The Nature of the Wave Function by Edwin Eugene Klingman

Hello Georgina,

I'm sure Tegmark is an extremist only in some ways, not in every way. But saying that in some cases all sets of possibilities exist is extreme. It's tough for creatives, because whatever you might come up with, there's the worry that he thinks it exists already. But creatives can have fun thinking up absurd things, and then realising that Tegmark believes that exists - I've played this game with friends occasionally, though only in a loose way.

Anyway, I do think that our conceptual picture is simply incomplete, and instead of facing up to that, and trying to make progress within our existing way of doing physics, many are now messing around with the underlying principles, and trying to reset the whole playing field. I see that in quite a few of the essays here, but to me that's a bit desperate and a bit premature - we haven't finished exploring with our present system yet. There's a need to look carefully at the holes in the jigsaw, and see what we can work out about the missing pieces - that's what I've been trying to do anyway.

Best wishes, Jonathan

Jonathan, Edwin,

sometimes ideas that are expressed can be provocation intended to make people stop, take notice and think rather than a statement of conviction that this is how things are-definitely. Whether you or I like what Max Tegmark has said or not he makes people think about it.

My views on what a multiverse is and how they can be a part of reality have changed radically as a result of listening to what Max Tegmark has said in his papers and lectures. I've gone from saying its just mathematical nonsense to thinking it really is a good way of describing what we are dealing with, (if the multiverses are thought of in a particular way).

Now thinking about what an object is I have had to concede that it is all of its possibilities simultaneously and not just what one observer will perceive it to be from his perspective. I doubt I would have got to there without someone demonstrating that there are vastly greater possibilities than I was imagining.

Edwin,

I think he is being serious too and playful. Edward de Bono wrote :"Hypothesis, speculation and provocation allow us to play in our minds. We try out new things. We carry out the thought experiments that Einstein used to develop his powerful ideas." (1992). IMO Whether it is correct or not is not as important as breaking new ground, finding new ways of thinking about the problems.

Edward de Bono also wrote: "The analysis of data is not enough. We also need the creative ability to speculate and use provocative hypotheses. If we can develop these skills in scientists, science will advance more rapidly.The new hypothesis or provocative idea provides a scaffold on which to organise our information and with which to seek new information." (1992)

I'm not disagreeing with your judgement Edwin just expressing what I think. Max Tegmark knows what his intentions were and I'm not a mind reader. "Beauty is in the eye of the beholder." It would be a dull world if we all liked exactly the same things.

Dear Edwin:

I hope you don't mind, but I'm copying a comment that I just left on Johathan Kerr's topic over here because it draws on parts of this current discussion. Also, Edwin, Jonathan, and Georgina, thanks for the interesting and insightful discussion. Georgina, I really like those last Edward de Bono quotes.

Dear Jonathan:

I like your essay. I think you present an interesting analysis of a concept that is very muddled. In particular, I was glad to see you repeatedly bring up the problem with the supposed illusion of time in a block universe. You might like my favourite quotation from Milic Capek, which I think expresses this problem beautifully:

"We shall deal only briefly with an extremely serious epistemological difficulty which arises when time is deprived of an ontological status and reduced to a mere appearance. For in relegating time into the phenomenal world an intolerable dualism is created between the realm of appearances, occurring in time, and the realm of timeless noumena. All static systems from Parmenides to Bradley and McTaggert are plagued by the same problem: If true reality is timeless, *where does the illusion of succession come from?* If time has no genuine reality, why does it appear to be real?

"No solution can be found which would not introduce surreptitiously the reality of time *somewhere*. If the illusory reality of time is nothing but a gradual rising of the curtain of ignorance which separates our mind from the complete and timeless insight, then at least *this process of rising is still a process which unfolds itself gradually without being given at once*; but, by conceding this, we admit the reality of time either in our mind or *between* our mind and the allegedly timeless reality."

For it is this surreptitious element of "time" that enters into the description of a block universe that leads to the intolerable dualism that you've also discussed, which leads to all kinds of paradoxes in working with and interpreting the theory. As you've correctly noted, "in taking that view, the number of phenomena that must be demoted to unreal is large. It amounts to anything that could be called a *process*, and that includes a lot of our world."

But, for this reason, I also think that your description of a block universe doesn't get all the way down to the heart of the issue with it, although I'm certain you do know what that issue is. You described: "The universe is a motionless 4-dimensional block, with no moment called 'now' moving through it anywhere. Instead it has many events and equally important 'now' moments, all sitting alongside each other in a static spacetime grid. This unchanging object it is just *there*." But the thing is, that although we can't avoid the use of verbs in describing what a thing "is", every verb that is used in describing a block universe actually falsely represents it. It's a true dilemma, and I'm not saying anyone could describe a block universe better than you have, but I think that any description of a block universe, which will inevitably require words like "is", needs to be supplemented by saying something like "although we say that a block universe physically 'exists' in its absolute entirety, from the beginning to the end of all four dimensions of spacetime, 'existence' is clearly the wrong word to use in describing a block universe, because although it contains within it a timelike dimension, it no more 'exists' in a temporal sense than a block of wood that comes in and out of existence in an instant; it is temporally singular."

And this is really why any attempt to reconcile the illusion of time with the block universe, as in perdurantism, is a false-start. And it's also the biggest indication that the block universe theory has to be incorrect, because no matter how we try to avoid it, we do commonly get a sense of temporal existence that can't really be reconciled with that singular block. Since the requirement of a block universe can be deduced directly from special relativity theory, something must be wrong at the heart of the theory.

This is all very closely related to the problem that's at the heart of the essentially paradoxical notion of time travel, in which science fiction writers begin with the idea of things actually existing throughout spacetime, (sort of) as in a block universe, but then allow that the events in that "spacetime" are also able to change. Clearly, the notion of a physically existing spacetime that changes requires another temporal dimension---and this is where that surreptitious Newtonian concept of an absolute time comes in; i.e., because the changes that are thought to be able to occur within spacetime, due to a time traveller's influence, are also thought to simultaneously effect all of spacetime. If you could go back in time and kill your grandfather before he met your grandmother, then you never would have been born, so you clearly can't do that---a well-known paradox. But as I see it, my grandfather doesn't exist before he met my grandmother: the event is no longer real. What's real is my typing this right now, which will be past, and therefore unreal, when you come to read it.

Elsewhere on this blog, you've made comments that indicate to me that you think I haven't carefully thought this problem through, and that you think I've been too quick to suggest what I think lies at the heart of the problem with the relativistic implication of a block universe, when I say it is the problem that, along with the assumption that there can be no privileged observers, it is the interpretation that synchronous events, described by constant values of the time-coordinate in any frame, truly occur simultaneously according to observers who remain at rest in those frames---which is what leads directly to the *inference* "that an event can be both past and future in two different viewpoints". Or else, when I say that there must instead be an absolute (global) simultaneity-relation amongst *all* observers in a three-dimensional enduring (i.e., flowing) universe.

This is a difficult stance to argue for, which involves not only having to reconcile with the principle of relativity and the relativity of simultaneity, but also having to justify the need to forsake the principle that there can be no privileged observers (which seems to agree so well with both the principle of relativity and the Copernican viewpoint), and show that the scientific evidence does actually support this.

This is what I concentrated on accomplishing in my essay; but I assure you that I have subjected the problem of the nature of time to rigorous analysis, dedicating nearly eighty pages of my (184 page) thesis to an analysis of the historical, philosophical, epistemological, and physical factors associated with this great problem. Although it may appear that I have presented something that simply works (I can hope you at least saw it that way), I have by no means simply chosen, without a great deal of thought, to reload assumptions that were previously cast off with good (but I think imperfect) reason. This is my response to your remark that "In relativity I'm often suspicious of views in which the weirdness in the theory is removed by pointing out errors that everyone else failed to see for a century. Usually when physicists allow a theory to be weird for that long, it's because they couldn't go anywhere else, and not from lack of trying."

You also wrote to Edwin: "I felt that unlike many, you were grasping at an underlying reality by looking at the clues. That's what makes a paper of interest to me these days, if it's looking for ways forward for physics - it's not enough for it to be trying to rejig existing theory into something it wasn't before. Like you, in my essay I'm grasping at an underlying reality by looking at the clues, and the real clues are external things like observations, not internal things like elements of existing theory.

"To me, for an approach to be relevant in the present situation it also has to be open to there being bits of the jigsaw missing, that we haven't yet found. Many of the essays I've read have implied within them the idea that the pieces we have are enough to finish the puzzle, if we can only organise them in the correct way. And yet a careful look at the clues shows that this idea is unavoidably wrong - new conceptual elements are needed."

I agree with you here, except for the part where I fear you're considering me with the "many" who are unlike you. To use your analogy, if we think of physics as closing in on the completion of one area of a puzzle (say, just for instance, with about ten pieces left to put together), you know that without fitting the remaining loose pieces into the puzzle correctly you can only jam about half (say, five or six) of them in the remaining space. These few pieces are all connected at points, and touch on the completed part that surrounds them in a number of places, but the picture is obviously imperfect and sparse. However, the pieces that have not been carefully fit into their right places *can* be put there by taking a careful look at their shape; but this may require one or two of the other pieces that were set aside because they didn't fit when the first five or six were jammed in without enough care.

Just because I have, in my essay, attempted to take a piece of the puzzle that I think was out of place, and fit it into its correct spot, that should not be taken to indicate that the argument has implied within itself "the idea that the pieces we have are enough to finish the puzzle." To my notion, space-time is, by the definition I've given of an enduring three-dimensional universe, *not* real. It is a graduating map of the events that occur in the universe, which contains within it the effects of things that occurred in the (absolute; purely *ideal* or mental) past. Now, in general relativity, space-time is described as a four-dimensional physical field that is moulded by mass which in turn follows geodesics, so that there is a reciprocal interaction. "Space and time are now dynamic quantities: when a body moves, or a force acts, it affects the curvature of space and time---and in turn the structure of space-time affects the way in which bodies move and forces act. Space and time not only affect but are also affected by everything that happens in the universe."

In my opinion, this quotation from A Brief History of Time poses just as paradoxical a notion as the theory of time travel---which Hawking also considered realistic enough, according to standard relativity, that in 1992 he invented the chronology protection conjecture. For the idea is the same: four-dimensional space-time exists, and bodies dynamically move through it, shaping it moment-by-moment in their presence. Since it is in fact space-time that's warped in the presence of gravitational mass according to general relativity theory, then according to the cosmological interpretation of relativity that I've discussed in my essay, all that might actually be warped is the perception of that unreal coordinated map of events.

If we choose to postulate absolute time in place of the postulate of the absolute world (according to Minkowski, since the relativity-postulate "comes to mean that only the four-dimensional world in space and time is given by phenomena..., I prefer to call it the *postulate of the absolute world*"), at the sake of having to accept that there *is* a fundamental rest-frame in our Universe, as cosmology came to demand anyway, many of our previous notions will have to fall. But the empirical facts still have to remain the same, so it's true that we will still have to reconcile the physical theory---our interpretation of the mathematics---with the evidence. Therefore, this requires a certain amount of "re-jigging" in order to maintain consistency.

I hope you don't mind this long note: I've found both your essay and your comments to be thought provoking, and I had a lot that I wanted to say in response. I hope you've found my comments to be thoughtful, and that we can continue to have intelligent discussion if you've got anything to add or criticise in response. I think we do have a common goal in mind; therefore, for now, I'd like to leave you with a quotation from Bertrand Russell, which I included in my thesis as an epigraph to the chapter "Against Einstein's Relativity: A Doxographical Analysis":

"I cannot believe---and I say this with all the emphasis of which I am capable---that there can ever be any good excuse for refusing to face the evidence in favour of something unwelcome. It is not by delusion, however exalted, that mankind can prosper, but only by unswerving courage in the pursuit of truth."

Daryl

Dear Edwin:

Thanks very much for the opening, and the heartwarming comments about my essay. I haven't voted on any essays yet either, but yours must be amongst the finalists in my opinion.

Your question about how "some observers will see an event while the same event will lie in anothers 'future'" can be understood by referring to Figure 2 in my essay. Draw two past 45-degree null-lines extending from A in either direction in both frames, but ending at some "past event of photon emission" that's above B's x'-axis. In both frames, those null-lines describe the paths of photons that "will be emitted in B's 'future'", that are presently being observed by A, since the present is, by definition, A's x-axis. This funny result has only to do with the requirement that light has to travel at the same rate in either direction in the proper coordinate system of any inertial observer, and can therefore be understood without also considering the hyperbolic scaling between local coordinate frames that's associated with the Lorentz transformation. The latter is of course necessary to ensure that the speed of light is the *same magnitude* in all frames, and it's important for time-dilation and length-contraction.

The crucial thing to understand is that, along with any one event, it is possible to define an absolute set of other space-time events that occurred simultaneously with it in the three-dimensional universe. Therefore, although the event at which A observes these photons may in one sense be said to lie in B's "future", that's actually false by definition, since simultaneous events all lie along x. This agrees with the "man on the street's" Newtonian intuition about the passage of time: all inertial observers may well consider themselves as being at rest in a three-dimensional universe that exists now---where "now" refers to ever-flowing present space. However, there's a catch: since we're saying that B is *really* moving through the universe, two photons incident on B at one event, coming from either direction, which were emitted at *truly simultaneous* events, will not have synchronous emission times in B's proper coordinate system: the photon that B was effectively "running away from" will have a later emission time, while the one that B was "racing towards" will have an earlier emission time. However, this has to be the case if B is to describe light as moving at the same speed in either direction, since the relative absolute distance covered by the former photon will be less than that of the latter. In contrast, two events that are described as synchronous in B's frame won't actually have occurred simultaneously.

This is why A is called a privileged observer, because synchronous events in A's frame really do occur simultaneously, due to the fact that A has zero absolute motion. But as I've argued in my essay, this aspect of the theory should not actually be at odds with intuition. Putnam's argument hinges on the principle that there can be no privileged inertial observers because any one is as well suited to the position that they "now" exist in a three-dimensional universe; therefore, because everyone has different "nows", and none of them should be special, all "nows" integrate to form a block. However, as I've said in my essay, the "now" doesn't have to be the time that's read on anyone's watch, since there's no intuitive reason to require that anyone's proper time coordinate is orthogonal to space "now"---we don't have a sense of flowing an a direction orthogonal to space, but of space *existing*. Therefore, "now" can be one and the same enduring space for all observers.

I'd sure like to be able to talk with you sometime about whether logic, math, and the emergent physical universe that we observe are parts of a puzzle to be completed.

Best regards,

Daryl

I thought I might add, because the statements I made above, about events that are really simultaneous not being perceived as synchronous in B's frame, may sound a bit mysterious,---that this is demonstrated in my essay by the fact that observers B and C' are totally causally disconnected, so what B describes as synchronous with the event illustrated by the red dot in Figure 2 is not the blue dot, where C' is "simultaneously in its own separate universe", but C (the yellow dot) at a *later* absolute time---i.e., when it gets to the blue dot as the universe (x-axis) evolves. C could emit a photon towards B at that (cosmic) time, which would travel through the one-dimensional "universe" evolving in absolute time, until it's observed by B; and B would infer that that event, which *really* occurred at a later cosmic time, was synchronous with the event that's illustrated by the red dot.

The thing is, that relativity theory doesn't tell us a priori the location of an observer along its worldline that coincides with the emission of a distant photon, nor the location of the emitter along its worldline that coincides with the later event when the photon is observed: all it describes is the space-time separation between any two events. We are left to infer the rest for ourselves, and the common practice is infer that such coincident (i.e., simultaneous) events in space-time occur at the same "time" in any frame---i.e., synchronously. This is what leads to Rietdijk-Putnam-type deductions that there has to be a block universe. But then those who want to deny this inference, often appeal to the fact that the theory can't really tell us a priori which sets of events were *actually* coincident---and claim, e.g., that the observer could really have been anywhere along its worldline in the region outside the light cone associated with the emission event, in the region known as "absolute elsewhere", thus denying the existence of an objective reality.

Many problems arise as a result of this inconsistency of thought, because when not backed into the corner of the block universe implication, everyone does commonly assume that synchronous events really are simultaneous in any frame, even in general relativistic solutions. And that's where the really new pieces of the puzzle come in when we do make the assumptions of absolute space and time that are consistent with the theory.

Hello all,

Thank you Daryl for your kind and interesting comments on my essay, also the same to Edwin. Daryl, I wasn't referring to your essay before, having only flipped through it until just now. I think it's very good, and unlike many of these essays, I agree with you about some things.

I don't see the linguistic thing you mention as a problem with block time, it might be a slightly different use of the word 'is', but to me the question of whether or not we have the language to describe it doesn't affect the question of whether block time is true or false.

I don't agree with a universal present moment - I think the concept of simultaneity at a large distance is always questionable. In Newtonian time it has some meaning, in Einstein's version it has less. I think it has even less than that - no meaning beyond the light cone. The reason is that in the universe we have different time rates locally. Relating them clearly doesn't work in different frames, as I mentioned in the essay. They're thought to be relatable in the same frame, but we can't easily check that.

Two clocks a million light years apart and not moving in relation to each other might keep the same time and run in sync. But that doesn't prove simultaneity. It just proves that two local time rates at a distance are in step with each other. To me relating the times of events with meaning is saying that an event is before another one if it can affect it by getting a light signal there in time to influence it. That means within the light cone, at short range.

This would explain why block time is wrong - what led to it depends on long-range simultaneity having enough active meaning to allow an event to be in the past to one observer but in the future to another. Without that, there's no block time, and a lot of the confusion about time goes away. Hope this makes sense...

best wishes, Jonathan

I have read a conversation with Julian Barbour in which he says motion through time must be caused by some sort of psychological illusion. To me that approach fails in trying to interpret gravitational time dilation, and tends to need a second illusion, interacting with the first one, when interpreting motion time dilation. Two interacting illusions does not make for a good explanation.

It is also denying the problem, and rather like marking the unexplored areas on a map with 'here be illusions' (just as the old map makers marked unexplored areas with 'here be dragons'). Barbour says time is 'nothing dressed up in clothes', like the emperor's new clothes. He's looking at it mathematically, but it's a conceptual problem - initially anyway.

To me the thing that is like the emperor's new clothes is the fact that the illusion approach dismisses the laws of physics, and hence physics itself and much of our world, as an illusion. Some people have simply pretended not to see the problems with block time, because like the emperor's new clothes, it has been the standard view, to be accepted. Only recently have we been questioning it, because we need to if we are to get to quantum gravity.

Best wishes, Jonathan

Hi Jonathan and Edwin:

The local reconciliation of temporal passage that's supposed to come from denying a metrical relation between events that exist outside one's past light cone is Howard Stein's thing. However, as Craig Callender pointed out in "Shedding Light on Time", by positing that "at least one event in the universe shares its present with another event's present", which he considers to be "the thinnest requirement one could put on becoming", "Stein's 'possibility' theorem [is transformed] into a 'no go' theorem for objective becoming in a Minkowski spacetime". Basically, what this means is that if we can say that *even just one event* exists at some metrical distance outside the light cone of another event---like, for instance, the emission of a photon by the Sun anytime in the past or future eight minutes---Stein's theorem tells us that the common way of describing what is "present" in relativity theory demands a block universe.

I believe in the existence of Physical Reality, despite the fact that I can't know what simultaneity-relation describes the sapcelike surface that exists at any instant as I'm looking at my watch, because every experience I've ever had in my life tells me it's there. Therefore, although we can't scientifically prove or disprove its existence, I think a pure verificationist way of looking at things is the wrong approach. It doesn't lead to any clear understanding of things, but only allows some people the opportunity to wave their hands or shrug their shoulders.

Therefore, given Stein's theorem, and the fact that I believe the Sun exists now---as in, I believe there's a well-defined spacelike metrical distance between the Sun and me now, which has a different length (and, e.g., isn't synchronous) in different coordinate frames---even though I won't see what it looks like now for another eight minutes---I completely agree with Roger Penrose's remark, when demonstrating his own version of the Rietdijk-Putnam argument in The Emperor's New Mind, where he notes that whether one uses observers' light cones or their simultaneous spaces makes no difference at all to the conclusions. ("Some relativity 'purists' might prefer to use the observers' light cones, rather than their simultaneous spaces. However, this makes no difference at all to the conclusions.")

As to denying the relevance of coordinating distant spacelike events with a metric, that is not something that should be done lightly, and I think it just leads down a rabbit hole. All of science is based on the use of a metric---rather than a more general abstract topological space---to describe "distances" between two events, and there's a mountain of scientific evidence to support the fact that, regardless of which coordinate system is used, there is a Lorentzian metrical relation amongst all space-time events. This is the very reason why proper times are measured differently by observers in relative motion, and there is indeed a well-defined metrical relation between them according to relativity theory. Therefore, in relation to my above remarks, I think it's just wrong to argue that this metrical relation should somehow only crystallise when events enter one's past light cone, which is what I can only take your comments to mean.

I've already noted elsewhere on this blog a very relevant observation that Tom Ray made in his essay: 'One recalls that prior to Descartes, all geometry was done with compass and straightedge---all "here" and no "there." Only with the development of analytical geometry were we able to identify relations between numerically distant points and a local coordinate system.' I don't understand why you would *want* to reject this. I agree that it seems to be hard to reconcile it with relativity without concluding that there has to be a block universe; but if you'd rather accept instead that it does work---and I'm certain that it does---I think you'd see that the interpretation of the emergence of relativistic space-time that I've described in my essay really works. The key assumption is that the metrical relation amongst events in space-time has to be Minkowskian, just as it is in the block universe theory.

The linguistic thing is essential to forming a clear understanding of the problem, and how the theory works; and there are in fact important distinctions that need to be made between the meanings of *two* words in order to understand how special relativity can be reconciled with a flowing present. First and foremost is the copular verb: as Steven Savitt argues (see the top paper) it's really through a carelessness with the word "is" that McTaggart was able to show, even from a Newtonian perspective, that the past, present, and future are all equally real. According to presentism (which McTaggart tried to argue against), the past and the future do not "exist" in the same sense as the present, which is all that's supposed to be real. Instead, the past and future exist, according to the presentist viewpoint, *ideally*---i.e., brains, photons, computers, books, etc., existing in the present, carry, or form ideas about what was in the past or will be in the future. This is an extremely important distinction to make, because confusion does arise when one thinks of the real present as somehow flowing through the space-time continuum of events, with any particular event in the future existing as such until it eventually becomes present, then past---even if we're thinking of this sense of "existence" as something abstract---and it's only amidst such confusion that arguments like McTaggart's (or, e.g., those of Huw Price) prevail.

But when one thinks of the present as enduring, with the ideal past emerging in its wake, as an unreal thing about which records exist in the present, and the ideal future as something that's anticipated in the present, there's no reason to think of McTaggart's argument as anything more than a misuse of semantics. As I noted before, it's also this way of thinking of all events throughout (space-)time as existing in some way that can be travelled to, that leads people to time travel paradoxes.

This presentist thinking makes perfect sense from a Newtonian viewpoint. But relativity throws in another monkey wrench, because what is meant by "time" is---at least in one sense---not universal. Two events that occur at the same "time" according to one observer will happen at different "times" for another observer, and clocks will tick at different rates. For such reasons, it's difficult to see how it could be possible to reconcile a view that everything only exists "now" with relativity theory. The way to do this, I've argued, is to first make note of the distinction between space-time, as a four-dimensional *ideality*, and an enduring three-dimensional *reality*---a flowing Heraclitean present, with an absolute time defining an absolute simultaneity-relation, and associated sets of events that *truly* occur simultaneously, in a Newtonian sense. These events obvously then have to be said to occur at the same "time"; however, as described in different relativistic space-time coordinate systems, viz. those used by observers with non-zero absolute motion, the events that occur at the same "time", in the pre-defined sense of simultaneity, will not occur at constant values of the time-coordinate.

Therefore, along with the distinction that I think needs to be made between the "existence" of "ideal" past and future and a "real" present, I think it's also very important to make a distinction between events described as "synchronous" in a given frame occurring at the same "time", and events that truly occur "simultaneously", at the same cosmic "time".

Best,

Daryl

Jonathan:

I typed up my previous comment before seeing this one, so I added it there. I agree with what you're saying here about people pretending not to see the problems associated with a block universe, and chalking things up to illusions. I think this happens because people don't want to change the basic way they think about the theory. The problem with that, I believe, is that the basic way people like to think about the theory---as dynamical---is demonstrably incompatible with what the physical theory has to say about the way they like to think about the theory.

Daryl

Hello Daryl,

in reply to your last two posts, I agree with the latest one, that people don't want to change the way they take SR.

They take SR with spacetime, and yet spacetime may be entirely wrong. It is impossible for anything to move through spacetime, almost by definition. Spacetime distances include imaginary numbers, which people accept in an 'emperor's new clothes' kind of way. But this may have no physical meaning. And, for instance, an event 4 minutes ago on Mars has zero separation in spacetime from right now where you are on Earth. All this may have no physical meaning. And because it leads to block time which requires illusions, spacetime is very questionable.

Spacetime hasn't been tested, and like string theory, it can't be tested. Suppose it's entirely wrong - imagine sweeping it away. We'd be looking for missing pieces of the puzzle in a new landscape. Much of our present conjecture would be irrelevant.

You talk about relating things in space, but the issue is, can we relate things in time? That's what we don't know - we know a lot more about space. We have reason to think we can't relate things in time as we have been doing, because look where it led - it led to block time, which doesn't work with the real world we observe. So time may be different. It may be meaningless to relate points in time at all. We don't know. All out attempts to relate points in time may have failed to work. But within the light cone, light signals give us an alternative method, meaningful, but perhaps just a crude approximation, perhaps also ultimately irrelevant to the way time really is.

Best wishes, Jonathan

Dear Edwin,

You invited me to take part in your discussion. I have to apologize for not reading all contributions. Instead of referring to the weak points in Daryl's view, I just added to my essay a hopefully unmistakable explanation why SR is based on confusion between physical reality and what an observer measures.

"Two events that occur at the same time according to one observer will happen at different times for another observer, ..."

Do they really happen for observers or do they happen at the location where they happen?

Let me tell a story that happened 50 years ago. In a rowing race over 2000 m in about 6 minutes, my crew was defeated by only as little as 0.02 seconds precisely measured with a Swiss Longines system. This was undeniably close to physical reality. Merely at start, we were a bit cheated because the acoustic signal reached us about 0.1 second later than the winning boat.

Best,

Eckard

Dear Eckard,

This perfectly demonstrates the point I've been making about problems that arise due to sloppiness with language. You wrote, "Do they really happen for observers or do they happen at the location where they happen?" Well said. The word "for" in the quotation you gave is meant in the sense of "according to" or "as determined by" or "in the proper coordinate system of", and therefore not in the sense of a gift. Events in space-time are locations or points on the four-dimensional map. What's meant in that quotation is simply that two events at the same value of the time-coordinate of one system will be at different values of the time-coordinate of another system.

Since you've claimed that there are weak parts in my view, I'd very much appreciate those being pointed out so that I might have the opportunity to argue otherwise. I'd consider it a courtesy. I'll even briefly recap my position for that purpose.

The past, present, and future don't all "exist" in the same sense: the past and future "are" purely ideal (ideel in German; i.e., not real anywhere but in *present* brains, computers, etc.) and the three-dimensional enduring present "is" real. Relativity adds another layer, complicating this picture further, because it comes to mean that together with the dual meaning of the copular verb "is" in relation to the dimension of time, there must also be a dual meaning of the word "time" if the theory should be reconciled with a Heraclitean flowing present. Thus, the common-sense impression of "time" that we have when we consider present "existence" in three-dimensional space---which is what we refer to when we say two events occur "simultaneously"---must be separated from the sense of "time" that's described by any space-time coordinate system. This is precisely because any claim that two events occur at the same "time" in the latter sense cannot be universal, since any change of coordinates describes one event as preceding the other; i.e., "synchronicity" is relative.

This latter fact has commonly been taken to imply that relativity is inconsistent with presentism, because "synchronous" and "simultaneous" are thought to be synonymous; but I've shown in my essay the mathematical theory can be consistently reconciled with the above view of time, as long as we make the appropriate split between the meanings of the two words and define a global simultaneity-relation. Therefore, relativity does not require a block universe.

Daryl

Dear Jonathan:

It *is* impossible for anything to move through spacetime by definition. I think the quotation by Geroch that I gave in my essay says that the best. Although the one by Weyl comes a close second. It's just that some people mis-construe that due to an inability to break away from the sense that things really change.

If you're interested, I can prove to you that spacetime distances don't include imaginary numbers in de Sitter space. It's not a hard or long proof, and it's done from first principles. But it requires a positive cosmological constant.

Zero distance between two points that are not identical is indeed a peculiar property of Lorentzian metrics. They're weird. But that doesn't mean we should deny the appropriateness of the Lorentzian metrical structure that's used to describe physical reality. That has been very successful, not even just locally, but also for describing cosmological data. Without the assumption of the RW metric to describe an emergent three-dimensional universe, how might you consistently relate all the cosmological observations?

Best,

Daryl