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Consciousness as an active part in modern physics

  1. Nov 20, 2005 #1

    vanesch

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    Hi,


    after some PM discussion that went into this direction and a short check, I want to persent here a summary of some of the ideas involved concerning a link between the consciously experienced subjective world and physics. First of all, it is probably interesting to find out the controversy between "materialism" (which states that the physical world includes whatever is "consciousness") and "dualism" which is supported by some arguments that the physical world can never entirely explain all aspects of consciousness. A summary of the concepts involved can be found here:

    http://www.iep.utm.edu/c/consciou.htm


    What I will write here subscribes in a way to the dualist notion, where consciousness is something extra-physical. However, it finds its roots in the physical world.


    My point was the following: modern theories of physics (GR and QM) need a non-trivial relationship between the physical ontology (corresponding to a mathematical object in the theory) and the subjective experience by consciousness. This is in contrast to the Newtonian frame where a much more evident 1-1 relation can be seen. In order for this to make sense of course, some form of a dualistic vision on consciousness is necessary because a purely materialistic view cannot do.

    But first, what about the Newtonian frame ? In the newtonian frame, one can (almost) keep a purely materialist vision, if one associates consciousness to a physical structure (say a brain), because it is possible, because of the *physically ontologically meaningful concept of universal time* to recognise an ontologically existing 3-dim space with a brain state, which will then evolve according to that other, ontologically existing universal quantity, time, which "ticks away".
    Of course, in a deterministic Newtonian frame, it is always possible to construct a 4-dimensional "static" manifold, and as such to attach an ontology to a 'spacetime'. This remark is sometimes made, that there is no fundamental difference between the 4-dim static manifold in Newtonian physics, and in relativity. However, the point is that this 4-dim manifold in Newtonian physics is entirely facultative. We don't NEED the concept of a 4-dim manifold as an ontological reality in Newtonian physics.


    What happens in GR ? There, the postulated ontology is a static 4-dimensional manifold. We now NEED this structure, it is not facultative anymore. GR has no real meaning without the concept of a 4-dim manifold. So "yesterday" and "tomorrow" are different regions of that manifold (and even only make sense with respect to a specific world line). Yesterday exists no less than tomorrow or today. Nevertheless, we are consciously ONLY aware of "today". So I argued that you need AN EXTRA POSTULATE which maps, in a non-trivial way, the entire "state of the brain" which is a 4-dimensional structure (the worldline of the brain) onto ONLY ONE SLICE corresponding to "now" and that slice is what is subjectively experienced by the consciousness that is conjugated to that brain.
    Although that brain's birth still exists somewhere on the manifold, and its death too, the consciousness of the brain only experiences ONE slice of it, namely the "today" slice. And as there is NO ontologically existing universal time parameter anymore, "ticking away", there is no PHYSICAL way to select this timeslice. This has hence to be done by a non-trivial mapping from the physical ontology (4-dim structure) to the subjective experience of a conscious being. However, this is often not explicitly stated, because locally the equations LOOK like those of a Newtonian observer, with his space and time coordinates. Nevertheless, the time coordinate is now just that: a coordinate. It is not a physically existing quantity anymore that has a specific value (and hence determines a specific slice). In Newtonian physics, one could claim that only ONE value of the time parameter "had ontological existance" (and that yesterday and tomorrow did not exist). This is not possible anymore in relativity.


    Next comes in quantum theory. A popular (although not (yet?) standard) view on quantum theory is the relative state (or many worlds) interpretation, which claims essentially that ONLY ONE TERM in the cosmic wavefunction is consciously experienced by a conscious being - which explains the apparent probabilistic nature of QM. Usually, this meets a lot of critique because "introducing consciousness in a physical theory is somehow a bad idea". But I wanted to argue that *this was already the case when we took up general relativity with its spacetime manifold*.
     
    Last edited: Nov 20, 2005
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  3. Nov 20, 2005 #2

    vanesch

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  4. Nov 20, 2005 #3

    hypnagogue

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    Hi vanesch, thanks for the interesting argument. A couple of questions and comments:

    1) How, if at all, does entropy figure into the story here? If we take it that the arrow of time is fixed by the manner in which entropy in a system tends to increase (which is a purely physical phenomenon), how does that factor into your argument?

    2) What exactly is meant by a timeslice? I assume you mean something that captures spatial extent but not temporal duration. However, on the objective side, it's not clear that any given conscious event can be meaningfully mapped onto a spatial 'snapshot' of the brain; that is, the minimally sufficient physical conditions in the brain that are associated with conscious experience may all involve physical events evolving through time. On the subjective side, it seems that even the most temporally compact components of consciousness actually occur over a duration of time (the so-called "specious present"; see here for an elaboration). So the physical mapping problem might not be one of picking out individual timeslices, if a timeslice is understood to have no temporal duration.

    3) It might also be fruitful to give some consideration to cognitive functions. Might one be able to say that the manner in which our brains store short term and long term memories, and the manner in which these memories inform our current conscious experience in the here-and-now, is something that may create an illusory sense of the flow of "now" out from the past? If not, why not? If so, might this be a way of solving the problem of consciousness of the 'now' without needing an explicit mapping of the kind you mention?
     
  5. Nov 21, 2005 #4

    vanesch

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    First of all, I'd like to point out that what I wrote is of course speculative. I only wanted to indicate that we could take "a step back" when considering the relationship between consciousness and physical reality, by associating a conscious experience not *directly* with that physical reality, but through some "window" ; that window itself being of course not a physical degree of freedom (otherwise we'd be back to case 1). I'm brought here mainly because of the relative-state interpretation of quantum theory (in my opinion the only one that sticks to the currently existing formalism - which doesn't mean it cannot change in the future). But it occured to me, as I said, that one already has to postulate such a relation in the frame of classical relativity - though on a much less involved way.


    If we accept that a conscious experience "just is", then we could argue that the "illusion" of an arrow of time is given by the memory of the body, which has clear correlations with macroscopic quantities in what's experienced as "the past" and doesn't have any "souvenirs" of these macroscopic quantities in what's experienced as "the future".
    A bit like on a picture (= the conscious experience) of somebody running, you have a clear indication of the motion of the person, although it is a static image. In other words, we define past as "what we remember" and we define future as "what we expect".

    Yes, and (in relativity) the brain is not a single point of space either. So we are actually talking about associating a conscious experience with a rather localized lump of spacetime, which, in the eigenframe of the brain, would extend spatially over the width of the brain, and in time, over the typical "time it takes". So the "window" would not be a singular function, but some smooth weighting and averaging function over a small region of spacetime.
     
  6. Nov 21, 2005 #5

    vanesch

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    This is an argument that was already made, but the point I'm trying to make is not so much "the arrow" as "the position". Why am I experiencing "today" and not "my birth", or my 20th birthday, or my 80th birthday (if that one exists) ? All these moments are on an equal level, ontologically, in relativity (at least, that's how I understand it), because the 4-dimensional manifold has ontological existence. It is *this* which is different in Newtonian physics, because "universal time" could have a specific value, which is "now", and my 20th birthday has no ontogical existance, nor my 80th birthday. I mean, the "pointer" on the Newtonian time axis could be something "real out there" (and then of course I only experience what corresponds to that pointer: it is part of the physical ontology). But in the static 4-dim manifold, there is all right an eigentime, which is a COORDINATE along the worldline of the brain center of gravity, but ALL of the points along this line have "equal physical ontology". There's nothing that singles out "today" from other points. So it seems that something "ticks" along that line, as was the universal time in the Newtonian frame. But that "something that ticks" has no physical ontology. It is "integrated in the window function that puts up the relationship between my brain and the subjective experiences that go with it" (at least, that's what I'm proposing here).
    You could even put "many trains of consciousness" on the same brain (4-dim structure). Maybe another consciousness is experiencing my birth. And another one is experiencing my 80th birthday. But the one "I" have, is now typing on PF.
     
  7. Nov 21, 2005 #6
    As I said in our PM, your just like too much science fiction and Newtonian physics. :smile: First of all, I do not see why the Newtonian situation is different from the one in GR (in this respect), since in your reasoning, you would need a universal awareness of the *value* of the time parameter. Both in Newton and GR, you are dealing with time reversal invariant *deterministic* systems, implying that you can compute how it was for t < t_0 and t > t_0. In that sense, the past and future exist, but that does not imply of course that we observe them now (in Newton at t=t_0, in GR at the specific gauge fixed starting point of your worldline where you decided to evolve the Einstein equations). So, I give you again the GR intepretational scheme which does not need any sort of consciousness:
    (a) the Einstein equations are objectively true
    (b) our fluid matter models (where the fluidum is constrained to satisfy the weak energy condition) are adequate, and the ideal PLATONIC matter model satisfies the same constraint
    (c) local time for a matter density = eigentime of the corresponding worldline
    (d) observation : at a particular small interval of your worldline you recieve signals coming from the thickened past lightcone, you process them like a computer and have a limited visibilty such that signals with a too weak intensity go unnoticed.
    (e) fixing the initial conditions : repeat (d) long enough such that you can make a reasonable extrapolation in order to guess what happens at that part of the universe where you cannot be

    (d) implies you observe a smeared out *localized* now, since you can process signals such as the ticking of your watch at a rate according to (c) - relative motion is enough to get a (non universal) now! It is obviously incorrect to state that all points along a worldline have the same ontological status, the are clearly distinct (for example because they have a different past) (c) can even be dropped to some extend by going over to Weyl gravitation. (e) is a necessary requirement in every physical theory, even Newton.

    It seems to me you are wondering *where* you are on your worldline. In GR the situation is vastly BETTER in that respect than in Newtonian physics since we have a universal PHYSICAL starting point (that is our extremely tidy big bang), in Newton, we can make any time translation we want. So you can express your moment of birth in the physical time it took for local matter densities to group together into an embryo you are starting from the big bang (you can even know objectively which of these clumpings you are in the 4-D manifold by studying your past).

    You seem to have the strange idea that although you experience now monday 21 of November 2005, there might *now* be a copy of you on a worldline very close to yours at a date you labelled 13 december 1975.
    That is of course entirely excluded and even meaningless in GR : *now* has a local meaning (as prescribed before) and the earthly *now* is a matter of AGREEMENT; we earthinhabitants have once met at one place and set our watches equal and departed again. For earth, such procedure works well since the gravitational field is very weak. In the good old times, *now* was relative to the position of the sun at the sky or the position of the wave front at the beach in one of its tides (the Greeks were more relativists than Newton in that respect). So, *now* for you cannot be linked to *now* in 1975 by CONVENTION and as mentioned before, they are clearly distinguishable by their past relative to the BB (not: big boobies :biggrin: ).
     
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  8. Nov 21, 2005 #7

    vanesch

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    No, this is exactly what I tried to point out. In Newtonian mechanics, you CAN CONSTRUCT, if you want to, a 4-dimensional "spacetime" (that is what you do when you say that you can calculate solutions for all values (past and future) of t. But, I can consider that as a mathematical nicety that DOESN'T HAVE TO CORRESPOND TO AN ONTOLOGICAL REALITY. A bit like I could do complex continuation of, I don't know, any real function. It is not necessary to associate this complex continuation to a really existing thing out there.

    You CAN get around, in Newtonian physics, with assigning only an ontology to a certain time slice. There could be some universal godfather or whatever (I don't want to get into religious debate here of course, it is just a pictorial representation) that PUTS THE TIME DIAL TO november 2005. As such, time is not a "parameter" but a value of an ontological quantity. It also corresponds to a parameter in our theory, and if we put the value of the parameter in the theory equal to the value the deity put on the dial, then we will find the "world right now". Then there is only ONE reality, namely the one corresponding to the time dial set by that deity. And we can of course use the laws of nature as to how this reality looks like when he puts the dial to another value.



    Yes, but the ontology of GR makes that the embryo I was, is still there, and my dead body too. It has no less existance than my body I experience right now. Nevertheless, I don't feel like I'm dying or being an embryo. In Newtonian physics, you can simply say that there is NO ontological existance to me being an embryo or me being dead, because this only happens when the deity puts the dial onto the right value, which he didn't: he put it to november 2005. So there's only an ontological reality to november 2005. So it is normal that I'm aware of my body in november 2005. But you do NOT have your universal dial anymore in GR. Some part of the manifold is still my birth, some part is me dying, some part is my 20th birthday, and some part corresponds to november 2005 for me. I only experience november 2005. Why ?


    I can assure you that it is not a convention that I'm not having my twentieth birthday party right now, or that I'm being born right now. BTW, I was not talking about a copy on a worldline CLOSE to me, I was talking about a copy on MY worldline, but on another value of my eigentime. Maybe a copy of me IS having a party as my 20th birthday. Why is that copy experiencing that, and not me ?
     
    Last edited: Nov 21, 2005
  9. Nov 21, 2005 #8
    ** No, this is exactly what I tried to point out. In Newtonian mechanics, you CAN CONSTRUCT, if you want to, a 4-dimensional "spacetime" (that is what you do when you say that you can calculate solutions for all values (past and future) of t. But, I can consider that as a mathematical nicety that DOESN'T HAVE TO CORRESPOND TO AN ONTOLOGICAL REALITY. You CAN get around, in Newtonian physics, with assigning only an ontology to a certain time slice. There could be some universal godfather or whatever (I don't want to get into religious debate here of course, it is just a pictorial representation) that PUTS THE TIME DIAL TO november 2005. **

    You DO need the Universal godfather to obtain what it is you want but again, it is wrong. There is NOTHING in Newton which gives you t=0 PHYSICALLY and in our calender t=0 is the birth of Jezus Christ. If we would take the birth of the profet Mohammed and stick to the counting of time which is inspired by the physics of our solar system then we wouldn't be in 2005 now. In GR, the big bang does this for us in the most natural way.

    ** As such, time is not a "parameter" but a value of an ontological quantity. **

    Time is of course a parameter in Newtonian physics (this is universally accepted by earthlike physicists).

    ** Then there is only ONE reality, namely the one corresponding to the time dial set by that deity. And we can of course use the laws of nature as to how this reality looks like when he puts the dial to another value.
    Yes, but the ontology of GR makes that the embryo I was, is still there, and my dead body too. It has no less existance than my body I experience right now. Nevertheless, I don't feel like I'm dying or being an embryo. In Newtonian physics, you can simply say that there is NO ontological existance to me being an embryo or me being dead, because this only happens when the deity puts the dial onto the right value, which he didn't: he put it to november 2005. **

    The SAME thing is achieved by my postulate (c). Why are you refusing to comment on this ??? You basically ask me what in GR would tell me that my unborn children do not´exist yet. And I tell you that GR dynamically provides you with a t = 0 (the big bang), which in conjunction with (c) gives us a (local) arrow and measure of time. Moreover, GR is a ONE WORLD theory, so the FACT that I live and experience a localized now (and that I have such and such distance to the big bang) implies that my unborn children do not yet exist. Perhaps, you want to engage yourself in a discussion why I know that I exist and why I think the clock which is ticking next to me is not imaginary. This is IRRELEVANT: the fact that I percieve a ticking clock in conjuction with (a) the one world in GR (b) my hypothesis (c) and (c) the big bang is sufficient to lead to the latter conclusion. I do NOT have to bother about the possible existence of other worlds: that is the beauty of GR. This implies that my dead body has not the same ontological status as I have for me and all other people I meet. GR tells me only to bother about the WORLD within my perception, that is the signals I (the machine) recieve, that is what RELATIVE means. Now, you can start arguing that we are not all equally calibrated: that is why in physics we use more simple and predictable machines which are easy to calibrate. So, the philosphy is that as long as there are no mechanisms which can bring ourselves back into our past (future), the past (future) does not *exist* (by definition) anymore (yet).

    ** So there's only an ontological reality to november 2005. So it is normal that I'm aware of my body in november 2005. But you do NOT have your universal dial anymore in GR. **


    The point of GR is that 2005 is NOT UNIVERSAL at all, it is a mere agreement which works well because clocks tick almost like in Minkowski on our planet !

    ** Some part of the manifold is still my birth, some part is me dying, some part is my 20th birthday, and some part corresponds to november 2005 for me. I only experience november 2005. Why ? **

    See the previous... (by definition)

    ** I can assure you that it is not a convention that I'm not having my twentieth birthday party right now, or that I'm being born right now. **

    Yes, it IS! See the previous...


    ** BTW, I was not talking about a copy on a worldline CLOSE to me, I was talking about a copy on MY worldline, but on another value of my eigentime. Maybe a copy of me IS having a party as my 20th birthday. Why is that copy experiencing that, and not me ? **

    Worldlines in GR are only assigned to ONE matter density, my postulate (c) avoids this complication.
     
  10. Nov 21, 2005 #9

    vanesch

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    I'm of course not talking about the 0 of the time scale, which is only a coordinate on the 1-dimensional time manifold in Newtonian physics. But in Newtonian physics, you can give an ontological meaning to that parameter, because ONE point on that axis is special, it is "now". (Newton said "time flows uniformly", so he meant that this point is somewhere on the time axis, I presume). The coordinate of that special point is what we call "t", in Newtonian physics, and of course the value of that point t depends upon how we have choosen to label the non-special points on the axis.

    But in GR, there is no such special point. There may be a special point which is the big bang (then why am I not experiencing the big bang - apart of course from the fact that I didn't exist). But what's special about today ? I can calculate the eigendistance from "today" to other events, true, and I will find that that agrees. I'm not saying that I'm supposed to find disagreements. I'm just saying that there is something special about "today" because I experience "today" and that there is NO way, in GR, to make "today" special over "yesterday" and over "tomorrow". In Newtonian physics there was such a means, because of the universal time (not the universal measure of time with respect to some "origin", no, the fact that time was an ontologically existing thing in nature, which could, hence, have a specific point which was "today" and which denied ontology to the past and the future. That would then mean that there is no sense to be given to "me experiencing consciously last month", because nothing ontologically exists corresponding to "me last month". But "me last month" exists very well in GR, so I don't see why this is not consciously experienced - but I know that that's not "me" (maybe another "me" does experience this).

    So something has to single out "today" as special on my world line. Not that I cannot calculate back on my world line what my age is - it will fit with the other parts of my conscious experience (namely what I saw on the calendar and so on). But "me yesterday" exists. "me tomorrow" exists. Nevertheless, I don't experience it. I only experience "me today". What distinguishes "today" from "tomorrow" or from "yesterday" on my world line?

    Well, time is a coordinate system on a one-dimensional manifold. But "today" is not a parameter of course, it is a special point on that one-dimensional manifold.

    No, because the same body of yours also has a slice with a slightly bigger distance to the big bang where you DO have your children. We all agree that the slice of time which you experience right now is a bit closer to the big bang, and that this is fully compatible with you not having your unborn kids yet. But we all agree also that there is another slice, still a bit closer to the big bang, when you were a kid yourself. So why are you NOT experiencing THAT slice, or that FUTURE slice, but only "today's" slice ?

    No, that's not what I want to discuss.

    There's a slice of "you" who looks at the clock and sees 9 PM
    There's another slice of "you" who looks at the clock and sees 8 PM
    There's still another slice of "you" who looks at the clock and sees 11 PM
    ...
    You only are consciously aware of ONE slice. Why ?
    In newtonian physics, there could be a "kink" on the timeline that says "now", making that point special. But not in GR.

    Hehe, I almost got you into MWI here ... :biggrin: But let us keep to GR for the moment.

    Now that's hard to do in GR, isn't it ? Can chunks of the 4-manifold be declared "not existing anymore ontologically", so that only your time slice "now" exists ? And the future timeslices "come into existance" ? THAT is exactly what I could do in Newtonian physics because I didn't NEED the ontology of the 4-manifold. But in GR, I'm screwed if I try to deny existence to certain events, no ? Because it would introduce a foliation of the manifold ?


    You're starting to get parts of my argument, great :approve:

    If november 2005 were universal, then that could have been a special point with "now" status. But in GR you cannot do that. So NOTHING physical can be postulated to single out november 2005. Nevertheless, that's what I'm consciously experiencing. So this is the NON-TRIVIAL RELATION BETWEEN PHYSICAL ONTOLOGY (the 4-manifold and the part of it that corresponds to my brain) and my subjective experience of "it is november 2005 and I'm typing on PF".

    I don't know about you, but I do NOT have the subjective experience of being born right now... :tongue:

    Because yesterday there was no matter ? It is only there today ? :confused:
     
  11. Nov 21, 2005 #10
    **
    But in GR, there is no such special point. There may be a special point which is the big bang (then why am I not experiencing the big bang - apart of course from the fact that I didn't exist). ***

    Hem, hem, denial of the BB is enough to get kicked off this forum as far as I understand :biggrin: I would miss you though :tongue2:

    ** I'm just saying that there is something special about "today" because I experience "today" and that there is NO way, in GR, to make "today" special over "yesterday" and over "tomorrow". **

    Again, this is my postulate (c). I gave you a logical explanation for this, the rest you say about why newtonian physics *can* make sense of this applies also to my scheme (this is just logic since (c) is nothing but a LOCALIZED NEWTON HYPOTHESIS).


    ** So something has to single out "today" as special on my world line. Not that I cannot calculate back on my world line what my age is - it will fit with the other parts of my conscious experience (namely what I saw on the calendar and so on). **

    (c) does that in my scheme


    ** But "me yesterday" exists. "me tomorrow" exists. **

    No, no, perhaps in another world, but not in mine and all fellow compadres I meet. I gave you the logical reasoning already. If you would be so kind to give a specific comment on that...


    ** Nevertheless, I don't experience it. I only experience "me today". What distinguishes "today" from "tomorrow" or from "yesterday" on my world line? **

    (c) + the fact that I exist (and you were not going to doubt that).

    ** No, because the same body of yours also has a slice with a slightly bigger distance to the big bang where you DO have your children. We all agree that the slice of time which you experience right now is a bit closer to the big bang, and that this is fully compatible with you not having your unborn kids yet. But we all agree also that there is another slice, still a bit closer to the big bang, when you were a kid yourself. So why are you NOT experiencing THAT slice, or that FUTURE slice, but only "today's" slice **

    Because I exist and by comparison see that I am an (physical :tongue:) adult.

    ** No, that's not what I want to discuss.
    There's a slice of "you" who looks at the clock and sees 9 PM
    There's another slice of "you" who looks at the clock and sees 8 PM
    There's still another slice of "you" who looks at the clock and sees 11 PM
    ...
    You only are consciously aware of ONE slice. Why ? **

    (c) + I exist.

    ** Hehe, I almost got you into MWI here ... :biggrin: But let us keep to GR for the moment. **

    Don't sell the skin of the bear yet :tongue:

    ** Now that's hard to do in GR, isn't it ? Can chunks of the 4-manifold be declared "not existing anymore ontologically", so that only your time slice "now" exists ? **

    There is no time slice involved (how many times do I have to repeat that). There is only my world line, me = I exist, and the past lightcone of me = NOW (the rest is just extrapolation and guesswork based upon data over a large period of time we recieve); therefore my universe and that of my compadres which I meet.

    ** And the future timeslices "come into existance" ? THAT is exactly what I could do in Newtonian physics because I didn't NEED the ontology of the 4-manifold. But in GR, I'm screwed if I try to deny existence to certain events, no ? **

    No, the only relevant future is my future lightcone (I do not need to bother about the rest). Look: call myself A and you B, I send a signal to you, 3 minutes later I recieve a signal from you in which you communicate what you have done in the time between recieving my signal and sending back yours according to your local clock. Based upon MY personal knowledge (and whatever I can look up in the library) I can make a reasonable space time MODEL and guess the moment at my worldline when you recieved my signal (by using my local notion of space and the exponential map in my pet space time). Nature seems to tell us that there exists a *universal* arrow of time such that all these local PET spaces coincide.

    ** Because it would introduce a foliation of the manifold ? **

    NO, NO, NO....

    **You're starting to get parts of my argument, great :approve:
    If november 2005 were universal, then that could have been a special point with "now" status. But in GR you cannot do that. So NOTHING physical can be postulated to single out november 2005. **

    YES it can, my ancestors, 34 bloodlines ago met in the past at planet earth to decide upon one clock measure and starting point. Since then clocks are ticking and everything is registered. This meeting CAN be dynamically singled out in GR (local matter densities clumping together and specific sound waves being created).

    **
    I don't know about you, but I do NOT have the subjective experience of being born right now... :tongue: **

    I am registering typing at my computer now.


    **Because yesterday there was no matter ? It is only there today ? :confused:[/QUOTE] **

    Yesterday there was matter, and tomorrow there will be. I know that yesterday has past because my distance to the BB has been increased. You seem wanting to pull me into a many world declaration for physics, comment first specifically on my single world theory.
     
  12. Nov 21, 2005 #11

    vanesch

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    Your postulate (c) was:

    Does that mean now that what is consciously experienced "now" by any matter density is a special value of eigentime since the big bang ? Is that what you mean ? The value of eigentime since the big bang that *for me* corresponds to the number of seconds along the worldline of an electron in my brain that corresponds to "november 2005" and that all conscious creatures are experiencing THAT number of seconds ?
    But, not all particles making up my brain will have the same "eigentime since the big bang", and I can imagine that certain brains will made up of particles that had a slightly longer or shorter worldline since the big bang. As such, what is "november 2005" for my neighbour (as measured since the big bang along the eigentime of the worldline of my neighbour's brain) might very well cross MY eigentime of the worldline when my eigentime reaches october 2024. Does that mean that my neighbour is experiencing something in what for me is his past (because we all are experiencing a certain eigentime which corresponds to "november 2005" since the big bang, right ?) ? That while I see him, he's in fact not conscious of the state that I see him in, but that he's still experiencing when I had my birthday party (where I invited him) some 19 years ago, while I see him in "his future" right now ?

    No, this is not tenable. There is no specific value of eigentime since the big bang which indicates that THAT eigentime is now to be experienced consciously, by all conscious creatures (and not the day before or the day after). In Newtonian physics, that WAS possible: you could postulate that there WAS a special time, called "now" (and which, according to a certain coordinate system, got the coordinate "november 2005") which IS to be experienced by all conscious creatures, simply because OTHER times could be postulated not to exist ontologically.

    But you cannot postulate my past "not to exist" on the 4-dim GR manifold. You can only postulate my past "not to exist for ME, when I am on a specific point on my worldline" but clearly that is only related to my conscious experience of "now".

    This is what I am trying to make clear. That there is a non-trivial relationship between a special point on my worldline, and my subjective experience, such that that special point corresponds to my subjective "now" experience.
     
  13. Nov 21, 2005 #12

    vanesch

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    I would like to add the following to my previous post, in order to make sure that there is no elementary misunderstanding.

    I understand your postulate (c), and I know that the eigentime, as a coordinate along the worldline plays perfectly well the role of the t-parameter in dynamical equations, and if things are slow enough and flat enough, that this coordinate coincides with a local Newtonian model. I'm absolutely NOT putting that in question. I know that this parameter gives rise to about the same equations of any time evolution that one can think of, like, say, the diffusion of some ink in a glass of hot water, or the propagation of a signal through some wires or whatever usual dynamical phenomenon one can think of. And indeed, this establishment often leads people to conclude that this parameter (eigentime) is then the local equivalent of what used to be the global time parameter in Newtonian physics. I think this is what you try to explain me since a few PMs and posts. But I'm NOT disputing this at all. I know that, no problem - maybe in the mean time, you think I have a totally weird view on GR (not to say that I totally misunderstood the theory).

    What I'm saying is only the following. This eigentime t is a coordinate, which you can turn into a parameter which parametrises successive time slices, "just as in Newtonian physics, only locally". Up to there, no problem. The problem resides in THE ONTOLOGY. If you only consider t as a parameter occuring in an equation in Newtonian physics, you would have the same problem as the one I am trying to outline. But in Newtonian physics, you can AVOID simply calling t a "parameter", you can give it the meaning of the coordinate of a really existing timeline out there on which there is a special bubble, called "now". This option exists in Newtonian physics. It is rarely if ever explicitly said, but it can be done ; if that's done, you can give special status to "now" ; you can even go as far as to say that only that spacetime slice in the Newtonian spacetime has ontological existence, "is" out there. As such, the fact that I experience subjectively "now" is no mystery: it is the only thing which exists out there.

    But it is THIS possibility which is not possible anymore to the local t parameter in GR on a world line. There, it is reduced to just being a coordinate, which indeed parametrises the space slices along the world line, and which occurs in dynamical equations, but which has NO special status for "now"... unless you explicitly INTRODUCE such a "now" point ON EACH INDIVIDUAL worldline of a conscious being, and associate that "now" point with the subjective conscious experience of that being. But it is not a *physically indentifiable point*.
    And you are getting closer to it when you say:

    or:

    where there's an embryo of the idea that *something* else is needed to PICK the "now" point along your body's world line ; you call it "I exist", "my universe" etc...

    The "I" that "exists" indeed: your subjective experience which experiences "now" and which corresponds to a particular point on that worldline.

    The other points on your worldline can correspond to "souvenirs of yourself of some time ago" but infact they are not: those souvenirs are encoded in the structure of your brain NOW (otherwise you would not remember them), and to what you project yourself into in the future (and of which your brain has no souvenirs). Nevertheless, if we take GR seriously, those future points EXIST on the same level as the "now" point, or as the past points on your worldline. But you only experience ONE point of it, and that's what I'm trying simply to indicate: you only experience a part of what "is" out there ; one point on your entire worldline.

    You feel of course where I want to go to in MWI: if the quantum state of your body consists of several terms, you can then only experience ONE of these terms, in the same way as you only experience ONE point along your worldline in GR. I admit that it is weirder, more involved, less clean and all that. But the basic idea is that the picking out of ONE particular aspect of the state of your body (one point along the worldline ; one term in its wavefunction) and have this aspect of its physical state determine your subjective experience, is not an inconceivable proposition.
     
  14. Nov 21, 2005 #13
    ** Your postulate (c) was:
    Does that mean now that what is consciously experienced "now" by any matter density is a special value of eigentime since the big bang ? **

    I simply say that I exist and (c) indicates the rate at which MY time is running, therefore I experience a ``now´´. The big bang just indicates the beginning of time and I can express my position on my world line relative to it. Now, as a robot, I recieve mainly signals from other organized matter forms in my past (recent) lightcone (recent can be well defined by using the exponential map and the priviliged notion of space defined by my worldline) since signals coming from far away are too weak to be noticed (unless they correspond to focused bundles such as can be achieved with a laser). In these signals I can recognize shapes and structures (by making use of my database) and I can imagine how the world is beyond me extrapolating the knowledge I have from the past.

    ** Is that what you mean ? The value of eigentime since the big bang that *for me* corresponds to the number of seconds along the worldline of an electron in my brain that corresponds to "november 2005" and that all conscious creatures are experiencing THAT number of seconds ? **

    No !! My brain exists only due to a particular matter clumping in the ovary of my mother (the time of construction of the ``computer´´ by the parents). Since then, I am learning through observation using the decoding device which is stored in my genes and historical records of any kind; moreover I am capable of improving my learning capacities. I am existing through my own observation, and the observation of others. November 2005 is just a time agreement between certain nations on the globe (and actually 5 november 2005 in China, could well be 4 November 2005 in the US).

    ** But, not all particles making up my brain will have the same "eigentime since the big bang", and I can imagine that certain brains will made up of particles that had a slightly longer or shorter worldline since the big bang. **
    Sure, but that is not relevant (this is just a variant of the twin paradox). Neuron (A) at an instant I_A can communicate with a neuron on a neighbouring worldline INDEPENDENT of the history the material which made up this other neuron (B) has since the big bang (actually it has for sure not been a neuron for most of the time).
    What I call neuron A could have been already in 500 people (and be born and desintegrated 500 times), it could even be made up of dust of several other neurons) while neuron B only in 499 cases. This is easy to imagine since a neuron is simply a very specific low entropy entity which has only a structural stability for a finite amount of time. Thus it is only relevant how old the last structurally stable neuron is (and its moment of birth has been roughly registered by my mother).

    ** As such, what is "november 2005" for my neighbour (as measured since the big bang along the eigentime of the worldline of my neighbour's brain) might very well cross MY eigentime of the worldline when my eigentime reaches october 2024. **

    True (in principle but not in practise on the scale of the earth), but this is not the issue. November 2005 is an agreement for a particular piece of the globe.

    ** Does that mean that my neighbour is experiencing something in what for me is his past (because we all are experiencing a certain eigentime which corresponds to "november 2005" since the big bang, right ?) ?

    As said: eigentime is *not* the clocktime we use on the continents: even if you fly over the ocean there is a small twin effect. It is just that these two notions of time coincide very well in practice (due to the weak gravitational field and the relatively low velocities when compared to c). Perhaps it is good to give a definition which says when two material objects A and B (I am A and you B) are in the same world and ``aware´´ of each other. Take A on a particular instant I_A of its worldline (between its birth and death) which he calls now (this is an allowed statement because of (c) and A says ``I exist´´), suppose A recieves signals (at that instant) which show another robot B (which he assumes not to be transmitted by a third party), then A has knowledge of B (for example creatures at the other end of the universe which recieve a message from the second world war). Now suppose A recieves a message from B (which was sent at t_B on his clock) and sends immediatly a copy of this message back + another question which is recieved by B at r_B, then A is in the communication range of B and all events of B in the interval [t_B, r_B] cannot be distinguished by A at I_A. Morover, in this interval B experiences A to be ``present´´. Now, signals turn 8 times around the earth in one second and human perception time is around 1/10 th of a second. Therefore, for all practical purposes on the dimensions of the earth t_B = r_B. This is the *illusion* of simultaneity concerning all inhabitants on the earth and it is actually the interval [t,t+1/10] which WE call now. Obviously this *now* will not be the same for someone else at the other end of the universe. This is how we make observations in reality, we are not aware of a *spacelike* slice in the universe. I see now you have posted something else, but I will respond to that later on.
     
  15. Nov 21, 2005 #14

    vanesch

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    Concerning the quote below, thank you, but I know all that. I'm simply not able to make you see the point I'm trying to raise, sigh.

    You are explaining me below why it is that, ONCE I AM IN A CERTAIN POINT ON MY WORLD LINE, I experience things the way they are ; what I experience when I'm doing experiments with clocks in airplanes and all that. But I'm not disputing that at all.

    I'm just saying that you're only experiencing A CERTAIN POINT ON YOUR WORLD LINE, which is a special point, called NOW.

    This is "strange" because the other points on your worldline ALSO exist, not simply as a mathematical construct, but they are postulated to exist "out there". But you don't experience them. So something singles out that NOW point over all the others. ONCE you have accepted that you experience that point, all the rest follows of course, and you will find consistent results.

    This is different in Newtonian physics: you can postulate that "yesterday" and "tomorrow" simply don't exist. As such, there is no surprise that you "only" are consciously aware of "today": the other timeslices don't exist. The only ontological reality is 3-dimensional. A 4-dim spacetime construction in Newtonian physics is just a mathematical extension with no corresponding ontology, and hence the "t-parameter" parametrising the different t-slices doesn't represent anything physical (just a parameter that parametrises illusionary extensions of the 3-dimensional ontology in 4 dimensions). And of course, a specific value of that t-parameter corresponds to the existing timeslice, and that is what we call the time "now".

    But this is - as far as I understand - not possible in GR: the 4-dim manifold has to have ontological existence. And then it is strange that of all my 4-dimensional existance, I only experience one 3-dim slice.

    One remark: I don't, of course, experience a "past light cone". I only experience a small 3-dim volume corresponding to about the size of my brain, and it is in this 3-dim volume that the sensory information is coded from events that happened in my past light cone, which make me conclude that other things happened. I'm only aware of the state of my brain, not of a signal I am receiving. When I talk about a time slice, I'm only talking about a time slice some 20 cm across. I can only be indirectly aware of things in my past lightcone, because these things changed the record of my brain. But my direct subjective experience is only aware of the state of matters in the volume of my brain (or maybe even a smaller part of it).
     
  16. Nov 22, 2005 #15
    **
    I'm just saying that you're only experiencing A CERTAIN POINT ON YOUR WORLD LINE, which is a special point, called NOW. **


    This is postulate (c) + I exist in my framework for *one* person. Your objection was immediatly : but what about the nows for all other persons? Why shoud these *nows* form a differentiable spacelike hypersurface, so that when A sees B, B is spacelike related to A and not in the future of it? Which dynamical agreement in GR can make sure that this is the case ? At that moment you inferred that eigentime from the BB might not do it because of the existence of gigantic focal points. Since you know that there is no GENERIC way to dynamically assign a *now* which has the above mentioned features, you conclude that one has to add a parallel mental world.

    The scheme I elaborated upon is all you can do generically (there is one robot which observes). Now, our universe is a very SPECIAL one, it is almost static and spatially flat (very close to Friedmann) and all deviations galaxies bring along are by no means sufficient to deform these constant t surfaces such that they are not achronal anymore. On the large scale, our universe is expanding which prevents it from consisting in the forseeable future of gigantic (supermassive) focal points which are exactly capable of folding space such that is not achronal anymore. Gigantic black holes are of no importance here since the metric gets only troublesome behind the event horizon and we cannot observe this part of the universe anyway. Similarly, the world is probably full of tiny black holes, or spinning ``singularities´´ but these are so small that they do not change the latter conclusion FAPP. So, our initial conditions are so special that eigentime starting from the BB *is* providing the *now* WE experience (and not just I). I already hinted the analogy somewhere with the second law of thermodynamics which needs the same special initial conditions to hold.


    **This is different in Newtonian physics: you can postulate that "yesterday" and "tomorrow" simply don't exist. As such, there is no surprise that you "only" are consciously aware of "today": the other timeslices don't exist. **

    As mentioned the same can be done for *one* person generically, and for the WHOLE universe simultaneously in very special circumstances such as small deviations from Friedmann.


    ** I only experience one 3-dim slice. **

    That remains incorrect.


    ** One remark: I don't, of course, experience a "past light cone". I only experience a small 3-dim volume corresponding to about the size of my brain, and it is in this 3-dim volume that the sensory information is coded from events that happened in my past light cone, which make me conclude that other things happened. **

    What we call *now* is a tiny sufficiently tickend *lamphat* such that it is closed at the top (I only know my past, not anything spacelike to me).


    ** I'm only aware of the state of my brain, not of a signal I am receiving. **

    That is your preferred consciousness lecture (unnecessary in my view for our universe). If our universe were not so good and almost flat (at least in our galaxy), we would not be here because gravitation would destroy us (some kind of anthropic argument).


    ** When I talk about a time slice, I'm only talking about a time slice some 20 cm across. **

    You do not need your whole brain to store some data, no ???

    ** But my direct subjective experience is only aware of the state of matters in the volume of my brain (or maybe even a smaller part of it **

    Your brain is not ``aware´´ instantaneously.
     
  17. Nov 22, 2005 #16

    vanesch

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    I think we're running in circles. I will ask you: does the event "me celebrating my birthday 3 years ago" have an ontological meaning or not in GR ? I mean, is there something that exists, out there, that corresponds to "me celebrating my birthday 3 years ago" or doesn't it exist ?

    Does "you have your 4th kid" (assuming one day you'll have 4 kids) exist in the GR ontology or not ?
     
  18. Nov 22, 2005 #17
    No, we are not running in circles. You just want to assume that GR is nothing BUT the Einstein equations and then all your objections are of course justified. I say that if you want a meaningful interpretation of GR, you just have to add a localized Newton hypothesis for every small tube around a worldline. This, is what I call (c) and it clearly determines a NOW for me. Now, an extra problem is that the whole universe seems to observe the same *now* (that is why you love newton so much). In my previous message, I said this can be solved by using the very specific initial conditions of the universe. Dynamically, you can do this as follows: just take Einstein Hilbert and put in by means of Lagrangian multipliers the harmonic condition for four scalar fields (that is the Gaussian gauge). Now, when suitable initial conditions are used, this gauge does not break down due to focal points. This is precisely what happens for the Friedmann universes and the slight perturbations of it in which we live. It goes without saying that the gaussian gauge condition DOES break down in quantum gravity; Karel Kuchar has done quite some work on that (1991). Once we have this *global* dynamical gauge you can have the same interpretational scheme as Newton has (and you do not need consciousness for that, you simply state that all material objects are in one and the same slice).

    In quantum gravity this is all much harder: as I said before, quantization in the gaussian gauge suffers from considerable difficulties (just due to these wild initial conditions which cause its breakdown). In causal dynamical triangulations for example, a kind of harmonic gauge condition is build in kinematically (as is a beginning of time through the Hartle Hawking boundary conditions). In causal sets, one goes over to a universal counting time (arrow is given by partial order) and in LQG, one just starts from an arbitrary foliation. In classical relativity, you have many globally defined dynamical time functions (the harmonic just being one - albeit the most natural); one could also take the volume of the past lightcone as the dynamical measure of time (again t=0 being fixed by the big bang). The latter is particularly robust concerning focal points.

    So, yes, you *can* get a global dynamically determined *now* in GR. You simply have to add your favourite time function to the action by means of a Lagrangian multiplier. This is ALSO what we do in Minkowski for example: Minkowski is dynamically singled out by (i) Ricci = 0, (ii) constraint : Weyl = 0 (iii) Harmonic constraint wrt. a flat spacelike hypersurface.
     
  19. Nov 22, 2005 #18

    vanesch

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    Please reply also to my previous post.

    Here, I would simply like to make a few extra comments.

    Yes, right. Well, at least, that there has to be a specific relation between the physical ontology and the subjective observation, which makes you experience "now".

    You seem to be postulating here something I wasn't aware off. If I understand you well, you seem to say that there are 2 things: the 4-dim manifold, and then still a kind of UNIVERSAL parameter, which indicates WHICH eigentime since the big bang is "special" so that it exists "now". (this was the role of time in the Newtonian frame). So if "eigentime since the big bang equals the "special time" it ontologically exists, and if it corresponds to a brain, then that is what is experienced by the consciousness associated with that brain, is that it ?

    But it is difficult to establish an eigentime since the big bang for something like a brain, that is made up of different particles with different histories. Don't you think that, over 15 billion years, differences in eigentime of a few 10s of years can be accumulated ? Now, this brings me to the example I gave: this means that if my neighbour's brain is made up of particles that "got 10 years late" since the big bang, I'm actually just dealing with him as a zombie, because he's consciously experiencing 10 years ago, when I'm experiencing "now" and the body I see "now" of him is not conscious.
    (and when it will become conscious, namely when the parameter which indicates which point should be experienced consciously has shifted 10 years, I won't be experiencing consciously my body at the party anymore, but 10 years later ; while at that point, my neighbour experiences the party).

    And in any case, we are having some difficulties, because for this external parameter (which indicates which is the value of eigentime that is "now") to coincide with an ontological reality, you'd have to assign "reality status" to only certain events - which indeed, might not even make up a smooth surface and the entire 4-dim manifold looses its "reality status" in GR.

    I wasn't aware one could deny ontology to the 4-dim manifold in GR, to only keep those points which were on eigentimes of a certain value since the big bang. And as I tried to argue, I'm sure that even small deviations introduce differences of a few years after 15 billion years, which would mean that most of the matter around me wouldn't even have an ontological existence "now", because their ontological existence (as determined by the external clock, as in Newton) would be slightly late or early.

    There's a specific POINT in your brain that you are aware of ?

    This has nothing to do with relativity, it is even recognized in the materialist view. Cut all the nerves leading to your brain and you'll know that what you're only aware of, is your brain status. Seeing, hearing and so on are illusions of receiving signals. It is only because they change the brain status that you experience them.

    Well, it is aware "instantaneously" of its status, no ? You mean, it is not instantaneously aware of external stimuli before they are processed. But I don't care about that, I'm talking about whatever it is that determines my conscious subjective experience. Some part of the brain is responsible for it, and the status of that part - which DETERMINES my conscious experience - well, determines my conscious experience, no ? So if that is in a certain state, then that IS my conscious experience (instantaneously) no ? But I didn't want to go into detailled neurological considerations. I just take the "thing which determines my subjective experience" as "my brain" ; it might be only part of it.
     
  20. Nov 22, 2005 #19

    vanesch

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    Ah, I was not aware of this possibility and you are honestly technically hitting me with stuff I don't know about.
    So the 4-dim manifold has no ontological status in GR ? This is really new to me.
    But, eh, doesn't that mean that general covariance goes down the drain ?
    Can you kindly explain me a bit more the technical stuff you're adressing here, I'd like to know more about it.
     
  21. Nov 22, 2005 #20
    ** Please reply also to my previous post. **

    I think I did already.

    ** Here, I would simply like to make a few extra comments.
    Yes, right. Well, at least, that there has to be a specific relation between the physical ontology and the subjective observation, which makes you experience "now". **

    drop the word subjective (it has a dirty consciousness smell :smile: ) and I agree.

    ** You seem to be postulating here something I wasn't aware off. If I understand you well, you seem to say that there are 2 things: the 4-dim manifold, and then still a kind of UNIVERSAL parameter, which indicates WHICH eigentime since the big bang is "special" so that it exists "now". (this was the role of time in the Newtonian frame). So if "eigentime since the big bang equals the "special time" it ontologically exists, and if it corresponds to a brain, then that is what is experienced by the consciousness associated with that brain, is that it ? **

    Correct, except the last two lines. Eigentime corresponds to a brain ???
    It is simply as follows: we observe we exist (again: you were not going to doubt that). There is an objective roadmap given by GR (the spacetime) and a universal (dynamical) time function which labels a present. By observation, we can know where we are on the roadmap just like you can get out of the desert by observing your relative position to the stars.

    ** But it is difficult to establish an eigentime since the big bang for something like a brain, that is made up of different particles with different histories. **

    Again, our brain does not ``intrinsically´´ establish this eigentime (our brain exists and registers only some time after I was conceived). My brain just observes, therefore it is by definition existing, therefore it corresponds to some time after the big bang in a notion of space where all observing creatures live (by hypothesis). The exact time label is only of academic interest. You seem to be looking for the hand of God ...

    ** Don't you think that, over 15 billion years, differences in eigentime of a few 10s of years can be accumulated ? **

    That is not what we observe and in the Friedmann universe, this is actually exact. Our universe is very, very special ... (generically whe should be killed by gigantic black holes and/or naked singularities)

    ** Now, this brings me to the example I gave: this means that if my neighbour's brain is made up of particles that "got 10 years late" since the big bang, I'm actually just dealing with him as a zombie, because he's consciously experiencing 10 years ago, when I'm experiencing "now" and the body I see "now" of him is not conscious.**

    Ok, I understand that, but our universe does not work that way and GR allows for spacetimes with only contact between the living (even in Gaussian gauge).

    ** I wasn't aware one could deny ontology to the 4-dim manifold in GR, to only keep those points which were on eigentimes of a certain value since the big bang. And as I tried to argue, I'm sure that even small deviations introduce differences of a few years after 15 billion years, which would mean that most of the matter around me wouldn't even have an ontological existence "now", because their ontological existence (as determined by the external clock, as in Newton) would be slightly late or early. **

    But the whole business of cosmology turns around the choice of a universal time parameter and perturbation theory around static spacetimes.

    **There's a specific POINT in your brain that you are aware of ?**

    Not a point of course (but something much, much smaller than 20 cm). Awareness is just a click in some control centre when some data is stored there and there in your brain. It seems to me that you are willing to go into this clicking business ad infinitum - which click is ``consciousness´´ and what clicks are perception ? I just define a materialistic control unit and every click there is BY definitìon ``conscious´´. It could be that there are sub-control units and so on... You postulate that this is not realistic and need a ghost state. So what?? I have just given you a full scheme which can do it without and still does what you want it to do.
     
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