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Theory of everything ? A joke !

  1. Nov 29, 2007 #1
    It has become fashionable to talk about a "Theory of everything (TOE)". Are scientists really serious that their model describes really everything in the universe? If so, they must be either extremely pretentious or extremely stupid or probably both. At one time, the "Earth, Water, Air, Fire" theory was also a TOE, and I am sure that the theories of now will in a far future be considered as primitive as this one. So, I want to plea to stop using this terminology. It gives also a completely wrong impression to the "man in the street". We can never obtain the final truth. The only thing we can do is to reach or describe just a level deeper. Then we need again a lot of time and effort to move down again a level deeper, and so on.

    Rudi Van Nieuwenhove
     
  2. jcsd
  3. Nov 29, 2007 #2

    ZapperZ

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    No, it isn't "fashionable" to talk about a TOE. In fact, I've highlighted written pieces by Phil Anderson and Bob Laughlin that pointed out the fallacy of such a thing. Laughlin even covered this considerably in his book. It only appears to be "fashionable" because the small group of people are getting more publicity due to the "sexiness" of the subject matter.

    You might want to read Laughlin's PNAS paper arguing against TOE as being nothing more than a TOE for "reductionism", but not for physics.

    Zz.
     
  4. Nov 29, 2007 #3
    But then there is reductionism--based on the undeniable trend of the universe to base complicated things on simpler things. So it seems there is probably a very very simple axiom that explains everything.
     
  5. Nov 29, 2007 #4

    ZapperZ

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    But that's purely an assumption not based on facts.

    Laughlin has shown, in his Nobel acceptance speech no less, on how one cannot derive phenomena such as superconductivity simply by invoking all the necessary interactions at the most fundamental level. Try it. No one has managed to do it.

    It is a fact that none of the emergent phenomena that we currently have in physics today have been derived and described via such reductionist approach. I'm not talking about negligible here. I'm talking about absolute ZERO.

    So the assumption that simple axioms can explain everything is something that has no support.

    Zz.
     
  6. Nov 29, 2007 #5
    Well, we are both using inductive reasoning here, so neither of our statements is 100% provable. All we can do is inductively estimate the probability of truth in our statements. The fact that no-one has yet elegantly explained such a new discovery as superconductivity is not surprising, considering that new discoveries usually take time to explain. But there aren't a lot of old discoveries we've explained outside of reductionism. In fact, I can't think of any. So our experience is that reductionism is very probably a general personality trait of the universe.

    For the benefit of other readers, Zz, others, and I are currently having a heated but fun argument about this here: https://www.physicsforums.com/showthread.php?t=199661
     
    Last edited: Nov 29, 2007
  7. Nov 29, 2007 #6

    ZapperZ

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    Er.. superconductivity is a "new discovery"?

    We DO have an explanation of conventional superconductivity. It's called the BCS Theory. But it isn't a reductionist theory. It starts with a many-body ground state, not from single-particle interactions being added on with more and more complexity.

    I strongly suggest you read Laughlin's papers and other materials, because I don't think you are aware of what emergent phenomena are and how they are being described. The whole field of condensed matter physics is based on this, and this is the field of study responsible for your modern electronics that you are using right now.

    Zz.

    Ref:

    1. http://www.pnas.org/cgi/reprint/97/1/28.pdf
    2. http://www.pnas.org/cgi/reprint/97/1/32.pdf
    3. http://arXiv.org/abs/hep-th/0210162
    4. R.B. Laughlin, Rev. Mod. Phys., v.71, p.863 (1999).
     
  8. Nov 29, 2007 #7
    So are you saying, Zz, that there are some phenomena that definitely ARE unexplainable in terms of something more basic? Is the universe inherently unexplainable? Or are humans inherently not capable of understanding the universe? That doesn't sound very scientific.
     
  9. Nov 29, 2007 #8

    ZapperZ

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    Note that saying something cannot be explained using elementary interactions at the individual particle level is NOT the same as saying that there are NO explanations.

    There are many emergent phenomena in condensed matter that have a solid, well-verified theoretical description. This includes conventional superconductivity, fractional quantum hall effect, quantum magnetism, band structure of solids, etc... etc. Heck, even simple theory of electricity in a conductor are explained and derived via such many-body renormalization. It is just that none of these ever started via a First Principle derivation using interactions at the individual particle level. I mean, how can one solve a gazillion interacting particles? We don't even have the most general solution to the 3-body problem, much less, something of the order of Avogadro's number! Yet, we still managed to have a solid theoretical description of many of these emergent phenomena involving such huge number of particles. How did we do this? By ignoring whatever is happening at those individual particles scale and starting with the formulation a many-body state for that system. That is how we solved those system.

    No one has managed to actually see any signature of those emergent behavior by starting with those individual particle interactions. That is why I said that the assumption that once we know all the basic force, we will know everything, is a fallacy. We know that the particles involved in superconductivity need only be described by electromagnetic interactions at the individual particle level. Yet, even with such knowledge, and even including quantum mechanical aspect of the spin orientation, no one has derived superconductivity from this. The BCS theory certainly didn't start from there.

    Zz.
     
  10. Nov 29, 2007 #9
    when one looks at the algorithmic complexity of causal structures like the universe- one sees that complex relationships and states emerge non-deterministically- simple recursive processes form hierarchies of fractal structure- states with unpredictable complexity but yet with very isotropic and consistent patterns of interactions- read: physical laws- so physical laws can be statistically modeled from the bulk of observation- but I don't think there can be a general universal rule like a TOE that can both describe the algorithm in simplest terms AND describe/predict the emergent behavior that leads to physical laws- there can only be a mathematical description of the algorithm and then loose statistical modeling with taxonomic classification of the emergent phenomenology-

    the only honest TOE [as printed on a t-shirt] should display the lambda calculus formulation for the simplest Turing Machine with an asterisk: *sort through bulk states to find this universe
     
    Last edited: Nov 29, 2007
  11. Nov 29, 2007 #10
    I appreciate all of what you are trying to say. But when you say things like...
    It makes it sounds as if you are saying that it has actually been proven that these emergent properties cannot be derived from basic individaul particle/field interactions. I don't know that this kind of no-go theorm has ever been proved.

    Your quote of not even having an exact solution to the 3-body probelm is well taken. But I think everyone agrees that even there the same basic types of interactions apply. If you are saying as a practical matter we can't derive emergent properties from basic interactions, OK, I agree at present. But doesn't mean that it is not possible. Has anyone ever proved that the 3-body problem is not solvable in theory? I think the Helium atom has been solved by going over to "eliptical" coordinates, right?
     
  12. Nov 29, 2007 #11

    ZapperZ

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    I said that we don't have the most general solution to the 3-body problem, i.e. without any constraints. The He atom is actually simpler and with constraints.

    Thus, if the 3-body problem is not tractable, how are we to know to what what kind of "solutions" we can get out of 10^26 particles?

    In one of the article that I've referenced, there's a quote from Phil Anderson that said "More Is Different", not "More Is More Complex". Think about it. In fractional quantum hall effect and fractional charges, you are getting the smallest "particle" being LESS than the individual particles making up the conglomerate! This indicates to me that it isn't just simply scaling up the problem to include a lot of stuff.

    When I said that the claim is a fallacy, I am not making a definite statement that it has been proven to be false. I am saying that it hasn't be done, and there's every indication that it can't be done. Granted, there's no evidence to prove that it can't be done. So I can't go out and tell people that in no uncertain terms. However, if you look at what I tried to say in my first post here, it is to counter the notion that it IS possible, and that such an assumption is valid. It isn't, and I think many people are not aware of that, and certainly not aware of these observations from condensed matter physics.

    Zz.
     
  13. Nov 29, 2007 #12
    I'd like to disagree. These emergent properties represent added struction that takes information to describe and so has entropy. Now if it were possible to prove from QFT, for example, that there is a limit to the amount of entropy that can exist per unit volume - the horizon area entropy theory (or whatever it's called), then there would be some reduction of these emergent properties from fundamental reactions. But I haven't proven it yet. That kind of proof may have to wait until we have a valid QG theory. Hasn't Robert Wald proven this black hole horizon entropy in his QFT on curved spacetime book?
     
    Last edited: Nov 29, 2007
  14. Nov 29, 2007 #13

    f-h

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    The three body problem can not be solved analytically, that is, three Newtonian particles interacting via gravity contain behavior that can not be analytically extracted from the equations that give rise to that very behavior. Neither the less, for the Universe consisting of these three particles these equations are a TOE in the sense that physicists use the term. The impossibility of deriving the emergent behavior from the equations does not imply that it is not contained in the equations.
     
  15. Nov 29, 2007 #14

    mheslep

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    From Laughlin's Nobel lecture
     
  16. Nov 30, 2007 #15

    Chronos

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    Science is done from the top down [observation], not bottom up [theory]. We know where the top is, but not the bottom. Some scientists believe there is a 'bottom', but, none are claiming to have glimpsed it. Particle physicists, whom you might expect to be closest to the 'bottom' have more vexing questions than any other group of scientists. Zz's superconductivity example is an excellent example. The process of finding high temperature superconductors is more miss than hit due to an infuriating array of competing variables. The universe does not yet simplify as you descend into the pit.
     
  17. Nov 30, 2007 #16
    Emergent behavior IS contained in the laws of physics, the problem is our inability to solve problems without approximations.

    There are several reasons for this, first in lieu of exact solutions to problems will must resort to approximations and since we cannot specify initial conditions with infinite precison, even with 100 decimal accuracy eventually the error incurred by the numbers after the 100th decimal will begin to have a drastic effect on the approximation, leading it away from the actual solution. This is what is known as sensitivity to inital conditions.

    It is a mathematical problem not a physical problem.
     
  18. Nov 30, 2007 #17
    How can we have claimed to explain something by providing a more complex "explanation" than simply what we measure? For the sake of this argument, lets define "complexity" as the least number of words that can describe the concept. I claim that BCS requires fewer words than the number of words it would take to individually describe all the forms of superconductivity that we attribute to BCS. Its reductionism. Surely Zz you are not claiming BCS requires more words than would a description of all the forms of superconductivity it describes!
     
  19. Nov 30, 2007 #18

    ZapperZ

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    Er.. requiring "less word" is reductionism IN PHYSICS? Since when? It certainly isn't the reductionism that Steven Weinberg is advocating, and it isn't what elementary particle physics is selling.

    You had just redefined reductionism as used in physics. To claim that this is a valid definition, you should write a rebuttal to Laughlin's papers. If your rebuttal is published, then I'll accept your definition.

    I've never seen anything in physics that has, as one of its criteria, a requirement for "fewer words".

    Zz.
     
    Last edited: Nov 30, 2007
  20. Nov 30, 2007 #19

    ZapperZ

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    Er... come again?

    If I am not able to say that these emergent phenomena cannot be reduced to a description of individual particle interactions, then the reductionism claim that they can is also not true. Why you have to invoke entropy into this is beyond me. I cite the non-existence of any First Principle derivation is my evidence that the latter isn't valid.

    Zz.
     
  21. Nov 30, 2007 #20
    It is arguable that, for the past 80 years physicists have been stuck for a general explanatory theory of the universe basically by the narrow constraints of their methodology, which led, in particular, to the general acceptance of the Copenhagen interpretation of quantum mechanics. So that this doctrine of indeterminacy effectively put an end to any progress towards a true and truly universal quantum revolution.

    The consequence being that physicists can still dream that a general theory of quantum gravity, which assumes the action of the fundamental forces or interactions alone, could lead to a theory of everything that explains quantum mechanics. Whereas, especially given a determinate quantum interpretation, reasons can be found to consider that it's the distinctive quantum behaviour called wave, spin and entanglement that just couldn't possibly be explained as effects caused by any of the forces in any case.

    And then if one stands back from the confines of experimental physics and its methodology and considers problems of explainiing the universe of the medium and large scale by assuming the action of the forces alone, the question may be asked: Would not a theory that generally explains the universe need to be one that accounts for everything that can't be explained as effects caused by the forces or the forces alone, and which would need to begin with a hypothesis that would causally explain quantum mechanics?
     
    Last edited: Nov 30, 2007
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