Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Impossible to predict where a particle will be

  1. Apr 6, 2005 #1
    Quantum physics states that it is impossible to predict where a particle will be for any interval of time. Another discipline states that if it were possible to track and predict the movement of all of the particles in the universe, it would be possible to predict the future.

    It is impossible to predict where a particle will be, but would it be reasonable to assume that each particle has a definite, predefined path?

    I know very little of quantum physics - I know the gist of it, but nothing more, so please correct me where necessary.
  2. jcsd
  3. Apr 6, 2005 #2
    There is no agreed upon answer to this question. To put it loosely, QM has to do with "observables", not with "actuals". SO you will find arguments for both sides, it is really a matter of philosophy.

    In order for this to be reasonable, there has to be a reason.

    Experiments do not give us any reason.

    But causes and effects (unique effects corresponding to each cause) are such a fundamental part of our world, it is tempting to assume that this cause and effect structure applies to quantum mechanics.

    In truth, it is deeper than this. When we say the world has causes and effects, we are refering to a theory that humans have that consistently "explains" our world. It is even true that continuous motion (on the macroscopic scale) as we percieve it, is a construct of our brain.

    So what you are really asking is:

    "Is it possible to have a consistent theory that explains subatomic behavior but describes the particles as having continuous paths?"

    The answer is: yes, if we are creative.
  4. Apr 7, 2005 #3
    Thanks, I have always had a quite strong physics mind, but recently I have found a certain interest in philosophy. 4 nights ago, I had an epiphany while arguing the philosophy of religion with my room mates on a band trip which I recently returned from. I combined Newtonian and quantum physics as well as a little conjecture on my part to develop a...erm...hypothesis on the nature of existence. (If we do really exist.) Is anyone interested or should I post on the philosophy forum?
  5. Apr 7, 2005 #4
    next year in A levels i should be doing both physics and RS with lots about philosophy, so i can't say that i mind you talking about this...

    hell, physics probably would't even exist without the questions of philosophy
  6. Apr 7, 2005 #5
    Ok, I am working on a paper...I never thought I would do academic work for fun, but here I am doing it. It won't be formal or properly organized or anything like that, but once I finish it, I will post it here.
  7. Apr 8, 2005 #6
    Don't be so enthusuastic about A-level physics. They barely touch through the implications of particle (note: it is NOT into real QM yet) physics, or even philosophy.

    However, private individual study of some sort will help you.
  8. Apr 8, 2005 #7
    But whether there will ever be a theory that allows us to predict the position of a particle or not does not only depend on our creativity. Nature also has to work that way, maybe it does not!
  9. Apr 10, 2005 #8
    I have to disagree. I know very little about Quantum Physics and I've never even taken Physics I(I'm a sophmore in HS), but the one thing I do know about it is Shcrodinger's Cat Paradox. Now tell me that's about "observables", and not the lack there-of.

    And yes, I realize you said "To put it loosely", I just had to say something.
  10. Apr 10, 2005 #9


    User Avatar
    Science Advisor
    Gold Member

    It would be reasonable, yes, but completely wrong. There is plenty of evidence that particles in fact do NOT behave in this manner in except in an approximate fashion. If you are working at the level in which exactness is required, then assume NO as the answer. (I.e. do not assume that particles have definite predetermined paths as the next step in your theory development.)
  11. Apr 10, 2005 #10
    QM is about things we can observe. Shrodinger's Cat illustrates that it is impossible to predict (in a certain situation) whether or not a cat will be alive or dead. QM says that we cannot predict some things any better than just giving the odds (probability) that it will happen or not.

    QM does not have anything to say about whether the cat is alive, dead, or both during the time that we are not observing it! This is the lie they tell you in these popular books for non-physicist about QM, but it is not true; QM is all about "observables" as opposed to "actuals". QM does not apply to the 'real' world, but only gives the odds on the outcome of various observations of the 'real' world.
  12. Apr 10, 2005 #11
    Philsophical methods have been tried and tested, just like QM methods have been tried and tested.

    'I think therefore I am', was one egotistical (not philosophical!) viewpoint.

    You can not confirm your existence, but you can go a long way to confirm 'other' existence, for example, when your with your love one's, their interaction to you being with them, can show that THEY confirm your existence, and if you respond to them, as they to you, then this is about as close you can get to confirmation of your existence, and at the same time extend your acknowledgement to the existence of 'others', I am sure your contemplations will be fruitfully answered?

    Instead of the Egotistical:I think therefore I am how about Modern Rap:They think I am, therfore I is ! o:)
    Last edited: Apr 10, 2005
  13. Apr 11, 2005 #12
    I was kinda just making a play on words with the whole conditional of the experiment that you not be able to observe the cat. Guess it didn't really work. I do, however appreciate what you say about the physics books lying to you, it's nice to know that before I take the class!
    Are you suggesting that we precieve things that do not actually exist. I've heard that theory before, but is there any proof? It has to exist "somewhere" for us to precieve it, correct? (and by "somewhere" I mean if not where we expect it to exist, it atleast exists in our mind)
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook