Is the Copenhagen Interpretation of Quantum Physics Rational?

[babelbusters]

Hello,

First post.

I have been doing a lot of reading in quantum physics, and I am really riled up about some things. First off, I get the feeling when reading those who defend the Copenhagen Interpretation (CI) that they are earnestly trying to put one over on me.

I'm a rational guy. I believe scientists should hold on to rationality. To embrace irrationalism is the end of science.

When CI people say that the spin of a particle is non-existent UNTIL it is detected, how can this be proven? I don't know of ANY rational test that can be performed that could prove that spin is non-existent until it is detected. You cannot know the spin of a particle until you detect it. The spin is there to be detected, but it is not known until it is detected.

I just listened to a lecture on EPR, and how tests were done in the 1990's that showed that when a non-spinning radioactive particle decays into two particles that go off into their own separate paths far far away from each other, that neither particle has any spin UNTIL one is detected, and when that detection determines the spin of one particular, supposedly proven is that the other particle far far away all of the sudden responds by spinning in the opposite direction.

I'm trying to figure out how an experiment could actually prove this. My view is that the particle decays into two particles that have opposite spins from the get go. When you detect the spin of one, you can go far far away and detect the opposite spin of the other because that is the direction of the spin determined from the get go!

Also, the double slit experiment is predicated on the fact that real existent waves travel through both slits while the particle only goes through one. The CI interpretation speaks of these obviously real waves as non-real "probability waves."

What appears to me as the rational interpretation as to what is going on is that a 'particle' is particular localization within the broader underlying non-local wave that seems to pervade all of reality. Underlying all of reality is some existent "stuff" that acts wave-like. It is all pervading and non-localized. A particle is where some of this "stuff" is in a localized form while still organically related to the all pervading wave-like "stuff." When you forcefully propel this particle at the double slits, it is not going to travel all by itself but ride on and with the wave-like "stuff". The movement of localized "stuff" (particles) is never apart from the causal movement of the nonlocalized "stuff" it is organically connected to.

For instance, consider a body of water. The water is non-local stuff. Then, take a few ounces of this stuff and freeze it into solid localized "stuff." Then propel this "stuff" through the water, and you have your particle and wave. The ice moves through the water, but it travels with and is guided by the waves it creates.

This is sort of what Bohm was saying with his pilot waves, right?

All feedback to my thoughts appreciated.

Thanks,
Babelbusters

 

[jtbell]

When CI people say that the spin of a particle is non-existent UNTIL it is detected, how can this be proven?

How can it be proven that the spin DOES exist (with a specific value as opposed to a superposition) without observing it?

 

[babelbusters]

How can it be proven that the spin DOES exist (with a specific value as opposed to a superposition) without observing it?

Well, if you detect something with a spin, you would simply use reason to then assume that the spin was there already (unless something about your detection apparatus physically caused the spin. But, if no causal link is known, no necessity to assume it.)

I just get the sense that a bunch of this Copenhagen stuff is unwarranted and illogical (esp. from a philosophical point of view), and something I read tonight seemed to shed some light on this. I read a statement that said that Niels Bohr and the CI came out of logical positivism. That's why to the Copenhagen people, the question of whether a particle has position or momentum PRIOR to being measured is a MEANINGLESS thing to ask.

It's not as though these people have concrete experimental proof that a particle prior to measurement is ontologically indeterminate. They CHOOSE to believe it is indeterminate because of the impossibility to measure both position and momentum simultaneously, and the gist of logical positivism is that whatever is not experimentally verifiable simply does not exist for all sense and purposes and it is wholly meaningless to even speak of it.

So, what's going on here is that because Bohr and Heisenberg could not experiementally measure something, their logical positivism inclined them to take the view that the thing is ontologically and really indeterminate prior to observation/detection/measurement.

But that is simply allowing oneself to be shortchanged by a logically false philosophy like logical positivism.

And it leaves "us" scratching our heads trying to figure out why these people came to these irrational conclusions. But if indeed they were guided by logical positivism, I can now better understand the "why."

 

[Hurkyl]

I'm trying to figure out how an experiment could actually prove this.

I do say, you would probably get a better reaction if you just said this -- your post makes it look like you have already assumed it cannot be proven, and may even be unwilling to listen to how it could be proven.


The crucial point is correlation between spins measured about different axes. If one detector is rotated, for example, 10 degrees from the other one, then the two detectors will give opposite readings most of the time, but not all of the time.

Then you make these hypotheses (I think this is enough):
(1) The spin about any axis is already determined when the particle pair is created¹
(2) The configuration of your detectors do not influence the creation of the particle pair
(3) the configuration of one detector does not influence the measurement at the other detector
(4) All of your trials are independent
(Bell's theorem, incidentally, assumes even less than this!)

Then, you can rigorously prove a certain inequality involving the observed correlations between different detector settings.

Quantum mechanics predicts that inequality can be violated. Experimental evidence agrees with QM's prediction.

 

[Hurkyl]

Well, if you detect something with a spin, you would simply use reason to then assume that the spin was there already

Please demonstrate.

 

[Demystifier]

Babelbusters, do you prefer some other interpretation instead of Copenhagen? Are you familiar with the Bohmian interpretation? If not, see
https://www.physicsforums.com/showpost.php?p=1366355&postcount=33
From your reasoning, I conclude that you might like it.

 

[babelbusters]

Babelbusters, do you prefer some other interpretation instead of Copenhagen? Are you familiar with the Bohmian interpretation? If not, see
https://www.physicsforums.com/showpost.php?p=1366355&postcount=33
From your reasoning, I conclude that you might like it.

Thanks for the links. I read a couple of things that portrayed Bohm as believing that the interference pattern in the double slit test was caused by actually existing waves along with the particle, rather than the notion that the pattern is the result of some "probability wave" that doesn't have any ontological status apart from the act of human observation collapsing it into a particle. Since then I have been trying to find links, so your links are very welcome.

What I find interesting as well is that it seems like many look at Copenhagen as opening the door to mysticism, yet Bohm who had an opposing view himself was a mystic. This seems to show that whatever one's view on the quantum reality, it can provoke mystical behavior. :-)

 

[babelbusters]

I do say, you would probably get a better reaction if you just said this -- your post makes it look like you have already assumed it cannot be proven, and may even be unwilling to listen to how it could be proven.

No, that's not quite true. I have been searching for books and articles on the web that would explain to me, in a way that I can get my rational mind around, how the CI can be true. I really don't have any prejudice in my mind against it, other than the fact that it's utter irrationalism irritates me. If I can be helped to get my mind around it, and if I can see clearly that experimentation has clearly proven it, I'd have no problem accepting it.

But, the books I have been reading and lectures listening too, I get the sense that a lot of logical errors are being made when interpreting the results of experiements. Reason and logic is being completely let go.

 

[Fra]

No offense to my former teachers, there were great but from what I remember my QM courses, they simply weren't designed to motivate QM in a general setting of scientific methods. Introductory courses and books are seemingly design to teach the student a formalism that is known to be very useful. The motivation were often historical overviews and the arguments at the level that "A predicts B, B is empirically supported, thus A makes sense". But to analyze this further, you'd probably have to look beyond QM.

If you want a deeper understanding of the model in a more general setting, beyond it's straight application, it might be that you have to find it on our own.

Standard courses provides standard answers to standard questions. If you settle with them, you're done. If not, the chance is that you're on your own.

IMO, this can't be sensibly disucssed without falling back to basic scientific methods and it's philosophies, that's where some of these issues start.

/Fredrik

 

[Demystifier]

What I find interesting as well is that it seems like many look at Copenhagen as opening the door to mysticism, yet Bohm who had an opposing view himself was a mystic. This seems to show that whatever one's view on the quantum reality, it can provoke mystical behavior. :-)

I would say that Bohm became mystical only much later, not when he proposed his "Bohmian" interpretation.

 

[Schrodinger's Dog]

Don't you wish we could ask Niels Bohr, what you want is to delve into the history of Copenhagen. If you want to resolve why exactly it is the way it is.

This website I personally found very helpful and it clears up a few questions about exactly what it means.

http://plato.stanford.edu/entries/qm-copenhagen/

Bohrs influences.

Earlier generations of philosophers have often accused the Copenhagen interpretation of being subjectivistic or positivistic. Today anyone who has studied Bohr's essays carefully agrees that his view is neither. There are, as many have noticed, both typically realist as well as antirealist elements involved in it, and it has affinities to Kant or neo-Kantianism.

Bohr thought of the atom as real. Atoms are neither heuristic nor logical constructions. A couple of times he emphasized this directly using arguments from experiments in a very similar way to Ian Hacking and Nancy Cartwright much later. What he did not believe was that the quantum mechanical formalism was true in the sense that it gave us a literal (‘pictorial’) rather than a symbolic representation of the quantum world. It makes much sense to characterize Bohr in modern terms as an entity realist who opposes theory realism (Folse 1987). It is because of the imaginary quantities in quantum mechanics (where the commutation rule for canonically conjugate variable, p and q, introduces Planck's constant into the formalism by pq - qp = ih/2π) that quantum mechanics does not give us a ‘pictorial’ representation of the world. Neither does the theory of relativity, Bohr argued, provide us with a literal representation, since the velocity of light is introduced with a factor of i in the definition of the fourth coordinate in a four-dimensional manifold (CC, p. 86 and p. 105). Instead these theories can only be used symbolically to predict observations under well-defined conditions. Thus Bohr was an antirealist or an instrumentalist when it comes to theories.

Much of Kant's philosophy can be seen as an attempt to provide satisfactory philosophical grounds for the objective basis of Newton's mechanics against Humean scepticism. Kant showed that classical mechanics is in accordance with the transcendental conditions for objective knowledge. Kant's philosophy undoubtedly influenced Bohr in various ways as many scholars in recent years have noticed (Hooker 1972; Folse 1985; Honnor 1987; Faye 1991; Kaiser 1992; and Chevalley 1994). Bohr was definitely neither a subjectivist nor a positivist philosopher, as Karl Popper (1967) and Mario Bunge (1967) have claimed. He explicitly rejected the idea that the experimental outcome is due to the observer. As he said: “It is certainly not possible for the observer to influence the events which may appear under the conditions he has arranged” (APHK, p.51). Not unlike Kant, Bohr thought that we could have objective knowledge only in case we can distinguish between the experiential subject and the experienced object. It is a precondition for the knowledge of a phenomenon as being something distinct from the sensorial subject, that we can refer to it as an object without involving the subject's experience of the object. In order to separate the object from the subject itself, the experiential subject must be able to distinguish between the form and the content of his or her experiences. This is possible only if the subject uses causal and spatial-temporal concepts for describing the sensorial content, placing phenomena in causal connection in space and time, since it is the causal space-time description of our perceptions that constitutes the criterion of reality for them. Bohr therefore believed that what gives us the possibility of talking about an object and an objectively existing reality is the application of those necessary concepts, and that the physical equivalents of “space,” “time,” “causation,” and “continuity” were the concepts “position,” “time,” “momentum,” and “energy,” which he referred to as the classical concepts. He also believed that the above basic concepts exist already as preconditions of unambiguous and meaningful communication, built in as rules of our ordinary language. So, in Bohr's opinion the conditions for an objective description of nature given by the concepts of classical physics were merely a refinement of the preconditions of human knowledge.

Who said philosophy was useless eh ?

A brief excerpt:-

Bohr's more mature view, i.e., his view after the EPR paper, on complementarity and the interpretation of quantum mechanics may be summarized in the following points:

1. The interpretation of a physical theory has to rely on an experimental practice.
2. The experimental practice presupposes a certain pre-scientific practice of description, which establishes the norm for experimental measurement apparatus, and consequently what counts as scientific experience.
3. Our pre-scientific practice of understanding our environment is an adaptation to the sense experience of separation, orientation, identification and reidentification over time of physical objects.
4. This pre-scientific experience is grasped in terms of common categories like thing's position and change of position, duration and change of duration, and the relation of cause and effect, terms and principles that are now parts of our common language.
5. These common categories yield the preconditions for objective knowledge, and any description of nature has to use these concepts to be objective.
6. The concepts of classical physics are merely exact specifications of the above categories.
7. The classical concepts—and not classical physics itself—are therefore necessary in any description of physical experience in order to understand what we are doing and to be able to communicate our results to others, in particular in the description of quantum phenomena as they present themselves in experiments;
8. Planck's empirical discovery of the quantization of action requires a revision of the foundation for the use of classical concepts, because they are not all applicable at the same time. Their use is well defined only if they apply to experimental interactions in which the quantization of action can be regarded as negligible.
9. In experimental cases where the quantization of action plays a significant role, the application of a classical concept does not refer to independent properties of the object; rather the ascription of either kinematic or dynamic properties to the object as it exists independently of a specific experimental interaction is ill-defined.
10. The quantization of action demands a limitation of the use of classical concepts so that these concepts apply only to a phenomenon, which Bohr understood as the macroscopic manifestation of a measurement on the object, i.e. the uncontrollable interaction between the object and the apparatus.
11. The quantum mechanical description of the object differs from the classical description of the measuring apparatus, and this requires that the object and the measuring device should be separated in the description, but the line of separation is not the one between macroscopic instruments and microscopic objects. It has been argued in detail (Howard 1994) that Bohr pointed out that parts of the measuring device may sometimes be treated as parts of the object in the quantum mechanical description.
12. The quantum mechanical formalism does not provide physicists with a ‘pictorial’ representation: the ψ-function does not, as Schrödinger had hoped, represent a new kind of reality. Instead, as Born suggested, the square of the absolute value of the ψ-function expresses a probability amplitude for the outcome of a measurement. Due to the fact that the wave equation involves an imaginary quantity this equation can have only a symbolic character, but the formalism may be used to predict the outcome of a measurement that establishes the conditions under which concepts like position, momentum, time and energy apply to the phenomena.
13. The ascription of these classical concepts to the phenomena of measurements rely on the experimental context of the phenomena, so that the entire setup provides us with the defining conditions for the application of kinematic and dynamic concepts in the domain of quantum physics.
14. Such phenomena are complementary in the sense that their manifestations depend on mutually exclusive measurements, but that the information gained through these various experiments exhausts all possible objective knowledge of the object.

 

[Anonym]

Hi, Dog! Glad to meet you here again.

Who said philosophy was useless eh ?

I say. But I did not read your essay.

Regards, Dany.

 

[Schrodinger's Dog]

Hi, Dog! Glad to meet you here again.
I say. But I did not read your essay.

Regards, Dany.

Hi thanks, yes need some maths advice and I have got back on track with the coursework so I have some free time

Another advocate of the Philosophy section should not increase your post count camp I see

I didn't actually expect people to read it except maybe the op but the infos their if they want to take a look.

 

[Anonym]

need some maths advice

Will be my pleasure if I may help

Regards, Dany.