Which is fine. The point is only that QM is an abstract theory about the mechanics of physical systems generally, regardless of the specific systems one is interested in modelling (which will include context-specific information). — Andrew M

Right, but we support abstract theories with empirical evidence gathered from observations. If, what is called an "observer" is not really an observer by rigorous standards, then the biases inherent within that definition of "observer" must be accounted for or else "empirical evidence" will not really be empirical evidence.

I really believe that you don't see the problem. — Wayfarer

"You say that to all the boys" who disagree with you. the "problem" as you see it exists only on your particular set of presuppositions, which apparently you cannot see that others don't share.

And what they DON'T share is 'the ability to form a perspective'. — Wayfarer

You didn't attempt to address my solution to the problem, which is along the lines of:

"

'the universe seems more a great mind than a great machine') — Wayfarer

that is, the implication here is panpsychism or pan-experientialism; nature itself is both mental and physical "all the way down". The irony is that your thinking consists in reacting to an outmoded paradigm; the idea that the universe is a dead mechanism. You accept this no longer apt idea in order to assert that human subjects are special, and you reject any idea that nature itself has an ineliminable subjective part to it.

So you keep mechanical nature and then project the subjective part into the "beyond" somewhere. But QM has no truck with any beyond, and thus your thinking on this, which is firmly founded on the empirical observations of physicists, and yet which nonetheless rejects any empirical explanations, seems inapt. Your position seems quite inconsistent and confused, in other words.

I really believe that you don't see the problem. One of the things Bohr said, and it's a bona fide quotation, is that 'Anyone who is not shocked by quantum theory has not understood it.' And I don't think you see anything shocking about it - ergo ... — Wayfarer

I'm not the one advancing an incredibly contentious idea about quantum mechanics requiring human minds to work. Note, this is not just the claim that humans can act as observers; but that only humans can act as observers. I'm indifferent to the matter of whether we can, but strongly convinced that other things can observe too; as is consistent with everything we've read in the thread and referenced. Moreover, I believe that if human consciousness can act as an observer, our sentience will have much less to do with that than the fact that our consciousness comes equipped with systems of macroscopic objects in our bodies.

The claim that only humans can act as observers, conversely, is inconsistent with everything we've read. Perhaps you should be more surprised; your view is inconsistent with the sources you used to form it.

Another Bohr quote is that 'a thing does not exist until it's measured'. The Wheeler 'Law without Law' article draws on the same point, where it says 'a phenomenon is not a phenomenon until it has been brought to a close by an irreversible act of amplification'. OK, this might be a photographic plate or some other device, but in all cases, the act of measurement or observation is intrinsic to it. — Wayfarer

This is extremely inconsistent with the claim that only humans can act as observers. Lab equipment also, trivially, works. And I do not believe you think lab equipment is sentient. The only way I can make sense of your claim now is that you believe that something being a derivative of human action imparts it observer status; but this thereby means non-human things can be observers.

Is your claim that observing objects must be derived from humans or be humans, or is your claim that only human consciousness can be an observer?

But look at the definition of 'device': "a thing made or adapted for a particular purpose, especially a piece of mechanical or electronic equipment". Devices are made by an observer, to complement or supplement the natural senses, and their operation and raison d'être are entirely dependent on the observer. And, as I noted already, 'data' does not become 'information' until it is interpreted in a context - until someone is informed by it. An automatic weather station contains only data, which do not become information until they're observed. — Wayfarer

This is irrelevant to whether lab equipment, or other physical processes, can act as observers. It's also inconsistent with the notion that probability distributions have entropy notions derivable from them. If anything, the 'data' comes after an 'informational' relation obtains between a system and an observer. A pair of electrons can be entangled with each other, thus giving information about the other's state, but they could also be in superposition prior to measurement; data derives from observing the state (or superposition) of something, not just having information about it. You'v got things the wrong way round here; information is much weaker than data.

Yes, quantum physics does suggest 'subjective idealism'. Hence the controversy! But that is not exactly news - Sir James Jeans and Arthur Eddington both wrote books on it between the wars ('the universe seems more a great mind than a great machine'). Paul Davies and other science writers have been commenting on it for decades - I read 'The Matter Myth' in, oh, about 1989. — Wayfarer

Except no, it doesn't, and the role consciousness and ideas play in quantum processes has been declared either irrelevant or non-central in every single source we've read in the thread. Also note 'seems like' in the quote, it would not surprise me if this was another analogy you have misinterpreted.

All of the arguments that are being deployed here are specifically to avoid the implication of the role of the observer which seems the unavoidable inference. But many think it's solved, or that it's a non-problem, because of 'presumptive realism', which is that 'common sense simply insists that the Universe exists when we're not observing it. Everyone know this is true.' But this is precisely why Bohr said that 'quantum mechanics is shocking'. This is why Einstein felt compelled to ask the question about 'does the moon continue to exist when we're not looking at it?', and why Einstein and Bohr went on to debate the point for 30 years. — Wayfarer

You continue to display a deaf ear for metaphor, and we've covered this. That quote is intended to be a reductio on the claim that observers constrain or realise quantum system dynamics; Bohr did not think that only human consciousness could be an observer, and he disagreed with Einstein in that debate not because Bohr thought only humans could be observers, but because he thought (rightly) a proper account of quantum phenomena requires one to tackle observer dependence. You have mistaken Einsten's exaggerated caricature of Bohr's position for Bohr's position (which has been revealed previously by looking at quotes from Bohr, he took something close to a relational view around the time).

The initial philosophical problem has never been solved, it's simply been continually obfuscated. What I'm arguing is that there is an irreducible subjective element to all science and all observation, which is the constructive (in the Kantian sense) activities of the mind. 'Modern thought' believes that it has bracketed this out by arriving at a purely quantitative and completely impersonal description of the Universe - the so-called 'view from nowhere'. However physics shows us that even the view from nowhere is still a view, and that a view requires a viewer. But people would rather believe in an infinite number of parallel universes than face up to it. — Wayfarer

Ah yes, that unforgettable Kantian thesis, subjective idealism. It is almost as if he never argued against subjective idealism in the Critique of Pure reason.

Information = data, measurement = conception = observation, empirically real = subjectively ideal, misrepresenting all the sources we've analysed together in the thread, presuming that I'm some ancient Cartesian and responding as such. grumble grumble

If you read me with more care you'd see that while yes, I'm a materialist of some sort, but I have strong sympathies for the relational interpretation of QM. IE; I fully agree with you that observers and systems need to be considered together. This is the grand charge you're saying I don't understand, but the relational character of nature is something I think is very important to see. You just think that I don't understand the issues here because I'm not using the above series of equivocations.

Though, I don't claim to be an expert on quantum mechanics.

The article says that an external system can take this more 'full measurement' of some system, but not any system containing the system being measured. I don't understand this since Heisenberg's uncertainty says that even an external system can't do that. So they must mean something else when discussing the sort of information they expect from this 'self measurement'. — noAxioms

After some reflection, I am not convinced by this explanation.

The first section says:

Dalla Chiara shows that the duality in the description of state evolution, encoded in the ordinary (i.e. von Neumann's) approach to the measurement problem, can be given a purely logical interpretation: “If the apparatus observer O is an object of the theory, then O cannot realize the reduction of the wave function. This is possible only to another O′, which is ‘external’ with respect to the universe of the theory. In other words, any apparatus, as a particular physical system, can be an object of the theory. Nevertheless, any apparatus which realizes the reduction of the wave function is necessarily only a metatheoretical object ” (Dalla Chiara 1977, p. 340).
...
O cannot have a full description of the interaction of S with himself (O), because his information is correlation information and there is no meaning in being correlated with oneself. If we include the observer into the system, then the evolution is still unitary, but we are now dealing with the description of a different observer.

In other words, from its own perspective, O is 'meta-theoretical', i.e. QM can describe anything but not everything. It must be applied in a particular context or 'perspective'. The only way for observers to know about themselves is to consider themselves in relation to others. This makes somewhat sense to me, actually.

Under any 'consciousness causes collapse' or other anthropocentric take, the friend, being conscious, cannot be in superposition. In any other interpretation, the friend very much can be. — noAxioms

I agree that this is the usual understanding. But in Bitbol's case, it seems that he faithfully follows the remark: "QM can describe anything but not everything". In other words, Wigner can apply QM even to his friend. The 'measurement' for Wigner takes place when he actually enters in the lab.

There is, however a problem here. If Wigner asks his friend before entering in the lab if he sees a definite result, it appears that at this point Wigner already knows that everything in the lab is in a definite state. So, superposition is now destroyed. At this point, it seems it is not very different from the classical case of an unseen coin. The problem is that Wigner still does not know in which state the lab is (including is friend). But it seems that when he enters Wigner and his friend must be in agreement! So for them, S is in the 'up' state.

Let's consider the RQM explanation. O = 'Wigner's friend'. O'= 'Wigner'. If O' 'asks' O if the state of S is definite (let's say spin 'up' or spin 'down'), and O answers 'yes', it seems that now according to O, S is in a definite state, let's say 'up', but at the same time for O' the state is definite but it is either 'up' or 'down'. In MWI terms, for O' there are still two non-interfering branches. Yet, when O' enters, there must be an agreement between them.

But what happened to the 'other branch' in O' (or Wigner's in Bitbol's interpretation)?


(edit: I am not sure that there is no more interference for O' (or 'Wigner) when O (or Wigner's friend) says that he sees a definite state to O')

Just thought of this: Per time symmetry, is there such a thing as radioactive un-decay, and would such an event constitute an end to a causal chain? If not, I don't think the decay can constitute an uncaused event. — noAxioms

I do not think that it is reversible, hence I'd say that time symmetry is broken!

Bob's knowledge of the paper means nothing: The device may have randomly declined to take a measurement and emit a blank paper. Bob can tell if it happened by measuring superposition or not. So the device taking the measurement, and not Bob's knowledge of that action is what collapses the wave function. — noAxioms

But in that case this is not a relevant information for Bob. So, to him the state is still undefined (even if he does not believe that...knowledge is not belief). If, instead, the measurement apparatus works perfectly, he really knows that the state is definite (but we fall in the aforementioned problem, where according to Bob, there are two possible states of 'Alice').

For the alien not to measure the moon, he'd have to put the moon (and everything else) in Schrodinger's box, which is best achieved by making a ship that is one, inside out. Zero information can penetrate from outside to inside the box. He opens the box randomly at some location which happens to be here, and there is some vast wave function of what he might find here that collapses quite improbably to us and our moon. Far more likely it collapses to empty space. Depend on from what distance he came, but it would have to be from over 5 billion light years away because the moon (or the whole solar system) needs to be unmeasured from the start. He'd have to come from a helluva longer distance to find no galaxy here. How far must I travel now to find a place where I have zero information about what is there? A lot further than the event horizon. It cannot be done. We see stuff that is 22 BLY away, which is not possible to reach ever. But the moon is young enough that it can be done. — noAxioms

I agree that the Moon and everything else are in the Schrodinger's box. But this means that in some sense there is 'something' that corresponds to the Moon in the perspective of the alien. When the alien 'opens the box', the Moon 'collapses' in a definite state according to him. But this seems to imply that the Moon in some sense 'exists' before the measurement.

Before that there is no moon to be nonexistent. He can equally declare torrid-planet Vulcan to not exist. In both cases, he's just making stuff up. — noAxioms

I see. But I would say that the comparison is apt for Vulcan and the definite state of the Moon, not the Moon.

I have a hard time figuring out what Bitbol finds special about us. I am special to me, but everything has a relationship like that with itself. Another human ('us' but not 'me') measuring something gives me no more or less knowledge of that measurement than a dot on an unseen paper, and the wave function collapses either way. Wigner's friend just doesn't change that, so there is no 'us', just 'me', which is solipsism if you posit any QM significance to that.
Sorry. You can see I have little patience for anthropocentrism. I'm biased all to hell. — noAxioms

I was going to make Rovelli's point. If something changes state at all, it stores that information in its changed state. A prism is an example of something that sort of interacts with a photon without a state change (storage of the information). The photon is absorbed and immediately a new one is emitted in the same direction, leaving no state change to the prism and a change to the photon for the tiny delay in its journey. The prism does not store the information, and thus does not collapse the wave function of the photon. Objects that do change state don't seem to need to perform an act of registration to be affected like that, so that wording is still a bit unclear to me. — noAxioms

I don't follow. The perspective of the pen seems the same as that of a human being there. The pen just pays a lot less attention. I honestly give humans or any living thing no special regard in this topic. — noAxioms

Ok. So, you endorse some kind of 'panpsychism' or 'panexperientalism'? (see: https://en.wikipedia.org/wiki/Panpsychism#Panexperientialism)
Actually, I agree with you that it seems that Wheeler's take is somewhat ambiguous. More precisely, it seems somewhat arbitrary to think that registering devices are 'special'. I can understand taking sentient beings (including non-humans ones if any) as special. But honestly, it seems that Wheeler's model is somewhat an artificial way to avoid either some form of RQM and giving a special status to conscious observers.

I believe that what Bitbol's find fascinating is that QM seems to force the idea that knowledge is perspectival. This is also what Rovelli finds fascinating of QM. The difference is that according to Rovelli, you can define a perspective for everything, whereas for Bitbol this is not true.

Note, however, that Bitbol's take seems in some sense 'skeptical'. Since we 'directly' know only how the world appears to us, we cannot really 'know' how the world appears to a non-sentient object (if such a thing is meaningful). So, if Bitbol can be charged with some form of anthropocentrism, I believe that his kind of anthropocentrism is not the usually criticized one: it is not due to some wishful thinking that we are 'special' but, rather, it is due to an epistemic reason, namely that we 'directly' know the world as it appears to us. In other words, Bitbol (and in a similar way d'Espagnat) does not deny a mind-independent reality (whether independent of 'my' mind or 'our' minds), but he says that it is inaccessible.

Cool. Few agree with that. It is controversial. — noAxioms

Well, first electrons are identical particles according to QM (if we do not accept hidden variables). Furthermore, QFT seems to give some support to this kind of view: electrons are just excitations of a field. So, it seems justifiable to think that an electron does really have an identity.

Kind of hard not to observe an electron. Its state might be hidden if put in a box, but we put it there so we know its there. If not in the box, it interacts with other things and that makes it exist. I cannot escape that interaction. — noAxioms

Well, yes. So, it must 'exist' even if unobserved!

An unobserved system is in superposition of possible states that follow from the last observed state of the system. The real trick is how to go about not observing it for any length of time. Hence our alien showing up in an inside-out Schrodinger's space ship. — noAxioms

Suppose you wanted to measure the diameter of a pizza. The way to do that is to put the pizza in front of you and hold a tape measure up to it, but the act of putting the pizza in front of you already performed the pizza/not-pizza measurement. I could in theory walk into a dark room, hold out the tape, have the lights turned on and hope by improbable chance that a pizza appears directly under that tape, but that is not likely to happen if I had zero knowledge of the presence of a pizza in that dark room.

So the electron is like that. Maybe I shot it and want to measure where it goes, or any other property of it, but to do that, I'm not taking a measurement of a random volume of space and hoping an electron appears in it. I probably already have a specific one in mind, meaning the measurement of its mere existence has already been done. — noAxioms

I see. Then maybe we are in agreement! The unobserved electron is not really non-existent. More precisely, it does not exist in a definite state. So, before measurement it simply does not make sense to talk about electrons in definite states.

I have more of a problem with MWI having a real wave function because it makes for a weighted reality of each of the worlds. One world seems to exist more than the other, but existence seems not to be anything but a True/False state. How cat X exist twice as hard as Y? So maybe CH resolves that problem for me. — noAxioms

Ok, I see. This for me shows that it is paradoxical to talk about an universal wave-function (whether an epistemic tool or a real entity).

I don't see why it needs to posit indeterminism or not. — noAxioms

IMO, because results of observations are random.

Equally weighted then, but why do we find ourselves in a world where far more 'likely' collapses occur than the 'unlikely' ones? If all results are equally real, why are the probabilities of measuring those results unequal? — noAxioms

Agreed! That's definitely a problem for MWI.

Sounds like RQM. My history is real to me. My future is not, thus 'I' am defined as this endpoint event along with its history, plus an arbitrary designation of which events are 'me' and which ones are 'other stuff'. There's nothing in physics to make that designation.

Information preservation seems to prevent multiple histories from culminating in the same state — noAxioms

Yes, I agree. It does not seems very different from RQM.

Yes, it alludes to the self-referential problems associated with predicting what oneself is going to do in the future. Fortunately, you can usually just choose! — Andrew M

Well, I am not persuaded that it says just that. As I said to noAxioms in my previous post, it seems that the only way for O to have 'information' about 'himself' (or better 'itself', to avoid anthropomorphic language as RQM does) it must consider 'himself'/'itself' as an object to another system. To me this somewhat makes sense.

Yes. Whereas, in my view, potential just means that the value has not been actualized yet for the observer (which would require a local interaction).

It's like the problem of non-referring sentences. The sentence "The King of France is wise" has a potential use but not an actual use until the appropriate physical conditions occur (i.e., a King of France is installed). As a consequence, you have to be careful about the logic applied to such statements. — Andrew M

Ok.

Let me ask a question that I posed to noAxioms. According to RQM, the state of S (let's say that S is an electron) is observed dependent. To be more precise, S can have a definite state, e.g. spin 'up', for O but not for O'. For O' it is still in a superposition. Now O' can ask O if 'it' 'sees' S in a definite state. O answers 'yes'. So, now it seems that according to O' the state of S 'collapsed' to a definite result. O' does not know which one, however. It seems that, at this point, for O, S has spin 'up' but for O', the spin can be either 'up' or 'down'. So, it seems that there are two 'branches' (using MWI language). But when O' 'opens the box' (or 'enters the room', as Wigner does in the Wigner's friend scenario), O' must agree with O according to RQM. But why? How is this justified in RQM? I mean: how the 'disappearance' of the 'other branch' is justified under RQM?

(edit: I am not sure that there is no more interference for O' when O says that he sees a definite state to O')

My own view is that there is a universal quantum state that is invariant, but RQM seems to reject that. Though perhaps another invariant is that we are all human beings with similar physical structures so we should always be able to agree that there are electrons and on the form of an electron. — Andrew M

That's my problem exactly. It seems that there is an ambiguity about the 'unobserved' objects in RQM.
Considering that the electron 'exists' but not in an undefined state IMO solves at least part of this issue.

Basically the same as you. I think almost all of these views can end up looking like Many Worlds when you dig into them. It makes sense in a way since they all depend on unitary QM. Though I think RQM would say that a history can be indefinite rather than there being multiple histories. — Andrew M

Ok, I agree!

In my opinion Wheeler's view is a bit ambiguous. At times he suggests some form of 'panpsychism'. In other places, he seems to suggest that an 'observer' can be a sufficiently complex physical object. By 'sufficient complex physical object', I mean that such an object must be able to store and process information. And maybe, he considers that these objects are somehow sentient.
But IMO, he does not give a 'special role' to human consciousness (or animal consciousness...).

Personally, I prefer either Bitbol's approach, where you can define perspectives to sentient beings, or Rovelli's approach where you can define a perspective to everything (and might relate Rovelli's view to a form of panpsychism).

I have somewhat of a taste for Whitehead's notion of pan-experientialism; the idea that experience or relation appertains to all entities and is thus the 'substance' of reality. Another way Whitehead expresses this is with his notion of concrescence. So, it might be better to say that experience rather than observation collapses the wave function. Experience can be a very broad term even in ordinary usage: as when we say things like "The cliff face experienced the erosive effects of the wind and rain". — Janus

I am too fascinated by panpsychism, pan-experientialism etc. But it too does have problems IMO.

In case you are interested, for a criticism of panpsychism, I suggest this article by Bitbol: https://www.academia.edu/36160525/BEYOND_PANPSYCHISM_THE_RADICALITY_OF_PHENOMENOLOGY. It is a bit long but very interesting IMO. Anyway, criticism to panpsychism can be found at pages 7-13.

(He also criticizes emergentism, at pages 6-7)

But a discussion on consciousness maybe is off-topic...

Thanks boundless, I'll have a read of it.

Note, this is not just the claim that humans can act as observers; but that only humans can act as observers. — fdrake

Do you think any other kinds of beings that we know of can actually do physics? It seems obvious that animals must be excluded. Computers can perform calculations, but again they're human artifacts. So do you have an alternative?

Acknowledging the centrality of the human is actually a gesture of humility. It's the idea that we can attain complete knowledge that his hubristic. That's why I say the Copenhagen approach is a modest attitude.

Is your claim that observing objects must be derived from humans or be humans, or is your claim that only human consciousness can be an observer? — fdrake

Human beings - not specifically 'human consciousness' - are observers, and they create devices to amplify their natural abilities. There are no 'observing objects' - there are measuring and recording devices but as I've said I don't think recording data amounts to 'an observation' until its interpreted.

You know yourself that there are no 'atomic facts' - that facts are only meaningful in an interpretive framework. I mean, physics comprises facts about the universe, but those facts are always embedded in theory.

that unforgettable Kantian thesis, subjective idealism. It is almost as if he never argued against subjective idealism in the Critique of Pure reason. — fdrake

I'm quite familiar with Kant's critique of subjective idealism. As I said before, my inclination is to objective idealism.

Regarding idealism in mid-war physics, see Eddington, James Jeans, and for contemporary examples Richard Conn Henry and Bernard D'Espagnat.

In my opinion Wheeler's view is a bit ambiguous — boundless

I think because it's controversial and counter-intuitive - like there's a conclusion he wishes to avoid.

Do you think any other kinds of beings that we know of can actually do physics? — Wayfarer

The issue is not about who ("who" here to be taken in the broadest possible sense) is capable of "doing physics" but about who can act as an "observer" to collapse the wave function. Not many people can "do physics"; do you think those people are the only ones capable of collapsing the wave function (in general, not merely in the laboratory, of course)?

"Observer" is this context must be being used in a specialized sense. You haven't responded to my suggestion that 'experience' might be used less ambiguously.

"Observer" is this context must be being used in a specialized sense. You haven't responded to my suggestion that 'experience' might be used less ambiguously. — Janus

It is true that my tendency to 'include the subject' is rejected by mainstream science. The wiki entry on the subject says the same, with these footnotes:

Of course the introduction of the observer must not be misunderstood to imply that some kind of subjective features are to be brought into the description of nature. The observer has, rather, only the function of registering decisions, i.e., processes in space and time, and it does not matter whether the observer is an apparatus or a human being; but the registration, i.e., the transition from the "possible" to the "actual," is absolutely necessary here and cannot be omitted from the interpretation of quantum theory. — Heisenberg

"Was the wave function waiting to jump for thousands of millions of years until a single-celled living creature appeared? Or did it have to wait a little longer for some highly qualified measurer - with a PhD?"

-John Stewart Bell, 1981, Quantum Mechanics for Cosmologists.

According to standard quantum mechanics, it is a matter of complete indifference whether the experimenters stay around to watch their experiment, or leave the room and delegate observing to an inanimate apparatus, instead, which amplifies the microscopic events to macroscopic measurements and records them by a time-irreversible process (Bell, John (2004).

My issue with these statements is that it takes too restrictive a view of what 'observation' entails. Because it seems to me that the very experiment that is the subject of this thread calls into question the whole notion that nature exists in a given state, whether or not observed. The whole point is that there is not a single, objective 'state of affairs' that is apprehended differently by different observers. Again, if that were the case, there would be nothing to discuss. Whereas, 'The experiment produces an unambiguous result. It turns out that both realities can coexist even though they produce irreconcilable outcomes.' In other words, two observers report different outcomes which are irreconcilable but correct.

So there's not a particular, observer-independent state which is, or is not, apprehended by the observer. Again the act of observation is implicated in determining the outcome, which is the point at issue. So I'm wondering if the problem with the quotes above is this: that they embody the (natural) viewpoint, that the outcome or object and the observer are two different things. So how could what happens in the mind of the observer effect what happens? It seems a ridiculous proposition when viewed that way. But I think perhaps it's because there is in reality, one situation which includes the observation and the result. Let's consider that.

It makes perfect sense. The photon cannot take one path, unmeasured. That would be the counterfactual definiteness that any local interpretation denies. — noAxioms

For RQM, the path travelled is only counterfactually indefinite for the observer outside the interferometer. It says nothing about what the full-silvered mirrors within the interferometer might measure (the result of which gets subsequently erased by the final beam splitter). Bell's Theorem is inapplicable for RQM because there are no hidden variables in the observer's reference frame.

Of course, if the photon did travel only one path for the full-silvered mirrors, that still leaves open the question of what produces interference for the observer. But, logically, a one path explanation has not been closed off.

That's your brain interpreting it that way. The reflection very much still appears to raise the arm on the same side, but appears to have switched front to back. — noAxioms

Yes. Physically it's a front/back reflection. And it can also potentially be perceived as a 3D object that is half rotated around the up/down axis and reflected left/right. Perhaps a 2D/3D gestalt effect.

I don't see that as superimposing or interference. — noAxioms

Thanks, problems noted!

My issue with these statements is that it takes too restrictive a view of what 'observation' entails. — Wayfarer

...yet another exhibition of Wayfarer's attempt to assasinate language for his equivocal woo: as if the attempt to unduly restrict 'observation' to nothing but humans is not among the most severve 'restrictions' one could arbitrarily place on interpretations on QM. Newspeak for the pseudoscientific cause: war is peace, inclusivity is 'too restrictive'. And that's to say nothing of this arrogrant reverse-speak where the height of hubris is passed off, bewilderingly, as 'humility':

Acknowledging the centrality of the human is actually a gesture of humility. — Wayfarer

Hot garbage.

What human beings and table lamps have in common is that they are substantial and have form.
— Andrew M

And what they DON'T share is 'the ability to form a perspective'. — Wayfarer

Right! I think we're in agreement.

Right, but we support abstract theories with empirical evidence gathered from observations. If, what is called an "observer" is not really an observer by rigorous standards, then the biases inherent within that definition of "observer" must be accounted for or else "empirical evidence" will not really be empirical evidence. — Metaphysician Undercover

Yes, the term observer has two uses, so we should always pay attention to the context to avoid equivocation. If an inanimate object is called an observer, then no intentionality is implied, it's just a reference frame. Whereas human observers have an intentional view (and can additionally serve as a reference frame).

Well, I am not persuaded that it says just that. As I said to noAxioms in my previous post, it seems that the only way for O to have 'information' about 'himself' (or better 'itself', to avoid anthropomorphic language as RQM does) it must consider 'himself'/'itself' as an object to another system. To me this somewhat makes sense. — boundless

Yes. This seems to align with Wittgenstein's private language argument. Our language develops via interactions with other people and things in the world. By which we come to learn things about ourselves as well.

Let me ask a question that I posed to noAxioms. According to RQM, the state of S (let's say that S is an electron) is observed dependent. To be more precise, S can have a definite state, e.g. spin 'up', for O but not for O'. For O' it is still in a superposition. Now O' can ask O if 'it' 'sees' S in a definite state. O answers 'yes'. So, now it seems that according to O' the state of S 'collapsed' to a definite result. O' does not know which one, however. It seems that, at this point, for O, S has spin 'up' but for O', the spin can be either 'up' or 'down'. So, it seems that there are two 'branches' (using MWI language). But when O' 'opens the box' (or 'enters the room', as Wigner does in the Wigner's friend scenario), O' must agree with O according to RQM. But why? How is this justified in RQM? I mean: how the 'disappearance' of the 'other branch' is justified under RQM? — boundless

I don't think there is another branch for RQM. A superposition merely indicates that there is no actual value for O' prior to an interaction. The reason that O' will agree with O is simply that an interaction allows the value that O has obtained to also become actual for O'. This does not constitute a hidden variable because the rule is that the value only exists as the result of a local interaction between the two systems.

As for why that should make a difference, my thought is that there are many possible spacetime paths between the present moment for O' and the measurement event for O. Similar to the Andromeda paradox, perhaps the time of the event for O can potentially be in the future of O' (until fixed in the past of O' by an interaction).

(edit: I am not sure that there is no more interference for O' when O says that he sees a definite state to O') — boundless

There is still interference. See Brukner's discussion on this below:

The key element of the experiment is that the message contains no information about which outcome has occurred and thus should not lead to a collapse of the quantum state assigned by the superobserver. Imagine that the observer encodes her message in state |message>₅ of system 5. This state is factorized out from the total state, |psi(t')> = 1/sqrt(2)(|z+>₁|z+>₂|z->₃|knows "up">₄ + |z->₁|z->₂|z+>₃|knows "down">₄) |message>₅, and thus the communication of the message does not destroy the superposition. — On the quantum measurement problem, p18 - Caslav Brukner

The first section says:

"... O cannot have a full description of the interaction of S with himself (O), because his information is correlation information and there is no meaning in being correlated with oneself. If we include the observer into the system, then the evolution is still unitary, but we are now dealing with the description of a different observer." — boundless

Under any 'consciousness causes collapse' or other anthropocentric take, the friend, being conscious, cannot be in superposition. In any other interpretation, the friend very much can be. — noAxioms

My comment is applicable to your reply. Wigner's friend is is superposition in relation to Wigner. The friend measuring himself sees no such thing and cannot detect his own interference with himself in the other state. In other words, Alice (the friend) is in superposition of having measured vertical and horizontal polarization. Bob (Wigner) sees this and can see Alice interfere with herself (per the OP) yet Alice cannot detect this self-interference. Perhaps that's what they mean by inability to self-measure. Alice needs Bob to tell her she's in this superposition of states.

I grouped this with your quote above because it mentions dealing with the description of a different observer. In the consciousness-causes-collapse interpretation, maybe the consciousness is that introduced second observer.

There is, however a problem here. If Wigner asks his friend before entering in the lab if he sees a definite result, it appears that at this point Wigner already knows that everything in the lab is in a definite state.

No he doesn't. The friend in superposition would also indicate that. Wigner does not learn from that answer that the lab is in a definite state. This is of course assuming that the friend (and the rest of the lab) is very capable of keeping the result a secret, which is why Alice is never a human in such experiments.

So, superposition is now destroyed.

Not if Wigner is unaffected by the actual measurement result, and not the mere taking of it. It is not the case of the classic unseen coin.

The problem is that Wigner still does not know in which state the lab is (including is friend).

If decoherence has occurred, then Wigner has effectively taken a measurement, and the lab is in one state. If Wigner doesn't know the result, that's just an epistemological problem. The result is fact at that point, known or not. A tossed coin between my hand and arm is not in superposition just because I don't know which side is up.

Let's consider the RQM explanation. O = 'Wigner's friend'. O'= 'Wigner'. If O' 'asks' O if the state of S is definite (let's say spin 'up' or spin 'down'), and O answers 'yes', it seems that now according to O, S is in a definite state, let's say 'up', but at the same time for O' the state is definite but it is either 'up' or 'down'. In MWI terms, for O' there are still two non-interfering branches. Yet, when O' enters, there must be an agreement between them.

I disagree with all of this, assuming O can keep a secret, which only certain lab instruments can do. With actual humans, O' and O need not communicate at all. O's measurement affects O' at nearly light speed because no lab is a Schrodinger's box.
Decoherence can be temporarily prevented with distance, but then O and O' cannot communicate. This has been demonstrated with entangled pairs.

Just thought of this: Per time symmetry, is there such a thing as radioactive un-decay, and would such an event constitute an end to a causal chain? If not, I don't think the decay can constitute an uncaused event.
— noAxioms
I do not think that it is reversible, hence I'd say that time symmetry is broken!

I'd bet otherwise, but what do I know? They create some exotic new element in a particle accelerator somewhere. Isn't that un-decay of a sort? Perhaps not. The exotic nucleus decays before it can even acquire some electrons and write home to its mommy that it has grown up and become an atom. I digress. The thing decays into different pieces than the pieces that that they probably smashed together to make it. If it can be the same pieces, that's un-decay in my book.

Bob's knowledge of the paper means nothing: The device may have randomly declined to take a measurement and emit a blank paper. Bob can tell if it happened by measuring superposition or not. So the device taking the measurement, and not Bob's knowledge of that action is what collapses the wave function.
— noAxioms

But in that case this is not a relevant information for Bob.

Exactly. Wigner learning that his friend took the measurement is not relevant information. What's relevant is being affected by the result of that measurement (and not even the knowledge of that result). Being affected by it puts him in the causal chain of that measurement and entangles Wigner (Bob) with the state of the thing measured.
This is what happens in the OP, where the fact that the measurement is done is simply not relevant information to the other observer, and thus the other observer still can measure superposition.

So, to him the state is still undefined (even if he does not believe that...knowledge is not belief). If, instead, the measurement apparatus works perfectly, he really knows that the state is definite (but we fall in the aforementioned problem, where according to Bob, there are two possible states of 'Alice').

What? All this assumes perfect lab equipment. Bob knows the measurement was done (by something else), and yet that irrelevant information does not change the superposition state of the thing measured to Bob. He doesn't need to know or believe anything. He can measure the superposition of the thing directly.


Concerning the counterfactual existence of the moon:

For the alien not to measure the moon, he'd have to put the moon (and everything else) in Schrodinger's box, which is best achieved by making a ship that is one, inside out. Zero information can penetrate from outside to inside the box. He opens the box randomly at some location which happens to be here, and there is some vast wave function of what he might find here that collapses quite improbably to us and our moon. Far more likely it collapses to empty space. Depend on from what distance he came, but it would have to be from over 5 billion light years away because the moon (or the whole solar system) needs to be unmeasured from the start. He'd have to come from a helluva longer distance to find no galaxy here. How far must I travel now to find a place where I have zero information about what is there? A lot further than the event horizon. It cannot be done. We see stuff that is 22 BLY away, which is not possible to reach ever. But the moon is young enough that it can be done.
— noAxioms

I agree that the Moon and everything else are in the Schrodinger's box. But this means that in some sense there is 'something' that corresponds to the Moon in the perspective of the alien. When the alien 'opens the box', the Moon 'collapses' in a definite state according to him.

It most very likely does not. Our moon, or us for that matter, are unlikely things to find in a random sample of totally unknown space. This location (which is known from inside the box due to inertial calculations) is in total superposition of anything that might have evolved from the known state of this area say 8 billion years ago. There wasn't even a galaxy here, but with really good instruments, perhaps it could be computed that there would be. So he's probably not going to pop into totally empty space like he would if he came from even further away.

But this seems to imply that the Moon in some sense 'exists' before the measurement.

Intuitive but not so if the principle of counterfactual definiteness is wrong. Think of it from a MWI perspective. The moon exists in that interpretation, but only in a tiny percentage of possible worlds that might stem from the state (past light cone) of where our alien shut himself in that ship 8 billion light years away. Most of those worlds have no moon, and far fewer have humans. He's not at all likely to witness either of them, but it is hard to imagine finding humans and no moon.

Before that there is no moon to be nonexistent. He can equally declare torrid-planet Vulcan to not exist. In both cases, he's just making stuff up.
— noAxioms
I see. But I would say that the comparison is apt for Vulcan and the definite state of the Moon, not the Moon.

Why any difference? OK, I don't think the torrid planet is going to happen naturally, but perhaps the Vulcans that live there find it convenient for some reason, so they made it that way. It could happen.

Ok. So, you endorse some kind of 'panpsychism' or 'panexperientalism'? (see: https://en.wikipedia.org/wiki/Panpsychism#Panexperientialism)

What? Where'd you get that? More the opposite. Living things are just arrangements of atoms just like pens. There's nothing experiential required to collapse a wave function.

Kind of hard not to observe an electron. Its state might be hidden if put in a box, but we put it there so we know its there. If not in the box, it interacts with other things and that makes it exist. I cannot escape that interaction.
— noAxioms

Well, yes. So, it must 'exist' even if unobserved!.
...
Then maybe we are in agreement! The unobserved electron is not really non-existent.

The interaction is observation. I did not describe an unobserved electron in that bit you quoted. So the unobserved electron is not really unobserved in those examples.

More precisely, it does not exist in a definite state. So, before measurement it simply does not make sense to talk about electrons in definite states.

Right. Even after observation, the state is only somewhat more definite. Never totally definite, as per Heisenberg.

I don't see why it needs to posit indeterminism or not.
— noAxioms

IMO, because results of observations are random.

OK, that sort of determinism. MWI is deterministic because the entire universal wave function is one completely deterministic thing. Consistent histories is not, but I don't know it well enough to say why. With RQM, it sort of depends on how you word things. Observations appear random in every interpretation, so none is deterministic in any sort of subjective way.

Newspeak for the pseudoscientific cause: war is peace, inclusivity is 'too restrictive'. And that's to say nothing of this arrogant reverse-speak where the height of hubris is passed off, bewilderingly, as 'humility': — StreetlightX

It’s because the view that we can arrive at a completely objective understanding of nature, is what is hubristic. We learned we cannot fully determine the nature of the presumed 'ultimate constituents of reality'. So Heisenberg's response to that is a modest one: 'What we observe is not nature itself, but nature exposed to our method of questioning.' Who was it who said 'nature loves to hide?' You see, it leaves space; actually it leaves uncertainty, in a somewhat broader sense, which is salutary, as far as I'm concerned.

I'm not the one advancing an incredibly contentious idea about quantum mechanics requiring human minds to work. — fdrake

Another question: why do you think Bohr made that statement about the fact that quantum physics is 'shocking'? Why do you think he would have said that? What was shocking about it?

So Heisenberg's response to that is a modest one: 'What we observe is not nature itself, but nature exposed to our method of questioning.' — Wayfarer

Which is fine and dandy, except your position is as far removed from Heisenberg's as can be: you're not arguing from some position of epistemological humility: you're arguing that consciousness (or subjectivity or intentionality or mind ... concepts which, because you have no coherent way of sharply defining, are all collapsed into each other in one big, useless mess) is inherent to quantum processes as such.

Frankly, I don't even think you have a coherent idea of what you want to argue - the epistolomological or ontological claim - each very different, each with utterly different implications - so long as you can somehow work whatever fuzzy notion of subjectivity/intentionality/consciousness/mind (again, amalgamated into a indistinct blob of concepts) into the science in some way or another. Which is why you can mangle quotes from Wheeler, Heisenberg, Einstein, Bhor or whoever, and why you're completely incapable of answering the questions posed by fdrake in any way than invoking completely irrelevant rhetorical questions like 'WhY ArEnT YoU ShOcKed?'.

So why do you think Bohr said that?

So it could serve as a rhetorical crutch for charlatans to muddy the waters when utterly incapable of having a discussion grounded in the science, clearly. DiD YoU KnOw BoHr HaD a YiNg YaNg SyMboL oN HiS CoAt Of ArMs MuSt Be SiGnIfiCaNt.

It's true: when we encounter objects, we use our perceptual system. The appearance is our response to the outside, to the thing we are encountering. All it means is our observations will entail how something appears to us (essentially, Kant).

It doesn't mean what we are observing is somewhat not present outside ourselves or not "objective". At most it means there might be more to what we have observed, other "objective" aspects of a thing our system of perception doesn't pick up-- e.g. colours to bees, smells to dogs, echolocation of bat, etc.

The story is not one of experiences creating things that are only themselves, but of how our experiences are/can be a limited in their grasp of "objective" reality. Our cone of vision is limited. Objective reality extends beyond it. We live in a world where flowers are colours bees see, we each have a particular smell a dog senses and trees have an echolocation profile to bats-- all "objectively."

The fact we don't sense those doesn't make them any less of the things we do observe.

How is an observer defined in physics? Certainly not in terms of an actual sentient being perceiving the system. With that said, what relevance do the observers have in the experiment? It seems to me a much clearer way of describing the results would be that a photon can behave inconsistently in certain scenarios.

DiD YoU KnOw BoHr HaD a YiNg YaNg SyMboL oN HiS CoAt Of ArMs MuSt Be SiGnIfiCaNt. — StreetlightX

Bohr did have a ying-yang symbol on his family coat of arms, and I can't see how this was not significant. The ying-yang symbol represented 'complementarity' which Bohr regarded as his signal philosophical insight. And you didn't answer the question, so I'll take a shot at it. QM was 'shocking' because it undermined what Bohr described as the 'Victorian' commitment to the possibility of absolute objectivity, which all boils down to 'mind-independence'.

QM was 'shocking' because it undermined what Bohr described as the 'Victorian' commitment to the possibility of absolute objectivity, which all boils down to 'mind-independence'. — Wayfarer

Tertium non datur. Bohr at least was not so juvenile as to think that the latter conclusion ("all boils down to 'mind-independence") at all follows from his declaration of 'shock'. Your usual mis/nonreading claptrap. Not even your - as usual, unconxteualized - citations mean what you want them to.

You are a mod here, right? So how is it that you believe that a string of ad homs amounts to anything? I think I understand why my posts illicit such a reaction, from you but there's obviously little use in trying to spell it out.

Which one's the ad hom? Pointing out a basic logical fallacy? Noting that you consistently and maliciously skew Bhor's meaning so as to impute to him a position he never held? Pointing out that you always shy away from discussions of the science and recourse to trivialities like coats of arms and out-of-context quotes? All of the above?

I respond to you the way I do because your posts on this topic are frequently scientifically dishonest, conceptually loose, and full to the brim with (non-)argument-by-allusion. The two instances of double-speak I pointed out are emblematic of all your posts on this topic.

Bhor's meaning — StreetlightX

It's all ad homs, it's all you have. And that's a misspelling.

One problem is understanding 'mind' or 'consciousness' as "the attribute of a person" - of what goes on in an individual's mind. This is plainly what Wheeler is referring to when he says that '"Consciousness' has nothing whatsoever to do with the quantum process". He is pointing to 'what happens inside an individual observer's mind'. And I agree with that.

But 'an observation' in this context, is not a matter of what an individual thinks. It is embedded in a context of theory and practice, of which scientific instruments are a part. That is why there are peer-reviewed journals and consensus. "An observation", in this context, is a data-point, one piece of information that is interpreted in the light of theory. That is how 'consciousness' manifests in this context, and the sense in which 'observation' is meaningful.

An observation", in this context, is a data-point, one piece of information that is interpreted in the light of theory — Wayfarer

If by 'this context' you mean Wheeler, there is no point, not a single mention - quote it, I fucking dare you - at which Wheeler even remotely refers observation to 'a piece of information interpreted in the light of theory (it's this qualification, which I've italicized, which is an utter fib on your part). Every single one of Wheeler's examples deals with registration by scientific instruments which interact with - and thus 'participate' with - the quantum phenomenon in question:

"The observing device in the here and now... has an irretrievable consequence for what one has the right to say about a photon that was given out long before there was any life in the universe" ; And repeated again two pages later: "Registering equipment operating in the here and now has an undeniable part in brining about that which appears to have happened"; And early on: "Bohr emphasized that ... we are dealing with two different experiments... the one with the half-silvered mirror removed ... [and] the one with the half-silvered mirror in place"; Elsewhere and most significantly: "A phenomenon is not yet a phenomenon until it has been brought to a close by an irreversible act of amplification such as the blackening of a grain of silver bromide emulsion or the triggering of a photo detector";

At every point is 'observation' linked to, and articulated in terms of, the physical set-up of the scientific apparatus in place. At no point is the wider body of 'theory' as set out by a community of scientists invoked necessary to bring about a quantum phenomenon: the phenomenon is 'brought to a close' by the interaction with the instruments: it goes no further, and certainly requires no 'consciousness' to swoop in from out of nowhere to make it an observation. And all this to say nothing about your attempt to insulate Wheeler's unequivocal statement about consciousness by once again skewing, with zero warrant, the statement to refer to 'what happens inside an individual observer's mind': no, it refers quite unambitiously, before your twisted attempt at blatant sophistry, to consciousnesses having a role in the 'quantum phenomenon' tout court - Wheeler is about as clear and blunt as can possibly be on this point:

"Does the record [of an act of registration] subsequently enter into the 'consciousness' of some person, animal, or computer? Is that the first step in translating the measurement into "meaning" [note how the measurement is deliberately and distinctly separated from meaning, unlike your sophistic attempt to run the two together - SX] - meaning regarded as "the joint product of all the evidence that is available to those who communicate"? Then that is a separate part of the story, important but not to be confused with 'quantum phenomenon'" - a deliberate confusion which you bathe in from head to toe.

Thanks for clearing up the issue of the interference. It makes more sense now.

Yes. This seems to align with Wittgenstein's private language argument. Our language develops via interactions with other people and things in the world. By which we come to learn things about ourselves as well. — Andrew M

Very interesting point :up:

As for why that should make a difference, my thought is that there are many possible spacetime paths between the present moment for O' and the measurement event for O. Similar to the Andromeda paradox, perhaps the time of the event for O can potentially be in the future of O' (until fixed in the past of O' by an interaction). — Andrew M

Ok, I see. Much confusion about this arises probably from an unconscious tendency to think in terms of a 'singular history' (i.e. a fixed present for everyone...), so to speak. But that's precisely what both Relativity (if one does not want to endorse the idea of a 'block universe') and RQM question. It is, however, simply very difficult (or impossible?) to 'overcome' that tendency...

Ok. So, you endorse some kind of 'panpsychism' or 'panexperientalism'? (see: https://en.wikipedia.org/wiki/Panpsychism#Panexperientialism)
What? Where'd you get that? More the opposite. Living things are just arrangements of atoms just like pens. There's nothing experiential required to collapse a wave function. — noAxioms

Ok, I see.

I actually made that comment following this remark of yours:

I don't follow. The perspective of the pen seems the same as that of a human being there. The pen just pays a lot less attention. I honestly give humans or any living thing no special regard in this topic. — noAxioms

My point was that a 'panexperientialist' might agree with this remark. I believe that for some forms of 'panexperientialism', there are degrees of 'sentience' and ours is just more complex. This is more or less the point of views like psycho-physical parallelism.

Anyway, sorry for the misunderstanding! I will answer in detail to your post later.

(BTW, unfortunately, I will soon have less time available so I will probably leave the discussion...)