it) is SR (special relativity) not GR (General Relativity), where GR is a theory of gravity and acceleration and contains SR, SR involves relative velocity, not acceleration nor gravity. SR is a special case of GR where acceleration and gravity equal zero.

    On aspect of QM stuff that involves SR is the Pauli Exclusion principle which limits the sort of electrons that can occupy an orbital based on spin. How Pauli figured this out is amazing, and I don’t know how, but he won the Nobel Prize for doing so.

    Here’s a picture of Bohr and Pauli looking at a top. Gotta love it — two of the greatest physicists of all time amusing over a kid’s toy together that illustrate an analogy to QM spin:

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  33. stcordova: Here’s a picture of Bohr and Pauli looking at a top. Gotta love it — two of the greatest physicists of all time amusing over a kid’s toy together that illustrate an analogy to QM spin:

    I only know enough QM to understand the related philosophy/QM Foundations work. I have no knowledge of actual applications like chemistry (or of chemistry in general). I did enough QM theory to understand that QM harmonic oscillator; that is as close to an application as I get.

    What you say about SR and acceleration is a common belief, I think, but SR can handle an accelerating object a s long as the spacetime remains flat. For the general case of spacetime curbed by mass/energy, you need GR
    http://www.math.ucr.edu/home/baez/physics/Relativity/SR/acceleration.html

    I had not heard that Pauli’s exclusion principle was related to SR. Do you have a reference for that?

    I’d be careful of comparing spin as a classical property to the spin that names a qm observable. eg, in QM up spin is superposition of spins in eg left/right basis, but there is nothing like superposition classically. (“Basis” is used in the vector space sense, of course).

    Pauli was a brilliant physicist. Bohr was a brilliant organizer/inspirer, but not in the first rank of the physicists of that day. He also wrote vague, obscure QM philosophy (or at least, the QM Foundations people I respect think that).

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  34. BruceS:

    What you say about SR and acceleration is a common belief, I think, but SR can handle an accelerating object a s long as the spacetime remains flat.

    Special relativity is framed in terms of Inertial Reference frames which are defined as:

    https://en.wikipedia.org/wiki/Inertial_frame_of_reference

    An inertial frame of reference in classical physics and special relativity possesses the property that in this frame of reference a body with zero net force acting upon it does not accelerate; that is, such a body is at rest or moving at a constant speed in a straight line

    SR is defined in terms of inertial frames.

    https://en.wikipedia.org/wiki/Postulates_of_special_relativity

    . First postulate (principle of relativity)

    The laws of physics are the same in all inertial frames of reference.
    2. Second postulate (invariance of c)

    As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body. Or: the speed of light in free space has the same value c in all inertial frames of reference.

    One can make approximations using SR with accelerations, but the results would not be exact.

    GR deals with gravity. Einstein’s equivalence principle says there is an equivalence with gravity and acceleration.
    https://en.wikipedia.org/wiki/Equivalence_principle

    a basic postulate of general relativity, stating that at any point of space-time the effects of a gravitational field cannot be experimentally distinguished from those due to an accelerated frame of reference.

    So GR deals with accelerated frames of reference. Curved Spacetime is due to gravity. Obviously then a LOT of applications of SR must be approximations since the effect of gravity is like everywhere!

    The book I studied GR from is below. Like QM there is so much I’ve forgotten and so much I should know, but don’t. Meaning, everything I say about this stuff feels provisional!

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  35. BruceS: I had not heard that Pauli’s exclusion principle was related to SR. Do you have a reference for that?

    Hi,

    From:

    https://en.wikipedia.org/wiki/Pauli_exclusion_principle

    In relativistic quantum field theory, the Pauli principle follows from applying a rotation operator in imaginary time to particles of half-integer spin.

    Perhaps my wording wasn’t good as I was going by memory. I think it is better stated the way Wiki stated it! That said, it would appear without SR (relativistic Quantum Field Theory), one could not derive Pauli Exclusion.

    Again from memory, I seem to recall the professor (who taught both my classes in QM and GR), said, QM and SR go well together, some problems with QM and GR, and that relativistic QFT means the relativity is SR, not GR.

    That said if something is orbiting, it’s in an accelerated reference frame, so this would suggest GR! Atoms have lots of stuff rotating! So I don’t know how to reconcile some of what I just said about my recollection that the relativistic QFT must be framed in SR!

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  36. For the reader’s benefit, I think the first few paragraphs describing what QM is, is one of the best I’ve seen. Like many tech articles on wiki, sometimes it is written by professors, and this one looks like it was written by a collection of professors:

    https://en.wikipedia.org/wiki/Quantum_mechanics

    Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.[2]

    Classical physics, the physics existing before quantum mechanics, describes nature at ordinary (macroscopic) scale. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale.[3] Quantum mechanics differs from classical physics in that energy, momentum, angular momentum and other quantities of a bound system are restricted to discrete values (quantization); objects have characteristics of both particles and waves (wave-particle duality); and there are limits to the precision with which quantities can be measured (uncertainty principle).[note 1]

    Quantum mechanics gradually arose from theories to explain observations which could not be reconciled with classical physics, such as Max Planck’s solution in 1900 to the black-body radiation problem, and from the correspondence between energy and frequency in Albert Einstein’s 1905 paper which explained the photoelectric effect. Early quantum theory was profoundly re-conceived in the mid-1920s by Erwin Schrödinger, Werner Heisenberg, Max Born and others. The modern theory is formulated in various specially developed mathematical formalisms. In one of them, a mathematical function, the wave function, provides information about the probability amplitude of position, momentum, and other physical properties of a particle.

    Important applications of quantum theory[5] include quantum chemistry, quantum optics, quantum computing, superconducting magnets, light-emitting diodes, and the laser, the transistor and semiconductors such as the microprocessor, medical and research imaging such as magnetic resonance imaging and electron microscopy. Explanations for many biological and physical phenomena are rooted in the nature of the chemical bond, most notably the macro-molecule DNA.[6]

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  37. stcordova: Special relativity is framed in terms of Inertial Reference frames which are defined as:

    Right, it is not the reference frames that are accelerating, just particles within them. Such particles have curved worldlines in inertial frames.

    I’m not sure why think the equivalence principle means accelerating bodies cannot be modeled in inertial frames.

    Thanks for the Pauli reference. Looks to be beyond my pay grade.

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  38. keiths:
    Allan,

    How would you simulate the photoelectric effect with the water-based setup you’ve been discussing?

    FWIW, I don’t see how you could use water to model results of delayed choice either. Allan’s water arguments remind me of J-Mac GR on a pool table experiments.

    Allan apparently has pulled an Eric on this discussion. But I did find this physics stack exchange which I found helpful. As far as I can tell, most think photons have the same ontological status as other entities in the standard model.
    https://physics.stackexchange.com/questions/273032/what-exactly-is-a-photon

    The linked blog post by Motl which “helps in understanding how the classical electromagnetic field emerges from a large confluence of photons [but] needs the mathematics of quantum field theory” seems to be germane based on a skim, but I don’t have the background to fully understand it, I read the summary as implying starting with the EM fields to explain the quantum gets the order of explanation backwards.
    http://motls.blogspot.com/2011/11/how-classical-fields-particles-emerge.html

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  39. BruceS:

    I read the summary as implying starting with the EM fields to explain the quantum gets the order of explanation backwards.
    http://motls.blogspot.com/2011/11/how-classical-fields-particles-emerge.html

    GREAT LINK!

    My understanding is that EM fields (the fluid model of EM) is the classical model. 1st day of EM theory professor outlines the perspectives of EM.

    The Classical “fluid” model of Maxwell ( from which actually Einstein found inspiration for SR).

    I seem to recall other models, but the final one was Relativistic Quantum Electro Dynamics, or QED.

    https://en.wikipedia.org/wiki/Quantum_electrodynamics

    In particle physics, quantum electrodynamics (QED) is the relativistic quantum field theory of electrodynamics. In essence, it describes how light and matter interact and is the first theory where full agreement between quantum mechanics and special relativity is achieved. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons and represents the quantum counterpart of classical electromagnetism giving a complete account of matter and light interaction.

    When James Trefil taught me elementary QM, he pointed out the classical view of EM would fail for an orbiting electron or something like that. It was something that caused Bohr to postulate away the problem . I think Dr. Trefil was relating this:

    The electron is able to revolve in certain stable orbits around the nucleus without radiating any energy contrary to what classical electromagnetism suggests. These stable orbits are called stationary orbits and are attained at certain discrete distances from the nucleus. The electron cannot have any other orbit in between the discrete ones

    https://en.wikipedia.org/wiki/Bohr_model

    So I agree, invoking CLASSICAL EM at the atomic level is backward, and won’t work.

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  40. stcordova: GREAT LINK!

    Here is one for you on a spreading metaphor for entropy that you may want to use in your ongoing battles with Keith.

    FWIW, I think the author is an eccentric in this matter as Lamb is in the matter of photons. Keith is giving the consensus view of the best way to understand Stat Mech entropy as a reduction of TD entropy. (See Wiki on Gibbs paradox, for example, for consensus view)

    Entropy, Its Language and Interpretation
    https://www.cpp.edu/~hsleff/entlangint.pdf
    [from abstract]
    “We argue in favor of the descriptor spreading, which entails space, time, and energy in a fundamental way. This includes spreading of energy spatially during processes and temporal spreading over accessible microstates states in thermodynamic equilibrium”

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  41. Thanks BruceS.

    I’ve said, the spreading metaphor is a good approximation to understanding. But a metaphor has it’s limits.

    If one really wants the rigorous approach definition it’s

    dS = dQrev/T

    or

    S = kB log W

    The argument over the spreading metaphor is it’s pedagical value, I’m not arguing for its absolute correctness any more than I’m arguing classical physics is absolutely correct!

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  42. Regarding Iran, could the USA inflict a lot of damage on the country without dropping bombs?

    The USA shot down an Iranian Drone with something akin to a death ray, but in many respects could be a souped up microwave oven.

    If the microwaves can be focused like a laser (the right term is MASER), then it can fry the electronics brains and nervous system of a machine and effectively neutralize it. I don’t believe the system used to take down the drone was necessarily a MASER, but it was adequate.

    There are “brains” needed to run power grids, and selective disruption of the control systems could take it down for hours and days. Could it take down aircraft, like military aircraft? No one is saying, but what’s stopping it from being used on aircraft? Or nothing is stopping it from being used on all sorts of infrastructure facilities like telecommunication or server farms. I nice little zap could wipe out electronics without necessarily killing anyone. Understandably the military isn’t disclosing its full electronic capabilities.

    When I worked in the aviation industry a while back, it was so blatantly obvious aircraft could be taken down, or have their safety compromised by electronic attacks (eh, the FAA regulations require shutting off cell phone transmission because there is a remote possibility it could mess with instrument landing equipment, not too bad during a visual approach and landing, but an instrument approach and then a full up near blind landing in really bad weather? Yikes!). Suffice to say, there were conversations and concerns on this topic. Just be grateful terrorist aren’t sophisticated enough to use electronic warfare and instead resort to less destructive old style suicide bomb approach to killing.

    But I suppose the drone shoot down by the US COULD be a warning to Iran, “don’t mess with us, we don’t even need to drop bombs to inflict serious damage, and you won’t even know the USA did it.”

    This of course is speculation. Of course, to know the full capability, one might need access to classified information.

    Any way, the Chinese aren’t bashful about advertising their work on this:

    https://www.popsci.com/china-microwave-weapon-electronic-warfare/

    China can find a wide variety of uses for an electronics killing ray. Defensively, microwave weapons could be part of electronic warfare booby traps, ambushing and disabling enemy vehicles and robots. At close ranges, it can be mounted on vehicles, warships, and even aircraft, to disable and distract missiles, small UAVs and even the personal and vehicular electronics of hostile forces.

    The US has some microwave missiles, but I would presume how it works is somewhat guarded:

    https://www.c4isrnet.com/electronic-warfare/2017/12/13/making-sense-of-champ-the-silver-bullet-miracle-missile-that-isnt/

    CHAMP is a missile that can emit targeted blasts of microwaves to fry electronics, without damaging the electronics in the way an explosive might. That alone is a strange and novel capability, and one worth reporting on as such. It is especially novel as the rare weapon that produces an electromagnetic effect, designed to disable computers, that isn’t also a nuclear weapon simultaneously producing some other, more pressing effects.

    So why did Trump not order an electronic warfare strike on Iran instead of sending an attack with explosives (and then recalling the strike)? I don’t think anyone on the outside knows and is telling the whole story.

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