# Absolutely Random Notings on QM—Part 3: Links to some (really) interesting material, with my comments

The “pride of place” for this post goes to a link to this book:

Norsen, Travis (2017) “Foundations of Quantum Mechanics: An Exploration of the Physical Meaning of Quantum Theory,” Springer

This book is (i) the best supplementary book for a self-study of QM, and simultaneously, also (ii) the best text-book on a supplementary course on QM, both at the better-prepared UG / beginning PG level.

A bit expensive though, but extensive preview is available on Google books, here [^]. (I plan to buy it once I land a job.)

I was interested in the material from the first three chapters only, more or less. It was a delight even just browsing through these chapters. I intend to read it more carefully soon enough. But even on the first, rapid browsing, I noticed that several pieces of understanding that I had so painstakingly come to develop (over a period of years) are given quite straight-forwardly here, as if they were a matter of well known facts—even if other QM text-books only cursorily mention them, if at all.

For instance, see the explanation of entanglement here. Norsen begins by identifying that there is a single wavefunction, always—even for a multi-particle system. Then after some explanation, he states: “But, as usual in quantum mechanics, these states do not exhaust the possibilities—instead, they merely form a basis for the space of all possible wave functions. …”… Note the emphasis on the word “basis” which Norsen helpfully puts.

Putting this point (which Norsen discusses with a concrete example), but in my words: There is always a single wavefunction, and for a multi-particle system, its basis is bigger; it consists of the components of the tensor product (formed from the components of the basis of the constituent systems). Sometimes, the single wavefunction for the multi-particle system can be expressed as a result of a single tensor-product (in which case it’s a separable state), and at all other times, only as an algebraic sum of the results of many such tensor-products (in which case they all are entangled states).

Notice how there is no false start of going from two separate systems, and then attempting to forge a single system out of them. Notice how, therefore, there is no hand-waving at one electron being in one galaxy, and another electron in another galaxy, and so on, as if to apologize for the very idea of the separable states. Norsen achieves the correct effect by beginning on the right note: the emphasis on the single wavefunction for the system as a whole to begin with, and then clarifying, at the right place, that what the tensor product gives you is only the basis set for the composite wavefunction.

There are many neat passages like this in the text.

I was about to say that Norsen’s book is the Resnick and Halliday of QM, but then came to hesitate saying so, because I noticed something odd even if my browsing of the book was rapid and brief.

Then I ran into

Ian Durham’s review of Norsen’s book, at the FQXi blog,

which is our link # 2 for this post [^].

Durham helpfully brings out the following two points (which I then verified during a second visit to Norsen’s book): (i) Norsen’s book is not exactly at the UG level, and (ii) the book is a bit partial to Bell’s characterization of the quantum riddles as well as to the Bohmian approach for their resolution.

The second point—viz., Norsen’s fascination for / inclination towards Bell and Bohm (B&B for short)—becomes important only because the book is, otherwise, so good: it carries so many points that are not even passingly mentioned in other QM books, is well written (in a conversational style, as if a speech-to-text translator were skillfully employed), easy to understand, thorough, and overall (though I haven’t read even 25% of it, from whatever I have browsed), it otherwise seems fairly well balanced.

It is precisely because of these virtues that you might come out giving more weightage to the B&B company than is actually due to them.

Keep that warning somewhere at the back of your mind, but do go through the book anyway. It’s excellent.

At Amazon, it has got 5 reader reviews, all with 5 stars. If I were to bother doing a review there, I too perhaps would give it 5 stars—despite its shortcomings/weaknesses. OK. At least 4 stars. But mostly 5 though. … I am in an indeterminate state of their superposition.

… But mark my words. This book will have come to shape (or at least to influence) every good exposition of (i.e. introduction to) the area of the Foundations of QM, in the years to come. [I say that, because I honestly don’t expect a better book on this topic to arrive on the scene all that soon.]

Which brings us to someone who wouldn’t assign the $|4\rangle + |5\rangle$ stars to this book. Namely, Lubos Motl.

If Norsen has moved in the Objectivist circles, and is partial to the B&B company, Motl has worked in the string theory, and is not just partial to it but even today defends it very vigorously—and oddly enough, also looks at that “supersymmetric world from a conservative viewpoint.” More relevant to us: Motl is not partial to the Copenhagen interpretation; he is all the way into it. … Anyway, being merely partial is something you wouldn’t expect from Motl, would you?

But, of course, Motl also has a very strong grasp of QM, and he displays it well (even powerfully) when he writes a post of the title:

“Postulates of quantum mechanics almost directly follow from experiments.” [^]

Err… Why “almost,” Lubos? 🙂

… Anyway, go through Motl’s post, even if you don’t like the author’s style or some of his expressions. It has a lot of educational material packed in it. Chances are, going through Motl’s posts (like the present one) will come to improve your understanding—even if you don’t share his position.

As to me: No, speaking from the new understanding which I have come to develop regarding the foundations of QM [^] and [^], I don’t think that all of Motl’s objections would carry. Even then, just for the sake of witnessing the tight weaving-in of the arguments, do go through Motl’s post.

Finally, a post at the SciAm blog:

“Coming to grips with the implications of quantum mechanics,” by Bernardo Kastrup, Henry P. Stapp, and Menas C. Kafatos, [^].

The authors say:

“… Taken together, these experiments [which validate the maths of QM] indicate that the everyday world we perceive does not exist until observed, which in turn suggests—as we shall argue in this essay—a primary role for mind in nature.”

No, it didn’t give me shivers or something. Hey, this is QM and its foundations, right? I am quite used to reading such declarations.

Except that, as I noted a few years ago on Scott Aaronson’s blog [I need to dig up and insert the link here], and then, recently, also at

Roger Schlafly’s blog [^],

you don’t need QM in order to commit the error of inserting consciousness into a physical theory. You can accomplish exactly the same thing also by using just the Newtonian particle mechanics in your philosophical arguments. Really.

Yes, I need to take that reply (at Schlafly’s blog), edit it a bit and post it as a separate entry at this blog. … Some other time.

For now, I have to run. I have to continue working on my approach so that I am able to answer the questions raised and discussed by people such as those mentioned in the links. But before that, let me jot down a general update.

A general update:

Oh, BTW, I have taken my previous QM-related post off the top spot.

That doesn’t mean anything. In particular, it doesn’t mean that after reading into materials such as that mentioned here, I have found some error in my approach or something like that. No. Not at all.

All it means is that I made it once again an ordinary post, not a sticky post. I am thinking of altering the layout of this blog, by creating a page that highlights that post, as well as some other posts.

But coming back to my approach: As a matter of fact, I have also written emails to a couple of physicists, one from IIT Bombay, and another from IISER Pune. However, things have not worked out yet—things like arranging for an informal seminar to be delivered by me to their students, or collaborating on some QM-related simulations together. (I could do the simulations on my own, but for the seminar, I would need an audience! One of them did reply, but we still have to shake our hands in the second round.)

In the meanwhile, I go jobless, but I keep myself busy. I am preparing a shortish set of write-ups / notes which could be used as a background material when (at some vague time in future) I go and talk to some students, say at IIT Bombay/IISER Pune. It won’t be comprehensive. It will be a little more than just a white-paper, but you couldn’t possibly call it even just the preliminary notes for my new approach. Such preliminary notes would come out only after I deliver a seminar or two, to physics professors + students.

At the time of delivering my proposed seminar, links like those I have given above, esp. Travis Norsen’s book, also should prove a lot useful.

But no, I haven’t seen something like my approach being covered anywhere, so far, not even Norsen’s book. There was a vague mention of just a preliminary part of it somewhere on Roger Schlafly’s blog several years ago, only once or so, but I can definitely say that I had already had grasped even that point on my own before Schlafly’s post came. And, as far as I know, Schlafly hasn’t come to pursue that thread at all, any time later…

But speaking overall, at least as of today, I think I am the only one who has pursued this (my) line of thought to the extent I have [^].

So, there. Bye for now.

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As usual, some editing after even posting, would be inevitable.

Some updates made and some streamlining done on 30 July 2018, 09:10 hrs IST.

# Absolutely Random Notings on QM—Part 1: Bohr. And, a bad philosophy making its way into physics with his work, and his academic influence

TL;DR: Go—and keep—away.

I am still firming up my opinions. However, there is never a harm in launching yet another series of posts on a personal blog, is there? So here we go…

Quantum Mechanics began with Planck. But there was no theory of quanta in what Planck had offered.

What Planck had done was to postulate only the existence of the quanta of the energy, in the cavity radiation.

Einstein used this idea to predict the heat capacities of solids—a remarkable work, one that remains underappreciated in both text-books as well as popular science books on QM.

The first pretense at a quantum theory proper came from Bohr.

Matter, esp. gases, following Dalton, …, Einstein, and Perin, were made of distinct atoms. The properties of gases—especially the reason why they emitted or absorbed radiation only at certain distinct frequencies, but not at any other frequencies (including those continuous patches of frequencies in between the experimentally evident sharp peaks)—had to be explained in reference to what the atoms themselves were like. There was no other way out—not yet, not given the sound epistemology in physics of those days.

Thinking up a new universe still was not allowed back then in science let alone in physics. One still had to clearly think about explaining what was given in observations, what was in evidence. Effects still had be related back to causes; outward actions still had to be related back to the character/nature of the entities that thus acted.

The actor, unquestionably by now, was the atom. The effects were the discrete spectra. Not much else was known.

Those were the days were when the best hotels and restaurants in Berlin, London, and New York would have horse-driven buggies ushering in the socially important guests. Buggies still was the latest technology back then. Not many people thus ushered in are remembered today. But Bohr is.

If the atom was the actor, and the effects under study were the discrete spectra, then what was needed to be said, in theory, was something regarding the structure of the atom.

If an imagined entity sheer by its material/chemical type doesn’t do it, then it’s the structure—its shape and size—which must do it.

Back then, this still was regarded as one of the cardinal principles of science, unlike the mindless opposition to the science of Homeopathy today, esp. in the UK. But back then, it was known that one important reason that Calvin gets harassed by the school bully was that not just the sheer size of the latter’s matter but also that the structure of the latter was different. In other words: If you consumed alcohol, you simply didn’t take in so many atoms of carbon as in proportion to so many atoms of hydrogen, etc. You took in a structure, a configuration with which these atoms came in.

However, the trouble back then was, none had have the means to see the atoms.

If by structure you mean the geometrical shape and size, or some patterns of density, then clearly, there was no experimental observations pertaining to the same. The only relevant observation available to people back then was what had already been encapsulated in Rutherford’s model, viz., the incontestable idea that the atomic nucleus had to be massive and dense, occupying a very small space as compared to an atom taken as a whole; the electrons had to carry very little mass in comparison. (The contrast of Rutherford’s model of c. 1911 was to the earlier plum cake model by Thomson.)

Bohr would, therefore, have to start with Rutherford’s model of atoms, and invent some new ideas concerning it, and see if his model was consistent with the known results given by spectroscopic observations.

What Bohr offered was a model for the electrons contained in a nuclear atom.

However, even while differing from the Rutherford’s plum-cake model, Bohr’s model emphatically lacked a theory for the nature of the electrons themselves. This part has been kept underappreciated by the textbook authors and science teachers.

In particular, Bohr’s theory had absolutely no clue as to the process according to which the electrons could, and must, jump in between their stable orbits.

The meat of the matter was worse, far worse: Bohr had explicitly prohibited from pursuing any mechanism or explanation concerning the quantum jumps—an idea which he was the first to propose. [I don’t know of any one else originally but independently proposing the same idea.]

Bohr achieved this objective not through any deployment of the best possible levels of scientific reason but out of his philosophic convictions—the convictions of the more irrational kind. The quantum jumps were obviously not observable, according to him, only their effects were. So, strictly speaking, the quantum jumps couldn’t possibly be a part of his theory—plain and simple!

But then, Bohr in his philosophic enthusiasm didn’t stop just there. He went even further—much further. He fully deployed the powers of his explicit reasoning as well as the weight of his seniority in prohibiting the young physicists from even thinking of—let alone ideating or offering—any mechanism for such quantum jumps.

In other words, Bohr took special efforts to keep the young quantum enthusiasts absolutely and in principle clueless, as far as his quantum jumps were concerned.

Bohr’s theory, in a sense, was in line with the strictest demands of the philosophy of empiricism. Here is how Bohr’s application of this philosophy went:

1. This electron—it can be measured!—at this energy level, now!
2. [May be] The same electron, but this energy level, now!
3. This energy difference, this frequency. Measured! [Thank you experimental spectroscopists; hats off to you, for, you leave Bohr alone!!]
4. OK. Now, put the above three into a cohesive “theory.” And, BTW, don’t you ever even try to think about anything else!!

Continuing just a bit on the same lines, Bohr sure would have said (quoting Peikoff’s explanation of the philosophy of empiricism):

1. [Looking at a tomato] We can only say this much in theory: “This, now, tomato!”
2. Making a leeway for the most ambitious ones of the ilk: “This *red* tomato!!”

Going by his explicit philosophic convictions, it must have been a height of “speculation” for Bohr to mumble something—anything—about a thing like “orbit.” After all, even by just mentioning a word like “orbit,” Bohr was being absolutely philosophically inconsistent here. Dear reader, observe that the orbit itself never at all was an observable!

Bohr must have in his conscience convulsed at this fact; his own philosophy couldn’t possibly have, strictly speaking, permitted him to accommodate into his theory a non-measurable feature of a non-measurable entity—such as his orbits of his electrons. Only the allure of outwardly producing predictions that matched with the experiment might have quietened his conscience—and that too, temporarily. At least until he got a new stone-building housing an Institute for himself and/or a Physics Nobel, that is.

Possible. With Herr Herr Herr Doktor Doktor Doktor Professor Professors, anything is possible.

It is often remarked that the one curious feature of the Bohr theory was the fact that the stability of the electronic orbits was postulated in it, not explained.

That is, not explained in reference to any known physical principle. The analogy to the solar system indeed was just that: an analogy. It was not a reference to an established physical principle.

However, the basically marvelous feature of the Bohr theory was not that the orbits were stable (in violation of the known laws of electrodynamics). It was: there at all were any orbits in it, even if no experiment had ever given any evidence for the continuously or discontinuously subsequent positions electrons within an atom or of their motions.

So much for originator of the cult of sticking only to the “observables.”

What Sommerfeld did was to add footnotes to Bohr’s work.

Sommerfeld did this work admirably well.

However, what this instance in the history of physics clearly demonstrates is yet another principle from the epistemology of physics: how a man of otherwise enormous mathematical abilities and training (and an academically influential position, I might add), but having evidently no remarkable capacity for a very novel, breakthrough kind of conceptual thinking, just cannot but fall short of making any lasting contributions to physics.

“Math” by itself simply isn’t enough for physics.

What came to be known as the old quantum theory, thus, faced an impasse.

Under Bohr’s (and philosophers’) loving tutorship, the situation continued for a long time—for more than a decade!

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PS: Only typos and animals of the similar ilk remain to be corrected.

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:

(a) deterministic
(b) non-local
(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.

[E&OE]