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Chance in physics ?

  1. May 1, 2003 #1
    I have to ask, is there any sensible reason to believe that physical processes, let's say radioactivity, is governed by chance ? Isn't that conclusion unwarranted ? I mean, the fact that radioactiveness is statistically predictable and depending on atomic structure, is a strong indicator that there's an actual cause for these seemingly random decays. And considering the probability that our atomic model is a true representation of physical reality, we can barely make qualified guesses about these kind of processes.

    What do you think, is science in denial ?
  2. jcsd
  3. May 1, 2003 #2


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    There are no ways to build a deterministic model of small-scale behavior in this universe. Period.

    That a variable is 'statistically predictable' does not imply it has some deterministic cause at all.

    - Warren
  4. May 1, 2003 #3


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    Greetings !
    Denial of what ?
    Science is the (or at least it aspires to be) the
    perfect objective recording and translation of the
    observed reality. It has (or at least shouldn't
    have if it's REAL science) no prior assumptions
    (except existence itself maybe).
    Now THAT is denial.

    Live long and prosper.
  5. May 1, 2003 #4
    I agree.

    No, but that and the fact that it varies with atomic structure are strong indicators that it isn't governed by chance. Not knowing the cause of an effect does not imply there's no cause at all.

    Also, believing everything happens for a reason does not necessarily mean believing all is predictable. I recognize uncertainty, but not the copenhagen interpretation. I don't know if that qualifies as deterministic ? [?]

    .. of the fact that there probably is a very reasonable cause for radioactivity, which science has been unable to find.

    ... perhaps
  6. May 1, 2003 #5
    There is a cause of radioactivity. Uranium atoms are, for example, in a low state of entropy, unstable, far from the ground state. So it's only a matter of time before a neutron pops out and generates radiation.
  7. May 1, 2003 #6
    That's circular reasoning. The definition of an unstable atom involves it being radioactive. But even so, that still doesn't explain how and why the neutron pops out at that specific moment.
  8. May 1, 2003 #7


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    The neutron has a non-zero quantum amplitude to exist outside the nucleus. It will appear outside the nucleus with calculable probability during any given time frame.

    Such probabilities are the very firmament of quantum mechanics -- everything is ultimately based upon such amplitudes.

    In our physical knowledge, there is no deeper answer that what I gave in my first sentence of this post. There is, however, rigorous proof that no deterministic model is able to converge to appear probabilistic in the appropriate physical limits. The Aspect experiments and Bell inequalities forbid it. If these proofs to out to be wrong, nearly every bit of our understanding of the world will be shown to be incorrect.

    - Warren
  9. May 1, 2003 #8

    Ivan Seeking

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    There is Bohm's "Implicate Order" and the concept of "Wholeness in Time". This could provide order over an interval, but it presently yields no predictive ability.
  10. May 2, 2003 #9
    Bold claim. Think we'll see it happen in our lifetime.

    Yes, when you postulate miracles, its expected that you can proove impossibility of determinism. Aspect, Bell, still arguable. QM has fever. Do you have any pointer handy regarding that rigorous proof? Maybe I'm full of crap, but I can't imagine how sufficiently complex quantum system creating even single equilibrium of forces implying irrational values of ratios can stay deterministic. Besides, there is no closed system in this universe. period.

    Also, "appears" is the keyword. Take a look at simple deterministic system, thats extremely unstable in terms of appearance.
    Imo, this is a good example to visualise that even slightest infinitesimal disturbance from outside would develop into apparently random behaviour. Its not possible to determine state of such system without disturbing it, so for observer, by any means, this system behaves randomly. Yet its completely deterministic.
  11. May 2, 2003 #10


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    That would require tossing quantum mechanics and everything based on it into the dumpster. I don't see that happening.
    The universe itself is a closed system.

    It is deterministic only up to a specific number of decimal places. Quantum mechanics deals with things that are very small.
    Last edited: May 2, 2003
  12. May 2, 2003 #11


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    Greetings !

    Regarding radioactivity, perhaps one
    possibility is some rear combination
    of Zero-Point energy fluctuations that
    triggers the nuclear decay.

    This could explain the predictable
    uncertainty of the phenomenon in terms
    of the HUP instead of going into "trouble"
    with each individual radioactive atom.

    Live long and prosper.
  13. May 2, 2003 #12
    It wasn't cute anyway. But yeah, maybe we should die out first.

    -- The universe itself is a closed system.
    Is that proved already??

    What was that supposed to mean? How about planck scale pendulum, with say 10E200 links, and say 10E55 fps instead of 24?
  14. May 2, 2003 #13
    My understanding is that a system can not spontaneousely decay (transit from one state to another). But it can interact with something which makes this system to decay. Now, what if this "something" is a virtual particle of a kind which strongly interacts with such system, and of energy which matches system's energy? Then interaction is very possible and the system will transit from one state to another.

    That is how I consider "spontaneous" decays of all kinds happen.

    What makes particle(s) - photons, electrons, neutrons, etc to appear out of vacuum is the fact that they all are waves, and waves have pairs of mathematically entangled properties (spread of wave number(momentum) and spread in space,or spread of energy and spread in time, etc). Thus the Hezenberg uncertainty and all quantum mechanics with it.

    But what makes certain wave to appear at some particular space-time location, I don't know. May be, particles are bits of space-time itself? Or space-time have wave structure too? Or both are just two sides of same object? Dunno for sure.
    Last edited by a moderator: May 2, 2003
  15. May 2, 2003 #14


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    I'm really not in the mood to argue with crackpots today. Scientists don't go about believing in something because it's cute, or not cute. Scientists believe in things because they are willed into believing them by experiment.

    Bell showed conclusively that there are no deterministic models (the so-called "hidden variable" theories) that can explain observed quantum behavior. It's a mathematical, i.e. fully rigorous, proof. Just because you don't like it doesn't mean it's false.

    - Warren
  16. May 3, 2003 #15


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    Greetings !
    Did Bell's Theorem also prove there're no
    solutions using additional dimensions
    of time/space ? Did it prove there're no
    solutions using other stuff we've yet never
    considered ? A proof is good for a whole
    complete abstract theory that has all the
    data, we do not have all the data - because
    this abstract theory is about reality.

    Live long and prosper.
  17. May 3, 2003 #16
    I think all physics is determined by the smallest possible thing (i.e. superstring are thought to be it, at the moment). There limitations determine the way our universe works, thus if we change a superstring of sorts, it could be that we can change physics to allow for what we want to do, then we become gods :)

    if you think about that for a minute it makes ense :) something has to determine everything, so what else than the thing everything is made out of... however, you could say its the components of the superstring (i.e. the things holding them together and the string things) that individually determine physics.

    I dont belive its chance in the least, where the universe is concerned everything is very well defined :)
  18. May 3, 2003 #17


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    Which means that you're the "old" type of
    materialist and you either do not see
    or ignore the apparent inability of all that's
    "well defined" to explain its own existence.

    Peace and long life.
  19. May 3, 2003 #18
    Not up to date are we ?

    "They show that despite the supposedly definitive Aspect experiments, in the literature local hidden variable (LHV) theories are definitely not dead both experimentally and theoretically. Its a very impressive collection and lively debate. Thompson in particular has worked hard to uncover pitfalls and show the Aspect data may actually support a LHV theory"

    >>> http://www8.pair.com/mnajtiv/qm/bell.htm

    [zz)] If you weren't, you wouldn't. And if you had anything interesting to say you would say it, instead of coughing up a pathetic line like this. Don't insult your intelligence.

    I thought crackpots were the ones that believe in magic ? [?]
  20. May 3, 2003 #19
    Must have hit a soft-spot. You know that when scientists appeal to authority - you're stupid, we're smart.
    Yeah, Bell's theorem is serious stuff. But, its implications are evaluated in frame of current theories, that are incomplete. Alot of assumptions. That no deterministic models can explain observation is just one of possible conclusions. If science was so chilled about state of things, there wouldn't be tens of alternate theories in works by serious scientists.
  21. May 3, 2003 #20


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    Serious != knowledgable.

    A lot of times, the part I marked in boldface is true. (do not interpret this as an assertion it is true now)

    Anyways, if what I understand about quantum measurement theory is correct, then QM has no problem admitting a completely deterministic underlying theory; the catch is that deterministic theory cannot a theory of simultaneous exact position & momentum.

    The classical presumption is that position and momentum are non-probabilistic ideas; that they are a fundamental, so classicist is forced to interpret quantum states as probability amplitudes.

    However, it is just as valid to take quantum states as the fundamental well-defined object and declare position and momentum as probablistic measurements of a quantum state.

    From the latter point of view, a deterministic universe is consistent with the theory; it is acceptable that detectors are really deterministic, merely shaping the typical statistical distribution of our incomplete knowledge into things that look like the concepts we wish to call position and momentum. If we had perfect knowledge of the underlying universe, the output of these detectors would no longer look like position & momentum.
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