the Atemporal Universe - Resolving the Problem of Time

Just wondering if you guys have had a chance to take a look at The Light Clock Toaster "Paradox" thread? I updated it with a post that is pertinent to the notion of the Roundtrip Light Principle.

Fourier wrote: »

You can prove QFT is local. Proofs are in the texts of Rudolf Haag and Weinberg. So to say it is nonlocal is provably wrong. It was a historical problem, people wondered if that made QFT nonlocal. The roundtable later mentions it is not a problem.

Gisin just says "can relativity account for nonlocal correlations?" as a question. In his own papers he says "yes". What you're doing is taking aspects of books and papers out of context about topics you don't know.

Apologies, I must have missed both of those (probably due to not fully understanding the points). Would you be able to highlight where those points are made?

Fourier wrote: »

The rest of the quotes concern quantum gravity which we know has problems, but is unrelated to what I was discussing.

The quotes pertain to issues with QFT being applied on a cosmological level and the "blame" is quite squarely laid at the feet of SR. Do you believe that there is no way to arrive at Minkowski spacetime in such a way that does not incorporate RoS?

Fourier wrote: »

I never said that was all it does. That's its end goal.

You were quite clear in your statement and indeed you were correct. That is what science is supposed to do - it is the "end goal" as you say. As is abundantly clear from your outline, relativity doesn't follow that.

Fourier wrote: »

Point 3 is exactly that. You have to actually read what we are saying. You can't isolate fragments of our posts in an attempt to construct gotchas.

I'm not playing gotcha. I'm simply outlining the consequences of your statements.

Re-read your statement about "what science does". The encoding of empirical statements comes first:
"physics is about making empirical conclusions via mathematical deduction by encoding empirical statements as mathematical facts"

We can simply re-arrange that sentence without changing its meaning: by encoding empirical statements as mathematical facts, physics is about making empirical conclusions via mathematical deduction"

As you outlined, the conclusion of RoS is not arrived at by encoding empirical statements as mathematical fact and then making logical deductions. It is arrived at by encoding assumptions as mathematical fact and then making logical deductions.

The emprical observations in (3) aren't the empirical statements that are encoded as mathematical facts, which are then used to make logical conclusions. They are the logical conclusions - or some of them at least - they are the logical conclusions which are subjected to empirical verification. They are the logical conclusions which are "empirically accessible". The fact that the other conclusions aren't emprically accessible makes them untestable.

As mentioned, the verification of those empirically accessible conclusions could be taken as verification of the non-accessible conclusions if it weren't for the simple fact that they equally support mutually exclusive conclusions.

Fourier wrote: »

All physical theories have such elements. There will always be a layer between ontological statements and empirically accessible facts.
The point is that Einstein doesn't assume RoS, not that RoS is empirically verifiable directly.

I understand that that is the point you are arguing against, but that isn't the point that is being contended. Although, whether or not Einstein assumes RoS is highly debatable. See the thesis of the conventionality of simultaneity referenced above. And, to quote Daniel Kahnemann again:

The errors of a theory are rarely found in what it asserts explicitly; they hide in what it ignores or tacitly assumes

So, while Einstein may not explicitly assume RoS, it can certainly be contended that he tacitly assumes it - again, see the conventionality of simultaneity thesis. There are further tacit assumptions pertaining to the measurment of "time" by clocks.

BUT!! That again, is not the contention.

The contention is that, to conclude that a model of the physical world, which incorporates RoS, is an accurate model, requires the conclusion of RoS to be assumed. In this context, the empirical accessibility of RoS is indeed pertinent.

That a principled approach to developing physical theories can be adopted is not in question. The issue is when it can be demonstrated that the conclusions [of one particular interpretation which follows such an approach] must be assumed.

Arguably, all 3 of the defining characteristics/conclusions of SR (i.e. what distinguishes it from an alternative which doesn't incorporate RoS), hinge on RoS. This means that all of it's defining conclusions must be assumed.

Fourier wrote: »

Poincaré's derivation cannot be gotten to work with QFT. The particle spectrum would be different. There are additional elements to why physicists don't accept Poincaré's derivation.

I might not have been totally clear in what I was saying. I wasn't saying that Poincaré's formulation of the theory can be made to work with QFT, I was saying that his derivation of the mathematics demonstrates that the mathematics of Minkowski doesn't necessarily imply RoS. It suggests (if not demonstrates) that Minkowski spacetime can be interpreted in such a way that doesn't include RoS.

Obviously I amn't capable of demonstrating this, so I would ask you genuinely: do you not think that by encoding the empirical statement of a round-trip light principle as mathematical fact, the mathematics of Minkowski spacetime couldn't be arrived at?

I struggle to see how they couldn't. As I've suggested, removing the "scaffolding" of the absolute reference frame [from Poincaré's derivation] would leave us with the mathematics of Minkowski. Or, applying a round-trip light principle instead of a one-way light principle in Einstein's theory.

Fourier wrote: »

You'd have to understand QM to comprehend it. Gisin discusses it in his text "Quantum Chance: Nonlocality, Teleportation and Other Quantum Marvels".

What's was it that Feynman said about understanding Quantum Mechanics again?
I don't doubt I will need to do a lot of reading and asking questions in order to develop a clearer understanding but if you could highllight a section of the text where Gisin makes the statement I can make a start. I have a copy of Quantum Chance. Or even give a brief outline of what Gisin says I will be able to ask others, more knowledgable than myself, to evaluate the statements.

I've re-read the roundtable conclusions and to reply to your previous post again:

Fourier wrote: »

You can prove QFT is local. Proofs are in the texts of Rudolf Haag and Weinberg. So to say it is nonlocal is provably wrong. It was a historical problem, people wondered if that made QFT nonlocal. The roundtable later mentions it is not a problem.

I don't think this quote:

Problem of localization in a quantum field theory. Schroedinger’s equation evolves wave- functions in a non-local way, so there seems to be a problem with superluminal propagation.

is saying that QFT is non-local, it's saying that Schroedingers wave equation evolves wave-functions in a non-local way. It is this that gives rise to an issue of superluminal propagation. This appears to be what Smolin refers to when he talks about the desire to go "deeper". The suggestion by [not just] him is that QM does contradict the local realism of SR just not a way that involves signal propagation i.e. causality.

Fourier wrote: »

The rest of the quotes concern quantum gravity which we know has problems, but is unrelated to what I was discussing.

This is a bit of a misnomer. Just bcos the [fairly explicit] points are made in the context of Quntum Gravity, it doesn't mean that inferences cannot be made as to their pertinence to SR. Indeed, the statements themselves are quite unequivocal.

Quantum mechanics has one thing, time, which is absolute. But general relativity tells us that space and time are both dynamical so there is a big contradiction there. So the question is, can quantum gravity be formulated in a context where quantum mechanics still has absolute time? Or does time have to give. The answer, yes or no, is interesting. If the answer is no, then perhaps some experiment can probe whether or not time is absolute?

This is very explicit in its statement about the nature of time in QM and the nature of time in GR. But, just bcos the statements are made in the context of QG, it doesn't mean that they don't apply to SR - bcos they clearly do. QFT doesn't resolve this bcos the absolute vs relative time issue applies equally to SR.

Fourier wrote: »

I don't see that in the quotes. Smolin for instance discusses what a certain class of hidden variable theory would have to do to explain entanglement. This has nothing to do with what you are saying. As I said the quotes relate to the more difficult end of a subject you don't know. It's pointless to take them out of context.

If you can't see it, I'll try to highlight what I'm seeing.

Smolin is less explicit in his ciriticisms of Einstein's relativity. He doesn't refer to it as "the root of all evil" as Magueijo does. Instead he chooses to say

This is our choice. Either quantum mechanics is the final theory and there is no penetrating its statistical veil to reach a deeper level of description, or Aristotle was right and there is a preferred version of motion and rest.

So, he suggests that either QM (not QFT) is the final theory or absolute motion and rest are real. He idicates that both roads lead to

giving up the relativity of simultaneity and embracing its opposite: that there is a preferred global notion of time

Presumably bcos, if QM is the final theory it is based on abolute time while if it isn't the final theory - and a hidden variables theory is more fundamental - it necessitates a preferred reference frame. It would appear that Smolin believes that all roads lead to the ditching of RoS.

He goes on to say

Remarkably, this does not require overthrowing relativity theory; it turns out that a reformulation of it is enough. The heart of the resolution is a new and deeper way of understanding general relativity theory which reveals a new conception of real time.

In other words, reformulating GR by overthrowing SR.

The quote can be seen in full again [in the previous post] here.



João Magueijo is a bit more explicit in Faster than the Speed of Light

The root of all the evil was clearly special relativity. All these paradoxes resulted from well-known effects such as length contraction, time dilation, or E=mc2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects. Quantum gravity seemed to lack a dam—its effects wanted to spill out all over the place; and the underlying reason was none other than special relativity.

So, while QFT might be taken to represent a feather in the cap of SR, it would appear that what it gives with the one hand, it takes away with the other. According to Smolin and Magueijo at least.

Fourier wrote: »

He doesn't. I don't have to see a text, I've worked through his derivation before and that of other physicists in textbooks.

Again, to paraphrase Kahneman, the issue doesn't lie in the explicit assumptions of the theory, it lies in the tacit assumptions. The conventionality thesis i.e. the thesis that RoS is established by convention speaks to the idea that RoS is a tacit assumption.

Fourier wrote: »

I know it's not your original contention but it is something you claimed a few times. We can't move forward until we have an accurate view of what Einstein actually did.

Whie the issues are related - by virtue of the fact that they pertain to SR - neither issue is dependent on the other. I'm clear on what Einstain explicitly assumed and you have been clear on the fact that he encodes assumptions as mathematical facts and then derives conclusions from that. You have been clear that some of those conclusions (RoS among them) are not empirically accessible. This means that they can only be established by convention, as they cannot be tested empirically. Therefore, RoS must be established by convention i.e. it is tacitly assumed.

Fourier wrote: »

Not in a way that is compatible with modern particle physics. That's my problem with it. A round trip light principle won't give the same particle spectrum. It's easy enough to prove as the group representations carried by the particles are different. The resulting particle spectrum is empirically incorrect.

Just to refer again to the Light Clock Toaster Paradox thread, as it is pertinent here.

With the light clock thought experiment, where the light clock is oriented from carriage-end to carriage-end, the observer at rest on the platform will see time speed up and then slow down. I haven't seen a resolution of this yet that doesn't invoke a round-trip light principle. Would yuo have any thoughts on that?


We can apply some reasoning to the above question of whether a round-trip light principle would be compatible with modern particle physics. You have mentioned that the issue has to do with the symmetry of the real space-time and this is one of the reasons why the Poincare inerpretation doesn't work. [Going the Einsteinian route as opposed to the LP rout] The application of a round-trip light principle would leave us with the mathematics of Minkowski but without the absolute space and time that Poincare invoked.

Given the same mathematics, without the issues of the symmetry of an absolute spacetime, a round-trip principled theory should be empricialy equivalent to SR.

If we derive our information about the physical properties of spacetime e.g. its symmetry from the mathematics and given that the mathematics of Minkowski can be arrived at in such a way that it doesn't inlcude RoS, it would seem to imply that the physical properties of spacetime that impact modern particle physics needen't include RoS.

Fourier wrote: »

It doesn't since it obeys the no signalling constraint. There's no nonlocal propagation in QFT. This can be directly proved from the Wightman axioms.

So are those from the Perimeter Roundtable mistaken when they say:

Schroedinger’s equation evolves wave- functions in a non-local way

Fourier wrote: »

I'm not sure what their pertinence to SR is I have to say.

I'll try and outline where I see the pertinence then and you can continue to highlight where my misunderstanding lies:

Quantum mechanics has one thing, time, which is absolute. But general relativity tells us that space and time are both dynamical so there is a big contradiction there. So the question is, can quantum gravity be formulated in a context where quantum mechanics still has absolute time? Or does time have to give. The answer, yes or no, is interesting. If the answer is no, then perhaps some experiment can probe whether or not time is absolute?

Here it is saying that QM has "time which is abssolute". They question whether QG can be formulated in a context where QM still has "absolute time". It's pertinence to SR is that like GR, SR "tells us that space and time are both dynamical so there is a big contradiction there".

If QFT resolved this issue, as you appear to be suggesting, then there wouldn't be a need to raise it. Unless you are stating that those from the Perimeter Roundtable are mistaken.

giving up the relativity of simultaneity and embracing its opposite: that there is a preferred global notion of time

Should be self-explanatory.

The root of all the evil was clearly special relativity. All these paradoxes resulted from well-known effects such as length contraction, time dilation, or E=mc2, all basic predictions of special relativity. And all denied the possibility of establishing a well-defined border, common to all observers, capable of containing new quantum gravitational effects. Quantum gravity seemed to lack a dam—its effects wanted to spill out all over the place; and the underlying reason was none other than special relativity.

Should be self-explanatory.

Fourier wrote: »

Look genuinely you don't know this area at all. That's not what Smolin is saying. He's talking about Hidden variables and Bell's theorem. Bell's theorem has several ways out of it of which removing RoS in just one. The choice is not between QM being the final theory and RoS being wrong their four other options as well. Earlier in the book he gives his reasons as to why he doesn't believe in the other options. However the entire argument does not work as you think, since you don't really know the area. I just don't understand why you'd run around taking quotes out of context about topics you haven't learned.

It is worth noting that the fact that removing RoS is even an option further demonstrates the point that it is an assumed conculusion. If it were supported by empirical observation - as the slowing of clocks in the Hafele-Keating experiment for example - then it wouldn't be "on the table".

I had a quick glance back over what I thought would be the relevant chapters but didn't see a very detailed discussion of the alternatives. He mentions LCQ, String Theory, and the MWI. Are those 3 of the 4 alternative you were referring to?

He does talk about the limitations of the standard model

After working with the Standard Model for several decades, we are now simultaneously more confident that it’s correct within the limited domain in which it has been tested and less confident of its extendability outside that domain.

Fourier wrote: »

QM doesn't have absolute time. Literally, several predictions of QM and QFT use the fact that time is not absolute like the Unruh effect.

Again, are the alumni from the Perimeter Roundtable incorrect in their explicit statement that QM has "time which is absolute"?

Some of the issues with QFT have been outlined in the quotes above, where the "blame" is directly attributed to SR. But, just bcos QFT includes RoS, it doesn't mean that QFT doesn't also assume the conclusion or establish it by convention. Indeed, it must do so, given that RoS isn't an empirically accessible conclusion.

I believe that is what you hope to demonstrate below.

Fourier wrote: »

They have to. The particle spectrum will be affected. Let me demonstrate it to you. In your model what is the actual structure of space and time?

Pertinent to this question is the issue raised in the Light Clock Toaster "Paradox" thread. I'll restate it again here:

In the light clock thought experiment where the light-clock is oriented from carriage-end to carriage-end, the observer in the "stationary system" will see time speed up and then slowdown, or speed up and slowdown in the same clock with 2 photons traveling in opposite directions.

Is there a resolution to this that doesn't make recourse to a round-trip light principle?

Fourier wrote: »

No they are correct. However the wave function isn't a physical object so it propagating nonlocally isn't some kind of problem. This is why you have to know QM to evaluate what they are saying.

A question that strikes me is, how could something non-physical be said to, in any way, have a problem associated with propagation, not to mention superluminal propagation?

I see what you're saying, and you're saying "it isn't some kind of problem", but the roundtable clearly says "Problem of localization .... a problem with superluminal propagation". You don't need to know QM to evaluate that they clearly see "some kind of problem" there.

As to the nature of the "problem", again, one doesn't need to know QM to understand that the roundtable sees it as a "problem of localisation" and a "problem with superluminal propagation".

Working on the assumption that those at the roundtable know QM, then presumably knowing QM won't lead to an evaluation that changes the "problem of localisation" and the "problem with superluminal propagation" into an understanding that they are "not some kind of problem".

Fourier wrote: »

Yes. It was a roundtable discussion by alumni so I don't know who said it. They easily might have worked in another area and not known QFT well enough. QFT literally doesn't have absolute time. First volume of Weinberg deals with this.

They don't say that QFT has absolute time, they say that QM does.

Perhaps they are refferring to something similar to this:

the t in ordinary classical mechanics refers to a clock carried by an inertial observer, which is not part of the dynamical system being modeled.
...
In quantum mechanics the situation is rather similar. There is a t in the quantum state and the Schroedinger equation, but it is time as measured by an external clock, which is not part of the system being modeled.

Smolin & Kauffman A Possible Solution For The Problem Of Time In Quantum Cosmology

Does the Schrödinger equation form any part of QFT?

Here is a list of the participants of the conference. I'm not sure how exactly the roundtable was conducted, but I doubt that everyone on that list was an actiive participant (based solely on the number of people). Perhaps some people were active while others were passive.

Would it be safe to assume that there was at least one person in attendance who had worked with QFT, or are we to assume that they are running around taking points out of context on subjects they've never learned?

Fourier wrote: »

I was taught by Magueijo, did a small project with him and have spoken to him several times. His views are not as you are thinking of them, you have to know QM to understand his points.

Nice, he seems like an interesting character. Does he still advocate a variable speed of light theory? Feel free to reference your private conversations with him to highlight where I'm misinterpreting what he says in the book. To be clear, I'm suggesting that he ascribes some (if not most) of the issues [of merging QFT with GR] to Special Relativity.

Fourier wrote: »

Again you don't know the theory of Hidden Variables in QM. It's not on the table in the way you think. It requires even the mathematics agreed upon by different views of relativity, e.g. Poincaré's & Einstein's to be wrong. Again as I said you don't know the area.

That's fair enough. And that does represent a pretty big barrier.

From what I can understand though, Smolin advocates for a notion of time that is contradictory to RoS. This arises from his position as a realist, which I would be incllined to take myself. As he says, "there must be something going on in each individual experiment". I would be further inclined to think that a final theory should not include RoS for the reasons allready espoused in this thread.

Fourier wrote: »

Nothing matters to this except the actual structure of space and time in your model. I'm not going to get into another discussion given how difficult this one is.

Talking about the roundtrip speed of light in a light clock, in an existing theory that incorporates Minkowski spacetime, is, I would have thought, relevant to a discussion about the structure of spacetime that employs a roundtrip light principle.

Anyway, I'm sure it can be addressed once this question is resolved.


Firstly, I wouldn't go so far as to call it a model. I don't have a particular model in mind as that is way above my capabilities. I'm conjecturing that a theory based on a round-trip light principle will derive the same mathematics as Minkowski spacetime and therefore wil have a Minkowskian structure - if our information about the structure of spacetime is derived from the mathematics.

But I've already stated all this. You've replied with questions about the symmetry of the spacetime, to which I have reiterated the point.

Fourier wrote: »

They're talking about getting one particular type of hidden variable theory to work. QFT itself has no problem with locality.

I take what you are saying but the fact that these scientists are even considering it, shows that it is not simply a closed matter.

My understanding is that there is no problem with locality if we don't go beyond the statistical predictions i.e. if we don't attempt to explain what happens in individual experiments. As Smolin states though, there is something going on in those individual epxeriments. Any theory that doesn't explain this is, by definition, an incomplete theory. It might be that given the limitations of experiments we cannot formulate a scientific theory that accounts for this, but that just represents a limitation on our ability.

Fourier wrote: »

QM is just a non-relativistic approximation to QFT which has no absolute time. So this is no issue.

Again, I take your point, but those at the perimeter roundtable clearly do see some kind of issue with it. If they didn't, they wouldn't have stated it so categorically; juxtaposing "time which is absolute" in QM with "relative and dynamical" time in GR. If QFT resolved all of this, then it wouldn't be a point of consideration.

Fourier wrote: »

Yes.

and those at the perimeter roundtable see an issue with Schrödinger's equation evolving wave functions in a non-local way, which appears to give rise to a problem of superluminal propagation.

You are suggesting that this isn't an issue, but if it was a completely resolved issue, then I'm sure those scientists wouldn't have seen the need to raise it. Unless they are going around making statements about subjects that they haven't learned.

Could it be the case that there are different interpretations of QM?

Fourier wrote: »

He considers a particular hidden variable approach to Quantum Gravity to require violating Relativity.

The quote above references the attempts to unify QFT with GR. The issue of inifinities that is mentioned in the guardian article and is the subjject of this statement:

it is meaningless to try to unify QFT so heavily suffering of infinities with GR. We also highlight difficulties of the QFT-treatment of entanglement.

Andrei Khrennikov (2016) The Present Situation in Quantum Theory and its Merging with General Relativity.

Does this pertain to the issue of renormalisation?

Either way, it's these issues which lead him to refer to SR as "the root of all evil" and which neccesitate his considering a hidden variables approach which violates relativity, in the first place. If SR weren't an issue, then there would be no reason to consider an apporach which violates it.

Fourier wrote: »

There are other realist approaches to going beyond QM, giving up Relativity isn't the only option. Personally I think realist approaches are unlikely to work.

which approaches are those? Do they include MWI and String Theory?

It might be my personal philosophical leanings but if a realist approach is one which says that there is something happening in the individual experiments of QM and there ought to be an explanation of this, then I can't see how anything other than a realist approach can be considered a complete theory.

Fourier wrote: »

I know that you've reiterated but you still don't understand why this doesn't matter. It doesn't matter if you can rederive Minkowski spacetime, the particle spectrum will change. Quantum Particles are sensitive to RoS being true.

If you have the same mathematical machinery shouldn't you have the same predictions?

Of course, for quantum particles to bee sensitive to RoS it would require Minkowski spacetime to be a physical structure. The problem with such a 4 dimensional structure is one that has been discussed at length on here, and in the essay I posted.

Such a 4 dimensional structure precludes the possibility of relative motion. I would go so far as to say that it predicts a frozen universe with no relative motion.

Fourier wrote: »

Nothing is ever a "closed matter" you can always consider rejecting things.


There's no problem with locality even if you want to go beyond the statistical predictions. There are other ways to go beyond the statistical predictions. Breaking locality is just one.

I suppose my position might indicate that I would have to advocate for breaking locality - although I cannot say that definitively.

Fourier wrote: »

It's a statement about the problem of background dependence in Quantum Gravity. In QFT time isn't absolute end of, but it is background dependent. They don't mean "absolute time" in the way you think. That's the problem with reading an extract out of context from experts in a field you don't understand. I don't really understand why you'd base your learning around out of context quotes instead of picking up a textbook.

I've come across the issue of background dependence vs indepdence in the book the Problem of Time. I must go back to that and see if I can take more from it.

The quote from the perimeter roundtable isn't the sole basis for my idea of QM having "time which is absolute", it was just the most explicit expression of a fairly common statement pertaining to QM. I will indeed continue to try and delve more into it and I'll check out your recommendations for text books.

Fourier wrote: »

Yes that's the point. If you interpret the Schrodinger equation as describing the propagation of a real wave, as they do in their hidden variable model, then you'd have to consider there to be nonlocal propagation. However in the standard Copenhagen reading of QM the wavefunction isn't real and operationally QFT is local so there is no issue.

Essentially this appears to boil down to the question of realism vs anti-realism then?

Fourier wrote: »

I've said this already and repeated it above. Hidden variable theories don't necessitate violating relativity. That's just one type of hidden variable theory.

I guess my position would suggest that I would advocate for such a theory that does violate relativity, or as Smolin puts it, "reinterprets" relativity.

Fourier wrote: »

MWI yes. String Theory is just a type of quantum theory, it doesn't go beyond it.

I, personally, wouldn't be inclined to call MWI a realist theory.

Fourier wrote: »

Most scientists consider the evidence to be strongly against realist approaches. We have several theorems rendering them almost impossible or contrived to the point of being unrealistic. It's why I have little interest in what Smolin is doing. We already know what kind of issues it will have. Like most experts in quantum theory I think realist accounts are not going to work. Yes it means QM is incomplete, but the completion isn't possible. The ontology of the microscopic world does not seem to have a mathematical description.

I would be of the position that fundamental reality is beyond description, but our inability to describe it doesn't mean that there isn't a fundamental reality. Again, as Smolin says, something is going on in those individual experiments. If we cannot describe that mathematically or linguisiticallly, then that is our failing and perhaps a "conspiracy" of nature.

Again, however, just because we cannot go beyond the statistical level mathematically, it does not mean we cannot derive anything beyond it on the basis of reasoning.

Which hidden variables thories are there that don't violate relativity?

Fourier wrote: »

You only have the same effective kinematic relations.

We seem to be going around on this point bcos I don't fully get yours.

If you have the same mathematics, how do you not have the same predictions? Just as the Lorentz-Poincaré interpretation of relativity makes the same predictions as the Einsteinian, but in this case the issue of symmetries of Galilean space should negated as we only have the mathematics of Minkowksi and it's symmetries [presumably].

Fourier wrote: »

Well they are sensitive to it, that's a mathematical fact. Minkowski spacetime doesn't preclude relative motion, read a textbook like D'Inverno to see this.

I'll check out that textbook. Is there a specific section which addresses this question? I've heard people refer to the angle between worldlines in a spacetime diagram but this doesn't actually address the issue, but the textbook might make reference to something else.

I would say however that any 4 dimensional structure where objects exist as worldlines/worldtubes frozen in that structure precludes relative motion. They simply cannot give rise to relative motion.

It's this idea that lead to Hermann Weyl's statement in Philosophy of Mathematics and Natural Science (Princeton University Press, Princeton, 1949)

The objective world simply is, it does not happen. Only to the gaze of my consciousness, crawling upward along the life line of my body, does a section of this world come to life as a fleeting image in space which continuously changes in time.

A position endorsed by Morbert in an old thread on the topic.

Fourier wrote: »

When discussing views on QM the phrase "Realism" just refers to the fundamental reality being described mathematically. It doesn't refer to whether there is a fundamental reality. Everybody in QM thinks there is a fundamental reality.

But would they question the idea that a theory can acually describe that fundamental reality?

Fourier wrote: »

Superdeterministic and non-causal ones.

Thanks.

Fourier wrote: »

The same no-go theorems prevent being able to reason about it beyond certain vague hints. So you won't be able to understand it by reason either beyond very small hints.

No, I meant just what you were referring to above with regard to there being a fundamental reality i.e. that there must be something beyond the statistical that is to be explained.

Fourier wrote: »

You get the same kinematics, but not the same ontology. The particles depend on the ontology in this case. To go into more detail would require teaching you QFT, I can't realistic do that.

Fair enough.

I still struggle to see how the same mathematics can give a different ontology. It can't be something inherent in the mathematics, it must be something added to the mathematics.

Fourier wrote: »

I don't see how. The world can be frozen from a 4D point and have relative motion from a 3+1D point of view.

That begs the qustion as to how?

If objects exist as worldlines frozen in a 4D structure where does the relative motion come from? How do frozen 4D worldlines manifest as 3D motion?

Fourier wrote: »

Because of the no-go theorems I mentioned.


There is something beyond it, but the no-go theorems prevent you from explaining or reasoning about it.

We only need to reason that there is something beyond the statistical interpretation, we dont necessarily need to determine what that is.

Fourier wrote: »

I don't really get the issue. A sphere can also be decomposed as a sequence of circles, it's not really any different. This is a separate issue, but there's known to be no contradictions with motion and the Minkowski description.

It's a separate issue pertaining to Minkowski spacetime, so it is entirely pertinent. Afterall, if such a structure does preclude relative motion then, just as QFT represents a reason to accept the circularity of relativity of simultaneity, the preclusion of relative motion would be a [pretty big] reason not to accept it.

The sequence of circles that make up the sphere don't account for relative motion. Just as worldlines frozen in a 4 dimensional structure cannot possibly result in 3D reative motion.

As mentioned, it's the reason Herman Weyl and others [unsatisfactorily and erroneously] invoke consciousness to attempt to explain it.

Fourier wrote: »

Sure, what's your point though?

One such solution is a hidden variables theory. What are the alternatives?

Fourier wrote: »

The sequences of circles was just an analogy. Minkowski space is perfectly compatible with relative motion, I really don't see how it isn't from its mathematical structure. You seem to be confusing Minkowski space with the Blockworld view. Whether the Blockworld is incompatible with relative motion is a separate issue. I think the Blockworld view is compatible with relative as do most physicists and philosophers of physics. I don't hold the Blockworld view however, but to me it seems consistent with relative motion. However the Blockworld is separate from Minkowski space itself.

We don't need to discuss the Blockworld view - although the Blockworld interpretation can be used to demonstrate the issue. We need only discuss the physical 4D structure of Minkowski spacetime, where particles/objects exist as worldlines/worldtubes frozen and unchanging in that structure.

The question is, how do we get from a static structure, with frozen worldtubes, to relative 3D motion. Static and frozen worldtubes do not move, how can they give rise to relative motion?

Fourier wrote: »

You're not getting the point. The alternative is the Copenhagen view, which is that the stuff exists but it is not comprehensible or mathematically modellable. This is called AntiRealism or Non-Representationalism. Hidden variable theories assume the stuff of the microscopic realm is comprehensible and modellable. For this reason they are classed under Realism or Representationalism. Like most physicists in the area I think Representationalism/Realism is not going to work.

The point is that we know we know it exists and that there is something there. We could nearly go so far as to say we know that there must be hidden variables. Our inability to model it mathematically is besides the point.

Fourier wrote: »

I don't know what you mean by "frozen". Newtonian dynamics has similar trajectories defined for all time, but nobody would call things "frozen" in Newtonian dynamics.

Newtonian dynamics was predicated on a universal present moment, where the universal configuration was constantly updating. This allows for relative motion.

Fourier wrote: »

Isn't it clear from the mathematics? Each 3D moment is a slice of the worldtubes. Thus the world tube is a collection of 3D configurations one for each moment. A world tube can describe an object moving from one point to another over time. Trivially so mathematically. The initial section has it at one point and intermediate sections have it at different points along the path and the final intersection has it at its destination.

Indeed, and Minkowski spacetime is the collection of 3D slices for the universe, assembled together - this is where the term Block Universe comes from.

An oft used analogy is that of a movie reel - as referenced by Sean Carroll in What is Time?. The frames in a movie reel can be taken as analogous to the 3D slices of worldtubes of an object in spacetime. What happens when you jump into one of those 3D frames? The world is frozen. there is no motion. There is no projector light to bring those frozen 3D slices to life, in the Minkowski spacetime structure.

Again, this is why Weyl and others have to invoke consciousness to bring 3D relative motion to the 4D structure of Minkowski spacetime.

Fourier wrote: »

It's difficult to say that there is hidden variables because of no-go theorems. They provide strong arguments against hidden variables. It's not that "we" don't have the ability to model it mathematically, it's that it cannot be modelled mathematically at all. Not just by us. There are no variables to describe it is what the no-go theorems suggest. Not that there are and we don't know them.

But there is something going on in the individual experiments. That this cannot be modelled mathematically is either a limitation on our part, or a limitation on the applicability of mathematics.

Fourier wrote: »

It seems to be the latter not the former. It's also a limitation on the applicability of reason.

Nobody thinks "nothing" is going on though. That's not what the realist vs anti-realist debate is about.

Discussing this elsewere also, it strikes me that there are similarities between this and the Buddhist (and perhaps Hindu) ideas that absolute reality is beyond conceptualisation.

I am continually trying to update my understanding based on the different discussions and information I encounter. Usually this results in me presenting my understanding in a matter of fact way, and then getting into what might more accurately be termed disagreements than discussions. After all this time, I might finally be learning to change that approach - old dog new tricks? In that vain, I want to ask rather than declare and see if there is anything that I have missed. Obviously, I have a mental model in mind based on all of the information I have encountered to date, but there may be nuances to that information that I am missing - this usually turns out to be the case. With that said:


In those said "disagreements" I have arrived at the understanding that the Block Universe is incompatible with any indeterministic interpretations of quantum mechanics because the Block Universe is fundamentally deterministic. A key issue with the Block Universe, when it comes to Bell tests is, according to the Block Universe, there can only be one possible outcome in a Bell test and that future outcome is eternally etched in the Block even before the beginning of the experiment - in this case "before" is not intended to suggest that the experimental result occurs temporally prior to the beginning of the experiment, rather that future events co-exist with past and present events.

If QFT is an indeterministic interpretation of QM, then it too would have to be incompatible with the Block Universe.

Would this then mean that an indeterministic interpretation of QFT necessitates a presentist universe? Or is there some nuance that I am missing out on? Possibly a "growing block" universe? Although would a "growing block" universe require some extremely ad hoc assumptions?

As I say, there are usually some nuances that I haven't picked up on.