Does the Block Universe Theory Affect Our Understanding of Time and Reality?

[bobc2]

OK, calculate any specific measurement that the block universe interpretation predicts and I will calculate using the LET interpretation.

If the thought experiment outcome does not contradict LET, that just means that LET also requires 4-dimensional objects. That in no way detracts from the 4-dimensional objects required of special relativity.

 

[bobc2]

...However, you should be careful in specifying exactly what this argument proves. It proves that any event on the third observer's worldline that has sent a light signal which has been received by some other observer, must "exist" (because it's been observed)...

Wait a minute--you've just left out the most important part: Brown and Blue share the same simultaneous 3-D space at an event where each one occupies a different 3-D cross-section of the 4-D universe. Further, Brown's simultaneous space includes one 3-D cross-section of the 4-dimensional Light Brown body, and Blue's simultaneous space includes a different 3-D cross-section of the 4-dimensional Light Brown.

...It does *not* prove that the *entire* worldline of the third observer, including its extrapolation to "future" events that have not yet sent light signals to anyone, must "exist".

I take it from the way you stated this that you at least acknowledge that we have established that Light Brown, as a minimum, has been shown to exist at two events along his world line, one being simultaneous with Brown and the other being simultaneous with Blue while Brown and Blue share their intersection event.

In the interest of brevity I just indicated that by extending the experiment we could establish the same Light Brown existence for any arbitrary point along his world line--or with sufficient tedium (perhaps with the use of mathematical induction) we could establish the existence of Light Brown at a continuum of points along the world line, i.e., a 4-dimensional object.

...But many of the claims you have made about the "block universe" strongly suggest, at the very least, that you are making the latter claim, which is not justified by your argument. That's why you have gotten pushback from several people here, including me.

Of course that is the claim I have made. A push-back is not unexpected.

And of course a stronger argument could be made, providing more explicit data, adding more and more observers with different Lorentz boosts, all intersecting in a way that shares one point from their respective inertial frames of reference.

The experiment can be further embellished by establishing an array of objects, spaced at specified distances from the Brown observer and all at rest in Brown's frame of reference (each accompanied by a clock, computer based controls system with appropriate algorithms for sending transmissions of various kinds of on-board information--two-way distance, computations, time marked videos, etc.).

Yet another array of objects can be sent out at the same velocities, programmed to travel to selected rest frame objects, then return to the Brown observer (all the while computing, storing and transmitting data).

Finally an array of objects travel at different velocities and finally all intersect at a specified event along with the Brown observer (similar to the above experiment).

Experiments could be conducted over and over again over a period of many years (although the distances and velocities do not have to be extreme--after all, experimenters have carried clocks on airplanes to verify time dilation).

If you give it some thought, you can probably come up with a better battery of experiments than I have proposed. I think you can see intuitively, without putting in specific numbers, that the outcome of these kinds of experiments would provide very strong evidence of 4-dimensional objects.

 

[bobc2]

By the way, it's obvious that we are susceptible to problems with semantics when we try to talk about time in the context of Block Universe. I've tried to avoid saying that Light Brown exists simultaneously at two different events on his world line. That language is self-contradictory in terms of normal usage of "simultaneous" in special relativity.

I noticed that Chestermiller, in his original post used a qualifier something like "in the 4D sense." I knew immediately what he meant but noticed some push-back from some here.

When referring to the block universe, Brian Greene uses language something like, "It is just all there at once." Right away he has given some physicists something to fuss about. Other physicists use similar language. I think it was Hermann Weyl who said something like, "...things don't happen--they just are." Maybe that is a little better than Greene. Einstein simply remarked something like, "...We physicists make no distinction between the past, present and future." And he remarked to Rudolf Carnap that he was "...very troubled by NOW." He indicated that NOW has no place in physics, and yet it is such a strong and compelling part of our experience. Paraphrasing Einstein somewhat: "Time is a stubborn persistent illusion." Reading Stephen Hawking's book by that title I anxiously anticipated Hawking's discussion of "Block Time" only to discover I could not find one reference to Einstein's comment anywhere in the book (what a bait and switch!).

Perhaps someone here can suggest some terminology we could adapt so that we all know what we are talking about. One physicist has published a paper about why so many physicists don't accept the block universe concept. He claims it is because there are two different kinds of time being used. So he recommends the time of physics be called "pime" and the other time just "time." I don't like his idea at all. And I don't accept his premise.

I think the real problem is that physics does not yet understand time at the most fundamental level. The logical positivists and operationalists offer the solution that you only talk about time measurements using clocks, etc. But that seems to fall short when attempting an understanding of the block universe.

 

[PeterDonis]

Wait a minute--you've just left out the most important part: Brown and Blue share the same simultaneous 3-D space at an event where each one occupies a different 3-D cross-section of the 4-D universe.

As it stands, this is nonsense. If Brown and Blue are in relative motion (which as I understand it, they are), they can't possibly "share the same simultaneous 3-D space" at any event. Each one, as you say, "occupies a different 3-D cross section of the 4-D universe"--the "3-D cross section" *is* the "simultaneous 3-D space". So you are contradicting yourself here, unless you mean these standard terms in some other way (in which case you should define how you're using them).

Further, Brown's simultaneous space includes one 3-D cross-section of the 4-dimensional Light Brown body, and Blue's simultaneous space includes a different 3-D cross-section of the 4-dimensional Light Brown.

Yes. But this doesn't mean what you think it means. See below.

I take it from the way you stated this that you at least acknowledge that we have established that Light Brown, as a minimum, has been shown to exist at two events along his world line, one being simultaneous with Brown and the other being simultaneous with Blue while Brown and Blue share their intersection event.

No. Read my post again, carefully. I said that Brown and Blue can each vouch for the "existence" of events on Light Brown's worldline *from which they have received light signals*. Those events are *not* events in their "simultaneous spaces"; they are events in their *past light cones*.

The "simultaneous spaces" are not "real" (at least, not "yet"--see below). They are *constructed* from the data that is known, the data in Brown and Blue's past light cones. But, because Brown and Blue do not have complete information about *all* of the initial conditions (only those in their past light cones), each of their *constructions* of what is in their "simultaneous spaces" at a given moment of their time are not *guaranteed to be right*. The constructions are only verified (if indeed they turn out to be right) *later*, when light signals from those events reach Brown and Blue at later points on their worldlines--but then, of course, there are *new* "simultaneous spaces" that have to be constructed, and whose constructions are not guaranteed to be right.

This is the basic flaw in your claim that *all* of the 4-D "block universe" has to "exist" all at once: *we don't have the necessary data* to establish it. We only have data from our past light cone. The rest of the "block universe" is *constructed* from that, but because we have incomplete knowledge, that construction may be wrong. In a thought experiment scenario, we can ignore this because we are making up the scenario: we can simply *stipulate*, by fiat, what the events are. In the real world, we can't do that. And no matter how many experiments we run, we will still only have incomplete data; we will *never* be able to *know* for sure what is happening in regions of spacetime that are spacelike-separated from us. Your strong claim about the "block universe" would require us to be sure, and we aren't.

 

[PeterDonis]

When referring to the block universe, Brian Greene uses language something like, "It is just all there at once." Other physicists use similar language. Perhaps someone here can suggest some terminology we could adapt so that we all know what we are talking about.

This language is fine when referring to the block universe as a *model*. Where it goes wrong is in trying to claim that the block universe must describe "reality", when our actual knowledge in the real world (as opposed to the model world of a thought experiment) is limited.

I think the real problem is that physics does not yet understand time at the most fundamental level. The logical positivists and operationalists offer the solution that you only talk about time measurements using clocks, etc. But that seems to fall short when attempting an understanding of the block universe.

It may well be true that we don't have a good fundamental physical understanding of time. But that's irrelevant to the "block universe" as a model. The block universe model is very simple: "time" is one of the four dimensions, and it's distinguished from the spatial dimensions (roughly speaking) by having an opposite sign in the metric. Once again, there's nothing wrong with this conceptually, as a *model*; but to claim that it must describe "reality" requires one to believe that we can somehow have complete knowledge of initial conditions, which we don't. Including our lack of knowledge in our model of reality complicates the model; it is no longer the simple "block universe" we have been talking about, but something more complex. (And including quantum mechanics adds further complications, as does including gravity.)

 

[Dale]

If the thought experiment outcome does not contradict LET, that just means that LET also requires 4-dimensional objects.

No, LET uses a model with a 3D reality which evolves over time, where time is the time in the aether frame. The worldline of any point particle can be written as a parameterized 1D object in a 4D space (t(\tau),x(\tau),y(\tau),z(\tau))\in \mathbb{R^4} or as a 0D object in a 3D space which evolves over time (x,y,z)\in \mathbb{R^3}(t). There is no way to distinguish the two experimentally.

 

[Dale]

I take it from the way you stated this that you at least acknowledge that we have established that Light Brown, as a minimum, has been shown to exist at two events along his world line, one being simultaneous with Brown and the other being simultaneous with Blue while Brown and Blue share their intersection event.

No, Light Brown has been shown to have existed at two past events. This does not imply anything about his current or continuing state of existence. The data is perfectly consistent with a 3D world which evolves over time.

Although you are correct that it is hard to explain the block universe concept in ordinary language (which is why it is best to use mathematical notation as above) it is not hard to explain the evolving 3D universe concept in ordinary language and see that it is also consistent with the data.

 

[Chestermiller]

The problem isn't that the experiment produces a negative result, the problem is that any alternative Lorentz-compatible model will also predict a positive result. For instance, LET would also predict a positive result.

This seems to be a key point that DaleSpam has raised. I would like to paraphrase it to test my understanding of what he is saying: The Block Universe model was originally developed as a way of translating the mathematical language of the Lorentz Transformation into a verbally articulated mechanistic physical model that could possibly represent physical reality (and that, possibly, people could more easily relate to). As such, it automatically and flawlessly must agree with every conceivable prediction that can be obtained from the Lorentz Transformation (including the thought experiments described by bobc2). However, back in the day, another verbally articulated mechanistic physical model, the LET model, was also developed, and it too is totally consistent with all possible predictions from the Lorentz Transformation. The verbally articulated descriptions for the Block Universe model and the LET model are very different from one another mechanistically, the former being a 4D geometric model, and the latter being an exclusively 3D description. Unfortunately, any thought experiments that agree with the Lorentz Transformation can not be used as a method of distinguishing which, if either of the two descriptions, provides a better representation of physical reality. There may be other equally valid mechanistic equivalents of the Lorentz Transformation that would also be in the running.
From this, I think it follows that, if mechanistic models such as these are to be tested to determine which if any are better representations of physical reality, we must look to experiments beyond the realm of SR, such as those which require application of GR; even there it might be very difficult to provide resolution.

 

[Dale]

I would like to paraphrase it to test my understanding of what he is saying: The Block Universe model was originally developed as a way of translating the mathematical language of the Lorentz Transformation into a verbally articulated mechanistic physical model that could possibly represent physical reality (and that, possibly, people could more easily relate to). As such, it automatically and flawlessly must agree with every conceivable prediction that can be obtained from the Lorentz Transformation (including the thought experiments described by bobc2). However, back in the day, another verbally articulated mechanistic physical model, the LET model, was also developed, and it too is totally consistent with all possible predictions from the Lorentz Transformation. The verbally articulated descriptions for the Block Universe model and the LET model are very different from one another mechanistically, the former being a 4D geometric model, and the latter being an exclusively 3D description. Unfortunately, any thought experiments that agree with the Lorentz Transformation can not be used as a method of distinguishing which, if either of the two descriptions, provides a better representation of physical reality. There may be other equally valid mechanistic equivalents of the Lorentz Transformation that would also be in the running.

Sounds right to me.

 

[bobc2]

Chestermiller, I didn't intend to take over your thread. There seemed to be two questions in your mind about the block universe: 1) What is it understood to represent in the physics community (and is your understanding of the concept in agreement with this)? and 2) What are the implications of the concept?

I tried to present the concept for you and indicate the motivation and validation of the concept. Since I've already dominated more than my share of the thread, I'll leave it to others to respond to your second question.

I think at this point you have enough of my views and the opposing views to draw your own conclusions about the validity of the concept. I'll just provide you a summary of the views I've expressed, presenting again the earlier sketches (which, by the way, are not at all original with me). The thrust of my presentations is that special relativity requires a universe populated by 4-dimensional objects, all of which co-exist in block time.

 

[Dale]

The thrust of my presentations is that special relativity requires a universe populated by 4-dimensional objects, all of which co-exist in block time.

If you would change "requires" to "permits" or "suggests" or something similar then I would agree. As it is, I think it is pretty clear that "requires" is too strong.

 

[harrylin]

The problem isn't that the experiment produces a negative result, the problem is that any alternative Lorentz-compatible model will also predict a positive result. For instance, LET would also predict a positive result.

In order for an experiment to qualify as evidence for theory A over theory B then not only does it need to be in accordance with theory A but it must also be in contradiction to theory B. That is what yuiop was mentioning:

Yes, and we have discussed that exact same topic not long ago.
- https://www.physicsforums.com/showthread.php?p=3558212 #27

Now, as different models claim to be consistent with SR (and all those interpretations are very hard or impossible to disprove), we call it "philosophy". Nevertheless, it's not the "empty" kind of philosophy that most of us don't appreciate that much, but philosophy of physics (in that sense I somewhat agree with both Ben and Bobc2). And if physics students don't learn it -just as my physics books omitted it- then they may be confronted with conceptual problems later on.

Harald

PS: Bob2c, I am again flabbergasted by your presentation today, in view of our earlier discussion in which you commented:
"I have tried and tried for many years to find material that effectively counters it, without success. I've tried to think up scenarios without success. I can't counter the argument for the block universe, but at the same time I just don't see how we can reconcile it when you consider the bizarre implications."
Upon that several of us presented alternative views; you may adhere to that view that you say you don't like, but there is no need for it.

 

[Dale]

I agree, and I think that it is beneficial to learn as many different interpretations as possible. I hope bobc2 continues to discuss the block universe interpretation and explain it to interested people.

 

[harrylin]

[..] Unfortunately, any thought experiments that agree with the Lorentz Transformation can not be used as a method of distinguishing which, if either of the two descriptions, provides a better representation of physical reality. There may be other equally valid mechanistic equivalents of the Lorentz Transformation that would also be in the running.
From this, I think it follows that, if mechanistic models such as these are to be tested to determine which if any are better representations of physical reality, we must look to experiments beyond the realm of SR, such as those which require application of GR; even there it might be very difficult to provide resolution.

Yes, the main contender of today is, I think, the one thought up by Bell (search for Bell Theorem, I also started a new topic on it in the QM group). Bell favoured the "older" interpretation and thought to have found a proof for that in QM. However, while I also think that the older interpretation makes more sense, his solution doesn't make much sense to me - it's as Einstein called it, a "spooky" solution and I'm not (yet) convinced that his theorem is faultless for sure.

 

[bobc2]

I agree, and I think that it is beneficial to learn as many different interpretations as possible. I hope bobc2 continues to discuss the block universe interpretation and explain it to interested people.

Thanks, DaleSpam. You always play fair.

 

[bobc2]

...PS: Bob2c, I am again flabbergasted by your presentation today, in view of our earlier discussion in which you commented:
"I have tried and tried for many years to find material that effectively counters it, without success. I've tried to think up scenarios without success. I can't counter the argument for the block universe, but at the same time I just don't see how we can reconcile it when you consider the bizarre implications."
Upon that several of us presented alternative views; you may adhere to that view that you say you don't like, but there is no need for it.

You may have missed a couple of the posts where I commented about caution--that physics does not yet have a complete understanding of time and certainly not consciousness.

But you are right. I have reservations and am mostly puzzled by the mystery presented to us by special relativity. I think its mystery is equal to that of QM. On the one hand we have the compelling concept of the block universe, while our deepest instincts and experience react against that concept (our "...stubbornly persistent illusion"). And along with the stubbornly persistent illusion are troubling implications of the block model, such as the zombies and threat of solipsism.

At the same time when it is time to present the block universe concept, I try to give it my best shot, although in the final analysis I don't really know the answer. But, what I personally believe is not that relevant--I'm certainly not an authority in this area, so I would rather present the views of physicists who have established reputations.

 

[harrylin]

[..] I have reservations and am mostly puzzled by the mystery presented to us by special relativity. I think its mystery is equal to that of QM. On the one hand we have the compelling concept of the block universe, while our deepest instincts and experience react against that concept (our "...stubbornly persistent illusion"). And along with the stubbornly persistent illusion are troubling implications of the block model, such as the zombies and threat of solipsism.

At the same time when it is time to present the block universe concept, I try to give it my best shot, although in the final analysis I don't really know the answer. But, what I personally believe is not that relevant--I'm certainly not an authority in this area, so I would rather present the views of physicists who have established reputations.

That's fine, but why do you present it in a biased way, as if it is proven to be the "correct" view? In fact, SR doesn't require "the reality of the 4-dimensional bodies" (post #24). Are you just playing "the Devil's advocate" perhaps?

My approach is very different from yours: if I am first presented with an explanation that doesn't make much sense to me, and after more reflection, for some subtle reasons appears to be simply wrong; and later another one that looks less appealing but which makes perfect sense, then I'm happy to have a way to understand it. And I offer it to whoever wants it, but without pushing it. And I hope one day to similarly understand QM - in a way that makes sense to me.
So, it's a bit funny - almost paradoxical - to see you pushing a model that you find puzzling, and me not pushing a model that makes perfect sense to me.

 

[Chestermiller]

Chestermiller, I didn't intend to take over your thread. There seemed to be two questions in your mind about the block universe: 1) What is it understood to represent in the physics community (and is your understanding of the concept in agreement with this)? and 2) What are the implications of the concept?
Since I've already dominated more than my share of the thread, I'll leave it to others to respond to your second question.

Thanks bobc2. I have found your discussions in this thread very educational, and they have helped me get a much better understanding of the Block Universe model. Thanks also for your courteous and respectful responses.
As you mentioned, in my original posting, I offered some extended interpretations which seem to be fully consistent with the Block Universe material that you presented. These interpretations are totally new (I think), within the framework of Block Universe, and I was hoping that some PF respondents would be willing to comment on them. Looking forward to hearing from some of you.

Chet

 

[bobc2]

That's fine, but why do you present it in a biased way, as if it is proven to be the "correct" view? In fact, SR doesn't require "the reality of the 4-dimensional bodies" (post #24). Are you just playing "the Devil's advocate" perhaps?

I'm not sure really. Aside from trying very hard to provide a good representation of the block concept, it's probably that I'm so conflicted about it. When in the process of really focusing on just the logic of the concept it kind of takes over my thought process. I get so convinced of the logic that I presented in the summary post, I'm probably really believing it at that point. Then, after pulling away and thinking about some of the bizarre implications I get quite a bit more subjective in the analysis. You might say that on an objective basis I can't find a way to refute the logic of block universe, yet, on a subjective basis I reject it. I don't know if that makes any sense, but I can understand your puzzlement over some of my posts.

 

[bobc2]

Chestermiller, I didn't intend to take over your thread. There seemed to be two questions in your mind about the block universe: 1) What is it understood to represent in the physics community (and is your understanding of the concept in agreement with this)? and 2) What are the implications of the concept?
Since I've already dominated more than my share of the thread, I'll leave it to others to respond to your second question.

Thanks bobc2. I have found your discussions in this thread very educational, and they have helped me get a much better understanding of the Block Universe model. Thanks also for your courteous and respectful responses.
As you mentioned, in my original posting, I offered some extended interpretations which seem to be fully consistent with the Block Universe material that you presented. These interpretations are totally new (I think), within the framework of Block Universe, and I was hoping that some PF respondents would be willing to comment on them. Looking forward to hearing from some of you.

Chet

Thanks for your consideration (and endurance through the extended posts). I hope you will get some more feedback on the ideas you've presented--and perhaps some comments on some of the implications of the block concept.

 

[harrylin]

[..] When in the process of really focusing on just the logic of the concept it kind of takes over my thought process. I get so convinced of the logic that I presented in the summary post, I'm probably really believing it at that point. [..]

OK, that explains it - thanks for the clarification!
And surprisingly not many people here take the time to defend the Block Universe concept, so I think that your elaborations are very useful.

 

[Vandam]

OK, that explains it - thanks for the clarification!
And surprisingly not many people here take the time to defend the Block Universe concept, so I think that your elaborations are very useful.

People who accept the real significance of "relativity of simultaneity" know that Block Universe is a fact.

 

[nitsuj]

People who accept the real significance of "relativity of simultaneity" know that Block Universe is a fact.

Hmmm, I don't. Perhaps I don't know RoS, or at least the real significance.

Block universe a fact? A fact of what? and according to what/whos measure of time?

 

[harrylin]

Hmmm, I don't. Perhaps I don't know RoS, or at least the real significance.

Block universe a fact? A fact of what? and according to what/whos measure of time?

I second that - IMHO, the real significance of RoS depends on one's interpretation, so that such an argument is bound to involve circular reasoning.

And there is a follow-up thread (also still open) with more discussion on the sub-topic of RoS as supposed evidence for the Block Universe, based on Paul Davies claims:

https://www.physicsforums.com/showthread.php?t=595021

 

[Dale]

People who accept the real significance of "relativity of simultaneity" know that Block Universe is a fact.

There is no experiment which can be performed to distinguish the block universe interpretation of SR from other interpretations of SR. So, no, it is not a fact, even given the relativity of simultaneity. The block universe happens to be my preferred interpretation, but I am not deluded enough to call it a fact.

 

[nitsuj]

The block universe happens to be my prefered interpretation,

and then it was and lastly but then :zzz: 'cause this ground has been covered many times.

I wouldn't have guessed you to prefer an Eternalism interpretation of time.

 

[Dale]

and then it was and lastly but then :zzz: 'cause this ground has been covered many times.

I wouldn't have guessed you to prefer an Eternalism interpretation of time.

Sorry to cause such distress!

I probably should mention that my preference is practical rather than philosophical. Specifically, I simply find it easier to correctly work most problems by using the block universe interpretation to organize my thinking than by using others. I don't particularly "believe in" any interpretation philosophically and so I shamelessly use other interpretations (even LET) whenever they suit the particular problem at hand.

 

[nitsuj]

Sorry to cause such distress!

I probably should mention that my preference is practical rather than philosophical. Specifically, I simply find it easier to correctly work most problems by using the block universe interpretation to organize my thinking than by using others. I don't particularly "believe in" any interpretation philosophically and so I shamelessly use other interpretations (even LET) whenever they suit the particular problem at hand.

Now that's a "Dalespam" response, thanks I feel better now!

 

[bobc2]

People who accept the real significance of "relativity of simultaneity" know that Block Universe is a fact.

Vandam, you are actually in pretty good company, embracing the Block Universe concept: Physicists and mathematicians like Einstein, Hermann Weyl, Kurt Godel, and many others. Einstein commented that General Relativity would not have got any father than its long clothes without Minkowski's 4-dimensional continuum of special relativity.

 

[PeterDonis]

Einstein commented that General Relativity would not have got any father than its long clothes without Minkowski's 4-dimensional continuum of special relativity.

I don't think Einstein was talking about the "block universe" concept in that quote, at least not as "block universe" is being used in this thread. "Block universe" is an *interpretation* of what 4-d spacetime, as it's used in SR and GR, means. Einstein was just talking about the theoretical usefulness of 4-d spacetime, in particular how viewing it as a geometric object opened the door to letting that geometric object be dynamic instead of fixed, which led to GR. Einstein was not talking about any particular interpretation of what 4-d spacetime means.