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Byron Jennings | TRIUMF | Canada

View Blog | Read Bio

Is there a place for realism in science?

In the philosophy of science, realism is used in two related ways. The first way is that the interior constructs of a model refer to something that actually exists in nature, for example the quantum mechanical wave function corresponds to a physical entity. The second way is that properties of a system exist even when they are not being measured; the ball is in the box even when no one can see it (unless it is a relative of Schrodinger’s cat). The two concepts are related since one can think of the ball’s presence or absence as part of one’s model for how balls (or cats) behave.

Despite our and even young children’s belief in the continued existence of the ball and that cats are either alive or dead, there are reasons for doubting realism. The three main ones are the history of physics, the role of canonical (unitary) transformations in classical (quantum) mechanics, and Bell’s inequality. The second and third of these may seem rather obtuse, but bear with me.

Let’s start with the first, the history of physics. Here, we follow in the footsteps of Thomas Kuhn (1922–1996). He was probably the first philosopher of science to actually look at the history of science to understand how science works. One of his conclusions was that the interior constructs of models (paradigms in his terminology) do not correspond (refer in the philosophic jargon) to anything in reality. It is easy to see why. One can think of a sequence of models in the history of physics. Here we consider the Ptolemaic system, Newtonian mechanics, quantum mechanics, relativistic field theory (a combination of quantum mechanics and relativity) and finally quantum gravity. The Ptolemaic system ruled for half a millennium, from the second to seventeenth centuries. By any standard, the Ptolemaic model was a successful scientific model since it made correct predictions for the location of the planets in the night sky. Eventually, however, Newton’s dynamical model caused its demise. At the Ptolemaic model’s core were the concepts of geo-centrism and uniform circular motion. People believed these two aspects of the model corresponded to reality. But Newton changed all that. Uniform circular motion and geo-centrism were out and instantaneous gravitation attraction was in. Central to the Newtonian system was the fixed Euclidean space time geometry and particle trajectories. The first of these was rendered obsolete by relativity and the second by quantum mechanics; at least the idea of fixed number of particles survived–until quantum field theory. And if string theory is correct, all those models have the number of dimensions wrong. The internal aspects of well-accepted and successful models disappear when new models replace the old. There are other examples. In the history of physics, the caloric theory of heat was successful at one time but caloric vanished when the kinetic theory of heat took over. And on it goes. What is regarded as central to our understanding of how the world works goes puff when new models replace old.

On to the second reason for doubting realism–the role of transformations: canonical and unitary.  In both classical and quantum mechanics there are mathematical transformations that change the internals of the calculations[1] but leave not only the observables but also the structure of the calculations invariant. For example, in classical mechanics we can use a canonical transformation to change coordinates without changing the physics. We can express the location of an object using the earth as a reference point or the sun. Now this is quite fun; the choice of coordinates is quite arbitrary. So you want a geocentric system (like Galileo’s opponents), no problem. We write the equation of motion in that frame and everyone is happy. But you say the Earth really does go around the sun. That is equivalent to the statement: planetary motion is more simply described in the heliocentric frame. We can go on from there and use coordinates as weird as you like to match religious or personal preconceptions.  In quantum mechanics the transformations have even more surprising implications. You would think something like the correlations between particles would be observable and a part of reality. But that is not the case. The correlations depend on how you do your calculation and can be changed at will with unitary transformations. It is thus with a lot of things that you might think are parts of reality but are, as we say, model dependent.

Finally we come to Bell’s inequality as the third reason to doubt realism. The idea here goes back to what is known as the Einstein-Podolsky-Rosen paradox (published in 1935). By looking at the correlations of coupled particles Einstein, Podolsky, and Rosen claimed that quantum mechanics is incomplete.  John Bell (1928 – 1990), building on their work, developed a set of inequalities that allowed a precise experimental test of the Einstein-Podolsky-Rosen claim. The experimental test has been performed and the quantum mechanical prediction confirmed. This ruled out all local realistic models. That is, local models where a system has definite values of a property even when that property has not been measured. This is using realism in the second sense defined above. There are claims, not universally accepted, that extensions of Bell’s inequalities rule out all realist models, local or non-local.

So where does this leave us? Pretty much with the concept of realism in science in tatters. The internals of models changes in unpredictable ways when science advances. Even within a given model, the internals can be changed with mathematical tricks and for some definitions of realism, experiment has largely ruled it out.  Thus we are left with our models that describe aspects of reality but should never be mistaken for reality itself. Immanuel Kant (1724 – 1804), the great German philosopher, would not be surprised[2].

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[1] For the relation between the two type of transformations see: N.L. Balazs and B.K. Jennings, Unitary transformations, Weyl’s association and the role of canonical transformations, Physica, 121A (1983) 576–586

[2] He made the distinction between the thing in itself and observations of it.

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10 Responses to “Is there a place for realism in science?”

  1. Uncle Al says:

    So where does this leave us?” Testably in error. Particle and gravitation theories postulate massless boson photon vacuum symmetries are exactly those toward fermionic matter (quarks), then parity violations, chiral anomalies, symmetry breakings; Chern-Simons repair of Einstein-Hilbert action. Unification empirically fails.

    Vacuum trace chiral anisotropy toward matter alters Noetherian coupling of exact vacuum isotropy to angular momentum conservation. It leaks for matter as MoND’s 1.2×10^(-10) m/s^2 Milgrom acceleration. Dark matter is epicycles.

    A left foot is invisible to socks but not to a pair of shoes. A vacuum left foot appears within five classes of experiment testing spacetime geometry with atomic mass distribution geometry: visually and chemically identical, single crystal test masses in enantiomorphic space groups. Yang and Lee (Phys. Rev. 104(1) 254 (1956); 105(4) 1413 (1957)) reiterated 1928 Cox (PNAS 14(7) 544 (1928)), but Cox was “impossible.” Parity violations are vacuum diagnostics. Empirically falsify an inexact postulate. Fix the problem, mourn the dead, and get on with the job.

  2. Tienzen (Jeh-Tween) Gong says:

    Truly an excellent article.

    Realism is a discipline in philosophy, and your argument belongs one of its school. That is, your point of view is consistent in your own school. Thus, there is no point for me to disagree with it. Yet, I am confused on some of your statements. Then, if you allow, I would like to discuss an off-topic issue, the reality (not the Realism). Again, I would like to beg your permission to use your examples to discuss this issue.

    “… By any standard, the Ptolemaic model [describes ‘a what’] was a successful scientific model … Eventually, however, Newton’s dynamical model caused its demise.”

    Demise of what? What is the connection between Ptolemy and Newton; friends, enemies or players of an ‘a what’ ball game? Demise of Ptolemy or the demise of the ‘a what’? By the way, ‘who’ is the judge for deciding that the demise is Ptolemy, not Newton? ‘What standard’ that this ‘who’ used for his judgment? Is this ‘what standard’ something about the ‘a what’? Is this ‘who’ a reality?

    “In quantum mechanics the transformations [on the members of ‘a what’] … But that is not the case. The correlations depend on how you do your calculation and can be changed at will with unitary transformations.”

    What is the point here? Why is this quantum phenomenon (reality ?) a big deal? Is the quantum mechanics a joke? Or the ‘a what’ a jerk?

    “This [EPR experiment] ruled out all local realistic models. … There are claims, not universally accepted, that extensions of Bell’s inequalities rule out all realist models, local or non-local.”

    Ruling out all those ‘models’; excellent, job well-done. But, is the ‘a what’ being ruled out?

    I am 100% agree with your conclusion that “It is thus with a lot of things that you might think are parts of reality but are, as we say, model dependent.” But, is the reality model dependent or the ‘model’ model dependent? Is the “realities that we think” has anything to do with the ‘a what’ that I, Ptolemy and Newton talked about here? I personally believe that there is a big difference between ‘a model’ and the ‘a what’. I personally will never construct any model (of what) but try to make contact to something known, such as, Electron fine structure constant, the Planck data, etc.. When those contacts are firmly made, we have touched the forever elusive ‘a what’. In this sense, I agree with Thomas Kuhn: that the interior constructs of models (paradigms in his terminology) do not correspond to anything in reality; and agree with Immanuel Kant: the distinction between the thing in itself and observations of it. In the following equations, I am choosing the first one.
    Forever elusive ‘a what’ = human stupidity
    Forever elusive ‘a what’ = non-reality of the ‘a what’
    I have no concern about the model. As long as I can make contact to the ‘a what’ in a small way (such as, being able to eat and to breathe, not easy tasks by all imagination), I have fulfilled my mission for this Earthly journey (part of this ‘a what’).

  3. Emmanuel says:

    I do not agree with the precise form of Thomas Kuhn statement:the interior constructs of models (paradigms in his terminology) do not correspond to anything in reality. And so partly – with the comments. One should define what is meant by “correspond to anything in reality”, especially my disagreement is related to the adjective “anything”. By definition, Ptolemaic model correspond to reality by perception of sun’s movement relative to the earth. The Newton model – by movement of the earth relative to sun, etc. Of cause, in physics there cannot be a model that completely agrees with anything in reality. But what is the full and absolute ‘reality’? It cannot be such thing in physics, it is just beyond the definition of physics. Nevertheless, the models are needed in physics to connect physical observations, and the connections in different models may differ because of different volumes of observations that they connect. These connections (interior constructs) if detached from the observation results do not correspond to reality.

    • Tienzen (Jeh-Tween) Gong says:

      @Emmanuel:
      “Nevertheless, the models are needed in physics to connect physical observations …”.

      This is indeed the slogan waved by almost every physicist. But, I do not truly understand what the heck this slogan means.

      There are four steps for the growth of ‘human’ physics.
      Step one, collecting data — knowing the phenomena.
      Step two, finding the pattern (with equations to best fit the data) — these equations have *variables* and *parameters*.
      Step three, finding the underlying causes (dynamics) for the equations (especially for the variables).
      Step four, finding the underlying framework for the *parameters*, deriving parameters from an axiomatic system.

      Are the step 2 and 3 the model building? If it is, this model is firmly based on the observations (the step one). That is, this type of model should be called the ‘derived’ model.

      Yet, in the current physics mainstream, the top dogs are SUSY (with s-particles) and Multiverse. Multiverse by definition cannot be connected by any observation, and SUSY has zero observation-base. Are these two models? If they are, they should be called ‘hallucination’ model.

      Then, there is a bigger issue. The proper step after the step three (model building) should be step four. As the mainstream physics thus far has failed to reach the step four, it has taken a detour (a small trail) which is the interplay of model and verification. That is, that model must predict an unknown. Now, we have two pathways.
      1. Proper highway — bridging to step four.
      2. Small trail — groping into the unknown.

      Thus, there are three types of observations.
      a. The base observations — the base for the ‘derived’ model.
      b. The unanswered known observations — the parameters of the step four.
      c. The observation of the unknown, predicted by a model.

      We can of course argue over which pathway is the proper (or better) one, but it is beyond the scope of the current discussion. My point is about your slogan with two questions.
      First, what kind of models are you talking about?
      Second, what type of observations do you try to connect to?

      Without knowing the answers of these two questions, I have no idea of what that slogan is talking about.

      “But what is the full and absolute ‘reality’? It cannot be such thing in physics, it is just beyond the definition of physics.”

      Again, this is a great slogan which cannot be derived by any kind of logic but is a dogmatic statement.

      First, can we firmly grasp the elusive ‘a what’ after the step four is completed? My opinion is Yes. Of course, you can disagree with me with your opinion. But, you opinion (as you have not completed the step four) should not be the logic base for the validity of that slogan.

      Second, there are two types of physics.
      One, the human physics — developed with the four steps above. Without the completion of the step four, the slogan does describe that status.

      Two, the Nature physics — it has only three steps (ready, get set, go). It is, in fact, in a reverse-order (from axiom system to phenomena) of the human steps.

      That is, even if the ‘a what’ is forever elusive in human physics, it is all clear in the Nature physics. Before I know what kind of physics you are referring to, I have no idea of what that slogan is all about.

    • Byron says:

      Gong’s step two is not quite the case. building scientific models is not a simple case of pattern matching. There are an infinite number of patterns that match nay finite data set and the model may be very obscure. Going from atomic structure to quantum theory is more than simple pattern matching. A great deal of creativity is required.

  4. Matt Dorans says:

    An interesting read. Only defining reality will and cannot occur until the physics is redefined as is yet very much misunderstood.

    I will be publishing in the next few months where by even the rusting titanic will be rocked

    Matt Dorans
    Theoretical/ Experimental Physicist

  5. Jeremy says:

    Nice post. I’ve written a little bit about this subject, but I haven’t seen some of the more specific objections (your second and third points) toward realism before.

    Regarding the first point, would you say that the sequence of models in physics is approaching describing reality?

    • Tienzen (Jeh-Tween) Gong says:

      @Jeremy: “Regarding the first point, would you say that the sequence of models in physics is approaching describing reality?”

      I think so.

      If something is observed, it should get a status as ‘fact’. If there is an underlying framework under that fact, that framework should gain a status as a ‘base-fact’. When a base-fact can be described in two seemingly unrelated ways and if those two unrelated descriptions turn out to be completely isomorphic, then that underlying ‘base-fact’ could gain one more promotion to the status of ‘reality’.

      On January 1, 2014, Amir Mulic published a new formula for Alpha {(4π^3+π^2+π), see (http://vixra.org/abs/1401.0037 )}. Although he has M-string interpretation for his formula, it is still basically a numerological formula. Yet, when it is rewritten with the following equation, the physics significance is now all clear.

      Let 2 π = the circumference of a unit disk (with radius = 1) = Pie
      π = half Pie = HPie
      Then, his formula can be written as,
      (1/α) = (1/2) {Pie * [(Pie + 1/Pie)^2 + (HPie – 1/HPie) – ((1/Pie) – 1)^2]} … equation A

      The equation A can be rewritten as below.
      (Pie + 1/ Pie), type 1 mixing (division); (Pie + 1/ Pie)^2, the first order mixing
      (HPie – 1/HPie), type 2 mixing (division), the second order mixing
      [(1/Pie) – 1]^2, the ‘remainder’ (indivisible) of the division

      So, equation A = (1/2) Pie * (the first order mixing + the second order mixing – the ‘remainder’ of mixing)

      Thus, although Amir Mulic’s formula (4π^3+π^2+π) is purely numerological, it shows that the Alpha is about the division (or sharing) a (the) pie (universe), with this rewritten equation. And, this is exactly the same underlying framework as my Alpha equation (with the Weinberg angle), sharing a pie.

      I am trying to show two points there.
      1. Some realities (observed facts, such as Alphya) can be contacted by models. Then, there is no reason for the ‘final reality’ to be beyond the reach of models.
      2. When two unrelated models point to a same ‘fact’, that fact is more than an observable phenomenon but has an underlying ‘reality’.

  6. […] if scientific realism was a thing that scientists themselves were unsure about, here’s a blog post (via @realscientists) by a physicist about it, which concludes as […]

  7. Mike says:

    I guess it’s understandable that you’re somewhat tentative when it comes to the scientific method, in the sense that it’s almost impossible to avoid as you’re confirming the kind of predictability that’s been well documented for a couple of centuries. The only way to invoke a paradigm shift is to be confounded by the evidence, instead of trying to explain it away as unphysical.
    Hubble’s Law is what wouldn’t have come to mind thirty years ago, because just about everybody had given up on wanting to get a sense of the underlying physics that seemed to be eluding disinterested theorists. There was no way to admit defeat until dark energy came along, as an evasion, really, for the sake of the uncultured masses, relying on the entertainment industry to furnish the kind of escapism that can mistaken for a scientific understanding, as if converging on an epiphany of some kind. Dementia, in it’s most distilled form, prevailing in the guise of a discerning perspective.
    The big bang theory is something else again, a goofy precept that you tend to associate with that particular era. The eighties, basically. Kitsch is what they used to call it. A period piece, all the way. It’s funny, because there’s no way to get a sense of what the concerns might have been. The real concerns. There weren’t any, presumably, and it’s okay to feel nostalgic. Had it been effectively subsumed by an utterly stable ‘model’ that seems to jive with the evidence, it would be almost impossible to revert back to the illusions. Entertain the possibility that the universe might have originated, somehow, thanks to the suspension of the usual kind of physical laws that you’re accustomed to. Or that it might collapse in on itself.
    Illusions can dissolve unexpectedly. For sure. Happens all the time. Frankly acknowledged. It’s almost a badge of courage. A sign of sophistication. But who are you surrendering to? It would have to be an all encompassing antisaviour that’s capable of quelling the concerns. It’s like somebody suggesting that Adolf Hitler was a bit of a flake. Maybe it’s time for the real deal. A specially devised inquisition at the expense of a dull witted priestly caste that likes to imagine that they’re ruling the roost. Buying into the hoax of a mythical elite, for the sake of convenience. And claiming to be dead set against any form of organized religion, as part of the bargain.
    If you’re wanting to invoke the learned helplessness routine, you’re going to have to understand that there’s nobody out there. I don’t know how many views you’re getting with your blog, but based on the commentary you’re either preaching to the converted or failing to interest ordinary folks that aren’t very well educated, at least formally, in the lucid perspectives you seem to be offering up. To the extent that there really is such a thing as peer review, it’s failing miserably. It’s the same with Pauline Gagnon’s blog from CERN.
    Which is too bad, because it’s really interesting. For the average layperson. From a detached perspective. As long as you’re not professionally employed as a scholar, you don’t have to worry. It’s quite possible to relax and be amused by the debate that seems to be going on. It’s the logical progression from the ‘reality shows’ that were turning ordinary people into well known celebrities back in the nineties.
    The conventional wisdom is that it’s come to fruition. The Higgs boson was finally detected, and it needed to be documented. The kind of accomplishment that only happens once every fifty years or so. A huge anticlimax from here on out. The routine experimentation that’s being arranged for. Theorists are pretty much out of luck. If there are huge holes in the fabric of assumptions being made, they will never be detected or pointed out.

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