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I may be flat-out wrong here, but it seems to me there is a very common misunderstanding of what the double slit experiment results mean, at least by non-physicists, because of the way it is often explained.

The experiment shows that photons behave differently, as particle or waves, depending on how we choose to observe them. The implication is that reality depends on the observer, that somehow the point of view defines the reality. I think this is a widely held misinterpretation of these results (at least by non-physicists), which is almost never clarified when explaining the double slit experiment.

To avoid this confusion I think it is crucial to always clarify that what makes the photon behave as a particle rather than a wave is that it interacted with something else, regardless of being observed or not. Observation requires interaction, so it is true that observation results in particle-like behavior. However, interaction does not require observation. The photon could have interacted with anything else and it would have behaved as a particle, even if no human ever observed it. So it's not really saying that reality depends on the observer, its just that when quantum waves interact with other systems, they behave as particles. When seen this way, it's not nearly as mind-bending.

Am I wrong?

Thanks!

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  • $\begingroup$ What particle-like behaviour are you referring to in the double slit experiment? $\endgroup$
    – ProfRob
    Jul 8, 2020 at 22:30
  • $\begingroup$ @RobJeffries If one observes the photons when they hit the detector, you see an interference pattern, meaning they behave as waves as they pass the slits. However if one observes the photon before the slit to determine through which slit the photon goes through, it generates two lines in the detector instead of an interference pattern, meaning it passed the slits as a particle. $\endgroup$ Jul 8, 2020 at 22:41
  • $\begingroup$ You might find this interesting if you haven't read it. $\endgroup$
    – Charlie
    Jul 8, 2020 at 22:46
  • $\begingroup$ Oh, I thought you meant the usual example of one photon at a time in the apparatus generating an interference pattern, but if you check, then each photon goes through one of the slits. $\endgroup$
    – ProfRob
    Jul 8, 2020 at 23:02
  • $\begingroup$ Photons do not “collapse” into particles. They are detected or not (binary outcome). $\endgroup$ Jul 8, 2020 at 23:41

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Almost no physicists, or scientists for that matter, believe that "reality is somehow linked to the concept of consciousness". That is assuming "there exists an objective reality". Some philosophers doubt this, but in my opinion that just means you claim that the word "reality" has no useful meaning, in which case the whole discussion is pointless.

In a way, the way you explain away your alleged misinterpretation of QM is correct. However, in the modern formulations of the theory (quantum field theory) the basic objects are quantum fields. The concept of a particle in that setting is emergent and approximate, valid only in certain limits (e.g. non-relativistic limit or scattering limit).

On the other hand, in the modern view of non-relativistic quantum mechanics (which is not a universal theory but still useful and valid for a wide range of phenomena), there are particles which have associated wave functions. The idea that "in certain circumstances the same object can be a wave or a particle" is not a claim of physics. It just means that "the most simple physical description of the phenomena involving that one object may use a particle picture or a wave picture depending on circumstances". This does not meen that we do not have a theoretical framework valid in all circumstances. We do! In fact, both quantum field theory, as well as standard non-relativistic quantum mechanics, both do not need to resort to a fundamental distinction between particle and wave behavior.

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