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The Devil's Gun

  1. Aug 25, 2012 #1
    A question for you learned gentlemen and ladies:

    The Devil being a crafty sort of fellow and not caring one nit about gun control laws decides to create a gun of infinite barrel length, loaded with a bullet containing an infinite charge of gunpowder/blackpowder or the like.

    Presuming his iron works have found a way to create a bullet that can withstand such forces...

    At what point in the barrel does the bullet achieve maximum acceleration?

    (I have from reliable sources that Newton was consulted via long distance telegraph and the answer wasn't as simple as hoped.)

    [mods please feel free to move this to a different area if required]
  2. jcsd
  3. Aug 25, 2012 #2

    Vanadium 50

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  4. Aug 25, 2012 #3


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    A crafty fellow like the devil would not likely waste his time on a gun that can't be pointed at anything, so what does it matter?
  5. Aug 25, 2012 #4


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    Nomdeplume, Welcome to Physics Forums!

    You specify in your thought experiment an "infinite barrel length" What is half (or any fraction) of an infinite length?

    Real scientists are frustrated when infinities appear in their calculations. Is there some hidden point or a disquised message in your experiment?

  6. Aug 25, 2012 #5
    Thank you Bobbywhy, long time lurker but only a couple of posts.

    Agreed, the infinite appears to present a thorny issue for physicists, cosmologists, theologians and philosophers from Bruno to Zeno.

    Your perception of my question is spot on; there was a hidden point, or at least question of sorts:
    My understanding (and please) correct me if I'm wrong is the is that the bullet in the devils gun would would could undergo constant acceleration and/or reach a theoretical limit...or indeed the very framing of the question makes it nonsensical.

    My confusion/concern comes in with the application of answers of the aforementioned to the accelerating expansion of the Universe (whether it is a closed system or an open system and if the energy contained therein is infinite would determine if it is at all analogous).

    I certainly appreciate everyone's time and consideration.
  7. Aug 26, 2012 #6


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    Nomdeplume, you have an unusual way of expressing yourself and as a result I cannot understand what you are asking. From your last post:

    “My confusion/concern comes in with the application of answers of the aforementioned” [which you described as “nonsensical”]

    “to the accelerating expansion of the Universe” [Yes, this is in accordance with the Standard model.]

    “(whether it is a closed system or an open system” [is this your question?]

    “and if the energy contained therein is infinite” [infinite energy…that’s really a lot!]

    “would determine if it is at all analogous).” [analogous to what?]

    It appears to me you are continuing to hide your question with unclear, or even mystical, English language. If you seriously desire some answer to a real question I promise you members here in Physics Forums are ready, fully qualified, and willing to assist you to overcome your “confusion/concern”.

    If you would please write out a clear and simple question, or express concisely what your doubt is, you may expect a reasonable answer. If you are not serious and just want to troll around with obscure unfathomable statements sprinkled with scientific terms then please don’t return.

  8. Aug 26, 2012 #7
    I don't think that this infinite gun is in any way analogous to the expanding universe. Gunpowder can not be compared to the dark energy that drives the expansion.
    Most importantly gunpowder has a maximum rate of expansion (around 2000m/s).
  9. Aug 26, 2012 #8
    My apologies if I came across troll like, not my intent and I'll work on cleaning up the language to make it more precise as well. I left study of physics years ago for continental philosophy but it still fascinates me.

    I created original analogy to simplify the system.

    Is the universe a closed system? (analogous to the barrel of the gun)
    Is the volume of the universe infinite? (length of barrel of gun)
    Is there a constant theoretically inexhaustible, or at least at this point not yet exhausted energy source? (gunpowder) Thank you DrZ., to clarify I didn't really mean gunpowder but rather an energy source that leads to expansion.

    At what point does the bullet achieve maximum acceleration?

    Again, I appreciate the effort and responses, if it is nonsensical then the thread can be closed.
  10. Aug 26, 2012 #9


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    Those are good questions and if you can come up with a verifiable answer for either of them, I predict a Nobel Prize in your future.
  11. Aug 26, 2012 #10
    I don't think Newton had access to telegraphs during his time, better check that 'source' ;)
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