The block universe is interesting, but not comforting

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This SMBC gets at something that’s often bothered me about the way many people talk about the block universe concept. The block universe is the idea that if the universe is fully deterministic, then its entire history from beginning to end exists in an eternal timeless static block. We are patterns embedded in the block, and so from our perspective, we exist in a dynamic and changing reality. But from outside, the block is like a movie DVD, a static object containing a story, with the beginning, middle, and end already set.

Often it’s described by saying that all of the past events in the universe, including all the people who’ve ever lived, are “still out there right now.” In other words, Julius Caesar, the Buddha, Gandhi, and our deceased relatives are still living their lives “right now.” Likewise, we’re often told that our lives are now part of the block, and that nothing will ever remove that part of the overall pattern.

The overall sense, I think, is meant to be comforting. Albert Einstein if often quoted as supporting this view. But it’s worth noting the context of the quote.

Now he has departed from this strange world a little ahead of me. That means nothing. People like us, who believe in physics, know that the distinction between past, present, and future is only a stubbornly persistent illusion.

Letter to Besso’s family (March 1955) following the death of Michele Besso,

But what exactly do we mean by “right now” in this context? Certainly not the same now we mean when we talk about our current plane of simultaneity within the block, a notion that general relativity has rendered into something relative to our current frame. So the “right now” that historical figures and past relatives are still living their lives would have to be a “now” outside of our normal conception of time.

And why exactly should we take comfort that our lives are ostensibly an undeletable part of the block? Who will ever see that part of the pattern, and in what context, being outside of time and space? God? Higher dimensional aliens? I can see a religious person finding comfort in the first answer, but the second one doesn’t necessarily provide me any comfort.

I think the block universe is an interesting metaphysical concept, one that could be true. But I’ve never seen it, in and of itself, as a particularly comforting one. But maybe I’m missing something?

159 thoughts on “The block universe is interesting, but not comforting

  1. The idea is mathematically elegant, but it is not emotionally soothing.

    As a mathematician, I appreciate that elegance. But I have come to doubt that there is anything mathematical about reality. The mathematics that we see are only part of our mathematical models. Reality is probably stranger than we are able to imagine.

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    1. It is striking that many new discoveries in physics happen first with mathematics. Often the people making those discoveries, or those around them, are quick to say, “Don’t worry. It’s not like this crazy thing is true. It’s just a mathematical convenience.” But often it does go on to be true.

      Reality is definitely stranger than we can imagine, often in way we don’t want to accept.

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      1. I do not get this kind of talk —- “Reality is stranger than we can imagine.”
        How alien could “reality” really be? Physics is not all ‘reality’ is. Physics needs to be able to connect to our best ideas in biology, ethics, art, …

        I believe, to understand “reality”, we need to start in the middle of it, with living things and their increasing complexity and complex ways of life —like our own.
        In some sense, the world physics shows us is an instrumentality. A useful perspective but not all of ‘Reality’.

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        1. Interestingly, that phrase is a paraphrase that dates back to J.B.S. Haldane, a British biologist.

          I have no doubt that in reality the future will be vastly more surprising than anything I can imagine. Now my own suspicion is that the Universe is not only queerer than we suppose, but queerer than we can suppose.
          Possible Worlds and Other Papers (1927), p. 286

          Consider if we encountered a well educated person from the year 1500. For that person, the earth is the center of the universe with everything in a very small universe rotating around it, rather than an infinitesimal speck of leftover stardust in an unimaginably vast darkness. For them, the world is only a few thousand years old rather than billions. They have no idea of evolution, relativity, the unsettling implications of quantum mechanics, what causes diseases, or many other things. If we told them of the modern view of reality, it would be stranger than anything they had imagined.

          Now, consider if we encountered a person from the year 2500.


          1. And yet, there has to be a reasonable train of thought of how we got there from here. However strange physics gets, it is still a human activity—- at least the Doing Of science is; it is a practice/praxis, an agency.

            And this gets us back to the original issue about The Block Universe and whether it is a “comfortable” perspective. It is not. I believe that human/personal vocabulary has no place there. That is a category mistake. It contains no agency. Persons don’t exist there, not you or I, and not Julius Caesar or Albert E. Only quantum waves and other such depersonalize spacious-temporal objects. It is all external relationships.

            So this leaves a huge disconnect in our thinking, if you do not allow for the reality of Doing, as well as the reality of Happening. There must be a compromise position. I think Dennett with his Intentional Stance is about this very point. From a physics-first perspective, only Emergent Realities allow the act of learning by humans.
            The universe can be no more strange than the ability we have of learning that it might be so.


          2. On further consideration, I think it would satisfy me if you guys said ‘Physics is stranger …”, not “reality is stranger…”
            I think humans have always been “in touch with reality” and that includes 1500, now, and 2500. How would we exist if we weren’t? And that includes our ideas about “reality”, they can’t be that wrong or our human cultural experiment would never have gotten this far.


          3. I don’t know Greg. We seem able to deal with our immediate reality on a day to day basis, on scales we evolved to deal with, as long as things don’t change too much or too fast. The fact that so many people in this country can’t seem to take the virus seriously, understand how economic policies affect them, or many other aspects of modern life, doesn’t incline me to think we’re that clued in to our reality.


          4. Right. Things only seem strange when they are unfamiliar. Gravity, for example, could easily be called “spooky action at a distance” if it were not so common that we all take it for granted.


  2. Looking for “comfort” in a scientific theory sounds a bit like looking for “beauty” as a criterion for a scientific theory. Neither strike me as relevant. That said, I find a certain degree of comfort in encountering a theory that makes sense to me; to coin a psychological term, “cognitive consonance” (as opposed to “cognitive dissonance”). That doesn’t mean I require theories to make sense to me. When they don’t, I shift gears and try my best to gain traction or I move on. I like the idea of us being patterns rather than definite things. Patterns are often in the minds of the conceivers and there might be many different ways of conceiving our patterns, some of which might be useful in certain contexts.

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    1. I agree on comfort not being good criteria. A theory definitely has to be compatible with empirical data. If it’s not, it doesn’t matter how comforting, beautiful, or consonant it is.

      On the other hand, we’re sometimes faced with multiple theories compatible with the data, or multiple speculative theories where tests to narrow down the options aren’t yet possible. We often talk about parsimony in those cases, but the reality is beautiful or consonant theories often seem a lot more parsimonious to us than theories we deem ugly or dissonant. And a lot of people won’t accept unsettling theories, no matter how elegant, until the evidence is overwhelming.

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  3. ” so from our perspective, we exist in a dynamic and changing reality. But from outside, the block is like a movie DVD,”

    From outside the block, time is depicted as a dimension within the block, so all temporal distinctions will be painted as spatial. That doesn’t mean that they really are, any more than if I paint a picture of Trump as green, he will stop being orange.

    “a static object containing a story, with the beginning, middle, and end already set.”

    Emphasis added to show the mistake. Time is off your map, if ye be outside the block. Here there be monsters.

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      1. I guess the block universe picture is supposed to enhance your intuition that the past and future are real. The trouble is that it enhances a bunch of wrong intuitions even more. A better approach IMHO is to draw a two-dimensional graph with two different time axes, as measured by two observers on different inertial trajectories. That will show you that you can’t make only one time “real” without artificially promoting one set of observers to having The One True Time measurement.

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        1. I think space time diagrams are definitely helpful in understanding specific cases in relativity. But I think the block universe is supposed to be an extrapolation from all those cases to what it means for the universe overall. The problem is, it’s an extrapolation we may never be able to actually test.


      2. It’s an Ideal reference point. It is a useful perspective to adopt, for some purposes—like if you want to blow up Hiroshima (but even a lot better stuff). It is not useful if you are standing in front of your closet trying to decide what shirt to wear to work today.

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    1. For myself, I find comfort in understanding the world. If the block universe helps with that understanding (which it does, especially with regard to the role of mutual information in consciousness), then I find comfort in that.

      Paul is correct in recognizing the difficulty of understanding the block universe without using concepts that involve time. But I don’t think that makes it pointless. It just makes it harder.


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      1. I don’t know that I would say understanding reality gives me comfort, but it does trigger some kind of reward system in my brain, a type of thrill. Once I think I understand something, particularly something I’ve long struggled with, I often find myself dwelling on it for a while and getting satisfaction from it. (During these periods, it takes discipline not to post on it constantly.) That wears off in time and I end up looking to get my understanding fix somewhere else.

        Maybe I overstated things with “pointless.” But I do often think the language difficulties leave a lot of people somewhat confused on exactly what the block universe is supposed to be.


  4. It seems to me that if someone lived, their life ‘crystallised’ something actual out of multiple possibilities, and that the effect of that is felt by everything subsequent to them. While the strongest such effects are physical artefacts, genetics and culture, from the viewpoint of physics they have an effect on everything within the ct (speed of light x time) cone that spreads out from them. In that sense their life is there for all time, its effects echoing into the future.

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    1. I think that’s definitely true. But it also seems true of a hurricane, or a virus. And on the scope of the universe, a quasar has far more causal influence.

      Of course, a person has a larger and longer lasting effect for the people that knew them. In that sense, the effects of the person live on after they’re gone in those people. So to their fellow humans, it’s very significant, and perhaps the best any of us can hope for.


  5. I don’t think the BUH is true, so I can’t find comfort in it. Seems like it could equally be discomforting since it’s a fully deterministic view. The raisins just are, from beginning to end.

    Most religious people believe in some form of free will, so I’d suspect most would just reject the BUH on that grounds.

    FWIW, MWI presents a form of block universe, especially versions where the wave-functions always exist (which I’m beginning to believe is the version that has to be considered). MWI, in any event, presents a fully deterministic universe.

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    1. I’ve never felt the discomfort of determinism. I might if that determinism could ever be cashed out in a meaningful way, but none of us is Laplace’s demon. Although I guess if you’re looking at it from the idea of ultimate judgment, I could see how it might be discomforting.

      Definitely the MWI, or any other deterministic interpretation of QM, leads to a form of the block universe. It seems like the possible fundamental randomness of QM is the only thing that would prevent a block universe scenario. At least unless some form of interactionist dualism were to turn out true.


      1. Determinism opposes free will, which is why some people are uncomfortable with it. Kind of a funny duality. Comfort or discomfort, depending on one’s view, about the BUH or determinism in general.

        I do think what we perceive as quantum randomness is an argument against the BUH. There is also the need to explain the subjective now we experience and share. I also have questions about how all that structure came into being. It’s one thing for the universe to calculate itself as it goes, but quite another to produce that much computation all at once as the BUH implies.

        And I think a key argument in its favor, the SR simultaneous futures argument, to actually be contrary to what SR says — that we can make no statements about “now” or simultaneity until the light from their events reaches us.

        Put it this way: I consider the BUH much less likely than MWI. 😀


        1. Determinism certainly opposes contra-causal free will. But I’m a compatibilist, so for me free will is still there.

          Most of the descriptions I’ve seen of the block universe don’t get into how it got there. The concept itself seems incompatible with an origin. Such a description would involve a time sequence, but we’re talking about something that contains all of time. It seems like that’s one of the concept’s problems. It’s extremely counter-intuitive to even think about. Most people can’t without thinking of it as somehow existing in an “outer” time of some sort, where the question of how it got there can arise.

          Strangely enough, while my credence in the MWI is higher than yours, I agree that the block universe is less likely. It involves a further extrapolation of what we might currently take to be our fundamental laws. Even if we have those laws right, we have no way to know whether that understanding is complete. In other words, we don’t know what unknown factors might frustrate that prediction.

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        2. Scientific determinism isn’t like theological determinism, and specifically doesn’t oppose free will. Most relevantly and surprisingly, scientific determinism doesn’t imply universal causality. That is, not every physical event or state has a cause, if we impose a common sense restriction on how we define “cause”. The restriction: causality must be asymmetric, i.e. one-way. If A causes B, then B does not cause A. A microscopically detailed state is linked by natural law to earlier and later microscopically detailed states (determinism), but this linkage is symmetric. So it is not causal.

          Time is not like a river. Or rather, it is so only at a macroscopic level, where we use coarse-grained descriptions (W > 1, W being the count of microscopic states that satisfy the description) that are associated with non-zero entropy (S = k log W), which increases. It is only here that time “flows” like a river. No hydraulic forces are pushing on you from the microscopic details of the past. From the macroscopic past, there are definitely influences you must deal with, but you have many options of how to deal. And the macroscopic past is not sufficient to determine a unique future for you. Insofar as the Block Universe picture interferes with the “fundamentally, time flows” assumption, it can actually help you see why scientific determinism doesn’t conflict with free will.

          By the way – to me, the Block Universe is a picture/metaphor. I don’t know what Hypothesis it is supposed to be – maybe the idea that all times Chéngwéi equally real? (Chéngwéi – Mandarin for “to be” – Mandarin is, I hear, a tenseless language. That would come in real handy here!)

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          1. I remember your free will posts — commented on several of them — and my view is still that time is axiomatic, a fundamental aspect of reality. (So fundamental, I suspect time existed before the Big Bang. I see space as less fundamental than time.)

            So, for me, causality is just what happens when the laws of physics are combined with time. Thermodynamics and entropy, likewise, are emergent from physical law plus time. The physical behaviors responsible for Boltzmann’s entropy equation are exactly due to this behavior — a physical system is far more likely to evolve to larger macro states simply because they’re larger.

            The asymmetry you want comes from time’s “ratchet” — time only goes one way; B can never retro-cause A. The basic laws of physics are symmetrical with respect to time, but reality simply cannot go backwards.

            I agree time isn’t a river (nice metaphor, though). Time is a spacetime curve we move along (a worldline). Just tonight, hanging with friends, I got into how, sitting still, we’re moving along the time axis at max speed, the speed of light. (The spacetime time axis is formally ct, not just t. (It was originally ict, and because the terms are squared, we get ct^2, which is where the +++- spacetime signature comes from.))

            The problem for free will with determinism is that, if reductionism is true, the macro world is just as determined as the micro world. (And with no recourse to quantum randomness.) Chaos means we have no hope of predicting anything, but the future (and the now) seem fully determined. Free will seems to be an illusion unless someone can explain how it arises.

            FWIW, I think higher-level brains just might be the one non-determined system in reality. (Maybe even all brains.) (You can find posts about that on my blog if interested.)

            And I am beginning to question whether the real numbers apply to physical reality. There are a lot of significant problems with the continuum. Maybe reality is rational, but not real (numerically speaking).

            The Block Universe Hypothesis is eternalism, the metaphorical image of a giant block of Lucite with embedded bits. It apparently sprang into existence, all the structure calculated. And, for some reason, we’re trapped in a “now” moment that began at birth and ends at death.


          2. I agree that time is fundamental – but time’s ratchet is not. The ratchet comes from entropy, not the other way around. If time extends beyond the Big Bang, then any intelligent creatures in that part of spacetime live “backward” relative to us. They remember things from times we would consider the less-distant past than their act of remembering, and they plan and control things we would consider to be in the more-distant past. Because that’s how their entropy gradient would go.

            It doesn’t matter if the future is determined, if the determining factors are not independent of you. Consider: why is a man in jail unfree in a way that a woman in a room with a curtain for a door is not? Because no matter how the jailed man pulls or pushes on the iron bars, they remain in a position which blocks his exit. Whereas the position of the curtain is not independent of what the woman does. And because the microscopic details of the past are connected to you only by bidirectional (in time) laws, those details are not independent of you. The thought that they are is a cognitive illusion, based on your all-macroscopic experience.

            If a Block Universe contains time, the block does not “pop into” existence. You would need some kind of meta-time for that, which is bizarre and excessive.

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          3. “I agree that time is fundamental – but time’s ratchet is not.”

            So time is fundamental but not omni-directional?

            I disagree entirely about entropy — I believe it’s just a consequence of the laws of physics over time. Entropy is about configuration states evolving towards more probable ones.

            I also disagree any part of spacetime can run “backwards” (for any reason). Entropy does not control time.

            I do agree the BU doesn’t “pop into” existence. As you say, that would be bizarre. In fact, it doesn’t exist at all. 🙂


          4. Wyrd, I’ve been busy with our other discussion about the BU but I’ve been meaning to ask about your remarks here. As a preliminary, I’d appreciate your providing a definition of the ‘time’ you’re discussing, although you likely agree with St. Augustine of Hippo, who said, “If no one asks me, I know, but if any person should require me to tell him, I cannot.”

            As you say, “the basic laws of physics are symmetrical with respect to time.” What is not symmetrical is not reality, however, but the stream of consciousness, which has a fixed futureward narrative direction. Physical laws and reality can operate backwards but consciousness cannot. Reflexes and memories are also encoded with a learned futureward narrative direction—that’s how we can tell that a movie of a line of people backing off a stopped train is being played in reverse.

            It appears that your usage of Minkowski terminology is incorrect. Minkowski introduced the term ‘worldline’ to denote the path that an object traces in 4-dimensional spacetime. Per Wikipedia, “Each point of a worldline is an event that can be labeled with the time and the spatial position of the object at that time,” i.e., the path in all four dimensions of spacetime. Time is not a worldline or a “spacetime curve we move along,” as you wrote. Physicist Robert Geroch wrote in General Relativity from A to B:

            There is no dynamics within space-time itself: nothing ever moves therein; nothing happens; nothing changes … one does not think of particles as ‘moving through’ space-time, or as ‘following along’ their world-lines. Rather, particles are just ‘in’ space-time, once and for all, and the world-line represents, all at once, the complete life history of the particle.”

            Further, the BU does not mean that we’re “trapped in a ‘now’ moment that began at birth and ends at death.” Our lifetimes are permanent objects in spacetime with extended volume called worldtubes. A worldtube is not a ‘now’ or a “now moment.”

            Your claim that begins “The spacetime time axis is formally ct, not just t” misconstrues the mathematics for a spacetime interval. From the discussion at:


            … special relativity provides a new invariant, called the spacetime interval, which combines distances in space and in time. All observers who measure time and distance carefully will find the same spacetime interval between any two events. … The constant ‘c’, the speed of light, converts time units (like seconds) into space units (like meters). Seconds times meters/second = meters.

            That means that your surmise that “we’re moving along the time axis at max speed, the speed of light” is incorrect. As Geroch wrote (above), nothing in 4-dimensional spacetime is moving at all. Also, a spacetime interval (and its mathematics) cannot exist in your conception of the geometry of the universe because a spacetime interval only makes sense if the different times t1 and t2 are co-real (i.e., both exist), which you claim is not possible.


          5. “I’d appreciate your providing a definition of the ‘time’ you’re discussing,”

            I hold time to be fundamental and axiomatic, so it can’t be defined, just described. My notion of it is essentially the common view of it being something that either flows or through which we flow.

            “It appears that your usage of Minkowski terminology is incorrect.”

            Nope. I’m using it exactly as Minkowski did. We move through 4D spacetime. If you go back and read the paragraph in question, I was contrasting our motion along the time axis when we have no motion along any physical axis with what happens when we do have motion along a physical axis. Regardless, in all cases, our proper time always ticks at the same rate, hence our worldlines, our path through spacetime, is our personal time axis.

            “Your claim that begins ‘The spacetime time axis is formally ct, not just t’ misconstrues the mathematics for a spacetime interval.”

            Nope. Firstly, you’re confusing the spacetime interval with the time axis. Secondly, defining the time axis with units of ct is necessary to create a 4D spacetime.

            Using units of ct on the time axis gives that axis units of length. If the length unit is 3×10^8 m/s × 1 s, then the seconds cancel out and we’re left with meters, a unit of length. And it’s common in these situations to just define c as 1, so there’s no numeric scaling of the seconds.

            “That means that your surmise that ‘we’re moving along the time axis at max speed, the speed of light’ is incorrect.”

            Not my surmise. It’s textbook SR.

            “Also, a spacetime interval (and its mathematics) cannot exist in your conception of the geometry of the universe because a spacetime interval only makes sense if the different times t1 and t2 are co-real”

            That’s utter nonsense. The spacetime interval is just an invariant measure in Minkowski space. It’s just the Minkowski equivalent of the Pythagorean distance in Euclidean space.

            Euclidean distance: x^2 + y^2 + z^2 + w^2
            Minkowski distance: x^2 + y^2 + z^2 – t^2

            As I mentioned above, the original source of the minus was defining the time units as ict (leveraging how multiplication by i creates a new orthogonal axis). Since the terms are squared, i turns into -1 and creates the subtraction. In GR there’s just a -+++ metric, which can equally be a +— metric.


          6. Entropy is about configuration states evolving towards more probable ones, sure. The open cosmological question is whether this happens in both temporal directions away from the low-entropy Big Bang state, or only in one. If it makes you happy, by all means describe these processes as “the Big Bang having evolved from a higher-entropy state, then evolving into another (our) higher-entropy state.”

            I don’t know what it would mean for “entropy [to] control time.” My claim is only that entropy controls our experience of time. And given that it does, we can explain our observations without positing a metaphysically objective (perspective-independent) True Arrow of Time.

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          7. Entropy gradients presuppose a time line. But in order to portray that line as a ray, a single-arrow beastie instead of a two-arrow one, that’s where entropy gradients come in. The single arrow faithfully represents something important about the macro level, but not about the level of ultimate constituents.

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          8. We can agree to disagree, but entropy isn’t just a consequence of time’s ray-likeness even if the latter is a fundamental fact. We both posit a low-entropy Big Bang. You add a True Arrow of Time on top of that, while I settle for the Entropic Arrow.

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          9. I don’t add time’s arrow on top of anything, time is fundamental, and that includes that it only goes one way. That’s what I meant by “time’s ratchet.” One-way time, for me, is axiomatic — even more so than space, since, for me, there is a “before” to the Big Bang as well as an “after.” Time is part of whatever meta reality provided the laws and context for the Big Bang in the first place.

            I totally agree about a low-entropy Big Bang, but I see entropy as a measure of something, not any kind of force in itself. The gradient you speak of is just a matter of statistical improbability. If it were a real gradient, it could never be defied, even in principle. An Entropic Arrow is consequential and conditional.

            Another thing for me is, entropy is always requires context and definition. For instance, my CD collection, if I define a total sort order such that there is only one possible fully sorted condition, then I can say the entropy of the collection, per this definition, is zero (k_b × ln 1 = 0). But I also have to define what I mean by the macro states of the system. How do different unsorted states compare to each other in terms of their entropy (which ones are in the same macro state)? All that, to me, makes entropy just a way of measuring and describing systems. I don’t attach any more significance to it than that.


          10. I agree that entropy is consequential and conditional, and that the entropy gradient can be defied. Indeed, Crooks fluctuation theorem gives the probability of an entropy-decreasing process – often absurdly tiny, but never quite zero. And of course, the fact that entropy gradients are consequential upon the existence of a particularly low entropy state is the beauty of it! It’s not an extra assumption, it’s buy one Big Bang, get a workable arrow-of-time free. Workable meaning that it explains the observations that led us to see time as asymmetric in the first place.

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          11. Correct me if I’m wrong, but it seems like the only point of disagreement is that I see (fundamental) time as axiomatically one-way whereas you see it as bi-directional so the only “ratchet” is emergent entropy?

            Question: “And of course, the fact that entropy gradients are consequential upon the existence of a particularly low entropy state is the beauty of it!”

            I don’t follow. Why a particularly low entropy state? Isn’t the gradient always there, per K_B ln Ω? Are you referring to how it could be said to be less “steep” as Ω increases?


          12. You’re exactly right about the only point of disagreement.

            The “particularly” low entropy state is needed to explain our known history. Of course how low you need to go, depends what you’re explaining. To explain all astronomical observations combined, you need the extremely low-entropy Big Bang that cosmologists infer. To explain just the fact that for thousands of years, humans have been able to remember their past but not to remember their future, you “only” need a very low-entropy state some thousands of years ago.

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          13. “To explain all astronomical observations combined, you need the extremely low-entropy Big Bang that cosmologists infer.”

            Ah, yes, we agree on that, too. (Roger Penrose, in his book Cycles of Time, has a good explanation of what makes the BB low-entropy (gravity). The idea had always been a bit fuzzy in my mind until then — the tendency to equate the initial moments of identical quark soup everywhere to a gas-equalized room, which is a maximal entropy condition. But gravity changes the dynamics.)

            I can’t go along with entropy being why we don’t “remember” the future, although I do agree creating memories necessarily increases entropy. All increased structure does!

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          14. 🙂 No, sorry, I can’t. In my view entropy is strictly consequential and never directly causes anything. It’s not what we would define as a “force.” To me it’s like asking if a shadow causes the object that creates the shadow.


          15. Not a sufficient reason in the sense of cause, perhaps (although I think it is, but never mind that), but a sufficient evidence. As indeed, in the right circumstances, a shadow of, say, a dog can be sufficient evidence of a dog.

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        3. Wyrd, as regards quantum randomness, consider this observation from physicist Brian Greene:

          “… loose language can be deceptive. The mathematics of quantum mechanics, Schrödinger’s equation, is just as deterministic as the mathematics of classical Newtonian physics. The difference is that whereas Newton takes as input the state of the world now and produces a unique state for the world tomorrow, quantum mechanics takes as input the state of the world now and produces a unique table of probabilities for the state of the world tomorrow. The quantum equations lay out many possible futures, but they deterministically chisel the likelihood of each in mathematical stone. Much like Newton, Schrödinger leaves no room for free will.

          Perhaps the idea of QM randomness is a physics urban legend rooted in a misunderstanding of probability. Greene’s remark lends philosophical support to the MWI, though. I see no reason to believe that the existence of our spacetime precludes the existence of an infinity of others.

          Secondly, the subjective ‘now’ is simply the feeling of the immediacy of an experience. It’s wholly explained as an artifact of consciousness

          Third, “questions about how all that structure came into being” are unanswerable and of the kind typically posed by science fiction writers. Perhaps the computation was completed prior to the result being impressed onto the hologrammatic medium of spacetime. Of course, the computation would have to take place in some sci-fi meta-time … but that ‘compute-print’ sequence would answer your “all at once” concern.

          Lastly, light cones are causal boundaries and irrelevant in determining what events are co-real—what events coexist. In the block universe, all events are co-real.


          1. “Perhaps the idea of QM randomness…”

            From a God’s-eye view, if one believes in the MWI (which, BTW, I don’t), then QM randomness does go away, but only from that God’s-eye view. From the perspective of any given branch, reality still appears random. The Schrödinger does evolve deterministically, but measurements involve probabilities, even in the MWI.

            “I see no reason to believe that the existence of our spacetime precludes the existence of an infinity of others.”

            I don’t rule them out, but I’m struck by how the main place we find ideas of extra dimensions and multiple worlds is comic books and science fiction. And some mathematical theorists who, I suspect, have gotten “lost in the math.”

            “Secondly, the subjective ‘now’…”

            Okay, but if the BUH is correct, and all moments exist equally, why do we experience only the ‘now’ and why do we share it with others? If the BUH is correct, why haven’t our senses evolved to have some sense of it?

            “Third, ‘questions about how all that structure came into being’ are unanswerable…”

            Yeah, exactly my point. The BUH is science fiction. (See my post Blocking the Universe for details.)

            “In the block universe, all events are co-real.”

            This represents a fundamental misunderstanding of SR. A key tenant of which is that simultaneity is virtual — we can make no statements about events outside our light cone until information about that event reaches us. We can only speak of our own ‘now’ — it’s only in retrospect we’re able to define some event with space-like separation as having happened “simultaneously” with some event in our past.


          2. Wyrd, regarding MWI:

            This Wikipedia article lists well over a dozen QM Interpretations, all of which are metaphysics —philosophy … and not verifiable in principle:


            Consequently we can’t believe in any of them. However I appreciate the creative boost to science fiction they’ve provided, which is their most valuable contribution.

            The ‘now’:

            We experience the completely subjective ‘now’ as the momentary immediacy within the stream of consciousness we’re experiencing. All of our conscious moments feel like now’s. If we’re not separated by too much distance and not noticeably accelerating relative to one another, my feeling of ‘now’ will correspond in clock time to your feeling of ‘now’ by virtue of us both being at the same temporal coordinate of spacetime. There is no objective ‘now’ in the universe that we can experience together—‘now’ is a feeling.

            Origin of Spacetime

            That’s the same age-old unanswerable question of “where did everything come from”? It’s completely irrelevant to the geometry of the universe. Proposed explanations include God, “everything always was and always will be” and a Boltzmann universe that just ‘popped’ into existence in its entirety. Being unable to explain something’s origin doesn’t make that something disappear.


            Wyrd, light cones are a mathematical abstraction describing a so-called “zone of causality.” But you’re claiming that everything outside our light cone doesn’t exist—isn’t real! You surely realize that light cones expand with time. According to you that means that, as our light cone expands, events become real that weren’t real before.

            Setting aside the fact that the universe contains an infinity of light cones, let’s start a brand new light cone with a flash of light as Wikipedia’s “light cone” article describes:

            In special and general relativity, a light cone is the path that a flash of light, emanating from a single event (localized to a single point in space and a single moment in time) and traveling in all directions, would take through spacetime.”

            Let’s locate our new flash of light about eight light-minutes away, about the distance from the sun to the earth. According to your statements, none of us is real to an observer within that light cone until the light cone expands to reach us, at which point we magically become real. Hokey smokes Wyrd! How about citing for our benefit a couple of accessible references of practicing physicists who agree with your “light cones create reality” proposal. Thanks in advance.


          3. Guys,
            This is an interesting discussion, but the rhetoric seems to be escalating. Please do me a favor. Let’s keep this friendly and respectful, and try to disagree without provoking each other.


          4. Stephen,
            The status of interpretations of quantum mechanics can be affected by observations. For instance, if an actual physical wave function collapse is ever detected, it would falsify any interpretation without a collapse (such as the MWI). Conversely, as larger and larger objects are held in quantum superposition, it puts increasing pressure on the assumption that a collapse actually happens. If a conscious being were ever put in superposition, it would be tough to argue that versions of them collapse out of existence without direct evidence.

            For the MWI in particular, Brian Greene and others have noted that it is possible, in principle, to detect interference between decohered branches (worlds), albeit very difficult. I read somewhere it was equivalent to trying to figure out how the gravity of Jupiter affects the orbit of the ISS.


          5. The thing is, the MWI does have a form of, for lack of a better word, “collapse”.

            It certainly has measurement, right? Alex can measure vertical electron spin and end up in separate branches [Alex-up] and [Alex-down]. Both branches now have a wave-function in a known state. Repeating the same measurement returns the same result, so the wave-function has, in some sense, collapsed as a result of the measurement.

            Measurements, interactions, whatever you want to call them, do change the measured wave-function.


          6. When it comes to collapse, we can talk about an epistemic collapse or an ontic collapse. Epistemic collapse is about what an observer knows and is trivially true for all interpretations. Ontic collapse is all the possible outcomes but one ceasing to exist. The MWI doesn’t have an ontic collapse.

            For the MWI, I suppose we could talk about an accessibility collapse, where all the outcomes but one become inaccessible, which would be true on any one post-measurement branch.

            The MWI definitely has measurement. It’s just that the observer has no special role. Any measurement like event, that is, any magnification of results of an individual quantum event, such as maybe a radioactive particle contacting DNA and causing a mutation, leads to diverging branches.


          7. Call it “accessibility” collapse if you want, but the wave-function does change instantly as a consequence of the interaction. (It would have changed in a different way had Alex measured the horizontal axis.)


          8. Remember, the MWI is QM without the ontic collapse. Nothing happens instantaneously in the pure quantum formalism. Certainly decoherence, which is what leads to the loss of access to the other branches, happens very rapidly depending on the environment, but that’s not the same as the instantaneous collapse.


          9. “Nothing happens instantaneously in the pure quantum formalism.”

            How do you account for what happens when Alex makes a measurement? There is still a change from the wave-function’s state before and after.


          10. Under both Copenhagen and MWI, Alex experiences the same results in her subjective timeline, although under MWI that timeline is just one of many branches. But MWI’s accounting of the wave function is different. It certainly evolves as a result of the measurement, but doesn’t have the sharp discontinuous abrupt change stipulated by Copenhagen and related collapse interpretations.


          11. But in some cases, such as this one, it has to. Even from the God’s-eye view of all branches, the measurement Alex performs causes an abrupt change to the wave-function as a consequence of the measurement. The interaction causes the wave-function to be in a different eigenstate, and that change happens instantly.


          12. Depending on the version of MWI, prior to the measurement, there either are two identical branches or just one branch. In either case, the “particle” is in a superposition of all possible states.

            Regardless of the version, after the measurement, there are two branches, and in both branches the “particle” is in a known eigenstate. Repeating the same measurement gives the same result.

            So, because of the interaction, the wave-function is different before and after.


          13. Not sure whether the difference here is terminology or ontology. I’ll describe my understanding and see which way it might shake loose.

            Under MWI, the particle remains in a superposition of all its states. Depending on the exact measurement, it does cause at least some of the branches of that superposition to decohere from each other, so the wave function is definitely altered. But it’s a very different account from the Copenhagen one, a continuous (albeit rapid) evolution, instead of multiple possible states instantly transforming into one.


          14. It is definitely a different account in that the MWI preserves all quantum “choices” while the CI collapses those into a single outcome. On the other hand, as you say, the wave-function is definitely altered.

            In beam-splitter experiments, the difference between the two seems more stark. As we’ve discussed in the past, in two-slit experiments, it’s not clear (to me) exactly where (or even if) branching occurs under the MWI. Spin-measurement experiments are a bit unique in making a measurement, but still having an evolving quantum system post-measurement.

            A spin measurement can only have two outcomes, hence two branches. In both of those Alex has altered the original wave-function as a consequence of the measurement. (Since one Alex has a spin-up particle and the other has a spin-down, they obviously don’t have identical wave-functions, but they each have a particle with a wave-function in a known eigenstate.)

            So it seems there are different … levels? types? kinds? … of “collapse” depending on the situation.

            There is one kind where an in-flight particle’s momentum description means it’s everywhere and nowhere, but the point-like interaction “collapses” that description “instantly” throughout space (seeming to violate locality). Beam-splitter experiments have that kind. In the MWI, that’s just separate branches.

            There’s what might be happening in two-slit experiments — the branching is in where the particle lands, and again there is the “collapse everywhere” type. If the branching involves the two paths through the slits, then I need a quantum mechanic to explain the exact physical mechanism there, because it appears that kind of branching merges at the point interaction.

            Then there’s what happens when we make spin measurements, which seems a different situation. There’s clearly branching, but rather than “collapse” in the “goes away” sense there is “collapse” in the “sudden shift” sense.

            I do think it’s to the point we need an expert quantum mechanic.


          15. When it comes to the MWI, the standard answer is, of course, whatever the raw mathematical quantum formalism says. Definitely having an expert quantum physicist on hand would help. I think I have a very shallow feel for it, but I quickly get out of my depth if you hit me with questions requiring too deep an understanding.

            Given the way the word “collapse” is used in quantum physics, I think applying it to what happens under the MWI is probably adding confusion rather than clarifying. MWI is QM without the collapse. The collapse as usually defined as an abrupt discontinuous instantaneous event. In straight Copenhagen, it’s a non-mathematical event that ends the evolution modeled by the math. (In objective collapse interpretations, it’s additional mathematics added to that formalism.) In MWI, I think all we can talk about is the illusion of the collapse. (Phenomenal collapse?)


          16. “The collapse as usually defined as an abrupt discontinuous instantaneous event.”

            Right, and my point is that I think it does happen under the MWI, too. And I’m not sure in either case if there is math for it.

            What bothers people under the CI is that the Schrödinger equation is a linear equation — fully deterministic. But any “measurement” affects it, and I’m just not sure the MWI actually does get entirely around that fact.

            I don’t think it’s an illusion. Measurement does affect the wave-function ontologically.


          17. “…‘now’ is a feeling.”

            Sure, but where does it come from? In an evolving universe, it’s just part of that evolution. In a block universe, time is static and there is no flow, so why does ‘now’ select a special moment in the static block? Why that moment? Why do we, here on Earth, appear to be at the rough time coordinate 13.8 billion years when the block must contain trillions of years.

            “Being unable to explain something’s origin doesn’t make that something disappear.”

            Of course not, but we can question the implications of those origins. One story asks us to believe in a Big Bang from which the universe evolves and we see the result of 13.8 billion years of a machine that calculate itself over that time. Another story asks us to believe all that generated structure — and much more — sprang into existence all at once. It isn’t just the last 13.8 billions of structure — it’s the trillions of years that follow, too. And surely the block must extend beyond our visible universe, so it’s a vast amount of structure in time and space. Something has to account for it.

            As you said yourself, “Perhaps the computation was completed prior to the result being impressed onto the hologrammatic medium of spacetime. Of course, the computation would have to take place in some sci-fi meta-time” Exactly. It has to be accounted for. The BUH suggests a dual creation: The calculation first, and then the implementation. But what was the calculation done with?

            “But you’re claiming that everything outside our light cone doesn’t exist”

            No, that’s not what I said. What I said was: “A key tenant of [SR] is that simultaneity is virtual — we can make no statements about events outside our light cone until information about that event reaches us. We can only speak of our own ‘now’ — it’s only in retrospect we’re able to define some event with space-like separation as having happened ‘simultaneously’ with some event in our past.”

            (See my post Blocking the Universe for details.)


          18. Mike, I always try to avoid the personal and be friendly and respectful, although at times one’s enthusiasm can be misconstrued.

            Perhaps you’re responding to my use of the phrase “Hokey smokes!” which is a phrase frequently used by Rocky the Flying Squirrel addressing his buddy Bullwinkle the Moose, as in, “Hokey Smokes, Bullwinkle!”. It’s the equivalent of “Gosh!” or “Gee Whiz!” and simply expresses mild surprise, which was my intention in using it. I see from Wikipedia that the Rocky and Bullwinkle show appeared on TV in 1959 when I was a teenager. So both the show and myself are relatively ancient. I didn’t realize at commenting time that many folks might not understand the cartoon reference. Mea culpa

            Regarding “wave function collapse”: The wave function is a probability function—a mathematical entity. I realize that there’s been a lengthy (and ongoing) debate about whether wave functions are mathematical or objectively real. In 2012, for instance, Colbeck and Renner presented an argument favoring the objective reality of the wave function:


            … but they admit that “Our result is based on the assumption that an experimenter can, in principle, ‘freely’ choose which measurements he would like to carry out … Hence, if one is ready to accept this assumption, our answer can be considered final.”

            So it looks like their argument is rooted in the philosophical quandary about the reality of “free choice.” Since this whole business is extremely murky territory, I continue to favor the “function as mathematical entity” perspective.

            I recall Greene’s statement as being that it may be possible, in principle, to measure some remnant interference from the decohered waves, but I can’t locate his exact quotation even after scanning The Hidden Reality. Can you point me to it? I ask because may be possible and is possible are distinctly different views of possibility.


          19. Stephen,
            What’s always made me think the wave is physical is that something causes the interference effects. The success of quantum computing, which crucially depends on the reality of the wave and those interference effects for its parallel processing, also seems to increase support for it.

            I’ve having trouble finding the exact passage myself, at least the one I remember, in The Hidden Reality, which is making me wonder if I saw it somewhere else, possibly by another author. However, this passage from Hidden seems to capture the same idea. (It’s at the end of chapter 8.)

            Second, in some situations, the predictions of the Many Worlds approach would differ from those of the Copenhagen approach. In Copenhagen, the process of collapse would revise Figure 8.16a to have a single spike. So if you could cause the two waves depicted in the figure—representing macroscopically distinct situations—to interfere, generating a pattern similar to that in Figure 8.2c, it would establish that Copenhagen’s hypothesized wave collapse didn’t happen. Because of decoherence, as discussed earlier, it is an extraordinarily formidable task to do this, but, at least theoretically speaking, the Copenhagen and Many Worlds approaches yield different predictions.12 It is an important point of principle. The Copanhagen and Many Worlds approaches are often referred to as different “interpretations” of quantum mechanics. This is an abuse of language. If two approaches can yield different predictions, you can’t call them mere interpretations. Well, you can. And people do. But the terminology is off the mark.

            Greene, Brian. The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos . Knopf Doubleday Publishing Group. Kindle Edition.

            Greene’s description of Many Worlds is one of the best I’ve seen. He has a powerful gift for explaining complex concepts in an approachable manner.

            It’s bugging me that I can’t find the passage I remember. I may keep looking for it.


          20. Wyrd, our feeling of ‘now’ does not select a special moment. As I wrote previously, all of our conscious moments embedded in the BU are experienced as now’s—all of them. No single moment of consciousness is privileged over any other and no location on the temporal dimension is privileged over any other. They’re all real. Our worldtubes (“we”) are 13 or so billion years distant from what we believe was the Big Bang because that’s our location on the temporal dimension of spacetime relative to the temporal location we’ve computed as the Big Bang’s.

            The BU doesn’t imply that everything sprang into existence all-at-once. As I wrote, always having existed, “always was and always will be” is a possibility. We don’t have to account for the BU’s origin for it to exist. And the “dual creation” you suggest would actually be an infinite regress. If the BU were created in some meta-time then that meta-time reality would have had to be created in some meta-meta-time and so on, ad infinitum. As I wrote initially, the BU origin question is unanswerable and always will be unanswerable. The important point is that the origin of the BU is irrelevant to its existence.

            Of course the universe extends beyond our visible universe—our Hubble Volume as it’s called. As you know, the Hubble Volume, with the earth at its center, increases in size by one light year every year as light from more distant regions reaches us. Your premise seems to be that those newly visible regions didn’t exist before the light arrived—that those new observables just mysteriously popped into existence and became real.

            I completely agree with you that “we can make no statements about events outside our light cone until information about that event reaches us.” But that doesn’t mean that those events do not exist. See the “Chewie’s descendants” statement below … that’s what you’re talking about. That’s from Brian Greene’s explanation of “now slices” and “now-lists” in Chapter 5 of The Fabric of the Universe. (By ‘now’ Greene is referring to the common usage of the clock time correlated with the feeling of a particular moment’s ‘now’.) You can fetch Chapter 5 from my Google Drive here for a few days:


            Read his explanation until you get to:

            At such an enormous distance, it takes an enormous amount of time for messages to be received and exchanged, so only Chewie’s descendants, billions of years later, will actually receive the light from that fateful night … The point, though, is that when his descendants use this information to update the vast collection of past now-lists, they will find that the Lincoln assassination belongs on the same now-list that contains Chewie’s just getting up and walking away from earth. And yet, they will also find that a moment before Chewie got up, his now-list contained, among many other things, you, in earth’s twenty-first century, sitting still, reading these words.

            That bold-font phrase is what you’re talking about but Greene perfectly makes the case that the reality of an event is distinct from one’s ability to know about it.


          21. What makes ‘now’ special is that it divides what we remember from what we can only anticipate. Our consciousness is serial, with a past, a now, and a future. In the BU, exactly as you say, no moment is privileged. An evolving universe accounts for our perception of the ‘now’ but the BU does not. It has the same problem as Tegmark’s MUH — it doesn’t account for the subjective flow of time.

            My point about the implied origin of the BU is that it’s a huge ask. It’s a key reason I don’t believe in the BUH — I think the need to generate all that structure in advance is far too big an ask for a theory.

            And the BUH absolutely does imply all that structure is created in advance — that’s the key feature of the theory; it’s what distinguishes it from evolving and/or non-deterministic cosmologies.

            My point about the visible universe has nothing to do with light speed, but with pointing out how large the BU has to be. It’s not just our visible part, but the whole thing (whatever that is). And it’s the whole thing from Big Bang to however many trillions of years it exists. That’s a mind-boggling amount of structure to have to create off-line. Exactly as you say, it leads to infinite regress.

            The way out is understanding that the universe calculates its own structure as it evolves. That solves the structure issue and the ‘now’ issue.

            I’m glad you agree about statements outside our light cone. The next step is understanding that being able to say, after the fact, that some point in your past was “synchronous” with some point that, at that point, was in the “future” of some other perspective, does not require that “future” exist at that moment in time.

            A key aspect of SR is that simultaneity is virtual and relative — it’s a matter of your perspective. You can’t talk about something “five years in the future” being real when it takes ten years to demonstrate it.


          22. Wyrd, since all of your assertions contradict relativity physics, I’m repeating my request for verifiable support for your claims from recognized practicing physicists. Here is a list of your claims (italicized) that require substantiation along with my brief relativity-physics-compatible response:

            1. Wyrd: The subjective feeling of flowing time proves that objective flowing time exists.

            Our perceptions are simulations of sensation events and they don’t correspond to physical reality. Note that physics is unable to find objective flowing time. No experiment has ever been proposed, let alone run, to verify its existence. ‘Time’ is the temporal dimension of 4-dimensional spacetime and nothing else. I’ve proposed that our feeling that there’s an objective “flowing time” is an externalization of the stream of consciousness, which is a fact of normal consciousness that needn’t be accounted for in physics.

            2. Wyrd: ‘Now’ is a single moving privileged moment that marks the current temporal location of objective flowing time.

            Physics is unable to find a ‘now’ as well—there is no ‘now’ in the universe or in the laws of physics. ‘Now’ is a feeling, an artifact of consciousness, and in BU terms, every conscious moment embedded in the BU is experienced as (feels like) a ‘now’ when it is experienced.

            3. Wyrd: Things whose origin is unknown cannot and do not exist.

            No comment from me—that’s not a credible assertion.

            4. Wyrd: The BU implies that all structure is created in advance.

            There’s no such thing as an “in advance” of the BU, which would be a time that precedes existence. Imagining that impossibility is what leads to an infinite regress of ‘meta-times,’ not the size of the universe as you just wrote.

            5. The universe calculates its its own structure as it evolves.

            Absent objective flowing time, whose existence cannot be demonstrated, that’s an impossibility and its ‘calculation’ mechanism is inconceivable.

            6. If we cannot observe something, it doesn’t exist.

            Like item 3, that’s also not a credible assertion. Note again, from Brian Greene’s explanation:

            “… when [Chewie’s] descendants use this information to update the vast collection of past now-lists, they will find that the Lincoln assassination belongs on the same now-list that contains Chewie’s just getting up and walking away from earth. And yet, they will also find that a moment before Chewie got up, his now-list contained, among many other things, you, in earth’s twenty-first century, sitting still, reading these words.”

            The phrases “the same now-list” and “now-list contained” means that the events referred to are co-real—they all exist together (all-at-once), regardless of their location on the temporal axis of spacetime.


            At this point, Wyrd, we’ve both described our viewpoints and further discussion seems unwarranted. However, you still haven’t identified any practicing physics professionals and credible physics that support your opinions as itemized above. So please provide them if you respond, preferably numbered for the claim substantiated. Many thanks in advance.


          23. My views are entirely mainstream relativity physics. I’m not asserting anything unusual. As I have made clear several times now, I am questioning the view that interprets the relativity of simultaneity the way the BUH does. I see it as contrary to a fundamental tenant of SR that “now” is strictly a local concept, that simultaneity is virtual and a matter of geometric perspective.

            The BUH is an interpretation of SR that is contrary to what SR actually says.

            I agree there is no point in discussing it further.


          24. Wyrd, ‘mainstream’ means that an opinion is the dominant, conventional view. If your view is entirely mainstream then where is the list of supporting citations from professional physicists I’ve requested?

            From my reading, those who disagree about BU being a direct implication of the RoS are primarily philosophers rather than physicists. And they typically misunderstand consciousness—they tend to believe that our perceptions accurately represent the external world so that, for them, a feeling of flowing time proves the objective existence of flowing time. It doesn’t, any more than the perception of a red rose proves that the rose has a color.

            4-dimensional spacetime is an implication of RoS, not an opinion or ‘interpretation.’ An implication is a logical structure meaning ‘a consequence of’ as in p->q.

            So who, then, are we to believe about the reality of spacetime? Not being a physicist, I’m sticking with Einstein and the great majority of physicists. But, being a patient sort, I’ll continue to wait for that list of references of credible, professional physicists who support your opinion.


          25. I thought we were done discussing this.

            You’ll find what I’ve said about SR and simultaneity in any textbook that addresses SR in-depth. What you won’t find is assertions about points outside a given light cone being “co-real” — that part is an interpretation. In fact, you’ll find SR says nothing can be said about such points and that simultaneity is virtual and depends on your frame of reference.

            Consider frame M with three “simultaneous” events located at -10, 0, and +10, on the X-axis, and label them “A”, “B”, and “C”, respectively. Anyone in frame M claims A, B, and C, happen simultaneously.

            Frame J has a positive velocity relative to M, so anyone in frame J sees the same events as happening in sequence, first C, then B, finally A. On the other hand, frame K has a negative velocity relative to M, so anyone in frame K sees those events in the sequence A-B-C. The timing between depends on the relative speed.

            You’ll find examples like this in any textbook, and they illustrate how, in SR, simultaneity is virtual and depends on your frame of reference.

            I can’t account for why people believe the BUH. Or SUSY. Or string theory. Or the MWI or the MUH. All I can say is I don’t, and I’ve explained why.


          26. Mike, I took a look at The Hidden Reality, Chapter 8’s Note 12, which says in part:

            “To adjudicate between these two pictures, imagine the following. After you measure the
            electron’s spin about the x-axis, have someone fully reverse the physical evolution. (The fundamental equations of physics, including that of Schrödinger, are time-reversal
            invariant, which means, in particular, that, at least in principle, any evolution can be
            undone. …)

            I’m unsure just how one goes about, in fact, not just in principle, having “someone reverse the physical evolution.” And this seems to be an “in principle” on top of another “in principle.”

            Any clues?


          27. Stephen,
            None from me. Greene admitted the difficulty.

            The challenge, of course, is in carrying out the full reversal of a physical evolution. But, in principle, this is an experiment that would provide insight into which of the two theories is correct.

            Greene, Brian. The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos . Knopf Doubleday Publishing Group. Kindle Edition.

            The main point is that the theories make different predictions about what would be observed, and experiments along these lines are possible in principle, even if we don’t currently know how to do them. (If we did, I’m sure someone would have already.) No one knew how to test Einstein, Podalski, and Rosen’s assertions in the 1935 EPR paper until John Stuart Bell figured out a way in 1964.


          28. So all you need is a time machine, and you can prove or disprove the MWI! 😉

            There is also the implications of having to coordinate separate branches such that one world’s spin-up particle can be merged with the other’s spin-down. Not sure how such an experiment is possible without a time machine that affects multiple branches.

            In that footnote, Greene says something that rose my eyebrows: “In the Many Worlds approach, by contrast, both the spin-up and spin-down outcomes occur, so, in particular, the spin-up possibility survives fully intact.” I’m not quite sure what he means by that.

            In the MWI, the X-axis measurement has a definite outcome, up or down, resulting in two branches, both of which have a wave-function in a definite state. As Greene says, that means there is no knowledge of the other axes. So I’m not sure what he means about the “spin-up possibility” being intact.

            This example is what I was talking about above. The Z-axis measurement results in a wave-function in a definite state. The X-axis measurement does, too. Measurement, even in MWI, is one place time symmetry breaks down.


          29. I’m sure to Copernicus’ contemporaries, it would have seemed like magic was required to test his theory against Ptolemy’s. Auguste Comte couldn’t imagine how we could ever know the composition of the stars. And as I noted above, Einstein took grief about his EPR paper for engaging in metaphysical speculation.

            I don’t think coordinating between the branches, in and of itself, would be the difficulty. Remember that it would be the same experimenters and equipment in both branches, just seeing different aspects of the same quantum system. But it would require an experimental design that could recognize which branch it was in and alter its activity accordingly.

            On not understanding what Greene means, this actually is the central difference between Copenhagen and the MWI. Under MWI, there is no collapse. The wave function, with all its branches, continues to evolve according to the math. Anything else wouldn’t be the MWI.

            So under MWI, both spin states continue to exist. The measurement interaction decoheres them from each other, but they’re both still there. The trick of these experiments would be to test this prediction. If the two branches can be manipulated in such a way that shows they’re both still there, then MWI is right. Under Copenhagen (or any other collapse interpretation), the other branch no longer exists and this should be impossible.


          30. Understood, but I don’t see that that first axis measurement is preserved, even in the MWI. Both decohered branches have a wave-function that have destroyed the first measurement, rather than just one (under the CI) wave-function that has destroyed the first measurement.

            MWI doesn’t have collapse, but it does have measurement, and measurement puts the wave-function into a known eigenstate. (Or rather: multiple branches with multiple wave-functions each in one of the possible measurement outcome eigenstates. In this case two, Up and Down.)


          31. I think there are different ways we can account for it. Remember that under MWI, there is one universal wave function.

            We also have a subset, the wave function of the original quantum system being measured: the system-specific wave function.
            Under MWI, that wave function continues to exist after measurement, although with the branches related to the measurement decohered from each other, its overall evolution becomes much more difficult to track.

            As a practical manner, after measurement, we can choose to model the portions of the system we have access to as its own wave function: a result-specific wave function. Copenhagen reifies this final one as the one and true wave function of the system, but under MWI the others are all still there.

            The experiments Greene discuss assume that the original system-specific wave function is still a meaningful concept, and attempts to test its predictions.


          32. I’m afraid I don’t follow. What exactly does the “system-specific wave function” describe? The electron?

            If so, then yes, absolutely it continues. The point is the measurement changes it.


          33. Yes, the system-specific wave function refers to the electron, or whatever quantum object being measured.

            Definitely the measurement changes it. My point is that, under the MWI, the changes can be accounted for at a scope Copenhagen asserts no longer exists, leading to MWI specific predictions.


          34. How? What scope retains information about the first measurement?

            The two branches with Left and Right measurements, could have some from a spin-up or spin-down eigenstate or from any superposition of states. Once the X-axis measurement is made, where is the information about the previous Y-axis measurement?


          35. If we’re talking specifically about Greene’s proposed experiment, we’re at the limit of my knowledge. I know information is supposed to be conserved in QM systems, and under the MWI, everything is deterministic and reversible, so in principle it should be retained in the system-specific wave function. So if its evolution could be reversed, you should be able to get it back to the original state. It seems like doing this would require extremely controlled conditions, maybe a quantum eraser type experiment on steroids.


          36. There is a view that spin is a single bit of information, Up or Down, and spin axes are conjugate pairs, so it’s only possible to have a single bit’s worth of information — the spin Up/Down on a chosen axis. So no information is lost. That single bit is distributed among possible measurements.

            Per this view, this is why measuring another (orthogonal) axis returns a random result when spin is known on a given axis — that knowledge exhausts the knowledge possible of the system. It can only return a random result.

            The Schrödinger equation is deterministic and reversible so long as no measurement occurs. Measurements cause instant changes that I’m not sure are reversible even under the MWI. The MWI absolutely preserves all possible outcomes, but I seriously question that it’s reversible.


          37. Mike, as I read it, Greene’s “in principle” remarks would only allow us to discriminate between CI and MWI. I’m not familiar with the other 10 or so QM Interpretations (who is?) so it’s possible that the “in principle” reversing of reality might lend credence to some of those.

            Considering the nature of the obstacles to any “in principle” resolution, and the number of Interpretations that might be affected, I’m still comfortable with my view that all of the QM Interpretations are metaphysics (philosophy) rather than science. But with my commitment to rationality, if someone gets a handle on reversing reality before I die, I’ll revisit my opinion. And if you happen to encounter any signs of success in reversing reality, I’m sure you’ll post about it. In fact, you might reverse reality sufficiently on your own to post about it last week … 😉


          38. Stephen, fair enough. Some interpretations are philosophy, simply another way of talking about what Copenhagen talks about. But others, like the MWI, de Broglie-Bohm, or GRW, make different predictions about reality. As Greene pointed out, these are different theories.


  6. I like your Einstein quote, SAP; and the cartoon: it makes sense that our Creator would compare us to raisins, or to characters in a novel that He had written. Characters die in stories, but they “live” on in our culture. And yet, religious people are obsessed with living forever in heaven. So, it is a strange thing for Einstein to have said. It reminds me of the ancient Greek thought that we need not be worried about death because before we die we are alive and afterwards we will not even be there. Perhaps some people found that comforting because they wanted it to be comforting. Interestingly, that thought does not need a Block Universe.

    Liked by 1 person

    1. Thanks Martin. That Greek thought is the Epicurean take on death. I do personally find some comfort in it. Many Epicureans in the ancient world had an epithet on their tomb: “I was not; I was; I am not; I care not.”

      In the end though, I doubt the fear of death can ever be completely shaken. Evolution has just ingrained it too much into our psyche to be easily dismissed.


      1. Yes, we evolved to try to win, and death is the losing of everything. The fear of death seems to be a biological, rather than a philosophical matter. Although the associated idea of reality going on without us, as though we had never really mattered, does make more sense on a philosophy of time like presentism, less on the Block view. So, perhaps that was what Einstein meant, that reality did not go on forever without us, after our deaths, but invariably included us. (Although if so, then that would not be much comfort to those left behind.)

        Liked by 1 person

  7. I’m not a big fan of the block universe (or the “universe rigid,” as H.G. Wells called it). It makes perfectly logical sense, of course, but I feel like it’s a little too easy and simple of a model. In real life, physics keeps throwing these weird twists and quirks and kinks at us, which makes me suspicious of any simple and easy model of our universe.

    I guess you could say I’m applying a reverse Occam’s razor here: whenever we’re talking about the entire universe, I think the simplest model is probably wrong.

    Liked by 1 person

    1. Universe rigid? That’s an interesting phrase.

      I can see what you mean. It seems like any characterization of the universe as a whole will always be an extrapolation of what our most fundamental theories currently say. Maybe that’s all it can ever be. We can’t imagine ever taking a position outside of the universe, outside of space and time, and viewing the whole thing. I mean, we can pretend like we’re imagining it, but it will always be a fantasy scenario.

      Liked by 2 people

  8. Mike, the block universe is not metaphysics—it’s physics. Metaphysics is Philosophy and Physics is Science. When Parmenides, with his “what is, is” linguistic analysis, posits that all of existence is one whole and unchanging thing—that’s metaphysics.

    The block universe, on the other hand, is science. The Relativity of Simultaneity (RoS) is a cornerstone of the Special Theory of Relativity of 1905, which was geometrized by Minkowski in 1908. The block universe is a direct implication of the RoS, an implication of the form ‘if p then q’. In this case, ‘p’ is relativity physics, repeatedly confirmed for over a century, and ‘q’ is the block universe. Minkowski introduced the term ‘spacetime’ to describe the block universe and in Minkowski spacetime the extent of the temporal dimension is endless. Minkowski’s geometric formulation of spacetime is integral to the follow-on General Theory of Relativity which would have not been achieved without it. (Because of the morass of unfortunate connotations clinging to the term ‘time,’ I prefer referring to the dimensions of spacetime as length width, depth and tempth, where ‘tempth’ is the temporal dimension. By the way, the temporal dimension is not spatial—it’s temporal.)

    I suspect you’re very comfortable with the word ‘spacetime’ but, in your Presentist conception, the tempth dimension must be a zero-sized moving/flowing infinite plane that terminates existence for all 3-dimensional ‘past’ events behind it and brings into existence a universe-sized collection of 3-dimensional events that weren’t real before, all of this through an unidentified and undescribed mechanism. If that’s not your conception of Time, Mike, please let us know what it is. Were you to look for a scientific validation of the flowing time of Presentism, which I strongly recommend you do, you’d find nothing because no one has ever demonstrated the existence of flowing time or even proposed a credible experiment to test for it. Physics doesn’t recognize it, nor does physics recognize that ‘now’ you insist upon—there is no ‘now’ in the universe or in the laws of physics. Both flowing time and ‘now’ are completely subjective.

    To explain the origin of our feeling of flowing time I propose that it’s owing to naïve realism. Without rigorous investigation, our naïve realism tends to externalize our conscious perceptions—we believe the world is what we perceive it to be. For example, we tend to believe that objects in the world have colors and we’re equally sure that the world is a noisy place. But both of those beliefs are false. The world contains differing wavelengths of light which we experience as color. And the world is completely silent—it contains compression waves that we experience as sound. In both these cases, and many others, we mistakenly externalize our perceptions—the perceptual contents of consciousness. The same naïve realism applies to the belief in a flowing time in the world. In this case, however, rather than externalizing a perception, we mistakenly externalize the fundamental characteristic of consciousness—its flowing ‘movie-like’ presentation.

    Einstein concluded that spacetime directly implies what he called the “eternity of life”—the endless repeated experiencing of our lives which, like everything else, are permanently encoded in unchanging spacetime. In a quotation repeated in his New York Times 1955 obituary, Einstein identifies consciousness as the agent of that immortality (“… conscious life perpetuating itself through all eternity …”).

    But Einstein’s “eternity of life” and the Besso quote’s “[Death] means nothing” are not necessarily comforting. While contemplating the endless re-experiencing of a lifetime that’s mostly agreeable and full of treasured experiences and relationships might be comforting, it is conversely horrifying in the case of an immortal lifetime characterized by suffering. But emotions do not dictate either our formulation or our acceptance of scientific realities.

    For a thorough discussion of this entire topic, I invite you to download my paper “The Consequences of Eternalism” from:

    Liked by 2 people

    1. Stephen,
      Me calling the block universe metaphysics wasn’t meant to be a strong statement about it. I’m inclined to use that word because I can’t conceive of a test for it. But I don’t have a strong demarcation between theoretical science and metaphysics.

      Certainly I can understand the logic from special and general relativity that leads to that conclusion. But we know relativity and quantum mechanics are incompatible with each other. There will eventually have to be revisions. It’s possible those revisions may alter the logic. And, not having ultimate knowledge, we can never know whether we have the full picture. We can test our fundamental theories to increasing decimal points, but there doesn’t seem any way to know that we have the full picture. No scientific theory is ever final. All are provisional pending new evidence. So unknown factors could frustrate the logical predictions.

      Unless you know of a way to test the proposition. I’m very open to the possibility that things we can’t test today may be testable in the future. Are there any conceivable tests of the block universe in and of itself?

      It’s the “endless repeated experiencing” part of this that I struggle with. How is it being repeated? In what sense? Is the person reliving their life over and over? If not, then what exactly is repeating? Where is the repeat happening? What causes it to loop back to the beginning?

      It seems like that at the BU level, an experience is a static unchanging thing. It’s only for the pattern within the block (us) having the experience that it’s the dynamic process we refer to as “experience”, and we only seem to get one shot at it the sequence we call life.


    2. Mike, I’ve numbered my responses to address the separate issues you raise.

      1. On Metaphysics

      The Wikipedia definition of ‘metaphysics’ is “the branch of Philosophy that examines the fundamental nature of reality.” Categorizing the block universe as philosophy diminishes its scientific credibility whether or not that’s your intention. Black holes and gravity waves are also direct implications of relativity physics but they didn’t transition from Philosophy to Science by virtue of being experimentally detected—they were always scientific implications of relativity physics.

      2. On Testability

      Physicists can, and have, conceived of tests for the block universe so we amateurs don’t have to. Vesselin Petkov discusses both testability and confirmation in his paper “Is There an Alternative to the Block Universe View?” From the Abstract:

      The argument advanced in the paper is that if the world were three-dimensional the kinematic consequences of special relativity and more importantly the experiments confirming them would be impossible.” You can fetch the PDF at:

      Click to access Petkov-BlockUniverse.pdf

      I also recommend Petkov‘s closely related paper, “On the Reality of Minkowski Space”:

      Click to access V.%20Petkov,%20On%20the%20Reality%20of%20Minkowski%20Space.pdf

      3. On Relativity, Quantum Mechanics and the “Full Picture”

      As I’ve commented before on your blog, relativity and QM are not incompatible with each other. Quoting Petkov again:

      A consistent conceptual analysis … almost immediately identifies an implicit assumption —we have been taking for granted that quantum objects exist continuously in time although there has been nothing either in the experimental evidence or in the theory that compels us to do so.

      Further, the position that an incompatibility between relativity and QM is sufficient reason to discount relativity’s direct implication of the block universe doesn’t seem valid. If you believe it is, would you claim to a physicist that, because of a supposed incompatibility of relativity an QM, we should disbelieve the relativity of simultaneity, the distortion of spacetime by matter, the slowing of accelerated clocks and the reality of black holes and gravity waves?

      4. Your Questions

      Regarding the endless re-experiencing, you ask:

      How is it being repeated? In what sense? Is the person reliving their life over and over? If not, then what exactly is repeating? Where is the repeat happening? What causes it to loop back to the beginning?

      All of your questions are answered in my paper so I invite you to investigate therein. I’ll take a brief shot here, but the paper has the definitive answers. To begin, here’s an excerpt from the abstract:

      Our lives in the block universe are unchanging recordings in spacetime that do not ‘happen’ and have never ‘happened’ but, rather, encode a series of conscious streams which are continuously being experienced from every conscious point in the recording.

      As Einstein wrote, “… mind is immortal in the same sense as the body,” meaning that our consciousness is a permanent feature of spacetime. As such, our unchanging conscious moments are continuously and repeatedly experienced as components of a stream of consciousness. There is no “loop back to the beginning”—all of the conscious moments of all of the conscious organisms that have ever existed or will exist are being experienced always. As physicist Brian Greene wrote: “Every [conscious] moment is.”

      At the BU level, the configuration of certain static and unchanging events as functioning brains gives rise to consciousness, i.e., to dynamic experiences. But those experiences are not those static events—they’re the outcome of that configuration of static
      events. It’s true, as you say, that we only seem to get “one shot at the sequence.” That’s because our awareness is always confined to a single stream in the ongoing stream of streams. The continuous re-experiencing provides for repeated “shots.”

      After you’ve read “The Consequences of Eternalism” I’ll happily to address any additional questions about the material.


      1. all of the conscious moments of all of the conscious organisms that have ever existed or will exist are being experienced always

        ? The final “always” doesn’t seem to belong. Time (for a given observer) is a dimension along the block universe; it isn’t something you can pop out of the block, and then map the entire popped-out timeline onto each point in the block.


        1. That’s the tricky and sometimes confusing result of using tensed language in this type of discussion. Perhaps it’s more correct to say of all of those conscious moments that they never stop being experienced.

          Or similar … that’s the meaning I intended though.

          Liked by 1 person

    3. Mike, most physicists believe in the block universe because not doing so is equivalent to not believing in relativity physics. Even physicist Lee Smolin knows that relativity’s BU implication must be accepted until he can construct his Shape Dynamics replacement for relativity. He wrote:

      … Einstein’s theories of relativity are the strongest arguments we have for time being an illusion masking a truer, timeless universe.

      As far as I know, Smolin’s years’ long effort to reclaim his free will is still far from succeeding.

      Since you clearly reject the reality of the block universe, I would like to read your explanation of your alternate conception of Time, hopefully evidence-based. The only other option appears to be the wildly popular naïve realistic belief in Presentism with its flowing time, a conception which I find somewhat incoherent as I described in my original comment:

      … the tempth dimension must be a zero-sized moving/flowing infinite plane that terminates existence for all 3-dimensional ‘past’ events behind it and brings into existence a universe-sized collection of 3-dimensional events that weren’t real before, all of this through an unidentified and undescribed mechanism.

      The central issue in all of this is, of course, what is real?

      I don’t think a comment in this block universe post would allow sufficient space and focus to describe your belief properly so I suggest a new blog post on the topic. And you’d no doubt like to research further before posting. I’m certain it would be a most interesting post on a topic you don’t seem to have written about yet. I’m very much looking forward to reading it so Thanks in Advance!


      1. Stephen,
        1. As a prediction of existing scientific theories, I have no trouble calling the block universe science. I put it in the same category as the more grounded, but currently untestable, cosmology and multiverse predictions.

        2. Glancing at the Petkov paper, it appears to be an argument that SR implies the BU. I’m onboard with that. But SR is a special case of GR, and we know GR breaks down in some situations (like the center of a black hole).

        3. You’ve cited Petkov’s views on QM before. For me to buy a sparse existence argument, I’d need an accounting of what brings quantum objects in and out of existence. If the answer is any variation of “just is”, I can’t say I find it convincing.

        My point about the QM and GR issues is that we know the combination isn’t the final answer. Future revisions could alter any currently untested prediction, including the BU one.

        4. I read your interesting paper when it was Einstein’s Breadcrumbs. Is there a particular section in the new edition where this particular point gets addressed?

        Can’t say I’m a fan of Smolin’s presentism views. Or most of his views in general.

        “Since you clearly reject the reality of the block universe,”

        I’m puzzled why you keep coming away with that impression. My credence in it isn’t as high as yours, but I do see it as an interesting and very credible possibility.

        I don’t have well developed or strong views about time. I generally accept the account from GR, but I’m also open to the possibility it isn’t the final answer.


      2. Yo Mike!

        1. Well, “calling the block universe science” is significant progress from your initial “interesting metaphysical concept” but you’ve tossed in another unusual word choice with ‘prediction.’ The BU is an implication of SR, not a forecast or a prophecy.

        2. A glance at Petkov? You said you were unable to conceive of an experiment to demonstrate the existence of the BU and Petkov provides exactly that in those papers I linked. I’d like to know what fault you’ve discovered in your glance at his logic though. If none, then his conclusion—that conducting the experiments confirming the kinematic consequence of SR demonstrate the existence of the BU—is valid. If you disagree, what is the flaw in his argument?

        SR stands on its own. GR is irrelevant to the issue at hand. And, rather than GR breaking down, I’ve read that the center of a black hole doesn’t actually exist—the calculations yielding infinities means instead that spacetime itself has been abolished.

        3. The QM argument of Petkov (and Stuckey too) isn’t one of “sparse existence.” Instead, it maintains that a detected QM object has always been at the spacetime coordinates where it is detected and always exists at those spacetime coordinates. No QM object is a worldline but, instead, is a collection of discontinuous worldpoints along the temporal axis of spacetime. All events in spacetime are fixed and unchanging. Nothing in the BU comes into or goes out of existence.

        Another strange usage of the word ‘prediction’ here: “Future revisions [of GR?] could alter any currently untested prediction, including the BU one.” To repeat: The BU is a logical implication of SR, not a forecast or a prophecy.

        4. Perhaps you’ve forgotten the contents of “Einstein’s Breadcrumbs.” All of your questions are answered and explained in “Breadcrumbs” and I believe all of them are now briefly answered in just the Abstract of “The Consequences of Eternity.” For the full explanation of the answers you need to read the paper. There have been significant revisions since you last read a much earlier version.

        Lastly, regarding your comments about my request for a blog post describing your beliefs about Time:

        Smolin isn’t a Presentist. He believes in the BU because he’s a professional physicist who believes in relativity physics. In fact, my paper recommends his book Time Reborn for its lucid descriptions of SR, the RoS and the BU. Smolin has decided he wants his free will back but, as a principled scientist, he realizes that goal requires a replacement of relativity. That’s what his still unsuccessful Shape Dynamics effort is intended to do.

        Regarding my impression that “you clearly reject the reality of the block universe”: There are only two choices regarding the nature of Time. Either Time is 1) an objective flowing present mechanism or 2) the unending temporal dimension of spacetime. If you “generally accept the account from” SR (not GR) then you apparently accept ‘2’ … the existence of the BU, rather than considering it just a possibility.

        I believe the BU’s consequences for our understanding of the human condition are remarkably profound and disruptive and I’d appreciate the contributions of any and all thoughtful persons in the effort to understand them further and to contemplate an answer to the question that it poses: “What should we do?”


        1. Stephen, I’m just not the kind of guy who makes statements of absolute certitude, even for propositions I argue for. So I fear the best you’ll get from me about the block universe is that it’s very plausible.

          I downloaded your paper and will take a look a it.


          1. Mike, I heartily agree that absolute certitude is never possible. However, that will always be the case so because life is short I believe in drawing the best conclusions possible using the best information available in this era. On top of which I find rigorous neutrality to be emotionally unsatisfying despite its philosophical purity.

            As a for instance, I’m quite concerned about the impending devastation from human-caused climate change, even though only 95% (or whatever the figure is) of climate scientists concur. We will most assuredly destroy the world waiting for absolute certainty before acting. IMO of course … 😉

            Liked by 1 person

          2. Mike, even though you may not agree with high confidence about the block universe being our reality, the number of physicists who believe it is certainly compelling. You might be thinking it’s a somewhat probable to highly probable proposition, perhaps 70% to 90%. The knowledge that Einstein believed in the reality of the block universe would suggest the percentage tends towards the higher of that range. While we both realize that these sorts of beliefs can’t be 100% certain, the possibility is certainly high enough that we can meaningfully ask the question, “What does it mean if it’s true?

            I wrote in “The Consequences of Eternalism” (TCoE), “… how do we resolve our personal experience—the dynamic-view—with the unchanging reality of the universe—the block-view?” I believe TCoE presents a credible explanation that consciousness resolves those two views.

            Beyond that, TCoE is asking what the block universe means for our conception of the human condition. I don’t know if you’ve yet had time to read TCoE but if/when you do, I hope you’ll see that the human condition revealed by the block universe is hugely and disturbingly different from anything ever conceived, with ramifications for our conception of ourselves far beyond Einstein’s “eternity of life.”

            Because of those “huge and disturbing differences” I’d like to engage other thinkers to consider the explanations and ramifications I’ve identified. Each new reader of TCoE brings the possibility of learning other’s views—evaluations of the ideas I’ve presented and creative thinking that would move beyond where I’ve gone. In that regard, I’d much appreciate learning your thoughts. Perhaps your circle of acquaintances could enlarge that learning potential, so I would gratefully appreciate your passing it on if that’s possible. TCoE has been read by a physicist (Stuckey, who found no fault from a physics perspective) and a few philosophers, both amateur and professional, including Schwitzgebel. Frankly, Mike, the impression I get is that it’s more comfortable to turn away and take refuge in the familiar—it’s much easier to ignore the peril to our conception of ourselves than confront the ramifications of the block universe head-on.

            Liked by 1 person

          3. Stephen,
            On having high confidence, my assessment is that the block universe is plausible. I might even go so far as to say highly plausible. It’s the logical consequence of relativity. But I perceive that our only justification for it is that logic. We can’t test it directly. As a result, we can’t establish it as reliable knowledge in the same sense we can for special and general relativity, or other successful scientific theories.

            The problem with logical conclusions is they’re only as good as the knowledge foundations they’re built on. If evidence were found for an actual physical wave function collapse per something like GRW, I think it would undermine the block universe. We also don’t know what a successful theory of quantum gravity might do. And we simply don’t know what else we don’t yet know.

            Sorry to admit I haven’t had a chance to read through your paper yet. I did scan the conclusion section just now to see your points about the human condition. My own philosophical views lean Epicurean (in the ancient prudent-hedonist sense, not the modern gourmet one), so I’m not that far from what you discuss.

            But it does seem to me that, even if a changing dynamic reality only exists in our consciousness, I can’t see that we can escape it. We still have to live in this dynamic world. Ignoring it seems to produce painful consequences. We don’t have the option to simply stop making the best decisions we can on our guesses about the future, and instead act as a static pattern in the block universe. That makes the block universe an interesting thing to ponder intellectually, similar to the all the emergent classic worlds that are also plausible from the MWI, but neither strike me as having any significant effect on how I live my life, at least not based on what I currently know.

            Anyway, I’ll try to go through the whole thing sometime soon. Maybe some of your arguments will sway me.

            Liked by 1 person

          4. I appreciate your thoughtful response Mike. I suspect, however, that it’s we’re as likely to prove a physical wave function exists we are to construct a time viewer, a gadget that would reliably and repeatedly fetched information from a second in the future. That gadget would prove the future exists and confirm the block universe implication. The wave function experiment and the time viewer are both improbable science fiction, but at least the time viewer case can be imagined.

            I suspect you believe in flowing time, Mike, because everybody does. After all, it’s a cultural belief that’s learned from our earliest toddler years, although, of course, not explicitly. Lakoff and Johnson’s Philosophy in the Flesh devotes an entire chapter to time metaphors. The major time metaphoric group is called “The Moving Time Metaphor.” They provide these (and many more) examples that illustrate how we learn to believe in flowing time simply by learning and using language:

            The time for action has arrived. The deadline is approaching. … Thanksgiving is coming up. The summer just zoomed by. Time is flying by..”

            And, of course, it then just feels that way. So let’s briefly analyze our flowing time belief to determine if it’s a plausible belief (i.e., reasonable, probable) with the same scrutiny we used to determine the plausibility of the block universe implication. Let’s start out at 100% plausibility for flowing time. The belief is clearly rooted in perception—and we know how naïve realism usually works out … down to 90%? No one is able to define ‘time’ or flowing time—no one knows what it is … down to 50%? No one has suggested a mechanism by which the present is continuously ‘updated’ … down to 30%? As is customary, we turn to science to investigate and learn that physics cannot find an objective flowing time in the universe or any “moving now” … down to 10%? 0%?

            Doing that intellectually honest assessment of our two choices seems to lead to a conclusion that the timeless block universe is far more plausible than flowing time, regardless of whether it’s highly plausible or not. Mike, your stated downside for the block universe belief—the inability to test for it directly—applies to both proposals. This comparative plausibility analysis is compelling and suggests that we must take the block-view seriously.

            Aside from its explanatory value in physics, I believe the block-view can have a significant effect on how we live our lives even though we cannot escape the dynamic-view of consciousness, as you put it.

            The major implication of the block-view is that we should realize that our lives are constructed. No one is the choreographer of his life so no one should be judged at fault for anything. No one should be judged at all. Compassionately helped—decidedly yes, to the extent possible. Judged?—never. Our ‘selves’ are constructions as well, so we should stop being so enamored of the one we experience and valuing it over the selves of others. Most importantly, in my view, all suffering is eternal so we should do everything possible to avoid inflicting unnecessary suffering and hurting others’ feelings. Some suffering, like symptoms of illness and post-surgical pain, is unavoidable and even beneficial, but should be reduced as much as possible.

            But, since we know there is no free will, how can we achieve improvements? We know that we can change the way our brains unconsciously evaluate action possibilities with memes. Successfully implant a meme in childhood—that all suffering is eternal, for instance—and behaviors change. The saving grace, if there is one, is that the future is always unknown, so we have no reason to be discouraged.

            That’s some my thinking so far Mike. I could use some help.

            Liked by 2 people

  9. Reality is the most familiar thing there is, and you can quote me on that.
    You hard science guys have your heads screwed on all wrong, often.
    To living things, to beings that experience, and to language users, ‘the world’ is as much ‘us’ as it is ‘other’.
    And I thought you appreciated Dennett?


      1. In Dennett’s Intentional Stance there are three basic approaches for us to take: the physical, the design, and the intentional. All three are “reality” and compatible. Our “naive” perceptions involve all three of these, and especially the intentional. Too much intentional initially, but still “elbow room” for it now. He uses Conway’s “Life” to suggest how more complex vocabularies and ‘objects’ are possible and real.
        So, yes, our naive perceptions are accurate, more or less, which is about what you can say for the physical stance too. In ‘fact’, you and I communicating, now, is based in/on intentionality, as much as design and —- in an attenuated sense, physics too.

        Also, our “naive perspective” has not done so poorly in terms of evolutionary success. It’s like Dennett’s reference to the old quip, “If I’m so dumb, how am I so successful?”

        I hate the way you throw around the term “reality”. I guess you have the key to it? Pity us, we the naive, so out of touch! (And yet still here.)

        Please explain all I have missed. Seriously.

        Liked by 1 person

        1. Maybe I can find some common ground here by noting that we are in tune with the affordances and evolutionary threats in our environment. We’re in tune with the portions of reality and on the scale we need to be to survive in day to day life. (Although in the modern world, we face threats our ancestors never faced, threats we need a scientific insights to succeed against.)

          I do use the word “reality” to refer to everything that is real, and that is far more vast than what we can perceive. I’m not sure what other word we could use.

          Anyway, if the above isn’t sufficient, this is probably an area where we’ll just have to agree to disagree.


        2. “So, yes, our naive perceptions are accurate, more or less, which is about what you can say for the physical stance too.”

          I tend to agree, and I’m not sympathetic to views that suggest our mental models and perceptions are “off-center” from reality. I think, to the contrary, they are centered, but approximate and incomplete. I think of our perceptions as something of a wire-frame compared to the fully rendered version.

          It seems fashionable among some to say we’re wandering around mired in delusion and illusion, but exactly as you quote, “If I’m so dumb, how am I so successful?” Our perceptions have allowed us to be extremely successful.

          Liked by 1 person

          1. Naïve perceptions are accurate? Hmm. Not sure about that.

            What looks like a table is mostly empty space reflecting light waves that my eye receives and my brain interprets. It isn’t actually what it looks like. It isn’t really red or blue or white. That is in my brain. What it looks like may be useful for my brain to make use of it for supporting plates while I eat.


          2. I’m not sure if you’re responding to me or GregWW? The phrase you cited wasn’t mine.

            As far as what I said, the keywords are “off-center” (versus centered) and “wire-frame”.


        3. Greg, regarding your statement “… our naive perceptions are accurate, more or less”:

          Our perceptions are an internal representation of sensory events, a felt simulation of a very narrow range of the events in the world. The external world and our internal representation based on those events are not at all alike, as I pointed out in my earlier comment in the cases of light wavelengths vs. color and compression waves vs. sound. We do not see photons—we see light and color. We do not hear compression waves—we hear sound. Those are only two examples from our perceptual range, but our entire perceptual imagery is simulative and, strictly speaking, not at all ‘accurate,’ in that we do not perceive the world as-it-is.

          We do, however, tend to externalize our simulated version of the world and believe it to be the actual world. That’s naïve realism. The word ‘naïve’ refers to the human tendency to believe that we see the world around us objectively when we, in fact, do not. Of course our internal simulation of the world has evolved to be successful. In very many cases, if the experienced simulation fundamentally misrepresents the objective reality, you do not reproduce. You die.


          1. The world “as-it-is” sounds like a very metaphysical position. Then add in your contention for a consciousness ‘that is all the consciousnesses of all things that have con’ and it sounds like, well, not science and maybe religion.
            My comments have been based in the idea that we often fall prey to splitting “the world” too drastically into external and internal, real world and our representations of it , subjective and objective.


          2. Greg, I’m using the phrase “the world as-it-is” to refer to the world of phenomena as revealed by scientific investigation which has demonstrated that which the external world and our conscious representation/simulation of it are drastically different. I believe that’s an uncontroversial conclusion.


  10. I think it’s mildly comforting.

    When someone dies, they haven’t really ceased to exist. They are just living in another part of spacetime. It’s sad from our point of view, because we can never interact with them again and we will miss them, but they’re still “out there” in a sense. I am sorry for myself and their friends and family for losing them, but I am not quite as sorry for the deceased. Their existence has not been erased, even though it may have been shorter than might have been hoped.

    To put it another way, I am not better off than Darwin, even though I am alive and he is dead. I’m just living at a different time. I may well die younger than he did, so if more life is better than less, he is better off than I.

    Liked by 1 person

    1. I can see how that might be comforting. It doesn’t really do much for me, but if you’re contrasting it with the view that only the present exists, I can see how the alternative, that the past is utterly gone, can seem a stark and uninviting notion.

      On the other hand, not everything in the past or present is comforting. And there’s something to be said for the stance that we have at least some control over the future. I don’t see those views as necessarily incompatible, but it takes mental effort to reconcile them.


  11. Yah, like you just said above, and like I said earlier. Science is a human “instrumental” point of view. It is always in a relation to us, “to how we handle things on a day to day basis.” It’s no better than an art, but useful in a different and Limited Way.
    Gee, i’m sorry for you that you will never get outside of the universe and see it all at once. That means you are not God, as if gods ever did exist. You are just stuck with a “participants point of view” and from there “reality” is as familiar as it is “strange”!
    Sorry, don’t mean to sound snooty, but this is all just kind of Kantian, post-Kant stuff.


      1. Me? Spam?

        I would never suggest that belief in the the block universe could improve your love life … although there is Wells’ very suggestive “rigid universe” … 😉

        And I much dislike that canned mystery meat product too.

        Liked by 1 person

  12. I’m not afraid of death, I’m afraid of dying a long, agonizing, and painful death. When I was old enough to understand that everybody dies eventually, the idea of a long and painful dying process kept me awake all night, not death itself.
    I prefer a peaceful one.

    Liked by 1 person

    1. Hi Linda,
      I’m with you there. A quote often attributed (probably misattributed) to Mark Twain: “I do not fear death. I was dead for billions of years before I was born and did not suffer the slightest inconvenience from it.”

      That said, even if I knew my death would be painless, if I knew it was imminent, I’m pretty sure I’d be in serious distress.


    2. Linda, I also find the prospect of a “long, agonizing, and painful death” abhorrent. But, having just recently re-read Awakenings by Oliver Sacks, I was reminded that many people live a long, agonizing and painful life. You may have read the book (or seen the movie) in which sufferers of severe Parkinsonism following the encephalitis lethargica epidemic a century ago lived for years, and sometimes decades, trapped in excruciating physical positions with additional painful effects like oculogyric crises—“forced deviations of gaze”—where the eyeballs rotate to extreme positions. Gruesome pain.

      But years and decades of suffering can also be found in sufferers of schizophrenia, child abuse, people (usually women) trapped in abusive and destructive relationships, cases of deep depression and so on. And on and on and on, unfortunately.

      When I initially began to understand Einstein’s “eternity of life” I was horrified to realize that, in addition to its possibly comforting effects, it also meant that all suffering is eternal—it’s re-experienced endlessly. When I wrote “The Consequences of Eternalism” I was partly motivated by the idea that if everyone learned about our eternal suffering, then humanity as a whole might decide that its highest priority was to reduce suffering of all kinds. But, of course, sad to say, that’s just a childish dream.


      1. “Linda, I also find the prospect of a “long, agonizing, and painful death” abhorrent. But, having just recently re-read Awakenings by Oliver Sacks, I was reminded that many people live a long, agonizing and painful life. You may have read the book (or seen the movie) in which sufferers of severe Parkinsonism following the encephalitis lethargica epidemic a century ago lived for years, and sometimes decades, trapped in excruciating physical positions with additional painful effects like oculogyric crises—“forced deviations of gaze”—where the eyeballs rotate to extreme positions. Gruesome pain.”

        Oh yes. Very horrifying.
        I agree with the whole “long agonizing life” part.
        I always say there are fates worse than death. And the Parkinsonism thing you mentioned sounds like one of them.


  13. There is now. Now is where everything is at the moment.
    There is history. History is where everything was previously.
    There is speculation, speculation as to where everything will be soon.
    Everything can only be in one place at one time.
    There is not room for everything to be everywhere at the same time.
    Therefore, the notion of a block universe, where stuff is where it was and where it is and where it will be all at the same time, is false.

    Liked by 1 person

    1. Hey Marvin. Good hearing from you!

      I think you’re reasoning makes sense in a Newtonian universe, but has issues in one ruled by Special and General Relativity. You might want to check out the videos in the next post by Matt O’Dowd.
      He covers why it’s more complicated than it appears. It also gets at your other comment. For example, General Relativity establishes that gravity is not action at a distance. (It was under Newton, which many of Newton’s contemporaries criticized his theory for.) Under GR, gravity is the warping of spacetime, which propagates at the speed of light.


  14. I was curious, so I did the math while watching Nicole Wallace today. Assume Blair has a relative velocity to Alex of 300 m/s (1080 km/hr, 671 mi/hr), which is pretty fast but doable. Assume c=3×10^8 to make the math simple.

    That gives a γ of 1.0000000000005 — essentially one. The frame shift at 1 LS is 1 micro-second. (For reference, the Moon is 1.3 LS away.) If we multiply by 10^6, then there is a 1-second frame shift at 1-million LS. Which is 277.77 LH, or 11.57 LD, or 1.8×10^11 miles, or just under 2000 AU (just at the inner edge of the Oort Cloud).

    Whether that frame shift is 1-second into the “past” or “future” depends on Blair’s direction relative to Alex. Of course, Alex has the opposite view as Blair, because both views are relative, correct, and virtual (and about events over 11 light days away).


  15. Here’s a way to understand why SR does not mean the “future” is “co-real” because of how the surface of simultaneity undergoes a frame shift due to relative motion:

    Firstly, per SR, motion towards distant events shifts them into the apparent future of a frame at rest relative to those events. Motion away from distant events shifts them into the apparent past of the rest frame. (One implication of this is that distant events with space-like separation — i.e. no causal connection — do not have a definite time order. Motion towards them makes the more distant events appear to happen first; motion away makes the closest events appear to happen first. In the rest frame, the events appear simultaneous.)

    Secondly, also per SR, anything moving at light speed doesn’t experience time. The motion vector and simultaneity vector coincide, so all points along the (massless!) particle’s path are simultaneous. From the POV of something moving at c, the universe moves past it at c, which means the path has zero length.

    Now consider what this means for a photon that leaves a star 10 LY away. From our perspective, we know that a photon that arrives today left that star 10 years ago. It spent 10 years in flight while the universe evolved for 10 years. We know that photon is 10 years old.

    But from the photon’s POV, the moment it begins its journey, it sees its eventual destination as being zero distance away and, therefore, simultaneous with it. And, indeed, the Lorentz shift for something moving at c towards Earth shifts the surface of simultaneity such that Earth 10 years later (relative to the star) is simultaneous with it.

    This doesn’t mean that 10 year future is real when the photon is created 10 years ago. The surface of simultaneity is virtual. The universe evolves for 10 years while the photon is in flight, so when it finally arrives, sure enough, it’s simultaneous with today.

    This is all textbook SR, and it illustrates how simultaneity is virtual.

    We can extend this to a massive object moving just below c (also from a star 10 LY away). Imagine it’s moving very close to c, though. Then it will arrive somewhat later than 10 years — say it takes 11 years to make the trip (one year longer than light). The surface of simultaneity will also shift symmetrically. I haven’t done the math, but say, when the journey begins, the velocity shifts the surface 9 years (one year less than for light).

    If we imagine this fast object arriving here today, it left the star eleven years ago. When it left, the virtual simultaneity was +8 years, putting it at today’s -3 years, so the object initially saw 2017 as “simultaneous” with its departure. During its 11 trip, that point shifts forward until, when the object arrives at Earth, it has shifted up to the current moment and the object is simultaneous at its destination.

    Again, we know the object actually started 11 years ago and the universe evolved for 11 years during that time. When the photon began 10 years ago, or when the object began 11 years ago, today did not exist and was not “co-real” with the star 10 or 11 years ago.


    1. Wyrd, these three excerpts (in two separate comments) aren’t from the textbooks which you recommended, but are from the writings of professional physicists. They don’t concur with your concept of virtual simultaneity (a concept I’ve not encountered anywhere) and virtually real objects somehow becoming really real objects. It appears Paul Davies has provided the only possibility for your viewpoint to be correct—you actually have to be a solipsist, in which case Mike Smith and all of us commenting on his blog don’t exist.

      I’ll request, once again, that you provide credible references from professional physicists to support your “virtual simultaneity” views. Three supporting references would be fine.

      1. Physicist William Stuckey, Beyond the Dynamical Universe:

      As a consequence of RoS, consider an observer Alice in A passing an observer Bob in B.
      Except for one another, Alice and Bob will disagree on who exists simultaneously with them at that instant of time (call it ‘to-day’); people at rest with respect to Alice will exist simultaneously with her ‘today,’ while those at rest with respect to Bob will exist simultaneously with him ‘today.’ According to SR, the people in Bob’s plane of simultaneity will exist with people in Alice’s past and future, and vice-versa. So, Bob and Alice exist together ‘today’ and people in Bob’s ‘today’ exist together with people in Alice’s ‘tomorrow’ and ‘yesterday.’ Likewise, people in Alice’s ‘today’ exist together with people in Bob’s ‘tomorrow’ and ‘yesterday.’ If there is no empirical means of discrimination, then both Alice and Bob are justified in their designations of who exists with them ‘today,’ so their pasts and futures are as real as their presents

      2. Physicist Paul Davies, About Time

      If two events occur at different places (e.g., one on Earth, another in Andromeda), then the time sequence of the two events can be reversed, but only if the two spatially separated events occur close enough in time so that light can’t get from one to the other in the duration available. Consequently there can be no causal connection between the events, because, according to Einstein, no information or physical influence can travel faster than light between the events to link them causally. So reversing the time order in this restricted case isn’t serious: it can’t reverse cause and effect, producing causal paradoxes, because the events concerned are completely causally independent. However, this limited ambiguity in the time order of spatially separated events does have an important implication. If reality really is vested in the present, then you have the power to change that reality across the universe, back and forth in time, by simple perambulation. But, then, so does an Andromedan sentient green blob. If the blob oozes to the left and then the right, the present moment on Earth (as judged by the blob, in its frame of reference) will lurch through huge changes back and forth in time.

      Unless you are a solipsist, there is only one rational conclusion to draw from the relative nature of simultaneity: events in the past and future have to be every bit as real as events in the present. In fact, the very division of time into past, present and future seems to be physically meaningless. To accommodate everybody’s nows—Ann’s, Betty’s, the green blob’s, yours and mine—events and moments have to exist “all at once” across a span of time. We agree that you can’t actually witness those differing there-and-now events “as they happen,” because instantaneous communication is impossible. Instead, you have to wait for light to convey them to you at its lumbering three hundred thousand kilometers per second. But to make sense of the notions of space and time, it is necessary to imagine that those there-and-now events are somehow really “out there,” spanning days, months, years and, by extension, … all of time.


    2. 3. Lee Smolin, Time Reborn

      If the direction of the laws of nature can be reversed, then there cannot, in principle, be any difference between the past and the future—and the fact that we have very different relationships with the past and the future cannot be a fundamental property of the world.

      We’ll concern ourselves with two concepts from special relativity. The first is the relativity of simultaneity. The second, which follows from it, is the block universe. Each was a major step in the expulsion of time from physics.

      Let’s begin by agreeing that the present is real. We may not be so sure that the future or the past are real—indeed, the point of this argument is to find out how real they are—but we have no doubt that the present is real. The present consists of many events, none of which is more real than another. We don’t know whether two events in the future are real, but we will agree that if two events take place at the same time they’re equally real, whether that time is the present, past, or future.

      If we are operationalists, we have to talk about what observers see. So we assert that two events are equally real if they’re seen by some observer to be simultaneous. We also will assume that being equally real is what is called a transitive property; that is, if A and B are equally real, and B and C are equally real, then so are A and C. The argument then exploits the fact that the present is observer-dependent in special relativity. Pick any two events in the history of the universe, one of which is a cause of the other. Let’s call them A and B. Now there will always be some other event X that has the following property: There is an observer, Maria, who sees A to be simultaneous with X. And there is another observer, Freddy, who sees X to be simultaneous with B. …

      To understand why X must exist, you need to know not only that simultaneity is relative but that it is as relative as possible, in the following sense: One consequence of Einstein’s postulates is that if two events take place simultaneously for some observer, all other observers will judge them to be not causally related. It’s also true that if two events aren’t causally related, there will be some observer who sees them as simultaneous, thus simultaneity is as relative as it possibly could be, while respecting causality.

      If B is far in A’s future, then X must be far enough away from both so that no light signal could travel from A to X or from X to B. But the universe that Minkowski describes is infinite, so this is no problem.

      Now we can reason as follows: By the criterion I gave, A is as real as X is. But B is also as real as X is. So A and B are equally real. But A and B are any two causally related events in the history of the universe. So if there is any sense in which an event in the universe is real, that reality is shared by every other event. There is thus no difference between present, past, and future. What is real is all the events of the universe, taken together. So we conclude that the reality of the world consists in its history taken as one. There is no reality to moments of time or their flow.

      What’s powerful about this block-universe argument is that to entertain it you need only believe that the present is real; the argument then forces you to believe that the future and the past are as real as the present. But if there is no distinction between present, past, and future —if the formation of the Earth or the birth of my great great great granddaughter are as real as the moment in which I write these words—then the present has no special claim to reality, and all that’s real is the whole history of the universe.

      … the philosophically interesting features of special relativity do extend to Einstein’s theory of general relativity. The relativity of simultaneity remains true—and, indeed, is extended. So the philosophical argument I just outlined still holds and leads to the same conclusion: that the only reality is the whole history of the universe taken as one. It also remains true in general relativity that all the information that’s observer-independent is captured in causal structure and proper time. If the history of the whole universe is represented in general relativity, the result remains the block-universe picture.


      1. Trust me, I’m familiar with the argument. As I’ve said repeatedly, I think it’s wrong. I’ve explained why. The example above illustrates exactly why. Please stop parroting things you read in books at me and read and consider the example I presented.

        Do you deny that the photon was created 10 years ago and take 10 years to make the journey? Do you understand that, when the photon begins its journey 10 years ago, it sees the present day as simultaneous with it?

        However, suppose at the 5-year mark a Vogon Constructor Fleet destroys the Earth. When the photon arrives five years later, there is no Earth, and it can’t know that until it gets here.

        The only explanation is that simultaneity is virtual, which is exactly what SR ways. It explicitly says we can make no statements about events outside our light cone. The photon can’t know the Earth is here until it gets here.


      2. Wyrd, I’m not “parroting” professional physicists—I’m quoting them word-for-word. And the number of physicists who fully concur with the three I’ve quoted is legion.

        We must conclude that not a single professional physicist agrees with your “Virtual Simultaneity” theory, since you’ve not been able to provide, or even “parrot” any such references. Wyrdian physics apparently stands alone, completely unsupported by the relativity physics community. Wyrdian physics is “textbook SR”? Please cite the textbook titles.

        You wrote that ‘time’ is “something that flows” (i.e., Newtonian time) or something we are flowing through (i.e., no one’s time). Wyrdian physics doesn’t care that physics cannot find any evidence that a (zero-sized, therefore unitless) flowing-something exists. Neither physics nor biology can find the ‘now’ you claim is a perceived manifestation of that flowing-something. What sensory biology detects the flowing-something or its ‘now’?

        In relativity physics, as you know, ‘time’ is precisely the temporal dimension of 4-dimensional spacetime. Spacetime is defined (per Geroch) as: “the collection of all possible events in the universe—all events that have ever happened, all that are happening now, and all that will ever happen; here and elsewhere.” For a graphic of a light cone and the ‘Elsewhere’ which Wyrdian physics claims does not exist, please see this Wikipedia diagram:

        Your argument that nothing exists outside our light cone (i.e., that the Elsewhere isn’t co-real—doesn’t exist) appears easily falsified. Consider the expansion of our Hubble Volume by one-light year per year. Each year, a year’s worth of light from far distant objects finally reaches us and renders those light-years-distant objects observable. Wyrdian physics maintains that if we can’t observe something (the Elsewhere) it doesn’t exist—that those newly observable objects were not real before the light from them reached us. Since non-existent, not real objects cannot emit light, from what existing physical object did the newly arrived light originate?

        All of Wyrdian physics’ references to spacetime or any spacetime-related concepts, like the spacetime interval and its mathematics, are invalid because Wyrdian physics’ description of the universe is strictly Newtonian: three spatial dimensions plus a flowing-something—Newtonian ‘time’ which “… of itself, and from its own nature, flows equably without relation to anything external.” The claim that a non-existent flowing-something flows along the temporal dimension of spacetime, let alone flows at the speed of light, is inconceivable in relativity physics. Nothing moves in spacetime. As one expert in SR wrote, “From a ‘happening’ in three-dimensional space, physics becomes, as it were, an ‘existence’ in the four-dimensional ‘world’.” So Wyrdian physics disagrees with Albert Einstein, the original SR physicist!

        I’ll consider your example of “what a photon knows” after you’ve convincingly identified and explained the flaws in the co-reality descriptions provided by Stuckey, Davies and Smolin. Their explanations cannot be determined to be wrong simply because your explanation disagrees—you need to explain the flaws in their descriptions. I trust you agree with the transitive principle: if A and B are equally real, and B and C are equally real, then so are A and C. Or maybe you don’t.


        1. Mike, what syntax in a comment will fetch and insert a graphic inline, like the Wikipedia one I referenced? TIA …


          1. Stephen, normally if you put a URL to the image on a line by itself, if WP recognizes that type of image, it will inline it. The URL you put was to the Wikipedia file entry, although it ended with an image file extension, which apparently confused WP. I edited it to point to the actual image. Let me know if it’s not what you intended.


          2. Mike, from the Wikipedia “Spacetime” article where the graphic appears, when I right-click on the image using Firefox, I can choose either “Copy link location” or “Copy image location”. The File: one is the link location and the Wikimedia one is the image location. I learn something new every day … 😉

            Liked by 1 person

          1. Mike, I didn’t feel any heat. But the use of the word ‘parroting’, which means “to repeat exactly what someone else says, without understanding it or thinking about its meaning” might be running a mild temperature. 😉

            I never mean to belittle or offend anyone, but if I’ve gone over the line somewhere please let me know so I can apologize.


          2. I said parroting because, as far as I can tell from your responses, you don’t seem to me to have a deep understanding of SR or of what I’m saying. You just repeat the same argument that I’ve assured you repeatedly that I fully understand and don’t agree with. But seeing why I don’t requires a grasp of SR that goes beyond pop science books. It requires analysis, not quotes.

            The scenario above illustrates my argument nicely. You can demonstrate your facility with SR by engaging with it.


        2. “Wyrd, I’m not ‘parroting’ professional physicists—I’m quoting them word-for-word.”

          Which is exactly what “parroting” means.

          Did you notice the diagram you linked to labels the time axis ct? Above you claimed that I was ‘misconstruing’ the mathematics of SR when I discussed it. As you see from your own link, I know what I’m talking about.

          And you clearly don’t, so this “debate” is over. I’m out. Believe whatever you need to.


          1. Sorry to see you bow out with issues in the air, Wyrd. I was looking forward to your references. Looking for references myself, yesterday I Google’d “virtual simultaneity” and a few variants, but only turned up someone who believes the aether is real, a complex, equation-riddled discussion of quantum wave behavior, a few artists and several links with the two words separated.

            Yes, the time axis in the graphic is correctly labeled ct. As the Wikipedia article on spacetime makes clear, “The constant c, the speed of light, converts time units (like seconds) into space units (like meters). Seconds times meters/second = meters.” So ct is a measure of distance—its appearance on the time axis doesn’t mean that anything is moving.

            Until next time, amigo.


          2. ” So ct is a measure of distance—its appearance on the time axis doesn’t mean that anything is moving.”

            This is the sort of reply that makes me think you don’t understand the material. This point arose because I made an aside about about how, when we’re not moving through space, we’re moving through time at the speed of light.

            And the thing is, we always move through spacetime at the speed of light. When “standing still” all that motion is along the time axis. In the diagram you linked, that black vertical line is the observer’s motion through spacetime — specifically along the time axis at the speed of light.

            As you begin to move through space, you move less through time. But you always move at c. That’s what’s behind the spacetime interval. Your total speed through spacetime is constant, but it can be split between time and space. If you could move through space at c, then you’re no longer moving through time at all; your spacetime interval is zero.

            (Again, this isn’t any special physics on my part; it’s textbook SR.)


          3. Wyrd, I can understand the confusion because of a crucial omission in the video, which mirrors your own. The confusion disappears with the realization that, although the three spatial dimensions are measured by rulers, the time dimension is measured by clocks, which both you and the video fail to mention.

            One of the comments for that video referred to Brian Greene’s The Hidden Universe, so I located his description of the video’s content. In chapter 2, Greene writes:

            Einstein proclaimed that all objects in the universe are always traveling through spacetime at one fixed speed—that of light. … We are presently talking about an object’s combined speed through all four dimensions—three space and one time—and it is the object’s speed in this generalized sense that is equal to that of light. … this one fixed speed can be shared between the different dimensions—different space and time dimensions, that is. If an object is sitting still (relative to us) and consequently does not move through space at all, then … all of the object’s motion is used to travel through one dimension—in this case, the time dimension. Moreover, all objects that are at rest relative to us and to each other move through time—they age—at exactly the same rate or speed. If an object does move through space, however, this means that some of the previous motion through time must be diverted.”

            There’s the clarification that you and Sabine don’t mention: motion through time is measured by clocks. Clocks slow with acceleration—time dilation, meaning that objects moving through space relative to us age more slowly because their clocks tick more slowly. So the claim that we’re moving through time at the speed of light actually means—we’re all getting older at the rate our clocks tick!

            This entire issue is irrelevant to any discussion of the block universe.


          4. Your complaint is that no one explicitly mentioned time is measured by clocks? At this point you’re either trolling me or demonstrating a serious incompetence with spacetime physics.

            Dude, the first sentence of your own quote reiterates the point, and the whole quote goes on to say exactly what I’ve been telling you. I don’t know why you thinking bolding “they age” demonstrates anything — moving through time means things age.

            As you say:

            “Clocks slow with acceleration—time dilation,…”

            Firstly, acceleration is a different topic, General Relativity, which is out of scope here. It’s true that clocks, either under acceleration relative to an observer, or clocks in heavier gravity relative to an observer, run slower as seen by that observer. But that doesn’t apply here.

            What you mean in this context is that clocks moving relative to a given frame run slower relative to that frame. Which is true, and what’s being explained here is why that’s true.

            It’s true because we’re always moving through spacetime at light speed. If we’re at rest relative to a frame, all that motion is through time. Thus we move through time — or age, if you prefer — or our clocks tick, if you prefer — at light speed.

            Motion through space deducts from that motion through time — this is why clocks of moving objects appear to run slower. Their (relative) motion through space deducts from their (relative) motion through time.

            If your motion is entirely through space, i.e. at light speed, then you have no motion through time.

            This, as I’ve said over and over, is SR 101, textbook SR, and you don’t seem to have any grasp of the material. (At the same time you presume to say Dr. Hossenfelder and I are confused, which smells like trolling to me.)

            “This entire issue is irrelevant to any discussion of the block universe.”

            Yes, it’s a sub-thread from when you said I misconstrued spacetime mathematics. Apparently one PhD. theoretical physicist isn’t enough to convince you. I suggest you Go Ogle [do I move through time at the speed of light] for more.

            Maybe I can clear up another point for you: searching for “virtual simultaneity” isn’t likely to return relevant links because it’s not a term of art, like “proper time” or “spacetime interval” — it’s an understanding obtained from the material. What you do find in the text is that it’s not possible to make statements about points with space-like separation from you, and all points in the surface of simultaneity have space-like separation.

            One last point:

            “All of Wyrdian physics’ references to spacetime or any spacetime-related concepts, like the spacetime interval and its mathematics, are invalid because Wyrdian physics’ description of the universe is strictly Newtonian…”

            Either you’re trolling by deliberately misrepresenting me or you’re showing that you don’t understand me at all. It should be self-evident I don’t have a Newtonian view. At this point, until you can demonstrate you understand the scenario I presented above, I don’t see how this moves forward.


          5. Wyrd, my comments here are contributions to discussions to further understanding by exchanging viewpoints and to learn from those thoughtful and verifiable viewpoints that enlarge, refine or even replace one’s own conceptions. There’s no contest to see who is right. I infer that you’ve become emotionally engaged, however, based on the ad hominem’s in your replies: parroting, trolling, incompetent and ignorant, for instance. For me those judgments cause no offense (a waste of time and energy), but it would be helpful for our discussions if you could restrain the judgmental vocabulary. I’ve delayed posting this comment for a few days hoping you’ll be able to read it dispassionately and try to understand what I’m trying to communicate. If my sometimes clumsy scribblings cause confusion, just ask me to clarify or rephrase.

            Lightspeed: The statement that “we travel through time at the speed of light” certainly gets one’s attention in the “Golly!” sense, so I can understood why it’s widely used in YouTube videos. Note the “Golly!” comment “Thank you for totally blowing my mind!” below Hossenfelder’s video. My point is strictly about the units of measurement her statement implies. Look up what the word ‘lightspeed’ or “speed of light” means and you’ll find “300 million meters per second” or “186,000 miles per second” or similar. Substituting that definition into the statement in question yields: “we travel through time at 300 million meters per second.” What I’ve been trying to explain is that the statement “we travel through time at ruler-units per clock-units” is literally incorrect because temporal motion is measured in clock-units alone.

            I’ve never disputed the SR physics, just the literally incorrect statement. Below Hossenfelder’s video is a comment by Tudor Montescu: “Did you mean, by any chance, to say: ‘Do we travel through spacetime at the speed of light?’ (i.e. not through time). Because it was delta s / delta t = c. We instead travel through time at delta t / delta t = 1 second / second, as you yourself mentioned at one point.” An “object’s speed through time” is “the rate at which time elapses on its own clock,” as Greene wrote.

            Block Universe First, I’d like to answer your question of 11/1: “If the BUH is correct, why haven’t our senses evolved to have some sense of it?” The answer is, “some sense of it” has evolved—it’s called consciousness. However, as I’ve pointed out several times (and again on 11/3), “Our perceptions are simulations of sensation events and they don’t correspond to the sensation events, the physical reality.” There is no color or sound in the world, for example. The events in the block universe are fixed and unchanging, but our simulated representation of the block universe is a streaming, movie-like experience. That’s how consciousness operates. But, just like our perception of a red rose doesn’t mean that the rose possesses color, our perception of a movie-like flow of the world doesn’t mean that the external world (or an imagined objective time) is flowing. The block universe—the block-view—is the reality revealed by SR. The flowing perception—the dynamic-view—is our perception of that reality. If all consciousness vanished from the universe the dynamic-view would vanish with it.

            There are pathologies of consciousness, specifically one caused during the encephalitis lethargica epidemic a century ago, that slow, speed up and even stop that flowing presentation. When the flow of consciousness is stopped, the sufferer experiences the block universe directly but is unable to function. In several cases, the patients did not even appear to physically age, retaining a youthful appearance over a period of decades. This pathological condition might lend support from neuroscience to the physics view that the “flow of time” is not an objective reality. Based on autopsy results, the condition is believed to have been caused by viral damage to the midbrain’s substantia nigra which, when healthy, would seem to support the streaming continuity of consciousness.


          6. BU and Virtual simultaneity Wyrd, I searched for “virtual simultaneity” in a way that the words could appear separate from each other and in any order. That search should have turned up references that agree with your viewpoint even without the explicit phrase.

            You haven’t yet replied to my Hubble Volume question. I would think that your contention that our Hubble Volume contains everything that is real is likely not shared by astrophysicists. That contention is a corollary of your “light cone contains everything that is real” premise that nothing exists outside our light cone because we cannot know anything about objects until their light arrives. I suspect astrophysicists would explain that, as the Hubble Volume expands, we see objects for the first time that existed—that were real—in the presumed infinite universe prior to becoming visible. If you can locate any astrophysicists that support your contention, they might be able to rescue your virtual simultaneity hypothesis from falsification. Having knowledge about objects (light cone) and the reality of objects are two different things.

            On Newtonian Time: To disambiguate, the word ‘time’ has two quite distinct usages. The first is the “flowing time” usage (aka Newtonian time, “time as experienced” and so on). This usage of the word ‘time’ is your “flowing something.” The second usage of the word ‘time’ denotes the temporal dimension of spacetime, in my view an unfortunate word choice because of the confusions resulting from equivocation. Moving forward, I’ll instead use the word ‘tempth’ (like length, width and depth) to refer unambiguously to the temporal dimension of spacetime.

            Your statements about “time being fundamental” must be referring to the first usage—the Newtonian flowing time usage. Assuming that by ‘fundamental’ you mean either “existed prior to” or “something on which other things are based” (you’re welcome to clarify your meaning of ‘fundamental’), the idea that an objectively real flowing time is ‘fundamental’ in either sense of the word ‘time’ is, at best, an unverifiable philosophical belief. While it’s true that a number of Philosophers agree with your view that Newtonian flowing time is fundamental. But, as Einstein said to Henri Bergson, “The time of the philosophers is dead.”

            On the other hand, since spacetime is a single 4-dimensional geometry, neither tempth nor any of the three spatial dimensions can be sensibly thought of as ‘fundamental’—no dimension of spacetime could have preceded the others or formed a basis on which the other dimensions exist. Tempth also does not and cannot ‘flow’—it’s a measurable extent, a dimension of spacetime.
            So my statement about your conception of physics being Newtonian is based on your belief in time as a fundamental “flowing something” rather than a measurable extent. Perhaps my confusion is results from your equivocation in your use of the word ‘time’—you’re mixing the flowing time usage with tempth in your remarks.

            Wyrd, if you’re feeling agitated again, please reread this comment a few times and try to understand the meaning I’m communicating. Please ask questions if you would like additional clarification. And have a pleasant day! 🙂


          7. “Look up what the word ‘lightspeed’ or ‘speed of light’ means and you’ll find ‘300 million meters per second’ or ‘186,000 miles per second’ or similar. “

            Yes, 299,792,458 m/s. That’s how far a photon travels through spacetime in one second. Since a photon moves at light speed, all its motion is through space, and none through time, it covers that distance in one second.

            An object traveling only through time, but not through space, moves through spacetime at the same rate, but all its motion is through time (at light speed, which is a velocity — the differential of distance over time).

            “That search should have turned up references that agree with your viewpoint even without the explicit phrase.”

            Once again, it’s something that emerges from understanding the material.

            “You haven’t yet replied to my Hubble Volume question.”

            Actually I kind of have. Just expand my scenario above, which concerns a location 10 LY away, to any distance you like. The same logic applies. I’ll repeat it below.

            “Your statements about ‘time being fundamental’ must be referring to the first usage—the Newtonian flowing time usage.”

            Right, but then wrong. Newtonian time is the idea of absolute time, and the notions of SR and GR don’t apply. I subscribe to time as described by GR. (FWIW, I do think time is axiomatic and existed in some fashion before the Big Bang, and I agree that’s a metaphysical view.)

            This may answer your Hubble question, too: Consider the universe expanding from the Big Bang. Each particle, once formed, has a worldline and its own proper time, which depends on the local environment. The particles that ended up in, for instance, the Milky Way, have roughly similar worldlines and have aged (to use your word) roughly the same.

            With some variation. The particles at the center of the Earth, because of the higher gravity, are about 2.5 years younger than those at the surface. For that matter, the tip of Mount Everest is ever slow slightly older than the rest of the Earth. The differential is higher for Jupiter, and even higher for the Sun.

            Given that, we can reasonably assume that the particles of a system, say, 50 LY away have aged roughly the same time as we have (give or take). Despite that SR is explicit that we cannot say anything about events happening “right now” 50 LY away, it’s reasonable to assume that’s the case on the presumption those particles have had the chance to age up to now.

            But note that it will take 50 years to receive a signal that we can then, and only then, use to retroactively state that such and such and event was simultaneous with a time 50 years ago. Note that when that signal leaves for Earth, it sees 50 years into the future as simultaneous (as well as all points along the path). But obviously the Earth has to age those 50 years before it gets here.

            “…neither tempth nor any of the three spatial dimensions can be sensibly thought of as ‘fundamental’…”

            When I say fundamental, I mean, among other things, irreducible. Spacetime is a unified geometry, yes, but it still reduces to X,Y,Z,T axes.


          8. Wyrd, I should have replied here, but I mistakenly started a new thread, so please see my comment posted a few minutes ago. Thanks …

            Liked by 1 person

  16. Wyrd, I’ve been busy discussing definitions as facts-of-the-matter on Eric Schwitzgebel blog, but I did wish to reply to your comment of the 11/13.

    I can understand your defending the “blow your mind” version because it’s what you originally mentioned telling your friends. I quoted Greene above, that we are “… talking about an object’s combined speed through all four dimensions—three space and one time—and it is the object’s speed in this generalized sense that is equal to that of light.” But when talking about motion only through time, we’re no longer discussing it in that generalized “all four dimensions” sense.

    You wrote on the 13th: “An object traveling only through time, but not through space, moves through spacetime at the same rate, but all its motion is through time (at light speed, which is a velocity—the differential of distance over time)”, or the differential of ruler-units over clock units. But tempth is measured in clock-units … where is that distance you mention coming from?

    On the BU and “virtual simultaneity” you wrote that “… it’s something that emerges from understanding the material.” Wouldn’t it be better if the notion were explicitly stated in the material rather than “emerging” from it? I’ve searched through several books on SR and cannot find any mention of anything that corresponds to your virtual simultaneity, which I believe you defined as:

    “… simultaneity is virtual—we can make no statements about events outside our light cone until information about that event reaches us.”

    But what you are denying is co-reality which is existence, not knowledge. Co-reality is what RoS is about. Using the equations of SR, events futureward of us on the timeline can be calculated to exist by distant observers moving relative to us (towards or away), even though neither of us can have knowledge of, i.e. information about them—please reread Greene’s example of the distant alien Chewy. The knowledge of those futureward events only arrives several generations later but then Chewy’s descendants can confirm that his SR co-reality calculations were correct. Note that in your examples of a photon 10 LY away, we have to wait 10 years to know of it, but the photon and the Earth are co-real at the start of your examples.

    I have to conclude that your proof that the BU doesn’t exist is not convincing until, at a minimum, 1) you falsify Smolin’s co-reality logic (in my comment of 11/6) and 2) you provide credible physicist references confirming the validity of your virtual simultaneity views. As always, my conclusions about such issues are always provisional and subject to revision. I’d like to believe that applies to yours as well.

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    1. Hard pass. You’ve consistently ignored my argument, and it’s clear at this point it’s because you don’t understand it. Possibly you can’t understand it, so I see no point in wasting any more time on you.

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  17. Oddly coincidental and perhaps amusing, a very recent bottom-of-the page quote on from mathematician David Guaspari reads:

    Comparing information and knowledge is like asking whether the fatness of a pig is more or less green than the designated hitter rule.

    I agree with you wholeheartedly, Wyrd. I don’t and can’t understand your argument. I’ve looked for others who do and I can’t find any. Apologies for wasting your time.

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      1. You seem to be suffering from incontinent judgmentalism Wyrd. As I’ve explained, not being a physicist, I rely on the understandings of physics professionals when forming my own beliefs. My inability to understand your argument is not owing to limitations—it’s because your argument implies nonsense about what exists that conflicts with the physics community’s understanding of RoS and even light cones. I’ve provided their explanations, which you won’t address and cannot falsify … shall we interpret that inability as a limitation?

        Have a Happy Thanksgiving Wyrd.

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        1. My judgement is based on my perceptions, and I stand by it. Everything I’ve explained is textbook SR that any physicist would agree with. The only even slightly debatable claim I’m making is that the future isn’t real.

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