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Absolute symmetrical sphere become unsymmetry

  1. Nov 20, 2008 #1
    Say we have an absolute sphere ball which is consist of an fully filled with air which the ball cannot expand anymore, as further pumping air will cause the ball explode. As a few air inside is leaked, the ball will not shrink since its membrane is inelastic, hence causing the ball to become a different shape where it will not became symmetry anymore.

    Is this statement is true? Will an absolute symmetry inelastic ball will no more become absolute symmetry again after a little air is leaked? (The ball might be in symmetry in a few axis but still not in infinite axis way.) Can somebody prove this statement is wrong?

    I am thinking of this question relating to the broken symmetry in particle physics. I am thinking of this phenomena which might lead to the symmetry breaking idea.
  2. jcsd
  3. Nov 20, 2008 #2


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    Welcome to PF!

    Hi lol1986! Welcome to PF! :smile:

    If the air leaks through a hole, then the sphere can simply start collapsing along the diameter ending at that hole …

    is there any reason why the sphere should not remain rotationally (in two dimensions) symmetric?
  4. Nov 20, 2008 #3
    Because it just in symmetry in one or two axis, that's what I mean it is not symmetrical in other possible axis such as when when symmetrical axis being shifted to 0.000001 degree will do it so.

    Ok, I found that air leak sphere is really not a good example.

    What I thought is when a absolute symmetrical sphere is contracting after it is being expanded (as it been symmetrical when expanding), the sphere will no more being absolute symmetrical anymore (tough it might being symmetry in a few axis). During the expansion, the boundary, or 'membrane' should be forced to formed according to the expanded contains, kind of like plastic deformation, and contraction will cause the boundary to be out of shape and cannot become absolute symmetrical anymore.

    It quite hard to explain but this is what inside my imagination.
  5. Nov 21, 2008 #4


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    Hi lol1986! :smile:

    The trouble with making a hole is that the hole itself breaks the symmetry …

    you need an example where you don't interfere unsymmetrically …

    the example usually quoted is a pencil standing on its point …

    it's in equilibrium, but sooner or later it will fall, and when it does the symmetry will be broken. :smile:
  6. Nov 21, 2008 #5
    I know it is talking about symmetry breaking...
    But the standing pencil doesn't represent the symmetry situation at the beginning. That's why I used sphere here.

    I don't understand what is the meaning of "interfere unsymmetrically". Do you mean the symmetry breaking must not be an "intentionally" interfere and it should be a natural way for it to be happen?

    Well, that is what I wanted to pointed out, an expanded sphere will not become symmetry anymore when it started to contract. The cause of contraction is expansion of itself, and thus causing the symmetry breaking. There wouldn't be any "intended" external interfere which cause the breaking.

    Why expansion must be follow up by contraction? So that its also represent the symmetry upon of its action, of what I thought to be truth.
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