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## Block Universe Implications

 Quote by bobc2 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.

 Quote by bobc2 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.)

Mentor
 Quote by bobc2 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.

Mentor
 Quote by bobc2 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.
 Recognitions: Gold Member [QUOTE=DaleSpam;3803243]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.

Mentor
 Quote by Chestermiller 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.
 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.

Mentor
 Quote by bobc2 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.

 Quote by DaleSpam 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.

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.
 Mentor 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.

[QUOTE=Chestermiller;3804649]
 Quote by DaleSpam [..] 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.

 Quote by DaleSpam 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.

 Quote by harrylin ...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.

 Quote by bobc2 [..] 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.