Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Theory Of Everything/ M-Theory

  1. Jun 6, 2006 #1
    my Qns is how everything is The "Theory Of Everything/ M-Theory" ?

    can it calculate temperature rise of an object given sufficient information?

    can it calculate acceleration of an object given sufficient information?

    can it calculate work done given sufficient information?

    Q1) if it unable to do so, why is it called the theory of everything/ mother of all theory??

    Q2) then what is it able to calculate?

    p.s. i know i ask a seemingly stupid Qns. :P
  2. jcsd
  3. Jun 6, 2006 #2


    User Avatar

    In principle or in practice?

    In practice it's likely that we wont even be able to properly define the concepts you listed in a ToE at first. Even if able to do so, the equations they obeye will certainly be to complex to solve. Whatever of them we can solve will be identical to the parts solvable in the context of SM/GR, except for very exotic situations.

    So for all practical purposes a ToE will tell us nothing new.
  4. Jun 6, 2006 #3
    It might have some philosophical value. It would tell us why we are here, what purpose we have. For example, if a TOE told us that information is conserved, then obviously we complex beings exist to balance out the entropy in the universe. Or perhaps we can expect ever increasing complexity or stability.
  5. Jun 6, 2006 #4


    User Avatar

    "It would tell us why we are here, what purpose we have."

    Hardly, our complexity is the result of processes of emergence happening almost exclusively in the SM/GR context. The increase of entropy around us is also just relative to our level of emergence, microscopically no information is ever lost according to what we know.

    Another way to say it is that for almost all purposes we already have a ToE.
  6. Jun 6, 2006 #5


    User Avatar
    Science Advisor

    TOE/M-theory is supposed to explain fundamental physics questions, such as the four forces and the elementary particles. Starting from the four forces and elementary particles, current physics describes atoms, radiation, etc. The next level up, starting from atomic phiscis, chemistry can describe molecules, etc. You get the picture?

    Most day to day science has a pretty good theoretical foundation, including the fact that certain things are essentially impossible to predict, like weather, because very small initial changes can lead to large changes in effects.
  7. Jun 6, 2006 #6
    I suspect that these "processes of emergence" are accounted for by the underlying quantum foam where as you say no information is lost. In this case it will require a complete understanding of the quantum foam, including how quantum gravity is incorporated into it, in order to realize how the classical scale knows when "emergence" is required to balance all things out. :wink:
  8. Jun 7, 2006 #7


    User Avatar
    Science Advisor
    Gold Member

    My objection to that conjecture is it presumes the existence of information. If information bootstaps itself into existence, there is no paradox. Causality may suffer a bit, but at the Planck limit, causality is not required. Time is not a conserved quantity.
  9. Jun 7, 2006 #8


    User Avatar

    Mike2, the process of emergence happens if you just take classical mechanics, or Quantum mechanics at the nuclear scale, or whatever your favourite theory is.
    It's not an unexplained property of a very specific physical system, it's a very ill understood but apparently extremely general property of a wide class of mathematical models. What you say about complexity being related to a conservation of information might be true in some sense, but I just don't see how it should possibly be related to a ToE. You DON'T need a quantum foam to get life/the solar system/everything we have observed so far (except for the universe as a whole).

    Put in another way, given the intial conditions at the time of the formation of our solar system, and a universe operating strictly according to SM/GR, I am convinced that life would just as well develop.
  10. Jun 7, 2006 #9


    User Avatar
    Staff Emeritus
    Gold Member
    Dearly Missed

    Apparently you are not sensitive to the fact that in the SM/GR model so many parameters, including the basic constants of nature, have to be put in by hand.
  11. Jun 7, 2006 #10


    User Avatar

    sA, even if it is true, as you seem to suggest, that these parameters have to be the way they are for complexity to be possible (which is not in contradiction to what I said I think), this would distinguish them within the context of GR/SM, therefore it is a property insensitive to the underlying ToE.

    It would be great if a ToE could explain the 26 parameters, but it seems to me that indeed the complexity we see at our (and higher) energy scales does only depend on the ToE through this precise 26 parameters.

    Or am I missing your (both of your) point(s)?
  12. Jun 7, 2006 #11
    To acknowledge the existence of a particle is to distinguish some form of structure different from the background. This structure (even at this most fundamental level) represents a decrease in entropy. But there must also be a background of "noise" in order to distinguish the structure from the noise. So it would seem that structure cannot form unless the background noise exists, and I suppose the reverse is true as well. This kind of makes me suspect that there must be a balance between the two in nature, a conservation of information - for every from of order there is chaos, and visa versa. No this is not an episode of Get Smart.

    When the universe was so small it was basically one particle, the probability of its existence is 100%; there can be no alternative but that a universe exists. And then the next thing that must have occured is that structures inside the universe must have emerged, like an embryo whose cell begin to divide. But there is no way to divide unity except into various fractional parts, parts whose probability of existence is less certain then the existence of the universe as a whole. Still the universe is very small, and still there is no alternative to its existence as a whole. This implies a conservation of information and that we exist to balance out chaos in the world.
  13. Jun 7, 2006 #12
    ...so the cosmo needs auto-organized systems.
    This leads me to the Smolin's hypotesys about cosmological natural selection.
    Well, this is not antropic, but is always a finalistic principle!
    I have a duble feeling: I'm fashinated even if I rationally reject it...

    About the SM parameters: we can say that Great Unification Theory don't need to explain these, but what people means with ToE must do it... but a theory that can explain these, will need the theoretical context of GUT...

    :biggrin: therefore I'm quite optimist we can search something to avoid these manual parameters :biggrin:
    Last edited: Jun 7, 2006
  14. Jun 8, 2006 #13


    User Avatar
    Science Advisor
    Gold Member

    There are are a myriad of arguments suggesting the values of the fundamental constants can be 'explained'. I don't doubt we can reduce the number of them, but seriously doubt we can make them all go away. I'm convinced that at least a handful of them are simply what they are. Appealing to the anthropic principle is, IMO, an exercise in circular logic. I like the idea behind Smolin's CNS conjecture, but it, like most other other eternal or cyclical universe models, merely ducks the hard questions.
  15. Jun 8, 2006 #14


    User Avatar

    Mike2 I don't get it.
    The way I learned it you need to chose a coarse graining scale to define entropy and structure. Fundamentally in all theories we have, informationn is conserved (the meassurement of QM being a notable exception).

    So on a molecular scale we are no more structured then a rock, on the next scale up we are. I would assume there is a sort of locality of emergence through the scales, that is, the emergence of complex arrangements of molecules depends on the (to ridiculously high precision known) dynamics of molecules and not on the layer below, from which molecules emerge as stable entities.
  16. Jun 9, 2006 #15
    I'm not sure how much certainty can be contained in the quantum foam. On the one hand every virtual particle which changes into others conserves all information in those various changes. On the other hand, the quantum foam is where the uncertainty principle rules. But if the quantum foam does conserve information, then this may be where the necessity of emergence arises.
  17. Jun 9, 2006 #16


    User Avatar


    As I said, emergence occurs at every level without a quantum foam. It occurs in purely classical systems up to the cosmological scale and at energy scales many many orders of magnitude over the planck scale.

    What are you talking about?
  18. Jun 9, 2006 #17
    what am I talking about, you ask....

    All the gravitational and molecular forces are derived from more fundamental physics at the level of the quantum foam. So EVERYTHING, including emergence comes from the quantum foam.

    Just because we do see complexity emerging at various scales does not prove that it does not require an understanding of the most fundamental quantum effects to explain all this. Your point seems to be lost.

    Entropy seems to be caused by initially complex things breaking up an going off in their own separate directions of space. Though properties such as energy and spin are conserved in the break-up, the lack of understanding about the quantum nature of spacetime gives rise to entropy in the first place. If we understood how the quantum properties of spacetime itself were shared with particles as they travelled from one bit of quantum spacetime to the next, we would see that no information would be lost in any size volume of space even as particles dispersed.
    Last edited: Jun 9, 2006
  19. Jun 9, 2006 #18


    User Avatar

    "EVERYTHING, including emergence comes from the quantum foam."

    See, I disagree. The thermodynamics of a system do NOT depend on the details of it's microscopic structure.

    Emergence is in mathematics not in physics.

    "Just because we do see complexity emerging at various scales does not prove that it does not require an understanding of the most fundamental quantum effects to explain all this."

    There is nothing to suggest it does require it. If I put QM of protons, neutrons and electrons into a simulation I get the right answers for the emergent atomic structures. If I put these into a simulation I get the right emergent molecules and so on. This means that emergence is inherent to this limited effective theories, not an exterior effect imposed on them from the more fundamental theory they approximate (and how else could it be? If this was not the case we wouldn't be speaking of these theories and their awesome explanatory power in the first place).

    "the lack of understanding about the quantum nature of spacetime gives rise to entropy in the first place"

    As far as I can see this statement is at best wrong at worse nonsensical.

    I think you are looking in the wrong place, we wont understand emergence by breaking things apart further and looking at ever smaller scales. Emergence is not a problem for the reductionist (at least in the traditional sense).

    Now I wont discount that emergence will in some way have a role to play (see the role statistical mechanics played in the birth of quantum mechanics), but if at all (highly unlikely IMO but not inconceivable) this will come after we gain deep insights into emergence in the context of the effective theories we know and deduce from this that for emergence to work a particular theory needs to give rise to the effectivness.
    For this our understanding of emergence is far to rudimentary to contribute at the moment.
  20. Jun 9, 2006 #19
    Explanations by nature require breaking things down to their elements. Your arguments prove my point. For you describe how larger structures are achieved because of forces and and particles of a smaller scale.

    It may be that understanding the quantum foam will not allow us to predict 2 hands, five fingers, 2 legs, 1 mouth, etc. But it may tell us that complexity is necessary due to some sort of conservation of information that becomes evident throughout the foam.
  21. Jun 10, 2006 #20
    emergence and decoherence

    Maybe it would be intersting to talk about quantum decoherence...
    There will be a conference:
    "[URL [Broken] International Workshop DICE2006
    Castello di Piombino (Tuscany, Italy) September 11-15, 2006
    Quantum Mechanics between Decoherence and Determinism:
    new aspects from particle physics to cosmology[/CENTER][/URL]
    Note the speakers:

    S. Carlip (Univ. of California, Davis)
    Black hole entropy and the problem of universality.

    J. Halliwell (Imperial College, London)
    Commuting position and momentum operators, exact decoherence and emergent classicality.

    G. 't Hooft (Spinoza Institute & Univ. Utrecht)

    B.-L. Hu (Univ. of Maryland)
    What is quantum gravity if spacetime was emergent?

    F. Markopoulou (Perimeterinstitute, Waterloo)

    T. Padmanabhan (IUCAA at Pune)

    J. Pullin (Louisiana State Univ., Baton Rouge)
    Spatio-temporal fundamental decoherence from quantum gravity.

    M. Schlosshauer (Univ. of Queensland)
    Decoherence in quantum electromechanical systems.

    D. Oriti (Univ. of Cambridge)
    A field theory picture for simplicial quantum geometry and the emergence of spacetime.

    and many others.

    There will be a public lecture by Del Giudice... He was the main collaborator of another great italian physicist, Giuliano Preparata. Do you know him? I suggest this book: Giuliano Preparata QED Coherence in Matter World Scientific, 1995
    http://www.citebase.org/cgi-bin/citations?id=oai:arXiv.org:hep-th/9503102" [Broken] He died in 2000.
    I wonder if his works could give inspiration to link SM and QG...
    Last edited by a moderator: May 2, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook