jcns,

Thanks for reading my essay and commenting. Indeed, presentism is an old theory, and one that's been challenged by a number of philosophers, particularly in light of consequences from relativity theory. Therefore, the task I took up was not so much to expound the idea directly, but to reconcile the corresponding intuition with special relativity, for the purpose of eventually supporting the similar interpretation of a different relativistic description, in which that would be less obvious.

Since you're of a similar mind as I am, I thought you might appreciate a quotation from Seneca, which to me provides a clearer description than anything I've read elsewhere:

`Our bodies are hurried along like flowing waters; every visible object accompanies time in its flight; of the things which we see, nothing is fixed. Even I . . . , as I comment on this change, am changed myself. This is just what Heraclitus says: ``We go down twice into the same river, and yet into a different river.'' For the stream still keeps the name, but the water has already flowed past. Of course this is much more evident in rivers than in human beings. Still, we mortals are also carried past in no less speedy a course; . . . the universe, too, immortal and enduring as it is, changes and never remains the same. For though it has within itself all that it has had, it has it in a different way from that in which it has had it; it keeps changing its arrangement.'

Good luck to you, too, and thanks for the references.

Daryl

Dear Avtar,

I'll try to pick through the few things I think you have mixed up about my argument, according to your first statement. First of all, by the word `critical' in the title, I meant to indicate careful analytical evaluation, and not simply to pass negative judgement on standard cosmology. Indeed, the one argument is meant to provide physical motivation for the assumption of an absolute cosmic time in relativity, only not as it is given in the RW line-element, which further sets the corresponding present as actually being synchronous with fundamental observers. I also agree with the description of an accelerating universe, as this is the natural tendency of a universe that expands through the `de Sitter effect'. But there is nothing about standard cosmology in that last sentence, except a hope that the model would be empirically equivalent, according to the result stated above that; i.e., SdS is not isometric to RW, but I think it may be empirically equivalent to the particular FLRW model we observe.

I will try to look more closely at your paper.

Daryl

Well, I guess you've got your opinions and I've got mine... On second thought, I do tend to agree with the last one.

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  • Post #14

Daryl

I would prefer none of us to have opinions, this is supposed to be science. Some statements may prove to be wrong in due course, but so long as they were correct given knowledge at that point in time, this is the best we can do.

Paul

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  • Post #15

Hi Daryl,

Thank you for the quotation from Seneca. And yes, I'm certainly aware of the Presentism versus Eternalism debate which can be traced back to Heraclitus and Parmenides. The point I've tried to make in several essays which I've written for these FQXi competitions and elsewhere is that there is an actual correct answer to this ancient debate! We need not continue to debate the question forever! This is not the same as debating how many angels can dance on the head of a pin! The correct answer, moreover, has important implications for our view of reality and for scientific theories which are based on our view of reality.

I fully understand that you're probably far too busy to follow up on every reference which is sent your way. Nevertheless, I hope you might at least find time to read the following abstract from my essay Toward a Helpful Paradigm for the Nature of Time:

"Abstract: Throughout recorded history, there has been a glaring lack of consensus regarding the nature of time. Not only is the topic a knotty one, it also has been made to appear more arcane, complex, and daunting than necessary by an insufficiently careful use of language. This paper offers definitions for what are called here 'particular times' (particular configurations of the universe), as well as for 'the flow of time' (the evolution of the physical universe). These lead to a new and helpful paradigm for the nature of time, as well as to falsifiable conclusions which are distinctly different from -- and mutually exclusive from -- conclusions which generally are believed to stem logically from the operational definition of time (time is that which is measured by clocks) upon which much of the edifice of physics is founded. "

This is not merely some intellectual exercise in loosey goosey philosophy or metaphysics! There is a correct answer. For example, time travel either is or is not possible; we can't forever continue to have it both ways. Reasoning based on special relativity allows for the theoretical possibility of time travel. Reasoning based on the view of time presented in my essay does not. This is a real and important difference. Moreover, it is potentially falsifiable.

jcns

Dear Daryl:

Thanks for clarification of the title. There are some other serious consistency problems with the concept of an absolute and unique cosmological time:

1. An absolute cosmological time implies an absolute location wherein the Big Bang occurred. The open question is to identify this unique location in empty space of the universe, which would be the center of the universe. Widely accepted cosmology theories, consistent with observations, are based on isotropic universe, which is independent of a unique location as the center of the spherically expanding universe.

2. Another widely used assumption is that when we look into the far field galaxies, we are looking into the early universe where the location of the Big Bang and the center should reside. On the other hand, the Hubble observations imply that we are at the center of the universe since the universe is expanding spherically and symmetrically all around us. Hence, the center and the edge of the universe, implied by an absolute cosmic time, can be flip-flopped and are impossible to define.

3. Since time t=0 represents the Big Bang Singularity, there are well-known questions and presumptions about what was before the Big Bang that seemingly represents a supernatural creation out of nothing violating the laws of conservation.

4. Clocks only measure the time interval, while the absolute time t=0 can be arbitrarily set (as in different time zones) by the observer. Where is the unique cosmic clock located in the universe and who set it t=0 at the instant of the Big Bang?

Again, as described in my paper, the observed universe and galactic expansions can be explained without any explicit considerations of the absolute cosmic time or clock. Hence, the paradoxical presumption of a unique cosmic time may be scientifically unnecessary and irrelevant.

Sincerely,

Avtar

    Avtar:

    Your comments suggest to me that you lack an understanding of the basic concepts of cosmic time and cosmic expansion. A few quotations from Eddington's Expanding Universe might help you to better understand expansion:

    `The lesson of humility has so often been brought home to us in astronomy that we almost automatically adopt the view that our own galaxy is not specially distinguished---not more important in the scheme of nature than the millions of other island galaxies...

    `When the collected data as to radial velocities and distances [of these galaxies] are examined a very interesting feature is revealed. The velocities are large, generally very much larger than ordinary stellar velocities. The more distant nebulae have the bigger velocities... The most striking feature is that the galaxies are almost unanimously running away from us...

    `The unanimity with which the galaxies are running away looks almost as though they had a pointed aversion to us. We wonder why we should be shunned as though our system were a plague spot in the universe. But that is too hasty an inference, and there is really no reason to think that the animus is especially directed against our galaxy. If this lecture room were to expand to twice its present size, the seats all separating from each other in proportion, you would notice that everyone had moved away from you. Your neighbour who was 2 feet away is now 4 feet away; the man over yonder who was 40 feet away is now 80 feet away. It is not *you* they are avoiding; everyone is having the same experience...'

    The description given by the RW metric is of an isotropic and homogeneous (i.e., maximally symmetric) three-dimensional universe that multiplies in cosmic time. When the scale-factor that describes the form of this multiplication of maximally symmetric space is equal to zero, space is singular---i.e. it has zero extent.

    Please consider Fig. 1 in my essay, which graphs the evolution of Weyl's `de Sitter cosmology': at $t=-\infty$, all worldlines converge at a point; however, in the first instant of time space is infinitely large, with comoving geodesics distributed throughout Euclidean space that exponentially expands in cosmic time (Eq. (1)).

    Just about everything you've said in point 1 is incorrect. The standard model assumes maximally symmetric space that expands in cosmic time, which is, moreover, the proper time of all fundamental observers. Those *are" the basic axioms of standard cosmology, so to say that it only assumes maximal symmetry of space, or that maximal symmetry and cosmic time are mutually exclusive, is just wrong.

    On 2, there's no centre as you've written, just as there's no centre to the surface of a sphere or an infinite plane. When we look at distant galaxies, we are perceiving them as they were at earlier epochs, due to the finite speed of light. We don't take observations of isotropy to imply that we're at the centre of the universe, since we assume homogeneity as well, according to the cosmological principle.

    On point 3, t=0 is a big bang singularity in any model where the scale-factor, a(t=0)=0. In others, like the de Sitter cosmology mentioned above, it may be different. Since the scale-factor is a *scale*-factor though, the definition is arbitrary. What matters is the model that's been empirically constrained, which tells us that the big bang occurred 13.7 billion years ago, and how it has expanded since then. It takes two points to set a scale. The rest of what you've said in this point has been discussed a lot by other people, and I'd prefer not to get into it with you.

    On 4: see what I've written about point 3. Then, as described by the standard LambdaCDM model, which is a very successful empirical model, the big bang is at t=0---i.e. 13.7 billion years before now---on the clocks of *every* fundamental observer in maximally symmetric space. t=0 is not just an absolute time, though: the coordinate t is the common time held by each of these fundamental observers.

    Daryl

    J. C. N. Smith,

    `Reasoning based on special relativity allows for the theoretical possibility of time travel.'

    If you read my essay, you'd know that I disagree with that statement, as I see more reason for an interpretation of the theory in which time travel is identically impossible. You would also know that I already agree with the thrust of the argument in your essay, as well as much of what you've written. However, I hope you'd also see that I disagree with the notion that the changes we observe *are* the flow of time, since then the Universe (the present, the particular time, as you've called it) might not equably endure, which I think has to be a prior aspect of our existence.

    You've cited Augustine's Confessions: I'd refer you to the parts where he discusses the length of a day as 24 hours, regardless of whether the Sun stays still for a time or runs its course in only twelve, as well as the different durations of syllables. These are the types of reasons why I think time has to describe the equable endurance of a three-dimensional present. This is why I've described the present as real, and the past and future as purely ideal (in the original adjectival sense of the word idea that's used in philosophy, e.g. as defined by Johnson). But there is a reason why I haven't lingered much on this: if such a theory is to be acceptable, it must be consistently philosophically and mathematically reconcilable with physical theory, and there must be physical reasons to motivate its acceptance over other possible interpretations. This, therefore, is how I've argued for a reconception of time in my essay.

    As for the essay you linked for me: I liked it; I found it interesting and easy to read; and I agreed with most of what you wrote. If you're interested in knowing how much, you could read sections 2.1 -- 3.2 in my dissertation, which I've provided a hyperlink to in the references section of my essay. I think you'd like that.

    If you have any more questions or comments, I'd be glad to hear them. As I said before, I am trying to get to your essay for this contest. When I do, I'll try to post something for you there.

    Sincerely,

    Daryl

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    • Post #19

    Dear Daryl:

    Thanks for the clarification, and I understand the cosmic time and cosmic expansion used in standard cosmology as you mentioned:

    "The standard model assumes maximally symmetric space that expands in cosmic time, which is, moreover, the proper time of all fundamental observers. Those *are" the basic axioms of standard cosmology, so to say that it only assumes maximal symmetry of space, or that maximal symmetry and cosmic time are mutually exclusive, is just wrong."

    However, my point is that the fundamental assumption of "a synchronous time and clock in the entire universe" adopted by Standard Cosmology is directly in violation of the relativity of space and time and non-synchronicity of time at varying relativistic velocities (from near-field to far-field universe) demonstrated by the relativity theory. This assumption only holds approximately true in the near-field universe wherein the radial expansion velocities of the galaxies are small (V much less than C) compared to the speed of light because the relativistic effects are small. However, as my paper shows that in the far-field, wherein the velocities are large (V close to C), the standard cosmology deviates from predictions of the supernova observations resulting in the unexplained and paradoxical dark energy. The error results from the fact that at large velocities (V=C), both the space and time dilate to zero stopping the clock and dissolving any cosmic time. Hence, the fundamental assumption of a standard or proper cosmic time cannot be imposed on the far-field universe and must be corrected to eliminate the current inconsistencies and paradoxes that are artifacts of the basic axioms of the standard cosmology.

    Thanks for being patient as we are investigating the fundamental assumptions that are wrong in this forum.

    Regards

    Avtar

    Dear Daryl,

    Though a receding light source certainly looks redshifted so the redshift of galaxies can indicate that they recede from us -in which case our universe expands, a redshift does not necessarily mean that it actually recedes from us.

    The problem I have with the Big Bang hypothesis is that a Big Bang Universe lives in a time continuum NOT of its own making: here the existence of an absolute kind of clock is posited (be it an imaginary one), a clock showing cosmic time, the time passed since the bang, so in this universe it is the same time everywhere.

    As in a BBU the speed of light is interpreted to be a (finite) velocity (in contrast to referring to a property of spacetime, which is something else entirely), here we see a distant galaxy as it was in a distant past as it took its light so long to reach us.

    In contrast, a universe which creates itself out of nothing, without any outside interference has no such 'cosmic' clock, nor does it, as a whole, evolve IN time.

    A Self-Creating Universe (SCU) contains and produces all time within, so here clocks are observed to show an earlier time as they more distant -which is only possible if they (are observed to) run slower as they are more distant, even if they are at rest with respect to us.

    In other words: here we see galaxies shifted farther to red as they are more distant even if they are at rest with respect to us, so in a SCU we should find a linear distance-redshift relation, so this universe doesn't expand at all, let alone suffer an accelerating expansion.

    Though I find it sad to see how a learned and highly intelligent scientist as Stephen Hawking can waste his life on a hypothesis which, in the final analysis doesn't make any sense at all, I find it appalling to see how everybody and his dog in physics follows the same mantra, not even bothering to at least try to dream up contradicting creation scenario's, just for the fun of it, or, in the absurdities such schemes might lead to, affirm the original big bang hypothesis.

    For why the Big Bang isn't such a good idea, after all, see my essay, topic 1328.

    Regards,

    Anton Biermans

      Dear Anton,

      I guess physicists waste their time with things like big bangs because we're concerned with empirically verified and verifiable physical theories. I've criticised the big bang in the standard model to the extent that I could manage coherently in this short essay. If you're interested to read more of my thoughts on that, you could have a look at my PhD thesis, which is hyperlinked in the references section of my essay.

      Daryl

      Dear Avtar:

      Your response has clarified your position a lot for me, but there are two points I think I can clarify further. First, standard cosmology does not `[deviate] from predictions of the supernova observations resulting in the unexplained and paradoxical dark energy'; rather, the Nobel prize winning observation was that a parameter of the standard model that had been presumed to be zero---viz. Lambda---is actually positive (as it should be, I think, for reasons I've argued in my essay). The flat LambdaCDM model agrees extremely well with the supernova observations---only with different parameters than were expected.

      The second point is really key to truly understanding the expansion scenario, which I think you're still not quite grasping. The cosmological redshifts are not thought to be due to relativistic effects or recessional velocities through space. Rather, cosmological redshifts are thought to result from the expansion of space through which the photons are moving, causing them to continuously lose energy in transit. This has been confirmed by the fact that thousands of distant quasars, galaxies, and supernovae have been observed with redshifts *greater than 1*. In fact, the largest confirmed redshift is greater than 8. But rather than taking this to imply that these objects are actually moving away from us faster than the speed of light, we interpret cosmological redshifts within the context of the standard model, as resulting from the expansion of maximally symmetric space where comoving observers actually remain always at rest---i.e., at constant spatial coordinates in the metric

      [math]ds^2=-dt^2+a(t)^2d\Sigma^2,[/math]

      where [math]d\Sigma[/math] describes three-dimensional maximally symmetric space and a(t) is the scale-factor that multiplies it throughout the course of cosmic time.

      I hope this is helpful to you.

      Sincerely,

      Daryl

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      • Post #23

      Avtar

      Time does not occur in physical reality, there is only timing, a measuring system which calibrates rates of change between such realities. At any given point in time (as in timing) there is a definitive physical reality, at another there is a different one. There is occurrence and re-occurrence differently, it is a sequence. This must be so, otherwise there is no physical reality. So, de facto, the physically existent event known as Big Bang, occurred at one spatial point at one point in time, assuming it did occur.

      Now, what this really demonstrates is that we are trapped in a sensory loop. We can only know of reality via sensory detection (hypothecation while overcoming practical problems in that process is still bounded by it). Put another way around, we cannot transcend our own existence. So 'Big Bang' represents the logical end point of reality as it is knowable to us. One can hypothesise that there was a sequence of these, but that is, logically, all the same. There is still the same end point.

      Paul

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      • Post #24

      Daryl,

      Thank you for for your kind words about my essay addressing the time paradigm issue. I've now given a quick read (it deserves a much more thorough read) to the sections of your dissertation to which you referred me. It is very impressive, and, as you suggested, I found much in it to like. I almost began to think at some points that we could be alter egos. I will go back and read it again more carefully, but wanted to get some sort of response to you here before the trail grows cold.

      I did not intend to imply in my earlier post that *you* were arguing in favor of the possibility of time travel, but rather, as you pointed out in your dissertation (p.114) some very reputable relativists *have* seriously investigated the problem of time travel and speculated on its theoretical possibility.

      "However, I hope you'd also see that I disagree with the notion that the changes we observe *are* the flow of time, since then the Universe (the present, the particular time, as you've called it) might not equably endure, which I think has to be a prior aspect of our existence."

      This could be a fundamental point of potential disagreement. My view, as I've stated in yet another related essay 'On the Impossibility of Time Travel', is that "the configuration of the universe, i.e., the arrangement of all its many bits and pieces relative to one another, is constantly changing. As sentient beings, we are able to *observe* some of these changes; we are aware of our surroundings. . . .Using our relatively recent and still imperfectly honed invention called language, we humans have come to refer to the changing configurations of the universe as 'the flow of time.' It is absolutely crucial to recognize . . . however, that the changes . . . are *not caused by,* and are not in any way a consequence of, the flow of time. Rather, the changes we observe (as well as those we don't observe) *are* the flow of time. If the configuration of the universe did not change, there would be no flow of time."

      You wrote in your dissertation (p. 128) ". . . We've also recognized that if physical reality would be only a continually rearranging three-eimensional thing . . . then our inquiry would need to end there, because it would then be impossible to determine an actual cause for that pre-defined abstract prime mover, through any theory of physical reality . . . . [footnote: i.e., because no physical cause can be attributed to the existence or workings of such a supernatural entity, even if it is capable of exercising a physical influence on the Nature of things."]

      The reasoning behind that statement has not come together for me yet, but I'll go back and spend more time trying to understand the thinking behind it.

      In the interest of not hijacking this blog for a discussion of the nature of time (your topic is, after all, cosmology, not time!), I'd propose that if we wish to talk further about time we move our discussion over to the blog for my essay, which *is* about the nature of time. If we do so, I'd also request that (when you can find time) you read my essay 'On the Impossibility of Time Travel'. Meanwhile, I'll be re-reading your essay here and your dissertation. Thanks.

      jcns

      Hi J. C. N. Smith,

      Thanks for having a look at my dissertation. Regarding this difference of opinion we have, I think I can clarify that my reason for thinking that there has to be a prior equable duration in physical reality, by which cosmic time passes at a rate of one second per second regardless of any change in its arrangement, is that space-time is co-ordinated---i.e., there is a regular, consistent way that things occur in our physical Universe. I think this is really the point where Augustine can be seen as having made a substantial contribution to the philosophy of time, although I think Aristotle already grasped the necessity of it, and thus took pains to define his prime mover. And I suspect Newton also understood this better than the relationalists of his time, when he defined absolute time. Furthermore, as I've argued, I think Newton's error was not in his definition of absolute time, but in the way it was incorporated into the physical description, requiring space to be synchronous in the frames of every inertial observer, which is incompatible with a finite speed of light.

      I urge you to really try to understand the physical description I've given in section 3 of my essay, which illustrates how SRT can be reconciled with this view of the nature of time. This relates to another point I neglected to mention to you yesterday: in your essay, I think you really haven't properly dealt with the paradox of the relativity of simultaneity in SRT, sometimes called the Andromeda paradox after a useful illustration by Penrose, which is commonly taken to imply that there must be a block universe. This paradox *is* a real problem for any presentist view of time, and can't be dismissed as you've done in your essay. Rather, the paradox can be resolved, and the theory reconciled with true becoming, according to the description I've given in section 3 of my essay.

      Finally, regarding your last statement above, my essay really is largely about reconceiving our view of the nature of relativistic time, so this discussion is appropriate here. However, as I've stressed above, it isn't enough simply to describe this view, and it isn't even enough to explain how it can be reconciled with physical theory and intuition: scientific motivation that supports this reconception of time *over* the old view that comes from the operational definition of the relativity of simultaneity, is really needed as well. This point was made, e.g., by Craig Callender in `Shedding Light on Time'. In my essay, I have therefore done my best to offer scientific motivation from cosmology for accepting a shift to this alternate view of the nature of time.

      Best,

      Daryl

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      • Post #26

      Hi Daryl,

      Thanks for your excellent reply to my comments. You've given me much to think about and much to read (and re-read). Unfortunately, I'm not a speed reader, especially not of PhD dissertations. Will be busy reading and thinking for a while before getting back to you. Please keep a light on for me. Okay? Thanks again!

      Best,

      jcns

      Dear Daryl:

      Thanks for the clarification, and we seem to be converging on the real issue with the standard model assumptions and use of different than expected empirical parameters to fit the data without any real physical and mechanistic physics proposed for the Cosmological Constant - viz. Lamda. The reason for positive Lamda presumably justifies the presumed Dark Energy but no physics of dark energy as to where it comes from and what it constitutes is lacking.

      What I am trying to clarify is that the root cause behind the need in the standard model to adjust for the positive value of Lamda as opposed to the expected zero Lamda, is the presumption of the Cosmic time and use of the linear Hubble model in the far field, which form the basis for the Big Bang and accelerated expansion. The point is that two assumptions (Absolute Cosmic Time and Linear Hubble Expansion in the far field) in the basic axioms of the standard cosmology are fundamentally in violation of relativity theory and hence, need the corrections to the expected Lamda values. The Relativistic Universe Expansion (RUE) model that provides a mechanistic physical model based on relativity theory is shown to naturally predict the observed (so-called accelerated expansion via Supernova) without any extraneous or after-the-fact corrections as needed by the standard model. RUE model does not support a universal Cosmic time but provides a predictive physics-based mechanistic model for the no-zero Lamda.

      On the second point, RUE predicts the observed redshifts using relativity theory without exceeding C and without resorting to the need for the unnecessary standard model interpretations i.e. - "...the expansion of maximally symmetric space where comoving observers actually remain always at rest---i.e., at constant spatial coordinates in the metric, through which the photons are moving, causing them to continuously lose energy in transit."

      In summary, I agree with your assertion that - " .. a parameter of the standard model that had been presumed to be zero---viz. Lambda---is actually positive". My point is that this extraneous correction to the standard model is needed because of its deficient assumptions of non-relativistic "Cosmic Time" and Linear Hubbble Model in the far-field. My paper shows that other unresolved cosmic paradoxes such as dark energy, dark matter, big bang singularities, multiverses, multi-dimensions may also be mere artifacts of the incorrect assumptions of Cosmic Time and Linear Hubble Expansion (LHE) in the far-field (Please note that LHE works well in the near field expansion). Eliminating the explicit universal time from cosmology theories resolves many of the current paradoxes of the prevailing Cosmic Conundrum.

      Sincerely,

      Avtar

      Dear Paul:

      I agree - Time does not occur in physical reality, there is only timing, a measuring system which calibrates rates of change between such realities.

      But I do not agree with your statement - "So, de facto, the physically existent event known as Big Bang, occurred at one spatial point at one point in time, assuming it did occur." The Big Bang is always associated with an absolute "MOMENTof the BEGINNING" of time i.e. Time =0 at the moment of Big Bang, which is non-existent since time, as well as space, is only a relative and not an absolute entity. Time's perception varies according to the observer's speed or frame of reference. There is no absolute fixed time or location in the universe to call it a Proper or Cosmic time and place of origin - Big Bang. Hence, the Big bang as strictly defined can never happen and is merely an artifact of the Newtonian mindset.

      Sincerely,

      Avtar

      Dear Daryl and jcns,

      A very interesting interchange. JCN says, "humans have come to refer to the changing configurations of the universe as 'the flow of time.' It is ... crucial to recognize ... however, that the changes ... are *not caused by,* and are not in any way a consequence of, the flow of time. Rather, the changes ...*are* the flow of time."

      That has sort of been the way I have been thinking, but your very phraseology has caused me to see it in a different perspective. As you know energy and time are conjugate variables, and in the view you [jcns] just espoused, it would be *energy* (or more correctly, "the flow of energy") that is real and time that is emergent. But in the "present as real" perspective, obviously energy is everywhere local, whereas time is global and universal. Therefore there would seem to be a universal 'reality' to time as opposed to merely a handy way of tagging sequential events.

      Daryl, I too am working through your wonderfully written dissertation. Wow!

      Edwin Eugene Klingman

      Dear Edwin Eugene Klingman and J. C. N. Smith,

      This has indeed been a very interesting exchange, and I look forward to more. I wanted to say thanks to both of you for reading my dissertation, and for your positive responses. I really appreciate them.

      Edwin, as promised, I will read your essay. It's currently right near the top of my list of things to do, and from the little I've gotten to so far, I do look forward to reading it in full.

      J. C. N., I will read through your essay for this contest as well, and leave a comment there.

      Thanks again,

      Daryl