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The Heisenberg Uncertainty Principle

  1. Aug 4, 2005 #1
    The Heisenberg Uncertainty Principle tells us that while it is possible to measure the position and velocity with reasonable accuracy, we cannot measure both an atom's position and velocity at the same time. The reason for this is simple. For instance, to find the position of an atom, we must shine a beam of light which come in small packets, or quanta, also known as photons. The individual photons of each wavelength have an energy inversely related to their wavelength.


    The greater the resolution we want, the smaller the wavelength of light we must use. But the smaller the wavelength, the larger the energy of the packets. If we bombard an atom with a high-energy photon in order to observe it, we may ascertain exactly where the atom was when the photon hit it, but the observation process itself, that is, hitting the atom with the photon will clearly transfer significant energy to the atom, thus changing its speed and direction of motion by some amount. That is the case with our current 'scanning systems'.


    1) But what if we invented new scanning systems which wouldn't cause the same problem, that is, without probing particles with other particles?


    2) What if we could measure an atom's position and velocity at the same time with something that has no energy at all? Is it possible in theory?


    3) Also, if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, modified or overcomed?


    4) What about freezing up the atoms prior to measuring the atom/molecule's position and velocity at the same time?


    5) Would that do the trick, if not, why?


    Whitestar
     
  2. jcsd
  3. Aug 4, 2005 #2

    James R

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    Bear in mind that the Hiesenberg principle is not JUST about measurement. It is about how accurately position and momentum can be defined. In other words, beyond the limits specified by the principle it actually makes little sense to talk about exact positions or momenta.

    Keeping that in mind, let's think about your questions:

    Can you think of any way to do that?

    Only if you can find something with no energy, which I think is impossible.

    Who knows? Future physics may overturn everything we think we know. This is looking into a crystal ball.

    Freezing them up would change their velocities, wouldn't it?
     
  4. Aug 5, 2005 #3

    But how does freezing an atom or molecule changes their velocity? If you can freeze an atom/molecule to absolute zero, shouldn't it freeze an atom/molecule in place?


    Whitestar
     
    Last edited: Aug 5, 2005
  5. Aug 6, 2005 #4

    James R

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    Sorry, I misunderstood what you were saying.

    The problem with freezing an atom to absolute zero is simply that it can't be done. If it could be, then we could violate the uncertainty principle.
     
  6. Aug 6, 2005 #5

    Yes, but why can't we reach absolute zero?


    Whitestar
     
  7. Aug 7, 2005 #6

    James R

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    Because doing so would violate the uncertainty principle!

    Circular, I know, but that's the way the universe seems to work.
     
  8. Aug 8, 2005 #7
    The third law of thermodynamics:
    It is impossible by any procedure, no matter how idealized, to reduce any system to the absolute zero of temperature (0 K/−273.15°C/−459.67°F) in a finite number of operations.

    They can come close... but not absolute.
     
  9. Aug 8, 2005 #8

    DaveC426913

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    Atoms, when reduced to abs zero, form what is called a Bose-Einsteinian Condensate - in effect, they stop becoming individual atoms and form an amorphous blob - defeating an attempt to measure them.

    An atom reduced - even theoretically - to abs zero will still not freeze its electrons and protons. It does not literally stop in place and become a well-behaved hard ball.


    "if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, modified or overcomed?"

    It is possible, but it is important to be aware that it is not simply a matter of getting better at measuring. For HUP to be overturned would require a radical new understanding of our universe, not simply better measuring techniques.
     
    Last edited: Aug 8, 2005
  10. Aug 8, 2005 #9

    James R

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    Even a Bose-Einstein condensate has a temperature greater than zero.
     
  11. Aug 9, 2005 #10
    i like whitestar's idea

    If you cooled atoms down to say 1 degree Kelvin, clearly their oscillations and jittering would slow down as well. That said, if you then bombarded them with high energy photons, wouldn't it make measuring the 'cooled' atoms position and velocity much easier, that say, firing photons at hotter atoms?

    Surely, Heisenberg's Principle would not be violated, but in effect, the limit to how precisely one could know the exat position and velocity of the 'cooled' atom's electron(s) would be more refined and accurate.

    What do you think?
     
  12. Aug 9, 2005 #11

    DaveC426913

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    Yes, I did not mean to imply otherwise. I merely meant to point out that, even before you reach abs zero, the effect happens and their position/velocity can't be measured.
     
  13. Aug 9, 2005 #12

    DaveC426913

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    It is not merely a matter of a round, hard ball coming to a stop. Atoms actually lose their identity as individuals - each one physically "spreads out" and blurs, until the properties of position and velocity no longer apply.
     
  14. Aug 9, 2005 #13

    1) Are you saying that atoms "spreads out" or becomes blurry once they reach absolute zero, or before they reach absolute zero?

    2) Could some extremely advance technology overcome this in the far future?


    Whitestar
     
    Last edited: Aug 9, 2005
  15. Aug 10, 2005 #14

    Math Is Hard

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    Just curious - is this Bose-Einsteinian Condensate considered a state of matter? How close to abs zero does the temperature have to get for this effect to occur?
     
  16. Aug 11, 2005 #15
    dave, So then what becomes of the electrons at 0 degrees kelvin? Can you site experiments or data to back up your claims?
     
  17. Aug 11, 2005 #16
    dave, Do the quarks comprising the atom blur out and flatten too? What actually happens here?

    Please don't answer with an analogy unless its scientific in nature, ty.
     
  18. Aug 12, 2005 #17

    James R

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    A BEC is a state of matter. It occurs when the particles get close enough together for their quantum wavepackets to start to overlap sufficiently.

    In practice, BECs in dilute atomic vapours, occur at about 1 nK above absolute zero (thats 0.000 000 001 degree about absolute zero).
     
  19. Aug 12, 2005 #18

    Math Is Hard

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    Thanks. :smile: I had no idea.
     
  20. Aug 12, 2005 #19
    this thread is reminding of eistein/bohr arguement on this same principle. it is a joke.:rofl: but exaggarated :redface:
    but i found its first half in the book 'einstein's cosms' by dr. kaku! dont know if it is true :confused:

    einstein=oh! cmmon god doesnt play dice.
    bohr=stop god telling what to do. :devil:
    e=cmmon :uhh:
    b=stop telling me what to do. :tongue2:
    e= :cry: :surprised

    gurkha-war-horse
     
    Last edited: Aug 13, 2005
  21. Aug 14, 2005 #20
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