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Limitations of Physics?

  1. Aug 23, 2010 #1
    During an interview I once had to write an essay about the aims of education and whether it allows us to pursue 'the truth'. It included the following passage:

    In physics, the more we probe the nature of matter, the more it appears that mind and matter are one, in the sense that the entities we are forced to invent and describe are more mathematical abstraction than physical reality. Complemented by empirical methodologies as it is, theoretical quantum physics is subject to the limitations of the scientific method and in my opinion the search for the chimerical Theory of Everything is thus doomed to failure.

    I would appreciate any feedback on my 'naive' ideas about physics.
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  3. Aug 23, 2010 #2
    I'm not sure how you can make such a bold statement of a "theory of everything" is bound to fail on the assertion of lack of Scientific Method and Mathematical Abstractions. Especially since mathematical abstractions are the nature of reality. And what chimera exists in reason? A Theory of Everything is the extrapolation of knowledge and logic following the actions of predecessors (Electroweak, Electromagnetism, Space-time), a testament to reality not illusion.
  4. Aug 24, 2010 #3


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    Let me comment on a few snatches:

    I don't think that neither within physics nor within mathematics we are even touching the problem of mind. It's like driving a car: the robot mounting certain pieces of a car does not know anything regarding traffic jams.

    It is true that we have to invent a lot of abstract entities; nevertheless some of these entities turned out to be physically real (antiparticles, neutrinos, quarks, entangled quanta, ...) Compare it with ordinary language: I guess we agree what we mean by "red" or "redness", but I think we should also agree that both "red" and "redness" are abstractions. The problem is not that we do not understand the abstract entities in physics (we do understand quite well and we can distinguish between pure abstract entities and physical reality); the problem could very well be that we erroneously believe in our understanding of abstract entities like "redness". The difference is not that "redness" is easier to understand than "entanglement", but that we are familiar with the concept redness in everyday life w/o ever thinking about its true nature.

    It is true that theoretical quantum physics is subject to the limitations of the scientific method. It is also true that scientists know about the limitations and are even able to derive physical predictions based on some limitations. Quantums physics tells us a lot about concepts which are not realized in nature; Bells theorem for example tells us what is not realized in certain quantum objects and how one can derive predictions from these limitations which are testable by experiment!

    Your last statement that the search for the chimerical Theory of Everything is thus doomed to failure seems to be at odds with the rules of this forum and with good scientific practice. What does chimerical mean (it has different meanings)? What do you think is a theory of everything? What shall it provide? How shall it look like? Do you know about a candidate for such a theory and why it is doomed to fail?
    Last edited: Aug 24, 2010
  5. Aug 24, 2010 #4
    Yes, and as an example, no physical theory explains (or at least tries to explain) a very special role of the moment called 'NOW'. On the contrary, current physics denies any special role of NOW assuming Block Time. Looks like some physical things, like NOW, should be waiting for theory of consciousness to be explained.
  6. Aug 24, 2010 #5


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    The natural conclusion is that any physical theory of everything is a theory of "everything except mind" :-)

    Honestly: of course a physical theory of everything will have certain limitations we are not always aware of. Let's assume we are able to derive the standard model (symmetries, particle content, free parameters like masses and coupling constants) plus gravity (and cc) from string theory and let's assume that our universe is somehow singled out by a new selection principle within the landscape (e.g. some kind of evolutionary mechanism based on microscopic mechanism in string theory; just like ordinary evolution is somehow based on the chemistry of DNA + "survival of the fittest"). This would be a fantastic breakthrough and nearly everybody would agree that the ToE has eventually been identified.

    Nevertheless this theory would not answer the question why our universe is described by string theory (instead of number theory, for example). In addition this theory would not explain concepts or entities like "string", "red", "mind", "god", "love", "evil".
  7. Aug 24, 2010 #6
    But at least TOE should explain the observed values of the parameters of the Standard Model. It is hard to believe that these dimensionless numbers (even there are some relationships, like Koide formula) have no degrees of freedom. So TOE (as sterile set of equations) will be not the last step - we will need to draw the exact shape of the island of consciousness-friendly universes in the space of degrees of freedom of TOE. Are we in the center of that island? Are there any other separated islands? I would give my right hand to get an answer.
  8. Aug 24, 2010 #7


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    Your example is not ambitious enough!

    An apple is an abstract entity. And I don't mean some notion of "appleness" -- I mean that when I look at a table and assert there is an apple upon it, I am invoking an abstract concept to organize and interpret the visual data gathered by my eyes.
  9. Aug 24, 2010 #8


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    @Hurkyl: yes, you right. The whole discussion goes back to Platon and Aristoleles (or even to the pre-socratic philosophers like Thales, Heraklit, Parmenides, ...). The ancient greeks called it "metaphysics" which means "beyond physics".

    This "meta" is what I wanted to stress: the discussion regarding "mind" and "nature of a ToE" is (at least partially) metaphysics. But this is not a problem as long as we are aware of the fact that it is metaphysics and as long as we are able to talk about intrinsic limitations of physics.

    One could argue that I am closing my eyes (or like Feynman said: "shut up and calculate"). But this is not true. I think it's more about the expectation what can be achieved within physics and what cannot be achieved. If an engineer working in the automotive industry fails to construct a perfect vehicle which is able to explain the theory "of all vehicles" (and which can swim and fly) that does not automatically mean that the automotive industry has a problem :-)
  10. Aug 24, 2010 #9

    haha... as long as those abstract wave-like forms taste good and juicy, i'll accept them to be approximations of apples.
  11. Aug 24, 2010 #10


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    This reminds me of a lecture with a very respectable physicist. Suddenly one of the more "philosophical" spectators asked: "I have the strong impression that the REAL cause is mathematics... Mathematics determines what is happening in the world... WHERE is this mathematics in three-dimensional space!?"

    And the respectable physicist (now with long face) answered: "Well... I don’t have a clear opinion on that..." :smile:

    I see two options:
    • TOEEM - Theory of Everything except Mind
    • TOEEM - Theory of Everything except Mathematics
    Last edited: Aug 24, 2010
  12. Aug 25, 2010 #11


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    No, not only "except mind"; there are several other entities to be excluded (I listed a couple of them); even "redness" - which is somehow related to "mind" - cannot be explained; "rednes"s is something else but a certain wavelength.

    Of course a ToE is based on mathematical axioms and cannot explain (but has to use) mathematics.
  13. Aug 25, 2010 #12

    If I understand your post correctly, you are saying that the physics community is struggling to develop a consistent theory of matter because of:
    (1) its propensity for inventing mathematical theories that are devoid of physical reality;
    (2) dysfunction in the system developed by the community for conducting research.

    Why is the community failing to deliver? Here are some possibilities that occur to me:

    (a) The next theoretical advance doesn't have to be a hard thing. In principle, there is little preventing anyone in the community from discovering it. But debates open up, conclusions are formed, the work is declared "done", the community moves on, in a herdlike fashion. So any issue that was not treated comprehensively in the past is unlikely to be done so again within the community.

    (b) What is it that motivates a person to become a professional physicist? Love of mathematics? Thirst for knowledge? Or the all-too-human lust for status and security? (I have tenure! I'll never have to endure insults again! My retirement is assured!)

    (c) Pressure to conform to doctrine, and fear of being outcast from the community. (Crank! Heretic! It's the factories for you!)

    (d) Pressure to publish means researchers have no time to investigate the larger, more time-consuming problems. The library shelves fill up, and in turn, workers must spend more time keeping up with all the literature.

    (e) A superficial expertise, gained from reading work done by others, rather than doing the work oneself. Knowledge gained through trial and error is precious, although it is inevitably more time-consuming, and hard to justify.

    (f) Separation from society. Who challenges the community? No-one else speaks the language, no-one else has the "expertise". The community is safe from criticism. This is the same false paradise that is enjoyed by the bully. If physicists aimed to serve society, rather than look down on society, and if they strove to address the scientific questions society has, in a language that society can understand, then physics would be in a much healthier place. This may be a hard one for a member of the community to understand.

    Actually I love theoretical physics, but I am enfuriated by the mess that is presently being served up by the physics community and being called theory. I am waiting for change to come, like many others, but I am not expecting the change to come from within the community. The community has demonstrated amply that it is interested in serving little but itself. If the community doesn't clean up its act soon, it risks becoming yet another irrelevant institution, which started with promising beginnings but has lost its way.

    "We demand some more. Nature is a whore."
  14. Aug 25, 2010 #13


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    How do you come to this conclusion? To which specific "community" and to which specific "theories" are you referring to? It seems that you have a rather limited scope, that you are disappointed with some singular aspect of theoretical physics and that you now generalize this disproportionately or inadequately.
  15. Aug 26, 2010 #14

    I am talking about the worldwide "community" of professional physicists, engaged in the pursuit of a unified "theory" of quantum theory and general relativity. I hope this is a clear enough definition.

    I am expressing concern about the speculative turn that fundamental physics research has taken in the last few decades. It seems that the community has run out of good ideas to pursue. There have been fewer genuine discoveries made in the last few decades than in any time since newton. This is somewhat embarrassing, given the number of professional physicists on the planet at the moment.

    Naturally the nature of mind is an important topic. However I think theory needs to progress one step at a time, and at the moment the most pressing problems are the need to tidy up quantum field theory, unify the forces, and develop a more consistent cosmological model. Once this is done, the answers to other bigger questions may become clearer.
  16. Aug 26, 2010 #15


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    Your definition is clear.
    The observation regarding a "speculative turn" is somehow correct.
    But the reason is imho due to the fact that we have seen a paradigm shift in the last ~30 years = since the SM except for the Higgs has been "verified".

    The paradigm shift is that all new ideas (candidates for physical theories beyond the standard model) lack phenomenological or experimental support by construction. A new theory (strings, NGC, LQG, ...) is always based on two basic principles:
    1) it must reproduce known physics => no new results for experimentally accessable domain
    2) it completes SM+gravity beyond the accessible domain => new results are not accessable

    So you cannot blame professional physicists for constructing a theory which can be verifyied only in a domain where it is (strictly speaking) not needed, which cannot be falsified in this domain (as it is constructed in such a way that it reproduces known results), and which can only be falsified in a domain which is unfortunately not accessible experimentally.

    You see what my conclusion will be: the very principle of experimental input and falsification a la Popper is to be questioned. So what is required is a new principle (that's why I call it a paradigm shift) that supports and guides the construction of new theories. As long as this new principle is not available, we have to face the speculative turn for a while.

    So one should not blame the majority of physicists for working on speculative ideas, but one should try to focus (in a small community) on this paradigm shift and its consequences.
  17. Aug 26, 2010 #16
    Shots in the dark, this is what it's about. The easy part of the development of physics is over, there are no clear cut ideas to unification, no path seems promising or nearby.

    The LHC could break the deadlock by either confirming some of the existing speculations/shots-in-the-dark or through a new, not as yet observed phenomenon. Exciting times, but at the same times somewhat depressing and hopeless.
  18. Aug 26, 2010 #17


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    Are you suggesting that this paradigm has much acceptance? It sounds quite contrary in fact. I would say instead that some rather unlikely theories (such as ones that suggest variable g, cosmic strings, clashing branes, etc) get support precisely because they offer the hope of being still testable.

    So there is a prejudice (in an attempt to remain traditionally scientific - and probably also to keep the funds rolling for colliders and space telescopes) that favours the plausibly testable ideas rather than the ones that seem worthwhile for intuitive or philosophical reasons.

    Still, I agree that there is a general question of how to proceed once we hit the limits of measurement. We will be back to doing meta-physics. But it need not be metaphysics as traditionally known.

    For a start, it could indeed be a program of exhaustive mathematical search as with string theory - searching for deep pattern in a systematic fashion.

    It could be (allied to this) a turn towards computers and simulation. This has already created one revolution with fractals and deterministic chaos. So where instruments can't reach, simulation might (and Loll's work on CDT is an example of course).

    Personally, I think we also probably already know most of what we need to know. We just haven't packaged it all together. So this would be an argument that we have assembled many bits of the jigsaw, but also created such a confusion of other bits that we just have to filter the signal from the noise. We have been so prolific with ideas that the view is temporarily obscured.

    So I would say that I see little evidence of any widespread support for the idea that the future of physics lies in systematic metaphysics. But perhaps in private, you may be arguing, this acceptance is taking hold. And now the issue is how to spin it to the public and the funding agencies as a bold advance rather than a rueful retreat.
  19. Aug 26, 2010 #18


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    I agree that this paradigm shift is not widely accepted; it is not even recognized that there is such a paradigm shift, perhaps because we are no longer in the driver seat as we are no longer able to design instruments and experiments to verify / falsify new ideas.

    First we have to acknowledge that the situation has changed! Then we can discuss (as we do here) how to respond.

    I agree that there are some phenomenologically interesting ideas like clashing branes / ekpyrotic scenario, large extra dimensions, variable g and c etc. BUT: they are neither forced nor supported by experiment. So they are not a way out of the situation but simply an indication of this new paradigm.

    Strictly speaking theoretical physicists could relax and say "there is no single experimental result that cannot be explained by our theories; so our job is done!"; of course they know their job is not done, but not due to new experiments but due to inconsistencies, incompleteness, missing axioms and guiding principles etc. This is the new situation.

    I have the feeling that this discussion conerges somehow with the rather long thread regarding string theory we started a couple of weeks ago. But we can keep things separate. We can observe that there is this new situation and we should accept the paradigm shift. Then we can discuss if the way we respond (ST, LQG, CDT, NCG) is adequate or not (in the ST thread we do just this for ST).

    It could even be that the LHC fails to produce an indication for future research: assume for a moment that the LHC finds the Higgs, disproves SUSY within below 14 TeV and rules out large extra dimensions. All what can be deduced is that e.g. SUSY / ST may be correct but at higher energies; or that asymptotic safety + SM could be the right way to go; or that NCG could be correct. ****! Billions of dollars / Euro for the simple result that everything we (or our professors or professors of our professors) guessed, constructed and derived a quarter of a century ago is correct.

    I agree with you that - from the perspecive of ordinary theoretical physics - we are start to do metaphysics, but that - from the perspective of philosphers doing metaphysics - this is not ordinary metaphysics :-)

    If you read Heisenberg's and Weizsäcker's books you will see that they were aware of the fact that physics and meta-physics are closely related. It is due to the fact that QM and the SM are extraordinary successfull we (~ 100 years later!) are no longer aware of this! But we can't close our eyes for another 25 or 30 yeras, we can't wait for the third, forth and sixth superstring revolution, we can't wait for the next generation collider (whatever it may be and regardless what it will cost) just to observe that something has changed fundamentally.

    I do not say that all phenomenological research directions are nonsense - far from it! I only say that in parallel to ordinary physics, ST, LQG, NCG, CDT etc.we have to think about a new way, new principles, new guidelines of doing physics w/o experimental input.
  20. Aug 26, 2010 #19


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    Well, the key problem for this new era would seem to be that there are no constraints to force a convergence of views. In science, the experimental evidence becomes a sharply decisive constraint. But in metaphysics, human ingenuity can probably spin an endless number of equally plausible scenarios. And there would be nothing to force people to prefer one over another.

    So as a society, the more we spent on an army of post-doc meta-physicians, the more confused noise we might generate. We might feel we are making a bad situation worse - and this is what some may be feeling right now about theoretical physics.

    Therefore the field might have to be structured differently. At the moment, a proliferation of views is tolerated/funded because in science, a single good experiment will cut them all down. As is hoped for with the LHC. But a big science project in meta-physics would have to apply its own discipline, its own constraints, on free speculation. What might that look like?
  21. Aug 26, 2010 #20


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    What you describe is meta-physics as known from philosophy, driven mostly by categories of thinking deeply rooted in the nature human mind. What I have in mind is meta-physics driven by physical and/or mathematical/logical principles, but not necessarily experimentally dominated.

    Your last question "what might that look like?" is the most important question in that context; to be honest: I don't know the answer.

    But remember we have Fra here whi is interested in "inference of physical laws"; I have never really understood how this could help, but it seems to be an interesting idea.
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