Comment on double slit

sj_zero@lotide.fbxl.net ⁨7⁩ ⁨months⁩ ago

• RememberTheApollo_@lemmy.world ⁨7⁩ ⁨months⁩ ago

  Perhaps it would be better to explain why instead of attempting a mic drop based on your superior knowledge?

  It’s called the observer effect, and it happens because:

  This is often the result of utilizing instruments that, by necessity, alter the state of what they measure in some manner.

  And particularly in the double-slit experiment:

  Physicists have found that observation of quantum phenomena by a detector or an instrument can change the measured results of this experiment.

  en.wikipedia.org/wiki/Observer_effect_(physics)

  So for anyone who wants to have a surface understanding of the observer effect, the wiki does a fair job of the basic explanation.

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  • sudoreboot@slrpnk.net ⁨7⁩ ⁨months⁩ ago

    The interference disappearing from measurement is not really because the instrument alters the state. Or, at least, putting it like that occludes the more fundamental reason.

    Fundamentally, measurements are subject to the uncertainty principle, which dictates that one can not define precisely the values of two complementary observables at the same time. Position and momentum of any quantum object are such complementary observables, so measuring one – for example position – requires that the other (momentum) becomes less defined.

    When the position of a particle is narrowed down to a pixel on a detector screen, its momentum becomes very uncertain and we must talk about all the possible paths it might have been on in order for it to have arrived at that point.

    The probability of a particle being measured at any given pixel is given by the probability of all possible paths combined, but with an important quirk: when combining each possible quantum state, they interfere with each other such that they may cancel out. It’s sort of like adding together vectors on the unit circle - usually the result is a shorter vector. Repeated measurements of positions give you what appears to be wave-like interference due to the way the probabilities of all paths interfere.

    By checking which slit a particle passes through, you exclude all the possible paths through the other slit and end up not observing the same pattern because the two slits simply do not interfere.

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  • oce@jlai.lu ⁨7⁩ ⁨months⁩ ago

    I think the issue is that quantum mechanics is hard to popularize without leading people into wrong conclusions, pop science clickbaits make this worse.
    I find it easier to understand if you say that observing necessarily means there’s an exchange of energy, otherwise no information can be retrieved, and however small that information retrieval energy is, quantum systems are so sensitive, that it is enough to modify their behavior.

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    • RememberTheApollo_@lemmy.world ⁨7⁩ ⁨months⁩ ago

      Agreed completely, especially about the clickbait-y titles that are at best half-truths. Quantum mechanics are difficult to grasp even on a surface level for sure.

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