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Insights Interview with Astrophysicist: Adam Becker - Comments

  1. Mar 31, 2018 #51
    So philosophy seems to be discussing the validity of language and scientific reasoning. For the latter, the exploration in the scientific reasoning for a science that has not had much deductive evidence seems worthwhile. To add to that statement with the change of language, the nuances of what was originally meant to what is understood today could affect the interpretation of what was the original intention. However this is just skimming the surface knowledge that I have gained.
     
  2. Mar 31, 2018 #52

    RUTA

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    You’re missing the point, quantum nonlocality and delayed choice experiments are analyzed within experimental limits using non-relativistic QM. So, obviously, Lorentz invariance does nothing to abate these mysteries. Now let’s look at some problems in physics that can actually be resolved with philosophy, i.e., the problematic initial conditions of big bang cosmology known as the low entropy problem, the horizon problem, and the flatness problem.

    These are indeed problems in physics, as evidenced by the creation of inflationary cosmology whose practitioners are physics professors at highly regarded institutions. How could mere philosophy resolve these problems? We explain that at length in chapter 3 of our book, but the short answer is that all we have to do as physicists is move from dynamical explanation per the Newtonian Schema Univese to block universe explanation per the Lagrangian Schema Universe. Those problems are created by physicists’ dynamical bias, as pointed out by ... philosophy of physics. You may not like the answer, but it is an answer from philosophy for a problem in physics. If you want to argue about it, we’ll have to take that to another thread. Let’s try to keep this thread on topic, i.e., Adam’s book.
     
  3. Apr 1, 2018 #53

    vanhees71

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    Physics is about objective reproducible quantitative observations in nature, and theoretical physics aims at a mathematical description and the derivation of the observable phenomena from as little assumptions (fundamental Laws of Nature, themselves finally always based on empirical evidence) as possible. This implies also the aim to adapt our intuitive sense for whatever ideas we have about nature. Locality and causality have a very clear and well-defined meaning in local microcausal relativistic QFT, which is the mathematical basis for the Standard Model of elementary particles. It in my opinion and open question, how to incorporate self-consistently gravitation and spacetime structure, i.e., some theory of "quantum gravity", but that's not a philosophical but purely scientific problem, which I doubt very much to be solvable by pure qualitative "philosophical" thought.
    Ordinary language is inadequate for any kind of physics in the natural sense. Already Galileo new that "the book of nature is written in terms of geometry...". This is still true today, even in a much narrower sense. Of course you have to use a modern idea of geometry, which reaches back to Klein's Erlanger program, but that's another story.
     
  4. Apr 1, 2018 #54

    vanhees71

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    Yes sure, that's the minimal interpretation, advocated by Ballentine in his famous RMP article and also in his excellent textbook. For me the probabilistic interpretation taking Born's rule as a fundamental postulate (the only logical way, because attempts to derive Born's rule from the other postulates failed so far; see Weinberg, Lectures on Quantum Mechanics, Cambridge University Press) implies that the predictions of QT can only be experimentally tested on ensembles. Formally, a state is defined as an equivalence class of preparation procedures and as such of course refers to individual systems, because in order to create ensembles the state has to refer to a preparation procedure on a single system, since each ensemble consists of many realizations of the same state (in the sense of a preparation procedure). E.g., at the LHC you have well-defined bunches of protons which in a well defined way collide at specified interaction points, where the detectors are located.
     
  5. Apr 1, 2018 #55

    vanhees71

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    By QFT I mean what's used in practice. Of course, I'm aware that QFT is not strictly defined in the mathematical sense, but renormalized perturbative QFT is well defined and obeys all the fundamental properties you expect, including locality of interactions and causality (in the sense of the linked-cluster theorem). In Hegerfeldt's paper it's not clear to me, how he defines his observables. You cannot define particles in transient states in the Heisenberg picture at all. A particle interpretation is only possible for asymptotic free states, which makes it pretty clear that relativistic particles are even less localizable as "little billard balls" than non-relativistic particles. This is all well known since Bohr and Rosenfeld and no contradiction to causality.
     
  6. Apr 1, 2018 #56

    Lord Jestocost

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    Philosophy, per se, is not confusing. It’s merely the person itself which gets confused when philosophy questions his/hers implicit assumptions.
     
  7. Apr 1, 2018 #57

    atyy

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    How come it's not ok to talk about "reality", but it is ok to talk about "Nature"?

    Is Nature different from reality?
     
  8. Apr 1, 2018 #58

    Lord Jestocost

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    Einstein believed “that the notions of physics would refer to a real external world and that these ideas would be set by things that claim a "real existence" independent of the perceiving subjects.” And then he tried to force quantum physics into the corset of his conceptions. Everybody knows how successful he was. “Physics” cannot establish that such beliefs are true, but it can establish that such beliefs are not true. But, instead of learning from Einstein’s convoluted and ultimately entirely unsuccessful attempts, some are still on the quest to find some good elements of “objective reality” in quantum theory. And the “interpretative game” goes on. It’s not the word "reality" that has almost lost its usability, it’s the concept of a physical reality that has lost all its usability.
     
  9. Apr 1, 2018 #59
    atyy's comment,
    is perhaps too much a cute fussing about words, but I'll further note that there are no “objective reproducible quantitative observations in nature” insofar as events never repeat perfectly. Of course pragmatically a given experimenter makes their choice of what is close enough (perhaps quantitatively, a formal choice of a distance between events, but even in the most meticulous experiments there are also judgement calls), there are "good" experimenters who serve as exemplars of best practice, and there are social conventions that have been honed over centuries that make intersubjective seem objective to those who have been trained in those social conventions, but there is a gap. Research is arguably about getting "out of the box" —or, for some, the straightjacket— that we find ourselves trained into, and creating a new and beautiful box for students to have to get out of in their turn. All of us have some groups of outsiders, people who have been trained into different social conventions than those we have been trained into, to whom we pay some attention. We can and should make our own choices, and perhaps it's OK even to disdain some other groups, but, I suggest, philosophers of physics are too diverse a group, at least as I find them, for physicists to dismiss all of them.
    I'll also add that there's no such thing as “pure qualitative "philosophical" thought”, except as a straw man. Most of the philosophers I pay attention to engage in quantitative mathematics of one kind or another.
     
  10. Apr 1, 2018 #60

    Lord Jestocost

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    Again, one of Einstein’s fallacies, merely based on his psychological predispositions and his desire to return to the ontology of materialism.

    In his book “Chemistry, Quantum Mechanics and Reductionism: Perspectives in Theoretical Chemistry“ Hans Primas cites Fock:

    The deeper reason for the circumstance that the wave function cannot correspond to any statistical collective lies in the fact that the concept of the wave function belongs to the potentially possible (to experiments not yet performed), while the concept of the statistical collective belongs to the accomplished (to the results of experiments already carried out) (Fock 1952, 1957).”
     
  11. Apr 1, 2018 #61

    vanhees71

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    It's ok to talk about reality with physicists, but with philosophers you never know what they mean!
     
  12. Apr 1, 2018 #62

    vanhees71

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    Well, particularly due to quantum mechanics we have some things that are really reproducible exactly. E.g., any electron is precisely as any other, they are even indistinguishable in a very strict sense. Thus to the best of our knowledge each electron has precisely the same mass, magnetic moment, and charges of the standard model as any other. Of course, these quantities can be measured only with some finite accuracy, but so far even by getting this accuracy down to up to 12 significant digits (for the magnetic moment), there's no deviation from the assumption of indistinguishability. In this sense we have objective reproducible quantitative observations in nature in much better approximation than within classical physics.

    That natural sciences are not sheer convention within a science community can be seen that indepedent researchers find the same result, measuring, e.g., the properties of elementary particles.

    Mathematics is not philosophy. The mathematicians for already some time like to group mathematics into the category of "structural sciences" rather than "philosophy". Of course, mathematical physics (like axiomatic QFT) is not philosophy but an important part of physics (maybe also mathematics, but that the mathematicians have to judge). If I was a mathematical physicist I'd consider it an insult to be named a philosopher of science!
     
  13. Apr 1, 2018 #63

    vanhees71

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    It's well known, why Fock wrote quite "interesting" philosophical articles concerning QT in Soviet times! I don't know, whether it's also in the English edition of Blokhintsev's famous QM textbook, but in the (then Eastern!) German edition there was also a "philosophical appendix"...
     
  14. Apr 1, 2018 #64

    zonde

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    Scientific approach is based on assumption of realism (defined as "there is mind independent reality" or as opposite of solipsism). So the realism is common basis for any meaningful scientific discussion (this applies to positivists too). If you reject realism there can be no meaningful discussion with you about any science topic.
     
  15. Apr 1, 2018 #65

    Lord Jestocost

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    The scope of physics and its operational formalism is limited to pointer readings (the experience of what is called “observations”), which physics can study and connect to other pointer readings. There is no need for any assumption of realism or anti-realism or anything else. All these assumption belong to the realm of beliefs, personal “hypotheses” about yourself and about your experiences of “observations”.
     
  16. Apr 1, 2018 #66

    zonde

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    I'm not sure what do you mean with "pointer readings". Do you mean either:
    1) direct experience of expermentalist;
    2) any type of record from which one can learn about certain measurement result?
     
  17. Apr 1, 2018 #67
    I would use a slightly different wording but....yes, that is exactly correct.
     
  18. Apr 1, 2018 #68
    In modern experiments, it will usually mean a record in a computer, not any direct experience, microsecond by microsecond. For experimental data to be really out there, it should be in "Supplementary Material", or at least available to other physicists on application. Where things get edgy is in the instrumental details of how the experimental apparatus was constructed, including how whatever exotic materials were used were exotically processed, where apparatus was sourced, what sources of noise were shielded and corrected for, et cetera, whchi all in all should be as much as is needed to reproduce the results.
     
  19. Apr 2, 2018 #69

    zonde

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    So do the records of experimental data and setup details have mind independent existence?
     
  20. Apr 2, 2018 #70

    vanhees71

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    I'd say, if anything is free of prejudices it's a "machine read" record of experimental results. Of course, these records are of no value, if one doesn't know, how the measurement devices and DAQ (i.e., both hard and software) has been constructed. E.g., at the LHC even the best DAQ technology cannot produce "raw data", i.e., there are hardware triggers already in the detectors before anything is stored to electronic storage. These triggers are to a certain extent constructed using models. It's not so clear to me, whether one really could perhaps through away interesting signals by such cuts. Recently there was an interesting article concerning the still mute search for particles beyond the Standard Model concerning possible long-lived candidates in the Quanta Magazine:

    https://www.quantamagazine.org/how-the-hidden-higgs-could-reveal-our-universes-dark-sector-20170926/

    So one should be aware that there is indeed a subjective element in objective observations, that cannot be eliminated, namely the "arbitrary choice" of the observational apparati. I you'd say, e.g., only the direct human senses are valid, you'd miss a lot of stuff, which objectively exists: e.g., of the electromagnetic spectrum, restricting yourself what can be seen by the human eye, you'd exclude all em. waves at wavelenths outside the one octave from about 400 too 800 nm that can be seen directly by the human eye.

    Nevertheless there's some objective reality in observations (particularly those not related to direct involvement of the human senses), because they are reproducible everywhere and at any time independently from each other, given a precise enough description of what is observed in terms of possible setups for measuring the concerning quantities. That becomse, of course, the more convincing if two or more such setups are also using different technology to measure the very same observable.
     
  21. Apr 2, 2018 #71
    I'll mostly defer to vanhees71's account, comment #70. I think of triggers as a definite lossy data compression, but how the data is compressed is presumably decided by some committee, which hopefully has some minds. One could perhaps say that once an experiment has been constructed as an automated object, the data collected can be automated and be mostly independent of mind. Indeed, if human intervention is required to keep an experiment on track because of an error condition that lies outside the automation specified, one would expect that any data during the period during which human intervention was required ought to be discarded (unless, perhaps the human intervention can be formally modeled).
    I'll paste in an account I wrote last night to a correspondent, which seems to be a propos:
    One additional note, keying in to vanhees71's account, is that triggers for large experiments are usually much more elaborate (and can slip into dangerously ad-hoc territory) than just whether one electrical signal transitions from zero to non-zero.

    I think it's best not to get too hung up on the Bishop Berkeley problem. Ultimately I can't see that it helps much to be solipsist about the world. Go to the world of extreme positivism for a visit if you like, which I've found occasionally useful as a way to get out of the box, but best to come back. I've been peppering everything I've written on PF with links to my arXiv:1709.06711 (comment #30 has a more up to date version attached) because that's how I think about QM/QFT (for which sorry, I guess) and it's not yet well-known, but for this specific question, I think its mathematical derivation of a random field as a subalgebra of a free quantum field algebra more reconciles a classical perspective and a quantum field perspective than any other math I've seen in the literature (there's a parallel with the de Broglie-Bohm approach, deriving trajectory probabilities from the wave function, but there are also fundamental differences, that I keep to the mathematics of operators acting on Hilbert space as a model for signal analysis, manifest Poincaré invariance is maintained, and I keep to an operational interpretation of the math as far as possible). One significant point, however, is that the philosophy of classical probability has become significantly less settled than it used to be. I'm happy with an instrumental, construct-an-ensemble-and-compute-statistics approach, which I think is what physicists do, but philosophers have worries that I find significant about that approach, and physicists who want to construct a model for the whole observable universe obviously can't construct an ensemble (also, if we take away the background Minkowski space, constructing an ensemble becomes quite fraught, AFAICT —amongst other worries, of course).
     
  22. Apr 2, 2018 #72

    Lord Jestocost

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    You have to find an answer for yourself to such a question. To my mind, it’s beyond the scope of "Physics" to answer this question or questions like “What is real?”. You can conceive that in course of experiments photographic plates have been blackened or that cloud droplets have been formed, without the intrusion of a conscious observer, but how should "Physics" prove your idea.

    From an instrumentalist' point of view, such questions are idle ones. "In science we study the linkage of pointer readings with pointer readings." (Arthur Stanley Eddington). That’s all. The confusion begins when one tries on base of a schedule of pointer readings to draw conclusions as to the nature of “NATURE”.

    Nevertheless, "Modern physics" now indicates that one cannot arbitrarily cut “NATURE” into – so to speak – subjective or objective parts or – let’s say – into Descartes’ mind and matter. Here I follow Bohr who said: I consider those developments in physics during the last decades which have shown how problematical such concepts as "objective" and "subjective" are, a great liberation of thought.
     
  23. Apr 2, 2018 #73

    AlexCaledin

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    f-knowledge-is-heading-towards-a-non-mechanical-reality-the-universe-begins-james-jeans-72-18-20.jpg
    ness-as-fundamental-i-regard-matter-as-derivative-from-consciousness-we-cannot-max-planck-259516.jpg
    ot-be-accounted-for-in-physical-terms-for-consciousness-is-absolutely-erwin-schrodinger-42-81-39.jpg
     
    Last edited: Apr 2, 2018
  24. Apr 2, 2018 #74

    RUTA

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    I just finished Part I of Adam's book. Did you read it? It speaks precisely against this attitude.
     
  25. Apr 2, 2018 #75

    zonde

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    Sure
    Why should physics prove anything?
    Science requires two things to do it. First, you have to have creative thinking to come up with possible explanations of phenomena. And second, you have to have critical thinking to throw away useless explanations.
    "Great liberation of thought" is good for creative thinking, but if you loose the critical thinking part as a result of this liberation ... well, it's just not going to work.
     
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