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Measuring classical object to arbitrary precision

  1. Dec 17, 2011 #1
    This has been nagging me in the background of my mind for many years and I've decided to get it sorted.

    I note that I'm not sure if this should be in the classical or quantum forum.

    I have heard it mentioned by many and often when referring to the inherent uncertainty when measuring quantum objects, that unlike classical objects which can be measured to arbitrary precision, quantum objects....etc

    It's this reference to the apparent precision that puzzles me. They will say, first how as we zero in on the momentum we become more fuzzy about position of a quantum object, unlike say a car or a baseball which we are told can be measured to this so called arbitrary precision.

    My question is, how do we measure this mythical classical baseball that avoids the quantum object problems.

    Do we measure from the centre of the baseball? Where exactly is that, or the leading edge of the baseball, again, where is that because it seems to me that the edge of the baseball is a quantum object.

    Why is the edge of the baseball, the very leading atom, the atom that is most furthest forward of the rest of the baseball any different to a single atom without the rest of the baseball.

    And further, when we are going for this arbitrary precision, then do we not have to use a quantum object to measure. If the baseball is set up to break a beam of photons, then again the photons just bring back the quantum uncertainty if we try to approach this arbitrary precision.
    Last edited: Dec 18, 2011
  2. jcsd
  3. Dec 18, 2011 #2
    You can't avoid it, but you could in a make-believe classical world. I don't think anybody is saying that in the real world you can measure the position and momentum of a baseball bat to a degree of accuracy that violates the Heisenberg uncertainty principle.

    But then again, in the make-believe classical world, you can in principle measure everything accurately..., so the statement about the bat could just as well be made about some kind of a make-believe "classical atom".
  4. Dec 18, 2011 #3
    Ah, ok that makes sense. I get it now. It's a principle sort of like a perfect thought experiment.
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