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Pure randomness & the incomprehensible universe

  1. Aug 14, 2005 #1
    is anything in our beautiful univerese 'purely' random?

    David Suzuki states in 'The Sacred Balance' that because we cannot know with certanty the position of a particle we therefore have no hope in understanding the univerese as we do not understand the most elementary levels.

    Anyway, i guess thats kind of 2 different topics. I need help on the first moreso,

    Cheers,
     
  2. jcsd
  3. Aug 14, 2005 #2
    It looks like you are starting a deep philosophical interrogation. Your question is referring to the HUP (Heisenberg uncertainty principle). I don't know the book of Suzuki. What I know is that if you sleep in the same room and in the same bed every night, you will surely also stand up about the same time during the week and do about the same things every morning until you get your breakasft. Your different positions (relatively to the walls of your room) will be about the same but not exactly the same one. So: you have a kind of random behavior in a semi-deterministic frame; you must go to the table to get your coffee... (smile) and I wish you a good day
     
  4. Aug 14, 2005 #3

    mezarashi

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    Does understanding that something cannot be precisely known considered understanding? It's not that we don't understand at all the universe at the "elementary level", but rather we understand that from a microscopic point of view, events happen randomly within the bounds of their probability distribution.
     
  5. Aug 14, 2005 #4
    I understand that we cant precisly know a particle position because of the uncertanty principle. but doesnt that just mean we're 'uncertain' of its position/velocity because we alter them in order to try and measure them, or is it that we dont know because its future is random (to a degree)?

    guess what im trying to say is.. does anything occur/happen/move/disappear with NO factors applied to it?
     
    Last edited: Aug 14, 2005
  6. Aug 15, 2005 #5
    I don't think we can know.

    There isn't a way, even in theory, to distinguish between a truly random event, and one caused by 'forces' beyond the scope of our current understanding / models / ability to predict.

    A totally deterministic universe could still be entirely unpredictable and unknowable at many levels to a being living within it, working with limited perception etc.
     
    Last edited: Aug 16, 2005
  7. Aug 15, 2005 #6
    I would like to say that I believe ignorance of a quantum objects exact position/momentum does not imply that our general, more fundamental understanding of how the universe works is somehow more limited. In fact, it could be said that the problems brought up by HUP helped deepen our understanding.

    Just because I cant tell you exactly where your car is as you do 200mph laps doesnt make me any less of a mechanic when I explain how your engine runs.

    God, I hope that makes sense . . .
     
  8. Aug 18, 2005 #7
    The problem may be that the idea of "random" can only ever be half the story. You always need a (global) process to produce (locally) random events. So randomness usually turns out to be the flip side of something highly determined. For example, if I want to toss a coin randomly, I have to go to great lengths to control the process. The coin must be fair. The toss must be high and fast to ensure no possibility of my controlling the outcome. A flat landing place must be chosen so the coin does not land on edge. Lots of constraints needed to ensure a "random outcome".

    So the idea that anything is "purely" random is to ignore the matching need for a "perfectly constrained randomness producing process".

    This does apply directly to QM. You can produce "pure randomness" at the local level if you can perfectly isolate the system in question. But then you can't ever perfectly isolate a part of the Universe as this level of shielding would require infinite energy.
     
  9. Aug 18, 2005 #8
    Lots of constraints are needed to get an outome which is "fair". eg
    a 50:50 coin toss. That does not mean that in the absence of those
    constraints you get determinism; many times you get "random randomness",
    where not only can you not predict deterministically what is going to happen, but there is no neat pattern of probabilities either. Many natural systems fall into this category, eg the weather. And the fact that "predictable randomess" such as your coin-toss requires scene-setting does not make it deterministic.


    Just because a system is not shielded from the rest of the
    universe doesn't necessarily mean that the rest of the universe
    is in fact determining it. A case for the non-local hidden variable approach still needs to be made.
     
  10. Aug 18, 2005 #9
    Without the constraints you don't get a process - no coin toss takes place. The determinism here is the ensuring a "randomness" producing process gets going.

    As to the weather, it is chaotic - random over all scales. You still need a process in some sense. Gravity of a planet to trap a layer of gas. Spinning and solar heating and other entropy gradients to drive the gas. Then in this system of constraint, you get turbulent patterns that then erupt randomly over all scales.

    Note of course that this system has very limited 3D freedom - cyclones can't whirl off into deep space, they remain bound to a more or less 2D plane. So the random randomness (sic) still has determined limits and is not completely unbound.

    On QM, I was refering to environmental decoherence (the only sensible approach IMHO). And also quantum zeno effects where the spectrum between constrained and unconstrained behaviour can be experimentally observed. The nonlocal aspect of QM would be evidence that nothing in the Universe can actually be fully isolated.

    So the important general point is that the Universe has a history - a prevailing state - and this constrains - but does not determine - what can happen next. You thus have a balance between chance and determinism. The material substance of the Universe has an inherent (quantum) creativity.

    But just as importantly, this creativity is severely constrained and gets washed out in most circumstances in the orders of magnitude between the Planck scale and the atomic scale.
     
  11. Sep 10, 2005 #10
    This is, still, one of those open questions for which no compelling answer can be offered currently. Determinism or indeterminism? The reality is that the old debate is still raging even today...Are the probabilistico-statistical regularities observed in the experiments with quantum particles a sign of determinism or of indeterminism? Here the stances vary widely.

    The orthodox wisdom, following the fathers of the Copenhagen interpretation, say that 'god does play dice' meaning that the quantum world (at least) is truly random at the 'core', being intrinsically indeterministic + we deal with truly uncaused events at the quantum level as the rule.

    Other thinkers however (among them Bohm, De Broglie, Vigier, Popper, Einstein, Bell, Ian Stewart and so on) say that we have to be much more cautious when interpreting QM, the observed probabilistic regularities deserve at least a further special attention (probabilistic approaches are fully compatible with deterministic processes), there is no compelling evidence that our universe cannot be deterministic or that the standard formalism of QM is complete (for example Bell's inequalities violations are fully compatible with classical locality if a certain form of determinism hold at quantum level).

    There are subltle differences amonst these thinkers but essentially all sustain at least a 'weak' form of determinism. The notion of 'weak' determinism has a long tradition at least from Hume onward. Defined in few words: Hume says that all events have causes but things could have been otherwise (e.g after making a choice we can still say that counterfactuals were possible).

    I have always had a very difficult time to accept Hume's definition for I do not see how could we avoid some form of indeterminism or that consciousness (a certain part of it at least) is a fundamental feature of the universe, being outside causation (not all things are caused then). Under the acception that consciousness is not fundamental the only rational solution I see is to accept at least a very weak form of indeterminism (at least some events are not predetermined, this irrespective whether prediction is possible or not).

    Popper seems to confirm me. In his book 'The open universe: An Argument for Indeterminism' Popper advocates a form of 'weak' indeterminism / 'weak' determinism absolutely necessary in his view for the existence of real free will. Frankly speaking I do not find his arguments there very strong (that there are events that are not predetermined) but the point of interest is that he defines his 'weak' form of determinism very clearly, by rejecting the claims of completitude and intrinsic indeterminism defended by copenhagenists.

    For him the quantum world is not intrinsically acausal and random, he does not reject the possibility of some 'deeper', fully deterministic, quantum laws. However predictability (in the classical deterministic sense) at quantum level is not possible and moreover there are events which are not predetermined this leaving the door open to real free will and for human responsability. This is exactly one of the interpretations of the Humean concept of 'weak' determinism I've always had in mind (being in the same time a form of 'weak' indeterminism).

    [some clarifications about Popper's view: his type of 'weak' determinism is a form of indeterminism (also 'weak'), he does not deny the existence of causality or the existence of clear laws at the quantum level he only denies strong determinism. That is, it is conceivable for example that the behaviour of quantum particles in the two slits experiment is fully deterministic in the strong sense (irrespective whether we will ever find AND justify those laws) but there must be some truly acausal events at least in the processes involved in human decision making at the quantum level or even at 'deeper' levels.]

    However neither stronger forms of determinism can be ruled out, the logical exercise of Bohm prevent us at least now to claim that there must be acausal events or that quantum entities cannot be particles (close to the situation in the classical physics) having definite trajectories, positions and momenta (irrespective whether we can know them or not).

    So, under the current circumstances at least, it is fairer to say that we do not know whether the universe is deterministic or not, implicitly we do not know whether the quantum world is truly random as copenhagenists and related views hold (still genuine underdetermination at quantum level, there are no sufficient reasons yet, upon the actual standard of rationality, to make a compelling difference between the different interpretations of QM).
     
    Last edited: Sep 11, 2005
  12. Sep 15, 2005 #11
    Randomness

    We can never know what is random and what isn't. The fact that at this point in science we cannot see any further into matter because of the uncertainty principal does not prove that the universe is complete (or partial) randomness. It may only show the limits of human knowledge.
     
  13. Sep 15, 2005 #12
    Randomness is what we haven't found a pattern to yet, and everything predictable is what we haven't found the randomness in yet.
     
  14. Sep 17, 2005 #13
    We are mixing apples and oranges.

    If you shuffle a deck of cards, there is no escaping the fact that the resulting shuffled deck will have a specific resulting order.

    You may not have knowledge of what that order is, but it does not mean that the deck is disordered, or to what extent.

    Of course, no shuffling process should produce a highly ordered deck, because then you would always be able to figure out the order somehow, defeating the purpose of shuffling.

    But simply not having knowledge does not create randomness. Just because you have no knowledge of the ordering of the cards, does not make the shuffle a random one.


    The original poster posits a very fascinating question.

    Consider this gedanken experiment :
    We want to create a random pattern of dots in the universe. The dots can appear anywhere in the entire universe, much like a computer program that creates random dots on your screen.
    Did we create pure randomness ? I dont think so - because we have already imposed a rule on this experiment. The rule is that we create dots. This is order. It's a rule. It imposes order on the experiment.

    So - does randomness exist ?
     
  15. Sep 17, 2005 #14
    Again, the mistake is to insist on either/or answers. The world (of processes) can be constrained towards randomness or towards determinism as opposing limits. You can argue for ever and a day about what "is". Much more interesting to consider how things actually come to be.

    So if you want to make a coin toss "random" or alternatively, "determined", what do you have to do?

    To make it random, you have to flick it high and fast enough. Make sure it lands on the right kind of surface. That it is evenly weighted. etc.

    To make it determined, you place it down the way you want it. After ensuring against all random mishaps, like someone bumping your hand on the way.
     
  16. Sep 20, 2005 #15
    What is the difference between saying the "position of a particle is at 1.32 microns plus or minus 0.0010 microns" or saying it is exactly at "1.3245456 microns" ? Is this so important ? and then at what point will the precision be sufficient to say you know exactly where it is ? It will never be precise enough even if you could measure/see it at 10^-10,000,000 microns because then your uncertainty will just be moved into the plus or minus 10^-1,000,000,000,000 microns.
     
  17. Sep 20, 2005 #16

    selfAdjoint

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    Perfectly correct. And for over a century there have been scientist who spent their entire careers "adding another decimal place." Finite experiments will never tell us the exact value with certainty, so it is necessary for those who make measurements to specify what their particular level of uncertainty is, so that others can estimate what size grain of salt to take the measurement with.
     
  18. Sep 21, 2005 #17
    So then pure determinism can really never be achieved. If you consider the extreme case of determinism where we have a complete set of equations that can determine exactly where a particle will be at a given time, we will always say "the particle will be 10.133949395949950409504 microns from another given point plus or minus 10^-1000000000000000000000000 microns". So your random - uncetainty is moved and you will never be able to demonstrate that the particle is at a given place with infinite precision. In fact determinism implies infinite precision, because if it doesn't then we can arbitrarily choose what level of error is no longer important for our determinism. If plus or minus 10,000 km is an acceptable level, than you can say determinism is achieved by saying the previous particle at a given time is on the earth, for example. What level of precision is no longer important to pure determinism ? The planck level (10^-40 mm) ? Isn't that just a limitation of our sense organs ? I can always say determinism is not achieved because there is pure randomness at 10^-100 mm.
     
  19. Sep 21, 2005 #18
    So then determinism is dependent on our personal interactions with the universe. If we can predict with cm precision hurricane katrina then we have achieved the goal of "pure" determinism in as much as it effects us and has meaning for us humans within our context. If you want to predict how far rock number 3,456 will have moved on mars by the year 2013 but can't, then that doesn't mean pure determinism isn't achieved since this is irrelevant for us humans. A funny corollary is that if in the future we live in a complete computer based virtual reality, complete prediction of everything could be achieved, so determinism for us would be completely achieved.
     
    Last edited: Sep 21, 2005
  20. Sep 22, 2005 #19
    I think you pinpointed down a major aspect of mathematics in general. It is an invention in as far as it is used according to our personal needs and uses. If plus or minus 10,000 km of precision is not important, most of our math is irrelevant in as far as it calculates things according to how they relate to us. Randomness is also a very ARBITRARY concept since this is also related on how we use the concept and how we perceive randomness. Quantum randomness is never directly perceived, so it can just as well be irrelevant. Only when you configure experiments and decide to manipulate matter in a certain way does it become relevant. If a million km particle accelerator becomes fundamental then physics that occurs at the 10^-30 mm size becomes very important.

    This thread then ties in with the "matter is mathematics" thread.

    https://www.physicsforums.com/showthread.php?t=85904

    Also we must bear in mind that mathematics is a process, an activity, a sequence of actions we perform in our mind, a series of steps we follow to obtain an answer to a question regarding for example "positions of particles". This in no way can be completely and infinitely deterministic, since the series of steps is always finite.
     
    Last edited: Sep 22, 2005
  21. Sep 22, 2005 #20
    This is not what the uncertainty principle says.
     
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