• apokrisis
    3.2k
    Post that on Physics Forum I dare you. :)
  • Rich
    3.1k
    Post that on Physics Forum I dare youapokrisis

    Don't want to upset too many of them during their fund raising efforts. You think I take them any more seriously than the average myth maker. Rather than read the actual works they read Wikipedia (like others who say Bohmian Mechanics is deterministic).
  • Wayfarer
    5.3k
    Your approach is confusing as you start off suggesting that rate ought to matter.apokrisis

    But if it's a wave, how can the rate NOT matter? Remember, the phenomenon at issue is interference. And interference implies interaction. You're prepared to say that 'particles interfere with themselves', but how is that any less confusing?

    Furthermore, what is 'the path' defined by? There is no actual 'path' in reality, unless you accept the pilot-wave theory, which you have said you don't. So they follow 'a path' - what is the path defined by? I am saying, it's not defined by something in time.

    So - I don't see my approach as 'confusing'. As far as I'm concerned, I have asked a novel question.
  • Rich
    3.1k
    So - I don't see my approach as 'confusing'. As far as I'm concerned, I have asked a novel question.Wayfarer

    It's a great observation, and when the experts are embarrassed (because they really don't get it), they call it gobblygook. Bohm agrees with you. What matters is the form for the information. For further reading I recommend Science, Order, Creativity by Bohm, Hiley.
  • Wayfarer
    5.3k
    That's how it struck me. If you look at the thread, you will notice I chose not to argue the case. But what it seems to me is that, as soon as I ventured something beyond the physics - i.e. into a meta-physical observation - then there's an instant red flag.

    The girl on the Physics Stack exchange explicitly said, well, time is not a boundary factor in this experiment. And I asked: this means, it's a timeless wave? Where else in physics would you see something analogous? I didn't get an answer, but for all I know, there might be a quotidian answer to that question.

    But I still think I'm onto something novel, here. :-)
  • WISDOMfromPO-MO
    720
    "Our illusion of the past arises because each Now in Platonia contains objects that appear as "records" in Barbour's language. "The only evidence you have of last week is your memory. But memory comes from a stable structure of neurons in your brain now. The only evidence we have of the Earth's past is rocks and fossils. But these are just stable structures in the form of an arrangement of minerals we examine in the present. The point is, all we have are these records and you only have them in this Now." Barbour's theory explains the existence of these records through relationships between the Nows in Platonia. Some Nows are linked to others in Platonia's landscape even though they all exist simultaneously. Those links give the appearance of records lining up in sequence from past to future. In spite of that appearance, the actual flow of time from one Now to another is nowhere to be found.

    "Think of the integers," he explains. "Every integer exists simultaneously. But some of the integers are linked in structures, like the set of all primes or the numbers you get from the Fibonacci series." The number 3 does not occur in the past of the number 5, just as the Now of the cat jumping off the table does not occur in the past of the Now wherein the cat lands on the floor." (emphasise mine) -- "There Is No Such Thing As Time"
  • Rich
    3.1k
    The girl on the Physics Stack exchange explicitly said, well, time is not a boundary factor in this experiment. And I asked, this means, it's a timeless wave. Where else in physics would you see something analogous? I didn't get an answer, but for all I know, there might be a quotidian answer.Wayfarer

    You are absolutely on track. Bohm's book I mentioned is a good read and will confirm. His theories were rejected because of the nature of the quantum field but action at a distance is more experimentalky verified, the Chinese have demonstrated that at a minimum it acts 10,000x the speed of light. Space-time (which doesn't exist) had nothing to do with anything, not even gravity. The Relativity equations have no ontological merit.

    Do what I do, ignore the common physicist and search for the exceptional like Erik Verlinde. They are rare (as Bohm was rare) but it is worth the hunt, since you'll actually get some usable insights.
  • Rich
    3.1k
    But memory comes from a stable structure of neurons in your brain now.WISDOMfromPO-MO

    And you know this how? Had anyone ever seen your memory?
  • WISDOMfromPO-MO
    720
    And you know this how? Had anyone ever seen your memory?Rich

    They are not my words.
  • Rich
    3.1k
    A rather startling assumption in the author's part.

    As for the actual flow of time, real time, the duration of life, everyone who is alive has experienced it every day of their life.
  • andrewk
    1.1k
    So my question to you is: do you think my inference that 'what is causing the interference pattern is outside, or not a function of, space-time' is indeed 'gobbledygook'? Or do you think it's a valid inference?Wayfarer
    The problem is that by asking what 'caused' something you are moving from physics to philosophy - metaphysics, and there's quite a bit of sensitivity on physicsforums about discussions veering off into philosophy. They try - not always successfully - to maintain a clear boundary between physics and philosophy and it looks like you inadvertently crossed it. I thought the reaction was a bit harsh, especially as you, not being a regular there, would have no reason to be aware of that sensitivity.

    I wouldn't comment on the validity of your inference because I see discussion of what caused what as frustratingly ambiguous. But I can observe that increasing the time between photon emissions also increases the average distance between photons, which reduces the frequencies of interactions and hence the extent to which interaction effects distort the pure proportionality discussed in the A to the second Q. And that maybe sounds something like what you were saying.
  • Noble Dust
    2.2k
    Is this thread "pseudo-science"? @TimeLine?
  • Wayfarer
    5.3k
    I thought the reaction was a bit harsh, especially as you, not being a regular there, would have no reason to be aware of that sensitivity.andrewk

    I wasn't upset by it in the least. It was instructive. You can see, I didn't push it, but I got the distinct impression that I had crossed a line. I learned something from it.

    I can observe that increasing the time between photon emissions also increases the average distance between photons, which reduces the frequencies of interactions and hence the extent to which interaction effects distort the pure proportionality discussed in the A to the second Q. And that maybe sounds something like what you were saying.andrewk

    Right! Time is NOT of the essence.



    Mum! Mum! Those bad people are saying bad things.
  • Wayfarer
    5.3k
    Only kidding! Have a look at the threads that I linked to in the OP. As I say in both threads on physics forums, I’m not physics-literate. The question I asked might be a bit difficult to comprehend, but I think it’s basically intelligible to the lay-person, and makes a point that I think is philosophically interesting.
  • WISDOMfromPO-MO
    720
    As for the actual flow of time, real time, the duration of life, everyone who is alive has experienced it every day of their life.Rich

    If we do not need any concept of time to explain and make predictions about the physical world, why does this "flow of time" matter?

    Occam's Razor seems to apply here.
  • Noble Dust
    2.2k


    Oh I know, Wayfarer! I was joking myself. This thread has been an interesting read so far. (Y)
  • Rich
    3.1k
    If we do not need any concept of time to explain and make predictions about the physical world, why does this "flow of time" matter?

    Occam's Razor seems to apply here
    WISDOMfromPO-MO

    Duration, real time, comes into play when understanding the nature and creation of the underlying quantum information (memory). This is not scientific clock-time. Bergson warned and challenged Einstein about the attempts to elevate scientific clock time to an ontology. As common in science, politics had a lot to do was at play. You see physicists really don't mind dabbling in metaphysics when it suits their purposes.

    Robert Disalle wrote a book on the Philosophical Development of Space-Time. The Physicist and Philosopher by Canales is also worth noting.

    The upshot is that philosophers should feel quite comfortable challenging the metaphysics of physicists and scientists. Most often they have no idea how poor their metaphysics really is. I loved it when Erik Verlinde came down hard on the Big Bang which is just more metaphysics along with the Laws of Nature.
  • boundless
    33
    Hi @Wayfarer,

    I try to answer in a non-relativistic point of view.

    Short answer: the particle does not interfere with itself. In QM the interference pattern is predicted by the form of the wavefunction which can be inferred by previous observations or by theoretical assumptions.

    But I then introduced the argument that this shows that the 'wave equation' is independent of time (and therefore space, as I had understood these two to be related as 'space-time' in relativistic physics). I said, in particular, that 'what is causing the interference pattern is outside, or not a function of, space-time'.

    In my opinion here you are right. The wave equation is in fact independent of time in QM in form. However the wavefunction is of course a function of the positions (which in QM are (hermitian) operators, i.e. observables) and time (in QM it is a parameter and not an operator).However in non-relativistic QM the "squared modulus" of the wavefunction is proportional to the density probability to find a particle in a position at a given time.

    However strictly speaking the cause of the interference pattern is not "outside".In this case, in fact, the wavefunction is a sum of two terms: there is a term that describes the path through the first slit and another relative to the other path. However the wavefunction itself is not an observable. What you can observe is the probability distribution. Forgive me if I use a simplified formula:
    Let F be the wavefunction, f1 the part relative to the first path and f2 the path relative to the second.
    F = f1 + f2. The wavefunction however is complex. So the probability density distribution is:
    FF* = f1f1* + f2f2* + (f1f2* + f2f1*)
    The first two terms (f1f1* and f2f2*) are always positive. The sum of the other two (the interference) however can be negative (hence the minima)! What you observe is that the particles follow that probability distribution (which of course is related to the interference pattern: the maxima of the interference pattern are the points where FF* has a maximum and the minima where FF* has a minimum). The interference therefore is given by the wavefunction itself: if our system is not time-invariant of course the probability distribution can change during time. The interesting feature of QM however is that you do not observe F (and so f1 and f2) itself but FF*. So it does not intefer with itself, simply the interference pattern depends on the (a-priori unknown) expression of the wavefunction.

    The interaction is between the particle and the experimental apparatus. However the wavefunction has all the information about this interaction.

    Remember that in a single experiment what happens is that we observe only one "path". To observe all possible path and therefore to verify that there is a "probabilistic" law we have to do a lot of measuerements. Consider a simplified version ot the experiment. Suppose that the particle can be observed only in two points of space, P1 and P2. Prior to the experiment you cannot know where the particle will be observed. You perform the experiment and you find the particle at P1. You perform a LOT of experiments and you find that with a probability p1 you find the particle at P1. QM says that when you perform another observation you will find the particle at the position P1 with a probailty p1.


    Of course you can also predict the form of the wavefunction theoretically (i.e. from theoretical assumptions) - and in fact it is what is almost always done in physics. In fact you can include in the wavefunction all the information about physical interaction (i.e. for example the influence of a electro-magnetic field).


    Regarding the ontology there is a lot of views.
    Some adherents to the Copenaghen interpretation think that the real is what is observed, therefore until observed we cannot say that the particle "exists". (the wavefunction is not real and until observed the particle does not "exist" - Recall Einstein objections)
    Others adherents instead think that it is an epistemological issue. They think that we can only make meaningful statements on the observed. Therefore prior the observation the "ontic status" of the quantum system is unknowable. In both cases the wavefunction is a "predictive tool".
    Then there is the MWI (many-worlds). They think instead that the only existing thing is the universal wavefunction which never "collpases". All possibilities are actualized (therefore the particle goes to both slits!). The fact that we observe only a determinate path is due to a sort of an illusion.
    The original Bohmian-mechanics treated both the particles and (universal) wavefunction as real. The wavefunction guides all the particles of the universe. Again we observe the probability distribution because of our "ignorance" (we do not observe the whole evolution of the universe).
    The "new" Bohmian mechanics instead treats the wavefunction as a "law". The only reality is given by the particles.
    There is also the Relational Approach, Statistical interpretation and others.



    I suggest this link: https://plato.stanford.edu/entries/qm/

    I hope to have been of help :-#
  • boundless
    33
    A shorter (and possibly clearer answer).

    The wavefunction according to the "standard/pratical interpretation" is merely a tool for the calculations. However the wavefunction itself does NOT give you the probability distribution. So it is not an observable and not therefore a physical "thing". To a physicist what we observe is what is real.

    And what about the unobservable? Here to the pratical physicist you are already in philosophy (and some physicists actually have a sort of "aversion" to philosophy).

    In the case of the experiment therefore: the "real" is the interference pattern (which of course is observed). If you perform a single-particle experiment, of course, you do not observe the interference pattern (and therefore you infer that the "quantum particle" behaves as a particle). However if you do a "large number" of single-particle experiments you will find that the "total" interference pattern follows a wave-like law. And therefore you conclude that the "quantum particle" behaves like a wave. The wave-like nature however is apparent only when you have a statistically significant number of single-particle experiment (or if you perform a single experiment with many particles).

    Consider the case of a single experiment with a single particle. Are the other "possibilities" in some sense "real"?

    1) If you accept the Copenaghen interpretation: no. They are not real. What is real is the observed. The quantum system, when unobserved is either "unknowable" or unreal. So do the other possibilities exist? Possibly some phyicists would say that "it does not apply". The question itself is meaningless. We can only say meaningful things about what we observe (similar to positivism). Or maybe "it does not apply" for other suggests that the "unobserved quantum particle" is indeed a "reality" but we cannot describe it in any ways.

    2) If you accept the Many-Worlds yes. But you cannot observe them since the "other" paths actualize in "other worlds". In this interpretation actually the only fundamental "reality" is the universal wavefunction, which "never collapses". The fact that we observe only one occurence is due to the fact that we cannot observe "the universe".

    3) If you accept the Bohmian mechanics actually the particle follows a precise path. The other paths are so to speak "empty". The other possibilities are "real" if you accept the wavefunction as a "thing" or "unreal" if you do not accept the wavefunction as real. Also in this case the only "true" wavefunction is the universal one which "guides" all the particles in the universe. However in practice since of course we cannot observe the whole universe we have to use "conditional wavefunctions" to describe the dynamics. Are the conditional wavefunctions real? No, they are only a tool.

    There are also other interpretations. However they are all in agreement with the "observed reality". The contention is about how to interpret what we cannot observe. And in a sense speaking about what we cannot observe is "meta-physics". And in fact many physicists do not engage in philosophical discussions because of this, To them speaking about the "unobservable" is futile or "beyond our range". Therefore when someone begins to "philosophize" sometemise they grow angry!

    However the real problem is not philosophy. The problem is that sometimes people try to use QM to "prove" that nonsense like "law of attraction" & similar are "true". For this reasons many physicists have a strong aversion to philosophy and tend to react "badly" IMO to honest philosophical discussions.
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