## The role of observers in MWI

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"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?"

I have often addressed that question. Again it's a question of philosophy not physics. For practical purposes you can assume the world has been there all along, just as is. But that is a methodological assumption, not a metaphysical postuate. That is what I think Sean Carroll doesn't see.

Ever seen the Andrei Linde interview on Closer To Truth? He talks explicitly about the role of the observer.

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OK, maybe, but it’s a very different definition. Is there an example of something that isn’t [a computable number]?
— noAxioms

Yes, one can use diagonalization to produce a number that isn't in the set. Another example is the probability that a randomly constructed computer program will halt (Chaitin's constant).
Both qualify as a computable number. The diagonalization method used with an ordered list of all rational numbers nicely produces a number that isn’t rational, but is very much computable by the definition on the site you linked. All one has to do to get n bits of precision is to list the first rational numbers and take a bit from each, a very finite task.
As for Chaitin’s constant, there is this from the site:
“Each Chaitin constant Ω has the following properties:
• It is algorithmically random (also known as Martin-Löf random or 1-random). This means that the shortest program to output the first n bits of Ω must be of size at least n − O(1).“

The existence of an algorithm to output the first n bits seems make it a computable number since they say what it takes to compute it to some arbitrary finite precision. I say that, but then I linked over to a page on normal numbers and it says this: “For example, Chaitin’s constant is normal (and uncomputable).“ which means I’m reading that listed property above wrong. I think I’m missing the ‘at least’ part.

A universal Turing Machine can simulate itself by accepting, as input, a description of itself and running it. See Turing completeness.
The page seems to assume infinite memory and infinite machines states. The more memory you need to access, the more states you need, and a machine emulating something needs more memory/states than the thing being emulated. The page seems to assume for instance a generic language where say pointers are not of finite size. But I’ll accept the definitions used on the page and withdraw my statement.

Concerning the paper on the Wigner friend thing:
The experiment matches the predictions of standard quantum mechanics, and thus also the predictions of MWI.
I agree with that, but I wasn’t talking about predictions. I was talking about language describing things other than the results.

So it doesn't challenge MWI on those grounds. But also, on an MWI view, it's disputable whether a measurement actually took place since no decoherence (and thus no world branching) occurred.
Another reason why I don’t like the suggestion of actual metaphysical branching of worlds. Everett never suggested it, but DeWitt added that, coining the term ‘MWI’ in the process. I prefer Rovelli’s take on it where there is no ‘actual’ about any of the measurements, and observation serves only an epistemological purpose.

So, if one accepts the authors' definitions for an observer and measurement, then one of the assumptions of free choice, locality, and observer-independent facts must be false.
That just sounds like Bell’s theorem (old news). What in 2019 was added to that?
Which is why Deutsch's proposal to use an AI on a quantum computer would be an important and compelling experiment.
Sorry, but I don’t see what the AI adds that any simple device (like the circuit on the camera) doesn’t.

You're rejecting the "observer-independent facts" assumption, which is fine.
If I have to drop something, that one seems far preferrable to the others. I don’t reject it since it cannot be disproved.

Bottom line is that I haven’t understood the proposal enough to clarify how the different interpretations make different predictions for some experiment, hence offering a falsification test for a subset of them. Supposedly this might have already been done for counterfactuals, which would then be a very good reason to reject observer independent facts.

I like Carroll’s definition of observer, appropriate for something like MWI.
As John Bell inquired, "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?"
This does not seem to reference that definition, but more of the dictionary definition of observer.

Under the precept of the relativity principle any existing body is always in motion.
That sounds like an absolutist statement, which sort of violates PoR. PoR might be used to say that any body is in motion relative to certain frames. Without the frame reference, motion is undefined.

Would you agree that the inertial frame is just an ideal, and it does not actually represent anything real in the real world of physical, material bodies?
I’ve called it an abstraction, specifically an abstract assignment of coordinates to events. That’s true of any frame, inertial or not. So yes, an ideal as you call it.

there is no body in the universe which is not subjected to forces at every moment of passing time.
I’d have said ‘every moment of time’. I don’t see what the word ‘passing’ adds to that. That almost every body is subjected to nonzero net forces at any moment means that nothing exhibits inertial motion, but plenty of them exhibit good approximations of it to where the mathematics is very useful indeed.
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That sounds like an absolutist statement, which sort of violates PoR. PoR might be used to say that any body is in motion relative to certain frames. Without the frame reference, motion is undefined.

It is not an absolutist statement, it is a deductive conclusion derived from two premises, the PoR, along with an inductive conclusion derived from empirical observation. It is observed that as time passes, there are always things moving. Along with the PoR we can conclude deductively that any existing body is always in motion.

You are reversing logical priority here. The concept "frame of reference" is derived from the principle of relativity, not vise versa. So motion was defined first, as relative (PoR), and then the concept "frame of reference" was developed as the means for measurement. The PoR discusses the motions of bodies relative to each other, and there is no need for a concept of frame of reference in this discussion.

Only when the intent is to put numbers to the motion, measure it, is the reference frame needed, due to what the PoR assumes. So the PoR gives one of the basic rules for constructing the frame. Also, we need a rule concerning the conceptions of space and time to be employed in the measurement. Newton employed a fixed, static backdrop of space, from which a coordinate system could be applied, along with an "absolute" time. Time is absolute in the sense of constant and continuous. Einstein proposed an alternative conception of space and time.

As per above, the conceptions of space and time are essential aspects of the conception of frame of reference. Also, Einstein used substantially different conceptions of space and time, from Newton. Therefore we can conclude that the substantially different conceptions of space and time employed by Einstein result in a substantially different form of "frame of reference".

I’d have said ‘every moment of time’. I don’t see what the word ‘passing’ adds to that.

There's a big difference in conception of "time" here, which we can apprehend through analysis. Some would posit "the present moment" as a moment which clearly and concisely separates the past time from the future time. No time passes at "the moment" in this conception because it is a precise, non-dimensional, division, similar to the way that a non-dimensional point divides two line segments. The past, along with the future, provide a complete representation of time, and the moment is an arbitrary (yet substantialized, and justified by "the present)") point in time. The abstracted point, removed from the assumed real point at the present, may be projected anywhere in time, to produce specific durations, like specific line segments.

So when I said "every moment of passing time", I implied that within any "moment" there is inherently some duration of time. This denies the reality of the abstracted "point", implying that instead of being a non-dimensional point, like a point which divides one line into two line segments, it is an infinitesimal point, such that there is some time within that point. Now there is not a clear and precise division between the two time segments past and future, as some time passes within the present moment. And since "the moment" is the dividing point by which time is measured, the time which inheres within the moment under this conception, evades measurement. It escapes from being measured. The measured durations are the line segments, yet some time inheres within the points which provide the boundaries to a segment, so that the boundary is somewhat vague, and this time within the point ends up as an unknown relative to the segments produced when a line is divided.

The first conception of "the moment" discussed above, is consistent with the Newtonian conception. The passage of time is constant and continuous and such consistency provides the basis for the assumption that we can posit points of division anywhere, just like what was done with traditional spatial conceptions. The second conception of "the moment" is consistent with the one employed by Einstein. This is understood as "the relativity of simultaneity". The moment in time which marks "now", as the divisor between past and present is not a clear and precise, non-dimensional point. Each frame of reference is allowed to have an independent and separate point which divides the two line segments, past from future. Within the frame of reference, the point is still supposed to provide a clear and precise non-dimensional divisor, but the vague boundary occurs when different frames, the basis from which measurements are made, are related to each other.

Under the Newtonian proposal, there is supposed to be an absolute divisor, "the present", which is substantiated or justified by human experience. This grounds all measurements of time as being consistent with each other, based in the experienced "present". Einstein removes this, saying that "the present" is relative to the frame of reference, rather than the human experience of a division between past and future. As a result, we have no basic principle to resolve any discrepancies in measurement which manifest as the result of the positioning of the divisor, the point which measured time segments are relative to, as measurements are made as time passes at the present. Resolutions would be arbitrary.

Simply put, Einstein recognized that human experience cannot provide a clear and precise non-dimensional division between one time period and the next, and he exploited this fact to employ the principle that there is no precise division between future and past. Consequently the Einsteinian observation perspective is based in this assumption, and all observations recorded from this perspective will demonstrate this feature, as conclusions reflect premises.
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Both qualify as a computable number. The diagonalization method used...

The computable numbers are countable since they be put in a one-to-one correspondence with the natural numbers. However the real numbers are not countable per Cantor's diagonalization proof. Thus there are some real numbers that are not computable.

"So, if one accepts the authors' definitions for an observer and measurement, then one of the assumptions of free choice, locality, and observer-independent facts must be false."

That just sounds like Bell’s theorem (old news). What in 2019 was added to that?

The addition is that the experiment tests a Bell inequality for a Wigner's friend scenario (which the paper terms a Bell-Wigner test).

Specifically, there are two types of measurement that each Wigner (i.e., Alice and Bob) can perform. Alice can measure with her beam splitter removed (A0) or present (A1). Bob can similarly measure with his beam splitter removed (B0) or present (B1). When the beam splitter is removed, the Wigner measurement is the same as their friend's measurement. When the beam splitter is present, the Wigner measurement is in the {|+>,|->} basis.

So one of the A0 or A1 measurements and one of the B0 or B1 measurements are performed on each run of the experiment. Over multiple runs the measurements, on a classical explanation, must obey the CHSH inequality

$S = \langle A_1B_1 \rangle + \langle A_1B_0 \rangle + \langle A_0B_1 \rangle - \langle A_0B_0 \rangle \lt= 2$

where Ax and By are the values -1 or +1, and <AxBy> is the averaged product over multiple runs.

Per the experiment, and as predicted by quantum mechanics, the CHSH inequality is violated.

Sorry, but I don’t see what the AI adds that any simple device (like the circuit on the camera) doesn’t.

It would be a macroscopic-scale experiment where the AI friends would exhibit human-level intelligence. It would thus be comparable to a human Wigner's friend experiment.

I like Carroll’s definition of observer, appropriate for something like MWI.

'As John Bell inquired, "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?"'
— Andrew M

This does not seem to reference that definition, but more of the dictionary definition of observer.

Yes, which was part of Bell's point. It's well worth reading the full context of Bell's comment:

It would seem that the theory [quantum mechanics] is exclusively concerned about "results of measurement", and has nothing to say about anything else. What exactly qualifies some physical systems to play the role of "measurer"? Was the wavefunction of the world 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 better qualified system ... with a Ph.D.? If the theory is to apply to anything but highly idealized laboratory operations, are we not obliged to admit that more or less "measurement-like" processes are going on more or less all the time, more or less everywhere. Do we not have jumping then all the time?

The first charge against "measurement", in the fundamental axioms of quantum mechanics, is that it anchors the shifty split of the world into "system" and "apparatus". A second charge is that the word comes loaded with meaning from everyday life, meaning which is entirely inappropriate in the quantum context. When it is said that something is "measured" it is difficult not to think of the result as referring to some preexisting property of the object in question. This is to disregard Bohr's insistence that in quantum phenomena the apparatus as well as the system is essentially involved. If it were not so, how could we understand, for example, that "measurement" of a component of "angular momentum" ... in an arbitrarily chosen direction ... yields one of a discrete set of values? When one forgets the role of the apparatus, as the word "measurement" makes all too likely, one despairs of ordinary logic ... hence "quantum logic". When one remembers the role of the apparatus, ordinary logic is just fine.

In other contexts, physicists have been able to take words from ordinary language and use them as technical terms with no great harm done. Take for example the "strangeness", "charm", and "beauty" of elementary particle physics. No one is taken in by this "baby talk". ... Would that it were so with "measurement". But in fact the word has had such a damaging effect on the discussion, that I think it should now be banned altogether in quantum mechanics.
— John Bell, Against 'Measurement'

Ever seen the Andrei Linde interview on Closer To Truth? He talks explicitly about the role of the observer.

Yes, we've discussed Linde's comments a few times before. See John Bell's comment above, where he says:

When one remembers the role of the apparatus, ordinary logic is just fine. — John Bell, Against 'Measurement'

One could also say, "When one remembers the role of the observer, ordinary logic is just fine." Which is to say, there is logically no view from nowhere.

The key point for me, whether about observers or measurement apparatus, is that quantum mechanics predicts the result of the interaction between two systems (the observer and observed), not the pre-existing value of an isolated system (which Bell showed to be incoherent).
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Which is to say, there is logically no view from nowhere.

You’ve said that before, and even though I obviously agree, I don’t think it’s as obvious, nor as insignificant, as you make it seem. As you might know, one of Thomas Nagel’s books is called ‘The View from Nowhere’. His point is to critique the widespread understanding that science provides a ‘view from nowhere’, meaning a view that is uncontaminated by anything we deem ‘subjective’, the aim being to arrive at a view which is at once universal and objective. Whereas to me, the lesson of quantum mechanics is that we cannot obtain such a view when it comes to the purported ‘ultimate constituents’ of existence (which is where, after all, such ultimate objectivity should be sought, you would think). The fact that observation has an unavoidably subjective dimension is the very thing that Einstein strenuously objected to - ‘does the moon continue to exist when nobody’s looking at it?’, he asked. He strongly believed that there was a reality that existed just so, independently of any act of observation, and it was science’s job to discern that. Insofar as it had to make concessions to ‘the method of observation’, then quantum mechanics was, to him, obviously incomplete. Wasn’t that the gist of the Einstein-Bohr debates?
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You’ve said that before, and even though I obviously agree, I don’t think it’s as obvious, nor as insignificant, as you make it seem. As you might know, one of Thomas Nagel’s books is called ‘The View from Nowhere’. His point is to critique the widespread understanding that science provides a ‘view from nowhere’, meaning a view that is uncontaminated by anything we deem ‘subjective’, the aim being to arrive at a view which is at once universal and objective.

I don't think it's either obvious or insignificant. Nagel critiques "the view from nowhere" but he doesn't reject it. He instead proposes an additional subjective dimension (per the usual Cartesian subject-object dichotomy) that just entrenches the error.

The fact that observation has an unavoidably subjective dimension is the very thing that Einstein strenuously objected to - ‘does the moon continue to exist when nobody’s looking at it?’, he asked. He strongly believed that there was a reality that existed just so, independently of any act of observation, and it was science’s job to discern that. Insofar as it had to make concessions to ‘the method of observation’, then quantum mechanics was, to him, obviously incomplete. Wasn’t that the gist of the Einstein-Bohr debates?

Sure, but the debates have moved on. There have been subsequent discoveries that would have informed both their views, and have informed ours. For example, Bell's Theorem and decoherence, just to name two.

So there's no question that the moon is there when no-one's looking at it, not least because its effects are ever-present in the environment, such as in the ocean tides. Similarly, there's no question that dinosaurs once existed, even though no-one has ever observed them.
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I don't think it's either obvious or insignificant. Nagel critiques "the view from nowhere" but he doesn't reject it. He instead proposes an additional subjective dimension (per the usual Cartesian subject-object dichotomy) that just entrenches the error.

I don’t agree that Nagel’s diagnosis is erroneous. I think he pinpoints something real and insidious.

And Bell's Theorem did nothing to validate Einstein's realist objections to 'spooky action at a distance'. Bell himself had this to say:

The discomfort that I feel is associated with the fact that the observed perfect quantum correlations seem to demand something like the "genetic" hypothesis. For me, it is so reasonable to assume that the photons in those experiments carry with them programs, which have been correlated in advance, telling them how to behave. This is so rational that I think that when Einstein saw that, and the others refused to see it, he was the rational man. The other people, although history has justified them, were burying their heads in the sand. I feel that Einstein's intellectual superiority over Bohr, in this instance, was enormous; a vast gulf between the man who saw clearly what was needed, and the obscurantist. So for me, it is a pity that Einstein's idea doesn't work. The reasonable thing just doesn't work. — John Stewart Bell (1928-1990), quoted in Quantum Profiles, by Jeremy Bernstein (Princeton University Press, 1991, p. 84)
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I don’t agree that Nagel’s diagnosis is erroneous. I think he pinpoints something real and insidious.

Yes he does. I'm further saying that the view from nowhere should be rejected in its entirety, not supplemented by a further error (the Cartesian subject).

And Bell's Theorem did nothing to validate Einstein's realist objections to 'spooky action at a distance'.

Yes, Bell showed that Einstein's idea didn't work. It doesn't follow that the moon isn't there when no-one looks at it.
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It doesn't follow that the moon isn't there when no-one looks at it.

The moon (where 'moon' symbolises 'any object') does not exist outside your consciousness of it. However, neither does it not exist. The universe/world/moon/whatever is a featureless, undifferentiated and meaningless aggregation of matter-energy which is only differentiated into separate objects, with features and locations - which comes into being - in the mind of the observer.

Let’s begin with a thought-experiment: Imagine that all life has vanished from the universe, but everything else is undisturbed. Matter is scattered about in space in the same way as it is now, there is sunlight, there are stars, planets and galaxies—but all of it is unseen. There is no human or animal eye to cast a glance at objects, hence nothing is discerned, recognized or even noticed. Objects in the unobserved universe have no shape, color or individual appearance, because shape and appearance are created by minds. Nor do they have features, because features correspond to categories of animal sensation. This is the way the early universe was before the emergence of life—and the way the present universe is outside the view of any observer.
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The moon (where 'moon' symbolises 'any object') does not exist outside your consciousness of it. However, neither does it not exist. The universe/world/moon/whatever is a featureless, undifferentiated and meaningless aggregation of matter-energy which is only differentiated into separate objects, with features and locations - which comes into being - in the mind of the observer.

One counter to this is that there is differentiation even without consciousness. True that there would be no conscious beings to conceptualize the universe, or out it into words and write about it on a forum. However structure would exist in how some parts of that universe can interact with others. This is the crux of the position that a conscious being is not needed to collapse a wavefunction - any interaction can do it.
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True that there would be no conscious beings to conceptualize the universe, or out it into words and write about it on a forum.

‘There would be no objects with shape and appearance, because shape and appearance are created by minds’. But that is part of a larger argument. Context is important. From a naturalistic perspective of course it is true that objects exist independently of observation, but here we’re discussing the metaphysical issue suggested by ‘the observer problem’
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The universe/world/moon/whatever is a featureless, undifferentiated and meaningless aggregation of matter-energy which is only differentiated into separate objects, with features and locations - which comes into being - in the mind of the observer.

That's a more or less imaginable picture, but how do you know, how could you know, it captures the character of reality? How could we make sense of the idea that something utterly undifferentiated and featureless could give rise to the vast and complex universe we observe?
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But when inflation ends, the universe reheats into a hot plasma of matter and radiation. That actually does lead to decoherence and branching

That's informative and interesting. So once inflation ends, the multiverse begins, until De Sitter space, when there's nothing left to decohere and make observations. Then all is just superposition.

That sounds mostly reasonable, but the branching part based on something making observations still bothers me a bit. What is the branching mechanism? Perhaps I should have started with that question instead.
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How could we make sense of the idea that something utterly undifferentiated and featureless could give rise to the vast and complex universe we observe?

Isn't that what we're all doing here? What I mean is, isn’t this one of the fundamental questions of philosophy? This is an approach that I think credibly addresses that question.
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That sounds mostly reasonable

Pardon me for so saying, but you must have a very liberal definition of ‘reasonable’ ;-)
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So once inflation ends, the multiverse begins, until De Sitter space, when there's nothing left to decohere and make observations. Then all is just superposition.

Physicists have coined words and expressions as conveniences as they work through the math, and we in the lay community have adopted them as if they really mean something. "Superposition" gets way overused, and frequently in a kind of mystical fashion. "Curved space" is right up there, too.

Once these words and expressions get into common usage philosophers begin using them as they explore metaphysical realms. It's quite a game. :chin:
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Assuming that reality is non-dual I don't undertsand that to mean it is either one or many, which would entail that it is neither differentiated nor undifferentiated and that those dualistic categories do not apply.
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Reasonable as in making sense within the MWI interpretation. MWI needs to be self-consistent and not have to introduce anything from outside the wave-function to make things works. So as long as observers and observation can be understand as parts of the universal wave-function, it's reasonable. I still have questions, though.
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That would be an anti-realist interpretation. Sean Carol is a realist about the wave-function, so he thinks there literally is a multiverse, at least from after inflation until heat death of the universe.
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‘There would be no objects with shape and appearance, because shape and appearance are created by minds’. But that is part of a larger argument. Context is important. From a naturalistic perspective of course it is true that objects exist independently of observation, but here we’re discussing the metaphysical issue suggested by ‘the observer problem’

My reply was very much to do with the context being discussed here.

In the context of the role of observers in the MWI, and the role of observers in quantum mechanics generally, there is no requirement for that observer to be a mind or have consciousness, or to be able to distinguish shapes or colors. The observer simply needs to be able to interact - something rocks, gasses, and moons can do. In the context of this discussion, even if all life in the universe was extinguished, the parts of the universe will continue to interact with other parts, and the lack of consciousness will make little difference.

That at least is the counter position to your previous argument.
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The computable numbers are countable since they be put in a one-to-one correspondence with the natural numbers.
Not to disagree, but an assertion like that requires a demonstration that they’re countable.
However the real numbers are not countable per Cantor's diagonalization proof. Thus there are some real numbers that are not computable.
Interestingly, the real number generated by Cantor's diagonalization proof is a computable number, so I’m not sure if this counts as evidence that there are some real numbers not computable. Once again, not disagreeing with the conclusion, only with how it was reached.
That just sounds like Bell’s theorem (old news). What in 2019 was added to that?
— noAxioms
The addition is that the experiment tests a Bell inequality for a Wigner's friend scenario (which the paper terms a Bell-Wigner test).
OK, they managed to test something whose outcome (the CHSH inequality violation) was already predicted by quantum theory. It’s a new test, but not one that changed the theory or any of its interpretations in any way.
Thanks for the larger context Bell statement. I agree with it fully. What is ‘jumping’ in that quote? “Do we not have jumping then all the time?”.
Meanwhile, I still don’t see what the AI in the box will do. Bell’s statement is pretty clear that a real human in there wouldn’t serve any special role or purpose, so why would an AI be any different?

You are reversing logical priority here. The concept "frame of reference" is derived from the principle of relativity, not vise versa.
Not sure where you get this idea. PoR is defined in a few places
In physics, the principle of relativity is the requirement that the equations describing the laws of physics have the same form in all admissible frames of reference. — wiki
And from the special relativity paper itself:
They suggest rather that, as has already been shown to the first order of small quantities, the same laws of electrodynamics and optics will be valid for all frames of reference for which the equations of mechanics hold good. We will raise this conjecture (the purport of which will hereafter be called the “Principle of Relativity”) to the status of a postulate

1. The laws by which the states of physical systems undergo change are not
affected, whether these changes of state be referred to the one or the other of
two systems of co-ordinates in uniform translatory motion
— Einstein,1905
Each one of these definitions of the principle of relativity references ‘frames of reference’ or ‘systems of coordinates’. I would go so far as to say that the PoR is derived from frames of reference, but it certainly is defined using the concept. Thus the reference frame precedes the principle, else the definitions above would all be meaningless.
The definition of motion being relative to a reference makes no reference to the principle of relativity.

So when I said "every moment of passing time", I implied that within any "moment" there is inherently some duration of time.
That’s like asserting that a mathematical point or a location in space must have a size. Your choice I suppose. It seems to just complicate what is otherwise a simple thing.
Your presentist opinions are well known. They’re valid (there are alternatives to Einstein’s theories that deny both his SR premises), but they’re fringe alternatives. Your inability to demonstrate an understanding of the mainstream view seems baffling for somebody with in-depth interest in the subject.
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Sean Carol is a realist about the wave-function

In quantum physics, a wave function is a mathematical description of the quantum state of an isolated quantum system. The wave function is a complex-valued probability amplitude, and the probabilities for the possible results of measurements made on the system can be derived from it.
Wikipedia

I can't see how this (a wave function) could be construed to be a physical reality, but some do. Perhaps my short-comings. :roll:
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Perhaps my short-comings.

Not yours. Theirs. :rage:

The observer simply needs to be able to interact - something rocks, gasses, and moons can do. In the context of this discussion, even if all life in the universe was extinguished, the parts of the universe will continue to interact with other parts, and the lack of consciousness will make little difference.

You do notice the "realist" assumption lying behind this, when that is precisely what is at issue. In other words, it begs the question.
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You do notice the "realist" assumption lying behind this, when that is precisely what is at issue. In other words, it begs the question.

Absolutely, I made assumptions. But it no more begs the question than an idealist position or any other position on this issue, including the one you were arguing for.

However I want to add something. Realism in quantum mechanics does not always mean the same thing as in philosophy. We know almost for certain that local realism is not true. What is meant by realism here? It refers to there existing objects with certain defined properties separate to interacting with them - this does not seem to be true. But it is not at all clear that interaction requires consciousness, however too often I see people making that jump as if it were required and necessary based on quantum mechanics.
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But the realist attitude begs the question, insofar as the question is ‘does the object exist in the absence of any observer’? Whereas, the existence of objects for the observer is not in question. As idealist philosophers, such as Bernardo Kastrup, will argue, the fact of the experience of an objective domain is never at issue. What is at issue is the question as to whether that domain is really mind-independent. As Descartes said, we can doubt the veracity of any experience, but we can’t doubt that we are subjects of experience. And we can say that without begging any question whatever.

As far as local realism is concerned, that issue arises from the theoretical postulate of entanglement and its subsequent experimental validation, doesn’t it? Of course, much ink has been spilled on the implications of that, but I think it can be safely stated that it appears to violate the realist assumption that the world comprises objects separated by distance in space. We already discussed the QBist interpretation above, which others here don’t favour. But I want to try and home in on what, exactly, is at issue. The necessity of acknowledging the existence of the observer, who is outside the equation, so to speak, is telling us something about the nature of reality. And what it is telling us, is not necessarily something amenable to scientific analysis. I myself am accustomed to the ‘constructivist’ approach - that the reality which we naively take for granted as simply something given, something external and separate from us, is in some fundamental sense constructed by the mind - your mind, my mind.

From a naturalistic point of view, this is not considered - naturalism tends to assume the ‘reality of appearance’ so to speak. And as the mind is something that cannot be made subject to objective analysis, in that it’s not an object of perception, then its sits uneasily with the naturalist or objectivist framework. But that is what physics has called into question. Some interpretations can deal with that but others cannot. That is why I think there *is* a ‘many-worlds’ interpretation - specifically to avoid acknowledging the fact that reality itself, being itself, has a fundamentally subjective pole, which is intrinsic to it, but which is never disclosed directly through objective analysis. That’s the point at issue, as I see it.
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Not sure where you get this idea. PoR is defined in a few places
In physics, the principle of relativity is the requirement that the equations describing the laws of physics have the same form in all admissible frames of reference.

Try this:

Galileo formulated the principle of relativity in order to show that one cannot determine whether the earth revolves about the sun or the sun revolves about the earth. The principle of relativity states that there is no physical way to differentiate between a body moving at a constant speed and an immobile body. It is of course possible to determine that one body is moving relative to the other, but it is impossible to determine which of them is moving and which is immobile. — https://www.tau.ac.il/education/muse/museum/galileo/principle_relativity.html#:~:text=The%20principle%20of%20relativity%20states,moving%20and%20which%20is%20immobile.

Sorry noAxioms, but we're just too far apart in terminology to carry on any meaningful discussion. I spend all my time just having to show you that you don't know what you're talking about. First we spent forever on the meaning of "inertial frame", now we're stuck on the meaning of "the principle of relativity". It's pointless, we can't discuss anything significant.
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ut the realist attitude begs the question, insofar as the question is ‘does the object exist in the absence of any observer’? Whereas, the existence of objects for the observer is not in question. As idealist philosophers, such as Bernardo Kastrup, will argue, the fact of the experience of an objective domain is never at issue. What is at issue is the question as to whether that domain is really mind-independent. As Descartes said, we can doubt the veracity of any experience, but we can’t doubt that we are subjects of experience. And we can say that without begging any question whatever.

You are quite right that the existence of objects for the observer is not in question. But the original post I replied to a few days ago was going beyond that. It was suggesting that the objects do not exist if the observer is not observing. That is begging the question in that it is assuming that realism is wrong.

So saying that objects do not exist when you do not look at them, is begging the question just as much as saying that objects do exist when you do not look at them.
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The necessity of acknowledging the existence of the observer, who is outside the equation, so to speak, is telling us something about the nature of reality.
Yes
And what it is telling us, is not necessarily something amenable to scientific analysis.
I am undecided on this. What it is telling me is that it is a fiendishly complicated issue at hand and I am not sure I have the correct tools to interrogate the problem. There are suggestions on how this may be interrogate using science, with quantum computers for example - I believe there is a post in this thread about the very thing. However I have not yet been able to wrap my head around this proposed experiment.

I myself am accustomed to the ‘constructivist’ approach - that the reality which we naively take for granted as simply something given, something external and separate from us, is in some fundamental sense constructed by the mind - your mind, my mind.

I am not of this approach, partly because every time I explore it I find that the logical end to this approach is solipsism. The way i interact with you is no different to the way I interact with other physical objects. Thus without some form of realism, I have no reason to believe that the photons leaving my laptop screen in your posts, have anything to do with another consciousness. If I question whether the photons are real, then I should question whether wayfarer is real in the same way. It is only my consciousness that I inhabit differently, and so the natural conclusion down this path would be that I only exist. But I reject this. Perhaps this is a discussion for a different thread though.
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Perhaps, just a wild guess, (the) mathematics (of quantum physics) is infected by (the) philosophy (of consciousness). :chin:
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And what it is telling us, is not necessarily something amenable to scientific analysis.
— Wayfarer
I am undecided on this. What it is telling me is that it is a fiendishly complicated issue at hand

It's not that it's complicated, but that scientific analysis generally takes place on a different level - that of the scientific analysis of objects, forces and energy. The question of the role of the observer is not complicated in that sense, but it's also not an objective question. That's why it evades scientific analysis - not that it's complicated or remote, but that it's 'too near for us to grasp'.

The way i interact with you is no different to the way I interact with other physical objects.

When you interact with others on the forum, you are not interacting with physical objects, but with subjects and their ideas. It is vastly different to how you interact with physical objects.

So saying that objects do not exist when you do not look at them, is begging the question just as much as saying that objects do exist when you do not look at them.

The way I put it is that both existence and non-existence are mind-dependent. It's not as if the object literally ceases to exist apart from the mind, but that the sense in which it exists is inherently meaningless. I know it's a very tricky point to grasp. From the interview with Chris Fuchs about QBism:

It’s so ingrained in us to think about the world without thinking of ourselves in it. It reminds me of Einstein questioning space and time — these features of the world that seemed so absolute that no one even thought to question them.

It’s said that in earlier civilizations, people didn’t quite know how to distinguish between objective and subjective. But once the idea of separating the two gained a toehold, we were told that we have to do this, and that science is about the objective. And now that it’s done, it’s hard to turn back. I think the biggest fear people have of QBism is precisely this: that it’s anthropocentric. The feeling is, we got over that with Copernicus, and this has got to be a step backwards. But I think if we really want a universe that’s rife with possibility with no ultimate limits on it, this is exactly where you’ve got to go.

How does QBism get you around those limits?

One way to look at it is that the laws of physics aren’t about the stuff “out there.” Rather, they are our best expressions, our most inclusive statements, of what our own limitations are. When we say the speed of light is the ultimate speed limit, we’re saying that we can’t go beyond the speed of light. But just as our brains have gotten bigger through Darwinian evolution, one can imagine that eventually we’ll have evolved to a stage where we can take advantage of things that we can’t now. We might call those things “changes in the laws of physics.” Usually we think of the universe as this rigid thing that can’t be changed. Instead, methodologically we should assume just the opposite: that the universe is before us so that we can shape it, that it can be changed, and that it will push back on us. We’ll understand our limits by noticing how much it pushes back on us.
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