Is there a fundamental flaw in our understanding of space and conservation laws?

[vanesch]

MWI is a most unattractive way of, er, looking at things. It certainly doesn't explain any of the stuff that it purports to explain. It seems to be saying that since the quantum processes involved in the generation of experimental observations (data) are pretty much unknown (ie., there's a measurement problem and an accompanying wave function interpretation problem), then let's just interpret the superposition of all possible outcomes as meaning that all possible outcomes actually happened (even though that interpretation doesn't actually mean anything). MWI also supposedly solves the locality/nonlocality problem.

Yes. Given the basic principle of quantum theory, which says that a system state is given by an element of hilbert space, and that that hilbert space is found by considering the superposition of all possible "classical states", it seems normal to extend this concept to "observer states".

There is no fundamental difference between the physics happening in "observers" and in "systems". As such, their descriptions should be the same. But if that is true (which we accept, if we accept the basic postulate of quantum theory to be universal), then there is no way out of saying that observers must be in states which are superpositions of "different states of observation". It is simply the application of the basic postulate of quantum theory to observers, if we don't want to give them any different physics than other physical structures.

So if we accept the Schroedinger equation to be perfectly universally valid, then there is no escaping that at a certain point in time, we should consider that Alice's state is a superposition of "Alice saw up" and "Alice saw down". This follows from the linearity of the Schroedinger equation, and the assumption that this is applicable in principle to a physical structure such as Alice.

We also know that quantum-mechanically, there can be no equivalence between "superposition" and "statistical ignorance". So the superposition of Alice saw down and Alice saw up is not the same as a statistical mixture.

We also know the measurement axioms, which specify that "when we do a measurement" (which is after all, ultimately a subjective experience), then a superposition becomes a mixture of "observed outcomes". But if we refuse to accept that there happens some DIFFERENT PHYSICS in a measurement interaction, than in a "system interaction", then the meaning of this measurement axiom is simply giving us the relationship between the actual physical state (which we found to be a superposition), and a subjective experience. Hence, the "state -> statistical ensemble" transition seems to hide in the transition "physical state -> subjective experience".

Now, the nice thing of doing this - and the only reason in fact - is that we can keep the full unitary machinery of quantum theory. As such, we can keep all the nice properties of this machinery, and we don't need to introduce any ugly "change in physics due to observers". Also, we can do what we've always done in physics, that is, to take the essential formal elements as describing reality.
This is the reason why I adhere to MWI *as an interpretation of QM*: it allows you to take the formalism seriously (in the same way as you take the spacetime manifold for real in relativity, or you take "particles" for real in Newtonian mechanics). In other words, MWI allows you to resist the temptation to fiddle with the formalism for philosophical preferences. The formalism should speak for itself, and we shouldn't have any a priori over it.

The bonus one gets also (which is somehow also comprehensible) is that a lot of paradoxes that appear in QM when one considers QM just as a kind of thing that must ultimately transit to a classical world, disappear. The main difficulty being the EPR problem with Bell's theorem. It is no wonder that the paradoxes disappear: you take the formalism which provides you with these predictions in the first place, for real. As such, there is perfect agreement between the ontology, and the basic properties of quantum theory, and you avoid paradoxes.

Now, the measurement problem really is a problem in that physicists really don't know much about measurement (or emission, for that matter) processes at the quantum level. But I think that we can agree that the MWI solution doesn't provide any new knowledge of such processes.

It provides for a view which helps you not to consider it as a problem.
A bit like taking on a spacetime manifold view avoids you to consider the "problem" of "simultaneity". You UNDERSTAND why it is not a problem in that view.

The locality/nonlocality problem hasn't yet attained the status of being a real problem (everything seems to behave as if locality were the reigning standard ... and no superluminal anything has been produced for our consideration), so maybe its solution by way of MWI is premature.

Well, if you have no problem with locality in your view of QM, that is ok then, but I wonder how you consider Bell's theorem then.

ttn's idea (and demonstrations) that MWI is silly on several different fronts is more appealing than vanesch's adherence to MWI -- which adherence doesn't promise to help his (vanesch's ... or anybody else's for that matter ) understanding of physics or of the world. Of course, if MWI could be used to improve our knowledge and facility regarding, say, high T_c superconducting, or dark energy, etc., then I'll have to reconsider.

No, MWI gives me the "ease of mind" not to look for problems where there aren't any, such as locality or the "measurement problem". It makes me resist the temptation to throw out of the window good and powerful principles such as the principle of relativity.

 

[setAI]

There is no fundamental difference between the physics happening in "observers" and in "systems". As such, their descriptions should be the same. But if that is true (which we accept, if we accept the basic postulate of quantum theory to be universal), then there is no way out of saying that observers must be in states which are superpositions of "different states of observation". It is simply the application of the basic postulate of quantum theory to observers, if we don't want to give them any different physics than other physical structures.

extremely well said- this is the source of much frustration- opponents of MWI and multiverse theories/ontologies in general would have us accept a grand epicycle- a demon that adds some new physical principle that somehow magically allows only one 'real' observer state- simply because they find the implications of unitary quantum mechanics 'unattractive'

 

[ttn]

I always claimed that "worlds" is an observer-dependent concept (one should say "many subjective worlds, one objective one" ; or in other words: a statistical ensemble for subjective experiences, one single objective world). That's why all those "splittings" and so on are not objective phenomena. They are subjective phenomena.

Yes, fine. But what you are less clear about is what the "one objective one" is made of and where it is. (As far as I can tell, there's no physical matter in your "one objective world" and whatever it does contain, if anything, doesn't live in 3D physical space.)

Also, there isn't to be any lorentz-independent notion of "how many worlds" there are, given that it is observer dependent, in the same way as a coordinate system of the rest frame of an observer is, well, observer dependent.

Oh jeez.

 

[ttn]

There is no fundamental difference between the physics happening in "observers" and in "systems".

Huh? There is, to the contrary, no more fundamental difference than the difference between stuff happening "in observers" and stuff happening "in [physical, external] systems".

As such, their descriptions should be the same.

But in MWI they aren't.

So if we accept the Schroedinger equation to be perfectly universally valid, then there is no escaping that at a certain point in time, we should consider that Alice's state is a superposition of "Alice saw up" and "Alice saw down". This follows from the linearity of the Schroedinger equation, and the assumption that this is applicable in principle to a physical structure such as Alice.

...and the evasion of the ever-present fact that no such states have ever been observed to exist.

We also know the measurement axioms, which specify that "when we do a measurement" (which is after all, ultimately a subjective experience),

That's where we disagree. Performing an experiment and getting an outcome is NOT merely having a certain kind of subjective experience. Reality is not virtual reality.

This is the reason why I adhere to MWI *as an interpretation of QM*: it allows you to take the formalism seriously (in the same way as you take the spacetime manifold for real in relativity, or you take "particles" for real in Newtonian mechanics). In other words, MWI allows you to resist the temptation to fiddle with the formalism for philosophical preferences.

Except that the only way of coming even remotely close to making MWI possible to consider seriously (let alone accept), is to adopt a very radial anti-scientific philosophical position about the basic relationship between consciousness and its objects -- namely, that (for all we know) consciousness *has* no objects.

This is the same kind of BS argument one used to always hear about Bohmian Mechanics -- "oh, that's just philosophy". So it is. But for Bohm's theory, the philosophy is good philosophy, true philosophy. What the people who make this argument don't understand is that Copenhagen is just as philosophical, and its philosophy is complete anti-science nonsense (Kantian subjectivism, existentialism, logical positivism, ...). It's not valid to dismiss one thing because it's "philosophical" when what one advocates instead is equally philosophical -- and it's particularly invalid when the philosophy one advocates instead is an embarrassing unscientific pile of poo.

The formalism should speak for itself, and we shouldn't have any a priori over it.

The whole idea that "the formalism should [or could] speak for itself" is philosophy.

No, MWI gives me the "ease of mind" not to look for problems where there aren't any, such as locality or the "measurement problem". It makes me resist the temptation to throw out of the window good and powerful principles such as the principle of relativity.

Yes, it is very difficult to resist the temptation to follow empirical evidence where it leads.

 

[ttn]

extremely well said- this is the source of much frustration- opponents of MWI and multiverse theories/ontologies in general would have us accept a grand epicycle- a demon that adds some new physical principle that somehow magically allows only one 'real' observer state- simply because they find the implications of unitary quantum mechanics 'unattractive'

There it is again. "Everybody has an accent but me."

 

[vanesch]

Yes, fine. But what you are less clear about is what the "one objective one" is made of and where it is.

It is a mathematical object, of course.

If you talk about "space", that's also a mathematical object, right ? "particles" are mappings from R to that space.

 

[vanesch]

Huh? There is, to the contrary, no more fundamental difference than the difference between stuff happening "in observers" and stuff happening "in [physical, external] systems".

There is also no bigger difference than "subjective experiences" and "physical world". We take it that the physics of the physical observer (=body) is the same physics as anything else. However, you should admit that it is a totally different matter to say that the subjective experiences emerging from such a physical structure ought to follow the same physical laws. Subjective worlds are not objective worlds. It is the difference between epistemology and ontology.

...and the evasion of the ever-present fact that no such states have ever been observed to exist.

You mean, quantum superposition effects have not been indirectly observed ?
Interference has never been observed ?

What has never been observed (subjectively), is _by definition_ the superposition of two states of subjective observation. This is so *by very construction*!

You could just as well say that two different eigentimes have never been observed by one and the same observer and hence that never ever, any difference in simultaneity has been seen by one single observer.

That's where we disagree. Performing an experiment and getting an outcome is NOT merely having a certain kind of subjective experience. Reality is not virtual reality.

THIS is what I'm trying to make you see: it is a statement which is absolutely not evidently true, and in fact, for which not the slightest ounce of scientific proof can be advanced, by its very ontological nature.

When you "see a chair", do you:

1) observe directly a chair ?
2) observe directly electromagnetic radiation coming from the chair ? (holography!)
3) observe directly photochemical processes in your retina ?
4) observe directly nervous pulses from the ocular nerve ?
5) observe directly certain brain states ? Quantum brain states or classical brain states ?

Where is the scientific evidence which FALSIFIES that you are observing a brain state ? I try to make you see that your position is not given by any *scientific* argument, but by a philosophical argument (and so does mine).

This is not an argument I invent. It is a well-known position, which posits the separation between ontological and epistemological argumentation.

Except that the only way of coming even remotely close to making MWI possible to consider seriously (let alone accept), is to adopt a very radial anti-scientific philosophical position about the basic relationship between consciousness and its objects -- namely, that (for all we know) consciousness *has* no objects.

Yes, but that is not an anti-scientific position. You cannot do an experiment in which you FALSIFY that position (which is the only way of calling a position anti-scientific). The proposition is scientifically neutral. It is a philosophical position which is entirely compatible with all of science. It is not a scientific position, but it is not anti-scientific either. However, it forms the basis of a view which IS scientific, in the sense that it makes predictions of observations which are entirely in agreement with what is observed.

Ontological positions are philosophical positions. They are never scientific positions: scientific positions are purely epistemological. You make one, I make another one. Yours don't allow certain forms of scientific theories, while mine does. As such, you allow a purely philosophical position (because an ontology assumption) to interfere with the construction of scientific theories, while I don't.

This is the same kind of BS argument one used to always hear about Bohmian Mechanics -- "oh, that's just philosophy". So it is. But for Bohm's theory, the philosophy is good philosophy, true philosophy.

You see, that's where you go wrong. There is no "good" and "bad" philosophy. There is no "good" and "bad" ontology.

It's not valid to dismiss one thing because it's "philosophical" when what one advocates instead is equally philosophical -- and it's particularly invalid when the philosophy one advocates instead is an embarrassing unscientific pile of poo.

As always, it comes down to an emotional argument. There is no rational, scientific argument against MWI, no more as there is against Bohmian mechanics, or for that matter, any other form of interpretation. Your classification of "good philosophy" and "bad philosophy", and the argument of wanting ontological positions to be scientific or anti-scientific illustrate the issue.

But there is a scientifically based argument:

The whole idea that "the formalism should [or could] speak for itself" is philosophy.

That is, let us not IMPOSE a priori philosophical arguments! Let us see what we have formally derived from our epistemological knowledge (and that IS science), and then let us stop there and take that as the only suggestion for an ontological position.

In other words, in as far as we are going to have to make a philosophical choice - which is: to make a hypothesis of ontology - let us try to be as unbiased as possible, and take as a suggestion (and nothing more than this), what we derived formally from the scientific method. In other words, because I have not much confidence in any a priori philosophical requirements, I try to take the position in which I give as few a priori input from that side as possible.

This is, by itself, indeed a philosophical position. You can choose something else (visibly you do so). However, there is not more or less merit to one philosophical position over another. So all argumentation of "this is BAD philosophy", this is RUBBISH, we all KNOW that it isn't (ontologically) true, ... are demonstrations of lack of genuine arguments (and essentially emotional statements).

As I said, I have never seen an argument that is NOT of this kind against MWI.

There is of course no scientific "proof" of MWI anymore than there could be a proof of Bohmian mechanics or anything else, given that they are all based upon ontological statements which are, by definition, philosophical positions, and not scientific ones. The only things that one can demonstrate scientifically, are epistemological concepts.

The advantage of MWI, for those who consider that an advantage, is that it doesn't require any change to the formalism. It takes the quantum formalism as is. In other words, in MWI, we don't permit weak philosophical a priori arguments to intervene in the formulation of a scientific theory. In MWI, we do not require a choice between fundamental principles on which the formalism is based, just for the sake of an extra philosophical requirement one might have.

It is the only use of MWI: to help one accept the formalism as it is, and to refrain from the desire to intervene in the formalism (and render it less "principle-based", just for the sake of some or other philosophical requirement). It helps one to accept quantum mechanics as something which might be a fundamental theory.

And this, by itself, has scientific merit. Indeed, although a position such as Bohmian mechanics can maybe run after the facts, and - especially in the domain of quantum field theory - with a lot of difficulty, ACCOMODATE what has been discovered formally before, admit that, if in the 30ies one would have gone for Bohmian mechanics (remember, no spin!), it would not have been an inspirationally fruitful ground in order to do things such as gauge theory. The modifications to the formalism required by the philosophical position which is at the basis of Bohmian mechanics, wouldn't have facilitated all the discoveries in QFT that followed. Bohmian mechanics is not "wired up" to suggest things such as gauge invariance. At most, with some difficulty, it can accommodate. This is because Bohmian mechanics has KILLED certain principles, of which one had to put the effect again in by hand.

THIS is why I consider it as not a happy idea to fiddle with the formalism just for the sake of some philosophical position, but rather, to let the formalism speak for itself.

EDIT: this is also why I don't mind the "shut up and calculate" position. In as far as one doesn't feel the urge to consider fiddling with the formalism for any other reason than observational, or for reasons of mathematical/formal consistency, that is fine.
It is when one starts to want to do things to the formalism JUST for the sake of philosophical positions, and by that, render the mathematical/formal system less "smooth", "simple" (Occam)... that one is making a potentially expensive mistake.

 

[ttn]

It is a mathematical object, of course.

But does that "mathematical object" in some way *describe* the "one objective world" that you say exists according to MWI?

 

[ttn]

You mean, quantum superposition effects have not been indirectly observed ?

If we're being careful with terminology, "indirectly observed" is a contradiction in terms. Quantum superposition effects have been *inferred* -- inferred from things that have been directly observed.

But my point was to object to the specific thing you mentioned -- a human observer being in a superposition of two belief states. *That* has never been observed, and neither has anything been observed from which one could infer it.

When you "see a chair", do you:

1) observe directly a chair ?

Yes.

2) observe directly electromagnetic radiation coming from the chair ? (holography!)

No. You observe the chair by means of the electromagnetic radiation -- but of course one doesn't observe *that*. One is completely unaware of it for a long time (until one takes some physics classes, or in terms of the development of history, until the 19th century or so).

3) observe directly photochemical processes in your retina ?

No, one doesn't directly observe those. They are discovered much later by advanced scientific inference.

4) observe directly nervous pulses from the ocular nerve ?

No, same as above.

5) observe directly certain brain states ? Quantum brain states or classical brain states ?

No, same as above.

Where is the scientific evidence which FALSIFIES that you are observing a brain state ?

Claims which are obviously false to begin with don't require such "falsification". The falsification is that the word "observation" actually means something, and we simply do not observe brain states. The vast majority of people have literally never observed a brain.

I try to make you see that your position is not given by any *scientific* argument, but by a philosophical argument (and so does mine).

This is where we differ. You equate philosophy = ontology = arbitrary. But then practically everything in legitimate science is arbitrary made up bogus "philosophy", and what is *left* of science according to your conception is some ridiculous game of trying to account for "subjective experience" but without allowing yourself to believe ever that these experiences are experiences *of* anything. And that is a fundamental, fatal, philosophical flaw in your whole way of thinking about all of this. Consciousness *means* consciousness *of* *something*. To be *aware* of something, is to be aware *of something*. Consciousness without an object is a contradiction in terms. So your whole conception of science which is based on this fundamental philosophical error falls apart.

By contrast, my conception of science is also based on a philosophy. But mine is based on a valid philosophy, not an invalid one. (See, we disagree about whether philosophy = arbitrary, and hence about whether there can be such a distinction as good vs bad philosophy. Ironically, it's bad philosophy which makes you think there's no such difference.) Mine is based on a philosophy that is "scientific" (though that is admittedly an imprecise term here) in the sense of being based on empirical observation -- for example, the observations by which we arrive at basic concepts like "consciousness".

Yes, but that is not an anti-scientific position. You cannot do an experiment in which you FALSIFY that position (which is the only way of calling a position anti-scientific).

Or at least so says the philosopher Karl Popper.

That's the problem here. It's just what I've been saying over and over again. You're convinced that (a) philosophy is just arbitrary crap and we shouldn't ever let it influence our scientific thinking, and (b) that you can prove that by appeal to certain philosophical doctrines which you regard as just obviously true beyond the shadow of any doubt.

Don't you see the problem there? In (b) you confess that it is necessary to have a philosophical base for one's whole conception of the nature and goals of science, which in turn influences how one assesses specific things in science. But because of (a) you refuse to take *seriously* the task of then working out what philosophy is right, and what the right conception of science is. So you're caught in a vicious circle.

Ontological positions are philosophical positions. They are never scientific positions: scientific positions are purely epistemological.

See, I think that is just preposterous nonsense. (No, that's not an emotional statement, just an honest, dry, factual assessment.)

"There's a table in front of me." "Matter is made of atoms." "There's another planet beyond Uranus which is perturbing its orbit through gravitational forces." "Novae in the sky are caused by the core-collapse of a supermassive progenitor star whose core comes to exceed the Chandresekhar limit." "Genetic inheritance occurs through the mechanism of DNA splitting and recombination."

To you all of these are evidently "philosophical", not science. But look at what is left of science without these things! As a simple empirical statement based on looking at the history of thought and which things we use the word "science" to distinguish from which others, it is quite clear that your conception of "science" is simply *wrong*. You are fatally mis-classifying what is and what is not science.

You make one, I make another one. Yours don't allow certain forms of scientific theories, while mine does. As such, you allow a purely philosophical position (because an ontology assumption) to interfere with the construction of scientific theories, while I don't.

But you see, you do. Even worse than I do. That we can't be sure whether there are really tables and cats, is a philosophical position (maybe not exactly "ontological", but "anti-ontological" and surely about the same *issues* that what you call "ontological" positions are about).

You see, that's where you go wrong. There is no "good" and "bad" philosophy. There is no "good" and "bad" ontology.

I don't agree. There is good and bad philosophy. I mean, even you know that there have been all sorts of conflicting philosophical positions put forward on all sorts of points. They can't all be equally right. I guess your view is that they're all equally wrong, equally empty, equally nothing, equally pointless. But I completely and totally disagree. The issues (or at least some of them) are crucial, and are fundamental to science. We need answers to them. And so we need to distinguish the right answers from the wrong answers.

As to ontology: someone who starts their philosophy by saying "I just know a priori that there is a god, and that he is omnipotent, omniscient, and has really great hair to boot" is doing bad philosophy. Someone who starts their philosophy by saying "I know there are tables and chairs because I *see* them and I know I am conscious" is doing good philosophy.

As always, it comes down to an emotional argument. There is no rational, scientific argument against MWI, no more as there is against Bohmian mechanics, or for that matter, any other form of interpretation.

So then how the heck can you justify spending all this time arguing about it? How can you justify considering yourself a proponent of MWI? To you this is all just a pointless game, in which we know going in that there is no answer, no way to actually establish what is true, what the world is really like (even if it takes hundreds of years)? Not to me.

That is, let us not IMPOSE a priori philosophical arguments!

What you refuse to see is that philosophy doesn't necessarily have to be "a priori". I reject completely the idea of "a priori". I'm an empiricist. And yet I believe philosophy is important and valid. To you that's a self contradiction I guess -- because you refuse to see that all your beliefs are influenced by the philosophy *you* (unwittingly?) accept.

Let us see what we have formally derived from our epistemological knowledge (and that IS science), and then let us stop there and take that as the only suggestion for an ontological position.

But I completely agree with this. It's just that I think we can be 100% certain, based on what you call "epistemological knowledge" (by which I assume you just mean "empirical", based in observation), that there are tables and chairs and cats (not to mention extra-solar planets, atoms, dark matter, etc.). You disagree because you define epistemology/empiricism/experience differently, which is a *philosophical issue*. But you are blind to the fact that you take this radical philosophical position and that it actually influences everything you are saying. Everybody else has an accent.

In other words, in as far as we are going to have to make a philosophical choice - which is: to make a hypothesis of ontology - let us try to be as unbiased as possible, and take as a suggestion (and nothing more than this), what we derived formally from the scientific method.

I agree, in so far as we are talking about questions of unobservables, things that have to be inferred from what is observed. There is no such debate over things that are directly observed. As an empiricist, I believe there is no possibly better warrant for believing something exists, than that I *see* it. Since any *other* warrant (some complex chain of scientific inference) has to be *based exclusively* on empirical/observational evidence, the end of such a chain could never be more certain than the things at its base. So if you don't think tables are real, if you don't think *seeing* them is enough evidence to "prove" that they are really there, then you are never going to be able to believe in *anything* unobservable (atoms, extra-solar planets, etc.). Indeed, you won't believe in anything at all. You'll have to end up a solipsist, trying to twist and turn to reconceive things like science in light of that radical (unscientific) philosophical position.

And this is precisely the argument against MWI that began this thread. You believe in MWI, which posits (kinda) a single objective world that is very very odd and unfamiliar indeed. What possible reason could you have to believe in this? Well, if we leave aside "a priori revelations" (which we both reject as invalid, unscientific) the answer *must* be: observation. But all of those observations that could possibly be relevant are observations of familiar material objects like tables, chairs, cats, pointers, computer screens, etc. And so if none of those things really exist as such, the whole alleged chain of reasoning that leads you from them to MWI falls apart, it fails to connect at the first link. So any such argument for MWI (i.e., any argument which appeals ultimately to *observation*, i.e., any *scientific* argument) is self-defeating. That is why it's impossible to take MWI seriously as a scientific theory.

In other words, because I have not much confidence in any a priori philosophical requirements, I try to take the position in which I give as few a priori input from that side as possible.

Well it's scorched Earth for me: I accept *no* "a priori input". Including such things as: some preposterous definition of "consciousness" that is *not* based on empirical observation, the idea that there is rational grounds for doubt about the existence of tables and chairs, etc...

There is of course no scientific "proof" of MWI anymore than there could be a proof of Bohmian mechanics or anything else, given that they are all based upon ontological statements which are, by definition, philosophical positions, and not scientific ones. The only things that one can demonstrate scientifically, are epistemological concepts.

By which you mean: "subjective inner-theater impressions." So you are a solipsist masquerading as a scientist.

...if in the 30ies one would have gone for Bohmian mechanics (remember, no spin!), ...

Huh? Are you saying "spin" can't be incorporated into Bohm's theory? If so, you display your ignorance of the theory. It's trivial. Make the wave function a spinor, and replace the guidance formula with

v ~ Im[ (psidagger grad psidagger) / (psidagger psi) ]

and change the hamiltonian in the standard ways.

That's it. You get the right predictions for stern-gerlach, and everything else handled by the corresponding orthodox non-relativistic theory of spinning particles.

Or maybe you meant something else.

THIS is why I consider it as not a happy idea to fiddle with the formalism just for the sake of some philosophical position, but rather, to let the formalism speak for itself.

Those voices you hear in your head are not the formalism.

 

[vanesch]

If we're being careful with terminology, "indirectly observed" is a contradiction in terms. Quantum superposition effects have been *inferred* -- inferred from things that have been directly observed.

Correct.

But my point was to object to the specific thing you mentioned -- a human observer being in a superposition of two belief states. *That* has never been observed, and neither has anything been observed from which one could infer it.

Well, personally, I consider an EPR-kind of experiment as exactly such a situation. The only problem is that one had to ressort to a trick to get two human beings in a "different basis" wrt each other (which is necessary to get interference experiments): namely by having them entangle with two different basis expansions of the singlet state (by using spin analysers at different angles).

Typically, how does one determine quantum interference ? One looks at whether a statistical mixture gives the same predictions as the proposed interference. That is: we make a setup in which, say, two possible classical states are present (in one basis), and then one analyses a result. If that result can be obtained by a statistical mixture of the two classical basis states, then there is no proof of interference ; if, on the other hand, there is a difference, then there is interference.

In the double-slit experiment, that's what happens:
there are two slits, and the two classical states are: went through left slit, and went through right slit. Now, any classical statistical mixture of particles going through the left slit and going through the right slit, no matter what is their subsequent dynamics, will give you a whole possibility of pictures on the screen, but NONE OF THEM corresponds to an interference pattern. Hence, the observation of the interference pattern in the double-slit experiment is a proof of quantum interference.

Now, humans are too big objects to send then through a pair of slits, and the problem is that they quickly entangle with their environment and hence amongst themselves. As such, it is not easy to find two "classical states" of a human which we will analyse according to another basis.
But there is a trick! We can entangle a human with a spin measurement along one axis, and look ourselves at a spin measurement along another axis. If we start out with an entangled singlet state, then OUR "resulting state" will be a combination of classical states of that other human (the classical states of that other human are: saw up OR saw down, according to his axis).
Given the spacelike separation, we are also sure that no premature decoherence will take place.
Now, we have to make sure that *no statistical mixture of his states* is ever going to explain the entire "pattern of interference" (that is, the correlation tables with our outcomes!) observed. If that is the case, then we know that the human being underwent an interference effect, which is a pure quantum state effect. Well, Bell's theorem is exactly what is needed: Bell's theorem asserts that we cannot obtain a statistical mixture which will give us the entire "interference pattern" (the correlations).
As such, I claim that in an EPR experiment, we have in fact done an interference experiment on humans.

Ok, this has never been done, because the EPR effect is done by electronic means, and the temporal separation is too small for a genuine human to take notes of his observations, and "go and interfere with himself" when we observe him - but we take it that the extrapolation of an EPR experiment over, say, a few lightminutes with human observers would not essentially change the result.

This is about only interference experiment that is readily executable with humans with reasonable technology.

Yes.

You directly observe a chair ? Even if it is dark and so on ? Even if you don't have eyes, nerves or anything ? (because if the observation is direct, and is the proof of the ontology of the chair, it shouldn't depend upon observational conditions ! It is direct!)

Come on.

You observe the chair by means of the electromagnetic radiation -- but of course one doesn't observe *that*. One is completely unaware of it for a long time (until one takes some physics classes, or in terms of the development of history, until the 19th century or so).

Exactly. So it took quite some analysis to determine that what we subjectively experienced as a "direct observation" was a whole chain of physical processes. Illustrating that what one intuitively *thinks* is "direct observation" is a very complicated process.

Also, if you "directly observe" a chair in a very good hologram, is that chair there then really ? According to you, there REALLY ARE chairs inside a hologram.

Do you say hello to the little man in the mirror ?

No, one doesn't directly observe those. They are discovered much later by advanced scientific inference.

Exactly. Scientific discovery can show that what was long thought to be "direct observation" is in fact a totally different physical process, giving us the *illusion* of something real (and our brains are wired up to jump all these intermediate steps, and give us such an impression).

Claims which are obviously false to begin with don't require such "falsification".

Such certainties is where science ends and dogma begins.

The falsification is that the word "observation" actually means something, and we simply do not observe brain states. The vast majority of people have literally never observed a brain.

You mean that our sensations do not find their origin in brain activity ?

This is where we differ. You equate philosophy = ontology = arbitrary. But then practically everything in legitimate science is arbitrary made up bogus "philosophy", and what is *left* of science according to your conception is some ridiculous game of trying to account for "subjective experience" but without allowing yourself to believe ever that these experiences are experiences *of* anything. And that is a fundamental, fatal, philosophical flaw in your whole way of thinking about all of this. Consciousness *means* consciousness *of* *something*.

Ah ? What's that kind of an argument ? Where do you get that from ?
So you mean that the ontological question is evident ? That's a very remarkable philosophical statement ! As I said, it is ONE specific view, and it is called "naive realism". You are picking ONE SINGLE philosophical position upon the ontological question, and you claim that it is the one and only, and that everything else is *necessarily* bogus, evidently false, ...
I find that personally a very close-minded position.

To be *aware* of something, is to be aware *of something*. Consciousness without an object is a contradiction in terms. So your whole conception of science which is based on this fundamental philosophical error falls apart.

Now, THAT's an irrefutable argument !

Come on: you simply STATE your conclusion, and consider that as a proof that my position falls apart.

By contrast, my conception of science is also based on a philosophy. But mine is based on a valid philosophy, not an invalid one. (See, we disagree about whether philosophy = arbitrary, and hence about whether there can be such a distinction as good vs bad philosophy. Ironically, it's bad philosophy which makes you think there's no such difference.) Mine is based on a philosophy that is "scientific" (though that is admittedly an imprecise term here) in the sense of being based on empirical observation -- for example, the observations by which we arrive at basic concepts like "consciousness".

So in short, the argument is: I say something different than you, and because what I say is right, yours must be wrong. QED.

 

[vanesch]

Continued...

That's the problem here. It's just what I've been saying over and over again. You're convinced that (a) philosophy is just arbitrary crap and we shouldn't ever let it influence our scientific thinking, and (b) that you can prove that by appeal to certain philosophical doctrines which you regard as just obviously true beyond the shadow of any doubt.

I never say that MWI is true beyond any shadow of doubt!
I say that if what we know is quantum mechanics, then a NATURAL ontological view that goes with it is MWI, and moreover, if you take on that view, a lot of "difficulties" that one would otherways have, disappear.

As such, MWI is as good a view as any other. You want to demonstrate that MWI is necessarily a crap view. I think you cannot make such a statement.
However, you NEED to say that it is a crap view, because otherwise some concessions YOU make about science are much less necessary than they seem to be.

However, yes, ontology is essentially arbitrary. That is because solipsism (absence of ontology) is unfalsifiable. Understand this clearly: solipsism is entirely possible. You cannot have ANY scientific argument against it.
So any postulate of an ontology (which ADDS stuff to the empty-ontology solipsism view) is ARBITRARY. Indeed. But some are MORE USEFUL than others. Some hypotheses of reality are more helpful in organizing our subjective sensations. And most of our sensations are in agreement with the "naive reality" hypothesis. So that is, in daily life, a good working hypothesis. But understand this very well, because it is a philosophically well-established fact: ontology is never more than a hypothesis.

Don't you see the problem there? In (b) you confess that it is necessary to have a philosophical base for one's whole conception of the nature and goals of science, which in turn influences how one assesses specific things in science. But because of (a) you refuse to take *seriously* the task of then working out what philosophy is right, and what the right conception of science is. So you're caught in a vicious circle.

That is as erroneous an argument as the following:
"you confess that it is necessary to use a mathematical structure to build a scientific theory. But because you refuse to take seriously the task of working out (a priori) what must be the RIGHT mathematical structure, you are caught in a vicious circle"

But of course one doesn't know a priori what is the right mathematical structure ! Of course one doesn't know what is the right set of fundamental principles ! And of course one doesn't know what is the right philosophical ontology hypothesis ! One has to find out by doing observations, and to set up a whole which explains those observations ! THAT is science.
In as much as it is entirely open WHAT are the fundamental principles, and WHAT are the correct mathematical structures (build upon those principles), it is also entirely open WHAT must be the right ontology hypothesis.
Also, it is very well possible that different alternatives for each of these things are possible. In that case, it is a matter of taste and esthetical judgement to make a choice.

Again, ontology is a CHOICE. Given that it is unknowable (contrary to what you claim !), we can do with it what we want, in the same way as we can take the mathematical structure we want for a physical theory. Only, at the end of the day, the entire machinery must simply spit out the right subjective experiences (epistemology).

"There's a table in front of me." "Matter is made of atoms." "There's another planet beyond Uranus which is perturbing its orbit through gravitational forces." "Novae in the sky are caused by the core-collapse of a supermassive progenitor star whose core comes to exceed the Chandresekhar limit." "Genetic inheritance occurs through the mechanism of DNA splitting and recombination."

To you all of these are evidently "philosophical", not science.

On the contrary. But they are shortcuts for the actual, epistemological statements:

"my observations are mainly consistent with "a table in front of me" "
"my observations are mainly consistent with "matter is made of atoms" "
"..."

My observations include my "direct" sensory observations, sensory impressions of things I read/saw/... (books, TV, ...) and sensory impressions of contacts with other beings (stuff Alice said etc...).

As I said (that's why you have this strong desire to make it an "obviously true statement"), many many many of our sensations are in agreement with a "naive reality" hypothesis. But not all.

But look at what is left of science without these things! As a simple empirical statement based on looking at the history of thought and which things we use the word "science" to distinguish from which others, it is quite clear that your conception of "science" is simply *wrong*. You are fatally mis-classifying what is and what is not science.

No. Science is NOT about what things ARE. Science is about "observation". Science is the activity which helps us organize observations (relationships between observations). And observations are ultimately "subjective impressions". For a lot of science, we CAN make the hypothesis of naive realism. For daily life too. But, as I said, such an hypothesis is entirely arbitrary. For daily life, and a lot of science, the naive realism hypothesis is by far the simplest and most helpful. But not for quantum theory. There, it is better to change your hypothesis to another one.

But you see, you do. Even worse than I do. That we can't be sure whether there are really tables and cats, is a philosophical position

No, THAT is a philosophical FACT.

I don't agree. There is good and bad philosophy. I mean, even you know that there have been all sorts of conflicting philosophical positions put forward on all sorts of points. They can't all be equally right. I guess your view is that they're all equally wrong, equally empty, equally nothing, equally pointless.

There is no "correct" and "false" philosophy. There is "useful" and "less useful" philosophy. The only false philosophy is the refusal to do philosophy, that is, the refusal to re-consider certain "evident" positions, and the claim that certain answers are beyond doubt true.

Of course the Earth is flat, Zeus lives on the Olympus, the Earth is 6000 years old, and there exist chairs and tables. Of course space is 3-dimensional, Euclidean, and time is absolute. Of course.

But I completely and totally disagree. The issues (or at least some of them) are crucial, and are fundamental to science. We need answers to them. And so we need to distinguish the right answers from the wrong answers.

Yes, but guessing them a priori, based upon intuition, is maybe not the only way - or the best way - of getting the "right answers".

As to ontology: someone who starts their philosophy by saying "I just know a priori that there is a god, and that he is omnipotent, omniscient, and has really great hair to boot" is doing bad philosophy. Someone who starts their philosophy by saying "I know there are tables and chairs because I *see* them and I know I am conscious" is doing good philosophy.

If you say so

So then how the heck can you justify spending all this time arguing about it? How can you justify considering yourself a proponent of MWI? To you this is all just a pointless game, in which we know going in that there is no answer, no way to actually establish what is true, what the world is really like (even if it takes hundreds of years)? Not to me.

Well, nevertheless, THAT is a genuinly true statement. We don't know what the world is like, and we will never know it. There's nothing we know as absolutely true. We can only make working hypotheses, which have only that validity: they are working hypotheses, which help us to organize what we experience. If you would have studied the most basic elements of philosophy, you would know how much is fundamentally unknowable.

What you refuse to see is that philosophy doesn't necessarily have to be "a priori". I reject completely the idea of "a priori". I'm an empiricist. And yet I believe philosophy is important and valid. To you that's a self contradiction I guess -- because you refuse to see that all your beliefs are influenced by the philosophy *you* (unwittingly?) accept.

If you are an empiricist, then you should not have to have any ontological position at all. Empiricists work entirely within an epistemological framework.

But I completely agree with this. It's just that I think we can be 100% certain, based on what you call "epistemological knowledge" (by which I assume you just mean "empirical", based in observation), that there are tables and chairs and cats (not to mention extra-solar planets, atoms, dark matter, etc.). You disagree because you define epistemology/empiricism/experience differently, which is a *philosophical issue*. But you are blind to the fact that you take this radical philosophical position and that it actually influences everything you are saying. Everybody else has an accent.

No, you stubbornly frame yourself within naive realism, without considering any ontological positions. I didn't come to quantum mechanics with an MWI view ! Children are of course naive realists, because that is a simple hypothesis which works very well for most if not all experiences children encounter in their childhood. Hence, this is deeply rooted in our intuition. They also have a "simultaneity" intuition, and they also develop a good intuition for Euclidean space. But all this, again, because that is a hypothesis which works incredibly well for daily experiences. So, naive realism works well for most of that stuff.
But when one comes to more sophisticated stuff (in fact, ONLY in physics), then this hypothesis shows its limits. Until the 19th century, naive realism even worked well within physics. But then, we grew more sophisticated, and understood that this hypothesis is not tenable. It was the birth of modern physics. Some people couldn't get over it, and they became etherists, and Bohmians.

I agree, in so far as we are talking about questions of unobservables, things that have to be inferred from what is observed. There is no such debate over things that are directly observed. As an empiricist, I believe there is no possibly better warrant for believing something exists, than that I *see* it.

That is a very very naive position. Again: do you believe that there is a little man in the mirror which ressembles you ? Nevertheless, that is what you SEE when you look in the mirror.

Since any *other* warrant (some complex chain of scientific inference) has to be *based exclusively* on empirical/observational evidence, the end of such a chain could never be more certain than the things at its base. So if you don't think tables are real, if you don't think *seeing* them is enough evidence to "prove" that they are really there, then you are never going to be able to believe in *anything* unobservable (atoms, extra-solar planets, etc.).

Exactly. You don't *believe* in anything for sure ! That's the whole viewpoint! However, you can make working hypotheses which HELP you understand what you see. If I *see* a chair in front of me, I don't have to BELIEVE that there is a chair in front of me. However, MAKING THE HYPOTHESIS that there is a chair in front of me helps me coordinate my actions and my experiences. For daily life, it is often sufficient to make the simple hypothesis that what one sees is there. It works, most of the time (not always, as with holograms).

Indeed, you won't believe in anything at all. You'll have to end up a solipsist, trying to twist and turn to reconceive things like science in light of that radical (unscientific) philosophical position.

You are trying to label the position as "unscientific", but you do this only by stating that. You don't have a single argument. I'm not a solipsist. I consider solipsism as a good exercise in "ontology hypothesis building", but I'm in fact an "ontological agnost". I am deep down, convinced that the reality of the world is fundamentally unknowable. I think that anybody who claims anything else is a seriously deluded and naive person.

However, I do think that we have learned quite a lot ABOUT the world (without even approaching what it "really" is: maybe a big computer, the mind of a deity, a mathematical structure,... who knows ?). We have learned quite a lot about relationships between experiences, observations, all that.
And, depending on what kind of relationships we are dealing with, it is often nice to set up some (evidently erroneous) mental picture of how the world MIGHT BE LIKE. But again, I don't think we have the vaguest clue what it REALLY is like, so the picture - the ontology we set up in our mind - is evidently a kleenex picture. The thing we know most, is the formal machinery that gives us more or less correct relationships between experiences, and hence it is the best source of inspiration to set up a picture.

And this is precisely the argument against MWI that began this thread. You believe in MWI

No, I do not believe in MWI. I think that MWI is a good working hypothesis as an ontology when one does quantum theory. That's all. It MIGHT eventually be "true", but we will never know. But in this respect, it isn't any worse than any OTHER ontology hypothesis, which is just as uncertain.

What possible reason could you have to believe in this? Well, if we leave aside "a priori revelations" (which we both reject as invalid, unscientific) the answer *must* be: observation. But all of those observations that could possibly be relevant are observations of familiar material objects like tables, chairs, cats, pointers, computer screens, etc. And so if none of those things really exist as such, the whole alleged chain of reasoning that leads you from them to MWI falls apart, it fails to connect at the first link.

You are still making the same argumentation error as from the start. In order for making an ontology hypothesis (such as MWI, or solipsism, or naive realism, or whatever), OBSERVATIONS DON'T NEED TO BE ONTOLOGICALLY REAL. There is strictly no need "for a table to be ontologically real" in order for there to be a "subjective experience which is consistent with what we colloquially say 'there is a table'". I only need to have a coherent set of (subjective) observations, like visual impressions of tables, pointers and all that. From that, I AM FREE TO MAKE UP WHATEVER REALITY I LIKE, as long as, at the end of the day, this reality "generates" my coherent set of observations.

See, you are taking your OWN starting position as "evidently true" (namely, naive realism, in which observations correspond to "ontologically true things"), and then argue that ANOTHER position (in which observations and ontology are distinct), must be erroneous, given that ontology is different from observations, and (here's the error) given that you take it as evident that observations are ontologically true, observations in this other system are "false", and hence the thing is self contradictory.

Your argument has the following logic:

I believe A, and A contains a statement D

You believe B and B contains the statement ~D

(D is here: observations are ontologically real)

Now, I'm going to prove that B is wrong and that A is right.
Indeed, take B. In B you have ~D.
But given A, clearly D. Hence B is wrong.

By which you mean: "subjective inner-theater impressions." So you are a solipsist masquerading as a scientist.

First of all, a solipsist can just as well do science as a non-solipsist. There is no contradiction between being a solipsist and being a scientist. The solipsist considers science as a way to explore his subjective experiences, and makes no ontology hypothesis. The statement "really exists" has no meaning for him.

As I said, I'm not a solipsist, am an agnost. I think we cannot know what really exists. We can only make hypotheses. And, given the equivalence of (unknowable) truth value of those hypotheses, we should make those which suit us. But it shouldn't have any incidence on how we try to formalize relationships between observations - which is REAL science.
In daily life (and many activities), we can get away with "naive realism", but in certain parts of physics it is easier to make another hypothesis. It's FREE!

Huh? Are you saying "spin" can't be incorporated into Bohm's theory? If so, you display your ignorance of the theory. It's trivial. Make the wave function a spinor, and replace the guidance formula with

Spin can be incorporated in Bohmian mechanics all right, namely in the quantum mechanics part of it. But spin "is not real" in Bohmian mechanics. It doesn't correspond to "a real state" of the particle. A particle with spin, or one without spin, is the same particle in Bohmian mechanics. Only, you can ADD BY HAND some stuff in the wavefunction (which is only "half-real") and there: motion AS IF there was spin. This is why I say that you can ACCOMODATE quite a lot of stuff in Bohmian mechanics, but one first has to discover it OUTSIDE of bohmian mechanics, and then it can be imported.

Spin essentially comes about because one requires the field equation solutions to be a representation of the lorentz group. From that follows that one of the few possible field equations is the Dirac equation.
But in Bohmian mechanics, there is no a priori need to have any representation of any Lorentz group, given that relativity is dead. But nothing STOPS you from putting in something like the Dirac equation. Or something else. This is how Bohmian mechanics can accommodate for spin. Now, the Lorentz group being represented by solutions, you can then go further and consider G-bundles over spacetime. Requiring fields not only to be representations of the Lorentz group, but requiring them to be sections over a G-bundle, automatically gives you gauge invariance. It is a very similar trick as the way the Dirac equation was derived (and hence spin was derived). But in Bohmian mechanics, there is no way to require naturally any G-bundle structure, given that there is just Newtonian space and time, and hence, gauge invariance is not easily *required* in Bohmian mechanics. But of course, the specific field equations that *come out of the requirement of gauge invariance* can be put into Bohmian mechanics (after the fact), and you can *accommodate* in this way, gauge invariance.
Once it is derived in another paradigm, you can easily (or less easily) PUT IT IN BY HAND in Bohmian mechanics. But the paradigm of Bohmian mechanics wouldn't have suggested it.

 

[ttn]

I have nothing to add that I haven't already said 5 times, so I'll just leave it at that. It's clear that we have fundamental philosophical differences, and that these are the cause of our disagreements over MWI/Bohm, etc. For anyone watching this, *that* is probably the most important take-home message: don't believe it when someone tells you that philosophy doesn't matter, and that you can (and should) do physics without philosophy. It just isn't true. You can *try* to do physics without any kind of philosophical input or base, but you will *fail*, and will end up being influenced by whatever philosophy you accept by accident, by osmosis. And so you will be letting all this crap which you didn't scrutinize carefully and which you probably wouldn't accept if you did, influence the way you think about and do science. And we should all be able to agree that that is not a good strategy.

Oh, one other point about spin in Bohm's theory: your answer is funny, after all that accusing me of being a naive realist (which I'm not). You say that the way Bohm incorporates spin isn't sufficiently good, because it treats spin as "merely" a property of the wave function, not of the particles, and hence not really real -- whereas, I guess, it is just obvious to you that spin really is really real. So you're a naive realist about "spin" and that's why you think Bohm's way of accounting for the relevant *observations* isn't good enough. Sigh...

 

[Schrodinger's Dog]

I have nothing to add that I haven't already said 5 times, so I'll just leave it at that. It's clear that we have fundamental philosophical differences, and that these are the cause of our disagreements over MWI/Bohm, etc. For anyone watching this, *that* is probably the most important take-home message: don't believe it when someone tells you that philosophy doesn't matter, and that you can (and should) do physics without philosophy. It just isn't true. You can *try* to do physics without any kind of philosophical input or base, but you will *fail*, and will end up being influenced by whatever philosophy you accept by accident, by osmosis. And so you will be letting all this crap which you didn't scrutinize carefully and which you probably wouldn't accept if you did, influence the way you think about and do science. And we should all be able to agree that that is not a good strategy.

Oh, one other point about spin in Bohm's theory: your answer is funny, after all that accusing me of being a naive realist (which I'm not). You say that the way Bohm incorporates spin isn't sufficiently good, because it treats spin as "merely" a property of the wave function, not of the particles, and hence not really real -- whereas, I guess, it is just obvious to you that spin really is really real. So you're a naive realist about "spin" and that's why you think Bohm's way of accounting for the relevant *observations* isn't good enough. Sigh...

Well thanks to both you and Vanesch for a really interesting exploration of two very conflicting and different interpritations anyway .

In the UK everyone learns metaphysics as part of the Physics degree, it may not be a huge part, but from what I have seen all the good universities make physics students at least conversant about philosophy, I've dabbled myself, and I'm sure some of the philosophical tomes and discussions I have, will help me to prepare better more logically consistent material for my course.

To be honest no good student should absolutely take somebodies word for it about physics, I mean you learn it, you ponder it, you discuss the implications of it, but blindly accept? no one just robotically assumes everything there told is absolutely true and there are no holes or oddities in any interpretation,hypothesis, theory, etc. At least I hope not anyway, for the future sake of physics ask questions about everything I think is the best approach, even if you don't like the answers.

 

[setAI]

For anyone watching this, *that* is probably the most important take-home message: don't believe it when someone tells you that philosophy doesn't matter, and that you can (and should) do physics without philosophy. It just isn't true.

how ironic you would say this yet argue against the MWI- Philosophy IS important- Logic is important- that is rather the point of the MWI! any philosophy that does not contain a multiverse ontology is a BAD philosophy- bereft of fundamental logic- invoking yet ignoring demons that allow only a single causal structure- which is why the vast majority of TOEs and physical theories posit or assume a multiverse-

http://arxiv.org/abs/astro-ph/0302131

 

[vanesch]

I have nothing to add that I haven't already said 5 times, so I'll just leave it at that.

I also have that impression on my side

For anyone watching this, *that* is probably the most important take-home message: don't believe it when someone tells you that philosophy doesn't matter, and that you can (and should) do physics without philosophy. It just isn't true.

Ok, but there is a difference between what you call "philosophy" and what I call "philosophy". I also consider philosophy important, but rather as a QUESTIONING. You call philosophy the *answers* (or one single "good" answer) to that questioning.
To the question, and the ponderings "what is reality ?", "what is really there ?", "what can I know about what is there ?" - which I consider important philosophical ponderings, you retain only ONE correct answer, and call THAT philosophy.

To me, philosophy is a tool to try to liberate one from one's intuitions and certainties in order to question what has always been taken for "evident". To you, it seems to be the opposite: to carve in stone what you intuitively "know" already.

You can *try* to do physics without any kind of philosophical input or base, but you will *fail*, and will end up being influenced by whatever philosophy you accept by accident, by osmosis.
And so you will be letting all this crap which you didn't scrutinize carefully and which you probably wouldn't accept if you did, influence the way you think about and do science. And we should all be able to agree that that is not a good strategy.

I can read that phrase in exactly the opposite way as you intended it!

Again, taking a position of solipsism, naive realism, ... by itself is for me, not "doing philosophy". It is taking position on a philosophical question. What's important is the question, not the answer. What's important is the question of the relationship between ontology and epistemology.
So one should ask the question, and be aware that the answer to it is not as simple as one would intuitively think (the answer being that one cannot know, and hence must make a hypothesis. Making a specific hypothesis is then taking on a particular stance).

Oh, one other point about spin in Bohm's theory: your answer is funny, after all that accusing me of being a naive realist (which I'm not). You say that the way Bohm incorporates spin isn't sufficiently good, because it treats spin as "merely" a property of the wave function, not of the particles, and hence not really real -- whereas, I guess, it is just obvious to you that spin really is really real. So you're a naive realist about "spin" and that's why you think Bohm's way of accounting for the relevant *observations* isn't good enough. Sigh...

No, my point was: given that the ultimate motivation for even doing Bohmian mechanics is some form of naive realism, it is somehow a bit strange that the clearly observable "spin" is relegated to that uncertain realm of the wavefunction, of which Bohmians are a little bit annoyed giving it a status of reality (given that it lives over configuration space, and not over real space), and don't put it "hard-wired" into the particle. So even though spin really seems to be a "property of a particle", nevertheless it has been relegated to purely an effect of dynamics as given by the quantum potential.
As such, one can jokingly say that in Bohmian mechanics, there is some kind of MWI situation for spins The memory of hard disks is written in the wavefunction, and not in the position of the particles.

 

[ttn]

No, my point was: given that the ultimate motivation for even doing Bohmian mechanics is some form of naive realism, it is somehow a bit strange that the clearly observable "spin" is relegated to that uncertain realm of the wavefunction, of which Bohmians are a little bit annoyed giving it a status of reality (given that it lives over configuration space, and not over real space), and don't put it "hard-wired" into the particle. So even though spin really seems to be a "property of a particle", nevertheless it has been relegated to purely an effect of dynamics as given by the quantum potential.
As such, one can jokingly say that in Bohmian mechanics, there is some kind of MWI situation for spins The memory of hard disks is written in the wavefunction, and not in the position of the particles.

There are several deep confusions here, but (since I already said I wouldn't comment anymore!) I will only address one. But in a way it is the whole argument. You describe spin as "clearly observable." That's the whole thing. It is *not* observable. One does not observe the spin of particles any more than one observes their electric charge or weak charge. What one can observe directly is that certain spots on a piece of film in a certain kind of experimental situation turn black. One then *infers* (from this and a ton of other background knowledge, itself inferred ultimately, but not at all directly, from observations) the existence of spin. And it is completely reasonable that different theories would propose different models for what, exactly, spin is. There is no way of saying a priori that the Bohmian model of spin (which is entirely consistent with everything that is observed) is wrong, unless one is oneself being a naive realist about spin.

This relates also to your totally wrong accusation that I want to use philosophy to settle advanced questions in physics, like questions about the nature of "spin" or which quantum theory is true. That is not at all the case. Philosophy is a very delimited subject. It deals only with fundamentals, not that which requires any specialized scientific knowledge. It is not up to philosophy how to interpret the black spots in the Stern-Gerlach apparatus, nor is it up to philosophy to decide how to best interpret the collective evidence for (some type of) quantum theory. What *is* up to philosophy to decide is such questions as whether we can rely on our perception of pieces of film. That is a philosophic, not a scientific, question, because an answer is *completely presupposed* by science. You simply cannot do science if you regard it still as an "open question" whether or not our senses systematically deceive us. (At least, you can't do good science -- maybe you can do rationalistic a priori "science" in the style of Plato or Descartes... or some of the contemporary string theorists!) My whole point in this thread will have to be summarized by this remark: by the time we get to such advanced questions as which version of quantum theory might be true, certain earlier, fundamental, questions are already settled and are hence no longer on the table. For example, the existence of such things as tables! And the proof that this point of view is right, is the hierarchical nature of knowledge: you literally couldn't even get to the point of *asking* which version of quantum theory might be true, if you didn't already accept all of those fundamentals (and much more that is not philosophically fundamental, but is still cognitively prior to any such debate as Bohm vs MWI, e.g., that matter is made of atoms). This is what I keep pointing out, and it is the final and fatal flaw in MWI -- its advocates *do* tacitly presuppose certain things in the very formulation of the theory, indeed, in the very formulation of the questions the theory is supposed to address... but then the theory they propose explicitly contradicts those presuppositions, destroying its own foundation and leading to logical collapse. Evidently many MWI advocates are narrow minded rationalists, and hence fail to grasp that they need all these presuppositions -- i.e., they make them tacitly only, and never bother to examine their own thinking and make the assumptions explicit. But they are there nonetheless, and clear thinkers who understand and value genuine science will see them and reject MWI because of the circularity they give rise to for MWI.

 

[vanesch]

It deals only with fundamentals, not that which requires any specialized scientific knowledge. It is not up to philosophy how to interpret the black spots in the Stern-Gerlach apparatus, nor is it up to philosophy to decide how to best interpret the collective evidence for (some type of) quantum theory. What *is* up to philosophy to decide is such questions as whether we can rely on our perception of pieces of film. That is a philosophic, not a scientific, question, because an answer is *completely presupposed* by science.

This is where I don't agree. At no point, science requires any presupposition of a philosophical *position*. Every position can, at any moment, be put in doubt, even if previously we were quite convinced that it was acquired "for good". This is called "keeping an open mind".

You simply cannot do science if you regard it still as an "open question" whether or not our senses systematically deceive us.

In fact, you can. At no point you need, in science, to take any position on an ontological question. And you are still using that charged term "deceived". There is no DECEPTION in our senses. Our senses sense what they have to sense, and it is up to us to give some meaning to them. *The way we do that* is entirely up to us.
Again, in MWI, there is not more any deception in "seeing a table" than in "seeing a movie". We honestly "see a table". It is the shortcut to "there IS a table" that might need a slight modification. Slight. And in certain cases.

"We see a table" is science. There IS a table is a hypothetical model of ontology.

In science, at any moment, anything can become again an open question. It is the very definition of science: falsification. At no point, nothing is carved in stone. Not even things that were taken for granted since ages. And certainly not philosophical positions which don't have a direct relationship with science, such as ontological positions.

by the time we get to such advanced questions as which version of quantum theory might be true, certain earlier, fundamental, questions are already settled and are hence no longer on the table. For example, the existence of such things as tables! And the proof that this point of view is right, is the hierarchical nature of knowledge: you literally couldn't even get to the point of *asking* which version of quantum theory might be true, if you didn't already accept all of those fundamentals

I don't agree with that point of view. Science is not a linear accumulation of knowledge without putting in question what was previously acquired. The only thing that is needed, is then a NEW explanation of why the old "acquired" knowledge has seemed right to us.

If it was once acquired, once and for good, that the Earth was flat, and that one could not put this in doubt (even after generations and generations of people who were convinced that the Earth was evidently flat) by doing more sophisticated things (such as go sailing), then we would be wrong guided. If, after centuries of being convinced that one can say, when one "sees a table" that there "is a table", and then it turns out that this needs a modification (but in such a way, that in most of the cases, "there is a table" still gives a good account of all the observations), then so be it.

This is what I keep pointing out, and it is the final and fatal flaw in MWI -- its advocates *do* tacitly presuppose certain things in the very formulation of the theory, indeed, in the very formulation of the questions the theory is supposed to address... but then the theory they propose explicitly contradicts those presuppositions, destroying its own foundation and leading to logical collapse.

It is not because when you set up your telescope and so on, that you still assume that LOCALLY at the site, the Earth is flat, that observations with that telescope that make you conclude that the Earth is round, are fatally flawed, because you "used the contrary hypothesis in gathering the evidence for your round-earth theory".

In the same way, it is not because of the good agreement in most cases between observations "I see a table" and "there is a table" which are used for the practical setup of experiments on quantum theory, that this undermines it rethinking of an ontology.

It is your good right not to like MWI. I can understand people not liking it. But it is a flaw to think that your not liking becomes a logical flaw. The thing you point out is not a logical flaw at all. Out of MWI, one can derive all of classical mechanics just as well as in any other view on quantum theory. As such, this shows that observations in MWI are in most cases entirely compatible with the formalism of classical mechanics (in the right limits: macroscopic bodies in interaction with their environment), and as such, within MWI, one can use, in those right limits, all hypotheses (including ontology hypotheses) that went with classical mechanics. It will give the SAME OUTCOMES OF OBSERVATIONS. So MWI predicts exactly the same behaviour of a "table" as in classical mechanics. As such, all things that we derived "naively" using classical mechanics, concerning tables, ARE NOT CONTRADICTED in MWI. Tables (in the sense of: the coherent set of observations that correspond to what we usually call a "table") act in exactly the same way in MWI as in classical mechanics. All the properties of tables needed to do experiments, are also in agreement with the MWI view on "tables". As such, MWI doesn't (as you claim) render the observations done using tables invalid.

Again, what we call "table" is just a kind of name for an association of different observations (when it looks like a table, when it smells like a table, when it feels like a table, when we see it burn like a table ... , well, we CALL it a table). At no point, we need anything more to do science with tables.
MWI reproduces exactly this set of observations. Hence, in MWI, there are these coherent sets of observations which we call "tables", just as much as they are present in classical mechanics. So at no point, MWI is in contradiction with the table we needed to do our quantum experiments on.

This is analogous to the astronomer who found out that the Earth was round. It was not because, in setting up his telescope, he made locally the hypothesis of a flat Earth (and initially in his mind, the Earth was a large, flat disk), that his observations leading to his conclusion are undermined. However, he DOES need to provide for the LINK between the old paradigm (flat earth) and the new one (spherical earth): he needs to show that in the new paradigm (the spherical earth), one still HAS THE IMPRESSION of a flat earth, locally. The link is the big ratio between the human scale and the scale of the earth. In a series development around the place of observation, on the human scale, the Earth still looks quite flat.

So, observations made by using the old paradigm of a flat earth, led the man to conclude that his old paradigm needed a review. However, he understands that within the new paradigm, most of the old conclusions drawn from the old paradigm are still valid, except for a huge "difference in principle". He now also understands that most of his old observations (which made people conclude that the Earth was flat initially) are entirely compatible with TWO DIFFERENT "ontologies" (flat Earth and round earth). As such, the chosen ontology has, for most (human) purposes, not much influence. Actually, for most human activities on small scale, it is STILL A MORE USEFUL hypothesis to take on the flat Earth hypothesis. But for SOME observations (such as go sailing), one is better with the new paradigm.

It is exactly the same for MWI. There is no LOGICAL flaw.

 

[ueit]

My main issue with MWI is the fact that it doesn't give an answer to perfectly valid scientific questions like "why I measured electron’s spin as being up?".
The theory only says that there is another copy of me that measured the spin "down" but this is not an answer, not for me, neither for my copy.
If we accept this kind of "explanation" then we can safely say that we know everything.

Why the gravitational constant has the value it has?
Nothing easier. There are many worlds, each with a different g. We happen to live in this one, by chance.

I don't think that MWI is contradictory. It may be even true. But I don't see anything useful coming out of it.

The argument that we are forced to accept MWI because of EPR-Bell and relativity is wrong. As Vanesch pointed out in another thread, superdeterminism (which is nothing but the plain old determinism) is a valid approach. As a deterministic theory, Bohm's interpretation may therefore allow a local reformulation.

 

[vanesch]

My main issue with MWI is the fact that it doesn't give an answer to perfectly valid scientific questions like "why I measured electron’s spin as being up?".

In as much as this *sounds* like a scientific question, it isn't actually one. The scientific question is always "will I observe that...".

The theory only says that there is another copy of me that measured the spin "down" but this is not an answer, not for me, neither for my copy.
If we accept this kind of "explanation" then we can safely say that we know everything.

Why are you the person you are, and aren't you George Bush ?

Why the gravitational constant has the value it has?
Nothing easier. There are many worlds, each with a different g. We happen to live in this one, by chance.

This is in fact not MWI, but rather the Landscape in string theory.

I don't think that MWI is contradictory. It may be even true. But I don't see anything useful coming out of it.

The only thing "useful" that comes out of it, is to have an ontology which fits perfectly with the formalism of quantum theory as we know it, without any desire to fiddle with it. It is a kind of tranquilizer which helps you come to peace with the quantum formalism - and to help you develop some intuition for it. That's what "interpretations" are for. Peace of mind.

The argument that we are forced to accept MWI because of EPR-Bell and relativity is wrong. As Vanesch pointed out in another thread, superdeterminism (which is nothing but the plain old determinism) is a valid approach. As a deterministic theory, Bohm's interpretation may therefore allow a local reformulation.

We are absolutely NOT forced to accept MWI because of EPR-Bell! We are not forced AT ALL to accept any interpretation (and certainly not MWI). Only, EPR-Bell is there in the first place because of the quantum formalism. So why look for *another* explanation if we have a machinery already on paper which has made us put up with the situation in the first place! The reason I mention this is different. If all this discussion were not there, and if, from the start, one was to have an MWI-kind of view on quantum theory, then one could easily see an EPR-experiment as a kind of "confirmation" of quantum interference with macroscopic bodies: you entangle two macroscopic systems with different spin decompositions of a pair of entangled particles, and you do this at spacelike separation in order to be sure that they don't decohere immediately with one another. Then you let them "interfere" (calculate the correlations), and you show that this is statistically not possible without quantum effects.
That's typically the kind of experiment you do to make quantum effects manifest (which means: to demonstrate "superposition"). With small objects, you do this with a kind of double-slit experiment, but you can do other kinds of "interferrometry", like this one.
Of course it doesn't *prove* MWI (you can't prove any interpretational scheme). It would just be a kind of indication that "superposition of macroscopic systems seems to work too".

If, in Newtonian mechanics, you calculate the force on a planet, and find, from those calculations, that the orbit is then going to be an ellipse, then why would you want to look for *another* mechanism which could produce elliptic orbits ? The very formalism that gave you the orbit (the Newtonian force of gravity) can also serve as the explanation or the mechanism. So you imagine with your mind's eye that some "force" is pulling on a planet, and that as such, it follows the orbit it should. If you do Newtonian mechanics, it wouldn't come to your mind to think of that as a kind of "bending of spacetime" or "crystal ellipsoids on which the planets roll" or whatever: if you do Newtonian mechanics, you take "as real" the elements of the theory. You don't lie awake at night of what "mechanism" might be responsible for elliptical orbits which come out of the mathematical formalism.
Well, to me, MWI is just a similar kind of reasoning held wrt the unitary quantum formalism. That's all. It's just a picture to keep in mind, when working with a formalism. A kind of "image of a reality" that will do the trick. But the nice thing is that because it sticks closely to the formalism, that it helps you reason intuitively in quantum theory.

MWI will learn you nothing more than what is already in the quantum formalism. To me, it is the kind of "minimalistic" ontological picture that one can have. It simply gives you the "ease of mind" not to have the desire to change the formalism. In exactly the same way as the usual view of Newtonian mechanics doesn't give you any desire to change it.

 

[tehno]

http://video.google.com/videoplay?docid=-45154219728824809&sourceid=searchfeed%20

Lisa Randall talks about her book .She even answers some of really profund questions touching differences between physics and philosophy that you are discussing.Watch ,have fun and learn.

 

[ueit]

In as much as this *sounds* like a scientific question, it isn't actually one. The scientific question is always "will I observe that...".

OK, I'll reformulate:

"will I observe that the electron will go up or down in a Stern Gerlach device?"

MWI cannot answer that. (this is true about QM in general, but MWI, by accepting QM as complete, cannot be expected to give an answer, never).

Why are you the person you are, and aren't you George Bush ?

1. my parents' DNA
2. my father's name is not Bush
3. my parents did not put me the name George.

Why do you think this question is relevant?

This is in fact not MWI, but rather the Landscape in string theory.

Yeah, but the method is similar. It proves the theory logically consistent but it gives useless answers.

The only thing "useful" that comes out of it, is to have an ontology which fits perfectly with the formalism of quantum theory as we know it, without any desire to fiddle with it. It is a kind of tranquilizer which helps you come to peace with the quantum formalism - and to help you develop some intuition for it. That's what "interpretations" are for. Peace of mind.

The problem is that QM's formalism fails to explain some experimental results (like the exact moment of decay of an unstable particle). Therefore the theory must be amended or changed (by adding hidden variables, like in BM for example). Trying to save the theory by in spite of unexplained experimental data is not, IMHO, a good way to do science. We should not "come to peace" with the present situation but try to improve it.

We are absolutely NOT forced to accept MWI because of EPR-Bell! We are not forced AT ALL to accept any interpretation (and certainly not MWI). Only, EPR-Bell is there in the first place because of the quantum formalism. So why look for *another* explanation if we have a machinery already on paper which has made us put up with the situation in the first place!

Because the "machinery" we have does not give exact answers (like the spin of the particle detected at a specific detector. The obvious answer is that we have a statistical theory that should be amended.

The reason I mention this is different. If all this discussion were not there, and if, from the start, one was to have an MWI-kind of view on quantum theory, then one could easily see an EPR-experiment as a kind of "confirmation" of quantum interference with macroscopic bodies: you entangle two macroscopic systems with different spin decompositions of a pair of entangled particles, and you do this at spacelike separation in order to be sure that they don't decohere immediately with one another. Then you let them "interfere" (calculate the correlations), and you show that this is statistically not possible without quantum effects.

You need quantum effects only if you assume statistical independence between the choice of detection angle and the properties of the entangled particles. EPR proves this assumption wrong.

If, in Newtonian mechanics, you calculate the force on a planet, and find, from those calculations, that the orbit is then going to be an ellipse, then why would you want to look for *another* mechanism which could produce elliptic orbits ? The very formalism that gave you the orbit (the Newtonian force of gravity) can also serve as the explanation or the mechanism. So you imagine with your mind's eye that some "force" is pulling on a planet, and that as such, it follows the orbit it should. If you do Newtonian mechanics, it wouldn't come to your mind to think of that as a kind of "bending of spacetime" or "crystal ellipsoids on which the planets roll" or whatever: if you do Newtonian mechanics, you take "as real" the elements of the theory. You don't lie awake at night of what "mechanism" might be responsible for elliptical orbits which come out of the mathematical formalism.
Well, to me, MWI is just a similar kind of reasoning held wrt the unitary quantum formalism. That's all. It's just a picture to keep in mind, when working with a formalism. A kind of "image of a reality" that will do the trick. But the nice thing is that because it sticks closely to the formalism, that it helps you reason intuitively in quantum theory.

When Newtonian mechanics failed to explain observations it was replaced. Not so with QM. Here, it is assumed that the random character of the measurement results must be fundamental, therefore a question that doesn't comply with this assumption is deemed irrelevant. I maintain that such a view is unscientific. MWI goes along with it, saying that there is no reason whatsoever for the specific result you get in an experiment because there are other, "superposed", experimenters getting the other possible results. Once you assume MWI as true, it makes sense, but I think such an assumption goes against scientific progress.

MWI will learn you nothing more than what is already in the quantum formalism. To me, it is the kind of "minimalistic" ontological picture that one can have. It simply gives you the "ease of mind" not to have the desire to change the formalism. In exactly the same way as the usual view of Newtonian mechanics doesn't give you any desire to change it.

I agree with this, but I don't see any merit in this lack of desire to change QM.

 

[rewebster]

It's interesting to see a discussion between a person concerned in applied physics and another in theoretical physics.

 

[vanesch]

OK, I'll reformulate:

"will I observe that the electron will go up or down in a Stern Gerlach device?"

MWI cannot answer that. (this is true about QM in general, but MWI, by accepting QM as complete, cannot be expected to give an answer, never).

I think you fail to see the gist of what is "an interpretation" of a theory. It is not at all an extension, or a suggestion for *another* theory, but it is just that: an interpretation (a way of looking at/understanding/having some intuition for) a theory. Several "interpretations" of QM start with saying that QM cannot be completely correct and modify it. But that's, strictly speaking, not trying to give an interpretation of QM! That is: not accepting QM and trying to fiddle with it to make it suit your wishes.

As to the random character of QM, I don't see in which way that needs to be a problem. After all, there is no fundamental theory - and you don't seem to be bothered by it either - which tells you how things on the left side of the road should look if you know how things on the right side look. In the same way, there is no a priori reason why we should be able to have a theory which tells us how things "tomorrow" look when we know how they look "today". It is simply a property of nature that there is such a relationship, but the nature of that relationship doesn't, in any way, need to satisfy properties we made up for ourselves. In classical physics, there is indeed a form of determinism: if we know how things are today, then we know (in principle) how they are tomorrow. But that is a specific property of classical physics. And classical physics itself ALSO has "unknowable" things ab initio: you still DO need to say how things are today to know them tomorrow. In other words, classical physics doesn't tell you what initial conditions you should choose. So not everything is "known" in classical physics either.

Quantum theory gives us a relationship between observations, and that relationship is stochastic. From that fact alone, we cannot conclude that it is "incomplete": nature might be such that there is no way to know for sure. There doesn't *need* to be any unique and deterministic relationship.

Yeah, but the method is similar. It proves the theory logically consistent but it gives useless answers.

The answers are not useless. QM does give a lot of information, in the form of statistical distributions, which are observationally verified.

The problem is that QM's formalism fails to explain some experimental results (like the exact moment of decay of an unstable particle). Therefore the theory must be amended or changed (by adding hidden variables, like in BM for example).

There is no fundamental need that the information of such a moment is "present" in nature before the thing actually happens. Maybe, maybe not. Observational determinism doesn't need to be a principle of nature.

Trying to save the theory by in spite of unexplained experimental data is not, IMHO, a good way to do science. We should not "come to peace" with the present situation but try to improve it.

Well, if you CAN improve upon it, than you should do so. However, nor Bohmian mechanics nor anything else has ever come up with an *observational improvement* of quantum theory. So saying that the theory is internally deterministic, but fundamentally observationally random, is scientifically speaking, not any different from saying that the theory is random.

Because the "machinery" we have does not give exact answers (like the spin of the particle detected at a specific detector. The obvious answer is that we have a statistical theory that should be amended.

The obvious fact is that we have a working observationally stochastic theory. Maybe nature is such, or maybe it isn't. But it is not up to us to decide that, in an armchair. Imagine that nature has a truly stochastic element to it. You can look forever for your deterministic improvement, you will be looking in vain.

You need quantum effects only if you assume statistical independence between the choice of detection angle and the properties of the entangled particles. EPR proves this assumption wrong.

EPR doesn't prove this assumption wrong, because it is only one amongst many.
It is true that there is a conceptually very simple theory of nature which is deterministic and which doesn't give many interpretational problems: nature is a pre-filled bag of events. There is somewhere a huge list of events, which fill spacetime. There is no causality, no determinism, nothing of the kind, just a big list of everything that happened and will happen in the universe. There are no laws of nature apart from this list, which includes everything.
Now, that list can have funny properties, and one can start to think that there are causal relationships, because of the funny correlations that appear in that list, but all that is just by coincidence.
With such a view, every theory and its contrary are possible.

When Newtonian mechanics failed to explain observations it was replaced. Not so with QM.

No, it is not because Newtonian mechanics failed to predict the correct initial conditions (you need to put them in by hand!) that it was replaced. It was because it made predictions that were observed not to be so.
QM doesn't make predictions that are observed not to be true.

Here, it is assumed that the random character of the measurement results must be fundamental, therefore a question that doesn't comply with this assumption is deemed irrelevant. I maintain that such a view is unscientific.

I could say: "it is assumed that the need to give initial conditions must be fundamental, therefor a question that doesn't comply with this assumption is deemed irrelevant..."

MWI goes along with it, saying that there is no reason whatsoever for the specific result you get in an experiment because there are other, "superposed", experimenters getting the other possible results. Once you assume MWI as true, it makes sense, but I think such an assumption goes against scientific progress.

Again, an interpretation is not meant to go beyond the theory it interprets. It just wants to give a mental picture that "explains" the formalism. That's all. All the rest is not "interpretational" but rather "exploratory".

I agree with this, but I don't see any merit in this lack of desire to change QM.

The specific problem QM faces is that it seems difficult to set up a mental picture of it that doesn't require one to say that, deep down, something doesn't turn round as it should. Now, that's very nice, but there is not any satisfying replacement that keeps the power of the QM formalism (Bohmian mechanics comes close, but needs to kick out a very fundamental principle, namely, relativity, without anything to replace it with just as much predictive power). So MWI proposes a way to set up such a mental picture without that need. With MWI, you can develop an intuition for QM which goes with its formalism. When you USE the formalism, you can rely on an MWI view when you are a bit in doubt on exactly how to use it (as is sometimes the case in delayed quantum erasers and EPR situations). That's the only use of MWI!

It is not from interpretational issues that any progress will follow in any case. It is not from re-interpreting Newtonian mechanics that people came to relativity or anything. A new theory was build upon a new principle, and THEN people tried to find out how the link with Newtonian mechanics could be re-established. Personally, I don't think that much progress beyond QM will come from considerations in Bohmian mechanics. It is already conceptually difficult to get some correspondence with QFT, which is a working horse.

 

[rewebster]

For me, this discussion is what is unusual about laws, theories, interpretations, etc. in theoretical physics.

Debate is one of the most useful tools that I’ve found to expand an idea, or initiate a creative thought; whether it is with another person, or, if you want/can call it a ‘debate’, if the person is able, to examine and criticize one’s own thought patterns.

I personally use set theory, bell curve grading (how and where the thought fits into each idea and subset), logic (in the way of deductive and inductive reason, in using judgement and reason), and common sense (very personal as it relates differently to each person). And, yes, all of these can be personal and introspective when it comes to anyone’s (and my) philosophy; and, of course, each and every statement made (by anyone, including me, here) is a reflection of one’s personal belief systems as it relates to each and every area of a thought taken (transcribed) to words, and the function of time to present those thoughts (reflection time to present the thoughts in the most ‘logical’ and correct way).

Laws, theories, interpretations, etc. can be accepted seemingly TRUE, FALSE, or PARTIALLY TRUE (and, therefore, PARTIALLY FALSE); and ‘accepted’ could mean generally, personally, academically, scientifically, etc.;

---and, again, the ‘ideas’ of the interpretation of the ‘words’ and the ‘ideas' behind the words, ‘true’ and ‘false’ can be interpreted in different ways (the idea of interpretation of any of the ‘words’ used here will be a ‘given’ as such).

There could be another subset (one of many) under this of USEFUL, PARTIALLY USEFUL (and therefore, PARTIALLY USELESS) and USELESS. This could be viewed from the perspective of (some) applied physicists (technicians, researchers, engineers, some teachers, etc.).

(Nine possible subsets)

Theoretical physicists may have a subset of ACCEPTABLE, PARTIALLY ACCEPTABLE (and therefore, PARTIALLY UNACCEPTABLE), and UNACCEPTABLE.

(Nine possible subsets, or, if combined with both the above, twenty seven subsets)

“The sun rises in the east” could be considered by some to be TRUE and USEFUL and ACCEPTABLE. Others will automatically say it’s FALSE, and, maybe PARTIALLY USEFUL and UNACCEPTABLE.

If you (and you can) add ‘unknown’ or ‘not known’, ‘not yet known’ etc., it would add more subsets, but also indicate a level of doubt, lack of completeness, indecisiveness, etc.

The question I asked myself is ‘If a theory is only partially true to every circumstance (QM, relativity, MWI, etc.), as it is (they are); and, it is (they are) not (yet) THE total and complete “The Theory of Everything”, is it (are they), or can it be (could they be), therefore, totally false (a little lie is still a lie, for example)?'


I’m in the thinking that MWI is PARTIALLY TRUE, PARTIALLY USEFUL, and PARTIALLY ACCEPTABLE.

 

[ueit]

I think you fail to see the gist of what is "an interpretation" of a theory. It is not at all an extension, or a suggestion for *another* theory, but it is just that: an interpretation (a way of looking at/understanding/having some intuition for) a theory. Several "interpretations" of QM start with saying that QM cannot be completely correct and modify it. But that's, strictly speaking, not trying to give an interpretation of QM! That is: not accepting QM and trying to fiddle with it to make it suit your wishes.

Of course, it depends on how you define "interpretation". I don't think that it is necessary to assume QM as complete in order to give an interpretation. For example one can understand QM as a statistical theory, like thermodynamics.

As to the random character of QM, I don't see in which way that needs to be a problem. After all, there is no fundamental theory - and you don't seem to be bothered by it either - which tells you how things on the left side of the road should look if you know how things on the right side look. In the same way, there is no a priori reason why we should be able to have a theory which tells us how things "tomorrow" look when we know how they look "today". It is simply a property of nature that there is such a relationship, but the nature of that relationship doesn't, in any way, need to satisfy properties we made up for ourselves. In classical physics, there is indeed a form of determinism: if we know how things are today, then we know (in principle) how they are tomorrow. But that is a specific property of classical physics. And classical physics itself ALSO has "unknowable" things ab initio: you still DO need to say how things are today to know them tomorrow. In other words, classical physics doesn't tell you what initial conditions you should choose. So not everything is "known" in classical physics either.

To say that something is random is to say that it cannot have any explanation. A theory that proposes such a possition goes against the very idea of science. One cannot seriously accept "there is no answer" for an answer.

There can be a connection between the two sides of the road, but it is so complex that nobody can "reverse engineer" the causality chain.

Determinism is the most powerful idea behind science. Randomness is a dead end. Maybe it is true, but it is as usefull as the "brain in the vats" hypothesis.

Quantum theory gives us a relationship between observations, and that relationship is stochastic. From that fact alone, we cannot conclude that it is "incomplete": nature might be such that there is no way to know for sure. There doesn't *need* to be any unique and deterministic relationship.

I disagree. The fact that we cannot explain an experimental result is a strong indication that the theory is incomplete. Otherwise, no theory will ever be suspected as being incomplete. Just answer "it's random" to any question.

The answers are not useless. QM does give a lot of information, in the form of statistical distributions, which are observationally verified.

I'm not saying that QM is useless. Useless is an interpretation of it which takes "there is no answer" as a good answer.

There is no fundamental need that the information of such a moment is "present" in nature before the thing actually happens. Maybe, maybe not. Observational determinism doesn't need to be a principle of nature.

Sure, but one must assume it in order to do science. Otherwise, can you propose a scheme by which one can distinguish between pure random phenomena and deterministic but yet unexplained phenomena worthy of research?

Well, if you CAN improve upon it, than you should do so. However, nor Bohmian mechanics nor anything else has ever come up with an *observational improvement* of quantum theory. So saying that the theory is internally deterministic, but fundamentally observationally random, is scientifically speaking, not any different from saying that the theory is random.

There is a difference. We can be 100% sure that a theory based on fundamental randomness is a dead end. If something is random it cannot be explained. Other theories may (or may not) evolve.

The obvious fact is that we have a working observationally stochastic theory. Maybe nature is such, or maybe it isn't. But it is not up to us to decide that, in an armchair. Imagine that nature has a truly stochastic element to it. You can look forever for your deterministic improvement, you will be looking in vain.

This is true, but what else can we do? There is also the possibility that a proof against deterministic theories is found.

It is true that there is a conceptually very simple theory of nature which is deterministic and which doesn't give many interpretational problems: nature is a pre-filled bag of events. There is somewhere a huge list of events, which fill spacetime. There is no causality, no determinism, nothing of the kind, just a big list of everything that happened and will happen in the universe. There are no laws of nature apart from this list, which includes everything.
Now, that list can have funny properties, and one can start to think that there are causal relationships, because of the funny correlations that appear in that list, but all that is just by coincidence.
With such a view, every theory and its contrary are possible.

I do not hold such a view and I find it completely useless. My deterministic hypothesis concerning EPR is based on the assumption that the entangled particles can "read", locally, from the surrounding fields how they will be detected/measured in the future.

It should be possible to rewrite Bohm's theory in a local manner by describing each event as a function of an arbitrary state in the distant past. I wonder if such an attempt has ever been made.

QM doesn't make predictions that are observed not to be true.

That's why I think it is a good statistical theory.

I could say: "it is assumed that the need to give initial conditions must be fundamental, therefor a question that doesn't comply with this assumption is deemed irrelevant..."

But Newtonian mechanics can give you the initial conditions, granted that you measure the present conditions with an arbitrary high accuracy.

Again, an interpretation is not meant to go beyond the theory it interprets. It just wants to give a mental picture that "explains" the formalism. That's all. All the rest is not "interpretational" but rather "exploratory".

See my opinion above.

The specific problem QM faces is that it seems difficult to set up a mental picture of it that doesn't require one to say that, deep down, something doesn't turn round as it should. Now, that's very nice, but there is not any satisfying replacement that keeps the power of the QM formalism (Bohmian mechanics comes close, but needs to kick out a very fundamental principle, namely, relativity, without anything to replace it with just as much predictive power). So MWI proposes a way to set up such a mental picture without that need. With MWI, you can develop an intuition for QM which goes with its formalism. When you USE the formalism, you can rely on an MWI view when you are a bit in doubt on exactly how to use it (as is sometimes the case in delayed quantum erasers and EPR situations). That's the only use of MWI!

OK.

It is not from interpretational issues that any progress will follow in any case. It is not from re-interpreting Newtonian mechanics that people came to relativity or anything. A new theory was build upon a new principle, and THEN people tried to find out how the link with Newtonian mechanics could be re-established. Personally, I don't think that much progress beyond QM will come from considerations in Bohmian mechanics. It is already conceptually difficult to get some correspondence with QFT, which is a working horse.

I think QM is more like thermodynamics than Newtonian mechanics. Here, evidence for the atomic structure was found by expressing some laws of unknown origin as a statistical approximation of many particles' motion(the P-V-T relationship of gases for example).

 

[vanesch]

Of course, it depends on how you define "interpretation". I don't think that it is necessary to assume QM as complete in order to give an interpretation. For example one can understand QM as a statistical theory, like thermodynamics.

Well, that's not so easy! If you do so, you need to introduce a sample space over which a statistical uncertainty is defined ; in other words, you need to build a hidden-variable theory. The only known one is Bohmian mechanics, and you run in quite some troubles with relativity there. Moreover, in doing so, you've been fiddling with the formalism, just for sake of a principle which doesn't bring in anything new and predictive, but rather destroys a predictive principle (namely, relativity).

See, saying that a theory "is a statistical theory, like thermodynamics" already creates a very restrictive frame. MWI, on the other hand, says that quantum theory is indeed, something like "thermodynamics", but then the sample space is the *observer* sample space. And then, you do not need to introduce any new elements in the formalism, or to break the principle of relativity.
In other words, what's particular to QM (through MWI glasses), is to say that there is "statistical mechanics" on the observer side, and not on the system side.

To say that something is random is to say that it cannot have any explanation. A theory that proposes such a possition goes against the very idea of science. One cannot seriously accept "there is no answer" for an answer.

Again, random doesn't mean "just anything". Random is that strange concept in between "determined" and "totally unknown": namely: with statistical regularity, but individually unknown.

Determinism is the most powerful idea behind science. Randomness is a dead end.

Determinism is a principle like any other. It can hold, or it can't.

Otherwise, can you propose a scheme by which one can distinguish between pure random phenomena and deterministic but yet unexplained phenomena worthy of research?

Well, if a theory can give you the verifiable statistical distributions of phenomena, then that's already something quite worth while. Nothing should stop you to try to find anything that gives more information, but there is no guarantee that you can find such a thing. As I said, Bohmians didn't come up with anything that gives "finer" predictions than the statistical predictions of QM.

There is a difference. We can be 100% sure that a theory based on fundamental randomness is a dead end. If something is random it cannot be explained. Other theories may (or may not) evolve.

I'm pretty sure that, if ever there is a theory which does finer predictions than QM, it will be of a totally different nature. So the interpretations suggested by QM will not help in uncovering such a theory (in the same way as different interpretations of Newtonian mechanics didn't lead to relativity). Again, the interpretation of QM has not as a goal to go beyond it, just to give an mental picture of it.

This is true, but what else can we do? There is also the possibility that a proof against deterministic theories is found.

Cannot be, given that there *IS* a deterministic theory (the big list of events) that can describe all what happens. Only, we will need first to observe all events in the universe before we can write it down (and even then, the sheet of paper on which it is to be written doesn't fit in the visible universe).

I do not hold such a view and I find it completely useless. My deterministic hypothesis concerning EPR is based on the assumption that the entangled particles can "read", locally, from the surrounding fields how they will be detected/measured in the future.

And how useful is such a view when you do QM computations ? Don't confuse a wet dream of a would-be theory with something that gives you an actual picture that goes with actual calculations.

It should be possible to rewrite Bohm's theory in a local manner by describing each event as a function of an arbitrary state in the distant past. I wonder if such an attempt has ever been made.

See, that's a wet dream of a would-be theory (which has in fact not much to do with the quantum formalism).

But Newtonian mechanics can give you the initial conditions, granted that you measure the present conditions with an arbitrary high accuracy.

No, you didn't understand my objection. I said: one could also have the principle that a good theory doesn't need ANY INPUT, and can make predictions WITHOUT input (such as initial or final or boundary conditions).

You require a theory to be deterministic: meaning: if events on a spacelike surface are given, then you should determine uniquely what are the events on another spacelike surface. You do not accept that only statistical correlations of those events can be found. I give you an extreme alternative: NO correlations have to exist really and all those that we think we've found are spurious (the "big list" theory) ; on the other hand the "a single theory that gives you all events WITHOUT having to specify any initial conditions"

Is the "big list" theory (which doesn't need any input at all!):
- deterministic or
- totally random ?

From a PoV of principle, the "big list" theory is superdeterministic: you do not even need to specify initial conditions, it contains all events AS SUCH (and no statistical distributions or anything: you just look in the list what are the events in the year 3050, and you also read in the list how the dinosaurs became extinct).
But from a practical PoV, it is totally random, as there aren't any a priori regularities in the list of events. It cannot even predict statistical regularities. Given that we don't have the list, this theory is practically way worse than QM.

A deterministic theory is an intermediate: GIVEN a slice of events in the list, we can calculate the whole list. So, you've shifted the whole list into a single slice + a reasonably short (?) algorithm. A theory such as QM is also an intermediate: given a slice of events, we can calculate statistical distributions of events of another slice. Here, the algorithm doesn't allow you to reconstruct the list, but just to find correlations.
In the "superdeterministic" list, no algorithm needs to exist at all, that gives you either a deterministic OR a stochastic link between two slices. So in as much you consider the list itself as a "trivial but huge" algorithm, you have a superdeterministic theory, and in as much you consider the list as "necessary initial data" (and an empty algorithm), you have a totally random "theory" without any predictive value.

 

[ueit]

Vanesch, our disagreement comes from the principles we consider important in doing science.
We have a set of experimental observations that cannot be explain/predicted by our current quantum theory (like the moment of a radioactive decay).

There are different things one can assume when confronting them:

1. Nothing. Reality is a “bag of events”
2. Nothing. They are fundamentally random (from our subjective experience), cannot be explained by any mathematical algorithm.
3. Try to find a mechanism by which they are “produced”
4. ….
5. ….

It is my opinion that “3” is the good way of doing science. In spite of its problems, BM provides a framework to explore this possibility. MWI goes with “2” and nothing interesting can be expected from it, just as in the case of “1”.
I repeat that MWI may very well be true, just like the “bag of events” or “universe as computer simulation” hypothesis. But, starting from such an assumption is not of any use for scientific progress. The theory is a dead end.

Now, because you assume “2”, you see nothing wrong/incomplete about QM formalism and see any deviation from it as harmful. On the other side, “3” requires the formalism to be completed. If by doing so, we have to change other principles like relativity, so be it, as long as there is no conflict with the experimental evidence (one can simulate relativistic effects on an absolute frame).

I'm pretty sure that, if ever there is a theory which does finer predictions than QM, it will be of a totally different nature.

Why?

So the interpretations suggested by QM will not help in uncovering such a theory (in the same way as different interpretations of Newtonian mechanics didn't lead to relativity). Again, the interpretation of QM has not as a goal to go beyond it, just to give an mental picture of it.

Again, I think Newtonian mechanics is a bad analogy because it is not a statistical theory. Thermodynamics is a better example. Because a new theory must reduce to QM, trying to reproduce QM’s formalism from a hidden variable approach might be useful.

Cannot be, given that there *IS* a deterministic theory (the big list of events) that can describe all what happens. Only, we will need first to observe all events in the universe before we can write it down (and even then, the sheet of paper on which it is to be written doesn't fit in the visible universe).

OK, but at least a proof against a certain class of deterministic theories, of the Newtonian type, could be found. I think “the big list of events” is not deterministic in the usual understanding of the term as the present does not determine the future. It can be rejected on Ockham’s razor alone.

And how useful is such a view when you do QM computations ? Don't confuse a wet dream of a would-be theory with something that gives you an actual picture that goes with actual calculations.

It is the obvious conclusion when confronting EPR from a deterministic point of view. I cannot myself develop a theory as I lack the necessary math skills and knowledge. I only wonder if such a view has been disproved. It strikes me as odd that nobody seems to think about it.

Time to go home, I’ll continue later.

 

[vanesch]

Vanesch, our disagreement comes from the principles we consider important in doing science.
We have a set of experimental observations that cannot be explain/predicted by our current quantum theory (like the moment of a radioactive decay).

Although the exact moment of a decay cannot be explained by QM, its statistical properties can. I agree with you that it could a priori be conceivable that there is a theory that can say so, however, in 80 years of trying, no such evidence has ever been found (in other words, no empirical relation has ever been put forward that gave a more precise relationship than the statistical relationship given by QM). As such, for all we know - today, and this can change tomorrow - we have no empirical indication at all that there is such a thing as determinism.

The "principles that are important in doing science" are basically that observations are what matters. Well, no observational correlations have ever been discovered that are more precise than QM predictions. This was, remember, different with Newtonian mechanics. Before the advent of Newtonian mechanics, there were Kepler's laws, for the motion of planets. They were empirically based laws, which could give a precise correlation between positions "yesterday" and positions "tomorrow", even though the theoretical frame was not known. But for QM phenomena, no such empirical relations have ever been devised. Not that there haven't been attempts! The early literature is full of "attempts to violate the Heisenberg uncertainty relationships". They all fail.

There are different things one can assume when confronting them:

1. Nothing. Reality is a “bag of events”
2. Nothing. They are fundamentally random (from our subjective experience), cannot be explained by any mathematical algorithm.
3. Try to find a mechanism by which they are “produced”
4. ….
5. ….

Well, before even having any hope of formulating a general deterministic theory, one should have some observations that suggest it.

It is my opinion that “3” is the good way of doing science. In spite of its problems, BM provides a framework to explore this possibility. MWI goes with “2” and nothing interesting can be expected from it, just as in the case of “1”.
I repeat that MWI may very well be true, just like the “bag of events” or “universe as computer simulation” hypothesis. But, starting from such an assumption is not of any use for scientific progress. The theory is a dead end.

I agree. An interpretation of a theory is not a way to make progress, it is a way to get a feel for the theory at hand. This is why I don't bother, for instance, to try to incorporate quantum gravity in any MWI picture. There is simply no physical theory as of today which gives a good formal description of quantum gravity phenomena, so I don't think that "interpretations" of an existing theory should do what the theory itself cannot.

But let's be clear about something: EPR-Bell phenomena are perfectly well described by the formalism of QM. So the "secret" already resides in the QM formalism. One mustn't "go beyond" QM to "discover" them, they are already included into QM. So it would be very strange that an *interpretation* of this perfectly well predicted phenomenon by QM would need elements that are NOT included in said formalism. Nevertheless, these (well-predicted) QM phenomena seem to be ununderstandable for some. MWI is a view which helps one understand how the CURRENT QM formalism works, and comes to these predictions.

Now, because you assume “2”, you see nothing wrong/incomplete about QM formalism and see any deviation from it as harmful.

No, not at all. I consider the exercise of *interpreting* an existing theory as a totally different exercise from the exercise to go beyond the given theory.

There is a difference between "inventing new, speculative theories" or rather having wet dreams about would-be new theories on one hand, and trying to understand what we already have in our hands. I consider MWI in the last category. It is not a tool to go beyond QM. It is a tool to understand contemporary QM, including its strange predictions such as EPR-Bell and quantum erasers and so on - of which I repeat that they are perfectly well described by the CURRENT formalism (so all the knowledge is already included in this formalism!).

On the other side, “3” requires the formalism to be completed. If by doing so, we have to change other principles like relativity, so be it, as long as there is no conflict with the experimental evidence (one can simulate relativistic effects on an absolute frame).

Yes, but in order to save a "desired" principle which, as of today, doesn't bring in any new formal predictive power, we've then sloshed down the drain another principle which DOES have quite some formal predictive power. That's where I think that we lose some.

Why?

Historically, things always happened that way. The view on the old theory was never a good starting point to find a new theory. In fact, the view on the old theory has always *hindered* the correct conceptualisation of the new one. This was so with electromagnetism (mechanical "ether"), with relativity (Lorentz ether), with quantum theory (Bohmian mechanics), ...
Sticking to the old view on things has never been very productive or suggestive in the new paradigm. That's why I think that if it happens again, all our considerations concerning QM are to be dropped also.

Again, I think Newtonian mechanics is a bad analogy because it is not a statistical theory. Thermodynamics is a better example. Because a new theory must reduce to QM, trying to reproduce QM’s formalism from a hidden variable approach might be useful.

It might. Then, it might not.

OK, but at least a proof against a certain class of deterministic theories, of the Newtonian type, could be found. I think “the big list of events” is not deterministic in the usual understanding of the term as the present does not determine the future. It can be rejected on Ockham’s razor alone.

What I wanted to illustrate is that the separation into "algorithm" (or "laws of nature") on one hand, and "external data" (boundary conditions) is, up to a certain point, arbitrary. A very complex algorithm is difficult to distinguish from external data. How nature is put together is not to be decided in an armchair, but by observation and deduction.
"deterministic" theories have a rather simple algorithm, and need as external data the "initial conditions" on a spacelike surface. They are just ONE possible configuration for nature, but that doesn't need to be so.
There could be a single, universal algorithm with NO external data needed (no "initial conditions" needed). Or there could just be statistical relations. Or there could be nothing at all in the form of an algorithm (big bag of events) - this is already probably not the case, given that we already FOUND laws of nature of a rather simple kind. But it is not up to us to decide in advance what should be the kind of structure that nature has. We can only make observations, and try to find relationships between them (deterministic, statistical, whatever). That's science.

For instance, superdeterminism is also a "bad" hypothesis to do science. It would mean that we cannot discover any laws of nature, because all of our observations are biased in unknown but strong ways. All the "correlations" we find between different events are actually DIFFERENT correlations due to superdeterminism. It would be the end of observational science, given that every observation is going to be the result of a big conspiracy.

 

[ueit]

It should be possible to rewrite Bohm's theory in a local manner by describing each event as a function of an arbitrary state in the distant past. I wonder if such an attempt has ever been made.

See, that's a wet dream of a would-be theory (which has in fact not much to do with the quantum formalism).

I disagree. I think it is easy to show that a deterministic theory, like BM, can be reformulated in a local manner. For example, one could predict each spin measurement in an EPR experiment, let's say, one hour before the said experiment is actually performed, only from the initial conditions. Any trick, like using a "delayed choice" device is irrelevant, because the "choice" already exists, hidden in those initial parameters. So, we can interpret the so-called non-local interactions in terms of a local mechanism. An example is the local description of gravity in GR versus the non-local one in Newtonian theory.
So, I think BM is only an approximation to the "true", local theory.

Although the exact moment of a decay cannot be explained by QM, its statistical properties can. I agree with you that it could a priori be conceivable that there is a theory that can say so, however, in 80 years of trying, no such evidence has ever been found (in other words, no empirical relation has ever been put forward that gave a more precise relationship than the statistical relationship given by QM). As such, for all we know - today, and this can change tomorrow - we have no empirical indication at all that there is such a thing as determinism.

The "principles that are important in doing science" are basically that observations are what matters. Well, no observational correlations have ever been discovered that are more precise than QM predictions. This was, remember, different with Newtonian mechanics. Before the advent of Newtonian mechanics, there were Kepler's laws, for the motion of planets. They were empirically based laws, which could give a precise correlation between positions "yesterday" and positions "tomorrow", even though the theoretical frame was not known. But for QM phenomena, no such empirical relations have ever been devised. Not that there haven't been attempts! The early literature is full of "attempts to violate the Heisenberg uncertainty relationships". They all fail.

First, I'm not so sure that evidence for patterns in the data was seriously looked for (I've seen complains about the lack of raw, "uncleaned" data from various experiments). Second, we simply don't have the same data about radioactive decay as we did for planetary motion. For example, we don't know the charge or mass distribution inside of an atomic nucleus that is ready to "blow up". We don't know the detailed structure of the electron cloud in the place where a tunneling has happened. So, it's not unexpected that a pattern was not observed.

AFAIK Heisenberg uncertainty applies only to predictions, not to past observations. For example we can determine with unlimited accuracy both the momentum and position of a particle simply by detecting it arbitrary far away from the source. We cannot use this result to predict its future behavior, but this has nothing to do to the random/determined character of its motion.

Well, before even having any hope of formulating a general deterministic theory, one should have some observations that suggest it.

We have two types of experiments:

1. we start with 100% identical systems (like two atoms produced from a diatomic molecule) and we get identical measurements. (this points to determinism)

2. we start with unknown initial parameters end get random results.

Do you think that "2" points to randomness at fundamental level? If so, why?

There is a difference between "inventing new, speculative theories" or rather having wet dreams about would-be new theories on one hand, and trying to understand what we already have in our hands. I consider MWI in the last category. It is not a tool to go beyond QM. It is a tool to understand contemporary QM, including its strange predictions such as EPR-Bell and quantum erasers and so on - of which I repeat that they are perfectly well described by the CURRENT formalism (so all the knowledge is already included in this formalism!).

OK.

For instance, superdeterminism is also a "bad" hypothesis to do science. It would mean that we cannot discover any laws of nature, because all of our observations are biased in unknown but strong ways. All the "correlations" we find between different events are actually DIFFERENT correlations due to superdeterminism. It would be the end of observational science, given that every observation is going to be the result of a big conspiracy.

I think we have a different understanding of superdeterminism. IMO, any deterministic theory (classical physics, MWI, BM) is superdeterministic, that is, no free-will. In fact I see no trace of evidence, from QM or any other branch of science, that would give a foundation for free-will. You need a sort of mind/brain dualism for that.
I fail to see why a determined "choice" implies a "conspiracy", or biased observations. There is no reason to assume that the experimental data is not representative. We have to accept however that there might be experiments that cannot be done. For example, you cannot "fool" a particle in a EPR experiment. But you cannot "fool" gravity or conservation laws either.

 

[vanesch]

I disagree. I think it is easy to show that a deterministic theory, like BM, can be reformulated in a local manner.

No. It is easy to show that an unknown theory, for which there is a common cause of the settings of the analysers (in other words, in which there is a common cause to the settings of the analysers of Alice, Bob, and of the pair production) doesn't have a problem with Bell, because one of the assumptions of Bell's theorem is not satisfied.

But the theory is still unknown! Can you figure out a theory in which all the nitty-gritty details are explained on how it came about that Alice decided to set exactly THAT analyser setting which she had to set ?
I mean, it is not sufficient to say that, because in a deterministic theory, there is indeed no free will and whatever Alice will set WAS predetermined, that it is also THE CORRECT VALUE of the setting! You have to show that the *correct* settings at Alice and Bob have to come out! Did you ever hear of any such derivation which shows that the complicated (deterministic) process in the brain of Alice and so on, cannot but result in exactly that correct setting which will lead to the (illusion of) EPR correlations ?

So I stick to my claim of a wet dream of a non-existing would-be theory.

For example, one could predict each spin measurement in an EPR experiment, let's say, one hour before the said experiment is actually performed, only from the initial conditions. Any trick, like using a "delayed choice" device is irrelevant, because the "choice" already exists, hidden in those initial parameters. So, we can interpret the so-called non-local interactions in terms of a local mechanism. An example is the local description of gravity in GR versus the non-local one in Newtonian theory.
So, I think BM is only an approximation to the "true", local theory.

Yes, but there is a difference between saying that such a thing could in principle be possible, and propose an actual theory in which one can demonstrate that *THIS* is what will happen ! Do you realize the complexity of such a feat ? Irrespective of the specific physical setup, all small interactions will ALWAYS, in many different circumstances, conspire such that exactly that "choice" is made which makes us think that there are correlations!

 

[ueit]

But the theory is still unknown! Can you figure out a theory in which all the nitty-gritty details are explained on how it came about that Alice decided to set exactly THAT analyser setting which she had to set ?
I mean, it is not sufficient to say that, because in a deterministic theory, there is indeed no free will and whatever Alice will set WAS predetermined, that it is also THE CORRECT VALUE of the setting! You have to show that the *correct* settings at Alice and Bob have to come out! Did you ever hear of any such derivation which shows that the complicated (deterministic) process in the brain of Alice and so on, cannot but result in exactly that correct setting which will lead to the (illusion of) EPR correlations ?

First, you speak about the "illusion of EPR correlations". I don't think this is apropriate. The correlations are real and "enforced" by the deterministic law, like gravity. They are inevitable.

Yes, but there is a difference between saying that such a thing could in principle be possible, and propose an actual theory in which one can demonstrate that *THIS* is what will happen ! Do you realize the complexity of such a feat ? Irrespective of the specific physical setup, all small interactions will ALWAYS, in many different circumstances, conspire such that exactly that "choice" is made which makes us think that there are correlations!

I think there is another way to look at this problem, by focusing not on Alice's or Bob's brain but on the entangled particles.

Let's say that the total force acting on the particle source is represented by the function f(t) = d1(t) + d2(t), where d1 and d2 correspond to the detectors' state at time t (by "state" I mean any field comming from them, gravitational, EM, weak, whatever). I assume that no other object interferes with the experiment.
Because d1, and d2 evolve deterministicaly, their state at any future time can be known at source's position because of f(t).
We can now postulate that the the entangled particles are "produced" only when the measurement orientation, at the time of detection (which can be determined from f as well), is in accordance with QM's prediction.

 

[ttn]

I just skimmed the recent posts on this thread and wanted to make one comment.

ueit, you seem to miss (or unfairly minimize) the distinction between a merely deterministic theory, and a super-deterministic theory. The relevant point for this distinction is the idea of "external fields". An external field is a field which has causal influences on the beables of a theory, but which is not itself fixed by those beables. Most familiar physical theories have external fields: for example, the charge and current distributions can be external fields in classical E&M (though they can also be included dynamically in the theory), simple QM usually allows external electromagnetic potentials to be set, QFT allows coupling to external sources, etc. Indeed, it is hard to think of an example of a real theory (as opposed to a dream, like string theory... perhaps vanesch would call this a "dry dream" since it hasn't yielded any pleasurable results?!) which doesn't contain such external fields. And the reason for this is clear: scientific theories must be testable if they are going to be believed, and "external fields" are the way that theories leave room for experimenters. Without external fields, it is extremely difficult to imagine how we could test a theory -- or more precisely, it is extremely difficult to understand how the theory would permit something which we could validly describe as a test of the theory. (It'd be like a randomized drug trial in which the assignment of pills to patients was made by the pills themselves -- even if, in the end, the placebo patients did worse than the drug patients, it would be impossible to infer that the drug actually helped those patients, i.e., it would be impossible to believe that we had actually *tested* the drug.)

The point is: there are many extant examples of deterministic theories. But all of these leave room for "free human experimenters" in their external fields. So it is very misleading when you suggest that the EPR-Bell apparent statistical evidence for non-locality, can be explained away if we merely posit instead a deterministic theory. What you actually need to posit is instead a *superdeterministic* theory, i.e., a theory in which the kinds of things we normally (in science) think of as being "freely or randomly settable", actually *aren't* "freely or randomly settable". So when Weihs et al set up quantum random number generators to determine along which axis a given photon's polarization is measured, you have to believe that that random number generator is actually not random at all (with respect to the state of the incoming photon and whatever else it happens to be entangled with). Rather, by some gigantic cosmic conspiracy, whatever factors are determining the output of the random number generator, are also determining the state of the photon pair (or, I guess, since you want to preserve locality, the factors which immediately determine the output of the random number generator are determined/influenced by some other thing in the distant past which *also* turns out to the relevant thing for influencing the state of the photon pair). And as if that we're insane enough, you have to hold that this magical cosmic conspiracy is clever enough to magically work out exactly the same way, even if the random number generator is switched out in favor of some completely different process, such as a computer running a "random number" algorithm, a young child flipping coins, a human making last-minute "random free-will choices" (with scare quotes because, in superdeterminism, there can't actually be genuine freewill), a chimpanzee throwing either even or odd numbers of poop projectiles, etc. The point is, in order to take your idea seriously, you need to be able to construct a theory in which some causal influence from the distant past influences *all* of these sorts of things, and in just exactly the right way so as to correlate the apparatus settings (which are determined by one of these silly methods) and the state of the photon pair, so as to later fool us into believing that (a) a genuine empirical test of Bell's inequality has occurred and (b) that the outcomes violated the inequality. Or at very least, you have to be able to give at least the hint of some kind of plausibility argument that maybe all of these things *could*, in principle, be so influenced as to bring about the results in question. Without this, all you have is a conspiracy theory. And so it is no better than if you said, about some randomized drug trial which showed strong correlation between being given the actual drug and feeling better later, "I don't believe it because maybe the allegedly-random assignment of pills to patients wasn't random at all, but was somehow magically biased by some causal factors in the distant past which caused the assignment to somehow or other be correlated to the prior health of the patient." Yeah, "maybe." But in the absense of a single shred of evidence to suggest this, it is scientifically meaningless.

This is why, as vanesch keeps saying, it's not enough to just say (in the Bell case) "maybe the allegedly-random setting of apparatus orientations wasn't random at all..." There is strong empirical reason to think that the orientations are indeed random enough for the purposes at hand here. So the burden is on you to explain how -- all evidence accumulated so far to the contrary notwithstanding -- these things could actually have gotten correlated up in the necessary way. And doing that means providing an actual example of a theory which predicts this, a super-deterministic theory. And as vanesch has said, this is just a wet dream. Nobody has such a theory. Indeed, as I started out saying, nobody really has even any idea what such a theory might look like, and how such a thing, if it existed, could even be considered as a scientific theory (since it is highly questionable that it could even be rendered empirically testable). And so your idea for a local explanation of the relevant experiments here turns out to be a lot like string theory -- (paraphrasing Peter Woit) not even a wet dream.

 

[ueit]

ueit, you seem to miss (or unfairly minimize) the distinction between a merely deterministic theory, and a super-deterministic theory. The relevant point for this distinction is the idea of "external fields". An external field is a field which has causal influences on the beables of a theory, but which is not itself fixed by those beables.

Any "merely deterministic" becomes superdeterministic when applied to those "external fields", therefore there is no real difference between the two. If BM for example is true then everything in this universe is "fixed" since the big-bang. Free will (defined here as the possibility of multiple choices) is an illusion because there is really only one option, the one determined by the previous state. Assuming both determinism and free external fields is logically contradictory (at least when forces with infinite range, like gravity or EM are described). Sooner or later this contradiction will lead to "paradoxes". It is my opinion that these paradoxes should be dealt with not by abandoning locality (which is required by relativity) but by accepting that the "external field" assumption is false.

Indeed, it is hard to think of an example of a real theory (as opposed to a dream, like string theory... perhaps vanesch would call this a "dry dream" since it hasn't yielded any pleasurable results?!) which doesn't contain such external fields. And the reason for this is clear: scientific theories must be testable if they are going to be believed, and "external fields" are the way that theories leave room for experimenters. Without external fields, it is extremely difficult to imagine how we could test a theory -- or more precisely, it is extremely difficult to understand how the theory would permit something which we could validly describe as a test of the theory. (It'd be like a randomized drug trial in which the assignment of pills to patients was made by the pills themselves -- even if, in the end, the placebo patients did worse than the drug patients, it would be impossible to infer that the drug actually helped those patients, i.e., it would be impossible to believe that we had actually *tested* the drug.)

The GR theory did not require "external fields" to be tested by comparing its predictions relating the orbit of Mercury with what it was observed. Not all theories can be tested in a controlled environment but this doesn't make them useless.

The point is: there are many extant examples of deterministic theories. But all of these leave room for "free human experimenters" in their external fields.

They "leave room for free human experimenters" only with the price of their logical consistency. You cannot have both determinism and multiple choices at the same time.

So it is very misleading when you suggest that the EPR-Bell apparent statistical evidence for non-locality, can be explained away if we merely posit instead a deterministic theory. What you actually need to posit is instead a *superdeterministic* theory, i.e., a theory in which the kinds of things we normally (in science) think of as being "freely or randomly settable", actually *aren't* "freely or randomly settable". So when Weihs et al set up quantum random number generators to determine along which axis a given photon's polarization is measured, you have to believe that that random number generator is actually not random at all (with respect to the state of the incoming photon and whatever else it happens to be entangled with). Rather, by some gigantic cosmic conspiracy, whatever factors are determining the output of the random number generator, are also determining the state of the photon pair (or, I guess, since you want to preserve locality, the factors which immediately determine the output of the random number generator are determined/influenced by some other thing in the distant past which *also* turns out to the relevant thing for influencing the state of the photon pair). And as if that we're insane enough, you have to hold that this magical cosmic conspiracy is clever enough to magically work out exactly the same way, even if the random number generator is switched out in favor of some completely different process, such as a computer running a "random number" algorithm, a young child flipping coins, a human making last-minute "random free-will choices" (with scare quotes because, in superdeterminism, there can't actually be genuine freewill), a chimpanzee throwing either even or odd numbers of poop projectiles, etc. The point is, in order to take your idea seriously, you need to be able to construct a theory in which some causal influence from the distant past influences *all* of these sorts of things, and in just exactly the right way so as to correlate the apparatus settings (which are determined by one of these silly methods) and the state of the photon pair, so as to later fool us into believing that (a) a genuine empirical test of Bell's inequality has occurred and (b) that the outcomes violated the inequality. Or at very least, you have to be able to give at least the hint of some kind of plausibility argument that maybe all of these things *could*, in principle, be so influenced as to bring about the results in question. Without this, all you have is a conspiracy theory.

In my previous post I've provided a sketch of a hypothesis that overcomes the difficulties you've raised. I only need the followings to be true:

1. The detectors (with everything that influences them like computers, humans, monkeys, whatever) are governed by a deterministic law (their future is fixed by their present state). This is true for every deterministic theory.

2. The state of the detectors can be inferred at the source by means of the known fields. (this is true about gravity, not sure about EM field though)

3. Particle pairs are produced only when the detectors have a "favorable" state, allowing the measurements to comply with QM's prediction.

I have to insist here that I do not claim that EPR correlations are false but we are predetermined to see a biased sample (a conspiracy theory). I think they are true, and they are enforced by the way the entangled particles are produced at the source.

This is why, as vanesch keeps saying, it's not enough to just say (in the Bell case) "maybe the allegedly-random setting of apparatus orientations wasn't random at all..." There is strong empirical reason to think that the orientations are indeed random enough for the purposes at hand here. So the burden is on you to explain how -- all evidence accumulated so far to the contrary notwithstanding -- these things could actually have gotten correlated up in the necessary way. And doing that means providing an actual example of a theory which predicts this, a super-deterministic theory. And as vanesch has said, this is just a wet dream. Nobody has such a theory. Indeed, as I started out saying, nobody really has even any idea what such a theory might look like, and how such a thing, if it existed, could even be considered as a scientific theory (since it is highly questionable that it could even be rendered empirically testable). And so your idea for a local explanation of the relevant experiments here turns out to be a lot like string theory -- (paraphrasing Peter Woit) not even a wet dream.

See my idea about such a theory above.

 

[ttn]

2. The state of the detectors can be inferred at the source by means of the known fields. (this is true about gravity, not sure about EM field though)

Suppose the state of the detectors is set by the even-ness or odd-ness in the millionth digit of the energy of some randomly selected CMBR photon. Of course, this photon was emitted in some specific process 15 billions years ago 15 billion light years away. And the past light cone of that emission event does (in the very remote past) overlap with the past light cone of the event at which the particle pair (to be measured) is emitted by the source. So think about what you are saying here: it's not just that "the state of the dectors can be inferred at the source by means of the known fields", but that some truly incomprehensible set of events 10s of billions of years ago has magically set things up so that the particle-pair-emission event and the CMBR photon emission event (events which happen 15 billion light years apart from each other) are correlated -- and not just correlated in any old way, but correlated so that the millionth decimal place in the energy of the one has some connection with the state of the emitted pair.

So you'll have to let us know when you actually produce a theory which explains how this could come about.

3. Particle pairs are produced only when the detectors have a "favorable" state, allowing the measurements to comply with QM's prediction.

Again, you state it misleadingly. It's not just that "particle pairs are produced only" in some favorable circumstances, but that events in the remote remote past have been contrived to produce (by mechanisms which you cannot name and merely envision in the wee hours of the night) correlations between the emitted particle pairs and pretty much everything else in the universe (incoming CMBR photons, the poop-throwing behavior of monkeys, etc). But seriously. There was some lucky bunching of free quarks in the goop 20 billion years ago, which caused a monkey to throw an even number of poops at 3:00 PM on a Tuesday at Fermilab? Give me a break. It's not science. It's a conspiracy theory, except that it's not even a theory but a wet dream.

But that's the last time I'll try to argue that here. The burden is clearly on anyone who advocates this kind of idea to put up or shut up.

 

[ueit]

Suppose the state of the detectors is set by the even-ness or odd-ness in the millionth digit of the energy of some randomly selected CMBR photon. Of course, this photon was emitted in some specific process 15 billions years ago 15 billion light years away. And the past light cone of that emission event does (in the very remote past) overlap with the past light cone of the event at which the particle pair (to be measured) is emitted by the source. So think about what you are saying here: it's not just that "the state of the dectors can be inferred at the source by means of the known fields", but that some truly incomprehensible set of events 10s of billions of years ago has magically set things up so that the particle-pair-emission event and the CMBR photon emission event (events which happen 15 billion light years apart from each other) are correlated -- and not just correlated in any old way, but correlated so that the millionth decimal place in the energy of the one has some connection with the state of the emitted pair. So you'll have to let us know when you actually produce a theory which explains how this could come about.

I’ll make an analogy with gravity. We have two theories:

1. Newtonian gravity (non-local, the force is assumed to propagate instantaneously)
2. GR (local, the changes in space curvature propagate at c)

An analogous experiment would be set up this way:

The “source” is an asteroid pair. The “detectors” are two galaxies, each 1 bln. parsecs away from the “source”. Now, in order for the two asteroids to leave their orbit towards the “detectors”, it is necessary that the stars in those galaxies to be in a certain relative position (otherwise, the resultant force is too weak).

From a Newtonian point of view it looks like the force between “detectors” and “source” acts instantaneously. Once the galaxies have a certain internal structure the asteroids start flying towards them. However, from a GR point of view, the two asteroids follow the space curvature, “carved” by the two galaxies 1 bln years ago, WHEN NONE OF THEM HAD THE REQUIRED STRUCTURE.
This example is quite similar with my hypothesis and it shows that the later is not such absurd as you might think.

Again, you state it misleadingly. It's not just that "particle pairs are produced only" in some favorable circumstances, but that events in the remote remote past have been contrived to produce (by mechanisms which you cannot name and merely envision in the wee hours of the night) correlations between the emitted particle pairs and pretty much everything else in the universe (incoming CMBR photons, the poop-throwing behavior of monkeys, etc). But seriously. There was some lucky bunching of free quarks in the goop 20 billion years ago, which caused a monkey to throw an even number of poops at 3:00 PM on a Tuesday at Fermilab? Give me a break. It's not science. It's a conspiracy theory, except that it's not even a theory but a wet dream.

While I agree that my hypothesis is more like a “wet dream” than a theory, your criticism is not, IMHO, well founded. You assume that physics is somehow scale-dependant as you think that by using more distant or complex detectors would change anything. I think this assumption is wrong. If BM (or other deterministic theory) is right it is irrelevant how far or how old is a system. You simply replace the value of time or coordinate parameter.

 

[reilly]

With all due respect, much of the discussion here, has little to do with physics. Rather it's about philosophy, in which there is seldom a right answer, and thus everyone has great freedom to pontificate, and argue about the maybe.

What so many people, at least in this forum, fail to realize is that physics is phenomena driven -- Nature provides puzzles, scientists try to solve them, ideally with simple math and elegant experiments -- and now with experiments run as if they were the province of small corporations.

With all due respect to the geniuses of String Theory, they are still in business 'cause there's no data to prove or disprove their arguments. With such a good deal, a new priestthood has been born, with hopes of eventual redemption. But now, they are free to do virtually anything, free from the difficult constraints of lot's of data.

Quantum theory, at every level, was born to explain, to provide understanding of very strange, classically impossible phenomena. Now we even have such gems as MWI, and Bohm's gallent efforts to turn back the clock on QM, and who knows what else. The problem with these efforts is that they seemed to be developed without recourse to any data, except that already used in standard QM. What have these alternatives really added?

They don't explain new phenomena, and they give obviously bright people like David Deutsh the chance to come up with some of the silliest arguments physics has ever seen. In his case, I refer particularly to the jive and con of "shadow photons", one of his better nonsensical ideas. (In some sense, we've gone back to pre-Galileo times in which authority was the primary criteria for vetting ideas. Data, while nice, was really not that important.)

A bottom line is: 1, Nature is not always classical.That is, God knows why, Nature is not a 19th century construct; it's far more complex than Newton or Maxwell ever imagined. To suppose that 20th century Nature can and should be explained by 19th century ideas and intellectual structures is, shall we say, pushing research in the wrong direction.

2. Nature is the boss, whether it confoms to our current strictures or not. That QM is, at times, bizarre simply means that to explain the bizarre requires new ways of thinking. To expect that these new ways of thinking should provide a complete, or just extensive world view is, I think, wrong, absurd, and as arrogant as the English physicists at the turn of the century, the TOE folks today, and certainly the weird notions of the anthropic priniciple.(Isn't amazing that these anthropic souls have no more empirical clue than the rest of us about life, and its role and place in the Universe.) As people are won't to say these days, Hello.

Hey, humans are far from the end-all, be-all; we are lucky to be here, and luckier still to have the capabilities to understand Nature. With all due respect, this anthropic stuff, this MWI stuff , belongs in the Monty Python world. These theories have absolutely no empirical foundation, and, in my opinion, are acknowleged only beause a few heavy hitters like John Wheeler like such notions. Back to authority)

3. I believe that when in conflict, human ideas are often trumped by Nature. The best current example is QM. For various understandable reasons, more than a few physicists have problems, some slight, some major, with QM. More often than not, these problems can be associated with 19th century ideas, which are very much at the center of our-day-to-day life. That is, many are unwilling to take the position that it's a new ball game, that many of our old ideas -- causality, notions of the external world, the role of observers, closed theories -- do not necessarily apply to QM as they did to classical 19th century ideas. and, so it seems that many refuse to, or are simply comfortble with the old ideas, and simply can't' accept the sparse quantum world.

The 2-slit experiments drives some to distraction. But, theory and experiment seem to do well together.The strange interference is there, like it or not. What's good about QM in this case is that the basics of 2-slit interference are generalizable, and serve nicely in, for example, scattering experiments. No amount of slick exposition can take the triumph from QM. This means to me, the real issue is to find a framework in which QM is celebrated as an extraordinary human acheivement, and to keep pushing toward a deeper understanding of QM and Nature -- requires experiments and theories that give numbers. Worked before.
Regards
Reilly

 

[vanesch]

Quantum theory, at every level, was born to explain, to provide understanding of very strange, classically impossible phenomena. Now we even have such gems as MWI, and Bohm's gallent efforts to turn back the clock on QM, and who knows what else. The problem with these efforts is that they seemed to be developed without recourse to any data, except that already used in standard QM. What have these alternatives really added?

Well, honestly, it is from this perspective that I see MWI as one of the mental pictures that can make the standard quantum formalism "intuitively understandable". If you have no problems with QM, whatever your view is, then keep it that way! But you often see that one asks for "what is the action at a distance" in EPR situations or "how can this be?" in delayed choice quantum erasers and so on. Personally, I was also bugged by these apparently "nonsensical" (but empirically confirmed) situations, and taking on as a mental picture "MWI" (which is nothing else but telling yourself that the mathematical objects you handle in standard QM are "genuine" in the same way as "position of a particle in space" is genuine in classical mechanics), has helped me to build a "mental picture of what happens" in these EPR experiments and so on (in the same way as - I assume - you have some mental picture of "what happens" when you do Newtonian mechanics).
Now, whether this is "really true" or not doesn't matter for me: I just imagine that what the standard QM formalism tells me, is somehow "what really happens physically" in my mind's eye. As such, I don't have to fiddle with the formalism to get my picture up and running, within that picture, I don't wonder how there is "action at a distance" in EPR, or if there is some backward causal magic in delayed choice quantum erasers.

If this doesn't work for others, then they will have to devise their own way of getting - if they desire so - a different way of understanding quantum theory. I just want to be of some help for those who struggle with things I also struggled with (and many do), and for which I found "ease of mind" with MWI. As I repeated often, to me, MWI is just a way of getting a "feel" for quantum theory as it is now. It is not some credo of some weird religion.

To suppose that 20th century Nature can and should be explained by 19th century ideas and intellectual structures is, shall we say, pushing research in the wrong direction.

I agree with that. That's why I insist on letting the formalism (which has been build upon observation) guide the interpretation, and not vice versa.

 

[vanesch]

Suppose the state of the detectors is set by the even-ness or odd-ness in the millionth digit of the energy of some randomly selected CMBR photon. Of course, this photon was emitted in some specific process 15 billions years ago 15 billion light years away. And the past light cone of that emission event does (in the very remote past) overlap with the past light cone of the event at which the particle pair (to be measured) is emitted by the source. So think about what you are saying here: it's not just that "the state of the dectors can be inferred at the source by means of the known fields", but that some truly incomprehensible set of events 10s of billions of years ago has magically set things up so that the particle-pair-emission event and the CMBR photon emission event (events which happen 15 billion light years apart from each other) are correlated -- and not just correlated in any old way, but correlated so that the millionth decimal place in the energy of the one has some connection with the state of the emitted pair.

I wholeheartedly agree. (nice to agree some times too )

There is a difference between saying: you don't have a completely closed argument to forbid such a theory on one hand, and to propose a reasonable formulation of it which works out in such a spectacular way on the other.

 

[Demystifier]

Now we even have ... Bohm's gallent efforts to turn back the clock on QM ... What have these alternatives really added?

This for example:
http://arxiv.org/abs/quant-ph/0406173
Or this:
http://arxiv.org/abs/hep-th/0407228
http://arxiv.org/abs/hep-th/0601027
Or this:
http://arxiv.org/abs/gr-qc/0611037

 

[ueit]

Suppose the state of the detectors is set by the even-ness or odd-ness in the millionth digit of the energy of some randomly selected CMBR photon. Of course, this photon was emitted in some specific process 15 billions years ago 15 billion light years away. And the past light cone of that emission event does (in the very remote past) overlap with the past light cone of the event at which the particle pair (to be measured) is emitted by the source. So think about what you are saying here: it's not just that "the state of the dectors can be inferred at the source by means of the known fields", but that some truly incomprehensible set of events 10s of billions of years ago has magically set things up so that the particle-pair-emission event and the CMBR photon emission event (events which happen 15 billion light years apart from each other) are correlated -- and not just correlated in any old way, but correlated so that the millionth decimal place in the energy of the one has some connection with the state of the emitted pair.

I wholeheartedly agree. (nice to agree some times too )

The “argument” put forward by ttn is not even an argument but an appeal to emotion (“10s of billions”, “15 billion light years apart”, “millionth decimal place”, “magically”) . I’m sad that you’ve been fooled by it.

Any deterministic theory requires, in order for a good prediction, a good knowledge of the initial parameters. If you choose to introduce as a parameter the properties of a photon generated at the big-bang then you find yourself forced to introduce the big-bang in calculations. The absurdity comes not from the theory but from the physicist who decided to use a practically unknowable parameter in his experiment.
In order to describe Aspect’s experiments I only need information regarding the state of the two detectors, few fractions of a second before detection and nothing else.

My analogy with the “gravitational EPR” gedankenexperiment shows how lame ttn’s “argument” is.

There is a difference between saying: you don't have a completely closed argument to forbid such a theory on one hand, and to propose a reasonable formulation of it which works out in such a spectacular way on the other.

I agree with this but there is no need to misrepresent or exaggerate in order to close that argument.

 

[ttn]

I know I said I wasn't going to comment any more on this thread (god, I think I might have actually said that twice already ) but I can't pass this up because it makes everything so clear:

In order to describe Aspect’s experiments I only need information regarding the state of the two detectors, few fractions of a second before detection and nothing else.

That is simply not true. If you think that, you haven't sufficiently understood Bell's theorem and/or the superdeterminism you are proposing.

If you consider as "given" (relative to ascribing probabilities for the possible outcomes of the nearby measurement) only (a) the state of the particle pair to be measured and (b) information regarding the state of the nearby detector, then you cannot account for Bell-inequality-violating correlations. That's the theorem. On the other hand, if, as I think your statement above is meant to imply, you consider as "given" the above (a) and (b) and in addition "information regarding" the state of the other, distant detector, then your account of the correlations is not local. *Obviously* you can "describe Aspect's experiments (i.e., account for the outcomes) if you allow each outcome to depend on the particle pair state and "information regarding the state of the two detectors, few fractions of a second before detection". But this would not be a *local* explanation of the outcomes, which is supposed to be the whole point, right?

So it is not an appeal to emotion, or some pointless rhetorical distraction, that I bring up all the stuff about billions of years ago and billions of light years away. This is actually what your theory *requires* us to consider if we are going to convert what you say above into an actual *local* explanation of the correlations. It is not good enough to say that the current settings of the apparatus "just happen" to be so as to fool us into thinking we have performed a non-biased measurement of the correlations. You must shoulder the burden of explaining how this (apparent) conspiracy could have come about, and the *only* way to do this *locally* is to search in the distant past for events which have *caused* (*locally*) the two settings and the particle state to get appropriately correlated. So, good luck with that.

My good friend and philosophical partner-in-arms vanesch will have to take up any further discussion of this on my behalf because this time I'm serious when I say I won't comment anymore! (Unless I change my mind...)

 

[vanesch]

Any deterministic theory requires, in order for a good prediction, a good knowledge of the initial parameters. If you choose to introduce as a parameter the properties of a photon generated at the big-bang then you find yourself forced to introduce the big-bang in calculations. The absurdity comes not from the theory but from the physicist who decided to use a practically unknowable parameter in his experiment

The point is that it is not very difficult to set into action an experiment that uses almost ANY kind of measurement to decide upon the settings of the polarizers. This can range from cosmic microwave background noise, to stuff happening in the brain of an experimenter, to sampling a song of the 1930ies... you can pick MIRIADS of ways to select the polariser settings, based upon totally different kinds of physical systems, and ALL of them have to agree upon the RIGHT polarizer settings in order to generate the right EPR correlations. That is, if we use samples of a song of Vera Lynn to decide upon the polarizer settings, then these samples have to be in agreement with the polarisations of the sent pairs of light pulses so as to generate EPR correlations. But we could decide in the middle of the experiment, to switch to CMB radiation noise as a decider for the polarizations, and this should simply continue. Etc...
In other words, all these totally different physical quantities have to be in agreement to generate the correct polarizer settings in agreement with the pairs sent out.

In order to describe Aspect’s experiments I only need information regarding the state of the two detectors, few fractions of a second before detection and nothing else.

The point is that that "information" can be Vera Lynn's song, or the CMB radiation or whatever, and this all has to come out correctly.

My analogy with the “gravitational EPR” gedankenexperiment shows how lame ttn’s “argument” is.

Not really. In the gravitational EPR experiment you propose, everything is a simple gravitational interaction. Your example doesn't work anymore if there is one single electromagnetic phenomenon happening, which "helps align" the stars. It is clear that if a gravitational EPR experimenter had the impression of having some freedom to align or not, the stars in the galaxy, that the argument wouldn't hold anymore - even if this freedom is only apparent. It simply means that the experimenter has some "way of deciding" to his disposal to align, or not, the stars in the galaxy, which means essentially that the experiment can be set up in such a way that alignment or not of the galaxies can be correlated with just any other phenomenon.


I agree with this but there is no need to misrepresent or exaggerate in order to close that argument.[/QUOTE]

 

[ueit]

I know I said I wasn't going to comment any more on this thread (god, I think I might have actually said that twice already ) but I can't pass this up because it makes everything so clear:

In order to describe Aspect’s experiments I only need information regarding the state of the two detectors, few fractions of a second before detection and nothing else.

That is simply not true. If you think that, you haven't sufficiently understood Bell's theorem and/or the superdeterminism you are proposing.

If you consider as "given" (relative to ascribing probabilities for the possible outcomes of the nearby measurement) only (a) the state of the particle pair to be measured and (b) information regarding the state of the nearby detector, then you cannot account for Bell-inequality-violating correlations. That's the theorem. On the other hand, if, as I think your statement above is meant to imply, you consider as "given" the above (a) and (b) and in addition "information regarding" the state of the other, distant detector, then your account of the correlations is not local. *Obviously* you can "describe Aspect's experiments (i.e., account for the outcomes) if you allow each outcome to depend on the particle pair state and "information regarding the state of the two detectors, few fractions of a second before detection". But this would not be a *local* explanation of the outcomes, which is supposed to be the whole point, right?

Bell's theorem proves that the properties of entangled particles and detectors' orientation are not statistically independent parameters. The theorem is silent about the mechanism by which the correlations are realized. It doesn't require it to be non-local.
Aspect's experiment used a fast-switching device to set the detector while the particles were in flight. Does the experimental result rule out a local mechanism behind the correlations? Not at all.

As I said, few fractions of a second before detection (the time it takes the photon to travel from the source to the detectors), just before the entangled photons are released, the information regarding the detector's state arrives at the source. Because I propose a local mechanism, that information is not "up to date" but this is not a problem. We've agreed that the detectors are deterministic systems, therefore knowing their state at a certain time is enough to predict their state in the future. So, when the particles leave the source they "know" how they will be detected even if they only have old information.

To better illustrate my point, let's say some aliens set up an EPR-type experiment. The source is placed on Earth and the detectors about 1 parsec away.
But the humans found out about the experiment and wanted to make fun of the aliens by sending them a message encoded in the experimental data. But, they don't know how the aliens will perform the measurements so what to do? Well someone comes with the idea of building a telescope so powerful that it can see the electrons and quarks the detectors are made of. He then puts the data into a computer and calculates the detectors' state one year into the future, when the measurement will be performed. It doesn't matter how the aliens will do to "chose" the detectors' orientation. A quick "scan" of their brain will inform humans about the so-called choice.

In conclusion, as I said before, there is no need for a non-local mechanism if the detectors are predictable and if their state (even if an old one, it doesn't matter) can reach the source via EM or other signals traveling at or bellow the speed of light.

Of course, finding the exact mechanism could be a difficult task, perhaps more dificult than going from Newtonian gravity to GR, but the fact that such an mechanism is allowed by Bell's theorem and all experiments performed to date is quite important.

 

[ueit]

The point is that it is not very difficult to set into action an experiment that uses almost ANY kind of measurement to decide upon the settings of the polarizers. This can range from cosmic microwave background noise, to stuff happening in the brain of an experimenter, to sampling a song of the 1930ies... you can pick MIRIADS of ways to select the polariser settings, based upon totally different kinds of physical systems, and ALL of them have to agree upon the RIGHT polarizer settings in order to generate the right EPR correlations. That is, if we use samples of a song of Vera Lynn to decide upon the polarizer settings, then these samples have to be in agreement with the polarisations of the sent pairs of light pulses so as to generate EPR correlations. But we could decide in the middle of the experiment, to switch to CMB radiation noise as a decider for the polarizations, and this should simply continue. Etc...
In other words, all these totally different physical quantities have to be in agreement to generate the correct polarizer settings in agreement with the pairs sent out.

The point is that that "information" can be Vera Lynn's song, or the CMB radiation or whatever, and this all has to come out correctly.

The key issue here is that those "totally different physical quantities" are not as different as you claim they are. If, at the bottom, all particles follow deterministic trajectories and if they can "communicate" their state via a local mechanism, similar to gravity in GR, it doesn't matter how complex or big a system is or what internal distribution it has. A button-pressing monkey or a computer analyzing "Vera Lynn's song" are, after all both quark-electron systems and I see no reason to look for different physical laws to describe each of them.

Not really. In the gravitational EPR experiment you propose, everything is a simple gravitational interaction. Your example doesn't work anymore if there is one single electromagnetic phenomenon happening, which "helps align" the stars. It is clear that if a gravitational EPR experimenter had the impression of having some freedom to align or not, the stars in the galaxy, that the argument wouldn't hold anymore - even if this freedom is only apparent. It simply means that the experimenter has some "way of deciding" to his disposal to align, or not, the stars in the galaxy, which means essentially that the experiment can be set up in such a way that alignment or not of the galaxies can be correlated with just any other phenomenon.

Sure, in my example, you can appeal to EM to "fool" gravity. But how can you propose to "fool" an electron or a quark if it follows a deterministic trajectory? You should use something else that is not "covered" by QM, a different kind of force. I don't have any idea of what that may be.

So, if you are limited to what QM (or better QFT) describes, and if the theory is deterministic you are like an astronaut, without any propulsion system, orbiting some planet. He might believe that it goes round and round because of his "free will" but he can do nothing but "choose" to follow that trajectory.

 

[reilly]

This for example:
http://arxiv.org/abs/quant-ph/0406173
Or this:
http://arxiv.org/abs/hep-th/0407228
http://arxiv.org/abs/hep-th/0601027
Or this:
http://arxiv.org/abs/gr-qc/0611037

Interesting work indeed. But where does it go? Theory is nice, particularly when it is close to experiment. I first enountered Bohm's work some 50 years ago. It's still outside the mainstream, beause it has contributed little or nothing to further any branch of physics that's connected to experiments. My sense is that the arguments about Bohm have not changed much over the last 50 years.

Regards,
Reilly Atkinson

 

[reilly]

Now, whether this is "really true" or not doesn't matter for me: I just imagine that what the standard QM formalism tells me, is somehow "what really happens physically" in my mind's eye. As such, I don't have to fiddle with the formalism to get my picture up and running, within that picture, I don't wonder how there is "action at a distance" in EPR, or if there is some backward causal magic in delayed choice quantum erasers.

If this doesn't work for others, then they will have to devise their own way of getting - if they desire so - a different way of understanding quantum theory. I just want to be of some help for those who struggle with things I also struggled with (and many do), and for which I found "ease of mind" with MWI. As I repeated often, to me, MWI is just a way of getting a "feel" for quantum theory as it is now. It is not some credo of some weird religion.



I agree with that. That's why I insist on letting the formalism (which has been build upon observation) guide the interpretation, and not vice versa.

Sounds good to me. I find MWI confusing, and take my Born interpretation with a grain of salt.

I think about an imaginary QM world based largely on a three-point interactions, transitions if you will. I think sometimes pictures of such are called Feynman Diagrams. Like many,I think the standard diagrams are a God send. But, it would be a great stretch to say they represent real processes -- but then many don't

Regards,
reilly

 

[vanesch]

The key issue here is that those "totally different physical quantities" are not as different as you claim they are. If, at the bottom, all particles follow deterministic trajectories and if they can "communicate" their state via a local mechanism, similar to gravity in GR, it doesn't matter how complex or big a system is or what internal distribution it has. A button-pressing monkey or a computer analyzing "Vera Lynn's song" are, after all both quark-electron systems and I see no reason to look for different physical laws to describe each of them.

Yes, but look at the following. We have the impression that we can "decide" about the settings of the polarizers. This means that we can essentially correlate this with almost any other phenomenon. Now, I don't want to drift in a discussion here about "free will" - I can accept that free will is an illusion in a deterministic universe, but nevertheless, it has a meaning. The meaning is that the choices can be based upon "arbitrary" correlations (human brain states, photons coming from the back end of the universe, samples of songs sung long ago...). We have learned somehow, throughout the entire evolution of science (and even before that), that when things seem to depend upon "free will" that they are statistically independent. In fact, the whole endeveour of science is based upon that idea! "Controlled experiments" are nothing else but exactly that: we change "arbitrarily" some parameters while keeping others constant, and we deduce "causal relations" from that. You push arbitrarily the button, and you see the light go on. You do that 50 times, and you conclude that there is some causal relationship between you pushing the button as cause, and the light going on as consequence... maybe due to the current that will flow in the wire, or maybe for another reason. In fact, THE WHOLE OF SCIENCE (and all of our common sense knowledge) has been deduced directly or indirectly that way: what we can change "arbitrarily" must be the "cause" and what is "observed" is the consequence. Even the whole idea of a deterministic time evolution comes from those observations (and their theoretical extrapolations) in the first place.
Now, whether we "really" had some choice, or whether we were just passive observers of spurious correlations between disparate events (such as me suddenly having a desire to push the button which is the result of some brain activity) doesn't matter. What matters is that we know when things are "arbitrary choices" we (think we can) set, and which find their origin if not in free will, then in some processes that have "nothing to do" with the phenomenon that is to be observed.

Now, if we are going to claim, that the light went on just by some thermodynamical coincidence (suddenly, the random motion of the atoms in the wire increased a lot as a statistical fluctuation), and that, exactly at that time, in my brain, there was a process that gave me some desire to push the button, and that this coincidence repeats itself several times, then indeed, I will be fooled into thinking that there is a causal relation between me pushing the button, and the light going on, but in fact there is none. But then, ALL WE KNOW is based upon erroneous deductions of causal relationships which were in fact nothing else but funny coincidences.

This is different with your GR "experiment". In GR, if we don't use electromagnetism, we wouldn't "have the impression that we had the freedom to choose when the galaxies aligned". We would just be passively observe the galaxies evolve, see them align, and then see that our asteroids got pulled apart. We wouldn't have that same impression of 'being able to decide when we push the switch". Indeed, in a passively evolving system, where we cannot "arbitrarily decide", we don't know whether correlations represent cause-effect relationships. At no point, we would be fooled into thinking that we had a choice.

And finally, my argument against "unknown physics/conspiracies/..." to explain EPR correlations is this: quantum mechanics predicts them correctly. That means that all the physical knowledge of the mechanism is already included in one way or another in quantum theory. Now, we might not understand this totally, or quantum theory might be an "effective formalism" of a deeper theory of course. But it would be very strange that a superdeterministic theory of which we don't even have a clue how it might be put together (in such a way that samples of a song of Vera Lynn are correlated with the photon pairs emitted in a lab 60 years later) produces as only effect, exactly those effects that are nicely described by the current quantum formalism. A quantum formalism that was deduced by looking at observations that were often made by using "free choices" of settings to derive "causal relationships".

Again, I don't say that superdeterminism is impossible. But it stretches imagination (much more so, imo, than the extravagance of MWI!).

I have outlined several arguments:

1) The argument that was used against MWI in the beginning of this thread (namely, that MWI supposes a difference between observation and "reality", while that MWI was derived by looking at QM, which was a formalism that was derived by looking at observations, probably by people who thought that observations corresponded to reality), can be, in a much stronger form, used against superdeterminism:
If superdeterminism is true, then all "causal relationships" we've ever derived were the result of funny correlations without the slightest bit of causality. This includes all we think we know, because all our knowledge is based upon the assumption that free choices are uncorrelated with what is going to be observed.

2) There is not the slightest hint of an existing theory that does this, even though it is not impossible.

3) All that trouble for finding, finally, something that we know already: the EPR correlations are correctly predicted by quantum mechanics as we know it today.

He might believe that it goes round and round because of his "free will" but he can do nothing but "choose" to follow that trajectory.

He wouldn't. If he had the impression of free will, he would find correlations with several distinct phenomena. He could say: now, the planet will have the position given by a 'random number generator'. Next, he could say: now the planet will have the position given by samples of my favorite song. Next, he could say...
Of course, this is maybe not truly free will, but the point is that the correlations could be with just anything. If this happens, THEN he will have the impression of "being able to decide where the planet is". And if, as a function of that position of the planet, he observes certain phenomena (like tides on another planet or something), he might start to think that there is a causal relationship. But he wouldn't have that impression from just the planet following passively an orbit on which he "cannot decide" how to "change" it.

I'm not fooled into thinking that the sun's position is causally determined by the hands on my watch. If however, I can "change" the hands of my watch "arbitrarily" and the sun would "follow" instantaneously, then I would be quite puzzled. But for that, I have to be able to get the impression that I can freely change the position of the hands of my watch.

 

[tehno]

I first enountered Bohm's work some 50 years ago. It's still outside the mainstream, beause it has contributed little or nothing to further any branch of physics that's connected to experiments. My sense is that the arguments about Bohm have not changed much over the last 50 years.

To me,Bohm's work is an interesting approach how to interpret some aspects of QM.I don't see how it can contribute to any branch of experimental physics or predict something new what can't be predicted by an ortodox school of QM.Therefore ,as such,it's just a try to "see" what is in background of QM and its' equations. What would Einstein say about Bohm's interpretations?

 

[vanesch]

To me,Bohm's work is an interesting approach how to interpret some aspects of QM.I don't see how it can contribute to any branch of experimental physics or predict something new what can't be predicted by an ortodox school of QM.Therefore ,as such,it's just a try to "see" what is in background of QM and its' equations.

Right. That's also how I look upon Bohm (and MWI, btw).

What would Einstein say about Bohm's interpretations?

Now, that's an interesting question

He would have liked the "realist" aspect, and disliked the fact that relativity goes out of the window, I guess (but then, who am I to say what Einstein would have thought :shy: ...)

 

[Anonym]

Quote:

What would Einstein say about Bohm's interpretations?

Now, that's an interesting question.

He would have liked the "realist" aspect, and disliked the fact that relativity goes out of the window, I guess (but then, who am I to say what Einstein would have thought)

For your pleasure

A. Einstein to M.Born (12.5.1952):

”Did you see as Bohm (as by the way de Broglie 25 years ago) believes that the quantum theory may be interpreted deterministically otherwise? It, in my view, cheap consideration, however, your judgment is better indeed.”

Regards, Dany.