Quantum Confusion: Philosophical Assumptions Behind Mechanics

[wittgenstein]

I am confused by the philosophical assumptions behind Quantum Mechanics. Are physicists logical positivists? The reason I ask that is because it seems that they believe that if something in intrinsically unknowable it does not exist as a truthful proposition. For example before the collapse what is happening? Suppose, I have an impregnable box ( even logically necessarily impregnable) . I do not know if there is a brick ( particle) or water ( wave) inside. Does that mean that one possibility is not correct and the other is also not correct? I am totally confused! Please help!

 

[Dickfore]

I do not know if there is a brick ( particle) or water ( wave) inside.

WHAT? Do you know what bricks and water are made of?

 

[wittgenstein]

It's a metaphor.* My point ( in using a concrete metaphor) is to see what the philosophical assumptions behind QM are. For example, if one asks," suppose one is on a photon, what would the universe look like?" It would not have anything to do with the speculation to say that no one can ride a photon.
PS; Einstein pondered that absurd metaphor and it inspired Relativity.
* Yes, matter ( bricks and water) are composed of quantum . But that totally misses the point.

 

[geophysics10]

If I told you the philosophical assumptions of physics were intrinsically unknowable and provided a reasonable explanation why, would you continue to ask that question?

I'll give the usual answer and then go on to provide a helpful answer and point you in the right direction to form your own philosophical assumption of physics.

Physics does not delve into ideas that cannot be impirically evaluated and understood, so asking questions like

Q: "what would it be like to be a photon?", "whats outside of the observable universe?", "whats is smaller than the smallest observable parts of the universe?" are asking for nothing but a speculative answer.
A: "Because of time contraction, you would experience nothing and feel as if you had never existed", "pixies and pink dragons", "it's turtles all the way down"

Pondering the absurd can be a useful tool of imagination, but it not part of the scientific process. It's inspiration for an idea.

Your Schrodinger's box analogy is way off. The Schrodinger's box example is a tool used to explain the mathematical process of determining the probability of some quantum state. It is not some magical property of the universe which turns every sealed box and crate into a wave-particle limbo machine. Uncertainty arises from the physical contraints imposed by the methods used to probe properties of the smallest pieces of matter we know. To probe the small, we must prod it (using light, electrons, etc), and know approximately where the particle is. So we can either not look at it (box is closed) or look at it and not know it will be in the future (open box).

 

[Fredrik]

The most useful way to think of QM is not as a description of reality, but as a set of rules that tells us how to calculate probabilities of possible results of experiments.

If "QM" refers to the theory defined by the standard Hilbert space axioms, then there's nothing in QM that tells us unambiguously what the system "is doing" at times between state preparation and measurement.

The "interpretations of QM" are attempts to turn QM into a description of reality. The most straightforward way to do that is to simply add new axioms on top of the ones that define QM, in order to give us a picture of what "actually happens" without changing the theory's predictions. The fact that the predictions are unchanged means that these interpretations are unfalsifiable, so they are strictly speaking not a part of science.

Another approach, which is also considered to be a part of "interpretations of QM", is to find another theory, that makes the same predictions but is defined by a different set of axioms, and see if it suggests a different picture of what "actually happens". A good example is de Broglie-Bohm pilot wave theory.

 

[DevilsAvocado]

I am confused ... Please help!

Hi Wittgenstein! Not Ludwig I presume?

Fredrik’s & geophysics10’s explanations are excellent, but in case you didn’t get it, here’s my "version":

1) QM is without competition the most precise theory we have. Mathematically, it works perfect, period.

2) When trying to "translate" the mathematics of QM to human language, we run into different paradoxes. This has in turn created a set of http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics" . All interpretations uses exactly the same mathematics, but have different explanations for what’s "going on" in nature.

I think your "impregnable box" is a "confused" version of http://en.wikipedia.org/wiki/Schr%C3%B6dinger%27s_cat" . Erwin Schrödinger made this paradox – of a cat being both alive and dead at the same time – to show that something was wrong with the Copenhagen interpretation (Niels Bohr, Werner Heisenberg, et al.)

We know that a cat can’t be both alive and dead at the same time. It’s stupid, right?

Niels Bohr’s answer to the paradox was that we don’t need an observer (human) to make the collapse of the wave function (cat = alive/dead). A measurement alone, by a Geiger counter, is sufficient to collapse a quantum wave function before there is any conscious observation of the measurement.

Today, we know for sure that QM particles, like photons and electrons, indeed can be both "alive & dead", in a superposition of states before measurement. This is a fact.

Now, we all know that a cat is only "made of" trillions of QM particles, right? So what happens if we manage to "screen off" the macroscopic cat to the same level as the microscopic electron? Could the cat be in a "superposition of states" as well??

I think that many contemporary professors would say it could...

Personally, I have absolutely no idea. All I know is that it’s very interesting to learn and follow the development of QM. Who knows... some day it might be possible to go to the pet shop and buy a Norwegian Blue parrot that is both dead and alive!

 

[Dickfore]

Yes, matter ( bricks and water) are composed of quantum.

I don't even know what this means. Please enroll in a Modern Physics course before trying to 'uncover' the meaning of Quantum Mechanics.

 

[wittgenstein]

And you sir should take a course in civilized discourse and stop name calling like a 12 year old. Also, you cannot understand that sentence? Good grief! Its fairly basic. It's that fundamentally, when you break things down , everything is made of quantum particles and or waves.
See this site to refresh your education
http://hubpages.com/hub/Quantum-Physics---Sub-Atomic-particles
Anyway, enough with the troll. Thanks for everyone elses responses. Informative, but unfortunately disappointing. It seems to me that you are all saying that physics ( at least QM physics) is not about describing reality, its about experimental results. My impregnable box analogy was based on the Schrodinger's cat paradox. And yes, I understand the basic principle of Heisenberg's uncertainty , that the photon ( or whatever particle is used) disrupts the object and so that therefore one can only obtain position OR momentum. My point was that I wanted to see if physicists are actually claiming that before collapse the state is not a particle or a wave. From what you all have been saying it seems that it is one or the other, its just that we do not know.And it is impossible to know and so therefore the question ( what is it) is meaningless for a physicist. Like I said that's logical positivism.
PS Yes my computer name is in honor of the famous philosopher.

 

[wuliheron]

No, physicists are not necessarily logical positivists.

Physics doesn't make metaphysical assumptions anymore than my auto mechanic. So long as they both produce results everyone is happy and no one bothers to ask their auto mechanic what his metaphysical beliefs might be.

 

[wittgenstein]

That is what a logical positivist is. One that does not believe in metaphysics. One must remember that in this context "metaphysics" is not about anything new age or whatever. For example the belief that there is an objective reality separate from our personal subjective reality is a metaphysical belief. The opposite belief solipsism is also a metaphysical belief.
http://en.wikipedia.org/wiki/Solipsism

 

[wittgenstein]

One of Einstein's objections ( and the most pertinent one for this thread) to QM is that many of its advocates are logical positivists. Einstein did not just give equations that could be experimentally verified he provided a description ( in this sense Einstein was metaphysical , see above post). For example gravity is curved space-time.* The interesting thing is that in academic philosophy logical positivism is considered the only belief system that self destructed. It is based on the rejection of metaphysics ( an over all description of reality) and yet its basic premise is metaphysical!
* Einstein's genius was to approach a problem by visualizing a thought experiment. For example Relativity is the result of his visualizing and speculating about what the universe would look like if one rode a photon. Of course Einstein knew that that was impossible and to make that objection is nonsense.

 

[Dickfore]

And you sir should take a course in civilized discourse and stop name calling like a 12 year old. Also, you cannot understand that sentence? Good grief! Its fairly basic. It's that fundamentally, when you break things down , everything is made of quantum particles and or waves.

But, you said:

* Yes, matter ( bricks and water) are composed of quantum.

That word, by itself, has no meaning. Unless you make sense, you can't expect for people to have a meaningful discussion with you.

 

[wittgenstein]

So if I said,"Yes, matter ( bricks and water) are composed of atoms." You would find that sentence too confusing to understand?

 

[wittgenstein]

Seriously Dickfore I have no hatred for you. I just think that this petty path you seem to want us to take is boring. Let's talk about the subject, which I at least find more interesting than if one or the other of us is an idiot. I can speak for myself and say that I am pretty sure I am not an idiot. And I am willing to bet that you are not an idiot also.

 

[ZapperZ]

So if I said,"Yes, matter ( bricks and water) are composed of atoms." You would find that sentence too confusing to understand?

That too makes no sense.

An electron is a "matter". Yet, do you think it is "composed of atoms"?

I think you've made an oversimplification of physics, especially quantum mechanics. That is what is causing so much confusion with your question. You may not think it is confusing. But I can certainly tell you that if you have learned QM, your question borders on nonsensical. "everything is quantum" doesn't say anything meaningful, whether you like it or not.

Before you can make any kind of "philosophical" discussion of something in physics, it is imperative that you actually understands that part of physics that you want to talk about. This means it has to go beyond just a superficial understanding of what it is. If not, we get into something like this, where the starting point or the object of the discussion is lost due to confusing understanding of it.

Zz.

 

[Q_Goest]

I am confused by the philosophical assumptions behind Quantum Mechanics. Are physicists logical positivists? The reason I ask that is because it seems that they believe that if something in intrinsically unknowable it does not exist as a truthful proposition. For example before the collapse what is happening? Suppose, I have an impregnable box ( even logically necessarily impregnable) . I do not know if there is a brick ( particle) or water ( wave) inside. Does that mean that one possibility is not correct and the other is also not correct? I am totally confused! Please help!

Hi W. I’m no expert on logical positivism but it seems to me the intent is not that physical things have a single, specific existence (such as a single, specific position and momentum) or that events have a single, specific occurrence (such as Schrödinger’s cat being either alive or dead). From the definitions of logical positivism I'm looking it, it only says that physical things and events must be verifiable as being true, false or meaningless. So a photon passing through a diffraction grating for example, may not have a defined position, and that’s ok (as far as I can tell) from a logical positivist perspective. Logical positivism (as far as I can tell) only requires there be some ability to form a true/false meaning when we talk about such things. It doesn’t seem to require that we have an ability to form a definitive mental representation of something. Like I said, I'm no expert on it, but having read through a few articles, that's the impression I get.

Who knows... some day it might be possible to go to the pet shop and buy a Norwegian Blue parrot that is both dead and alive!

lol That's one of my favorite MP skits.

 

[wittgenstein]

"An electron is a "matter". Yet, do you think it is "composed of atoms"?"
ZapperZ
?? When did I say that? Good grief! If you have that much of a misunderstanding of what I said no wonder you have no clue as to what I said.
Here, I'll make it simple. If I said " All dogs are composed of cells" and then I said," all dogs are composed of atoms" I am not saying,or even implying," all atoms are composed of cells."

 

[Dickfore]

But you didn't say that, did you?

 

[wittgenstein]

Good grief! I cannot believe I am having this discussion. For some reason if I said ( here I'll make it even simpler) "Bricks are made of atoms." One of you would say "that is stupid , electrons are not composed of atoms."
How am I supposed to respond to that? It is so obviously a misunderstanding that any explanation would be like saying 1+1=2 and that would only be insulting.

 

[Dickfore]

Do you know what 'matter' means?

 

[wittgenstein]

"Logical positivism (as far as I can tell) only requires there be some ability to form a true/false meaning when we talk about such things."
Q_Goest
Therefore, it would say ( to go back to my impregnable box) that it is meaningless to say if there is a brick or water inside. In the sense that we are capable of visualizing a brick and water, one can say that if something is visually verifiable it meets the criteria of logical positivism.
I find logical positivism's stance extreme. It would actually say that one cannot make meaningful speculations. For example, it would be meaningless for me to say," there is probably matter at the center of Pluto."
----------------
I laid out two possibilities.
1. Before the collapse there is an actual reality ( particle or not), its just that we don't know what that reality is.
2. Before the collapse there is no reality regarding particle or not.

What did I get wrong? What other alternative is there? A or not A, show me something else. I did not take a side as to 1 or 2 . I merely asked which is it. And I get all this irrational name calling about how I know nothing. I never claimed omniscience. Show me where I was wrong. Was I wrong when I said," And yes, I understand the basic principle of Heisenberg's uncertainty , that the photon ( or whatever particle is used) disrupts the object and so that therefore one can only obtain position OR momentum." That is pretty much the only claim I made concerning my knowledge of QM.
Just calling a person ignorant with nothing to back it up is childish. Even then one should be polite instead of ranting," you should get a basic knowledge before discussing things far beyond you."

 

[wittgenstein]

"Do you know what 'matter' means? "
Dickfore
Look, if your only going to be an obnoxious troll, I'll refuse to talk with you. However, if you want to talk with me as an adult I'm more than willing.
GEE, tell me ( I'm such an idiot and you are soooo smart) what is matter and also tell me what is a dog, and what is a cat and...

 

[ZapperZ]

"An electron is a "matter". Yet, do you think it is "composed of atoms"?"
ZapperZ
?? When did I say that? Good grief! If you have that much of a misunderstanding of what I said no wonder you have no clue as to what I said.
Here, I'll make it simple. If I said " All dogs are composed of cells" and then I said," all dogs are composed of atoms" I am not saying,or even implying," all atoms are composed of cells."

Let me refresh your memory. You said

So if I said,"Yes, matter ( bricks and water) are composed of atoms." You would find that sentence too confusing to understand?

What do you think "matter" is in physics? Are you excluding electrons, protons, mesons, etc.. etc? How are you able to do this? Who gave you the right to define what "matter" is? Maybe THAT is the problem here. You are using terminologies that have definite meaning in physics, but then you make your own definition with them.

No sane discussion can come out of something like this.

Zz.

 

[ZapperZ]

"Do you know what 'matter' means? "
Dickfore
Look, if your only going to be an obnoxious troll, I'll refuse to talk with you. However, if you want to talk with me as an adult I'm more than willing.
GEE, tell me ( I'm such an idiot and you are soooo smart) what is matter and also tell me what is a dog, and what is a cat and...

This shows your very narrow definition of what "matter" is. If you wish to discussion a very restricted subset of "matter", then you should make that very clear in the beginning. If not, then your definition of matter is faulty.

Zz.

 

[wittgenstein]

Anyway I proved in post 21 that I have not made any claims about QM other then that quote about Heisenberg. And I offered 2 options ( objective reality before the collapse or no objective reality before the collapse . OK I know how you guys jump on any general statement. I'll simplify, the reality inside the box.)
Anyway, all the childish ranting was over nothing.

 

[wittgenstein]

OK. I was a little lax there. When I said that matter is made of atoms. I can see your point. But from that grammatical slip ( do you honestly think that I am so stupid that I think that electrons are composed of atoms?) you reach extreme conclusions. Please read my posts over , especially post 21 and point out where I was wrong. Considering that I was asking questions, politely, I think if you look at it without prejudice , you will see that my points and questions are rational. These red herrings and straw men do not mean anything.

 

[ZapperZ]

Anyway I proved in post 21 that I have not made any claims about QM other then that quote about Heisenberg. And I offered 2 options ( objective reality before the collapse or no objective reality before the collapse . OK I know how you guys jump on any general statement. I'll simplify, the reality inside the box.)
Anyway, all the childish ranting was over nothing.

You also need to realize that some of us here are NOT trying to attack you, but rather to make sure that you understand the words that you are using. Rather than be defensive about it, you could have paid a bit more attention and try to learn where you made the mistake. You asked a question based on physics. It is important that you learn what those words you are using actually mean, especially when you want physicists to respond to your questions.

Now, coming back to your original question, are you asking of realism is alive and well as far as QM is concerned? Before you answer that, you need to also figure out what is defined by "realism", especially in the context of the EPR/Bell-type experiments, which deals with "local realism". While such concept may have their own definitions, this concept is clearly defined in QM based on what is being tested via those experiments.

Again, I have no idea if this is what you are asking, since your original post makes several puzzling connection and statements.

Zz.

 

[wittgenstein]

I do not care one way or the other if you guys think I am an idiot. I simply want my question at least addressed without the name calling. Is what is inside the box an objective reality ( before being measured) or not. If the answer is "no". Is that "not an objective reality" in the logical positivist sense? That is why I gave the example of the impregnable box with a brick or water in it. A logical positivist would say that asking what is inside that box is a meaningless question. I disagree and find a logical positivist's definition of objective reality simplistic and trivial.

 

[Q_Goest]

I laid out two possibilities.
1. Before the collapse there is an actual reality ( particle or not), its just that we don't know what that reality is.
2. Before the collapse there is no reality regarding particle or not.

What did I get wrong? What other alternative is there? A or not A, show me something else. I did not take a side as to 1 or 2 .

You didn’t get anything “wrong”, I’m just responding to your (valid) question about logical positivism.

And I get all this irrational name calling about how I know nothing. I never claimed omniscience. Show me where I was wrong. Was I wrong when I said," And yes, I understand the basic principle of Heisenberg's uncertainty , that the photon ( or whatever particle is used) disrupts the object and so that therefore one can only obtain position OR momentum." That is pretty much the only claim I made concerning my knowledge of QM.
Just calling a person ignorant with nothing to back it up is childish. Even then one should be polite instead of ranting," you should get a basic knowledge before discussing things far beyond you."

I wasn’t calling you ignorant or any such thing. Not by a long shot. You asked a good question (I don’t respond to stupid ones) and you deserve a chance to discuss it. I don’t think logical positivism conflicts with #2:

2. Before the collapse there is no reality regarding particle or not.

In fact, I think ZapperZ would be a "logical positivist".
.
.
.

You also need to realize that some of us here are NOT trying to attack you, but rather to make sure that you understand the words that you are using.

Exactly… now relax and let’s discuss………

 

[wittgenstein]

I have no problem with you Q_Goest. I was addressing others that I felt were not listening to me, or at least they were not trying to understand what I was saying.

 

[Maui]

Wittgenstein, consider the following - it's much easier to make a case on solipsism than realism in our age of SR and qm, YET most physicists(>95%) don't consider solipsism a beneficial path to follow. This should give you a hint as to how most physicists feel about reality.
I think a quote by Cantor sums it up well, when upon stumbling on something that bears resemblance to Zeno's paradoxes in his set theory, he exclaimed:

"I see it, but i don't believe it"

Confusion is the natural state of being. Nobody should be afraid of it, or else one'd be indocrinated into somebody else's beliefs.

 

[apeiron]

I laid out two possibilities.
1. Before the collapse there is an actual reality ( particle or not), its just that we don't know what that reality is.
2. Before the collapse there is no reality regarding particle or not.

What did I get wrong? What other alternative is there? A or not A,

A third metaphysical alternative here is to view the "before" state as vague, a state of unformed potential. So a potential that can "really exist". Yet is also at the same time a (formally maximal) form of not existing.

This is the sort of thinking you would find in process physics, for example, where there are just events conjured into being by their contexts. So you can see something wave-like, or something particle-like, depending on how you frame the measurements.

However your original question did mix in quite a few separate questions.

The above is an ontological question (concerning what we believe is really out there - if we could really see it). It should not be mixed up with the epistemological issue of what we can know about the out there, and how we should go about learning about it.

So logical positivism is an epistemological stance. Not an ontological one. And Wittgenstein being one of its inspirations, you'll know all about it .

The key distinction from the general pragmatism and empiricism that we all agree on (minds can only model reality) is that the logical positivists wanted to shear the concepts employed by science of all their unnecessary "metaphysical" connotations. The meaning of qualitative terms are defined purely by the quantitative measures made in their name.

But logical positivism was of course based on a strong metaphysical position itself (rationalism). And failed to the extent that it was as usual a lurch of the pendulum of epistemology to the unnecessary extremes.

 

[ZapperZ]

In fact, I think ZapperZ would be a "logical positivist".

Do you have a label for people who put labels on other people?

Zz.

 

[ZapperZ]

I find this discussion interesting and frustrating at the same time (a form of superposition, I'm sure, except that "interesting" and "frustrating" might not be orthornormal basis states).

Interesting because of how people are interpreting, using their OWN preference, what quantum superposition actually means, without referring to established knowledge. It is also frustrating because all of this appears to be taking place "in vacuum", without regards even to the latest knowledge and advancement in physics. For example, would you care about the Leggett inequality and what it is testing? Does that fact that there are now several different experiments that violate such inequality (a more stringent test of realism than Bell's) would factor into people knowledge base on here BEFORE one actually offer an opinion?

A case in point is a paper that was published within the past 2 weeks. If you are not capable of understanding the actual paper, one should at least read a review of it on PhysicsWorld website:

http://physicsworld.com/cws/article/news/44580

The actual paper was published in New Journal of Physics, which is an open access publication, meaning you could get full access to the actual paper. You might want to read it just for the references, especially the physics surrounding Leggett's inequality.

Now THIS is something testable, and not simply based on TASTES or personal preference.

Zz.

 

[DevilsAvocado]

I laid out two possibilities.
1. Before the collapse there is an actual reality ( particle or not), its just that we don't know what that reality is.
2. Before the collapse there is no reality regarding particle or not.

What did I get wrong? What other alternative is there? A or not A, show me something else. I did not take a side as to 1 or 2 . I merely asked which is it. And I get all this irrational name calling about how I know nothing.

And the short answer is: The next Nobel Prize in Physics will go to the PF-user in this thread that can answer this question!

Honestly, I think I know what you are "going thru"... been there myself so to speak...

You must be careful when making "statements" here at PF, especially on Quantum Physics. Example:

Good grief! ... How am I supposed to respond to that? It is so obviously a misunderstanding that any explanation would be like saying 1+1=2 and that would only be insulting.

If I were a "QM Bloodhound" looking for some "fun", I would reply:

What do you mean by saying "1+1=2"...? Everyone with slightest knowledge of QM knows that 1 + 1 = 3. Please explain!?​

(This is the truth) And now a "funny quarrel" would begin, where I could play with you as much as I want, because you have absolutely no idea what I’m talking about, right?

But don’t pay too much attention to that "game"; just continue asking what you want to know.

My personal layman’s guess is that you are actually referring to the famous http://en.wikipedia.org/wiki/Bohr%E2%80%93Einstein_debates" , right?

In 1925 Werner Heisenberg’s matrix equations removed space and time from any underlying reality, and in 1926 Max Born proposed that the QM was to be understood as a probability without any causal explanation, and in 1927 Heisenberg and Born declared that the revolution was over and nothing further was needed.

This was too much for good old Einstein and his skepticism turned to dismay, and he spent the rest of his life finding a better "description" of the microscopic world, without any success.

The "peak" of the Einstein-Bohr Debate was afaict the 1935 paper with the title "Can Quantum-Mechanical Description of Physical Reality Be Considered Complete?", better known as the http://en.wikipedia.org/wiki/EPR_paradox" (mentioned by ZapperZ).

Until this point Niels Bohr had "dismantled" any "objection" from Einstein swift and easy. But this was something else. It took Bohr five months to reply and his paper had the exact same title:

(... and some say Bohr didn’t even understand "the problem" ...)

Anyhow, the debate between Einstein & Bohr continued, and was never settled.

A quick jump to present knowledge, we know thanks to John Bell, Alain Aspect and Anton Zeilinger et al. that Einstein was wrong – Local Hidden Variables (LHV) and Local Realism is as dead as the Norwegian Blue Parrot. It just doesn’t work, period.

You can have non-local realism, or local non-realism, or non-local non-realism, but NOT Local Realism.

(A better word for non-realism is http://plato.stanford.edu/entries/physics-holism/" )

As you can see, the present knowledge of QM cannot be answered with 1 or 2, it’s much more "multifaceted" than that (that’s why some are "upset" ). But the good news is that a lot of geniuses are working hard on the solution!


P.S. Good info on the Einstein-Bohr Debate:

David Kaiser - Associate Professor MIT
http://web.mit.edu/dikaiser/www/Kaiser.AENB.pdf"
British Journal for the History of Science 27 (1994): 129-152.

 

[Fredrik]

Is what is inside the box an objective reality ( before being measured) or not.

I don't think there's a simple yes/no answer to that. I'm not even sure how to make sense of the question. Is it about what's actually in the box, or about the mathematical representation of it? If you meant the former, the question gets really weird, because now the meaning of the question depends on its answer.

That is why I gave the example of the impregnable box with a brick or water in it. A logical positivist would say that asking what is inside that box is a meaningless question.

You seem to be asking if there's water in the box given that you have put water into it, and then made the necessary arrangements to make sure that it's impossible in principle to determine the contents of the box. The problem with this scenario is that the theory we're supposed to use to answer the question doesn't allow such arrangements to be made. So QM neither agrees nor disagrees with this positivist, because you're describing a scenario that's inconsistent with QM.

 

[apeiron]

A case in point is a paper that was published within the past 2 weeks. If you are not capable of understanding the actual paper, one should at least read a review of it on PhysicsWorld website:.

Yes, but how does this change anything here?

QM says models of reality based on the principle of locality, of effective cause, fail. Experiments have been cutting down the final loopholes, which is certainly important to know. But the weight of evidence was already huge.

So now we should be cheerfully moving on to models of reality that are not fundamentally dependent on the principle of locality (but where locality may still be an emergent property of course).

 

[DevilsAvocado]

... A case in point is a paper that was published within the past 2 weeks. If you are not capable of understanding the actual paper, one should at least read a review of it on PhysicsWorld website:

http://physicsworld.com/cws/article/news/44580

WOW! JUST WOW!

Many many thanks ZapperZ! This is just amazing! The world is non-local AND non-separable!


@wittgenstein: What did I tell you? PF will give you exciting news!

 

[ZapperZ]

Yes, but how does this change anything here?

It changed EVERYTHING here. It answered the OP's question with respect to what the physics is currently saying. It also points to legitimate references that not only provide the theoretical description of realism, but also the supportingexperimental evidence which shows that this isn't simply a matter of TASTES. These have been severely lacking in the discussion so far till now!

QM says models of reality based on the principle of locality, of effective cause, fail. Experiments have been cutting down the final loopholes, which is certainly important to know. But the weight of evidence was already huge.

Then you just missed the point of the Leggett inequality. The latest set of experiments are addressing the possibility that, even when the locality principle is relaxed, i.e. one allows for non-locality, realism, or more specifically, a large number of classes of realism, still cannot be saved. It rules out large number of non-local realism models.

Zz.

 

[DevilsAvocado]

@ZapperZ: How about moving this thread back to Quantum Physics? This is not Philosophy, it’s wonderful QM news!

 

[ZapperZ]

@ZapperZ: How about moving this thread back to Quantum Physics? This is not Philosophy, it’s wonderful QM news!

No way! The people who are doing most of the discussion on here are not interested in the physics, or the accuracy of the physics they are discussing. They're more interested in finding "meanings" behind these things, i.e. things that can be discussed based on personal tastes with no possibility of any empirical tests.

Zz.

 

[DevilsAvocado]

No way!

Okay, just asking.

It rules out large number of non-local realism models.

Can you mention any models that survive? dBB?

 

[apeiron]

It changed EVERYTHING here. It answered the OP's question with respect to what the physics is currently saying. It also points to legitimate references that not only provide the theoretical description of realism, but also the supportingexperimental evidence which shows that this isn't simply a matter of TASTES. These have been severely lacking in the discussion so far till now!

The reference is still just confirmation of a result demonstrated in 2007. So saying it changes "everything" sounds crackpot to me. I can't see that it changes anything so far as the thread is concerned.

Anyone who has yet to give up local realism and start seeking the alternatives is plainly not paying attention.

What puzzles me here is why you go on about the data when the data is accepted. Now we need to move on to the theoretical and metaphysical consequences. Which has nothing whatsoever to do with tastes.

Then you just missed the point of the Leggett inequality. The latest set of experiments are addressing the possibility that, even when the locality principle is relaxed, i.e. one allows for non-locality, realism, or more specifically, a large number of classes of realism, still cannot be saved. It rules out large number of non-local realism models.

Again, what does this confirmation add to Zeilinger's 2007 result? And anyone who hadn't chucked out local realism with Aspect's original 1982 experiments could only have been grasping at straws.

So both locality and realism have for sure now both bitten the dust. What metaphysics do you suggest to replace them?

As I have said often enough, I opt for vagueness over realism, and systems causality over the principle of locality (ie: Aristotle's four causes over just efficient cause alone).

Given this is a philosophy forum, do you have any concrete metaphysical view to offer now that local realism is agreed to be a dead parrot, not merely resting on the bottom of its cage or pining for the fjords?

 

[ZapperZ]

The reference is still just confirmation of a result demonstrated in 2007. So saying it changes "everything" sounds crackpot to me. I can't see that it changes anything so far as the thread is concerned.

It answered the OP. In case you forgot, this was what was asked:

I am confused by the philosophical assumptions behind Quantum Mechanics. Are physicists logical positivists? The reason I ask that is because it seems that they believe that if something in intrinsically unknowable it does not exist as a truthful proposition. For example before the collapse what is happening? Suppose, I have an impregnable box ( even logically necessarily impregnable) . I do not know if there is a brick ( particle) or water ( wave) inside.

Does that mean that one possibility is not correct and the other is also not correct? I am totally confused! Please help! [/quote]

The OP WAS asking about realism from the point of view of what we know about QM. This directly answers that question with the LATEST set of results fresh from 2 weeks ago. You offered none.

Anyone who has yet to give up local realism and start seeking the alternatives is plainly not paying attention.

This latest result has nothing to do with "local realism". It has everything to do with non-local realism!

What puzzles me here is why you go on about the data when the data is accepted. Now we need to move on to the theoretical and metaphysical consequences. Which has nothing whatsoever to do with tastes.

It does, when you still can't see the significant difference with this latest result.

Again, what does this confirmation add to Zeilinger's 2007 result? And anyone who hadn't chucked out local realism with Aspect's original 1982 experiments could only have been grasping at straws.

So both locality and realism have for sure now both bitten the dust. What metaphysics do you suggest to replace them?

As I have said often enough, I opt for vagueness over realism, and systems causality over the principle of locality (ie: Aristotle's four causes over just efficient cause alone).

Given this is a philosophy forum, do you have any concrete metaphysical view to offer now that local realism is agreed to be a dead parrot, not merely resting on the bottom of its cage or pining for the fjords?

Zeilinger's result, especially the one testing the GHZ inequality, is DIFFERENT than the Leggett test! One only needs to read the actual paper that is referenced in that Physics World article!

If it is no different, then why is there Leggett's inequality? You're basically saying that there's no difference between it and, say, Bell inequality, and that all these publications are doing nothing but repetitions of well-known results! I suggest you write your rebuttal to those papers.

Zz.

 

[yoda jedi]

The most useful way to think of QM is not as a description of reality, but as a set of rules that tells us how to calculate probabilities of possible results of experiments.

i agree.
just a phenomenological theory.
a epistemic one.

The reference is still just confirmation of a result demonstrated in 2007. So saying it changes "everything" sounds crackpot to me. I can't see that it changes anything so far as the thread is concerned.

Anyone who has yet to give up local realism and start seeking the alternatives is plainly not paying attention.

What puzzles me here is why you go on about the data when the data is accepted. Now we need to move on to the theoretical and metaphysical consequences. Which has nothing whatsoever to do with tastes.
Again, what does this confirmation add to Zeilinger's 2007 result? And anyone who hadn't chucked out local realism with Aspect's original 1982 experiments could only have been grasping at straws.

i agree, just confirming nonlocality (non-separability)
i posted it, at:
Another for Leggett inequalities.
Dec17-10, 04:36 PM
https://www.physicsforums.com/showthread.php?t=457422

A third metaphysical alternative here is to view the "before" state as vague, a state of unformed potential. So a potential that can "really exist". Yet is also at the same time a (formally maximal) form of not existing.

or just that counterfactual definiteness is not a necessary condition of reality.

"If, without in any way disturbing a system, we can predict with certainty (i.e., with
probability equal to unity) the value of a physical quantity, then there exists an
element of physical reality corresponding to this physical quantity." (Realism accord EPR)

value of ? ...a value of something, what is something ? something that exist, no nothing
that is, be REAL is exist in whatever form (but in consistent way and autonomous).

Reality is the state of things as they actually exist.

BEING QUA BEING:
"being qua being", or being understood as being. It examines what can be asserted about anything that exists just because of its existence and not because of any special qualities it has.

That is VALUES
not special qualities - not specific values....

 

[apeiron]

The OP WAS asking about realism from the point of view of what we know about QM. This directly answers that question with the LATEST set of results fresh from 2 weeks ago. You offered none.

I think if you check back you will find that I answered the OP central question, commenting that there is in fact a third metaphysical position that is possible beyond either total local realism, or zero local realism.

You keep insisting the latest data makes EVERY difference. I don't see it makes any difference. Total local realism should long ago have been abandoned by any reasonable person. Which means the actual alternatives come down to a non-position - reality is just weird, get over it - or, as I suggest, we can consider a systems-based metaphysical perspective.

This latest result has nothing to do with "local realism". It has everything to do with non-local realism!

But the OP already was assuming the extreme cases. So both the principle of locality, and of realism, were deemed violated. At least that seems fair to impute from what was indeed a rather confused presentation of the issues. Or can you show where the OP was in fact attempting to preserve realism while conceding non-locality, and so where the Leggett data becomes relevant?

Zeilinger's result, especially the one testing the GHZ inequality, is DIFFERENT than the Leggett test! One only needs to read the actual paper that is referenced in that Physics World article!

So you want to argue that this Nature paper was not about Leggett's inequality. Really?

S. Gröblacher, T. Paterek, R. Kaltenbaek, C. Brukner, M. Zukowski, M. Aspelmeyer, A. Zeilinger, An experimental test of non-local realism, Nature 446, 871-875 (2007)

GHZ was back in the 1990s. Yes?

 

[apeiron]

or just that counterfactual definiteness is not a necessary condition of reality.

If you accept the principle of vagueness, then you are indeed saying that reality is not fundamentally definite.

This was what CS Peirce was trying to articulate with his logic of vagueness. Reality is indeterminate at base. That is the big paradigm shift to make - to actually give up a belief that definite outcomes must have definite initiating conditions. Then you can begin to think about the kind of causal machinery that can develop a self-organised definiteness from the fundamentally indefinite.

Peirce's system was the triadic machinery of semiosis. It was a good start.

 

[yoda jedi]

If you accept the principle of vagueness, then you are indeed saying that reality is not fundamentally definite.

This was what CS Peirce was trying to articulate with his logic of vagueness. Reality is indeterminate at base. That is the big paradigm shift to make - to actually give up a belief that definite outcomes must have definite initiating conditions. Then you can begin to think about the kind of causal machinery that can develop a self-organised definiteness from the fundamentally indefinite.

Peirce's system was the triadic machinery of semiosis. It was a good start.

yes, i basically agree.
tentatively, because who knows, maybe there are definite values, if not, it doesn't matter because we have vagueness or indefiniteness,
...a state of unformed potential (I thought the same thing, in almost identical terms)

 

[ZapperZ]

I think if you check back you will find that I answered the OP central question, commenting that there is in fact a third metaphysical position that is possible beyond either total local realism, or zero local realism.

But your "offering" has no physical validity! You didn't back it up with anything to be able to differentiate it from the rest. You just TOLD him and that's that! I do not consider that to be valid.

You keep insisting the latest data makes EVERY difference. I don't see it makes any difference. Total local realism should long ago have been abandoned by any reasonable person. Which means the actual alternatives come down to a non-position - reality is just weird, get over it - or, as I suggest, we can consider a systems-based metaphysical perspective.



But the OP already was assuming the extreme cases. So both the principle of locality, and of realism, were deemed violated. At least that seems fair to impute from what was indeed a rather confused presentation of the issues. Or can you show where the OP was in fact attempting to preserve realism while conceding non-locality, and so where the Leggett data becomes relevant?



So you want to argue that this Nature paper was not about Leggett's inequality. Really?

S. Gröblacher, T. Paterek, R. Kaltenbaek, C. Brukner, M. Zukowski, M. Aspelmeyer, A. Zeilinger, An experimental test of non-local realism, Nature 446, 871-875 (2007)

GHZ was back in the 1990s. Yes?

OK, I mistook your "Zeilinger" reference for something else. I referenced this work at Groblacher work, which I've highlighted already elsewhere.

https://www.physicsforums.com/showpost.php?p=1307660&postcount=40

And yes, there IS a difference. The Groblacher's experiment ruled out a small class of non-local realism. But this doesn't make more stringent test of the Leggett inequality. In fact, there were two more experimental work published that made further tests on this:

T. Paterek et al. "Experimental Test of Non-Local Realistic Theories Without The Rotational Symmetry Assumption", Phys. Rev. Lett. 99, 210406 (2007).

Cyril Branciard et al. " Experimental Falsification of Leggett's Nonlocal Variable Model", Phys. Rev. Lett. 99, 210407 (2007).

No one single experiment can be convincing enough! And especially with experiments like this where sampling issues and loopholes could be present, no one experiment can make a totally convincing argument that rules out a whole class of concept!

Until I brought it up, no one made ANY kind of references to such issues that presented theoretical and experimental support for our understanding of realism. All we got were handwaving argument with no indication of any degree of validity to support such an argument.

Zz.

 

[DevilsAvocado]

About Non-local Realism and Leggett’s inequality:

I think there’s been some "journalistic misinterpretations". Yes, in http://physicsworld.com/cws/article/news/44580" they say "a large class of nonlocal theories". What they don’t say is that:

The de Broglie-Bohm theory does not satisfy Leggett’s assumptions.

(I think it has do with the fact that in dBB the photons do not have a well-defined value of polarization, but instead it is determined non-locally via the quantum potential.)

So, Non-local Realism is alive and kicking as before!

Readdressing OP’s question on what’s in the "impregnable box", there’s still three options:

• locality=true/realism=false
  
  
• locality=false/realism=true
  
  
• locality=false/realism=false

And Local Realism is, as before, a dead parrot that should be returned to Michael Palin's pet shop.