This joblessness, for catching up on my reading, I have been having a more detailed look at Bohm’s theory.
In the past, I had written a longish post on it [^]. However, I thought I could perhaps have a re-look at this theory, and try to write something more concisely. Here are my current thoughts (though not very concisely).
BTW, in my last post, though it was a bit too free-wheeling and longish, I had not noted anything about Bohm’s personal life or character. So let me note down something about it, and thereby get it out of the way, before we come to his physics.
I haven’t read any biographical book on Bohm (nor am I interested in reading one), but from what I gather by browsing brief articles on the ‘net, I think that you can’t hold that McCarthy affair against him, even if as a young man, he sincerely believed in Marxism. [Yes, I myself continue to believe in Capitalism, but read on anyway.] I also don’t hold his association with Jiddu Krishnamurti against him. [Yes, JK was a real funny British creation, even if based on an Indian version of mysticism.] If I must comment on Bohm’s personal life, the first thing I would say, i.e., apart from noting his bewildering naiveté, is that he obviously deserved a PhD advisor/boss better than Oppenheimer, a country better than the USA (or the way it treated him anyway), and an intellectual Guru better than JK. He turned (partly) lucky on only one of the three counts. Unfortunate.
He also deserved an audience better than the 20th century physicists. And, his physics, I now believe, deserves a bit better estimate than what I think I accorded it the last time.
Bohm’s theory, that way, is not much different from the standard mainstream QM. His theory, I think, essentially is:
(c) with an ontological separation of the quantum into the wave and the particle as two distinct kinds of entities,
(d) and, truly remarkably, having particles inhabiting only a 3D space.
It’s obvious that modern physicists would hate him for (a), and they do.
It would be expected that they should love him for (b), but they don’t. Their passion on the count of (a) has been so strong that they can’t even notice (b).
They wouldn’t a care a hoot about (c) simply because it’s “all philosophical” to them. On this count, they do deliver completely as expected.
And, they to this day haven’t allowed themselves to know that they also hate him because of (d). Since they don’t know it, they just silently chew their lips as they hurriedly skip over this feature of Bohm’s theory.
In contrast, my biggest problems with Bohm’s theory have been (b) and (c).
I was on my guard regarding (a) on two counts: (i) so many attempts at giving a deterministic theory have been so negligent of so many QM features or so much observational data, or have been so outright foolish, that even I couldn’t keep too much enthusiasm for a deterministic theory—one tends to think that in view of the success of probability in classical statistical mechanics, the probability in QM must be a simple interpretation issue. (ii) In philosophization, the determinism-oriented people slip so easily into a denial of free will.
Still, I now realize that we should applaud Bohm for (a), i.e., determinism. We could even be thankful to him for upholding it despite a bitter opposition.
And, if you ask me, we should be even more grateful to him for (d), i.e., for keeping his particles only in a 3D space. (I have to finish my series of posts on space, and when I return to it, I will make it a point to address this issue.)
Now, let’s look at the points (b) and (c), i.e., the non-locality and the ontological separation, in more detail.
Regarding the non-locality, it’s only recently—as recently as this month—that I seem to have finally come to agree that I don’t have a good argument to necessarily deny instantaneous action at a distance (IAD) in every physical theory. (When David Harriman had noted in the mid-naughties on some forum that IAD was not an issue of philosophy, that it is not a task of philosophers to ponder whether one end of the see-saw goes up literally at the same exact time that the other end is pushed down, I had thought that it should be possible to figure this issue out on the philosophic grounds alone, more particularly, on the epistemological grounds. Now I no longer seem to think so.)
But that does not mean that I have jumped over on to the IAD side in general? No! Not at all.
All that I have realized here is that you can’t deny IAD on the basis of the principle of identity, or on epistemological grounds. In other words, the idea is not arbitrary, i.e., it is not devoid of any fundamental cognitive merit. No matter how ridiculous it may sound, a proper theory of physics could still, perhaps, have IAD built into it. Despite Einstein’s relativity.
In my own theorization, of course, I would continue to have locality. My insistence on having locality in a physical theory (or the reason to deny IAD) never was based on the relativistic objection. It was based on a simple consideration: I always thought that when I tossed a ball, or a typed a key, I was not directly and instantaneously affecting the path of a pebble rolling somewhere at the bottom of the Grand Canyon. That, if A, B, and C are three objects situated in space next to each other in the given sequence, then a disturbance from A must first travel to B before it gets to C. This has been just a “native” conviction for me, that’s all. In XI standard, while reading Newtonian mechanics, my mind couldn’t stay focused on calculating acceleration of a ball once it is hit by a bat. The reason wasn’t a lack of a mathematical reasoning ability. The reason was, knowing that a ball was not a particle, I would wonder how the hit must be propagating inside the finite ball, and what it would take to understand this issue really well (the stress waves, I learnt later, but couldn’t explain the issue well right back in XI standard to friends as to why the then text-book explanation based on impulse and all falls short—I only insisted that it does). Wanting to explain the stationary via the transient—or at least wanting to relate the two—has been native to me, to my natural thought processes. (That’s how the sub-title of this blog.) … So, I would continue building my theorization via the local and propagation-al processes.
For the same reason, I also have had this resistance to accept the viability of IAD in a theory of physics. But, finally, I seem to have built some argument to show that IAD could be a reasonable view to take.
IAD would be a relatively easier to accept in a fully deterministic i.e. materialistic world, one that is devoid of any willed (or even just animate) physical action. In the literally clockwork universe, IAD would be easier to believe. How?
Before we come to that point, let us pause to consider another characteristic of Bohm’s theory—the place where my quantum approach (or call it attempt at to build one) differs from his. Recall my past posts on the nature of space, on what I call the foreground objects (say the physical things you see such as apples, trees, buildings, planets, etc.) and the background object (or the aether).
The point concerns what dynamical attributes are carried by which—the usual material (or massive) objects and the aether/field/”empty space”. Since a physical theory must have both of them, I now realize, it should be possible to think of a whole spectrum of theories based on how they partition these two aspects.
In Newton’s particle and finite-body mechanics, it’s the material objects that carry all the dynamically important attributes; the empty “absolute” space simply sits idle. In contrast, in Maxwell’s classical electromagnetism, both the material objects and the fields carry the necessary physical (dynamical) attributes, and an interaction between the two is necessary for a complete physical description. In Bohm’s mechanics, this trend reaches its logical extreme: it’s the Bohmian field that is the true dynamical causal agent; the particles are completely passive.
There, of course, is a position that is even more “extreme” continuing in the same direction, but it falls outside of the spectrum because it is so thoroughly illogical: the mainstream QM. Here, like in Bohm’s mechanics, it’s the “other thing” (say Schrodinger’s wavefunction) that does everything dynamical, but the difference is this: you can’t even say that particles are completely passive because, the mainstream QM insists, the particles can’t even be said to exist unless when observed, and the wavefunction can’t be seen as a 3D phenomenon in the general case of many particles. So, logically speaking, it’s only Bohm’s theory that represents the extreme end of the possible spectrum.
So, there. Newton–Maxwell–Bohm. All the other proper theories fall in between. For instance, molecular dynamics falls in between Newton’s and Maxwell’s, and Higg’s theory, I suppose, could be taken to lie between Maxwell’s and Bohm’s. Bohm’s theory indeed is at the logical extreme (leaving aside the mainstream QM that randomly falls off the table).
Now, if the “empty” thing/field is the real physical agent, IAD becomes more easily believable. Why? Because, quantitatively, there exist only one causal agent, all by itself. When this entity acts, it must act as a whole. And, now, the key point: This action of the whole doesn’t have to be divisible across the parts. The action indeed may be quantitatively different for the different parts (e.g. the force being generated in one part may be more than that being generated in some other part), but inasmuch as it’s the only object in the entire universe, whatever it does is only a single action. Such an action may be taken as carrying a kind of IAD.
Strictly speaking, it’s not exactly IAD in the usual sense of the term. It’s not some action that one object exerts over some other object lying at some distance and somehow instantaneously. It’s an instantaneous action at every point of the same object. It’s a bit like morphing an image: say, a circle expanding to a bigger circle, or a ring carrying some waves transverse to its central fiber. Here, all points are taken to move simultaneously, and so, you could arguably describe it by saying that the motion of one point has an instantaneous effect at another point.
That’s the best possible argument I could come up with, in support of the IAD.
I still have a feel that it all is a nonsense, but let’s be clear about distinguishing a mere feel from a reasoned argument.
Now, if you can ascribe all the essential dynamics to that single object i.e. the Bohmian field, then the possibility of IAD within that field is, how to put it, without a soundly opposing argument.
Then, once you sprinkle some particles in it, the rest of the Bohmian mechanics follows.
But, do note very carefully what is being conceded here. All that I have so far conceded is that the presence of a sound argument necessitating a denial of this kind of a theoretical IAD—the one occurring in a “field” where the field is the exclusive actor in the entire universe. It’s only the universe that ever acts; the parts have no such freedom in such a world, but they may be abstractly seen to have instantaneous influences on each other. All that I am saying is that I have no argument against this kind of an IAD.
But I thereby do not concede that this kind of a theorization (the one involving IAD) is necessary to explain the quantum phenomena. IMO, a good, logical QM theory can also be local in nature—nay, it must be.
Now, even if you grant IAD to the Bohmian field, there is another issue that Bohmian mechanics runs into, viz., the ontological separation between the particles and the field.
If the field is the exclusive actor—as required by the IAD—then it leaves no ontological place in the theory for any particles at all. If so, why are they there?
(Or, if you like: if the American society is a single object that can do all the productive work necessary for itself, then why sprinkle immigrants into it?)
Thus, if the particles are ontological (i.e. if they at all exist in this world as objects), then the field cannot be the exclusive actor in the universe, and so, IAD is ruled out. On the other hand, if the IAD is to be retained in the theory, then to make it the exclusive actor, the particles have to be taken out of that theory; they cannot be more that mere visualization aids.
In the first case, the particles are like the tracer particles in an actual flow of a real fluid—they do affect the flow locally, they are not dynamically passive entities, and so IAD for them is as spooky as lifting your arm and thereby causing a dust particle in the next room or a mountain on the Mars instantaneously move up, too.
In the second case, the particles are like the arrows drawn on a photograph of a real flow—they cannot affect the flow but neither are they actually moving in the actual flow in the reality out there.
You see, IAD is a tough thing to accommodate in a physical theory—whether in the diffusion of carbon in steel, or mainstream QM, or Bohmian QM.
If the Bohmian mechanics is that bad, then why am I reading it? especially since I do seem to know better? Good question.
Answer: Because, even if it is that bad, it is no more worse than that. It certainly is not as bad as its critics make it out to be. In fact, this theory actually becomes the better exactly for the reasons its mainstream critics hate it: determinism and 3D space. And the introduction of these two features make it a far more easily understandable wrong theory. As compared to others. … You see, a theory based on particles moving in only a 3D space does not have to bother about bringing results from 4, 5, 10 or 1000 dimensions back to a space of three dimensions—the symmetries or otherwise of the collapse of dimensions. And, precisely because it’s deterministic with definite trajectories, with particles always moving forward in time, it is easy to grasp, believe even if only temporarily, visualize even if the variables are only hidden, and, possibly also easier to calculate, at least in many situations. Classical determinism, with the feature of a 3D space reduces the cognitive load enormously.
So, as a bottom line, Bohm’s theory is wrong, but “good”!
It sure does not resolve the QM riddles, e.g., the wave-particle duality, but it does essentialize these riddles very well, even, brilliantly. In any case, it does so better than any of the existing QM interpretations. That’s why, it is a good idea to study it.
For most people, this theory should be a good step to get out of the totally mystical abyss of the mainstream QM, even though it wouldn’t get you completely out of it—it might get you out, perhaps, say, some half-way through. But, yes, the air will be fresher, and you will see a greater expanse of the sky.
Little wonder that Ayn Rand-admiring physicists like Dr. Travis Norsen or Dr. Eric Dennis took as much enthusiastically to it as they did. … If there were no Ayn Rand, and no ancient Indian wisdom, one can still be certain, one would have been an Aristotlean. No comparison of the scale even suggested in any sense, but merely as a matter of stating a fact, if I were not to have my approach—or at least some early success with it—I would have ended up being a Bohmian.
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If you want some good pointers to the literature on the Bohmian mechanics, go to “Bohmian-Mechanics.net” [^]. Make sure to see the frequently asked questions [^], PDF document [^].
Just one more point before closing. There are many other, more detailed or more technical objections against Bohm’s theory. For instance, people object that Bohmian mechanics is inapplicable for photons, for relativistic situations, etc. Some of these don’t hold any water; other objections should go away in future (may be within 10–20 years). I mean, generally, I think, you can expect the scope of Bohmian mechanics to be the same as that of the mainstream QM. If there is a mainstream QM theory to explain a certain phenomenon, then, in principle, it must be possible to extend the existing Bohmian approach (even if not the exact mechanics currently existing) to include those same features, too. That’s what I anticipate. With the QM, unless it is made a local theory, all workable interpretations are in a way equivalent, and selection of any one is just a matter of suitability to attack a given problem, or even of personal choice! Bohm’s theory is more than an interpretation (who else has only a 3D space? determinism? forward time?), even if its development as of today may not be as complete as compared to the other interpretations.