Lee Smolin and the status of modern physics

3262010115214PMby Joe Boswell

[This is the first interview we are publishing here at Scientia Salon, hopefully the beginning of a new interesting trend at the magazine.]

I write a science and philosophy blog called Adams’ Opticks [1], and about a year and a half ago I published an in-depth critique of Lee Smolin’s Time Reborn, a radical reappraisal of the role of “the present moment” in physics [2,3]. My article was certainly critical of the book, but also something of a labor of love, and I’m completely thrilled to say that Lee has now read the piece and would like to respond. What follows is a Q&A, with most of the questions derived from the earlier post [4].

Adam’s Opticks: Hi Lee, central to your thesis as outlined in Time Reborn, and in its recent follow-up The Singular Universe (co-authored with Roberto Mangabeira Unger) [5], is a rejection of the “block universe” interpretation of physics in which timeless laws of nature dictate the history of the universe from beginning to end. Instead, you argue, all that exists is “the present moment” (which is one of a flow of moments). As such, the regularities we observe in nature must emerge from the present state of the universe as opposed to following a mysterious set of laws that exist “out there.” If this is true, you also foresee the possibility that regularities in nature may be open to forms of change and evolution.

My first question is this: Does it make sense to claim that “the present moment is all that exists” if one has to qualify that statement by saying that there is also a “flow of moments?” Does the idea of a flow of time not return us to the block universe? Or at the very least to the idea that the present moment represents the frontier of an ever “growing” or “evolving” block as the cosmologist George Ellis might say?

Lee Smolin: Part of our view is that an aspect of moments, or events, is that they are generative of other moments. A moment is not a static thing, it is an aspect of a process (or visa versa) which generates new moments. The activity of time is a process by which present events bring forth or give rise to the next events.

I studied this idea together with Marina Cortes. We developed a mathematical model of causation from a thick present which we called energetic causal sets [6]. Our thought is that each moment or event may be a parent of future events. A present moment is one that has not yet exhausted or spent its capability to parent new events. There is a thick present of such events. Past events were those that exhausted their potential and so are no longer involved in the process of producing new events, they play no further role and therefore there is no reason to regard them as still existing. (So no to Ellis’s growing block universe.)

AO: Can you help me understand what you mean by a “thick present”? I’m confused because if the present moment is “thick” rather than instantaneous, and may contain events, it seems like you’re defining the present moment as a stretch of time, which looks like a contradiction in terms. Similarly, when you say that the activity of time is a process I’m left thinking that events, activities and processes are all already temporal notions, and so to account for time in those terms seems circular.

LS: I can appreciate your confusion but look, think about it this way: the world is complex. What ever it is, it contains many elements in a complicated network of relations. To say what exists is events in the present does not mean it is one thing. The present is not one simple thing, it is the whole world, therefore it contains a vast complexity and plurality. Of what? Of processes, which are dual to events.

AO: One of your main objections to the idea of eternal laws comes in the form of what you diagnose as the “Cosmological Fallacy” in physics. Your argument runs that the regularities we identify in small subsystems of the universe — laboratories mainly! — ought never to be scaled up to apply to the universe as a whole. You point out that in general we gain confidence in scientific hypotheses by running experiments again and again, and define our laws in terms of what stays the same over the course of many repetitions. But this is obviously impossible at a cosmological scale because the universe only happens once.

But what’s wrong with the idea of cautiously extrapolating from the laws we derive in the lab, and treating them as working hypotheses at the cosmological scale? If they fit the facts and find logical coherence with other parts of physics then great… if not, then they’re falsified and we can move on. As an avowed Popperian yourself, are you not committed to the idea that this is how science works?

In addition, wouldn’t the very idea of “laws that evolve and change” make science impossible? How could we ever confirm or falsify a hypothesis if, at the back of our minds, we always had to contend with the possibility that nature might be changing up on us? Don’t we achieve as much by postulating fixed laws and revising them on the basis of evidence as we might by speculating about evolving laws that would be impossible to confirm or falsify?

LS: To be clear: the Cosmological Fallacy is to scale up the methodology or paradigm of explanation, not the regularities.

Nevertheless, there are several problems with extrapolating the laws that govern small subsystems to the universe as a whole. They are discussed in great detail in the books, but in brief:

  1. Those laws require initial conditions. Normally we vary the initial conditions to test hypotheses as to the laws. But in cosmology we must test simultaneously hypotheses as to the laws and hypotheses as to the initial conditions. This weakens the adequacy of both tests, and hence weakens the falsifiability of the theory.
  2. There is no possible explanation for the choice of laws, nor for the initial conditions, within the standard framework (which we call the Newtonian paradigm).

Regarding your questions about falsifiability, one way to address them is to study specific hypotheses outlined in the books. Cosmological Natural Selection, for instance, is a hypothesis about how the laws may have changed which implies falsifiable predictions. Take the time to work out how that example works and you will have the answer to your question.

Another way to reconcile evolving laws with falsifiability is by paying attention to large hierarchies of time scales. The evolution of laws can be slow in present conditions, or only occur during extreme conditions which are infrequent. On much shorter time scales and far from extreme conditions, the laws can be assumed to be unchanging.

AO: I’m actually a big fan of Cosmological Natural Selection (which suggests that black holes may give birth to new regions of spacetime, fixing their laws and cosmological constants at the point of inception [7]) — and I can see how that is both falsifiable in itself, and would still allow for falsifiable science on shorter time scales.

Far more radical, however, is your alternative theory which you dub the Principle of Precedence. The suggestion here is that we replace the metaphysical extravagance of universal laws of nature with the more modest notion that “nature repeats itself.” The promise of this idea is that it makes sense of the success of current science whilst leaving open the possibility that truly novel experiments or situations — for which the universe has no precedent — will yield truly novel results.

To my mind, however, this notion begs many more questions than it answers. You claim, for instance, that the Principle of Precedence does away with all needless metaphysics and is itself checkable by experiment. But is it? You suggest setting up quantum experiments of such complexity that they’ve never been done before in the history of the universe and seeing if something truly novel pops out. But how could we ever tell the difference between a spontaneously generated occurrence and one that was always latent in nature and simply unexpected on the basis of our limited knowledge? And once again, as a falsificationist, shouldn’t you count the thwarting of expectations as evidence against individual theories, rather than positive proof of a deeper principle?

LS: My paper on the principle of precedence is a first proposal of a new idea. Of course it raises many questions. Of course there is much work to do. New ideas are always fragile at first.

As to how to tell the difference between a spontaneously generated occurrence and one that was always latent in nature — this is a question for the detailed experimental design. Roughly speaking, the statistics of the fluctuations of the outcomes would be different in the two cases. I fail to see how such an experiment would violate falsificationist principles.

In addition, we believe we know the laws as they apply to complex systems: they are the same laws that apply to elementary particles. To posit new laws which apply only to complex systems, and are not derivative from elementary laws, would be as radical a step as the one I propose.

AO: Can you tell me how the universe is supposed to distinguish between precedented and unprecedented situations? On the face of it, it seems like unprecedented things are happening all the time. You and I have never had this conversation before. Are we establishing a new law of nature right now, and if not, why not?

Another objection: can you tell me where novelty is supposed to come from? If the “present moment” is both the source of all regularity in the universe, and the blank slate upon which formative experiences are recorded — then what could introduce any change? Are you assuming that human consciousness and free will may be sources of genuine novelty?

LS: How nature generates unprecedented events and how precedent may build up are important questions that need to be addressed to develop the idea of precedence in nature. What I published so far is just the beginning of a new idea.

It’s intriguing to speculate about the implications for intentional and free actions on the part of living things. But in my view this is very premature. I am not assuming that consciousness is a source of novelty; I am only making a hypothesis about quantum physics. There is a very long way to go before the implications could be developed for living things.

AO: Nevertheless, it seems readily apparent from your collaborations with the social theorist Roberto Mangabeira Unger, and also the computer scientist Jaron Lanier, that you see many connections between your conception of physics and the prospects of human freedom and human flourishing. It concerns me, however, that in pursuit of a singular — very beautiful — solution to so many problems in science, philosophy, politics and our personal lives, a lot of awkward details may get overlooked.

In philosophy, for instance, you claim to show that the reality of the present moment — conceived in terms of unresolved quantum possibilities — may at last solve the problem of free will. But what of the history of compatibilism in philosophy — from David Hume to Daniel Dennett — that purports to show that our freedom as biological and psychological agents is not only compatible with the regularity of nature, but may in fact depend upon it?

LS: There are certainly common themes and influences in my work and those of Jaron Lanier and Roberto Mangabeira Unger. And I’m happy at times to indulge in some speculation about these influences. But these are very much to be distinguished from the science. The point is that I am happy to do the scientific work I can do now and trust for future generations to develop any implications for how we see ourselves in the universe. There is much serious, hard work to be done, and it will take a long time. Especially given the present confusions of actual science with the science fiction fantasies of many worlds and AI (these two ideas are expressions of the same intellectual pathology).

I agree that we have to build a counter view carefully. I don’t claim to show that my work solves the problem of free will. I suggest there may be possibilities worthy of careful development as we learn more. As for compatibilism, I am unconvinced, but I haven’t yet done the hard work needed to develop the alternative. Dan Dennett is a generous, serious and warmhearted thinker who works hard to produce arguments which are crystal clear. But talking with him or reading him, both of which are great pleasures, I sometimes find that at the climax of one of his beautifully constructed arguments, the clarity fades and there is a step which I can’t follow. I hope someday to have the time to do the hard work to convince myself whether the fault is with his reasoning or my understanding.

AO: Since I have you here, let me try to make the compatibilist objection compelling with three more questions, inspired to a great extent by Dennett’s Freedom Evolves [8]:

  1. If we turn to physics (as opposed to biology or psychology) in search of free will, are we not likely to end up granting as much free will to rocks or tables or washing machines — or indeed computers — as we do to human beings? If we are to be able to change and adapt in response to the problems we face, surely the science of free will must be the science of a human plasticity that outstrips the plasticity of nature more generally?
  2. You claim that the openness of physics may enable us to transcend the fatalism inherent in predictions from climate science, for example: in 2080 the average temperature on earth will be six degrees warmer than it is now. But what of those other predictions stemming from climate science such as: a concerted effort to reduce carbon emissions will avert disaster? If the true nature of physics undermines the certainty of the first prediction, does it not also undermine the certainty of the second?
  3. Setting yourself against a long history of thinkers who would write off the sensation of “now” as a psychological quirk incompatible with timeless physics, you go so far as to call it “the deepest clue we have as to the nature of reality.” But I wonder what you make of the innumerable psychological and neuroscientific studies that demonstrate the problematic nature of human perception of time over short intervals? Benjamin Libet’s apparent prediction of conscious decisions from unconscious brain activity seems particularly troubling. Might you be persuaded to push in the direction urged by Dennett and resist such a conclusion by arguing that an instantaneous “you” cannot be contrasted with your slow-moving brain activity, and that the search for free will and consciousness in “the present moment” is fundamentally misguided? Can we not look, instead, to the mechanically-possible processes of decision making, learning and adaption that take place over seconds, minutes, weeks and years?

LS: I don’t see why grounding human capabilities in an understanding of what we are as natural beings implies that every capability we have is shared with rocks. We have a physical understanding of metabolism, or the immune system, but rocks and tables have neither. My guess is that when we know enough to seriously address these issues, the vocabulary of concepts and principles at our disposal will be greatly enhanced compared to what we have now. Certainly we are aspects of nature and every capability we have is an aspect of the natural world.

Regarding climate change, the first is a prediction of what could happen if we don’t take action to strongly reduce GHG emissions. My point is not that the climate models are completely accurate. My point instead is that the intrinsic uncertainties in their projections are the strongest reason to act to reduce emissions so we can avert disaster however the uncertainties develop. In national defense we prepare for war because the future is uncertain. Climate change is not an environmental issue, its a national security issue and should be treated as such.

As for the objections from neuroscience, I completely fail to see the force in this kind of argument. Those studies are fascinating but I don’t think they remotely show what is claimed. Certainly the present moment is thick and the self is not instantaneous. But giving up the instantaneous moment for the thick and active or generative present (as I sketched above) does not imply that consciousness or time or becoming are illusions.

AO: Lee Smolin — thank you!

_____

Joe Boswell is a writer and a musician trying to figure out how to make a living in a world where words and music are free. He has a degree in English literature, but having learned to bluff philosophy by listening to lots of podcasts, he enjoys picking fights with eminent scientists and philosophers on his blog, Adams Opticks (https://adamsopticks.wordpress.com). His songs are available on Bandcamp (https://joeboswell.bandcamp.com). He does Twitter too (https://twitter.com/joeboswellmusic).

Lee Smolin is is an American theoretical physicist, a faculty member at the Perimeter Institute for Theoretical Physics, an adjunct professor of Physics at the University of Waterloo and a member of the graduate faculty of the Philosophy department at the University of Toronto.

[1] Adam’s Opticks.

[2] Time Reborn: From the Crisis in Physics to the Future of the Universe, by L. Smolin, Houghton Mifflin Harcourt, 2013.

[3] For a good introduction to the basic ideas of Time Reborn, see this video.

[4] On Time Reborn as modern myth: Why Lee Smolin may be right about physics (but probably wrong about free will, consciousness, computers and the limits of knowledge), by Joe Boswell, 5 October 2013

[5] The Singular Universe and the Reality of Time: A Proposal in Natural Philosophy, by R.M. Unger and L. Smolin, Cambridge University Press, 2014.

[6] The Universe as a Process of Unique Events, by M. Cortês and L. Smolin, arXiv.org, 24 July 2013.

[7] For a more critical take on the idea of cosmological natural selection see: Is Cosmological Natural Selection an example of extended Darwinism?, by M. Pigliucci, Rationally Speaking, 7 September 2012.

[8] Freedom Evolves, by D.C. Dennett, Viking Adult, 2003.

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74 replies

  1. Hi Marko,

    Don’t worry, I love nitpicking! (especially on the nature of science). 🙂

    … we should really say “Any cause that has reproducible effects in the observable universe…”. There are things that cannot be reproducibly studied, and we (physicists, scientists…) must always be acutely aware of the difference between observation and experiment.

    As someone firmly in an “observational” science I must beg to differ. Reproducible experiments are indeed a very good thing, if we can do them, but we cannot insist in them. Science is very pragmatic and is a matter of doing our best. Often we can’t do reproducible experiments in our lab.

    To pick a few examples, how about the Tunguska event, or the Chicxulub event and the K–T extinction. Or, say, the hypothesis that a Mars-sized planet collided with Earth early on, with the resulting debris forming our moon. In all such cases we can’t reproduce these events in order to study them, yet I would argue that their study is entirely scientific. Indeed this surely applies through large swathes of science.

    We simply do our best — which means that if we can do reproducible experiments then we should. Feynman summed up the scientific method as “The first principle is that you must not fool yourself–and you are the easiest person to fool”, which doesn’t require reproducible experiments if they are not feasible.

    Could, in principle, science study the possibility of a “God” intervening causally? Yes, provided only that this posited cause makes some different somewhere. If so, you simply analyse its effect and deduce what you can about its nature. Even if the effects had no apparent pattern we could still cope with that, in the same way that we cope with the apparent randomness of radioactive decay. One can object that God’s whims might be too capricious to fathom, and they might be, but again you do your best.

    Afterall, chimpanzees can be pretty complicated and capricious, but nobody says that studying chimps and chimpanzee politics is unscientific. In the same way, studying gods — if they existed — would be entirely scientific. The fact that science has gradually ditched notions of gods as our science and understanding have advanced is not a prior metaphysical assumption, it’s a scientific conclusion resulting from having done our best to understand the world.

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  2. Marko,

    “This nitpicking is just a note for non-scientists — in case they are not aware of the level of rigour necessary for something to be called “science”.”

    As a non scientist, may I pick several nits with astrophysics and cosmology? I think this area has seriously stepped over the edge.
    I assume the principle of falsifiability means a theory should make predictions and observation determines if these predictions are accurate. Yet on at least two occasions, with the smoothness of the background radiation and the change in the rate of redshift, cosmology has been allowed to insert two rather enormous forces of nature, “inflation” and “dark energy,” in order to bridge the difference between prediction and observation. Implicit prediction for the smoothness issue and explicit for the rate of redshift.
    As well as the point I’ve brought up here several times, that in order to explain why the geometry of this redshift makes us appear at the center of the expansion, it was changed from an expansion in space, to an expansion of space, using the premise of spacetime. Yet this completely overlooks the fact that in order to be relativistic, the speed of light would have to increase as well, in order to remain constant.
    When I try raising these issues, mostly I get ignored, or in the case of bringing it up on physorg, lots of down votes, with very few responses. This is the sort of behavior I would expect from a cult, not legitimate science. One of the few responses I do get is the argument the intergalactic light is just being “carried along” by the expansion. Which is nonsense, given it is the redshifting of this light that is presumed proof of the expansion. If it was carried along, then why would it be redshifted, given redshift is an effect of the light having to travel further. So there is expanding space, based on the redshift and we measure this in constant units based on the speed of the very same light.
    So where is the rigor, if they can keep adding patches? How can it be falsified??? What if an accountant simply made up a figure, every time there is a discrepancy? Appeals to authority don’t cut it.
    As an aside, an optical effect would logically explain why we appear as the center and if it compounds on itself, why the rate curves upward.

    Thomas,

    “Notions of the present are in some ways more difficult for me to grasp and express than are those of the past and future. The present seems a subliminal point needed to bridge past and future.”

    A somewhat similar relationship is Complexity theory, with the complex as the intersection of chaos and order. Naturally the past is ordered and chaos the future. I would amend it to the relationship between energy and form, as energy moves to the future, i.e. potential, while form tends toward entropy and thus falling into the past, since it is a closed set when separate from energy.

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  3. Hi Marko,

    Thanks for the clear exposition.

    While the model you describe cannot be represented as a 4 dimensional manifold, there can still be a ‘block universe’ formulation of it. For example I could have the set of all events that ever occur and also an ordered set of transitions – like ‘such-and-such event causes such-and-such other event’ or ‘such-and-such event ceases to have any causal role’.

    Thus any point along the ordered set will have an implied set of events which – at that point – have a causal role and therefore a ‘present moment’ according to that definition.

    Or maybe there are some transitions where there is no fact of the matter about which occurred before the other in which case the transitions structure might have to be something like a directed graph. But the point is that any mathematical model of a system evolving through time can have an equivalent representation as a static structure, even if indeterminism is part of that model.

    So we can look at one of these and say “look, time is real and it flows” and then look at the other equivalent structure and say “the distinction between past, present and future is a persistent illusion”.

    Lee Smolin seems to understand this, he warns of the tendency to confuse the model with the reality – which is something scientists do all the time.

    But if he is presenting this model as somehow rescuing the reality of time then he is just making the same mistake.

    If Smolin’s ideas develop into something which is a viable model of quantum gravity, then that is great, but that is a different issue to what is being presented in this interview.

    We often hear that it has become an orthodoxy among physicists that the flow of time is an illusion. But what could such a claim even mean? It would imply that

    there is a logically possible state of affairs that represents a real flow of time and;
    this is not the case in our universe

    But if we were in a Universe in which there really was a flow of time, how would we detect it? As I pointed out before any model for a ‘real’ flow of time could have an equivalent static formulation.

    That seems to indicate that we can have no rigorous definition of what we mean by a ‘real’ time flow.
    Someone might say “We can make the distinction because a real time flow would have an evolving model and so if we have a static model with no evolving equivalent then the flow of time is an illusion”. But without a rigorous definition of what a ‘real’ time flow is then it is only an intuition that a ‘real’ time flow would involve an evolving model.

    That lack of a definition seems to make the distinction between ‘real’ time and ‘illusionary’ time a pseudo distinction, as I said.

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  4. Brodix, I hope my earlier reference to your comments has not been misinterpreted by you since I look forward to your comments, and, like the comments of many others here, I try to understand them as best I can. Any misunderstanding here is completely attributable to my ignorance of science, not to anything you’ve said. And thanks for personally taking the time to address one of my remarks.

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  5. Coel,

    Reproducible experiments are indeed a very good thing, if we can do them, but we cannot insist in them. Science is very pragmatic and is a matter of doing our best. Often we can’t do reproducible experiments in our lab.

    I am not disagreeing with you, on the contrary! 🙂 I just wanted to emphasize that there is a qualitative difference between observation and experiment when doing science. Otherwise someone may claim that things like telepathy or walking on water should be explained (or otherwise accounted for) by science. Namely, there are anecdotal reports of people managing to perform such feats 🙂 — but anecdotal observation (whether you believe it to be true or not) does not count as scientific evidence unless it is reproducible (under controlled conditions, etc.).

    Brodix,

    As a non scientist, may I pick several nits with astrophysics and cosmology? I think this area has seriously stepped over the edge.

    No you may not, and please don’t. 🙂 If you are not a scientist, you have two choices — either trust that scientists know what they are talking about, or go learn the relevant math and physics, in order to figure out for yourself whether they are right or wrong. But unless you know the relevant details well enough, nobody will give you any credibility in any criticism of any established scientific result.

    When I try raising these issues, mostly I get ignored, or in the case of bringing it up on physorg, lots of down votes, with very few responses.

    Precisely. If you are contesting something that all other experts agree on, you better be an expert yourself, or otherwise people will not listen.

    Robin,

    While the model you describe cannot be represented as a 4 dimensional manifold, there can still be a ‘block universe’ formulation of it.

    Only if you stretch the definition of the term “block universe” way beyond its usual meaning. Usually, block universe contains both the past events, the present events and the future events. Then, at each “moment of time” the present is then represented as one or the other “slice” of the block.

    But in our case the block can contain only the past and the present, because the future doesn’t exist (as soon as it comes to existence, it becomes part of the present, so…). Geometrically, you could imagine this as a “discretized manifold” with an open timelike boundary, which grows. The growth is represented by new points being created and added to the thick boundary layer, while other points pass on from the boundary into the bulk. This dynamical process describes the passage of time.

    In all this it is important to understand the difference between the “evolution of space” (as time passes) and the “evolution of spacetime” (as time passes — !!). The former can always be represented as a “block spacetime”, while the latter cannot be.

    We often hear that it has become an orthodoxy among physicists that the flow of time is an illusion. But what could such a claim even mean?

    My sentiment as well. 🙂 That “orthodoxy” was believed by physicists before they learned that Nature is not deterministic, and that the real world cannot really be represented as a block-universe. Today that statement is very much obsolete, at least in the QM and QG communities. There may be contemporary physicists who still know only Newtonian mechanics and some relativity, and they may still believe in such “orthodoxy”, but modern physics has moved on.

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  6. Hi Marko,

    Only if you stretch the definition of the term “block universe” way beyond its usual meaning. Usually, block universe contains both the past events, the present events and the future events. Then, at each “moment of time” the present is then represented as one or the other “slice” of the block.
    But in our case the block can contain only the past and the present, because the future doesn’t exist (as soon as it comes to existence, it becomes part of the present, so…).

    I am not sure you understood my formulation. It does have all events, past, present and future in a static set (and in no particular order). The evolution of the system is described in the transitions set, also a static structure. So I am not sure that I am really stretching the concept of ‘block universe’, I am just slicing it a little differently.

    I can illustrate this with your earlier population dynamics analogy. I have a list of everyone who ever lived or will live in no particular order {Adam,Abel,Awan,Cain,Eve …} (yes, yes I know they weren’t real people 🙂 )

    Then I have a second list of transitions containing references to the events and their transitions: (Adam & Eve cause Cain), (Adam & Eve cause Abel), (Abel ceases to be a causal agent), (Adam & Eve cause Awan), (Cain & Awan cause …) well you get the idea.

    The transitions list is also a static structure.

    Traverse the list and you have an implied set of currently causal events (ie the ‘present’) at any point in the list. {Adam,Eve},{Adam,Eve,Cain},{Adam,Eve,Cain,Abel},{Adam,Eve,Cain},{Adam,Eve,Cain,Awan}…

    Since they are implicit in the transitions list the set of the ‘present’ does not have to be specified explicitly and thus no event needs to appear more than once in the structure.

    Now maybe Adam and Eve conceived Awan on a near light speed trip round the universe while Cain slew Abel back on Earth, then there is no easy answer as to which happened first, then I need some sort of directed graph for my transitions instead of a simple list

    But if Smolin’s model has any analogous indeterminacy of precedence then the idea of a ‘present’ disappears from it in any case except as an approximate concept.

    But that is not really important, the main point is that I can create a static formulation which is mathematically equivalent to the evolving system, I think I could probably do that for any evolving system.

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  7. Everyone,

    After thinking a bit and rereading the comments, maybe I can provide some additional clarifications about some things. By the way, it seems that I am providing unsolicited interpretation and argumentation about both the essay and Lee’s research, but I hope the authors don’t mind. 🙂

    In energetic causal set theory (and in the particular model presented in 1307.6167), there are three fundamental concepts that should be distinguished. The first is the causal structure between discrete-spacetime-events. The second is the number of “steps” between a couple of events along some particular trajectory in the causal structure. The third is the action of the “event generator”, which adds new events to the structure.

    In classical physical theories (like Newtonian mechanics, relativity, QM) all three of these concepts are mostly the same thing, which we call “time”. But in the model under discussion, these three concepts — while related — are not equivalent to each other. I feel that a major source of confusion comes from the failure to distinguish between these.

    The causal structure tells us about the relative orientations of the local light-cone structures. It gives us a qualitative description of which events are in the “past”, “present” and “future”, from a perspective of a particular given event. This is like in special relativity.

    The number of “steps” connecting the two events along the given chain of events in the causal structure tells us the “coordinate time”. This is the thing that is being measured by a clock. Different clocks follow different trajectories and may give different time intervals between the same two events. This is like in general relativity.

    The action of the “event generator” is the addition of the new events to the causal structure. The generator takes a certain subset of all events constructed so far (the “present”) and adds to it another event (“future to present”). Then it discards some of the events from the “present” set (making those events part of the “past”) and repeats. Its action is nondeterministic (performed by an uncomputable function), and is nonunitary and irreversible. This is like the collapse of the wavefunction in quantum mechanics.

    So all three concepts should be familiar from the respective theories, and they are all called “time” (defining the past, present, future, etc.) despite not being “the same thing”. As long as we are discussing only one of the three theories (SR, GR, QM), we are mostly free to ignore the other two notions of time. But when we want to make a theory of quantum gravity, we must mesh the theories together, and thus incorporate all three concepts into the single theory. Only then we are faced with a challenge that these three things are all called “time” but are still quite distinct from each other.

    The fact that they are different means that we can talk about “spacetime evolving in time”, “thick present”, “future becoming the present as spacetime evolves”, and such stuff. This always implies a slight abuse of the common language and is highly context-dependent, but the equations are clear and there are no category errors.

    So in order to avoid confusion, please try to distinguish the three types of “time” being used here.

    By the way, note that there is also a fourth notion of time, the thermodynamic “arrow of time” (the often discussed second law of thermodynamics). In quantum gravity this notion of time takes a back seat until the theory is mature enough that we can discuss cosmology, so it is not in the above list.

    I believe this was my fifth post. HTH! 🙂

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  8. Marko to Brodix

    “Precisely. If you are contesting something that all other experts agree on, you better be an expert yourself, or otherwise people will not listen.”

    This site is aimed at Main Street, which you don;t even listen to, unless they are an expert? Seems wrong to me. Is that the why you have not answered the arguments, for pure logic set out on the page, no tricks, about the Uncertainty Principle and Godel’s First & Second Theorems, becuase I have not “expertise”, despite the simple logic? If so, that would we wrong for site like this, wouldn’t it? Is this an exclusively technical site where others are not listened to? I don’t think so.

    As I have said previously, if you are a teacher dealing with all the controversies in physics (or philosophy) today, you look for diverse sources for ideas, which might be one benefit of a site like this. The key is logic, and we all use it and some read about the logic of science and have useful views about it. If they are simply incomprehensible (inconsistent or inapplicable) its always easy to say why.

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  9. Marko,
    So basically falsifiability doesn’t apply to cosmology and every time observation doesn’t match prediction, it is clear evidence of an enormous new force of nature, even to the point of multiverses? Interesting. Very interesting. Thank you for the clarification.

    Thomas,

    I’m just trying to figure things out as well. Admittedly, given there are many areas of interest, from politics to physics, all working together, that human civilization appears to be at one of its most monumental peaks and there is increasing and significant downside, along with having a personal life and work, if I may seem abrupt, it is nothing personal.

    Joe,
    Not joining in the conversation?

    My last post on this thread. It’s been real.

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  10. Since I seem to have reached agreement with Marko 🙂 I’ll divert a comment to brodix,

    When I try raising these issues, mostly I get ignored, or in the case of bringing it up on physorg, lots of down votes, with very few responses. This is the sort of behavior I would expect from a cult, not legitimate science.

    Well, it’s tricky. There are several commenters here who regularly put forward what could be called “personal” versions of physics. For example tienzengong regularly posts lengthy screeds about his personal “physics” that bears no relation to actual physics. It is based on his book that he self-published 30 years ago, which in that time has been cited zero times by actual physicists.

    Should physicists respond to such posts? Well, it is both hard to do within comment limits and largely pointless since it won’t get anywhere (and risks falling foul of the moderation guidelines if one calls a spade a spade).

    But, first on the scientific method:

    … cosmology has been allowed to insert two rather enormous forces of nature, “inflation” and “dark energy,” in order to bridge the difference between prediction and observation. […] So where is the rigor, if they can keep adding patches?

    This is called the scientific method. One continually adapts models to better fit the data. That is exactly what we should be doing. You then have a competition between different models, and pick the one that works best for explanatory and predictive power. So, there is nothing wrong, in principle, with adding things like “dark energy”, the issue is whether it improves the explanatory and predictive power compared to alternative models.

    As for the state of cosmology today, take a look at the second image in this Sean Carroll post about Planck results on the microwave background.

    The red line is a model. Most of the aspects of this model (including adding “dark energy” into the now-standard LambdaCDM cosmology) were developed before the recent WMAP and Planck data and were thus predictions. This means that the exceptionally good fit between cosmological models and data is a now-verified prediction of having added dark energy into the model.

    If you think that such models are wrong, and think you can produce a better model, then go ahead, and compute your own predicted power-spectrum of CMB fluctuations, and preferably predict things that the next-generation of experiments can then test. Physicists do routinely consider alternatives, for example considering whether MOND models give better explanatory and predictive power than “dark matter”.

    … to an expansion of space … Yet this completely overlooks the fact that in order to be relativistic, the speed of light would have to increase as well, in order to remain constant.

    Why? Why do you think that the speed of light would have to increase? Under a special relativistic picture, the speed of light is a property of space (see here). So, if the expansion of space produces more of exactly the same space, then the speed of light remains the same. This is perhaps one reason that “mostly [you] get ignored”: one would first have to spend time sorting out the starting points of the discussion.

    If some non-scientist thinks that they’ve spotted some fundamental flaw that thousands of physicists have all overlooked, then the chances are that the lack of understanding is with them. Physics is not a “cult” (to use your term), and physicists spend their lives criticising each other’s ideas. If an idea gets posted repeatedly and doesn’t even attract a response, the likelihood is that it doesn’t merit one.

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  11. Marko

    So there are no shaky linguistic foundations here — only a shaky linguistic intuition interpreting the math, the latter being quite sound. 🙂

    Touché! Thanks for bringing such a clear and detailed discussion of QM, GQ and Energetic Causal Sets to the table. I feel like I’m learning a lot.

    I still need a little cajoling on ECS; to my eyes, Smolin’s account of it in the interview and the population dynamics metaphor you provide still leave a major question begging, which is this: Don’t ‘events’ and the ‘combination of parent events’ *take time*? So isn’t it circular to explain time in terms of temporal notions like events?

    To the untrained eye, it looks like the unfolding of everyday events in everyday scales of time are being explained by relocating the problem in some micro-arena of space and time.

    Indeed, I’m having a hard time getting more from the ECS definition of the present than “stuff going on right now that can still influence the future”, which seems entirely commonsensical.

    Am I totally off base?

    Robin

    This is interesting:

    So we can look at one of these and say “look, time is real and it flows” and then look at the other equivalent structure and say “the distinction between past, present and future is a persistent illusion”. Lee Smolin seems to understand this, he warns of the tendency to confuse the model with the reality – which is something scientists do all the time. But if he is presenting this model as somehow rescuing the reality of time then he is just making the same mistake.

    Would you say that it’s a little backward, methodologically speaking, to try to ‘represent’ the reality of time in physics? I tend to take the attitude that physics comes first (if it’s empirically validated), and metaphysics second (read off from successful physics). Do you think Smolin is putting the metaphysics first?

    ejwinner

    blockquote>I enjoyed the interview, and the discussion that has followed. However, I admit that I would have preferred more Smolin and less Boswell. It seems you went into the interview not so much to clarify topics but to argue points. I think that has led to some loss of clarity in the comments that have followed.

    As I say in the introduction, the interview has a slightly odd history – it started out as a lengthy article I wrote on my blog. I sent it to Smolin, and he was keen to respond. He’s a busy guy, obviously, so I thought it might make matters easier for him if I broke the article up into bite-size points. I know I’m dragging him over to my turf a little – but if you want to read Smolin discussing his ideas on his own terms, you know where to find him!

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  12. Hi John Smith,

    See my previous comment for why I usually avoid such discussions, but since I’ve started this theme:

    Is that the why you have not answered the arguments, for pure logic set out on the page, no tricks, about the Uncertainty Principle and …

    I (for one) have not replied because I don’t understand what you’re saying or why you think you have a valid objection to the uncertainity principle.

    Your objection seems to be about defining “velocity” at a point. The way to do this is using calculus, as used routinely since Leibniz and Newton developed it in c1660. One can define the “instantaneous velocity” by taking the limit as the time-interval goes to zero of the ratio of space-interval to time-interval. See here. Such methods are used pretty much throughout physics. I thus fail to see any problem.

    As I said above: “If some non-scientist thinks that they’ve spotted some fundamental flaw that thousands of physicists have all overlooked, then the chances are that the lack of understanding is with them” and “If an idea gets posted repeatedly and doesn’t even attract a response, the likelihood is that it doesn’t merit one”.

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  13. Coel,

    This seems to be a good time to express my appreciation of your gentlemanly responses and patience over many months, and right here as well:

    “….it is both hard to do within comment limits and largely pointless since it won’t get anywhere (and risks falling foul of the moderation guidelines if one calls a spade a spade)…..”,

    as well as your ability to at least be somewhat blunt when it is called for:

    “…lengthy screeds about his personal “physics” that bears no relation to actual physics. It is based on his book that he self-published 30 years ago, which in that time has been cited zero times by actual physicists….”

    It may be of interest to note that Mr Smith, who also has become prolific here recently, has given a web address which was a similar, self-published lengthy writing. The author, supposedly a Melbourne lawyer, had not that name, but it is hard to believe, comparing the content and writing styles, that it is not the same person as gave the address.

    It has dawned on me, glancing through a number of these, that giving lectures in philosophy in many places (to undergraduates since I imagine a certain amount of this kind of stuff even here comes from philosophy undergraduates) must sometimes be an extremely trying occupation. I’m sympathizing with Massimo here, not you, since I realize your students are physics hopefuls, though I also realize you probably have to deal with ‘Einstein-denyers’, ‘one-way-speed-of-lighters’ and the like occasionally as well. I think my patience would have been sorely tried had it not been mathematics.

    As to the Smolin interview again, I haven’t yet got access to his books on this or any technical writing other than the reference the interviewer gave in one response. So maybe later, but I have to admit right now to being completely baffled, in trying to understand his point about (non)existence of past and maybe future.

    The very reputable mathematician Chris Zeeman (still around I think but he must be 90 or close!) once wrote a short paper showing how the causal partial order on Minkowski space implied just about ‘everything else’. This spawned a minor industry in a somewhat obscure area of geometry, which I don’t think ever caused any stir in basic physics. Actually Zeeman’s result did follow directly from something earlier: Back in the 30’s, there had been a book by a man Robb who showed how the synthetic geometry which corresponded exactly to coordinate Minkowski geometry could be axiomatized by a single binary operation which is the causal order. So in some sense, Minkowski is simpler than Euclidean geometry! But Robb’s axioms were somewhat baroque you might say.

    Anyway, one would hope that that Smolin paper I referred to above could be re-formulated in a style more familiar to run-of-the-mill mathematicians like me (rather than to quantum field theorists), one where their system is in a more ‘set with relations’ style, and where one of their theorems was the recovery of Minkowski space and special relativistic physics as some kind of limit, and other such theorems. This despite their system making no reference to space or space-time or quarks or gluons, but definitely making reference to ‘time’ in some form. That would help me, but perhaps be of minimal interest to physicists. Or maybe my lack of understanding what they are attempting makes the suggestion above out of the question.

    I do follow somewhat David Deutsch’s attempts, to the extent they have been published, with a similar basic attempt to find something for which both general relativity and quantum field theory arise as limits in some senses. But he is in the Everettian camp, and I don’t think Smolin and Penrose are (cf. the section on twistors in that paper), so there is likely little connection.

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  14. This post is a plea for help. I post it here in response to Marko because it is one of the posts where Cortes and Smolin’s model 1307.6167 is cited.

    I use the word science to refer to the process or method of science not its body of knowledge. I seem stuck or misunderstand the place “models” belong. For me they belong in the hypotheses’ generation phase. The phase Feynman called “thinking” in his three element method of science (Feynman, Six Easy Pieces). However “models” are used in this forum as “theories.” I thought theories were based on evidence, were tested hypotheses. Smolin’s model seems pure conjecture and interpreted mathematical results.

    The second law of thermodynamics tells me the direction in which time must proceed. It may be that such an understanding is lacking or superseded by newer information. I do not understand comments in this forum to the contrary that time is asymmetric or does not flow . I also do not understand suggestions that the cosmos might not operate according to the same laws we observe here and from here. I would certainly like evidence to the contrary.

    So, those are just a start of my understandings or lack thereof. Perhaps someone can steer me in a fruitful direction.

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  15. Ye must have faith is science too.
    I don’t.
    Science believes in or has faith in its devises of measure, time and space, so then dear science, what is the measure of now? How fast does now travel through time and space?. Do you measure now in a vacuum like the measure of light? Is now a constant too? If now and light are traveling through a void of space time continuum, is the vacuum still void? Is a vacuum measurable? And if now is not in a void, can it be measured? Is this where the smoke and mirrors comes into play? QM, uncertainty, or a hope and a prayer at best? Are not science and religion the same?
    Is nothing measurable? Is everything measurable? What is the measure of everything, nothing, something, anything? What is the scientific measure of measure? Is science in a vacuum too? What is right now? =

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  16. Peter Woit posted some comments on Smolin’s ideas.

    Coel, Phoffman56: No need to pick on other commenters. Start with the OP and Lee Smolin. Smolin says in his book (The Trouble with Physics, chap. 17, What is science?) that he almost dropped out of physics, but Paul Feyerabend persuaded him that science does not need to follow any rules, and you can just say whatever you feel like, regardless of the objective evidence. So Smolin promotes all these grand ideas that have little to do with reality.

    Woit attacked string theory because it has failed to do anything useful in physics. Smolin’s attack was from the other direction, and he complained that string theory was taking attention away from all the other useless and unverifiable ideas in theoretical physics.

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  17. schlafly, I haven’t read Woit’s comments on Smolin yet, but you are entirely wrong when you say that the two of them attack string theory from opposite directions: their criticisms are substantively the same. And good for Feyerabend if he was able to keep Smolin interested in physics!

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  18. This thread reminds me a bit of a courtroom scene where the objection “Asked and Answered” keeps being repeated, but the jurors can’t even tie the questions to the answers, or of a quote from the TV series House: “How does somebody who believes absolutely anything become a non-fiction writer?”

    Consider the venue. The commentary is, for better or worse, public discourse. One doesn’t have to be credentialed to participate. And yet all too often comments stray from the actual posts/articles to chatter between insiders of some scholarly discipline or some quasi-self-identifiable academic clan. Where the case for “public intellectualism” comes in is presumably the article itself. It is really a dilemma for SciSal to play referee regarding much of this while somehow balancing the objectives of the webzine. So I look forward to his two part article on Smolin’s thinking.

    Both Marko and Coel have weighed in on a question (complaint?) asked by one of the commentators. Marko, in particular, has tried to contextualize notions of time, space, and spacetime from the vantage of theories in physics. But having followed both SciSal and Rationally Speaking, it is not a surprise to me that some comments seem to reduce to “pet” theories. This is no more a problem for me than other comments that seem more designed to advertise one’s learning in a particular discipline than to address issues raised by the article itself. So asked and answered.

    But I would question whether there might be some ironic quid pro quo in recasting one of the comments here as follows: “If some XXX thinks that they’ve spotted some fundamental flaw that thousands of XXX have all overlooked, then the chances are that the lack of understanding is with them.” Chances are? Wow. Asked and answered.

    In terms of the articles presented here, understanding, or my personal appreciation of what I don’t understand, is the key word here for me. I’m not taking orals for an advanced degree when I come to SciSal or any other blog I read. So, would anyone like to address the article’s points? Asked and answered.

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  19. Schafli,

    One is not “pick(ing) on other commenters” by relating the facts that their comments here are restatements of parts of their unpublishable books.

    From observing Smolin ‘in action’, I am quite convinced that he is a serious scholar, certainly several orders of magnitude more able than me.

    While I agree with Weinberg (to the extent my agreement is of any value) that Feyerabend is more of an amusing and clever writer than a person whose scholarly output is of much value (that appears to be what Weinberg implied about him and Wittgenstein, but more politely), I don’t think that a young person who happens to have been inspired by that entertainment will necessarily not him- or herself later make valuable contributions.

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  20. Thomas,

    One remark about your recast

    “If some XXX thinks that they’ve spotted some fundamental flaw that thousands of XXX have all overlooked, then the chances are that the lack of understanding is with them.”

    is that the XXX to whom Coel referred is the “XXX” whose discoveries in quantum theory alone subsequently led to about 1/3 of the entire US national product, and which, more ominously, led to the spectre of nuclear weapons, and so on. It is not just any old XXX-group. An Einstein can revolutionize the truths previously found by that XXX-group, but it is very soon indeed that that particular XXX-group realizes that something very valuable has really happened.

    The two aspects of fundamental physics referred to above I have expressed in terms of effects on all of us, but do not wish to imply that that is the only, or even the main, criterion for its value, so let’s not start going on about that again.

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  21. Hi Wesley Johnson,

    I seem stuck or misunderstand the place “models” belong. For me they belong in the hypotheses’ generation phase. … However “models” are used in this forum as “theories.” I thought theories were based on evidence, were tested hypotheses.

    The answer is that physicists don’t place much store by exactly what words are used for such things. A “model” is pretty much the same as a “theory”. You’d tend to use the word “theory” in a more general context and the word “model” when you’re trying to calculate something.

    Thus a “model” is a set of ideas and equations that “models” an aspect of reality. For example a “model” of a star is a set of equations which, when solved, tells you the temperature, pressure and density at each point in the star. You could then use this model to calculate the amount of nuclear burning, and thence compute the evolution of the star.

    On the question of whether models/theories come before or after data, the answer is both. Science is an iterative process, where one has a web of models/theories, and iteratively improves the theories to better match the data. (Nearly all accounts of science which separate the process into different “phases” are over-simplifications.)

    Smolin’s model seems pure conjecture and interpreted mathematical results.

    So far it is, yes (which is not in itself a problem, since many good ideas start out like that).

    On another topic:

    Peter Woit posted some comments on Smolin’s ideas.

    People such as Woit and Smolin are a good counter to the suggestion that physicists are a cabal who won’t criticise each other because we are covering over basic flaws!

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  22. Hello Marko and thank you for pointing out the fuzziness of my question about, Smolin’s model and Feynman’s idea of sum over histories. It was the rest of my brief post for which I was seeking comment. I have understood sum over histories as a smooth progression, in the entire cosmos, of events from potential (probabilistic) future events to the present moment, where the potential event’s probabilities collapse to one, then flow into the past (become the past). My view may be way off the mark and fuzzy (using imprecise language) as might be my understanding of Smolin.

    Smolin sees each moment as the possible parent (precursor) to the future. He says; “Our thought is that each moment or event may be a parent of future events.” I think he is correct in the sense that events in the present moment produce future probabilistic events that at some other present moment collapse to one completing that present moment.

    He has need of a “thick” present to allow present events to generate future probabilities of events as well as that event’s probabilities to collapse. When he says; “A present moment is one that has not yet exhausted or spent its capability to parent new events.” I understand it to cover both parenting other events and future probabilities collapsing to one at the present moment.

    About the past he says; “Past events were those that exhausted their potential and so are no longer involved in the process of producing new events, they play no further role and therefore there is no reason to regard them as still existing.” Yes of course, once the present is fully determined by future event probabilities collapse and generating future events the present becomes the past.

    An example. In the present moment my car is struck by a stone which dropped from an overhead bridge. I may or may not find out later (it really does not matter) that the stone moved and fell due to years of bridge neglect and physical processes of freezing and thawing. Years ago bridge neglect set in motion the probability conditions which lead to the stone’s moving. At some time in the future the stone has a fall probability ranging from essentially zero to 1. Over the years the probability changed and then collapsed to one in the present moment. The probabilities prior to the present moment were determined by many factors such as replacing or repairing the bridge, the traffic on the bridge over the years, and so on. But in my example present moment we will say the other possible factors were not manifest and the probability of stone fall kept increasing until it collapsed to one. I was driving my normal route as I passed under the bridge in the present moment and the stone fell. However, I left earlier than usual so that event changed the combined, but not causally linked, probabilities resulting in being struck by the stone. There are so many more collapsed probabilities, some casually related and some not in the unique event of my car struck by a stone, I certainly cannot begin to compute them. It is very complex.

    Comments please.

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  23. Hi Coel:

    Thank you for your response. Given that Scientia Salon is: “from the Ivory Tower to Main Street, and vice versa.” The interchangeability of model and theory seems unfortunate. Although, as you point out, “model” is more specific than “theory.” I do understand mathematical models as I have developed a few to predict, in one case, the bone strength consequences of osteoblast inhibitors. At the current stage of Smolin’s work I would call it a model, a beginning model. When it can really predict something it might graduate to theory or remain a model used as a tool.

    Simplifications are a requirement to communicate with Main Street. In speaking with intelligent people in the Humanist and Atheist communities defining theory in the scientific sense is difficult.

    I certainly agree with you that there is no physicists’ cabal and that Smolin’s work will evolve as it is challenged and reviewed. 🙂

    Again, thanks for your response.

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  24. I enjoyed the interview and the comments. I feel there is something to Smolin’s ideas, and they seem to mesh with some of my ideas about ways to speak of things. Things? I wouldn’t dare say more without some serious though, and without reading more about what Smolin and Unger are thinking. So I’m looking forward to Massimo’s review(s).

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