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Are there any accidental things in Physics?

  1. Yes

    8 vote(s)
    66.7%
  2. No

    3 vote(s)
    25.0%
  3. What??

    1 vote(s)
    8.3%
  1. May 29, 2004 #1
    Hi there

    My question is, are there any accidental things in physical ?

    Why am I asking this question?
    Many people think the whole universe is either created or it's made by chance! to me it sounds like probability and chance are just matematical ideas and we don't have anything accidental in the real world nor in any area of physics, or at least we shouldn't.
    I think anything that happens has a cause and something that has a cause can't be accidental.

    For example in math we can calculate if we throw a dice once, the chance that the dice shows 1 is 1/6.
    But in physics if know exactly how much the dice weights and how exactly it is thrown and what forces are effecting it and if we can measure them then we can predict what number will it be showing.

    So generally we use probablity because we are not able to measure some quantities.
    One of the conclusions from Newton's rules is that if someday we know how much does each thing weight and how it is moving and etc.. we can predict everything that will happen in future.

    What do you think? Is there anything accidental that is reviewed in any area of Physics?
     
    Last edited: May 29, 2004
  2. jcsd
  3. May 29, 2004 #2
    Well, first, if you believe in QM then you should accept that at a fundamental level accidents do happen because at that level everything is determined probabilistically.

    But even if we were to live in a fully deterministic world, chaos theory and "complexity" tell us that often we must have perfect knowledge of a system in order to make any predictions about it. So the question of whether or not you could in principle predict everything becomes somewhat academic as you will probably never obtain the knowledge required to make these predictions.

    Matt
     
  4. May 29, 2004 #3
    I don't think so. Because physics is based on math models, and its theory has been created to explain the things as far as mathematics can do. Any physics student realizes that all of the problems we do are supposing things such as: constant gravity, constant pressure, ideal gases, no friction...

    That's the point. Using math models we can learn about universe and explain so many things that happens on it. Certainly there are a lot of things that can be explained but we can't write down a equation to solve it.

    You can understand the meaning of "aceleration" and see a car acelerating without consider friction, the air, and so, and so, and so...

    Chemist can't do that :)
     
  5. May 29, 2004 #4
    Oh, I forgot to say that I answered "No" to the question above.
     
  6. May 30, 2004 #5
    Thanks for your replies :)

    If you believe that the answer is 'yes' and there are accidental things happening on random basis in the physical world I would really appreciate if you give a clear example of a physical accident.
     
  7. May 30, 2004 #6
    Hmm this is difficult as I'm not sure what you define as an 'accident'. By your first post it sounded like you defined one as 'something you could not predict', but now I'm not so sure.

    Perhaps before we continue you could give us your definition?

    Matt
     
  8. May 30, 2004 #7
    Nothing is made by chance

    Anyone who thinks that everything happens or accidents take place by chance is totally wrong. It is foolish to think this. Every thing happens for a reason. There r scientific reasons for every thing which happens. Ok think about some time, if the humans or the universe were created by chance, then how come they have so complicated structure and mechanism.
     
  9. May 30, 2004 #8

    selfAdjoint

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    There are two branches of physics that apply here. Of course quantum theory has its well known uncertainty and probability aspects, and chaos theory has the sensitive dependence on initial conditions ("butterfly effect") where small deviations can expand exponentially into large ones. The bottom line is that physics does not say you can predict the future exactly; it says if you could have perfect knowledge you might do so.

    In practice our gross physical world seems pretty deterministic, but that seeming can't be pushed too far. Every day we are buffeted by winds that can't in principle be forecasted too many days into the future.
     
  10. May 30, 2004 #9

    ahrkron

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    And in QM, the output of two quantum systems set up in exactly the same way will follow the same probability distributions, but the individual outcomes will not be the same. They are "accidental" within the limits set by the distribution function.
     
  11. May 30, 2004 #10

    jcsd

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    I think that staements to strong, can you cannot say that there's DEFINTELY a reason that a wavefunction we collapse into a particular eigenstate as opposed to another eigenstate.
     
  12. May 30, 2004 #11

    Alkatran

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    The problem is that we can't ever know the exact position and speed of a particle at a point in time... so we'll never really know the answer, eh? (Or maybe that's the answer itself...)

    I personnaly believe that, yes, causality applies and everything in the future is pretty well determined by the present. But: We can't even understand the present, so good luck with the future.
     
  13. May 30, 2004 #12
    It seems the majority of responders here take view that QM provides the answer that physics does have accidental components, though I'm not sure philosophically if "accidental" is the same thing as "acausal." I agree that QM means the universe is not strictly deterministic, and that een if we had complete information of initial conditions, the future would not be entirely predictable (more predictable for the very short term in near neighborhoods, and less predictable as time and distance increases).

    I don't like the term "acidental," bcause it's opposite seems to be "intentional," and that opens up aspects of theology that are outside the scope of physics.
     
  14. May 31, 2004 #13
    What I meant by accident is an event that happenes in a disordered way. something that is abseloutly random and there is no possible way to predict it. Anything that happens by chance. An unplanned event, unexpected and undesigned, which occurs suddenly and at a definite place and a lot of other good definitions that you can browse trough http://www.google.com/search?hl=en&lr=&ie=UTF-8&q=define:accident


    I think in some branches of physics because we are not able to measure some quantities accuartily (or we don't believe those quantities are measureable) we use probablity rules to solve the problems, and using these rules DOES NOT mean that there are things that happen in physics on RANDOM basis. Does anyone disagree with that?
     
  15. May 31, 2004 #14
    I believe the very popular idea that the whole universe is either created or happened accidentally is a fallacy entitled "False Dilemma" in logic, and that means these two are not the only two options, more than that I believe not only these two are not the only options but in fact these are two WRONG options to explain the existance of the universe.

    The second option has less to do with science, Im just very curious to know if there are areas in physics in which things happen in an unpredictable way?

    Theists insist to persuade people that atheists believe the universe is created just by chance, we know although the probablity of everything being created by chance is a very very small number but that doesn't make it IMPOSSIBLE at all,but More than that what I'm trying to ask from you guys is that is the first option "being created by chance" a physically approved argument? Do we categorize events as either predictable or accidental in physical sense? I didn't think so...

    We were discussing these terms with some theists and they have claimed that there are areas in physics that accidents happens and we have to use probablity rules, they named "spectroscopy" and "statistical thermodynamics" as two examples and I'm trying to validate my idea that "that we use probablity rules (if really use), that doesn't mean some events happen in physics just accidentally"
     
  16. May 31, 2004 #15
    That's right, maybe acausal is a better word for this question.
     
  17. May 31, 2004 #16
    Who's to say we will ever be able to have quantum systems that are "set up in exactly the same way"? If the two systems are said to be completely equvialent, it implies one actually checked each and every component and verified that all of its properties match on both systems. And if one were to perform this operation on two quantum systems their results would no longer be different.

    Right?
     
  18. May 31, 2004 #17
    Let's not confuse our inability to predict the future and the future being 'accidental'. We also can't predict the weather with great accuracy, does that mean it behaves in a completely random way? No, it just means it is too complicated to be predicted efficiently.

    I don't like to think the future can't be predicted even if we had unlimited computation power and complete information over the inital setup. After all, that's what the universe does all the time - it predicts the future and manifests it. However, it only predicts the 'immediate future', i.e the state of afairs around the universe at the moment that will follow the present. It might not be possible to predict the long term future, without going through every step in between. Which is why I believe we will never be able to predict the far future... (And no, I'm not talking about some divine being here. Think of it like a giant uber computer. :smile:)
     
  19. May 31, 2004 #18
    Well, I read in a book, that the CHANCE of the big bang happening would be the same as if you got 1 million blind men, put them all in a row, and gave them rubix's cubes and fi they were to solve them all at the same time.
     
  20. May 31, 2004 #19
    Even if that's true (I never heard of anything remotely close to that :smile:), we shouldn't be so surprised. It's similar to the question raised in this thread:
    https://www.physicsforums.com/showthread.php?t=18905
    billy_boy_999 asks how come there so many objects in orbits in nature. HallsofIvy says while there are many objects in orbits, there are a lot more objects which didn't go into orbit so we don't see them today. Similarly, you may find it amazing that the big bang occurred having a chance of only one in a million, but it's not that amazing when you consider the fact that if it hadn't occurred, we wouldn't be here to discuss its probabilities. :smile:
     
  21. May 31, 2004 #20

    Alkatran

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    You know, a funny thing is that I thought about that before I was told it.

    Whenever I would see someone arguing about creationism on tv (or in a book) and how the chances were so low for it to happen HERE etc etc etc I would think: "Well, does it really matter if it's here? There's so many places it could be, and we're only going to ask in the places where it happens... so maybe here is somewhere else."

    Then I read "A Brief History of Time" and learned that this was the anthropic (sp?) principle.


    Pretty neat on my end.
     
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