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Double slit confusion from observed particle dynamics.

  1. Jul 8, 2012 #1
    Hey Guys,

    I continue to get mixed messages about the nature of electron behaviour during the double slit experiment.

    I have heard the term observation used to describe an interaction with the electron (Obviously necessitating a change in it's behaviour to facilitate the ballistic outcome).

    But also I've had individuals swear by the idea that the electron KNOWS it's being observed and changes accordingly so that we are unable to achieve a wave pattern when testing if a single electron goes through both slits.

    Can anyone clear this up once and for all?

  2. jcsd
  3. Jul 8, 2012 #2


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    Electrons of course don't "know" anything, BUT ... they ACT as though they know whether or not they are being observed. Based on human experience and intuition, this is nonsensical to the point of being impossible, but nature really doesn't care what we think, it just does what it does.
  4. Jul 10, 2012 #3
    Can you cite any physics papers or similar?

    I really dont know what to make of it if the double slit experiment truly shows the result being the electron acting as though it knows we are testing it without the interference negating the wave effect.
  5. Jul 10, 2012 #4
    Whenever there is (select kind of) interaction with the photon, the behavior of the photon changes (due to change in the relative phase between the various paths). Whether a human/life-form is watching, or not, is irrelevant.
  6. Jul 10, 2012 #5
    I find this idea intriguing. You seem to be implying that it is possible that the particle still takes both paths even after we measure it. It's just that by measuring it we have thrown the two paths out of phase, and so the interference pattern disappears.

    I know that you weren't directly advocating such a position, but I find the possibility interesting, and I shall make a note to keep it in mind when contemplating other seemingly mysterious quantum effects.

    I also wonder if there is any way to test whether the particle still takes both paths.
  7. Jul 10, 2012 #6


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    You are trying to understand quantum mechanics from the human perspective. I mean you no disrespect when I say that it has been tried by smarter people than either of us and as Richard Feyman (a VERY smart physicist) said "no one understands quantum mechanics".

    Quantum mechanics and cosmology do NOT fit at all well with human intuition.
  8. Jul 10, 2012 #7

    Feynman said that in 1965, since then we have not only come to understand it better, but better than the entirety of Feynman's knowledge on the subject.
    If we truly did not understand many aspects of quantum mechanics, we couldnt produce such amazing inventions and innovations that we have presently.

    I used to quote Feynman in the same manner when I was starting out learning Quantum mechanics. But to say that we do not have much of an understanding of quantum mechanics because one very smart man who pioneered in the field >50 years ago when it was still primitive in it's understand, devalues the entirety of our findings on the subject to date.

    As with the post above discussing photon interaction, we yet again come back to whether the wave intereference pattern breaks down due to interaction with the particle "which logically makes sense" or some kind of "supernatural" intervention of the particle because we tried to observe it interfere with itself using detectors.
  9. Jul 10, 2012 #8


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    The understanding of QM is in the Mathematics but there are different Interpretations of quantum mechanics.

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