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The nature of time itself.

  1. Dec 22, 2008 #1
    Do you think time flows or is static?
    Is time continuous or quantized?
    Is the direction of time uniquely defined and irreversible?
    Is time just a figment of our imagination?

    FQXI has an essay contest about the nature of time. All these points of view are championed by various authors, (some quite well known). It is too late to enter the contest, but anyone can vote on the essays (up until january 1st 2009) that seem to make the most sense.The current leader is an essay by Carlo Rovelli advancing the notion that time does not exist at the quantum level. Do you agree?

    Read the essays and cast your vote here!
  2. jcsd
  3. Dec 26, 2008 #2
    Do you think time flows or is static?
    If time flows, then I beg to ask, "at what rate does time flow?" Since such a question is nonsense, I believe time to be something that doesn't flow. I'm under the impression that we perceive our passage through time due to the construction of memories in a direction along the time coordinate such that we remember the 'past' and not the 'future'. This is intimately connected with your third question.

    Is time continuous or quantized?
    I don't know -- but quantum mechanics seems to roughly motivate a quantize time (and space).

    Is the direction of time uniquely defined and irreversible?
    Time most likely does not have an intrinsic direction (just like space). However, we conventionally give time an arrow by taking advantage of the fact that the entropy of our universe monotonically increases along some direction. This direction is conventionally taken to be 'direction of time.' An outstanding problem of cosmology is to understand why the entropy of our universe is increasing monotonically (i.e. why the universe didn't start with a maxed-out entropy).

    Other interesting issue is why we build memories along the same direction entropy increases; note that building memories is a process that locally lowers entropy.

    Is time just a figment of our imagination?
    In the usual sense, no; time is not a figment of our imagination.
  4. Dec 26, 2008 #3
    BTW there is an interesting theory that time on our brane can END (literally). Time will become space-like and our universe will be converted into 4-dimensional universe without time.

    For the brance in the bulk nothing dramatic happens, but for the local observers inside the brane the end of time looks exactly like in the 'Big Rip' scenario (antigravity increases, space curvature becomes infinite everywhere)
  5. Dec 26, 2008 #4
    It's hard to answer questions about an undefined or ambiguously defined term. Depending on how the word TIME is defined, the correct answer to each of the above questions could be any of the possibilities expressed in your questions. (Except, I think we can drop the figment of our imagination question. :smile:)

    So, what do you want the word TIME to refer to? Reality? The evolution of the universe? Motion? A 'measure' of motion? Clock readings? Indexes? Etc.

    I like to think of the word TIME as referring to indexes (subjective and objective) that are generated by correlating 'snapshots' of spatial configurations. The existence of a fundamental quantum of action would seem to put limits on the constituents of any index of reality, prohibiting an absolutely continuous record as well as limiting the content of any 'snapshot'.

    Anyway, thinking of TIME as an index, TIMING as indexing procedures, and A TIME as some specific subset of some index, then your questions might be answerable.

    Quantization isn't necessarily opposed to absolute continuity or contiguity or seamlessness at some fundamental level of reality that quantum theory doesn't deal with. But the concept of TIME as our individual and collective physical indexes is.

    We define motion in terms of two or more incongruent spatial configurations. Thus motion is a feature of TIME but not synonymous with it.

    A characteristic pattern of all of our indexes seems to be that the spatial configurations in any index evolve away from previously recorded ones. That is, the individual spatial configurations or 'snapshots' of any index are all unique, and they're ordered so that, say, configuration #100, is more like #99 than it is like #98, and more like #101 than it is like #102, and so on. #103 will be unique, but more like #102 than any others < #102. This seems to be a property of the evolution of the entire universe. So, our TIME indexes reveal a uniquely defined direction of change or motion. If this IS the defining motion and dominant energy of the universe as a whole, then all subspaces must follow this general trend -- in which case we might view, say, gravitational behavior not as something opposing the universal isotropic expansion, but rather as wave evolutions and interactions and complex wave structures following from it. And, until there's some physical evidence that suggests that the isotropic expansion is reversible, then we're justified in considering Nature as one big irreversible process.

    The statement, "time doesn't exist at the quantum level", might be a bit misleading (I can see the headlines now "Physicists Determine That Time Does Not Exist" :smile:).

    He wants to express dynamics as relationships between sets of variables without specifying which variables are the 'clock' and which variables are evolving as a function of 'clock' configurations. In effect, there wouldn't be any variables uniquely defined as 'time' variables. Or something like that. :smile:

    I just skimmed over the paper and a few others so far. Thanks for the link. Chrisc, a PF contributor who also has a paper there, The Heuristic Significance of the Principle of General Relativity on the Nature of Time, turned me onto the FQXi website a while back. I've been struggling with it. If you have a working understanding of GR maybe you could explain his model in terms that I can understand. The thread is: Time - A Dimension of Physics or Mathematics?

    I do think that there's some unnecessary confusion surrounding the physical meaning of the word TIME. In sorting out the semantics and ignoring what I think is bullsh**, I'm left with TIME as referring to our indexes (subjective and objective), our ordered records, of sensory data (from which we infer general facts and properties of an objective reality) -- no more, no less, and nothing other than. From this conceptual point of departure, it seems like a relatively straightforward (though not necessarily simple) task to fill in the details regarding the generation and qualitative aspects of TIME as it refers to physical events and objects.

    Also, what do you think about Rovelli's ideas?
  6. Dec 26, 2008 #5

    does "flows" mean time passes faster or slower depending on where you are in the universe?

    why not 1/c ?

  7. Dec 27, 2008 #6
    Time does not flow. Our interpretation of time flows; however these are not the same thing. It is our perception of things moving through space which creates what seems like a smooth flow of time. However if our brains were wired to notice much smaller incremental movements then we would see things more choppy. The flow is about how our brain inteprets movement and intervals between movement.
  8. Dec 27, 2008 #7
    I've been following your posts that posit time as an index. I think it is a good method for explaining the concept of time in physics as an operational, or the changing spatial configuration of observable variables in a system.
    This does not conflict with the model I presented at FQXI, but it deals with only the kinematic evidence of such configurations. The model I presented suggests the kinematics arise, as all kinematics must, from dynamics. The present dynamical laws can be understood as partial descriptions of a single, collective dynamic from which the evidence of time emerges. This single dynamic gives reason to and in fact predicts the second law of thermodynamics and much more.
    The difficult concept for most seems to be recognizing that dynamics "define" direction. The dynamic laws are time symmetric in the time symmetry of their equations, so we assume this means the dynamics the equations define are also time symmetric.
    This is not the case. If I said a body at rest tends to motion and a body in motion tends to rest, you would say I'm wrong since the evidence of inertia is well established as exactly the opposite of this. Being a fundamental law of dynamics, inertia holds from Newtonian mechanics all the way through to the QT of the Standard Model.
    So my statement is wrong, but it makes one aware there are four possible symmetries of mechanics that are resolved to one by the law of inertia. They are: rest tends to persist, rest tends to motion, motion tends to persist and motion tends to rest. That rest does not tend to motion is easily reasoned by most as requiring a spontaneous increase of energy, a contradiction of conservation. Similarly motion tending to rest requires a spontaneous loss of energy. That both motion and rest persist is a simple correlation of two principle laws - inertia and conservation.
    So although I would not suggest these laws are wrong, I am suggesting they collectively define a direction of the dynamics they govern.
    This is a simplification of what the model I presented follows with all dynamics.
    The direction of time emerges from the collective dynamics that are presently separate and partial descriptions of a larger dynamic of greater symmetry. The evidence of this direction is the evidence of the second law of thermodynamics, evidence that permeates all dynamical law.
    Time does flow as the culmination of all mechanics obeying all dynamical law. It will not flow if/when the universe reaches equilibrium.
    Time is a continuous process (see my essay for how) but EM is a finite, discrete cessation of this process which in turn makes the "strangeness" of quantum action a very rational and deterministic behavior of mechanics.
    The direction of time is uniquely defined and irreversible. The reversal of time would require the reversal of "ALL" dynamical law, i.e. a body in motion would tend to rest and a body at rest would tend to motion.
    Time is not a figment of our imagination, but appears so when the evidence of time is approached as separate and isolated evidence of each dynamical law, whereas it should be understood as the collective, resulting evidence of all laws.

    I think Rovelli's ideas are interesting in that they offer a framework that "side-steps" the problem of time. But I think the true nature of time will have to be more directly addressed to complete the Standard Model and remove all the hand made inputs, reveal the meaning of the coupling constant and remove the hierarchy problem.
    I think Julian Barbour's approach is a more direct handling of time in a relativistic framework. I like the simplicity of his approach as it offers a method of setting variables for my model, which is admittedly so deeply entrenched in a generally relativistic framework, knowing where to begin testing it would be impossible without Barbour's essay.
  9. Dec 27, 2008 #8
    I like the idea that time and gravity (maybe space) are all collective properties of matter.
    Last edited: Dec 27, 2008
  10. Dec 27, 2008 #9
    Time perception might be . I.e a flys time might be faster than a humans.
  11. Dec 31, 2008 #10
    What other sort of evidence is there? If we make a statement about the world, then we're required to express this in operational terms that reduce to positional variables, aren't we?

    Isn't dynamics inferred from kinematics?

    Yes, I agree. I see this fundamental dynamic as the isotropic expansion of the universe. As far as we can be concerned, there's no deeper process, since we don't have access to anything preceding or encompassing our universe.

    Our time indexes show a 'direction' of change because we live in an expanding universe.

    I think I understand what you're saying and agree with your conclusion that a single dynamic accounts for 'arrows of time', but I think that there's a simpler conceptual basis, a better heuristic, available than is expressed in your paper. Isotropic expansion as the fundamental dynamic accounts for a defining property of evolutions (time indexes) on all scales. In terms of spatial configurations, the general 'direction' is away from previous configurations.

    A 'universal time reversal' is just a meaningless grouping of words in a universe whose fundamental dynamic is isotropic expansion. Inertia is just bodies following the general expansion. Nothing moves contrary to the general expansion. There isn't any other 'direction' for things to move in.

    The deep nature of acceleration of macroscopic bodies is wave interaction. The deep nature of gravitational behavior is wave interaction. And the fundamental dynamic governing wave action and interaction on any scale is isotropic expansion.

    Anyway, that's the line along which I'm speculating at this time. :smile:
  12. Dec 31, 2008 #11
    ThomasT, I understand your interest in a fundamental dynamic and I know space-time expansion is an enticing candidate as it seems to imply a universal time via indexing, but expansion is not a local phenomenon since systems remain spatially constant under one or more forces. It is not in-fact a dynamic at all according to GR. GR originally included a cosmological constant to hold the universe static (an aesthetic preference at the time) because it predicted expansion not as a dynamic or driving force but as a consequence of the dynamics of GR.
    So if you stand back and look at the Big Picture, expansion is an isolated effect between systems under the influence of dynamics. The laws are meant to deal with what happens between the expansion in the regions of the universe where matter and the four forces are the dominant physics. In this sense if expansion were the direction of time, time would exist everywhere except where everything is happening.

    Kinematics are the evidence of dynamics. Measures of space and time provide the kinematical framework of observation. Once this framework (and its relative nature) was accepted by physics the only fundamental dimension left to provide the dynamics that give rise to the kinematics of space and time - was mass. The energy of mass has been the concentration of theoretical physics ever since.
    Whatever the successful model of mass will be (the Standard Model[Higgs field] is the culmination of all this work so far) it must provide the dynamic/s that drive kinematics and define the laws of mechanics. This does not mean the energy of mass is directly responsible for all kinematics, but it will play a fundamental role in the laws that govern all kinematics.

    What, in my opinion, changed all of the above was the discovery of kinematics on a universal scale that lack dynamics - the acceleration of expansion, the angular momentum of galactic bodies that require more mass than can be found. The discovery of kinematics that require a dark energy and dark matter throws a wrench in the present modeling of physics beyond what I think many are prepared to accept. In that the long search for a model of the energy of mass was not completed before it was discovered the universe consists of far more mass NOT in the form of matter than in the form of matter, suggests mass is not at all what we thought it was.
    If space-time is an extension of mass, and the success of GR suggest it must be, then it seems only reasonable if not necessary to consider the density of space-time is mass and capable of accounting for dark energy and dark matter as a simple relativistic measure.
    If this is the case, the local space-time of dynamic systems is not isolated from the expansion but is the antithesis of what we presently think of as expansion. Space-time condenses to mass and an astronomically large region of condensing space-time provides the dynamics otherwise conjectured as dark matter and energy.
    Time is then the local condensation of space-time which is measured as cosmological expansion.
    So your idea that time "is" the index I think is correct in the sense that the index is the kinematic measure of all physical change, but I think the direction of the index would show local condensation is interpreted as cosmological expansion.
    Of course this is all conjecture but it fits every test I've considered. I am not sure why everyone is so quick to trash the concept of condensing space-time yet so eager to accept expansion. If either exists, the other is a local, (frame dependent) relativistic measure of it.
  13. Jan 1, 2009 #12
    Chris, thanks, things are falling into place, so to speak. I think I might have a way of translating your "condensation of spacetime" into terms that I think in. But I need to think some more about what you've written, and it's New Year's Day, ... will hopefully be able to do some constructive nitpicking by this evening.
  14. Jan 3, 2009 #13
    Conceptualizing in terms of a unifying view of a fundamental wave mechanics that applies to all scales and a fundemental dynamic defined by isotropic expansion might never lead to viable calculational models (even if it's the right conceptual approach, and, of course, we have no way or knowing whether it is or isn't). Nevertheless, there are practical as well as conceptual problems with the mainstream approach.

    Isotropic expansion doesn't seem to apply to local phenomena or 'persistent' objects. But if you think of it as the fundamental dynamic, then the spatial constancy of various phenonomena, the emergence of ponderable physical objects, might be understood in terms of boundaried wave structures that conform to a fundamental, wave mechanical dynamic, and emerge via interactions within and across interfacing media.

    That's a problem, isn't it? A unifying fundamental conceptual picture can't emerge from GR and the Standard Model -- maybe because they're not fundamental. If everything were conceptualized in terms of a fundamental wave-mechanical dynamic, isotropic expansion, then all of the apparently scale-specific organizing principles and phenomena might be conceptually (even if not computationally) unified.

    The Big Picture I have is of an expanding wave shell (the boundary of our universe), which is the archetype for the basic behavior of any disturbance in any medium that's produced in and bounded by the expanding universal wave front. The stuff inside the wave front (you and me, our conceptions of time, etc.) emerges from disturbances in a very large number of particulate media following the same archetypal wave dynamic that defines the universal scale.

    I don't understand this.

    In my view, what we call inertia is a result of the expansion. Mass is a measure of inertia. So, mass is, at least indirectly, a measure of the expansion. No expansion, no inertia, no mass.

    This is compatible with my general conception of things. The kinetic energy of the universal isotropic expansion is the mother of any and all internal energies at any and all scales.

    How, exactly does all this work? Well, I haven't figured that out yet. :smile: And, the way things are going, it looks like I might have to abandon this conceptual approach. But not just yet. There are a lot of experimental phenomena to consider first, and more stuff to learn about various sort of waves in various sort of media, etc. I like the idea of the universe being a humongous explosion. Wrt certain 'explosive' disturbances in certain media (across a range of different sorts of initiating events) you can see something like 'inflationary' intervals and variable expansion rates and emergent internal structure, and so on. But this isn't a very popular idea. As Guth said on TV recently, if our universe is the aftermath of some explosive event, then it's an explosion like nothing we've ever seen. But of course, I think, the universal medium is, presumably, a medium like nothing we've ever seen either. And, if this fundamental medium is truly seamless (ie., nonparticulate), then we'll never see it ... ever. Anyway, the point is that maybe you can tweak the hypothetical medium and the hypothetical initiating event so as to get an expanding wave front from something akin to explosion and something akin to at least gravitational behavior emerging internally.
    Yes, this does seem to be true.

    If we thought of mass as a quantification of inertia, as a measure of an object's acceleration (or resistance to acceleration) wrt some standardized applied force, then why do the observations you noted require some different conceptualization?

    Is your 'condensation' synonymous with contraction?

    Is it possible to visualize your 'condensation' in terms of wave mechanics, interacting wave structures? The formation of massive, ponderable objects via "condensation of spacetime" is a bit hazy to me (as I'm sure most of the stuff I've been spewing is a bit hazy to you and anyone else who's happened to read it).

    I think the idea of cosmological expansion comes directly from observing astronomical bodies moving away from each other and us. And yes, I do interpret mass (local condensation) as a measure of a universally pervasive isotropic expansion.

    Do you consider 'local condensation' to be moving against the isotropic expansion?

    I promise I won't trash your concept of condensing spacetime unless I'm sure that I fully understand it (which I don't ... yet), and can give you good reasons why I might prefer some other approach. I might have spoken too soon in post #10 of this thread where I said that I think there's a simpler conceptual approach, a better heuristic. Well, of course there might be, but I'm actually undecided at this time. Yesterday I had one of those train of thought eureka moments about all this, but I didn't record it in any way and I've been feeling too lazy to reconstruct it. Too much turkey I guess.

    Anyway, who's "so eager to accept expansion"? You mean as a fundamental dynamic? I haven't found that to be the case.

    Do you mean, if both exist, then one is a local measure of the other? I agree with this, and, as noted above, I think that mass is a local measure of the isotropic expansion of the universe. I also think that what you're calling condensed spacetime is a way of referring to bounded wave structures, and that your 'condensation of spacetime' is the wave mechanics, whose fundamental dynamic is isotropic expansion, which produce these bounded wave structures.

    I'm in the middle of Huw Price's paper, and must read yours again.
  15. Jan 4, 2009 #14
    Let me answer this one question as I think it will answer most of your others.
    Sorry for being so long winded, it's not an easy concept to explain.

    The key to understanding this model of condensing space-time is unfortunately also at the core of the confusion many people experience when trying to grasp the application of the principle of general relativity in observable mechanics.
    It is one thing to say the principle of relativity is at work in our quantitative measures of mechanics, such as the relative measures of space and time. It is a completely different yet not so difficult thing to say the principle of general relativity is at work in our "qualitative" measures of mechanics. The difference being a matter of pragmatic, scientific method in discarding our notions of what we "believe" to be real and what we "measure" as real.
    In terms of SR, when I measure the motion of light via this ruler of time I call a watch, I will find the speed of light is constant. But as the geometry of SR demonstrate so accurately, my watch is not a consistent ruler with respect to every other watch not in my frame of reference. So, am I measuring time or am I measuring space?
    One cannot say "I am measuring time, but as SR holds we know some portion of my measurement is actually space".
    Scientific method does not provide loop-holes where we can discard the method in favour of what we think is true.
    If I measure time, it is time, nothing else. That you may measure a greater portion of space than I do, tells us only one thing and that one thing MUST be scientifically accounted for - a quantitative measure of dimension is a qualitative identification of dimension.
    As the density of space-time (the rate of time per unit Length) changes, what "is" space and what "is" time changes. This is not an illusion explained away by SR, it is a hard-core fact of dimension.
    Now consider the same pragmatic approach to space, time "and" mass. Mass changes, Time changes and Space changes, all change "qualitatively" with respect to motion and proximity to mass.
    Unless we are willing to throw out the laws of conservation and with them Noether's theorem, we must agree there is a transformation of dimension that affords you the ability to measure mass where I measure space-time.
    The mechanism or the process that is common to and affords relative measures of, all these transformations is motion.
    Whether it is constant relative motion or accelerated motion, motion changes our measure of dimension.
    If we are not in motion with respect to a massive body but the space-time extending from and as the mass of that body changes with proximity to that body, well, there is no point in denying the obvious, space-time is in motion with respect to us and that body.
    It sounds so naive it is easy to dismiss, but in the proper relative geometry of all three dimensions it works exactly as predicted by GR and solves so many more questions in physics I will not let it go unless it fails a test of falsifiable mechanics.
    This is a simplified example of the principle of general relativity that hopefully helps explain the basic model.
    My comments above regarding expansion might now make more sense when you ask - if, on a cosmological scale, space-time is expanding and on a local scale space-time is condensing, where would we draw the line between expansion and condensation?
    We wouldn't, we couldn't - one is a relative measure of the other. If my frame in a gravitational field is an accelerating frame, yet I am not in motion with respect to the mass generating the field, what is moving? If a distant galaxy is at rest with respect to ours yet the space-time between us is expanding, what is moving? Put simply, if all space-time condenses to and as the creation and persistence of mass-energy, the space-time of cosmological scales will be measured to expand as a relative measure of their local condensation (from our perspective) yet the masses will remain at rest wrt each other.
  16. Jan 8, 2009 #15
    Thanks Chris, I still don't understand the concept of condensing space-time, but, as time permits, I'll try to eventually nitpick my way through your latest post (I've read it twice, but haven't decided how to order my questions and comments yet). In the meantime, maybe you could work on a sort of 'condensing space-time for dummies' for me and others who might be having problems with it. :smile:

    I think I need a short break from thinking about TIME for a while (even though I have a definition of it which satisfies me, sorting out the semantics of different approaches is wearing).

    Also, there are a couple of new threads on the meaning of Bell's theorem and the violation of Bell inequalities. This is another area that has vexed me for years, so I'm going to explore the links to papers and ponder the comments in those threads.
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