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Overcoming The H.U.P. ?

  1. Sep 4, 2003 #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) Also, if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, or modified?

  2. jcsd
  3. Sep 5, 2003 #2


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    There is a difference between a technological and a theoretical barrier. This is a theoretical one which means that no amount of technology can overcome it if the theory is correct. Only a change in the theory can allow it to be possible.

    The sound barrier is an example of a technological barrier - even at the time the scientists knew that it was possible to fly faster than the speed of sound (bullets of course had already done it), it was just up to the engineers to figure out how.
    Well of course anything is possible. But its highly unlikely that HUP will ever be found to be wrong in general.

    Also, your understanding of HUP is a little simplistic. Its not just that you can't observe exact position and velocity simultaneously, they simply don't exist. There is an inherrent "grainyness" to the universe below which things are unpredictable. Planck time is the shortest interval of time that exists - not just the shortest that can be measured.
    Last edited: Sep 5, 2003
  4. Sep 5, 2003 #3
    Re: Re: Overcoming The H.U.P. ?

    Doesn't that depend on your interpretation of quantum mechanics, rather than on the physics itself?

    My understanding was that it's not yet known whether there is a shortest interval of time (or whether the question makes sense), but that if there is one, it will be somewhere close to the Planck time.

    You're perfectly correct on technological versus theoretical limits, though. You can't get around the uncertainty principle without also getting around quantum mechanics, which is at best not easy. :)
  5. Sep 5, 2003 #4


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    Re: Re: Re: Overcoming The H.U.P. ?

    Well, there is some extremely small wiggle room on the matter, but there is essentially no evidence to support the minority point of view. See Bell's Theorem, which addresses the point directly. The "realism" school - i.e. that position and momentum are real even if they cannot be simultaneously measured - is only possible in a non-local universe. However, all known physical effects obey locality.
  6. Sep 5, 2003 #5
    Re: Re: Overcoming The H.U.P. ?

    1) Is this where the quantum fluctuations come in which is known as virtual particles?

    Also, you mentioned that the exact position and velocity cannot be simultaneously measured, i.e. they simply don't exist.

    2) If there is a "grainyness" to the universe where things are unpredictable then why did you suggest that anything is possible, i.e. that the HUP may be wrong but it's highly unlikely?

    Last edited: Sep 5, 2003
  7. Sep 6, 2003 #6


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    Re: Re: Re: Overcoming The H.U.P. ?

    Yep. There are things in physics that depend on HUP being physically real. Hawking radiation for example. ZPE for another.
    No, you miss my point. When I said anything is possible, I mean that it is possible that our understanding of the universe is wrong - maybe there ISN'T any grainyness to the universe. What I find highly unlikely is that our understanding is that wrong.
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