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Could a ball lying on the ground spontaneously bounce?

  1. Oct 11, 2011 #1
    My textbook tells me that balls don't randomly bounce upward because it is improbable that all of the thermal motion of the particles suddenly align in one direction (upward). But it is just improbable right, or is it impossible?

    I guess what I'm asking is, is entropy only a statistical expression and thus the ball could bounce, or would this violate the second law?
     
    Last edited by a moderator: Oct 11, 2011
  2. jcsd
  3. Oct 11, 2011 #2

    DaveC426913

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    All objects above absolute zero are jittering with molecular motion. Essentially, at a very tiny scale, the ball is spontaneously bouncing from the occasional accumulation of molecules bouncing on the same direction. It's just really tiny.

    Have you ever seen Brownian motion act on grains of pollen?

    I believe the answer is that it is indeed vanishingly improbable. Like on the order of the age of the universe.
     
  4. Oct 11, 2011 #3
    So entropy really is just a statement of probability then? And the ball, however improbable it is, can violate the second law? Or is this not a violation of the second law?
     
  5. Oct 11, 2011 #4

    DaveC426913

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    It is not. The system is not closed.
     
  6. Oct 11, 2011 #5

    jtbell

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    It is not impossible, but it is very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very very improbable. :smile: (Maybe a mole of "very"s would be enough.)

    Fundamentally, the second law of thermodynamics is a statistical statement. With ten molecules, violations are uncommon but do occasionally occur. With a hundred molecules, they become highly unlikely. With a thousand molecules, you're probably more likely to win the Powerball jackpot. With a mole of molecules... well...
     
  7. Oct 12, 2011 #6
    There is no way that heat will apply a downward force to a ball of any normal size sufficient to flex it. Work must be done to store energy. This work must not violate the third law of motion. There is nothing in the air, nor anything else, which can absorb the force of the heat in such a manner to supply this downward force. Absent of external thrust or a light enough ball, say with a nano-thin flexible shell with great elasticity, it will *never* happen.
     
    Last edited: Oct 12, 2011
  8. Oct 12, 2011 #7
    Any time you question whether or not something is "possible," the answer(in todays Quantum view of the universe) the answer is yes.

    Is it possible for the ball to morph into a hungry lion and eat you? Yes. How possible? Thats intuitive...
     
  9. Oct 12, 2011 #8
    That of course is not going to happen, let alone spontaneously.
     
  10. Oct 12, 2011 #9
    Just because its not GOING to happen, doesn't mean it CAN'T happen.

    What are the odds of a small dense point of matter and energy expanding into an entire inhabitable universe? Not very good.
     
  11. Oct 12, 2011 #10

    DaveC426913

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    A ball spontaneously changing into a hungry lion is impossible by physics as we know it.

    A ball spontaneously jumping off the ground is fabulously unlikely, but there is no principle - except that of cumulative probabilities - preventing it from happening.
     
  12. Oct 12, 2011 #11

    DaveC426913

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    One.
     
  13. Oct 12, 2011 #12
    just because it occurred does not mean its probability was one.

    Rolling a dice and getting a four does not mean there was a one hundred percent chance of getting a four.

    I would say the chances of the ground and rubber ball suddenly disappearing, or exploding, or turning into a lion, are no less likely than a small point of energy winking into existence on the quantum scale(or however you believe the story went before the big bang) and suddenly expanding into and cooling into a universe with a set of rules favorable to the evolution of intelligent life.

    P never is one or zero in a quantum universe
     
  14. Oct 12, 2011 #13
    Walking through a wall is also possible but it's splendidly unlikely.
     
  15. Oct 12, 2011 #14
    Correct. If you had an infinite amount of time, and walked into the wall over and over, you would walk through it an infinite number of times.
     
  16. Oct 12, 2011 #15
    Given eternity within the sea of vagueness (state of pre-exisitence, pre-something/nothing) a chance for Universe to arise (e.g. via Big Bang) is surely one. (Since it did happen once.)

    A ball to turn into an lion within our Universe which isn't eternal cannot have a chance of one.

    In short, Universe happens infinite times, while each Universe isn't lasting forever... Only if it could then I'd agree that a ball can suddenly morph into a lion or whatever.
     
  17. Oct 12, 2011 #16
    Yes, but then again, (since we're talking about the same universe), you have to give the ball the same domain. It will surely at some point turn into a man eating lion...given an infinite amount of time.

    Considering nothing about the universe, or its origins, is known to be infinite, the odds of either are highly unlikely.

    We got lucky once.
     
  18. Oct 12, 2011 #17

    phinds

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    And that's in addition to the fact that you would ALSO likely spend an infinite amount of time in the emergency room getting your nosed fixed on all the times when it didn't work.
     
  19. Oct 12, 2011 #18
    This is correct. Except that your monetary resources are probably not as infinite as they would need to be to support such an endeavor.
     
  20. Oct 12, 2011 #19
    Partly we seem to agree, that is, in case when we consider SAME Universe being eternal, as I added in my above post while you were answering me:
    "In short, Universe happens infinite times, while each Universe isn't lasting forever... Only if it could then I'd agree that a ball can suddenly morph into a lion or whatever."

    Also, if we consider that pre-conditions for Big Bang are eternal and each Universe is not, then we have a disagreement.

    But who cares right, we won't live long enuff to see who's right, right? Or will we? ;)
     
  21. Oct 12, 2011 #20
    Well, the singularity is near...
     
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