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    Smolin Vs Susskind: The Judge’s Decision Part 2
    By Sascha Vongehr | November 29th 2010 08:45 PM | 2 comments | Print | E-mail | Track Comments
    About Sascha

    Dr. Sascha Vongehr [风洒沙] studied phil/math/chem/phys in Germany, obtained a BSc in theoretical physics (electro-mag) & MSc (stringtheory)...

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    Physics hunts for the ultimate theory; at least that is what the media and people like L. Susskind and M. Tegmark tell us incessantly what physics is all about (god particle, ultimate string theory landscape, ultimate ensemble, and all that). If you are after the ultimate theory, Smolin

    demands two things that are yet worse than an infinite statistical ensemble (which I went into in Part 1 of this series): Firstly, Darwinian argumentation as a fundamental explanation, and secondly, that the fundamental theory can potentially be falsified.


    Lets first deal with Darwinian selection as the fundament: If you have a dead planet as a given, it is valid to ask where the amazingly complex animals came from, but it is even more important to understand where the first cells came from. Pre-biotic evolution resulted in those first beginnings on the otherwise dead background (e.g. earth). However, Smolin completely disregards the question of where the first black holes are coming from and what the dead background is on which the Darwinian selection process makes sense at that point. He only looks at efficient propagation, but has no environment in which different offspring could compete for resources, for example. They “compete” for sheer number, but that is not a scarce resource if you have infinity to take from.


    One cannot get the ultimate fundament from Darwinian evolution, because such evolution always requires a background on which selection happens. His solution is at most a little step in what may easily become an infinite regress, a tower of Darwinian evolutions, a tower of dead backgrounds, with the black holes being only one tiny step. To Smolin’s credit, he is not so much interested in already having a final theory than he is interested in proper science.


    On to the second aspect: Smolin draws on Karl Popper, who is famous for demanding that good theories must offer ways to decide, best by experimental observation, whether they are “right or wrong”. This is of course expressed with more sophistication via hypotheses and so on. Nevertheless, I rather speak about using observation in order to stake out a theory’s domain of applicability (Einstein did not prove Newton wrong!). This view also helps to understand that if the domain is unbounded, as is obviously the case for a truly ultimate theory, it cannot be falsified. Smolin started the whole Smolin/Susskind debate because he feels that “the anthropic principle cannot yield any falsifiable predictions, and therefore cannot be a part of science”. String theory is not a good theory in this respect, because it is mathematically so rich that one finds always some way to change the theory to account for pretty much whatever you could possibly observe. That is bad in a way, but it is actually exactly what the final theory should do!


    The ultimate theory cannot be supposed to be also coming with stuff that you can potentially falsify. The theory of everything tells us all that is possible. Any partial (i.e. not ultimate) theory may be expected to come with stuff that can be either this or that way, A or B. One, maybe A, fits to the rest of the world, the other one, say B, is wrong, it does not fit the rest. B can be found to be wrong by experimental observation, but the fundamental reason for its being wrong is that it is inconsistent with the rest of the whole. Now back to the ultimate theory of everything: your subject is totality, theories that tell us all that is possibly possible. In that case, the overall consistency is already there in the concept. You should not expect this theory to hand you anything falsifiable. Again, to Smolin’s credit, he is not claiming to be interested in the ultimate physics, but only in the next step, in falsifiable hypotheses concerning quantum gravity.


    Next time, I will start with ripping on Susskind.

    Comments

    colinkeenan
    Up to now I've just been reading posts and replies on science20.com, but since nobody's asking my question, guess it's finally time to contribute.

    I don't understand how Sascha Vongehr reaches the conclusion that a truly ultimate theory cannot be falsified as quoted below:

    "...I rather speak about using observation in order to stake out a theory’s domain of applicability (Einstein did not prove Newton wrong!). This view also helps to understand that if the domain is unbounded, as is obviously the case for a truly ultimate theory, it cannot be falsified."

    I understand the first part about using observation in order to stake out a theory's domain of applicability so that Newton's theory of gravity still works within a more limited domain of applicability than Einstein's theory of gravity. Maybe it's "true" that gravity is a force within the more limited domain, but to the extent the theory is trying to be completely general, it has already been falsified. The more general a theory is supposed to be, the more opportunities there should be to falsify it. So, because it's trying to be completely general, the ultimate theory should be easier to falsify than a theory that puts a bound on it's domain from the start.

    If the "theory" you are working with can be manipulated to be correct no matter what observation shows, then it seems to be a fantastically powerful mathematical machine for generating theories but not itself a theory of physics. I get it that with infinitely many pocket universes allowed in these ultimate theories, each with their own initial conditions where fundamental constants of physics are also part of the initial conditions, ultimate theories like these cannot be falsified by using them to calculate fundamental constants of physics. But when all the details are known to allow full application of the theory to our own pocket universe, the theory must make statements that can be shown to match observation or contradict observation without any further manipulation of the theory being possible. Even the prediction of multiple pocket universes might have testable consequences, but if not, that wouldn't mean their aren't other testable predictions that can be made with the theory. I don't think every implication of the ultimate theory needs to be falsifiable, but some statements that are possible to make must be falsifiable to be a theory of physics at all. Some things are impossible in reality, so their must also be things that are impossible in the ultimate theory of reality.
    vongehr
    "ultimate theory should be easier to falsify than a theory that puts a bound on it's domain from the start."
    Popper/Smolin/... demand hypotheses that can be potentially falsified, so that trying to confirm/falsify as the method of finding the limits of the domain of applicability is still worthwhile. Assume that we found the ultimate theory (no such limits; it tells us all that is "possibly possible"), we just do not realize our luck yet. All we can find out is what kind of bubble we happen to reside in, while looking to have something that can potentially be false with the theory is a waste of time.
    "Some things are impossible in reality, so their must also be things that are impossible in the ultimate theory of reality."
    If the ultimate theory holds "A is impossible", it is impossible in all bubbles (impossible just in this bubble will not falsify the ultimate theory, because it allows A in other bubbles). In other bubbles, since it is the ultimate theory, P is about self-consistency of observation as such, basically almost (or equal?) to pure logic (A = "1+1=3"). How do you test that with physics? Why should we even try?

    A multiverse on grounds of linear quantum mechanics is basically saying that nothing is impossible. How to falsify anything in this case? Even if you find 1+1=3 sometimes, it could always be just quantum fluctuation. There are already observers that talk to ghosts - we regard such (to the observer consistent) observation as hallucination (regardless whether observer is in straight jacket or Pope mobile), and consistency is such always ensured. I am not trying to be funny: it goes to the core of that the "ultimate ensemble theory" allows extremely small probabilities (lowered entropy in a closed system for example, quantum tunneling into Boltzmann brains).