At every point is 'observation' linked to, and articulated in terms of, the physical set-up of the scientific apparatus in place. — StreetlightX
you may as well say, if there were no microscopes guided by our theories of optics, there'd be no bacteria — StreetlightX
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). — Andrew M
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. — 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. — noAxioms
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. — noAxioms
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. — noAxioms
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. — noAxioms
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. — 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
But in that case this is not a relevant information for Bob. — boundless
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. — noAxioms
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'). — boundless
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. — 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.. — boundless
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.. — noAxioms
But this seems to imply that the Moon in some sense 'exists' before the measurement.. — boundless
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. — noAxioms
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. — noAxioms
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. — noAxioms
Right. Even after observation, the state is only somewhat more definite. Never totally definite, as per Heisenberg. — noAxioms
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. — noAxioms
The interferometer seems to be the only measurement taken (the only observer). Anything outside that is only noting what was measured by that device. The photon definitely takes both paths relative to the interferometer because it takes no measurements until the paths join up again.For RQM, the path travelled is only counterfactually indefinite for the observer outside the interferometer. — Andrew M
Those mirrors don't take any measurement since they retain zero state from the light that reflects from them. If they did take a measurement, the photon would take only one path and not interfere with itself at the final beam splitter. That would effectively be putting a detector on each of the slits in the double slit setup. No interference is observed in such a case.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).
The perception as a rotation is an illusion made possible by our near bilateral symmetry. But my wife in the mirror looks sort of unfamiliar to me, and my cat is unrecognizable. I don't look that way to myself because I rarely see myself, only my reflection.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.
You outright lie, misrepresent, and quite literally make things up — StreetlightX
That seems to work. I considered myself in relation to that alien who came from far away and has yet to observe what's here. To that alien, I am very much in a superposition of lots of states, most of which do not contain a 'me'. So it is a state of superposition of 'here' more than it is a state of superposition of 'me'. I don't need the alien to tell me that such a superposition state exists. He's still in his box, but conveying what he knows is outside, which is very little.Well, maybe you are right. But IMO, it suggests that the only that 'Alice' can know about herself is to consider herself in relation to 'someone else'. — boundless
Sure about my statement that decoherence is a measurement? The two are almost synonyms.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.
— noAxioms
Are you sure about this?
IMHO decoherence alone cannot, strictly speaking, give you a definite outcome.
MWI is misrepresented if it has a concept of branches with identities. There is never a specific branch. The measurement is taken by nearby matter but not yet by something further away, so it is still in superposition from that PoV. That's an RQM description, but MWI never really has distinct worlds. The cat is both dead and alive (same world to Schrodinger, different worlds to the cat). Opening the box entangles Schrodinger with the cat and now there are two of both, at least from their PoV. Each Schrodinger I suppose finds himself entangled with a specific branch, but there is no identity to the branch, only the wave function of some arbitrary system, which is different to different observers.More precisely, it removes the superposition but it is not enough to 'select' a specific 'branch'. That's why MWI supporters like decoherence. Decoherence explains the absence of superposition. But the are still the non-interfering branches.
Same thing, different spin.In my understanding, Consistent Histories instead says that interference disappears due to decoherence and a definite outcome is 'selected' probabilistically via the Born Rule.
With interpretations where selecting goes on, I suppose that needs explaining. Here are all these possibilities, and only one becomes real and the rest discarded. What makes that choice?Our disagreement is probably due to my possible misunderstanding of decoherence, then. AFAIK, decoherence can explain the disappearance of superposition, not the 'selection' of a specific branch.
Bob's knowledge of the action can be obtained without consulting the device that did the action, so that information passed on by the device is not relevant. Bob has independent access to this information already.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.
— boundless
It might be purple and tiny, but if there's one and there are locals living on what it orbits, then I suppose to them it would also be 'the moon' just like it is for us. There's a probability for finding that purple one and a probability of finding me.Ok, thank you again! I believe that now I see your point. So, there is at best a 'probability' of finding the Moon but not 'the Moon'.
I cannot measure the moon right now and not find it, so that limits my possible class of results, sure. The alien measuring the same thing will likely get no-solar-system here since he never measured one in the first place like I did. My measurement collapsed a much simpler wave function that has almost zero possibility of no-moon.So this means that the Moon is a possible outcome of the 'measurement'. The same goes for an electron, an atom and so on. 'Measurements' are random process but at the same time they can give only a class of result.
Example? I measure the moon twice and find it both times? Be freaky to get a different result. But I find it because I has already measured it prior, so its existence to me is about as defined as it can be.If one accepts counterfactual definiteness, this is explained by the fact that we, indeed, find something already there. If not, it is still undeniable that there are regularities. So, I wonder how we can explain them, if we can (unfortunately, this leads us to metaphysics...).
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. — StreetlightX
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... — boundless
The photon definitely takes both paths relative to the interferometer because it takes no measurements until the paths join up again. — noAxioms
Now the issue is that any information collected by the "reference frame", as "inanimate object", needs to be interpreted by human beings before it is useful as observational evidence. The interpretation is theory laden. So the idea that a reference frame can give observational information which is independent of intentionality is false.
The problem is that the theory laden interpretation cannot account for all the possibilities. For example, I put a dish of water in the sun, as my observer. I measure that water every fifteen minutes and derive a rate of evaporation as the day progresses. But I am assuming that evaporation is the only thing happening, I don't know if something else happened to the water, like a creature went and drank some when I wasn't looking. So the inanimate reference frame, as an observer, is only as good, and reliable, as the principles used to interpret the information. — Metaphysician Undercover
I've seen that people use the word 'know' a lot when talking about observation/information transmission/interactions involving energy exchange, but 'know' looks to be used in different contexts to where just 'correlation' would be appropriate - like, if 2 particles are entangled, it doesn't seem typical to say that one particle 'knows' the state (distribution) of the other. Examples in this thread are the use of 'Alice knows that Bob knows...' towards the start in the discussion between boundless, @noAxioms and @Andrew M.
What do you mean when you use 'know' in this sense? What is the (range of appropriate) physical interpretation(s) of it, if it has one? — fdrake
RQM indeed does not claim anything about what path is taken. Any statement about the path taken (such as it taking one or the other) would be a counterfactual one, and RQM is not a counterfactual interpretation. So perhaps I was in error stating that it takes both paths. Statements about unmeasured things are meaningless in RQM.I think you're mixing the issue of how the result at the detectors is calculated (by summing path amplitudes) with the question of what physically happens in the interferometer. RQM doesn't claim that the photon would take both paths, only that accounts of an event can differ for different observers which is a weaker claim. — Andrew M
I'm not sure I understand your claim. Your example seems to merely raise ordinary epistemic issues around observations and experiments. There's always the possibility of some factor undermining your conclusion regardless of how careful you are or how you define your terms. For example, perhaps you observed the dish all day, but there was leak in the dish resulting in you recording an incorrect evaporation rate. — Andrew M
What do you mean when you use 'know' in this sense? What is the (range of appropriate) physical interpretation(s) of it, if it has one? — fdrake
That seems to work. I considered myself in relation to that alien who came from far away and has yet to observe what's here. To that alien, I am very much in a superposition of lots of states, most of which do not contain a 'me'. So it is a state of superposition of 'here' more than it is a state of superposition of 'me'. I don't need the alien to tell me that such a superposition state exists. He's still in his box, but conveying what he knows is outside, which is very little. — noAxioms
Sure about my statement that decoherence is a measurement? The two are almost synonyms.
Some nucleus in the moon is in superposition of decayed/not-decayed. That decay (or lack of it) affects its environment, so it cannot be contained. The immediately surrounding matter is quickly in a completely different state because of it, so the wave function collapses into a definite outcome for at least that matter in state A or B. That's a measurement taken of the decay event by the surrounding matter. That's decoherence of the atom in superposition, entangling the matter around it into its superposition. Same thing. Within a second or two, that superposition state entangles me as well, even at this distance, and the fact of what happened to that atom becomes a definite outcome to me. — noAxioms
MWI is misrepresented if it has a concept of branches with identities. There is never a specific branch. The measurement is taken by nearby matter but not yet by something further away, so it is still in superposition from that PoV. That's an RQM description, but MWI never really has distinct worlds. The cat is both dead and alive (same world to Schrodinger, different worlds to the cat). Opening the box entangles Schrodinger with the cat and now there are two of both, at least from their PoV. Each Schrodinger I suppose finds himself entangled with a specific branch, but there is no identity to the branch, only the wave function of some arbitrary system, which is different to different observers.
A quote from Tegmark on the subject: https://arxiv.org/pdf/quant-ph/9709032.pdf
"[MWI (per Everett) does not posit that] at certain magic instances, the the world undergoes some sort of metaphysical “split” into two branches that subsequently never interact." — noAxioms
With interpretations where selecting goes on, I suppose that needs explaining. Here are all these possibilities, and only one becomes real and the rest discarded. What makes that choice? — noAxioms
I leave it to them. MWI makes them all real, — noAxioms
and RQM doesn't really have selections that happen. A measurement isn't really done by any observer who is but an event with only a history, but not the ability to 'select'. I cannot measure the photon, but I can have already measured it, so no 'selection' is ever done. At least that's how I interpret RQM. — noAxioms
Bob's knowledge of the action can be obtained without consulting the device that did the action, so that information passed on by the device is not relevant. Bob has independent access to this information already. — noAxioms
It might be purple and tiny, but if there's one and there are locals living on what it orbits, then I suppose to them it would also be 'the moon' just like it is for us. There's a probability for finding that purple one and a probability of finding me.
If at any time I take any measure at all of the alien's approaching ship, then there is a 100% chance that the alien that steps out will find me. This is unremarkable. From a MWI perspective, the alien, upon opening his door will 'split' into every possible world that could be found and all those worlds would see the alien. That is decoherence of the state of 'here' from massive superposition to something concrete. — noAxioms
I cannot measure the moon right now and not find it, so that limits my possible class of results, sure. The alien measuring the same thing will likely get no-solar-system here since he never measured one in the first place like I did. My measurement collapsed a much simpler wave function that has almost zero possibility of no-moon. — noAxioms
Example? I measure the moon twice and find it both times? Be freaky to get a different result. But I find it because I has already measured it prior, so its existence to me is about as defined as it can be. — noAxioms
I think you're mixing the issue of how the result at the detectors is calculated (by summing path amplitudes) with the question of what physically happens in the interferometer. RQM doesn't claim that the photon would take both paths, only that accounts of an event can differ for different observers which is a weaker claim. — Andrew M
RQM indeed does not claim anything about what path is taken. Any statement about the path taken (such as it taking one or the other) would be a counterfactual one, and RQM is not a counterfactual interpretation. So perhaps I was in error stating that it takes both paths. Statements about unmeasured things are meaningless in RQM. — noAxioms
Even beyond its foundational role in relativistic field theories, locality constitutes, therefore, the base of the relational methodology: an observer cannot, and must not, account for events involving systems located out of its causal neighborhood (or light-cone).10
[Footnote 10] We can take this observation as an echo in fundamental physics of the celebrated: “7. Whereof one cannot speak, thereof one must be silent” [from Wittgenstein's Tractatus]
Right, that's the point, there are epistemic issues with "observations" no matter how you define the term. Sometimes the "observer" might be focused so as to miss many possibly relevant factors. In a human observer, this is one's attention. The person might observe with eyes and not ears, or vise versa, and miss some relevant information. In the case of an observing machine, its capabilities are limited by the intent of the design. — Metaphysician Undercover
My issue with these statements is that it takes too restrictive a view of what 'observation' entails. — Wayfarer
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. — Wayfarer
Again the act of observation is implicated in determining the outcome, which is the point at issue. — Wayfarer
"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. — Wayfarer
I think we observe it every day, but you take it as an ordinary observation. A rainbow is quite impossible to see without superposition. The lens of my eye would not work without it. Most directly, Bob in the OP is able to directly measure superposition even after Alice has taken a measurement.I agree with what you said here. But I am not sure that it solves the 'measurement problem' completely. It explains why we do not observe superposition. — boundless
If your interpretation says that a single outcome occurs.BUT you need an additional assumption in order to explain why only one outcome actually occurs.
I never used the word 'universe' in what you quoted since it means such different things to different people.Not sure why you think you are disagreeing with me. If by 'universe' in MWI you mean the 'universal wavefunction' then I agree with you and Tegmark.
There is splitting of a sort in RQM also. To me, the photon is polarized vertical. Relative to another me, the photon is horizontal. Relative to a 3rd reference, there's not even a me or a photon. Sounds like those are separate worlds, some connected more than others.But this is not normally what one means by 'world' or even 'universe', so, in fact, I think that one can definitely say that there is splitting. And this is for me a reason to not accept MWI.
That very much goes against the Everett postulate. It is a different interpretation and should have a different name.Well, I know that some supporters of MWI consider only one branch as 'real' and other branches as 'unreal' ( e.g. apparently Hawking and Weinberg are supporters of this 'flavor' of MWI, see the Wikipedia article on MWI).
OK, I see better now what CH proposes that is unique. You'd think they'd put that in plain language in the introduction somewhere. How is what Hawking and Weinberg push different from the CH view then? Why add a 2nd postulate when the first one perfectly predicts the experience we have?But unfortunately, MWI cannot IMO justify that without an additional axiom (as in Consistent Histories, where there is the axiom that a 'history' is selected probabilistically. In dBB one 'branch' is occupied by particles).
So the inhabitants of those 'other branches' don't continue to post in their forums philosophical discussions about how their world being more real than ours? The Schrodinger equation says they very much do, and none of these additional postulates make any modifications to that.My point is that this version of MWI simply does not explain why the 'other branches' are 'unreal'.
I'm not sure that Everett did. It was a physics interpretation of QM, not necessarily making any metaphysical assertion. MWI as we know it might have been built on Everett's work, but I don't believe he called it 'MWI'.On the other hand, Deutch, DeWitt etc consider all branches as physical, 'real'. So it is not just me that understands MWI in that way.
I figured. That one is hard to explain. RQM says such and such is real to a second thing, say 'me', but 'me' needs definition. A worldline doesn't work because it isn't defined after a certain point. So that point (one event) is 'me', and that event cannot take a measurement. It may or may not have an abstract worldline leading up to it, but none has a worldline leading from it. Hence an event (me) can have already taken a measurement, but it cannot take a new one. Such new measurement are taken by future events, and the future does not exist to 'me', thus 'I' cannot take a new measurement, only something else which will happen to include 'me' as part of its past worldline. So 'I' do not select anything and thus what is real never changes for me. One of my future events (say one that measures a vertical polarity) can have already measured that polarity and that event considers that state of affairs to be real to it, but it never becomes real to (is selected by) any particular 'me' event, which, being an event, cannot flow through the selection process to its future, however much it might intuitively anticipate doing so.and RQM doesn't really have selections that happen. A measurement isn't really done by any observer who is but an event with only a history, but not the ability to 'select'. I cannot measure the photon, but I can have already measured it, so no 'selection' is ever done. At least that's how I interpret RQM.
— noAxioms
I do not understand this.
I never observe an electron passing through a slit. If I do, it goes through one and doesn't interfere with itself. So I don't get this scenario. What I have observed is where the electron hit the screen, or the pattern from many such electrons. At no point does any local interpretation of QM interpret the electron taking one path to get there. I think pilot wave theory might assert it, but they've really shot that one to hell when they put a partition between the two slitsTake the double-slit experiment. When you observe that an electron passes through slit A then you either explain this observation of a single outcome via a selection or you accept that the 'other history' is equally true as in MWI. So, I believe that both CI and RQM leave it unexplained.
Take a point exactly 50 billion LY north. There is a nearly pure wavefunction describing what exists there, and one set of solutions to that wave function is finding a moon like ours nearby, or just an electron, or whatever. If there was a way for 'me' to just suddenly teleport and take a measure of that point, under MWI, I (a whole multitude of 'I', however many it takes) would measure every one of these possibilities. Under RQM, each of these possibilities would be real to the 'me' that appears there. Same story, but different wording. Both views also say that to an observer on that moon or at any of the other possible states there, I'd probably not suddenly appear in front of them. My appearance there is as unlikely as is theirs to me.I agree again. My point however is that there is no explanation why there is a probability of finding a Moon, an electron or whatever in the first place. If one accepts hidden-variables this is of course explained.
How does one go about 'finding' an electron? What sort of measurement are we talking about here? With the moon, sure, you look up on a clear day and see if there's one there, but for an electron, it seems more difficult to not find one since they're everywhere. OK, 50 BLY away I might not find one in a sample radius since odds are I encounter fairly empty space, but I'm not sure if that's what you mean.Right, you find the Moon again because you already measured it. As you say it is not that remarkable. It is more remarkable that you find an electron probabilistically when you perform a measurement without hidden variables.
Such an interpretation would seem to propose counterfactual definiteness. Somewhere off to the side, some measurement is taken by not-me and causes some state to be real and the other results not.Just a curiosity: has anyone ever suggested an interpretation where the 'universal wavefunction' is real (like in MWI) and a single branch is 'selected' by a probabilistic rule (as in Consistent Histories as I understand it)? — boundless
An interpretation that such selecting of reality is going on outside of some privileged light cone is doing exactly this: accounting for events involving systems located out of its light cone. As such, the interpretation bears little resemblance to local interpretations like MWI or CH as I understand it.Even beyond its foundational role in relativistic field theories, locality constitutes, therefore, the base of the relational methodology: an observer cannot, and must not, account for events involving systems located out of its causal neighborhood (or light-cone).10 — Rovelli
Most directly, Bob in the OP is able to directly measure superposition even after Alice has taken a measurement. — noAxioms
If your interpretation says that a single outcome occurs. — noAxioms
I never used the word 'universe' in what you quoted since it means such different things to different people. — noAxioms
There is splitting of a sort in RQM also. To me, the photon is polarized vertical. Relative to another me, the photon is horizontal. Relative to a 3rd reference, there's not even a me or a photon. Sounds like those are separate worlds, some connected more than others. — noAxioms
That very much goes against the Everett postulate. It is a different interpretation and should have a different name. — noAxioms
OK, I see better now what CH proposes that is unique. You'd think they'd put that in plain language in the introduction somewhere. How is what Hawking and Weinberg push different from the CH view then? Why add a 2nd postulate when the first one perfectly predicts the experience we have? — noAxioms
That's why I like RQM which is the main Everett postulate: "All isolated systems evolve according to the
Schrodinger equation" without MWI's secondary metaphysical postulate that said equation is real. The latter postulate makes no change to the evolution of the equation and thus 'what happens', and thus isn't needed to explain what the experience would be. — noAxioms
I'm not sure that Everett did. It was a physics interpretation of QM, not necessarily making any metaphysical assertion. MWI as we know it might have been built on Everett's work, but I don't believe he called it 'MWI'. — noAxioms
I figured. That one is hard to explain. RQM says such and such is real to a second thing, say 'me', but 'me' needs definition.
...
That was a very eternalist way of describing things, but I cannot think of a way to do it in presentist terms. I consider 'observers' (that to which a reality relates) to be events in RQM, and consequently almost anything can be such an event. Humans are not special at all. Not sure if empty space is a valid event since there is nothing there to take a measurement of anything. It has to be something capable of being affected by state. — noAxioms
I never observe an electron passing through a slit. If I do, it goes through one and doesn't interfere with itself. So I don't get this scenario. What I have observed is where the electron hit the screen, or the pattern from many such electrons. At no point does any local interpretation of QM interpret the electron taking one path to get there. I think pilot wave theory might assert it, but they've really shot that one to hell when they put a partition between the two slits — noAxioms
Take a point exactly 50 billion LY north. There is a nearly pure wavefunction describing what exists there, and one set of solutions to that wave function is finding a moon like ours nearby, or just an electron, or whatever. If there was a way for 'me' to just suddenly teleport and take a measure of that point, under MWI, I (a whole multitude of 'I', however many it takes) would measure every one of these possibilities. Under RQM, each of these possibilities would be real to the 'me' that appears there. Same story, but different wording. Both views also say that to an observer on that moon or at any of the other possible states there, I'd probably not suddenly appear in front of them. My appearance there is as unlikely as is theirs to me. — noAxioms
Such an interpretation would seem to propose counterfactual definiteness. Somewhere off to the side, some measurement is taken by not-me and causes some state to be real and the other results not.
From the Rovelli bit you quoted in the post above: — noAxioms
Even beyond its foundational role in relativistic field theories, locality constitutes, therefore, the base of the relational methodology: an observer cannot, and must not, account for events involving systems located out of its causal neighborhood (or light-cone).10
— Rovelli
An interpretation that such selecting of reality is going on outside of some privileged light cone is doing exactly this: accounting for events involving systems located out of its light cone. As such, the interpretation bears little resemblance to local interpretations like MWI or CH as I understand it.
Per you post above, it seemed that Hawking and Weinberg posited something along these lines, so I wonder what they'd say to my point here. — noAxioms
There is certainly no one version of probably any of the interpretations, but there are probably some fundamental features that characterize each. Take that away and it isn't really a different version of something (like RQM), but rather a whole different interpretation. So sure, all outcomes occur, but they don't all occur to a given X (or anything else). They very much occur (are real) to things Y that interact with (measure) them.But this is IMO the position of RQM. On the other hand, I do not believe that there is only one 'version' of RQM. In fact, I believe that there are different relational approaches to QM. So, maybe some versions accept that all outcomes occur. — boundless
Tegmark is kind of funny this way. An MWI person might refer to 'universe' as the one universal wave function and all these resulting worlds, but Tegmark often uses 'multiverse' splitting into universes so that it falls under his type-3 multiverse. But other times he speaks of worlds and one universe.I never used the word 'universe' in what you quoted since it means such different things to different people.
— noAxioms
Yeah, but when MWI-supporters deny that there is a 'splitting', they actually do not usually deny that there is a splitting that others have in mind IMO (of course, there are exceptions).
Sounds good.Yes, there is a splitting in this sense. What I meant is that for each reference, there is no splitting. In your example of the polarization, if 'I' observe a horizontal polarization the observation of a vertical polarization does not occur in RQM (for 'me'). In MWI, it does.
It isn't stated in MWI because it doesn't need it. All worlds are real, so none of them is in need of selection over the other. It's only when you have a metaphysical selecting (dice throwing as Einstein disdained) that such a postulate is introduced.OK, I see better now what CH proposes that is unique. You'd think they'd put that in plain language in the introduction somewhere. How is what Hawking and Weinberg push different from the CH view then? Why add a 2nd postulate when the first one perfectly predicts the experience we have?
— noAxioms
IMO, the difference is that in the MWI 'version' of Hawking and Weinberg the axiom is not stated (in fact, my 'proposed interpretation' consisted to add this axiom).
Everett was forced to reign in his views in order to gain acceptance. It was dumbed-down to a reasonably finite number of worlds, not this full blown Hilbert space thing. That has since been put back, but I wonder what else never was. It's not like Everett really ever contributed much after being driven from the physics community like he was. He needed more of the PR engine that was behind Einstein. His thinking was too out-of-box for the time.Agreed! I believe that there is some controversy on Everett's own views.
I think information preservation principle gives the persistence needed. If I measure the photon and then the big boot hits me from the sky (Python-style) before I can pass on the findings, was the measurement done? Information preservation says yes, the boot doesn't erase that.some persistence over time seems required.
Agree. Nothing to collapse a wave function.Regarding empty space, I am not sure if it can be an 'observer' in RQM.
Maybe so. Not up on QFT enough to comment with anything but the ignorance PoV.What about QFT? In QFT, the 'vacuum state' is not really 'void'. So, maybe quantum fields can be used as 'events'? (hope this makes sense)
I say it isn't selected at all.Anyway, I do not believe that this affect my point. I would say that the point where the screen is hit is 'selected randomly'.
There is certainly no one version of probably any of the interpretations, but there are probably some fundamental features that characterize each. Take that away and it isn't really a different version of something (like RQM), but rather a whole different interpretation. So sure, all outcomes occur, but they don't all occur to a given X (or anything else). They very much occur (are real) to things Y that interact with (measure) them. — noAxioms
Tegmark is kind of funny this way. An MWI person might refer to 'universe' as the one universal wave function and all these resulting worlds, but Tegmark often uses 'multiverse' splitting into universes so that it falls under his type-3 multiverse. But other times he speaks of worlds and one universe. — noAxioms
So worlds don't actually split off, but different terms simply become sufficiently decoherent for their interaction to become negligible. — noAxioms
Everything in that paper seems to apply to RQM since it seems to separate out the needless metaphysical assertions piled on top of the one postulate. Section III-C seems to offer a choice between effectively MWI and RQM, making RQM a valid offshoot of MWI physics. — noAxioms
Yes, there is a splitting in this sense. What I meant is that for each reference, there is no splitting. In your example of the polarization, if 'I' observe a horizontal polarization the observation of a vertical polarization does not occur in RQM (for 'me'). In MWI, it does. — boundless
Sounds good. — noAxioms
It isn't stated in MWI because it doesn't need it. All worlds are real, so none of them is in need of selection over the other. It's only when you have a metaphysical selecting (dice throwing as Einstein disdained) that such a postulate is introduced. — noAxioms
Everett was forced to reign in his views in order to gain acceptance.
...
His thinking was too out-of-box for the time. — noAxioms
some persistence over time seems required. — boundless
I think information preservation principle gives the persistence needed. If I measure the photon and then the big boot hits me from the sky (Python-style) before I can pass on the findings, was the measurement done? Information preservation says yes, the boot doesn't erase that. — noAxioms
Regarding empty space, I am not sure if it can be an 'observer' in RQM. — boundless
Agree. Nothing to collapse a wave function. — noAxioms
What about QFT? In QFT, the 'vacuum state' is not really 'void'. So, maybe quantum fields can be used as 'events'? (hope this makes sense) — boundless
Maybe so. Not up on QFT enough to comment with anything but the ignorance PoV. — noAxioms
Anyway, I do not believe that this affect my point. I would say that the point where the screen is hit is 'selected randomly'. — boundless
I say it isn't selected at all. — noAxioms
What exactly do you mean by "given state"? Would saying that nature does not exist in a given state mean that nature is "really" not anything, that there is no 'way things are' at all? If there were no "objective states of affairs that are apprehended differently by different observers", then how could there be any commonality of observation at all? Where would the commonality that is obviously attained originate? If there are no "ways things are", then what is science studying, and how would science then be possible at all? — Janus
Some time ago there was a meeting of philosophers, most of them positivists, here in Copenhagen, during which members of the Vienna Circle played a prominent part. I was asked to address them on the interpretation of quantum theory. After my lecture, no one raised any objections or asked any embarrassing questions, but I must say this very fact proved a terrible disappointment to me. For those who are not shocked when they first come across quantum theory cannot possibly have understood it. Probably I spoke so badly that no one knew what I was talking about.
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