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Postulations and unknown unknowns in physics

  1. Dec 31, 2015 #1
    My understanding is that scientific proof, if we mean physics not pure mathematics, is all about "postulations" to explain experiment, observation, and data.

    But these set of consistent postulations that give us elegant charming equations have their limits of applications and run into anomalies in the underlying theory.


    On the issue of anomalies in a given theory consider the Newtonian mechanics and law of gravity. What happens to $$F=ma$$ or $$F=\frac {GmM}{r^2}$$ if you take the limit when the object is massless, i.e. light, and $$m, M = 0$$?

    The result of calculations is nonsense, a singularity, division by zero. Here comes a new theory by Einstein, totally disregarding the notion of a "force", and gives you some geometrical sense. Light particles, or photons, can have gravity among themselves, called technically "pure radiation", "null dust", or "Vaidya metric" solution.

    Even Einstein version of gravity is immature, because for the interior of black holes, beyond the event horizon, and the Big Bang moment runs into singularity itself. Not to mention that cosmology theory only explains almost 5% of mass energy density of cosmos and the unfit data to current theory is regarded simply as dark energy and dark matter, reflecting our total ignorance, completely "dark" territory of rather known unknowns! Perhaps the key or solution is an unknown unknown.

    In the quantum formalism you also get nonsense results if you insist on a particles system and interpretation. When you disregard this "postulate" and introduce the ontological idea of "matter fields" throughout spacetime you can simply avoid nonsense as physicists do in quantum field theory. Yet again your postulate and new theory breaks down when faced with infinitely large energies or small distances, i.e. "ultraviolet divergence". Making you wonder what is really infinity! Perhaps the solution is in rethinking set and number theory!

    I am not familiar with string theory but would guess that it also counts on alternative postulates.

    A renowned postulate is "the principle of least action" used in classical and quantum and relativity theories based on Lagrangian formalism.


    The question is if the above understanding is correct and if new alternative postulates can only deal with known unknowns or is it a good scientific method also for unknown unknowns?

    The question is should we add a new physical notion that should be observed to avoid singularities of current theory?


    How about multiverse interpretation of QM. We cannot in principle observe a parallel universe. It will remain unknown. Can we therefore say those theories are "unscientific".
     
    Last edited: Dec 31, 2015
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  3. Dec 31, 2015 #2

    MathematicalPhysicist

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    If you cannot observe the other universes how would you know that they exist?
    Perhaps an indirect evidence, but then again you can as well find other explanations to this explanation of multiverse within our own universe.

    Too philosophical for my taste.
     
  4. Jan 2, 2016 #3
    As per my taste much of current work in science is unscientific, in sense that predictions cannot be experimentally verified now or in foreseeable future.
    String theories are coming to mind.

    It is worth to remember that scientific theories are *models* which are describing reality within a scope of their applicability.

    So for example GR is breaking down around very dense objects like BH, laws of thermodynamics are not applicable to systems of few particles only (famous 2 law relies on statistical mechanics which need large numbers of particles to deliver expected results) and so much cherished and successful QFT turns into an utter nonsense once applied to estimations of intristic energy of vacuum, so called zero point energy, by delivering results 110(!!!) orders of magnitude off mark.
    So let's not confuse our models, eg scientific theories with physical reality, eg with Nature.
    These are not the same.
     
  5. Jan 3, 2016 #4

    MathematicalPhysicist

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    From reading the discussions it doesn't seem string theory as of yet have any predictions, it's only a mathematical framework, @Martin0001
     
  6. Jan 3, 2016 #5
    Why not?
    At first glance string theory predicts that:
    1. There are strings (tough luck - too small to test).
    2. There is 10, 11 or even more dimensions (well... we are aware of 4 and no hint of more in LHC)
    3. There is a really large number of possible quantum vacuums (but we are only aware of one, no ideas how to find other).
    4. Principle of equivalence is broken (no evidence yet but we may look still)

    Proper test is 1.
    Second best hint you could get is from 2.
    3 is out of reach to test.
    4. Would hint that theory might be right but not necessary is.

    So at present it is quite messy state of affairs.
     
  7. Jan 4, 2016 #6

    MathematicalPhysicist

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    @Martin0001 we had a discussion here with @haushofer that said that string theory doesn't actually predict the number of dimensions a few months ago.
    He said that in dimension 3+1 we have an anomaly (I don't remember what was the anomaly) in the theory.

    The assertion that there are strings is more a mathematical statement than a physical one since also saying that particles are zero dimensional point like particles is not really a physical statment (but people were using this strucutre mathematically).
     
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