Why did they ignore Bohr?

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apeiron
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One of the curiosities of 20th century physics was that the complementarity principle was central to the QM revolution, yet physics only took heed of uncertainty. Why?

Kote would certainly have an opinion. But here are some relevant snippets to remind others.

Niels Bohr on the importance and universality of complementarity or conjugate pairs....

One of his favorite maxims was that there are two types of truths: trivial truths whose opposites are plainly absurd, and profound truths which can be recognized by the fact that the opposite is also a profound truth.

[So it was not just about QM but a general philosophical fact - profound truths come in opposing pairs.]

We can think of electrons as both a particle or a wave or stream of particles depending on the situation. An object being a particle AND a wave is seemingly mutually exclusive and not possible. But an electron, in some sense, is both at once.

A profound aspect of complementarity is that it not only applies to measurability or knowability of some property of a physical entity, but more importantly it applies to the limitations of that physical entity’s very manifestation of the property in the physical world. All properties of physical entities exist only in pairs, which Bohr described as complementary or conjugate pairs.
http://en.wikipedia.org/wiki/Complementarity_(physics [Broken])

[The familiar statement of particle~wave and location~momentum duality.]

An electron can manifest a greater and greater accuracy of its position only in even trade for a complementary loss in accuracy of manifesting its momentum. This means that there is a limitation on the precision with which an electron can possess (i.e., manifest) position, since an infinitely precise position would dictate that its manifested momentum would be infinitely imprecise, or undefined (i.e., non-manifest or not possessed), which is not possible.

[Now we can see that the dualities are not states but limits. So it is not a case of either/or when it comes to a question like is it looking like a wave or a particle? Instead it is about the separation towards limits, in which an electron becomes increasingly particle-like as it becomes increasingly less wave-like.]

Both behaviors can be observed at the same time, but each only as lesser manifestations of their full behavior (as determined by the duality relation). This superposition of complementary behaviors exists whenever there is partial "which slit" information....
...a stronger manifestation of the particle nature leads to a weaker manifestation of the wave nature and vice versa.

[Again, what is fundamental is not a binary division that just exist, but instead the separation of a particle's potential in one or other possible direction.]

The group surrounding Bohr soon came to perceive complementarity and uncertainty as so closely intertwined that in 1928 Heisenberg gave Bohr's concept precedence over his own....In the larger physics community, however, the uncertainty principle became inseparable from any presentation of quantum mechanics, while complementarity figured little in the teaching of the new physics. It tended to be regarded as overly philosophical, vague, and irrelevant.

In recompense, complementarity took on a life beyond physics. Bohr sought to generalize its application, first to psychology, then to biology, and ultimately beyond the scope of natural science. Although he did not complete the book on the topic that he had hoped to write, Bohr conceived complementarity as a general epistemological argument of great import for humanity.
http://science.jrank.org/pages/48960/complementarity-uncertainty.html

[Again the social perspective. Bohr thought he was on to something fundamental. But the physics community didn't want to go there.]
 
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  • #2
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Kote would certainly have an opinion. But here are some relevant snippets to remind others.

Okay, you caught me; I studied Bohr for a little while :tongue:. Here are some more quotes you may find interesting. They are about all I came across when it comes to Bohr extending complementarity though (I think. I didn't record much from his Essays on Atomic Physics and Human Knowledge). I'm not familiar with any program he had to extend complementarity (not saying it didn't happen), but he certainly thought it was pretty important and had some wide applications. Bohr in Atomic Theory and the Description of Nature (1934, p96):
A close connection exists between the failure of our forms of perception, which is founded on the impossibility of a strict separation of phenomena and means of observation, and the general limits of man’s capacity to create concepts, which have their roots in our differentiation between subject and object.

...

For describing our mental activity, we require, on one hand, an objectively given content to be placed in opposition to a perceiving subject, while, on the other hand, as is already implied in such an assertion, no sharp separation between object and subject can be maintained, since the perceiving subject also belongs to our mental content. From these circumstances follows not only the relative meaning of every concept, or rather every word, the meaning depending upon our arbitrary choice of view point, but also that we must, in general, be prepared to accept the fact that a complete elucidation of one and the same object may require diverse points of view which defy a unique description.

I don't have the full quote handy for this next one... but here's me quoting Bohr (on qualia?) :wink::
In discussing the principle of complementarity, Bohr later draws an analogy between taking a physical quantum measurement and focusing one’s mind on an aspect of a mental image. Just as “the tinge of psychological experiences” changes as we focus our attention on their different elements, he says, so do the certainty and character of quantum properties change as we redirect our focus (ATDN 100). He also finds visualizability and complementarity in aspects of free will, writing,

"When considering the contrast between the feeling of free will, which governs the psychic life, and the apparently uninterrupted causal chain of the accompanying physiological processes, the thought has, indeed, not eluded philosophers that we may be concerned here with an unvisualizable relation of complementarity. (ATDN 96)"

And another brief bit on free will...
We are here so far removed from a causal description that an atom in a stationary state may in general even be said to possess a free choice between various possible transitions to other stationary states. (ATDN 106)”
 
  • #3
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Now we can see that the dualities are not states but limits. So it is not a case of either/or when it comes to a question like is it looking like a wave or a particle? Instead it is about the separation towards limits, in which an electron becomes increasingly particle-like as it becomes increasingly less wave-like.
I think Bohr probably actually was an either-or guy. The type of measurement you take determines which property you get, and when you actually take a measurement there's nothing quantum, uncertain, or indeterminate about it. Bohr (showing his Kantian side):
It lies in the nature of physical observation, nevertheless, that all experience must ultimately be expressed in terms of classical concepts, neglecting the quantum of action (ATDN 94).
Wave/particle duality was a misleading representation of Bohr's views though, and he himself abandoned its use. Waves and particles are classical things with persistence, intrinsic objective properties, and certain causal implications, none of which Bohr fundamentally believed in. From http://plato.stanford.edu/entries/qm-copenhagen/#4 (worth reading):
So within less than ten years after his Como lecture Bohr tacitly abandoned “wave-particle complementarity” in favor of the exclusivity of “kinematic-dynamic complementarity” (Held 1994).
To respond to your original question, Bohr himself stopped using the term "complementarity," for similar reasons to why he gave up the wave-particle pair. From the same section by Jan Faye on SEP:
Furthermore, Bohr no longer mentioned descriptions as being complementary, but rather phenomena or information. He introduced the definition of a “phenomenon” as requiring a complete description of the entire experimental arrangement, and he took a phenomenon to be a measurement of the values of either kinematic or dynamic properties.
But at the same time, I think one could make a case for Bohr being a modeler. What sets Bohr apart in my mind is his denial of intrinsic objective properties in real objects. For Bohr, real objects only exist in the context of their interactions with other things, and they have no context-independent, persistent properties. Momentum is not a persistent property of an electron. It is a property that manifests itself for the duration of an electron's collision with another object.

One would expect Bohr to be an instrumentalist. He denied that we should be looking for properties that would meet Einstein's (well, EPR's) criterion for reality. He didn't believe that objects had any properties (or existence) in a metaphorical vacuum. (I find it helpful to consider Bohr with a dose of Berkeley's "common-sense" arguments for rejecting materialism :smile:.) Bohr, however, was not an instrumentalist. He was a strong realist. He was able to hold this view by realizing (correctly? incorrectly?) that physics had never been about any more than the model, and we had always been calling the model reality. Furthermore, he believed it was impossible to do any better. So either we can call the model reality, as we do naively, or we can never begin to know the first thing about what basic reality is (the second option is what Bohm actually settled on). So our model doesn't allow us to visualize causality like we wanted to - big deal - the experiments are telling us that this is an impossible goal, so let's let it go. Bohr again:
We meet here in a new light the old truth that in our description of nature the purpose is not to disclose the real essence of the phenomena but only to track down, so far as it is possible, relations between the manifold and aspects of our experience (ATDN 18)

I think Bohr had some troubles in that he changed his own terminology and spoke liberally about subjectivity and observation. To him, however, these had nothing to do with humans or minds, so there was no confusion. Also, he spoke in very realistic terms while maintaining that real objects had no intrinsic objective properties and that there was no "view from nowhere." These two views are difficult to reconcile, and Bohr didn't emphasize their reconciliation. It's also hard to understand how a "no view from nowhere" stance could not require one to fall back on minds as subjective observers. And finally, the "no view from nowhere" stance is opposed to the entire implicit goal of physics, which is to describe the world from the objective point of view.

Of course this is all just the view that I have come to on Bohr. Someone please correct me :smile:.
 
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  • #4
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I do not know the history of why Bohr has been ignored but it might be useful to point out that the uncertainty principal is not a philosphical precept but rather a feature of quantum mechanics. Mathematically is a feature of the Fourier transform. Bohr's theory seems to me, and correct me when I err, to be a conceptual interpretation of theory rather than a feature of it.

The Uncertainty Principal applies in all of quantum mechanics not only for position and momentum.

To my naive mind, the philosophers have tried to objectify QM in terms of common everyday/classical ideas and fail to realize that QM objects such a electrons are neither waves or particles but something different. The wave nature comes from the the interference of wave functions, the particle nature from the calculation of discrete measurement events, a process that is still not understood. However, the wave function is not really a wave in the classical sense. It is a solution of a complex heat equation not of a wave equation. The wave function evolves not as a wave would but as a Markov like process where amplitudes replace probabilities. In fact, it is simple to derive the Shroedinger equation from such a Markov like process just as you can derive the heat equation from a continuous Brownian motion. For me, it helps to think of the Markov process as the actual quantum mechanical phenomenon and all else is a epiphenomenon of it (e.g. wave interference) -- except for measurement which is still not understood. A good example for me is the evolution of spin states according to the Shroedinger equation. I do not think of this in terms of wave particle duality
 
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I do not know the history of why Bohr has been ignored but it might be useful to point out that the uncertainty principal is not a philosphical precept but rather a feature of quantum mechanics. Mathematically is a feature of the Fourier transform. Bohr's theory seems to me, and correct me when I err, to be a conceptual interpretation of theory rather than a feature of it.

We are talking about the conceptual parts of the theory, but there's no separating the mathematical portions from their interpretation. A physical theory without a conceptual basis is just pure meaningless math. The math itself never tells you which measurements to plug in for each variable - that's where the conceptual interpretation comes in. That's also why physics and philosophy are so entwined.

For a theory to be correct there can't be any contradictions in either its math or its conceptual framework. For philosophers, it's not good enough to say that measurement is not yet understood. Measurement is the link between the conceptual and mathematical aspects of theories. It's how you find physical meaning for your variables. If you don't understand measurement, you can't show that your theory is self-consistent and lacks contradictions. Philosophers will leave the experiments and the development of more and more complete and accurate theories to the physicists. We'll help out, however, when a dose of logical consistency and conceptual analysis is required :smile:.

I'm sure there are plenty of bad philosophers who don't understand the physics, but there are also a lot of good ones who do. Just as Bohr, Heisenberg, and Bohm wrote books on philosophy, contemporary philosophers publish in leading physics journals. http://www.princeton.edu/~hhalvors/" [Broken] is one of my favorite examples (yes, he taught Princeton's graduate course, "Foundations of Algebraic Quantum Theory"). No philosophers take anyone seriously if they get the physics wrong.

See http://en.wikipedia.org/wiki/Duhem–Quine_thesis and http://en.wikipedia.org/wiki/Confirmation_holism.
 
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We are talking about the conceptual parts of the theory, but there's no separating the mathematical portions from their interpretation. A physical theory without a conceptual basis is just pure meaningless math. The math itself never tells you which measurements to plug in for each variable - that's where the conceptual interpretation comes in. That's also why physics and philosophy are so entwined.

For a theory to be correct there can't be any contradictions in either its math or its conceptual framework. For philosophers, it's not good enough to say that measurement is not yet understood. Measurement is the link between the conceptual and mathematical aspects of theories. It's how you find physical meaning for your variables. If you don't understand measurement, you can't show that your theory is self-consistent and lacks contradictions. Philosophers will leave the experiments and the development of more and more complete and accurate theories to the physicists. We'll help out, however, when a dose of logical consistency and conceptual analysis is required :smile:.

I'm sure there are plenty of bad philosophers who don't understand the physics, but there are also a lot of good ones who do. Just as Bohr, Heisenberg, and Bohm wrote books on philosophy, contemporary philosophers publish in leading physics journals. http://www.princeton.edu/~hhalvors/" [Broken] is one of my favorite examples (yes, he taught Princeton's graduate course, "Foundations of Algebraic Quantum Theory"). No philosophers take anyone seriously if they get the physics wrong.

See http://en.wikipedia.org/wiki/Duhem–Quine_thesis and http://en.wikipedia.org/wiki/Confirmation_holism.

I am not sure what your point is. The distinction that I made is correct.

Suppose I interpret quantum mechanics to be a manifestation of the unity of chi in the universe. All things are connected through energy and spirit. Would you call this a feature of the theory?

BTW the measurement problem is an active area of scientific research - Serious physicists - not philosophers - are investigating it. Currently there are competing theories of measurement all of which are considered unsatisfactory. A layman's treatise on this is Quantum Mechanics and experience by David Albert - a philosopher! My first exposrue to it was in a QM course given by Brian Greene. He did not discuss measurement philosophically but as a problem that needed a theoretical physics framework.
 
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  • #7
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I am not sure what your point is. The distinction that I made is correct.

Suppose I interpret quantum mechanics to be a manifestation of the unity of chi in the universe. All things are connected through energy and spirit. Would you call this a feature of the theory?

Of course it would be a feature of the theory. It would also invalidate your theory, unless you could somehow reinterpret reality in terms of your concept of chi - in which case it would just be silly and not philosophically or scientifically satisfying.

There are no theories without interpretations, only meaningless math.

BTW the measurement problem is an active area of scientific research - Serious physicists - not philosophers - are investigating it.

The physicists working on the measurement problem are working with the purely conceptual aspects of quantum mechanics. The mathematical framework for nonrelativistic QM has been established for decades. It is also just incorrect that philosophers don't work on the issue professionally.

I will also point out that neither Bohr nor Bohm, nor most of the other physicists involved in the development of QM, saw any measurement problem. The measurement problem is a conceptual issue with collapse interpretations of QM. Bohr's interpretation is no-collapse, so there is no problem.

See http://plato.stanford.edu/entries/qt-measurement/ for an academic philosophical overview of the topic.
 
  • #8
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Of course it would be a feature of the theory. It would also invalidate your theory, unless you could somehow reinterpret reality in terms of your concept of chi - in which case it would just be silly and not philosophically or scientifically satisfying.

There are no theories without interpretations, only meaningless math.



The physicists working on the measurement problem are working with the purely conceptual aspects of quantum mechanics. The mathematical framework for nonrelativistic QM has been established for decades. It is also just incorrect that philosophers don't work on the issue professionally.

I will also point out that neither Bohr nor Bohm, nor most of the other physicists involved in the development of QM, saw any measurement problem. The measurement problem is a conceptual issue with collapse interpretations of QM. Bohr's interpretation is no-collapse, so there is no problem.

See http://plato.stanford.edu/entries/qt-measurement/ for the academic philosophical overview of the topic.

thanks for the references. Show me in the postulates of quantum mechanics how you derive wave particle duality. Lets do this with spin 1/2.

If you agree that some philosophical interpretations are less useful than others then you should admit in theory that the uncertainty principal which is language that describes a structural feature of QM may be different qualitatively than an interpetation which does not.

I certainly was not saying that physics is just math. My point was that the uncertainty principal can be derived from quantum mechanics. Wave particle duality can not.

I do not see why Bohm's theory of QM is purely conceptual - whatever that really means. Perhaps you could tell me. Bohm's theory is seen by some as a path to solving the measurement problem.

You have misread and I think trivialized my points.
 
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  • #9
apeiron
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I don't have the full quote handy for this next one... but here's me quoting Bohr (on qualia?) :wink::
And another brief bit on free will...

But this is the subjective~objective duality of epistemology~ontology, or the modelling relation. It is about the way minds know worlds. Definitely a dichotomy, but not the more challenging one I meant.

What I was citing was ontological complementarity. What is actually case "out there" when it comes to objects like electrons.

And Bohr's shock at first being forced towards a principle - that objects like electrons and photons are particles~waves. Then realising this was deeply logical - in the old dialogic, yin-yang, thesis~antithesis way. And then...well the physics community seemed not to get the importance of this?

Instead, the fact was accepted - enshrined as an uncertainty principle and an apparatus of bra-kets, operators, hilbert spaces, etc - and the unconventional strangeness of the fact pushed aside.
 
  • #10
apeiron
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To respond to your original question, Bohr himself stopped using the term "complementarity," for similar reasons to why he gave up the wave-particle pair.

So within less than ten years after his Como lecture Bohr tacitly abandoned “wave-particle complementarity” in favor of the exclusivity of “kinematic-dynamic complementarity” (Held 1994).

Thanks. And I would entirely agree with this progression. It is a move towards a systems or process philosophy view of reality. Instead of talking about rival states or kinds of objects, he is now talking about different kinds of relationshops that weave located "objectness" within the constraints of contexts.

Note how this matches the similar progression in foundations of maths from set theory (containers and their contents - static existence both) to category theory (processes~structures to match Bohr's kinematic-dynamic).

I think Bohr had some troubles in that he changed his own terminology and spoke liberally about subjectivity and observation. To him, however, these had nothing to do with humans or minds, so there was no confusion.

I agree - in my limited reading of Bohr. He knew that QM focuses attention on the issue of observers. Classical physics had been able to ignore the creative process of reality by simply treating reality as a static existent object. A bunch of atoms in a void. Then QM introduced a model of the observed side of reality, and failed to deliver a model of the observation.

So again, physics was taking something to just exist (but now it was wavefunctions, uncertainty, complementary states and entangled probabilities), cutting away the relationships that make creation a process. But in doing so, QM also most clearly created the observer problem.

Bohr could see that with no epistemic cut in the model - no definition of the complementary act of observation - the finger could get pointed back in endless regress to consciousness itself. However, this is not a natural view. And if he were around today, no doubt he would favour decoherence as the right way to go in introducing "observation" back into the physical picture.

It's also hard to understand how a "no view from nowhere" stance could not require one to fall back on minds as subjective observers. And finally, the "no view from nowhere" stance is opposed to the entire implicit goal of physics, which is to describe the world from the objective point of view.

I see decoherence as the view from everywhere. The universe is a vast decohering system. It decoheres across all possible scale. It is a self-organising network of relationships. Which would make observation pretty objective - the universe is the observing system constituted by what it observes.

So Bohr would seem to be recognising first the essential process which is mind-like - all about an interaction between observers and the observed. Then he was trying to put this familiar epistemological~ontological or subjective~objective dichotomy "out there" in the universe, completing the revolution half-begun by QM.
 
  • #11
apeiron
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Bohr's theory seems to me, and correct me when I err, to be a conceptual interpretation of theory rather than a feature of it.

For me, it helps to think of the Markov process as the actual quantum mechanical phenomenon and all else is a epiphenomenon of it (e.g. wave interference)

Maybe this is indeed one reason why Bohr's insight was ignored. It does seem more a qualitative distinction than a quantitative one. To actually do quantum mechanics, the big view was broken down into simpler devices. So you can make practical calculations which treat the wavefunction as a success of existing states, further removing the need to treat things as being about a continuous system formed of relationships.

Physics ignored complementarity because it wanted to move on to lower-level technical applications. And this could be done using the old classical mechanical mindset quite adequately.


The Uncertainty Principal applies in all of quantum mechanics not only for position and momentum.

But the essential point is still that uncertainty reduces to complementarity. You may start with a state of naked QM potential where anything seems possible, but when you want to reduce this what can actually emerge, you end up with "only complementaries".

And Bohr's point was that physics expected reality to reduce to "only one thing". Not always two things. And two things related in this exact, mutually-defined, or complementary way.

And hey, it was what philosophers had always found. Fundamental concepts are also aways dual. So plainly something was going on.

Here is Bohr right in the centre of the most important scientific revolution of all time. He comes to a realisation. His peers all agree he is onto something key. And then physics just shrugs it shoulders, encodes the duality as a necessary quantitative correction and ignores any suggestion that a conceptual correction might also be in order.

Why has physics been so resistant to the idea? The fact that modern physics is largely about practical technical application - shut up and calculate - certainly seems a large part of the story.

It is not as if they proved the logic of the concept wrong?
 
  • #12
Wilczek mentions Bohr and profound truths and mistakes in his book. Anyone can make a mistake. But only a genius can make a profound mistake. He was referring to Newton. Kind of like what Picasso said about art, art is a lie that makes us realize truth.

I always liked this Bohr quote:

"Everything we call real is made of things that cannot be regarded as real."
 
  • #13
apeiron
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"Everything we call real is made of things that cannot be regarded as real."

Exactly. This is the paradox at the heart of human modelling. And the problem is that the modelled then becomes "the real" for the vast majority.

Newton's "profound mistake" I presume you mean was the idea of action at a distance. All his contemporaries, were trying to model gravity as a process. Descartes, for example, wanted the actions transmitted via the swirling motions of tiny jostling atoms, a motile corpuscular aether.

But Newton said no, I take the limit as a being an actual state and throw away any idea of a process that might get us there. His letters to Hooke revealed his doubts about the reality of this. But it was the bold act of reduction - from what seemed real to what was clearly unreal - that proved to be the most efficient approach to modelling the situation.
 
  • #14
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Maybe this is indeed one reason why Bohr's insight was ignored. It does seem more a qualitative distinction than a quantitative one. To actually do quantum mechanics, the big view was broken down into simpler devices. So you can make practical calculations which treat the wavefunction as a success of existing states, further removing the need to treat things as being about a continuous system formed of relationships.

Physics ignored complementarity because it wanted to move on to lower-level technical applications. And this could be done using the old classical mechanical mindset quite adequately.




But the essential point is still that uncertainty reduces to complementarity. You may start with a state of naked QM potential where anything seems possible, but when you want to reduce this what can actually emerge, you end up with "only complementaries".

And Bohr's point was that physics expected reality to reduce to "only one thing". Not always two things. And two things related in this exact, mutually-defined, or complementary way.

And hey, it was what philosophers had always found. Fundamental concepts are also aways dual. So plainly something was going on.

Here is Bohr right in the centre of the most important scientific revolution of all time. He comes to a realisation. His peers all agree he is onto something key. And then physics just shrugs it shoulders, encodes the duality as a necessary quantitative correction and ignores any suggestion that a conceptual correction might also be in order.

Why has physics been so resistant to the idea? The fact that modern physics is largely about practical technical application - shut up and calculate - certainly seems a large part of the story.

It is not as if they proved the logic of the concept wrong?

I still don't see what the duality really is. Maybe this is what I need to understand. The ideas of particle and wave both fail in quantum mechanics and it seems to me that we are using these old pictures to explain something different. The mathematical models are also entirely different.

I think this is why in QM the idea of force is de-emphasized and ultimately replaced. Energy takes the high seat.

But you have in several threads postulated the idea of necessary duality. Perhaps you could elaborate on it and explain why you think it is important.

The measurement problem seems on the surface to fit your idea of necessary duality since you have the duality of an indefinite continuous thing - a wave function - that becomes definite and discrete at the moment of measurement.
 
  • #15
apeiron
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But you have in several threads postulated the idea of necessary duality. Perhaps you could elaborate on it and explain why you think it is important.

My actual model of duality is now based on symmetry and symmetry-breaking. So we start with the unbroken, a pure symmetry potential of some kind, and then we break it as far as it can be broken. Thus we end up with an asymmetry. And in fact a scale asymmetry - the local~global symmetry breaking that is modelled in hierarchy theory and systems science.

So I come to this postulate from another branch of science - the modelling of complexity. Yet now I am interested in how it has cropped up also in fundamental physics - the modelling of simplicity. And why it has then been ignored when it does crop up. Bohr being a good example (though we have string dualities as a current issue of course).

Discussing Bohr, note that Kote has pointed out that particle~wave is the "beginner's" framing of the duality. As I said, it is still talking in terms of objective states rather than active processes. Kinematic-dynamic complementarity moves us towards the active view.

And then there Bohr's point about profound truths being recognized by the fact that the opposite is also a profound truth. This is the history of Greek philosophy in a nutshell.

If I say chance, you say necessity. If I say stasis, you say flux. If I say discrete, you say continuous. If I say substance, you say form.

And the reason is that to be able to go in some clear and definite direction, you have to by logical definition, be clearly and definitely leaving some place behind. Every crisp event must have a crisp context.

If I am paddling a boat in a fog, am I really going anywhere or standing still? I can't actually say. But if the fog lifts and I can see I am paddling out to sea, then there is a context which makes my motion, or lack of it, meaningful.

So this is the deep reason for dualities. You cannot have one definite direction without have the complementarity that actually makes it "definite". Every action needs a reaction to be an action (and reactions need actions to be a reaction).

Name a key insight in physics that does not hinge on such dichotomies? Newton's third law is the one that makes sense of the others. Einstein saw the symmetry, the duality, that lurked in gravity and acceleration. That led to GR. Particle~wave was the key that unlocked QM.

This seems to be the deep way the world works. It begins in symmetry. And when symmetry breaks, you are left with dualities. Or asymmetric dichotomies would be my own preferred technical jargon. When symmetries are completely broken, they take a particle~wave form where you have just the fundamental "twoness" or a local limit and a global limit, which makes a fundamental threeness if you include then the third thing of the hierarchical interactions of what gets split apart.

Bohr was saying QM seems to be a particular example of something already known to be much more general in philosophy. So hey guys, why not stop to consider this?

Yet are today's physicists being trained to think in these terms? Clearly not. So why not?

Maybe it's why we have become great at churning out technology - just shut up and calculate - but there seems to be a grave shortage of Einsteins, Newtons and Bohrs around these days. The very source of their discoveries is being denied.
 
  • #16
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But this is the subjective~objective duality of epistemology~ontology, or the modelling relation. It is about the way minds know worlds. Definitely a dichotomy, but not the more challenging one I meant.

What I was citing was ontological complementarity. What is actually case "out there" when it comes to objects like electrons.

I've typically interpreted complementarity as more of an epistemological than ontological view... although Bohr brings the two together very closely. From Faye (not that he's infallible):
Complementarity is first and foremost a semantic and epistemological reading of quantum mechanics that carries certain ontological implications. Bohr's view was, to phrase it in a modern philosophical jargon, that the truth conditions of sentences ascribing a certain kinematic or dynamic value to an atomic object are dependent on the apparatus involved, in such a way that these truth conditions have to include reference to the experimental setup as well as the actual outcome of the experiment. This claim is called Bohr's indefinability thesis (Murdoch 1987; Faye 1991).

Bohr could see that with no epistemic cut in the model - no definition of the complementary act of observation - the finger could get pointed back in endless regress to consciousness itself. However, this is not a natural view. And if he were around today, no doubt he would favour decoherence as the right way to go in introducing "observation" back into the physical picture.

I see decoherence as the view from everywhere. The universe is a vast decohering system. It decoheres across all possible scale. It is a self-organising network of relationships. Which would make observation pretty objective - the universe is the observing system constituted by what it observes.

I can't speculate on whether Bohr would have changed his stance to include decoherence (well, I guess I could, but not well). But I don't think the interpretation Bohr did adopt is compatible with decoherence. Bohr was big on the wave function not having any physical meaning and collapse not representing anything in reality. He had no problem with not giving a meaning to collapse and went as far as to say that QM was complete and there was no further room to explain any underlying mechanisms. The mechanism, for Bohr, was inherently incomprehensible and unvisualizable. Only the classical results of interactions were comprehensible, hence the completeness of QM in statistical form. It's also possible that I'm just not familiar enough with decoherence.

So Bohr would seem to be recognising first the essential process which is mind-like - all about an interaction between observers and the observed. Then he was trying to put this familiar epistemological~ontological or subjective~objective dichotomy "out there" in the universe, completing the revolution half-begun by QM.

When Bohr writes, he emphasizes the subjectivity of relativity theory. He doesn't seem to find any of his inspiration in mind-body duality (but who knows what he actually thought). He derives all of his "subjectivity" and relativism from special relativity's notion that the properties of velocity and length etc were meaningless unless placed in the context of a certain reference frame (experimental setup). I don't know if this disagrees with what you said, but I'm reminded of it :smile:.

The progression seems to me to be an extension out of relativity. Classical physics denies the objective intrinsicality of colors and meanings. Relativity denies the objective intrinsicality of position, velocity, size, and mass. In relativity, of course, you can often talk about inertial reference frames and rest mass etc. QM puts the nail in that coffin by saying that these properties don't just depend on reference frames but are mutually exclusive and therefore lack persistence. (Neglecting Bohm for the moment - I'll save arguments that he doesn't solve much ontologically :wink: - though philosophically I think he still solves a lot.) I think that Bohr realized this progression. I think it is a strength of his view that it restores an ontological equality to our naive conceptions of properties.
 
  • #17
apeiron
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I can't speculate on whether Bohr would have changed his stance to include decoherence (well, I guess I could, but not well). But I don't think the interpretation Bohr did adopt is compatible with decoherence. Bohr was big on the wave function not having any physical meaning and collapse not representing anything in reality. He had no problem with not giving a meaning to collapse and went as far as to say that QM was complete and there was no further room to explain any underlying mechanisms. The mechanism, for Bohr, was inherently incomprehensible and unvisualizable. Only the classical results of interactions were comprehensible, hence the completeness of QM in statistical form. It's also possible that I'm just not familiar enough with decoherence.

It was the accounts of Bohr that stressed the idea he was of the "shut up and calculate" school that put me off reading him more closely in the past. But I am now thinking that this is a case of Bohr being interpreted in ways that suit the wider physics community - history is being rewritten to normalise his dangerous views. I have come across this same thing in ancient greek philosophy - history is told by the winners after all.

I now think that Bohr had a more subtle understanding that would repay my research.

As to the episto~ontic issue, I feel Bohr would be taking the right approach if what he meant was that the wave-iness and particle-iness are not properties inherent in unseen objects but instead aspects of the questioning process - constraints exerted by the observer (whatever that may turn out to be) that shapes up the nature of the observables.

So it could be that wave or particle is just the only questions that a human mind could imagine asking of a naked QM potential. Or it could be that wave~particle are more objective in being the way that the symmetry of reality must break when any questions start getting asked.

My own belief (and it was a big surprise) is that epistemology and ontology do work the same way, they do have the same self-organising logic. So there is a reason why epistemology can seem to be ontology, even if we ought to keep them separated.

Our understanding is vague. And this symmetry state can only be broken completely by dichotomies. Reality also starts vague. And likewise, its symmetry can only be completely broken by dichotomisations.

OK, now I've introduced another good reason why Bohr was ignored. This way of understanding reality is just too self-referential and complicated for most people.

Possibly also it is to inter-disciplinary. We are talking about a generalisation that emerges from across many different fields, all divided by their own jargons and customs. So to teach dichotomies 101, you would have to draw from physics, biology, thermodynamics, greek philosophy, tao, category theory....and who has time to draw all that knowledge together, boil it down?
 
  • #18
apeiron
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The progression seems to me to be an extension out of relativity. Classical physics denies the objective intrinsicality of colors and meanings. Relativity denies the objective intrinsicality of position, velocity, size, and mass. In relativity, of course, you can often talk about inertial reference frames and rest mass etc. QM puts the nail in that coffin by saying that these properties don't just depend on reference frames but are mutually exclusive and therefore lack persistence. (Neglecting Bohm for the moment - I'll save arguments that he doesn't solve much ontologically :wink: - though philosophically I think he still solves a lot.) I think that Bohr realized this progression. I think it is a strength of his view that it restores an ontological equality to our naive conceptions of properties.

This is a good way of putting it. Nothing exists at points except what we create at points. And then we even create the points themselves!

This is what I call the systems view. Top-down global constraint restricts naked freedoms to create what we find at a systems locales. But then - and it is a big but then - what gets created at locales is then the "stuff" that can additively and collectively construct the system.

And then - another big then - it has to be the case that it is the right kind of stuff building the right kind of system, other wise the system won't have the right kind of constraints to be creating the local stuff. (Hofstadter sort of wrote about this as strange loops - http://en.wikipedia.org/wiki/Gödel,_Escher,_Bach)

But anyway this is the logic of synergy and mutuality and other modern accounts of how two things interact to form a complementary whole.

See for instance...
Synergy - http://en.wikipedia.org/wiki/Synergy
Synergetics - http://www.center-for-synergetics.de/
 
  • #19
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Yet are today's physicists being trained to think in these terms? Clearly not. So why not?

Maybe it's why we have become great at churning out technology - just shut up and calculate - but there seems to be a grave shortage of Einsteins, Newtons and Bohrs around these days. The very source of their discoveries is being denied.

Maybe we are in a culture that does not support the expensive experiments needed to test theories further. Many physicists have left for other things. As have many mathematicians. A mathematician I know who started a hedge fund said that we have a lot of Physics but we can't do the experiments to test any of it.

In my Wall Street days physicists were flocking to the trading floor. In my group I hired a guy who specialized in predicting chaos and was tired of the researcher's life and living in New Mexico.

Recently I attended a lecture on quantum computers. The researcher is part of a group at Microsoft. There are many theoretical questions that they need to answer to build this thing and they are testing their theories with real machines as well as mathematical models. He talked a lot about topological quantum field theories and Chern-Simons theories which seem to model aspects of quantum Hall fluids. I don't understand the stuff but it seems like many of the purely theoretical developments of the past half century are getting a chance to be tested.

It is also possible that Physics has become so mathematical that is has needed to take a rest and focus on mathematical frameworks for a while. This seems to have happened in the 19'th century with the development of modern mathematics prior to the physical theories that relied on it.
 
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  • #20
I wonder what his conversations with Wheeler were like on this subject. I remember reading in Wheeler's obituary:

"You can talk about people like Buddha, Jesus, Moses, Confucius, but the thing that convinced me that such people existed were the conversations with Bohr,” Dr. Wheeler said.

He thought Bohr was one of those transcendent figures.

I also thought Dyson proposed an interesting dichotomy about scientists. Says there are two kinds. Unifiers and diversifiers. The unifiers are happy to leave the world a little less complicated than they found it. Diversifiers are happy leave the world a little more complicated than they found it. Says most physicists are unifiers but gave Wheeler as an example of an exception who was a diversifier.

Dyson says the universe is built on the principle of maximum diversity.

The philosophical principle of maximum diversity, says Dyson, states "that the laws of Nature are constructed in such a way as to make the universe as interesting as possible."

The discoveries of recent decades in particle physics have led us to place great emphasis on the concept of broken symmetry. The development of the universe from its earliest beginnings is regarded as a succession of symmetry-breakings. As it emerges from the moment of creation in the Big Bang, the universe is completely symmetrical and featureless. As it cools to lower and lower temperatures, it breaks one symmetry after another, allowing more and more diversity of structure to come into existence. The phenomenon of life also fits naturally into this picture. Life too is symmetry-breaking. . . . Every time a symmetry is broken, new levels of diversity and creativity become possible.
 
  • #21
apeiron
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I also thought Dyson proposed an interesting dichotomy about scientists. Says there are two kinds. Unifiers and diversifiers. The unifiers are happy to leave the world a little less complicated than they found it. Diversifiers are happy leave the world a little more complicated than they found it. Says most physicists are unifiers but gave Wheeler as an example of an exception who was a diversifier.


Not heard that one. But it would seem to mean the same as analysis vs synthesis. Or differentiation vs integration.

Dyson says the universe is built on the principle of maximum diversity.

I think that is only true of the "middle era" of the universe. It started in great uniformity and will end in great uniformity. And anything interestingly complex, like us, appears only inbetween.

Talking about the physics of complementarities, the big bang~heat death is of course the cosmological one.

And note how energy/heat/etc is limited by the dualities of the planck scale. The hottest things can get is the planck heat. The coldest is then absolute zero.

It just goes on and on.
 
  • #22
I also thought Dyson proposed an interesting dichotomy about scientists. Says there are two kinds. Unifiers and diversifiers. The unifiers are happy to leave the world a little less complicated than they found it. Diversifiers are happy leave the world a little more complicated than they found it. Says most physicists are unifiers but gave Wheeler as an example of an exception who was a diversifier.


Not heard that one. But it would seem to mean the same as analysis vs synthesis. Or differentiation vs integration.



I think that is only true of the "middle era" of the universe. It started in great uniformity and will end in great uniformity. And anything interestingly complex, like us, appears only inbetween.

Talking about the physics of complementarities, the big bang~heat death is of course the cosmological one.

And note how energy/heat/etc is limited by the dualities of the planck scale. The hottest things can get is the planck heat. The coldest is then absolute zero.

It just goes on and on.

True. But Dyson is a futurist and thinks complexity will never end because "mind" will fill and take over the universe eventually. Or something like that.

:blushing:

Wheeler said all is mutable. If we advance far enough, we may develop the means to mute the actions of the universe that don't favor us. And replace them with ones that do.
 
  • #23
apeiron
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http://physicsworld.com/cws/article/print/33963

The Bohr paradox - May 1, 2008

The time is therefore ripe for re-evaluating Bohr and clarifying the “Bohr paradox”: why he is both revered and underappreciated?

Bohr practised physics as if he were on a quest. The grail was to fully express the quantum world in a framework of ordinary language and classical concepts.

Many physicists, finding the quest irrelevant or impossible, were satisfied with partial explanations — and Heisenberg argued that the mathematics works: that’s enough!

Bohr rejected such dodges, and rubbed physicists’ noses in what they did not understand or tried to hide. However, he did not have an answer himself — and he knew it — but had no reason to think one could not be found.

His closest approximation was the doctrine of complementarity. While this provoked debate among physicists on the “meaning” of quantum mechanics, the doctrine — and discussion — soon all but vanished.

Why? The best explanation I have heard is advanced by the physicist John H Marburger, who is currently science advisor to US President George Bush. By 1930, Marburger points out, physicists had found a perfectly adequate way of representing classical concepts within the quantum framework using Hilbert (infinite-dimensional) space. Quantum systems, he says, “live” in Hilbert space, and the concepts of position and momentum, for instance, are associated with different sets of coordinate axes that do not line up with each other, thereby resulting in the situation captured in ordinary-language terms by complementarity

“It’s a clear, logical and consistent way of framing the complementarity issue,” Marburger explained to me. “It clarifies how quantum phenomena are represented in alternative classical ‘pictures’, and it fits in beautifully with the rest of physics. The clarity of this scheme removes much of the mysticism surrounding complementarity. What happened was like a gestalt-switch, from a struggle to view microscopic nature from a classical point of view to an acceptance of the Hilbert-space picture, from which classical concepts emerged naturally. Bohr brokered that transition.”

Thus while Bohr used the notion of complementarity to say that quantum phenomena are both particles and waves — somewhat confusingly, and in ordinary-language terms — the notion of Hilbert space provided an alternate and much more precise framework in which to say that they are neither. Yet the language is abstract, and the closest outsiders can come to grasping it is Bohr’s awkward and imperfect notion.
 
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  • #24
This reminds me of another point from Wilczek's book. Where he pulls out an Einstein quote:

"Make everything as simple as possible, but not simpler."
 
  • #25
This thread still interests me and I have a few questions. Are you saying that a lot, if not all, profound truths are preceded by profound mistakes? Or that nobody could come up with a profound truth without at least being aware of the profound mistake. And maybe a profound truth can show you a profound mistake that nobody ever made yet . So it goes both ways, a profound mistake can help you discover a profound truth, but a profound truth could also help you discover a profound mistake. If you run into one, you will eventually run into the other. No matter which comes first.

And about always wanting to reduce things to one. Could this duality you speak of have implications about uniting GR with QM? That maybe they can't be united to one.
 

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