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
I really believe that you don't see the problem. — Wayfarer
And what they DON'T share is 'the ability to form a perspective'. — Wayfarer
'the universe seems more a great mind than a great machine') — Wayfarer
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
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
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
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
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
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
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
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.
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
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
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
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
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 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
Cool. Few agree with that. It is controversial. — noAxioms
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
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 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
I don't see why it needs to posit indeterminism or not. — noAxioms
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
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, 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
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
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
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
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
Note, this is not just the claim that humans can act as observers; but that only humans can act as observers. — fdrake
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
that unforgettable Kantian thesis, subjective idealism. It is almost as if he never argued against subjective idealism in the Critique of Pure reason. — fdrake
In my opinion Wheeler's view is a bit ambiguous — boundless
Do you think any other kinds of beings that we know of can actually do physics? — Wayfarer
"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
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
-John Stewart Bell, 1981, Quantum Mechanics for Cosmologists."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?"
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).
It makes perfect sense. The photon cannot take one path, unmeasured. That would be the counterfactual definiteness that any local interpretation denies. — noAxioms
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
I don't see that as superimposing or interference. — noAxioms
My issue with these statements is that it takes too restrictive a view of what 'observation' entails. — Wayfarer
Acknowledging the centrality of the human is actually a gesture of humility. — Wayfarer
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, 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
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
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
(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
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
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.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
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.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.
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.So, superposition is now destroyed.
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.The problem is that Wigner still does not know in which state the lab is (including is friend).
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.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'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.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!
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.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.
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.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').
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.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.
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.But this seems to imply that the Moon in some sense 'exists' before the measurement.
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.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.
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.Ok. So, you endorse some kind of 'panpsychism' or 'panexperientalism'? (see: https://en.wikipedia.org/wiki/Panpsychism#Panexperientialism)
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.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.
Right. Even after observation, the state is only somewhat more definite. Never totally definite, as per Heisenberg.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.
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.I don't see why it needs to posit indeterminism or not.
— noAxioms
IMO, because results of observations are random.
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
I'm not the one advancing an incredibly contentious idea about quantum mechanics requiring human minds to work. — fdrake
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
DiD YoU KnOw BoHr HaD a YiNg YaNg SyMboL oN HiS CoAt Of ArMs MuSt Be SiGnIfiCaNt. — StreetlightX
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
Bhor's meaning — StreetlightX
An observation", in this context, is a data-point, one piece of information that is interpreted in the light of theory — Wayfarer
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
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. 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
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
Get involved in philosophical discussions about knowledge, truth, language, consciousness, science, politics, religion, logic and mathematics, art, history, and lots more. No ads, no clutter, and very little agreement — just fascinating conversations.