Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Let us assume Feynman was wrong.

  1. Mar 30, 2009 #1
    After summing up the rudiments of quantum mechanics Feynman tries to answer a question that readers might have at this point of his book, The Feynman Lectures on Physics, Vol. III, page 1-10.1. He writes,

    "One might still like to ask: "How does it work? What is the machinery behind the law?" No one has found any machinery behind the law. No one can "explain" any more than we have just "explained". No one will give you any deeper representation of the situation. We have no ideas about a more basic mechanism from which these results can be deduced. ... "

    Assume Feynman was wrong, please give me a deeper representation of the situation.

    Thank you for your thoughts.
     
  2. jcsd
  3. Mar 30, 2009 #2
    Assuming Feynman was wrong leaves us with theories. I have my own; I don't like to share it over the internet (sorry, nothing personal, I'm just not comfortable with being to open about it). I don't think most would be.

    I can tell you this: if you want to know why a particle has probabilities of being in different places or states, then Quantum Mechanics is the last place to look. QM is all about math, probability amplitudes, wave/ particle duality. This is an explanation of what happens, not why it happens. So, in my opinion, there has to be an underlying cause, where one measures what QM states should happen, but the actual action of the particles is based on principles which one might need to invent. Einstein had this kind of thought. General Relativity was a huge leap that described nature. There has to be one for QM too. As far as what it is, I have used certain principles of Relativity. My personal thoughts are that we don't need to quantify gravity; we need to relativize QM.
     
  4. Mar 30, 2009 #3
    What you seem to be asking for is a derivation of QM from more basic principles. What more basic principles could there possibly be? By definition basic principles apply to a broad range of situations, and not just a few. And I suppose that the most basic principles that apply to everything are the principles of logic and reason. I don't believe that anyone is going to argue that there is anything in reality that does not comply with reason, is there? So I have to wonder if the laws of physics (QM, in this case) can be derived from logic. If physics could be derived from logic, then that would be the completion of physics. We would no longer be able to question where physics came from since the answer would be that it comes from reason itself, and how do you question that?
     
  5. Mar 31, 2009 #4
    Spinnor, (and everyone) did you know there is a school of thought that quantum behavior is simply the result of classical (but relativistic) elecytrodynamics when done properly. By properly here I mean including the effects of delay and radiation damping.

    Here is an example paper, that was published in the peer-reviewed literature (Found. Phys. 34 (2004) 937--62), "The electrodynamic 2-body problem and the origin of quantum mechanics", C. K. Raju, on arxiv here: http://arxiv.org/abs/quant-ph/0511235 . Within the rules here I cannot cite everything I would like. There are more papers on arxiv than have made it into print as of yet. A very important paper in this area is one by Jayme De Luca, Physical Review E, vol. 73, 026221 (2006), "Stiff three-frequency orbit of the hydrogen atom ", on arxiv here: http://arxiv.org/abs/physics/0511179 .

    On arxiv if you click the author name on the abstract pages you will see all the other papers by that author in the category of the abstract.

    Also I could recommend many other mainstream peer-reviewed journal articles. A good approach is to look at the references in those two papers. Many of them are too old to be on arxiv but you may find more recent papers there by some of the authors. David Hestenes' published works are posted on his website (along with applicable mainstream peer-reviewed journal citations) which may be navigated to from the wikipedia article about him.
     
    Last edited by a moderator: Apr 24, 2017
  6. Mar 31, 2009 #5

    Demystifier

    User Avatar
    Science Advisor

    A possible deeper representation is provided by the Bohmian (pilot wave) interpretation. In particular, the recent lectures presented here:
    http://www.tcm.phy.cam.ac.uk/~mdt26/pilot_waves.html
    emphasize the point that Feynman was wrong that a deeper explanation is not possible.
     
  7. Mar 31, 2009 #6
    Actually, any interpretation does the same. BTW Feynman prefered 'shut up and calculate' interpretation.
     
  8. Mar 31, 2009 #7

    dx

    User Avatar
    Homework Helper
    Gold Member

    Feynman was not wrong. There are no widely accepted ideas from which quantum mechanics can be deduced.
     
  9. Mar 31, 2009 #8
    Wheeler was closest with 'we all live in a giant computer' - if this is the case its all quite easy to understand. It needs an 'information space' from which data 'creates' ordinary thee dimensional space and objects within it.
    This information lies outside space but has time IMO).
    But its hard to swallow that we are all made of 0s and 1s - as is space itself. There are few takers of this theory but to me its blindingly obvious.
     
  10. Mar 31, 2009 #9

    jtbell

    User Avatar

    Staff: Mentor

    I think Feynman's quote refers to the fact that there is no generally accepted interpretation of QM. Lots of people certainly do have ideas about what "lies behind" the mathematics of QM. The problem is that there are a bunch of different interpretations, and no way (so far) to decide among them by experiment, because they're constructed to reduce to the standard mathematics of QM for predictions of the results of actual experiments.
     
  11. Mar 31, 2009 #10
    I'm afraid he was. Most of Feynman's sweeping statements about QM for a general audience refer to the two-slit experiment. He devotes nineteen pages of The Character of Physical Law to this - with repeated statements such as 'Many ideas have been concocted to try to explain [this interference pattern] in terms of individual electrons going round in complicated ways through holes. None of them has succeeded.' and 'A phenomenon which is impossible, absolutely impossible to explain in any classical way.. in reality it contains the only mystery'. This is as well as your 'How does it really work? What machinery is actually producing this thing? Nobody knows any machinery.'

    What Demistifyer is saying (and I followed that lecture course as well) is that de Broglie-Bohm pilot-wave theory (which basically says there is a particle and a wave') provides exactly the machinery that Feynman says is 'absolutely impossible.' It doesn't matter whether pilot-wave theory has anything to do with reality or not. The point is that Feynman says no-one knows any machinery - but they do.
    And that's interesting - particularly as Feynman knew Bohm well - (see Towler's Lecture 7). Presumably he just had a simple message which he wanted to convey (the two-slit experiment is not visualizable in QM terms) and he just wanted to stick to that.

    As John Bell said:

    'Is it not clear from the smallness of the scintillation on the screen that we have to do with a particle? And is it not clear, from the diffraction and interference patterns, that the motion of the particle is directed by a wave? De Broglie showed in detail how the motion of a particle, passing through just one of two holes in the screen, could be influenced by waves propagating through both holes. And so influenced that the particle does not go where the waves cancel out, but is attracted to where the cooperate. This idea seems to me so natural and simple, to resolve the wave-particle dilemma in such a clear and ordinary way, that it is a great mystery to me that it was so generally ignored.'

    So basically pilot-wave theory has the same results as QM, but it has the advantage of having qualitative explanations and 'mechanism' as well. There's got to be something to be said for making things comprehensible for students surely..? But the violent vituperation that has been dumped on this theory since its pre-Copenhagen proposal - (just because it shows many of the impossibility statements by the Founding Fathers to be profoundly mistaken, and we're not allowed to be rude about them) - is extraordinary.

    Remember Bohr's definition of complementarity: 'There is no logical picture (obeying classical propositional logic) that can simultaneously describe and be used to reason about all properties of a quantum system.' - essentially because of the incompatibility of wave and particle descriptions. Er.. except if - as de Broglie said - if you have waves and particles then everything is obvious - but somehow they missed that.. Hmmm.
     
  12. Mar 31, 2009 #11

    dx

    User Avatar
    Homework Helper
    Gold Member

    As I said, there's no widely accepted way to deduce quantum mechanics from more fundamental ideas or to provide some classical mechanism. Bohm's theory has many problems, and is at best redundant, but let's not turn this into a discussion of that.
     
  13. Mar 31, 2009 #12
    [Amused grin]

    So Feynman says nobody knows any machinery.

    I point out that somebody does know some machinery.

    You imply that this is irrelevant, because not many people know this, therefore Feynman is correct, and thus nobody knows any machinery.

    I love your logic!

    [PS: I agree - it serves no purpose. to discuss pilot-wave theory here - if people are interested they can read the lecture notes Demystifier referred to. But, just for the record, there are no problems with it that anyone has ever been able to substantiate - as always it is just a matter of opinion. However, it does provide machinery - so really what you are saying is that 'machinery' itself is redundant - not just that Bohm's (in fact de Broglie's) theory is redundant. A fair number of people would disagree with you on that, but of course you don't care, and why would you...? :wink:]
     
  14. Mar 31, 2009 #13

    dx

    User Avatar
    Homework Helper
    Gold Member

    I'm not saying machinery is redundant. I'm saying there's no machinery behind quantum mechanics that is widely accepted. I'm sure you know that there are a lot of disagreements among physicists about Bohm's theory, and it is a controversial thing. It certainly claims to provide a machinery for QM, but it is not a settled issue. That's all I'm saying.
     
    Last edited: Mar 31, 2009
  15. Mar 31, 2009 #14
    I think Max Tegmark is right
    There is no machinery at all, just equations.
    Ultimately, "**** up and calculate" is right - not as a denial to understand the underlying machinery, but as understanding that there is no machinery at all.

    P.S.
    Hm... the famous Feynmann interpretation is automatically replaced with ****....
     
  16. Mar 31, 2009 #15
    Christ - the philosophers would have a field day with you..

    The Original Poster quotes Feynman as saying 'nobody knows any machinery' - a statement which we now know is incorrect.

    You state that Feynman is not incorrect - he is correct. Thus you imply 'nobody knows any machinery'.

    As long as the relevant machinery is not demonstrably false (which it isn't) the logical flow here has nothing to do with how 'widely accepted' the machinery is, so I fail to see what point you are trying to make.

    The machinery Demystifer and I referred to is fully compatible with all observations, so one cannot rule out that machinery of this nature genuinely exists.. And since it makes comprehensible the 'reality of a quantum event', one might as well imagine this to be the case while we await further evidence. At the very least freshman students would be less confused..


    [PS: Look - I can edit my own post to make it look better after people reply to it as well!]
     
    Last edited: Mar 31, 2009
  17. Mar 31, 2009 #16
    Just so long as we understand that 'there is no machinery at all' is an interpretation just like any other.

    (And in my opinion a damned unlikely one - otherwise why does anything do anything? :rolleyes:)

    Now I wonder if you mistyped 'shut' as '****' (just testing).
     
  18. Mar 31, 2009 #17
    Check Max Tegmarks "Mathematical Universe"
    Just equations, and nothing else.
    The questions about the "machinery" behind are silly, like "what numbers are made of?"
     
  19. Mar 31, 2009 #18

    dx

    User Avatar
    Homework Helper
    Gold Member

    That's another common misunderstanding of what "interpretations of quantum mechanics" are about. It's not a pointless desire to visualize some "machinery" behind the equations. Theories of physics consist of two parts. One is a mathematical structure [tex] M [/tex], and the other is a way to relate that structure to experience, i.e. a map from experience to the mathematical structure. In all the theories discovered before quantum mechanics, the "interpretation" part was obvious, and never needed to be explicitly discussed. No one needed to tell you what a world-line was when you learned special relativity. It was clear what the elements of the mathematical structure of SR like events, world-lines etc. corresponded to in experience. This changed in QM. For many problems of practical interest, one knew how to apply QM. But it wasn't so clear in all cases. This is the problem of the interpretation of quantum mechanics. To define unambiguously how to relate the mathematical structure of QM to experience.
     
  20. Mar 31, 2009 #19

    dx

    User Avatar
    Homework Helper
    Gold Member

    Do we also know that special relativity is wrong? Many crackpots claim it is. I think it's pretty clear that what Feynman meant was that no machinery that is widely accepted has been found.

    I have no idea what you're talking about.
     
  21. Mar 31, 2009 #20

    dx

    User Avatar
    Homework Helper
    Gold Member

    Also, you keep saying Bohm's mechanics is fully compatible with observations. I don't want to turn this into a discussion of this theory, but you don't seem to get that not everyone agrees with this view . You may agree with it, but it is not established fact.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Let us assume Feynman was wrong.
  1. Feynman diagram (Replies: 2)

  2. Feynman on reflection (Replies: 3)

  3. Feynman Diagrams (Replies: 2)

  4. Feynman rules (Replies: 0)

Loading...