George:

When you say, "homogeneous surfaces in an expanding cosmology are locally rest spaces for the fundamental observers, but are not globally simultaneous as defined by radar", you use an operational definition of "simultaneity", according to which synchronous events that occur on clocks that have been synchronised by radar are called "simultaneous". In my essay, I've used the word "simultaneous" to mean the sets of events that take place on surfaces of constant cosmic time. I therefore make a clear distinction between simultaneity and synchronicity in my essay, and explain how that distinction agrees with intuition and special relativity theory.

In FLRW cosmology, a particular separation between space and time is made a priori in setting up the kinematical background geometry, along with the requirement that synchronous-and-simultaneous slices (defined by that separation) should be both isotropic (according to observation) and homogeneous (so that they're isotropic at every point, in accordance with the cosmological principle). Since the RW scale-factor doesn't necessaily have to satisfy Friedman's equations a priori, the standard cosmological model is not purely general relativistic, as it only becomes general relativistic when the metric is subsequently required to satisfy Einstein's equations---the eventual result of which tells us that the maximally symmetric surfaces should be filled with matter in the form of a perfect fluid, and that they must expand according to the description that's given by Friedman's equations.

You claim in your paper that the argument from special relativity for a block universe is irrelevant; but the model in which space is flat and a(t)=1 is an (elementary) FLRW model, and although it contains no matter, the kinematical description still has to be consistent with that of the more general models, which essentially results from the separation between space and time that's given a priori in the background metric. How can the unique congruence of fundamental worldlines be claimed instead to be defined by matter, when the dynamical equations of FLRW cosmology are derived subsequent to the kinematical restrictions on the background geometry? In order to argue effectively for an EBU, it is imperative---for logical consistency in physically interpreting the special case---to reconcile the elementary FLRW model with special relativity theory. This is what I've done in section 3 of my essay, the upshot being that the surfaces of constant cosmic time which I take to define simultaneity should clearly not necessarily have to be synchronous, which is one of the basic assumptions of FLRW cosmology. I would very much like it if we could continue discussing this over on my site, where I've already posted a response to the comment you left for me.

Daryl

Daryl,

With all due respect, George specifically stated above that he does *not* want to discuss his paper on time here! See above his post on 14 August which reads as follows:

"The issue of time has come up repeatedly in this discussion, even though it's not the essay topic. I've put up a paper on the archive today arXiv:1208.2611v1 [gr-qc], considerably strengthening my position about time as stated in my FQXI essay some years ago. I just point this out for those interested; but *discussion should take place somewhere else*, else this therad will grow out of hand!."* [emphasis added]

I'm hoping he'll be able to suggest another, more suitable venue for that discussion.

jcns

Hi Steve:

Thanks for your thoughts and views. You can define Free Will in your own way as you like. What I have been referring to the Cosmic Free Will as Cosmic Consciousness that is above and beyond time and evolution. A will that is constrained in time and evolution of brain, culture, and that could be chaotic is not a truly "FREE" but rather a constrained will bounded in time and body/brain.

But, if that is your definition, I have no problem with it.

My purpose of bringing the cosmic consciousness in this forum is to raise awareness of the scientists here towards the crucial missing physics in the current theories without which no Theory of Everything is possible. What I have noticed that most popular definition of Free Will is widely understood to be related to bodily evolution because of the dominant effect of biological evolution in science and our lives.

While there is a lot of discussion in this forum on what assumptions are wrong, these is a lack of emphasis or awareness of the what is critically missing from physics that is causing the CRISIS today. my posted paper --" From Absurd to Elegant Universe" tries to address what is missing to resolve the crisis rather than pointing to what are wrong assumptions only.

Best Regards

Avtar

Dear George,

I am very interested to know your views on the relationship between causality and time. To be sure we understand each other, let me say that I lean toward the view that time is a way of talking about causal relations. This is part of what I call the causal metric hypothesis, as I describe in my essay:

On the Foundational Assumptions of Modern Physics

Rafael Sorkin and the causal set theorists have a similar view, but with a number of important differences.

From my perspective, your essay seems to imply something quite radical, so radical that the simplest version of it is more complicated than the idea of multiple time dimensions. I mention this as an unlikely possibility near the end of my essay, but your treatment makes the idea sound quite reasonable.

Let me be more precise. As you well know, causality is sometimes regarded, at the classical level, as a binary relation on the set of spacetime events. By definition, such a relation is exclusively bottom-up; the relationships between two subsets of the universe are reducible to relations between individual events. In this view, the arrow of time corresponds to the order of events with respect to this relation. Multiple independent relations could be interpreted as multiple time dimensions in an obvious way.

What you seem to be claiming is that causality in fact involves binary relations on the power set of the set of spacetime events; i.e., that subsets involving multiple events influence each other in irreducible ways. In this view, it seems as though time might be understood as one-dimensional at the level of power sets (provided only one power-set relation is involved), but much more complicated at the level of spacetime itself.

One other point of comparison I would like to make is that a degree of holism already appears at the quantum level even if one restricts to binary relations involving only pairs of events, since the phases associated with transitions a priori depend on the entire universes involved (in practice, this would be somewhat restricted; the causal set theorists play around with axioms to this effect, but I don't go into these details). This makes me wonder if complicated power-set relations are really necessary at the classical level. Most of your examples are classical, so it seems that you think the answer is "yes."

I thoroughly enjoyed your thought-provoking essay. I'd be grateful for any remarks you might make on these issues.

Ben Dribus

    Dear Ben Dribus,

    I assume that Carey Ralph Carlson's essay on causal set theory gives a reasonable introduction to causal set theory and thus is helpful in interpreting your essay. My sense is that it is a mathematician's theory, or a physicist 'gone native'. As I understand it, you begin with time (as an ordered binary relation) and no space. Thus, to handle George's two-way causal flow you appear to need multiple time dimensions (or equivalent?)-- not a solution that would appeal to most physicists.

    Another non-physical mathematical interpretation involves quantum phases depending on "the entire universes involved". For a different physical understanding I refer you to my essay, The Nature of the Wave Function, which derives finite extent wave functions from a classical field and explains how these relate to probability amplitudes and superposition of [infinite] Fourier components. In such an approach there is no "quantum wave function of the universe", only local waves.

    My previous essays treated the universe as based on one physical substance (and *nothing else*) and assumes this substance (the primordial field) can evolve only through self-interaction. This leads to a scale-independent solution (hence, per Nottale, motion-invariant, ie, time-invariant) with no meaningful physical interpretation of time until the original perfect symmetry breaks. In this sense I begin with space and no time versus your assumption of time and no space.

    Although it's difficult to summarize this approach in a comment, the point I'd like to make in response to your above comment is that the essential nature of the primordial field (which turns out to be gravity) is to support self-interaction (since there is initially absolutely nothing else to interact with) and this (evolving as it has into the world as we know it) is at the root of the ability of our universe to support top-down as well as bottom-up causality.

    I suspect that you're rather committed to your causal metric approach but if you'd like a different take on this problem, I refer you to my previous essays, here and here.

    Although this comment addresses your specific comment, I hope that George also is interested in one fundamental explanation of the two-way causal nature of reality.

    Edwin Eugene Klingman

    Edwin,

    Thanks for the response to my remark. I don't want to clutter George's thread, but the discussion is directly relevant to his essay, so I don't think he'll mind if I reply here.

    I do not think the issues regarding time and causality raised by top-down causation are specific to approaches based solely on causal structures, nor to approaches involving configuration spaces. I mentioned the causal approach in this context not because it is my own, but because it simplifies the issue I was trying to get at, by removing independent structures that might clash with the causal structure, independent notions of locality, and so on. I mentioned configuration spaces because they seem to introduce top-down causality at the quantum level without requiring any radical new interpretation of the classical relationship between causality and time.

    The issue can be stated in a simple setting that has nothing to do with the origin of the universe or the microscopic structure of spacetime. Assume special relativity as a large-scale, low energy approximation. We call causally-related events timelike-separated for reasons that are obvious to every physics undergraduate. What, if any, corresponding time-related statement do we then make about larger subsets that are causally related in an irreducible way?

    If time in relativity is taken to represent a refinement of the causal order, then top-down causation clearly does require a radical new interpretation of time. If time merely corresponds to the lowest-level part of a power-set-relation, then this correspondence clearly endows the lowest-level part with unique significance.

    Either way, I am interested to know what George would say about the relationship between causality and time in a top-down paradigm.

    Dear Ben,

    As indicated by my mention of Carey Carlson's essay, I'm a neophyte to causal sets, with little knowledge of it or intuition for it. I suspected it was over-simplifying to say that you start with 'time and no space' since you've elsewhere commented that "the causal metric hypothesis includes the assumption that what we call time is just a way of talking about causality, and what we call causality is just a way of talking about binary relations on sets." This seems to jive with "If time merely corresponds to the lowest-level part of a power-set-relation, then this correspondence clearly endows the lowest-level part with unique significance."

    George mentions the brain in his essay, but does not directly mention consciousness. I suppose a materialist view supports a view of 'top down' causation that involves key strokes on a computer and other design tasks yet he does say that "The mind is not a physical entity, but it is certainly causally effective." As an exercise one can probably apply causal sets to the mind, but I believe that a more comprehensive perspective is required. Although these questions won't be settled anytime soon, I simply thought I'd point to my earlier essays that directly address these problems as I see them.

    I too am interested to know what George would say about the relationship between causality and time in a top-down paradigm, and will not take any more of his blog space with my own views.

    Edwin Eugene Klingman

    George,

    In your reply you don't point out what is logically wrong with my reasoning:

    ''If we understand something only if we can explain it as the effect of some cause, and understand this cause only if we can explain it as the effect of a preceding cause, then this chain of cause-and-effect either goes on ad infinitum, or it ends at some primordial cause which, as it cannot be reduced to a preceding cause, cannot be understood by definition.''

    You circumvent its irrefutable logic by asking me to explain how I go about my life, which has less to do with causality than with reason. Anyhow, I am not very interested in causality at macroscopic scale. If the antics of the moth can cause a hurricane but it depends on an infinity of other events whether the party is canceled or not, that is, if the moth only in retrospect can be accused of causing the hurricane, then it cannot be its cause at all. As far as I'm concerned, causality means that A causes B to happen with 100% certainty: to me ' approximately' causally is a contradiction in terms.

    The point of my essay is that if we live in a universe which creates itself out of nothing, without any outside interference, that is, without any cause, then in such universe fundamental particles have to create themselves, each other. In that case particles and particle properties must be as much the product as the source, the effect as cause of their interactions, of forces between them.

    If in a self-creating universe particles create, cause each other, then they explain each other in a circular way. Here we can take any element of an explanation, any link of the chain of reasoning without proof, use it to explain the next link and so on, to follow the circle back to the assumption we started with, which this time is explained by the foregoing reasoning, that is, if our reasoning is sound and our assumptions are valid. If we have more confidence in a theory as it is more consistent and it is more consistent as it relates more phenomena, makes more facts explain each other and needs less additional axioms, less more or less arbitrary assumptions to link one step to the next, then any good theory has a tautological character, fitting a self-creating, self-explaining universe. The circle of reasoning ought to work equally well in the reverse direction.

    In other words, I don't say that events aren't related, only that we ultimately cannot say, at least at quantum level, what is cause of what, what precedes what in an absolute sense as to be able to establish what precedes what requires that we can look at the universe from outside of it, which is impossible.

    Causality ultimately leads nowhere: if, for example, we invent the Higgs particle to cause other particles to have mass, then we need another particle to give the Higgs its properties, a particle which in turn owes its properties to another particle, and so on and on.

    As I argue in my essay, we'll never be able to unify forces, get rid of the infinities and contradictions of present physics as long as we cling to causality.

    Anton

      George,

      I see that your reply to my first post on your thread has disappeared. For the readers who want to understand my above reply to it, I again post your own reply to my comment.

      Author George F. R. Ellis replied on Jul. 23, 2012 @ 15:22 GMT

      Anton

      "Causality therefore ultimately cannot explain anything." If so please explain to me how you go about your daily life. If you are unable to cause any changes about you in your daily existence, then you don't exist as a person (and you certainly won't be able to get a job).

      I explained carefully at the start of my paper that there are always numerous causes in action, and we get a useful concept of "the cause" by taking all except a few for granted. This produces a valid local theory of causation. You don't have to solve problems of ultimate causation to understand local physical effects (e.g. heating water causes it to boil). Your complaint seems to be that if you can't explain the entire universe you can't explain such local phenomena. The whole practice of science disagrees with you.

      George

      Dear Ben and Edwin,

      thanks for these comments which are quite complex in their implications, and I can't do full justice to them at present. My view on the nature of time is set out in my paper here . I think that is compatible with top-down causation, which takes place at each instant in a local domain around each world line at all times.

      A key point I make in my essay is that top down effects don't occur via some mysterious non-physical downward force, they occur by higher level physical relations *setting constraints* on lower level interactions, which not only can change the nature of lower level entities (as in the case of the chameleon particles that might be the nature of dark matter), they can even lead to the very existence of such entities (e.g. phonons or Cooper pairs). This does not require multiple dimensions of time. So it is indeed a two-way causal flow which enables abstract entities to be causally effective (as in the case of digital computers) but does not violate normal physics. It is a largely unrecognised aspect of normal physics. The key issue you are both raising might be that in coarse graining physics one also needs a coarse graining of time to get the effective higher level laws. This certainly needs thinking about and I am not aware of much work on this.

      Two further key point I make are that (i) constraints are conserved by the dynamics of time evolution, indeed on some views effectively generate time evolution, so this is all compatible with how time works, and (ii) new information can arise by processes of adaptive selection; the outcome is not uniquely determined by the initial data because of noise and quantum uncertainty at lower levels. This is a top-down process because selection criteria are higher level entities. This is a core feature of how the brain can work in a rational way that transcends the lower level physics, without violating it.

      Edwin, you say "in such an approach there is no "quantum wave function of the universe", only local waves." I fully agree, that is what I say in my quantum paper here You carry on

      ``My previous essays treated the universe as based on one physical substance (and *nothing else*) and assumes this substance (the primordial field) can evolve only through self-interaction. This leads to a scale-independent solution (hence, per Nottale, motion-invariant, ie, time-invariant) with no meaningful physical interpretation of time until the original perfect symmetry breaks" Well as long as the symmetry breaks, time does indeed emerge. I believe its difficult for time to emerge from a timeless substrate, inter alia because of difficulties in then getting the same arrow of time everywhere.

      That's all I have time for now,

      George

      Dear Anton

      "As far as I'm concerned, causality means that A causes B to happen with 100% certainty" Well that's not this universe. Please read Feynman on quantum physics.

      "I am not very interested in causality at macroscopic scale". But that is what I am trying to explain.

      "The point of my essay is that if we live in a universe which creates itself out of nothing, without any outside interference, that is, without any cause, then in such universe fundamental particles have to create themselves, each other." But the word "create" has no meaning of there are no causes.

      George

      George,

      You wrote in reply to Edwin & Ben: "The key issue you are both raising might be that in coarse graining physics one also needs a coarse graining of time to get the effective higher level laws. This certainly needs thinking about and I am not aware of much work on this."

      I know Edwin eschews multiple dimensions; however, mathematical expressions of higher level laws, even in higher dimensions, do not forbid nonlocal causality in a finite space. That is, a closed logical judgment (mathematics) is 1 to 1 correspondent with a local physical result in the experimenter's measure space.

      This dichotomy -- between the local measure space of infinite range and the nonlocal domain of finite range -- led me to realize that Joy Christian's proposal using dichotomous variables eliminates the local-global distinction. That makes it fully relativistic ("all physics is local") and angle preserving in its application of topological orientability.

      Point is, that the general relativity interpretation of a universe finite in time and unbounded in space suffers no loss of generality as a universe finite in space and unbounded in time. This latter interpretation, though, fully embraces Minkowski space-time dynamics without ever having to refer to time as a physical phenomenon. Top-down causation is therefore continuous and locally real; continuous measurement functions are constrained by space-time topology (generalized geometry). I think this is consistent with your evolving block universe of spacetime evolution with no preferred surfaces.

      Best,

      Tom

      Yuri

      "We live in a universe that was born from a previous universe"

      - so how did that previous universe come about?

      Actually this has nothing to do with the topic of this thread. Your quote "we live in a universe which creates itself out of nothing," was not my statement, it was made by Anton. If you disagree please take it up with Anton on his thread.

      Dear George,

      Just a quick note to thank you for recommending Arthur Eddington's marvelous book 'The Nature of the Physical World.' I'm reading it now and enjoying it immensely. Having also just recently read Poincare's 'The Value of Science,' dating from 1913, it's fascinating to observe the evolution of thinking on many topics still of keen interest and still very much in a state of flux even today. It seems very much in keeping with the theme of this essay competition to observe the flow and, dare I say, "crystallization" (or lack thereof) of thinking on these topics over the past century.

      Fwiw, I'm personally convinced that we're currently living through and participating in what Thomas S. Kuhn would describe as a "crisis state" in physics. Would you agree? And if so, do you think that this is generally recognized and/or accepted in the wider physics community? I don't read or hear others talking in these terms, but I believe the evidence for it is abundantly clear; it's virtually a classic case, in my view. Exciting (and occasionally frustrating) times to witness.

      Regardless, thank you again for the book recommendation.

      jcns

        Hi jcns

        glad you are enjoying it. He was a great pioneer in astrophysics and cosmology, with a wonderful power of explanation. His book on the internal constitution of stars is still great reading, even though it was written before nuclear physics was understood. Physicists of his epoch did not deride philosophy, they realised its role as an underpinning to physical thought and took it seriously.

        Yes I do think there is a crisis in physics - but not all of it! One can get a very wrong impression of physics if you only read some of the over-hyped theoretical physics stuff, much of which seems in danger of losing touch with reality (for some people, models are more real than reality). But a vast amount of physics is absolutely solid, relating theory to marvellous experiments in materials science/solid state physics, nanophysics, quantum optics, biophysics, and so on - Nature Physics is full of the stuff, much of it very exciting. It is on the theoretical side,and in particular in relation to cosmology, where more and more extravagant hypotheses are being proposed with very little concern for usual constraints and/or for testability. "Phantom matter" and dark energy theories with p/rho < -1 are examples of the first; multiverses and theories of creation of the universe out of nothing are examples of the second. But physics has a great capacity for self-correction, and I think the more extravagant ideas will fade away and turn out to be ephemeral, as these ideas are tested and evaluated by the physics community in the long term, who hopefully will start to take philosophical issues seriously again. And I think the idea of top-down causation will gain traction and not fade away, even though it has so little support in the physics community at present. Ernst Mach and Dennis Sciama were early proponents of the idea, even if they did not call it such; present theories of the origin of the arrow of time are also of this kind; and it is starting to gain traction is some areas of astronomy, under the name "environmental effects". The exciting part is that it may help understand foundational quantum physics issues. Watch this space - but with a bit of patience!

        By the way, you quote Kuhn - have you read any Imre Lakatos? He has a more developed view of how changes of scientific research programs take place.

        George

        So it's previous universes all the way down. Are you claiming any of this is testable? Is this supposed to be science, or do you claim science does not need observations? How many universes back do you claim to prove exist, by some kind of observation - and what is the nature of the observation?

        Actually Penrose got there first: see his book Cycles of Time.

        I don't plan to read your correspondence with Weinberg, despite your demand that I do so.