Q: "Time Dilation: Faster = Longer Wait?

[bobc2]

Which brings me to the question:
If I send someone to get me lunch on another planet, the faster they travel the longer I have to wait?

Semifaded, by now you understand that it does not work that way. I will try to summarize for you the points of view that have been expressed.

First, since there is some interest in presenting the information in the most efficient manner, avoiding additional or redundant information, I'll just provide sketches of the three inertial frames that indicate how much clock time (proper time) is accumulated for each frame associated with the twin paradox scenario. Note that for the frame which represents the traveling twin's return trip, I have started his proper time reading at 21 months, since that is what that twin's clock was reading on arrival at the turning point. ghwellsjr wisely idealized the scenario to allow an instant turn-around. Thus, there is no lost turn-around time for the traveling twin's clock, and his clock time at the final meeting of the twins is read directly on the time scale of the chart. You can then compare that time to the clock time of the final meeting event shown on the stay-at-home's clock. Please credit ghwellsjr for the basic graphic, which I have simply copied from his screens and photo shopped a little.

Beyond that, ghwellsjr has taken this same approach with the addition of more information, particularly with his initial sketch charting the spacing of the proper times for each frame describing the scenario. As he has pointed out, you can compare directly on the stay-at-home frame the time increments between the three frames (illustrating the time dilation concept). This is a particularly good choice for those who like to avoid any inference about Minkowski's 4-dimensional space-time, which may not have been a motive of ghwellsjr's since I think he was trying to boil the presentation down to the simplest principles.

My embellishments to ghwellsjr's graphical presentation (see post #65) was intended to carry the picture into the context of the Minkowski 4-dimensional space-time picture. Of course you will decide if it is of any interest to you. You may have picked up on something of a controversial aspect on the special relativity topic.

There are those who feel that the 4-dimensional geometric interpretation of Minkowski should not be taken literally, because there may be other different interpretations of time dilation and length contraction besides Minkowski's (Lorentz Ether Theory--LET--is the most popular contender). Many physicists feel that special relativity theory does not select any particular one of these interpretations--so it is best to not slant presentations of special relativity (particularly on a forum that tries to avoid speculative ideas, i.e., just stick to fundmental observations and do not make more of these than are directly inferred). It is felt that discussion of these alternative interpretations of relativity should be reserved for the philosophy forum. Many of those who reject the physical reality interpretation of the 4-dimensional spac-time still embrace it as a valuable mathematical representation of special relatity that does not infer a physical reality.

Vandam and I may be the only members of the forum here who feel that the Minkowski geometric picture of special relativity directly refers to a 4-dimensional external physical reality (many refer to this as the "block universe").

However, we are not the only ones in the larger community of physicists who feel that the Minkowski 4-dimensional space-time picture should be understood as physical reality. Paul Davies, in his book "About Time" claims that most physicists hold this view, but I've never seen anything like a poll of physicists to back up his statement. Certainly there are many very prominent physicists who hold this view.

So, given these differing views it is not surprizing that you will find some tension among the posts on this forum. When it gets to the point of circular comments and personalizing the discussions, or too philosophical, the forum arbitrator will step in.

 

[Dale]

Vandam and I may be the only members of the forum here who feel that the Minkowski geometric picture of special relativity directly refers to a 4-dimensional external physical reality (many refer to this as the "block universe").

No, there are many other block-universe sympathizers on the forums, including myself.

The distinction that you and Vandam have is that you are the only members that don't seem to realize that it is just an untestable philosophical interpretation of SR and not an unavoidable scientific deduction. In your fervor to promote a philosophical viewpoint you step way beyond what is scientifically justifiable. Most of the opposition you face is opposition to you and Vandam's overreaching assertion of an untestable philosophy, rather than opposition to the block universe concept itself.

 

[bobc2]

Now I want to show three more IRF's...

ghwellsjr, I was immersed in preparing my last post for Semifaded and by the time I got it posted I had to bail out here for an appointment. I'm anxious to get back to it. At a glance it looks like you have done a very nice job of presenting the kinds of details that further enhance the time dilation picture for the twin paradox scenario. I'm sure Semifaded will gain more insight from it. Thanks.

 

[Vandam]

No, there are many other block-universe sympathizers on the forums, including myself.

The distinction that you and Vandam have is that you are the only members that don't seem to realize that it is just an untestable philosophical interpretation of SR and not an unavoidable scientific deduction. In your fervor to promote a philosophical viewpoint you step way beyond what is scientifically justifiable. Most of the opposition you face is opposition to you and Vandam's overreaching assertion of an untestable philosophy, rather than opposition to the block universe concept itself.

As far as I can remember -at least a general impression I got- you have problems with block universe because you refuse accepting there are events out there, ready to be observed. For you, only your own now event is 'real'. Period. No wonder any discussion about the meaning of a mathematical number becomes problematic and can be considered philosophy...
If you think there are no pace-like events out there, ready to be observed (Ghwellsjr also literally said he is not interesed in the origin of observations), then not only Block Universe, but also Special Realtivity has to move to philosophy! The whole lot. And we then have to discuss what you mean by 'observers' and 'observing'. And we will definitely have to look what space and time cooridinates stand for. Even throw in some semantics.
You probably are too much influenced by QM. Do you believe the moon is out there if you do not look at it? Be carefull not to slide into solipsism. Solipsism is methaphysics, not physics. This is a physics forum. Einstein believed in an observer independent world, so it's fair the work in that context.
I think it might me necessary to go through a discussion of relativity of simultaneity again. I will show you that if you believe in an observer independent world, SR automatically leads to block universe. I might start a new thread on that (but not before next year..).

In the sketches below I show two time coordinate charts of two relative moving space travelers. Lorentz Tranformations, gamma, etc will give you the numbers. But physics is more than mathematics. More than just charts with coordinates. I show you where the observations making up the charts come from: 3D world sections through 4D block spacetime.

 

[Dale]

As far as I can remember -at least a general impression I got- you have problems with block universe

You recall incorrectly. I have no problems with the block universe interpretation. I only have problems with your presentations of it.

Be carefull not to slide into solipsism. Solipsism is methaphysics, not physics.

Here is a good example. I have never posted anything remotely in support of solipsim, nor has anyone else that I noticed. I don't understand your weird penchant for labeling anyone who disagrees with you as a "solipsist".

I will show you that if you believe in an observer independent world, SR automatically leads to block universe.

And this is simply false. LET is an alternative interpretation of SR with an observer independent world that is not the block universe.

They are both interpretations of SR meaning that they lead to the same experimental predictions in all cases and therefore cannot be distinguished experimentally.

 

[bobc2]

No, there are many other block-universe sympathizers on the forums, including myself.

Good point, DaleSpam. In my comments I should have made a distinction between those who are favorable to the block universe concept based on philosophical considerations vs. those who feel that block universe is directly implied as a requirement of special relativity. You are probably correct in recognizing Vandam and I as the only forum members who feel that block universe is a requirement of special relativity.

The distinction that you and Vandam have is that you are the only members that don't seem to realize that it is just an untestable philosophical interpretation of SR and not an unavoidable scientific deduction. In your fervor to promote a philosophical viewpoint you step way beyond what is scientifically justifiable. Most of the opposition you face is opposition to you and Vandam's overreaching assertion of an untestable philosophy, rather than opposition to the block universe concept itself.

I understand the distinction you are recognizing. And certainly with a theory like special relativity there is potential for some to interpret special relativity under the influence of his philosophical bias rather than basing the interpretation on measured data.

But, I want to emphasize that Vandam and I feel this model is based correctly on physical measurements and theoretical predictions. I presented the theoretical motivation in my original post in this thread. No one has responded with a counter argument that would logically refute the logic I presented. Vandam and I have both presented examples of measurements that would validate the theory. We contend that is physics, not philosophy. However, some have drawn on their philosophical bias to refute the block universe.

I'm not suggesting you have based your analysis on philosophical bias, because you have pointed to LET as a theory that predicts the same outcome as Einstein's special relativity. Thus, one could not single out block universe as unique.

Nevertherless, here are a couple of points that influence me:

1) LET is a largely discarded (or at least, ignored) theory. Virtually all physicists doing work in relativity (especially the general case) do it in the context of a 4-dimensional geometry. Einstein acknowledged that without Minkowski's 4-dimensional concept he would have gotten nowhere with general relativity.

2) The Einstein-Minkowski picture of special relativity is foundational, whereas LET is ad hoc.

3) It has been pointed out (sorry I cannot give you a reference) that LET is manifestly incompatible with the experimental results of entanglement tests, whereas block universe can be analyzed as compatible with those results.

But, my main point here is that I maintain that the block universe is a concept which is an integral part of special relativity (not a separate theory), derived from the special theory of relativity and also supported by measurements. The philosophy of physics was a required course for our PhD curriculum. On the last day of the course our professor asserted that "...physics never has and never will contribute anything to the understanding of physical reality..." I've been leary of philosophers ever since.

So, you should not characterize my position as one based on philosophy.

I may be guilty of faulty logic in interpreting the theoretical and experimental results.

 

[PeterDonis]

the block universe is a concept which is an integral part of special relativity (not a separate theory), derived from the special theory of relativity and also supported by measurements.

Just to add some more thoughts to the discussion:

(1) If by "the block universe is integral to SR" you just mean "SR uses 4-dimensional spacetime to construct models", then of course nobody can dispute that. The disagreement, to the extent there is one, is about claims like "SR uses 4-D spacetime, so the block universe is what reality is really like".

(2) SR, as a physical theory, is wrong. It uses flat spacetime, but we know that spacetime is curved if there is any stress-energy present, and we know there is stress-energy present in the real universe. So we can't use SR, by itself, to justify claims about "what reality is really like".

(3) GR, as a physical theory, allows spacetime to be curved, and it also uses 4-D spacetime, so if we are going to argue that 4-D spacetime is "what reality is really like", we would do better to base such arguments on GR, not SR.

(4) However, there are formulations of GR, such as the ADM formalism, that view a 4-D spacetime model as a model of a 3-space "evolving in time". So the "block universe" is not the only possible interpretation of GR either.

(5) More importantly, though, GR, as a physical theory, is also wrong, because it doesn't include quantum mechanics. So we can't use GR, by itself, to justify claims about "what reality is really like" either.

(6) When we include quantum mechanics, we don't have a good theory (yet) that includes gravity. However, we do know one thing: quantum mechanics introduces an element of uncertainty that is not present in classical GR. And a key feature of GR (or SR) that is necessary to any argument that the block universe is "what reality is really like" is determinism. So when we include quantum mechanics, we can no longer argue that GR (or SR) leads us to the "block universe".

 

[bobc2]

Just to add some more thoughts to the discussion:

Thanks for your very well reasoned response. I'll try to add in a couple of my points of view.

(1) If by "the block universe is integral to SR" you just mean "SR uses 4-dimensional spacetime to construct models", then of course nobody can dispute that. The disagreement, to the extent there is one, is about claims like "SR uses 4-D spacetime, so the block universe is what reality is really like".

Then, in your mind what does the 4-dimensional space-time model represent?

(2) SR, as a physical theory, is wrong. It uses flat spacetime, but we know that spacetime is curved if there is any stress-energy present, and we know there is stress-energy present in the real universe. So we can't use SR, by itself, to justify claims about "what reality is really like".

We are interested first in understanding physical reality locally. Then, of course it must continue to be a part of the more general model.

(3) GR, as a physical theory, allows spacetime to be curved, and it also uses 4-D spacetime, so if we are going to argue that 4-D spacetime is "what reality is really like", we would do better to base such arguments on GR, not SR.

Of course. It's just more logical to develop the local concepts of physics, then generalize them for the curved 4-dimensional universe.

(4) However, there are formulations of GR, such as the ADM formalism, that view a 4-D spacetime model as a model of a 3-space "evolving in time". So the "block universe" is not the only possible interpretation of GR either.

On the contrary I feel that the ADM formulation with the foliations maintains a picture of a block universe. There may be complications, mathematically and conceptually, with regard to foliating in particular ways to accommodate certain different world line paths through the curved universe. I don't think it is necessary to get side tracked with special issues like black holes. We are just recognizing a simple fundamental concept for which we may not have all of the details worked out.

(5) More importantly, though, GR, as a physical theory, is also wrong, because it doesn't include quantum mechanics. So we can't use GR, by itself, to justify claims about "what reality is really like" either.

Block universe in the special or general form does not have to include the usual concept of causality as considered casually. Notice that with the block universe causality does not have the same physical meaning as it does in the time evolving 3-dimensional model. So, causality at the elementary particle level is not necessary for the physical description. This should be true with both block universe and QM. That's why the entanglement experimental results are consistent with the block universe model.

(6) When we include quantum mechanics, we don't have a good theory (yet) that includes gravity. However, we do know one thing: quantum mechanics introduces an element of uncertainty that is not present in classical GR. And a key feature of GR (or SR) that is necessary to any argument that the block universe is "what reality is really like" is determinism. So when we include quantum mechanics, we can no longer argue that GR (or SR) leads us to the "block universe".

That is incorrect. That's one of the significant aspects of the block universe--it is not necessary to predict the future in every detail. And the future does not have to be determined in a way that includes both macro and micro properties of the universe. The universe is just all there--the arrangement of worldlines of particles did not depend on the evolving in time of the 3-dimensional worlds (various hyperplanes--or GR foliations) at the elementary particle level. However the block universe was created or put together (we avoid any discussion of that, avoiding obvious traps into philosophy and theology), the presense of forces and response to forces (causality) were built in as part of the design. It would not be necessary to enforce the macro patterns of worldlines all the way down to the elementary particle. But, the observation and operation of physical laws in the sense of an evolving 3-D world is an illusion. Although, a clever construction of the block universe could arrange the elementary particle worldlines so as to present an appearance of causality emerging from interactions at the micro level.

 

[PeterDonis]

Then, in your mind what does the 4-dimensional space-time model represent?

A model, which works fine as an approximation in lots of situations.

We are interested first in understanding physical reality locally.

That's an assumption about what "physical reality" is like. What if the true "physical reality" is not local?

On the contrary I feel that the ADM formulation with the foliations maintains a picture of a block universe.

It depends on what you mean by "block universe". Once again, if all you mean by it is "we can use 4-D spacetime as a model", then of course the ADM formulation is consistent with that. But the ADM formulation does not claim that a 4-D spacetime that "exists all at once" is what reality "is really like".

Notice that with the block universe causality does not have the same physical meaning as it does in the time evolving 3-dimensional model.

Why not? Both models use the light cones to determine which events are causally connected and which are not. You're going to have to elaborate on what you think the "physical meaning" of causality is if you think it's something more than just the light cone structure.

So, causality at the elementary particle level is not necessary for the physical description.

Why not? I don't see this either.

That's one of the significant aspects of the block universe--it is not necessary to predict the future in every detail.

Huh? That's the whole *point* of the "block universe" as a claim about "reality" as opposed to just a model. It claims that the entire 4-D spacetime "exists all at once". That means a single self-consistent solution to whatever physical laws determine the 4-D spacetime structure is what "exists". If that doesn't include every detail, then it isn't a well-defined 4-D spacetime structure.

And the future does not have to be determined in a way that includes both macro and micro properties of the universe.

The word "future" doesn't have a well-defined meaning here. You should just say that the entire 4-D spacetime exists, period. But that 4-D spacetime has to include all "macro and micro properties"; otherwise what are you saying "exists"?

The universe is just all there--the arrangement of worldlines of particles did not depend on the evolving in time of the 3-dimensional worlds (various hyperplanes--or GR foliations) at the elementary particle level.

But it does depend on whatever physical laws determine the 4-D solution. In SR, that 4-D solution is flat Minkowski spacetime, period. In GR, the 4-D solution is determined by the Einstein Field Equation plus boundary conditions. The 4-D solution is "just all there" in the "block universe" view, but that doesn't mean it isn't determined by laws. The laws don't "act in time", but they still act.

However the block universe was created or put together (we avoid any discussion of that, avoiding obvious traps into philosophy and theology),

You're also ignoring physical laws. See above. Physical laws are not "traps into philosophy and theology". They're the only justification for adopting any kind of viewpoint like the "block universe" in the first place. SR and GR are physical laws.

the presense of forces and response to forces (causality) were built in as part of the design.

Sure, they're part of the laws; in this case, the laws that determine the stress-energy tensor, including whatever additional field equations (such as Maxwell's Equations) are needed to fully specify the 4-D solution for the stress-energy tensor.

It would not be necessary to enforce the macro patterns of worldlines all the way down to the elementary particle.

This makes no sense. If you don't do this, you don't have a 4-D solution, hence you don't have a "block universe". Particle worldlines are part of the solution.

But, the observation and operation of physical laws in the sense of an evolving 3-D world is an illusion.

On the "block universe" view, yes, you could say this; but it would be very misleading if it induced people to draw the additional conclusion that there are no physical laws operating at all. As I said above, that is not at all the case.

Although, a clever construction of the block universe could arrange the elementary particle worldlines so as to present an appearance of causality emerging from interactions at the micro level.

As I said above, the elementary particle worldlines *are* arranged; they are determined as part of the 4-D solution. You can't just arbitrarily specify them; they are determined by the physical laws.

Also, you're again misunderstanding what "causality" means. In the 4-D spacetime view, causality just means the 4-D spacetime, as a geometric object, has a light cone structure, which determines whether any given pair of events is causally connected or not. That's all part of the 4-D spacetime solution; if you don't have it, you don't have a "block universe".

 

[bobc2]

Sorry to not respond to you, PeterDonis. I just spent considerable time responding to each point in your last post. However, the PF program timed out, and when I responded to the request to log back in I was shut out and all of my text was lost. But, I think we have both expressed our points of view pretty well.

At the end of my post I suggested we terminate our comments relative to block universe. Once you start getting into some of the implications of block universe it can get quite controversal and eventually get way too far out into the weeds. I'm not sure if it is a good idea to try again to respond to your post. If Semifaded and others here wish to see my response, I would be glad to oblige. But, I suspect there would be relief to see an end to this discussion.

You have presented an excellent summary of the main objections to be brought up against the block model (as well as some of ghwellsjr and DaleSpam's inputs). I think it is O.K. for us to agree to disagree on this subject.

Now, I still need to go back and look at ghwellsjr's latest nice graphs.

 

[Vandam]

(Sorry, I'm a bit late with this post.)
I think what Bob tries to convey is that Block Universe not only embraces deterministic but also indeterministic processes.
If all of a sudden a particle pops up 'out of nothing', the mathematics can only give us probabilities. But the particle popping out of nothing is already part of 4D spacetime. Causality is not necessarily a feature of Block universe. I guess you can have a block universe with ONLY indeterministic processes, but that would be really a weird one. Actually there might indeed be or a lot weird block universe bubbles out there, but in those Block universes 'life' as we now it might not work. That's probably why we are stuck in our Block universe.
In a fully deterministic Block universe 'causality is nothing more than the glue that holds the events together. Causality is not the 'cause' of events to happen. In block universe causality is only a result of first seeing A, and then B. (I think it was David Hume 250 years ago that brought that up). I do not know why our block universe is what it is so that we in the successioj of 3D cuts perceive causality and physical lanws. That discussion would indeed be a philosophical or theological issue... at this stage: maybe in a hundred years physics will have an explanation (hopefully thanks to Bob's and my, and many other's perseverance).
The interesting thing in physics is that our block universe apparently does not contain only fully deterministic relations (on a very small scale i.e). That's a great interesting discovery if it turns out to be correct... But it does't refute Block universe. On the contrary: Bob and I think QM proves that block universe is correct. But whether QM is compatible with Block universe or not is way off topic here (actually I am not that much involved in QM, I prefer to leave that topic to Bob). But SR's relativity of simultaneity = block universe. That's a good start.

 

[PeterDonis]

If all of a sudden a particle pops up 'out of nothing', the mathematics can only give us probabilities. But the particle popping out of nothing is already part of 4D spacetime.

Which means that unless you *know* all the events at which particles "pop out of nothing", you don't have a well-defined 4D spacetime. From the 4D viewpoint, a particle "popping out of nothing" just means it has a worldline that doesn't extend all the way from minus infinity to plus infinity: instead it appears at some finite place. But in order to properly define a 4D spacetime, you have to define *all* the worldlines, including those that happen to start at a finite place (if there are any).

Causality is not necessarily a feature of Block universe.

Sure it is; a worldline that happens to appear at a finite place still has to keep within the light cones along its entire length.

In block universe causality is only a result of first seeing A, and then B. (I think it was David Hume 250 years ago that brought that up).

But first seeing A and then seeing B is still governed by laws. They may be probabilistic laws, but they're still laws. And the term "first" isn't really appropriate here, because the "block universe" viewpoint says that the entire 4D spacetime just exists, it doesn't evolve in time. So really "causality" in a block universe means that event A has a particular geometric relationship to event B. That's true: the 4D spacetime has a light cone structure even if some worldlines don't extend all the way from one boundary to the other. See above.

The interesting thing in physics is that our block universe apparently does not contain only fully deterministic relations (on a very small scale i.e). That's a great interesting discovery if it turns out to be correct... But it does't refute Block universe.

Nor does it *prove* it. Just following this statement you switch your ground, from this...

Bob and I think QM proves that block universe is correct.

...to this...

But whether QM is compatible with Block universe or not

QM being compatible with the block universe is very different from QM proving that the block universe is correct. I'll agree, for purposes of argument here, that QM can be made compatible with a "block universe" interpretation (though there are still lots of issues with doing that), but that does not show that QM *requires* a block universe interpretation. This is the same argument we've had about your claim that relativity of simultaneity requires a block universe; it doesn't. It's compatible with a block universe, but it doesn't require it.

But SR's relativity of simultaneity = block universe. That's a good start.

Not if nobody except bobc2 agrees with it.

 

[Dale]

Good point, DaleSpam. In my comments I should have made a distinction between those who are favorable to the block universe concept based on philosophical considerations vs. those who feel that block universe is directly implied as a requirement of special relativity. You are probably correct in recognizing Vandam and I as the only forum members who feel that block universe is a requirement of special relativity.

I suspect that many of the mainstream physicists you referred to earlier may also fall into the same camp.

Vandam and I have both presented examples of measurements that would validate the theory. We contend that is physics, not philosophy.

The problem is that those exact same measurements would also validate LET. They do not allow you to choose between the two on the basis of the proposed experiments. In fact, there is no possible experiment since both use the Lorentz transform for making all of their experimental predictions. Therefore the only possible criteria to choose one over the other is philosophical.

1) LET is a largely discarded (or at least, ignored) theory. Virtually all physicists doing work in relativity (especially the general case) do it in the context of a 4-dimensional geometry. Einstein acknowledged that without Minkowski's 4-dimensional concept he would have gotten nowhere with general relativity.

Agreed, but this is peer-pressure, not empirical evidence.

2) The Einstein-Minkowski picture of special relativity is foundational, whereas LET is ad hoc.

Agreed, but this is philosophy, not evidence.

3) It has been pointed out (sorry I cannot give you a reference) that LET is manifestly incompatible with the experimental results of entanglement tests, whereas block universe can be analyzed as compatible with those results.

This is false. Any result which would invalidate LET would also invalidate the block universe since both make all of the same predictions.

The philosophy of physics was a required course for our PhD curriculum. On the last day of the course our professor asserted that "...physics never has and never will contribute anything to the understanding of physical reality..." I've been leary of philosophers ever since.

So, you should not characterize my position as one based on philosophy.

But your position is one based on philosophy, that is all that it possibly can be based on since it cannot be based on evidence.

If you prefer, you can say that it is based on aesthetics rather than philosophy. I am not sure there is any difference, but maybe "aesthetics" doesn't carry the negative connotation you have of "philosophy". I am certainly willing to use a different word if you feel that it would be less objectionable.

 

[Dale]

Bob and I think QM proves that block universe is correct. ... But SR's relativity of simultaneity = block universe.

Both of these are false. Both QM and the relativity of simultaneity are compatible with LET as well as the block universe.

 

[Vandam]

Both of these are false. Both QM and the relativity of simultaneity are compatible with LET as well as the block universe.

Please explain how relativity of simultaneity is compatible with LET.
That's a contradiction in terms.
Relativity of simultaneity is compatible with the Lorentz transformations. But not with LET. LET does not give a physical explanation of the LT (Lorentz admited this).
SR does. That's Einstein's contribution.
See also my post:
https://www.physicsforums.com/showpost.php?p=4203539&postcount=14

 

[Dale]

Please explain how relativity of simultaneity is compatible with LET.
That's a contradiction in terms.
Relativity of simultaneity is compatible with the Lorentz transformations. But not with LET.

Nonsense, LET uses the Lorentz transformations for its predictions, so any feature of the LT is obviously compatible with LET. The relativity of simultaneity is an inherent part of the LT. In LET just as in SR different frames disagree about whether or not two events are simultaneous.

 

[Vandam]

Nonsense, LET uses the Lorentz transformations for its predictions, so any feature of the LT is obviously compatible with LET. The relativity of simultaneity is an inherent part of the LT. In LET just as in SR different frames disagree about whether or not two events are simultaneous.

Nonsense. You have to step away from the ether (LET) to make all the time coordinates physical. Lorentz never did this. And he admited this:
<<The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t' must be regarded as no more than an auxiliary mathematical quantity. In Einstein's theory, on the contrary, t' plays the same part as t; if we want to describe phenomena in terms of x'; y'; z'; t' we must work with these variables exactly as we could do with x; y; z; t.>>
The LT only have a full physical meaning in SR, not LET.

 

[Dale]

Nonsense. You have to step away from the ether (LET) to make all the time coordinates physical.

So what? The relativity of simultaneity doesn't require you to "make all the time coordinates physical", whatever that means. All it requires is that different frames disagree on which events are simultaneous, which they do in LET.

 

[Vandam]

So what? The relativity of simultaneity doesn't require you to "make all the time coordinates physical", whatever that means. All it requires is that different frames disagree on which events are simultaneous, which they do in LET.

That's mathematical mumbo jumbo with no physical sygnificance.
You are lucky Einstein does not read you.

 

[Dale]

That's mathematical mumbo jumbo with no physical sygnificance.

I agree. And yet, there is no experimental evidence which can select the LET mumbo jumbo over the block universe mumbo jumbo.

You are lucky Einstein does not read you.

As long as we are channleing Einstein and pretending to know what he would say, I think that he would strongly object to your idea that any coordinates are physical. Certainly by the time GR was well established it was understood that coordinates are not physical, they are just mathematical conveniences.

 

[Vandam]

I agree. And yet, there is no experimental evidence which can select the LET mumbo jumbo over the block universe mumbo jumbo.

I wonder what you exactly mean by 'experimental evidence'. That includes observation and measurements. We then have to agree on what you observe. Without observer independent events you only will end up in some bizarre philosophical interpretations such as solipsism. And if you do accept observer independent events as Einstein saw it (he was a realist and not a solipsist) it leads automatically to block universe.

Lorentz admitted that LT time-coordinates can not work in an ether (LET) context. LET with LT is a contradiction in terms. If you think you know better than Lorentz himself you have to do more work to convince me.

 

[Vandam]

Here is what I mean.
Green is the ether world. If you put green's coordinates of event A (0.5, 0.5) in the LT it gives you the red coordinates (Lorentz' local time) (0,289, 0,289).
The red coordinates (time and space dimensions) have no meaning at all in the green ether context. Not even if you consider the green ether through event R3.
In LET only the green coordinates have a physical meaning. Not the red ones. For the red ones you have to consider a physical red 3D world through R3 and A, which Einstein's SR allowed, but not Lorentz' LET.
That's why Lorentz said:
<<The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t' must be regarded as no more than an auxiliary mathematical quantity. In Einstein's theory, on the contrary, t' plays the same part as t; if we want to describe phenomena in terms of x'; y'; z'; t' we must work with these variables exactly as we could do with x; y; z; t.>>
The LT only have a full physical meaning in SR, not LET.

 

[Dale]

I wonder what you exactly mean by 'experimental evidence'. That includes observation and measurements.

Yes, exactly. And LET predicts the exact same observations and measurements in all situations as does the block universe. Thus there can never be any experimental evidence distinguising the two, regardless of your philosophical preferences and arguments.

 

[bobc2]

Yes, exactly. And LET predicts the exact same observations and measurements in all situations as does the block universe.

How do you square that with the obvious: A 3-D universe evolving in time is physically not the same as a 4-D universe that is "...just all there." Or, "...things do not happen, they are just there."

Thus there can never be any experimental evidence distinguising the two, regardless of your philosophical preferences and arguments.

Except that LET is not consistent with the results of entanglement experiments, whereas the block universe is.

And again, the block universe is more fundamental as compared to the ad hoc LET. It's a little bit like the difference between the heliocentric model of our solar system vs. the mathematical model of the Earth centered solar system with cycles and epicycles, etc.

 

[Austin0]

Here is what I mean.
Green is the ether world. If you put green's coordinates of event A (0.5, 0.5) in the LT it gives you the red coordinates (Lorentz' local time) (0,289, 0,289).
The red coordinates (time and space dimensions) have no meaning at all in the green ether context. Not even if you consider the green ether through event R3.
In LET only the green coordinates have a physical meaning. Not the red ones. For the red ones you have to consider a physical red 3D world through R3 and A, which Einstein's SR allowed, but not Lorentz' LET.
That's why Lorentz said:
<<The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t' must be regarded as no more than an auxiliary mathematical quantity. In Einstein's theory, on the contrary, t' plays the same part as t; if we want to describe phenomena in terms of x'; y'; z'; t' we must work with these variables exactly as we could do with x; y; z; t.>>
The LT only have a full physical meaning in SR, not LET.

It is true that Lorentz considered "the idea that the variable t only can be considered as the true time and that my local time t' must be regarded as no more than an auxiliary mathematical quantity. And SR considers both equivalent. But what that means is that SR considers BOTH t and t' as simply mathematical quantities with no implication that either one was "true" time or defining actual or physical simultaneity.

So your implication that SR considers t and t' as absolute in the sense Lorentz meant is not logically valid and in fact is antithetical to SR as it depends on the idea of an absolute scale or reference. You can interpret Einsteins thoughts as meaning conventionally synchronized clocks define actual or absolute simultaneity , which is the basis of your interpretation of Block Time but I don't think you can back up that interpretation with Einstein's actual statements and I flatly don't believe it. It seems fundamental to SR that simultaneity is totally indeterminate and relative with the exception of co-located events.

It is true that SR denies the classical concept of a universal or absolute now but it does not replace it with a set of many universal or absolute "nows" . One for every velocity.

In actuality SR does not explicitly negate the possibility of a universal "now" it simply shows that any such instant is indeterminate and thus superfluous. Like an ether, or absolute motion.

Even given a hypothetical persistent and pre-created 4-d continuum , it is clear that consciousness exists in a limited slice of time and so in effect moves. SO there is neither any objection to the possibility that all consciousness is absolutely simultaneous. I.e a single slice of awareness progressing through the continuum nor any means of empirically falsifying such a concept.
It is self evident that the various clocks throughout the universe would not correspond to this simultaneity but how could this be observed or measured within the structure?

There may be a number of people who are open to the possibility of Block time in some form ( I don't completely reject it) but I would be surprised if there are many people who understand SR who consider conventionally synchronized clocks to be absolutely simultaneous.
WHich is exactly what you are claiming wouldn't you agree?

 

[Dale]

How do you square that with the obvious: A 3-D universe evolving in time is physically not the same as a 4-D universe that is "...just all there." Or, "...things do not happen, they are just there."

It isn't obvious to me. If a 3D evolving universe were physically different from a 4D universe then I would expect there to be some testable consequences, which there aren't. So I think they are philosophically different but physically identical.

Except that LET is not consistent with the results of entanglement experiments, whereas the block universe is.

Please provide a mainstream scientific reference for this claim. Since both LET and QFT use the LT your claim seems patently false to me.

And again, the block universe is more fundamental as compared to the ad hoc LET.

I agree completely, but this is a philosophical or aesthetic preference.

 

[bobc2]

No, LET is consistent with entanglement since the LT is used by modern QFT.

That does not imply that LET is consistent with results of entanglement experiments. On the contrary, LET specifically requires light cone causality--that's the basis of Lorentz's derivations. That's why LET is tied directly to a 3-D universe evolving in time model. Entanglement experimental results violate light cone causality. Violation of light cone causality is not a problem for the block universe model. Thus, results of entanglement experiments provide the distinction you are looking for.

 

[PeterDonis]

Entanglement experimental results violate light cone causality.

No, they don't. You can't send signals faster than light by using entanglement. The statistical correlations between results *appear* to "travel faster than light", but that's only an appearance; when you work out the underlying quantum field theory, the field operators commute at spacelike separations, so light cone causality is obeyed.

Violation of light cone causality is not a problem for the block universe model.

It would be if it actually happened; the block universe model still depends on a well-defined light cone structure that determines causal relationships between events.

 

[Dale]

That does not imply that LET is consistent with results of entanglement experiments.

Yes, it does. Entanglement follows the LT, just as predicted by LET. That is the epitome of consistency.

PeterDonis already dealt with the rest of your post.

 

[Vandam]

Austin0,
Thanks for your reaction, I read it 4 times, but I am unable to understand what you exactly mean. I especially do not understand your 'absolute' and universal' terminology in the context what I mean. I think you didn't understand what I mean.
If my spacetime diagram is wrong , tell me where it is wrong.
How would you draw the spacetime diagram showing the Lt time coordinates?

Same advice for Dalespam.
If my spacetime diagram is wrong , tell me where it is wrong.
How would you draw the spacetime diagram showing the Lt time coordinates?
You just keep on telling me that the LT transformations give the same result in LET and SR, but if you can not tell me where the primed time coordinates should be read on a simple ether space and time diagram I am not impressed with your statement.

 

[bobc2]

No, they don't. You can't send signals faster than light by using entanglement. The statistical correlations between results *appear* to "travel faster than light", but that's only an appearance; when you work out the underlying quantum field theory, the field operators commute at spacelike separations, so light cone causality is obeyed.

You are missing the whole point of my comments. I didn't say that signals are sent faster than light with entangled particles. It is for exactly that reason that LET fails with entanglement experiments. LET was developed specifically for explaining related events via the model of a fixed ether through which all processes evolve as a result of signals transmitting at the speed of light as ether waves.

Processes involving entangled particles at a distance (not local) simply do not fit that model. LET is inconsistent with that. A fixed ether medium does not work with quantum field theory. However, the block universe model is not at all inconsistent with that.

It would be if it actually happened; the block universe model still depends on a well-defined light cone structure that determines causal relationships between events.

It certainly does not. The worldlines of the elementary particles are all there in the 4-dimensional structure. They can begin anywhere and end anywhere QM and QFT would like. It has no constraints by a fixed ether which includes only light cone causal influences.

 

[PeterDonis]

I didn't say that signals are sent faster than light with entangled particles. It is for exactly that reason that LET fails with entanglement experiments. LET was developed specifically for explaining related events via the model of a fixed ether through which all processes evolve as a result of signals transmitting at the speed of light as ether waves.

I don't understand your point. You agree that entanglement doesn't send signals faster than light; and you say LET doesn't involve sending signals faster than light. So where's the discrepancy?

entangled particles at a distance (not local)

If entanglement can't be used to send signals faster than light, then it *is* local. That's the whole point. "Local" in a relativistic theory is indistinguishable from "causal". In the quantum version, "local" means "field operators commute at spacelike-separated events", which is the same as "causal".

A fixed ether medium does not work with quantum field theory.

Sure it does. See above.

The worldlines of the elementary particles are all there in the 4-dimensional structure. They can begin anywhere and end anywhere QM and QFT would like.

Which means they can only embody causal relationships permitted by QM and QFT. You seem to have a misconception that QM and QFT somehow relax the rules about causal relationships between events. They don't. The observed worldline of a particle with nonzero rest mass can still only be a timelike worldline. You can have "virtual" worldlines for the particle which are not timelike (at least, that's how the "sum over histories" view of QFT would describe it), but their amplitudes will always cancel out in the observable; the observed worldline can only be timelike.

 

[Dale]

If my spacetime diagram is wrong , tell me where it is wrong.

I never said your diagram was wrong. Do you think that I did?

Regarding impressing you, frankly it isn't a requirement for being right.

 

[Vandam]

I never said your diagram was wrong. Do you think that I did?

If you accept my diagram you can not say that the LT make sense in LET.
So there's a contradction in terms.
Don't you see that?

 

[zonde]

Here is what I mean.
Green is the ether world. If you put green's coordinates of event A (0.5, 0.5) in the LT it gives you the red coordinates (Lorentz' local time) (0,289, 0,289).
The red coordinates (time and space dimensions) have no meaning at all in the green ether context. Not even if you consider the green ether through event R3.
In LET only the green coordinates have a physical meaning. Not the red ones. For the red ones you have to consider a physical red 3D world through R3 and A, which Einstein's SR allowed, but not Lorentz' LET.
That's why Lorentz said:
<<The chief cause of my failure was my clinging to the idea that the variable t only can be considered as the true time and that my local time t' must be regarded as no more than an auxiliary mathematical quantity. In Einstein's theory, on the contrary, t' plays the same part as t; if we want to describe phenomena in terms of x'; y'; z'; t' we must work with these variables exactly as we could do with x; y; z; t.>>
The LT only have a full physical meaning in SR, not LET.

The red sentence is wrong.

Red coordinates provide valid account of measured time and distance with rulers and clocks (brought) at rest in that coordinate time. In green coordinate system we have to add specific law in order to predict elapsed time on a moving clock (given we know elapsed time on the same clock when it is brought at rest in green coordinate system).