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Quantum Theory and Causation
Foreword by David Quinn
It is a common perception that quantum mechanics has conclusively demonstrated events happen without cause in the sub-atomic realm. It is a view regularly expressed by followers of science, or more accurately, by those who like to read popular books on science. After reading an article in Wikipedia which suggested this was actually a myth (see below), I thought it would be interesting to travel around some physics forums and ask serious observers of quantum theory what they think.
This occurred over a few days in March, 2004.
The results were very interesting. Almost no one agreed with the idea that events happen without cause in the quantum realm. They all believed this constituted a gross misunderstanding of quantum theory. They affirmed the more sensible view that while things are "indeterministic" in the quantum realms in terms of our ability to predict events, the quantum realm is nevertheless fully causal.
The first post I sent into these forums (Science Forum and sci.physics.particle) was this:
Quote:
From: David Quinn
Hello all,
I was wondering if an expert in quantum physics can clarify a couple of things for me.
I read this in the Wikipedia:--
Interpretation of Quantum Mechanics:
Quantum mechanics is a physical theory which is extremely non-intuitive. The equations have been very successful in predicting experimental results, but there have been a wide range of interpretations of what those equations mean.
The need for a large range of interpretations of quantum mechanics becomes clearer once it is mathematically demonstrated that no quantum theory can have all of the properties one would like quantum mechanics to have.
One intuitively would like a theory of quantum mechanics
- that is complete and not requiring any outside theory
- that is local in that the events at one point are only effected by nearby areas
- that is deterministic which is that given one set of circumstances, there is only one possible outcome
- that has no hidden variables
- that predicts only one universe
However, Bell's theorem appears to prevent quantum mechanics from having all of these properties. Which property is removed results in different interpretations of quantum mechanics.--
Now this seems to suggest that are at least five different interpretations of quantum mechanics, each one the result of eliminating one of the five properties listed above.
My questions:
(a) Do any of these interpretations conflict with what is physically observed in the quantum realm?
(b) Do any of these interpretations hinder the practical application of the theory and its equations?
In every forum, the standard response to both questions was "no". It doesn't matter what interpretation you adopt from the five listed above, the practical application of quantum theory remains unaffected. Indeed, the majority of respondents thought that quantum mechanics shouldn't be interpreted at all, that physicists should just "shut up and calculate".
I then asked them this:
Quote:
If that is the case, then why has the "Copenhagan interpretation" - which removes the 3rd property listed above - gained currency in the scientific and non-scientific communities?
This is particularly strange, given that the removal of the 1st property (that QM is complete and not requiring any outside theory) would seem the most reasonable thing to do. The fact that physicists have chosen to reject determinism in the quantum realm, instead of accepting that QM is an incomplete theory, seems incomprehensible to me.
Can you explain this?
Here are some of the responses from a couple of the more intelligent forums:
***
The Copenhagen interpretation is a kind of pretense that physicists had adopted so they can stop calculating useful things for a while and discuss it with people that aren't interested in the math. The Copenhagen interpretation was an early effort, I think it was the first attempt to interpret the theory, and you'll find a lot of dissatisfaction with it. The whole "collapse of the wave-function" thing and the role of the conscious observer, in my opinion, comes from a misguided effort to consider an observer to not be a quantum system.
Gregory L. Hanson (Science Forum)
***
The interpretations are attempts to express QM, to some degree, in terms of things with which we are familiar. Some people find that this helps them get a feel for the subject. However, when physicists
were polled on which interpretation they preferred, the 'shut-up-and-calculate' interpretation came top.
In other words the results of QM are so weird that attempts to express them in terms of everyday experience fail, or at least lead to bizarre situations. Of course these are always useful for adding dramatic appeal to the subject.
Martin Hogbin (Science Forum)
***
If all you want to do is use QM to solve a particular problem then you do the "shut up and calculate" thing. But that is not very helpful if you want to have science progress and see if there is something more fundamental than QM. The mind is a wonderful thing in that we can imagine all kinds of scenarios. And imaginative scenarios based on past history can be very powerful. A basic mindset right now is that of "turtles all the way down". If we find something more fundamental to QM then what is more fundamental to that? So why not just stop somewhere and call it quits since we can calculate many useful things. Quantum field theory is that spot for right now. But eventually our knowledge will progress to the point of realizing something more fundamental than QM. It is just a matter of time
really.
FrediFizzx (Science Forum)
***
I question the "need" for interpretations. It is not a duty of a theory to be "interpretable". Its only function is to be able to produce reliably correct answers to questions put to it. Besides.what does it mean to "interpret" a theory? To crudely reword it in terms of what the state of our intuition requires at the moment? Why bother, apart from the intellectual pleasure it gives some to venture into metaphysics.
Franz Heymann (Science Forum)
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If you could lay hand on a copy of a book by Franco Selleri that was prefaced by Karl Popper, you would get a rather clean explanation about this.
I suppose it has been translated to English, but my own copy is in French and it's the only title I can refer you to:
"Le grand débat de la théorie quantique", by Franco Selleri.
As you may gather, the possible English title could very well turn out to be "The Great Debate of Quantum Theory", but who knows!
Of course there are as many opinions on this as there are authors, as I observed as I went through quite a few of them, but Selleri's account seems quite objective and thorough.
Although there is talk and rationalization about many interpretations, they all boil down to either causalist or non-causalist, all non-causalists on last analysis turning out to be plain and simple followers of the Copenhagen school of thought.
What seems to have happened is this:
The most famous causalists (Einstein, Planck, Shrödinger, de Broglie, et al.) believed that fundamental objective reality, that underlies the theories that we elaborate about it, is not chaotic and obeys logical laws that can be identified and understood, while the Copenhagen-Götingen school of thought headed by Bohr, Eisenberg, et al. believed that there exists no fundamental reality beyond what Quantum Mechanics can describe.
A strange turn of history seems to be responsible for the debate to eventually die down, even before Einstein passed away, for lack of fighters on the causalist side. Arnold Sommerfeld for example, a major original proponent of the copenhagist view, was so viscerally opposed to it, that he apparently taught for an extended period of his career only the copenhagist view to group after group of students.
He was thus almost single handedly, at the origin of a complete generation of eminent professors who had apparently only superficially glanced at the other side of the coin and who concluded, with no reason other than the conviction of their eminent teacher that the idea was worthless, which translated into the causalists views and theories to progressively cease being referred to in textbooks and thus came to not even be minimally explained to students of the following generations.
The non-causalist ball had started rolling and is still in full swing.
Today, physicists are unknowingly trained from the start as Copenhagists in almost all colleges and universities without really being made aware of the fact, and if they never personally question their own
philosophical orientation with respect to reality, naturally tend to not even become aware that they are.
No reference book expounds anymore on the causalist viewpoint beyond a few well known traditional showcases, like the EPR experiment for example, which have simply become traditional causalists scapegoats to be flogged in public, presumably because it simply is not possible to completely disregard the major contribution of causalist scientists.
In fact, so little consideration has come to be afforded to causalists' opinions at the international level, that despite his immense stature as the last remaining major architect of modern physics, Louis de Broglie's, last book seems not to even have been translated to English, although he possibly was the keenest mind on electromagnetism of the 20th century!
From my analysis, the wide acceptance of the non-causalist option finds its roots in the Copenhagist philosophy which involves the acceptance of irrational premises as an integral part of Quantum Mechanics, which in turn seems to make it easier for the promoters to more readily accept other irrational explanations to rationalize every observation that does not logically fit accepted theories, which seems to satisfy them sufficiently for them to consider searching for other explanations a waste of time.
In other words, indeterminism simply is the easy way out.Doesn't everybody love magic? :-]
Regards
André Michaud, sci.physics.particle
***
I believe that is not the only reason. The "underlying" reason is that in doctoral programs excellence in philosophy has been entirely and without second thought divorced from the requirements to obtain a PhD degree. Today, we educate science automatons, not scientists and for that unphilosophical unconscious drones of today's "big and glorious science" are sufficient.
Otherwise, a moderate physicist who had had a fleeting glance of philosophy of mind would have known that statistical behaviour might not be primarily caused by a fundamental existence of randomness. Fortunately, the school of Leibniz has been revived and through works of digital physicists we are seeing a formidable alternative to the Copenhagen interpretation!
Regards,
Eray, sci.physics.particle
***
As I recall the Copenhagen interpretation evolved out of Bohr's desire to present a unified interpretation to the world, and Heisenberg's regard for his old teacher, together with a few bits from other contributors. I think it was most accurately described in sci.physics as a sort of Danish Smorgasbord, from which you take the bits you like.
Bohr's central contribution seems to have been the notion of complementarity, the idea that something can be both wave and particle, and that we only seen a part of its nature in any type of experiment.
This idea has itself been taken to mean different things by different people but is widely subscribed, particularly in , and is probably at the centre of most of the "crackpot" arguments about quantum mechanics on sci.physics. From my general reading I have become convinced that Heisenberg did not subscribe to complementarity, but I regret that I have not read any of Heisenberg's own writings, and am about to correct this by getting one of his books from Amazon. From what I do know of his discussion of uncertainty, I think it was pretty on the ball, and lead into the Dirac interpretation and indeed to my own understanding of uncertainty - namely that the (crisp) position of an object cannot be defined or discussed except relative to other matter, and since the (crisp) position of other matter equally cannot be defined or discussed except relative to still other matter, any definition of position in classical (two valued) logic is bound to degenerate into recursive argument.
If Heisenberg was not 100% clear, either in his own mind or to his readers about this discussion, I think the reason is that he was struggling with these ideas for the first time in history. Moreover many valued logic was in its infancy, and there was no way that Heisenberg could distinguish crisp from unclear statements, and this stuff is extremely difficult to talk about if one is restricted to making statements in crisp logic (classical or two valued logic, in which every statement is either absolutely true or absolutely false).
Regards
Charles Francis, sci.physics.particle
***
DQ: I've been repeatedly told, by scientists and non-scientists alike, that quantum physics has proven that things arise without cause in the quantum realm. Now I find that this is not true at all. It is just one particular interpretation that has been adopted by the physics community at the expense of rejecting the commonsense view that QM is an incomplete theory. I find this extraordinary.
Franz Heymann: That is horse dung. Whoever told you that did not know his arse from his elbow. QM is fully causal, but not fully deterministic.
(Science Forum)
***
I think the main reason that the Copenhagen interpretation has been the preferred one is that it was the first, and most people will stubbornly cling to the earliest version of a theory, especially when later versions supply no additional working predictions, and so maintain the same old physical content.
I also think that the notion of non-determinism in QM has been overstated. So you can't predict with certainty how a system will evolve in phase space, but we should not be too concerned about that.
The quantum realm has its own set of rules and we have to live with them. Certainly, the wave function evolves in a deterministic way in its own space. If you look at it that way, I think you can take a lot of the mystery out of the theory . . . . .
Andr Michaud, sci.physics.particle
***
All through history, self appointed "judges" of political correctness of potential discoveries (today they name themselves "peer review panels") have granted themselves the right to accept or refuse publication of potentially promising papers based strictly on their own understanding of the subjects. Understanding that can certainly be questioned if the premises of the papers proposed were currently unpopular.
As far back as the beginning of the 20th century, Poincaré himself considered that they were not wrong in doing so and that they ran no risk of smothering any serious discovery, for, as he explains: If you had asked academics [regarding this], they would have answered: "We have compared the probability that an unknown scientist had found what we have been looking for in vain for so long, to that of there
being one more fool on the Earth, the second would have appeared greater".
Paradoxically, to explain the reluctance of academics to consider any new idea and their recurring belief that all has already been discovered, Poincaré wrote in the same book: "Each of us carries within himself his own conception of the world, which he cannot so easily dismiss"; which, of course, is a psychological problem that affects all humans and has nothing whatsoever to do with science.
After having invested years of their life becomimg comfortable with Minkowski's 4-dimensional space geometry, Special Relativity, General Relativity, Quantum Mechanics and QED, fledgling physicists then tend subscribe to them for good. They are afterwards very unlikely to ever risk again losing intellectual footing by reconsidering the whole structure, including the premises.
Unfortunately, despite the importance of the remaining problems, orthodox theories always seem too satisfactory, and life too short, for them to consider investing even part of their precious remaining time and required effort in looking for potentially more appropriate alternatives at the fundamental level.
To them, reconsidering fundamental space geometry, for example, or trying to explore where would lead the idea that electron spin could be due to pulsating instead of spinning, seem like useless extreme mindbenders, or quite wrongly feel inadequate to deal with such re-questioning, even if it could potentially cause our theories to evolve towards solving the remaining problems.
Peer pressure to conform to the norm is also a major extinguisher of personal initiatives.
André Michaud, sci.physics.particle
***
Contrary to the common perception quantum mechanics becomes intuitive when you grasp the difference between a fluid-like quantity and a quantized quantity.
Be that your wife/girlfriend/concubine acts very different to your idea of 'the women'. The fact that you may or may not at a certain time is also expressed by a probability. Company owners /CEOs who consider their mass of workers as fluid are overlooking that few key persons at the right places decide over success or failure of a project.
Rene Tschaggelar (Science Forum)
***
If you look and dig long enough, you will eventually come to the conclusion that under the thick cloak of flashy mathematics that fill so much space in so many physics papers and books, the real stuff is not increasing in complexity, and the complexity of the math cover often simply is an indication of the circuitous way that the author used to get at some minute side detail of the main subject.
Andr Michaud (sci.physics.particle)
***
FreddiFizz: If all you want to do is use QM to solve a particular problem then you do the "shut up and calculate" thing. But that is not very helpful if you want to have science progress and see if there is something more fundamental than QM. The mind is a wonderful thing in that we can imagine all kinds of scenarios. And imaginative scenarios based on past history can be very powerful. A basic mindset right now is that of "turtles all the way down". If we find something more fundamental to QM then what is more fundamental to that? So why not just stop somewhere and call it quits since we can calculate many useful things. Quantum field theory is that spot for right now. But eventually our knowledge will progress to the point of realizing something more fundamental than QM. It is just a matter of time really.
DQ: You seem to be saying that the "Copenhagen interpretation" is a kind of pretense that physicists have adopted so that they can stop for awhile and calculate many useful things. Is that correct?
If so, it raises another couple of interesting questions:
- Why do physicists need to create a pretence in order to "stop for a while"? Why can't they just stop for a while (in the knowledge that QM is a transient, incomplete theory) and get on with their calculations? Why all this extral bullshit?
Franz Heymann: Physicists generally speaking *don't* concern themselves with what you (rightly) call this extra bullshit. They get on with their experiments and their calculations. It is the folk who are concerned with the philosophy of science who bother with "interpretations". In that respect they do not indulge in physics, but in metaphysics.
DQ: - And secondly, if they had known all along that the "Copenhagan interpretation" is merely a pretense, a kind of metaphysical tool of convenience, then why has indeterminism been presented to the general public for the past eight decades as though it were a firm philosophic truth?
FH: That is a good question. Probably because pop science writers have a good nose for what makes exciting reading, and because religious proselytisers rather fancy the idea that there is a god somewhere who pulls strings in the background and manipulates the uncertainties.
DQ: Why do I feel like I've been lied to by the physics community?
FH: You have been lied to by the *metaphysics* community. You would be quite safe to disregard all they have to say.
The Copenhagen interpretation is not physics. Physics would progress in its merry way whether the Copenhagen interpretation is true or false. The interpretation of a theory is itself a set of philosophical statements about a theory. As such it is *metaphysics*.
(Science Forum)
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Science Forum
sci.physics.particle
When I posted these comments on Genius Forum in March, 2004, I was asked for my reaction:
Question: Interesting David. What do you suggest this data which you have gathered shows us?
David Quinn: At the very least, it shows us that the "proof" of non-causality in the quantum realm, as preached by many on this forum, is groundless, as it is based on an irrational interpretation of QM.
Secondly, it shows us that most physicists don't care if they are being irrational in a philosophic sense. When faced with a choice between rejecting the concept of causality or rejecting the idea that QM is a complete theory, the mainstream physics community has, for decades, chosen the former - which, to my mind, is an action so incredible that it is beyond belief. I can only put it down to the fact that physicists simply do not care whether they are being rational or irrational in a larger sense, beyond their work.
Thirdly, it shows us that we cannot trust scientists in anything they say about their work. We can trust them to do the experiments and the maths, but as soon as they step outside of this realm and begin to philosophically interpret their work, we should be extremely wary.--
Question: You write as if physicists get some advantage from insisting the particles arise uncaused. What possible advantage, other than the chance to make fools of themselves eventually?
David Quinn: It's due to a number of factors:
One is that scientists are notoriously prone to being carried away with their latest research, and they are always bursting to hype it to the max. Barely a week goes by without some scientist loudly proclaiming a recent discovery or theory, no matter how trivial or obscure, to be the most important breakthrough in a century, one that will revolutionize the way we view ourselves, blah, blah, blah. It's quite embarassing the way they carry on. Like children, they lose all sense of perspective.
Another factor is that most scientists believe that philosophy is a dead subject, and thus they don't care what sort of philosophical mess they make. They can come up with any old crazy metaphysical viewpoint to support their latest theorizing and it doesn't trouble them in the least that it may be irrational or untruthful. Indeed, the wackier it is, the better. For it demonstrates, to their own eyes at least, that science is wonderfully exciting and glamorous and not at all like the dreary old lessons that we had to endure at school.
Another factor is that scientists are alway looking for grants to fund their research, a tiresome process made significantly easier if you can bedazzle politicians and business folk with wild, sexy stories about quantum theory and cosmology and the like. Scientists are competing with many other organizations for the entertainment dollar and so it is in their interests to keep sprucing science up and have it showing a lot of cleavage and leg.
Finally, despite the nature of their work, most scientists are very similar to the rest of the human race - they are average egotistical people with plenty of false thoughts and emotional attachments swirling around in their brains. As such, they neither see the significance of the concept of causality, nor the damage which their own foolish proclamations have done to the human race's spiritual relationship to it.