Does it matter what the observer is in the double slit experiment? Could it be anything from an ant to a dog? Has it ever been tried with a non-human observer?

  • $\begingroup$ Why would being a human (or not) impact the physics? An unattended camera does a fine job of observation - does non-living count? $\endgroup$
    – Jon Custer
    Sep 1 '15 at 20:59

When physicists say we "observe" the particle that's passing through the slit, they aren't really referring to the person who sees the electron, but rather the photon itself that interacts with the electron. Functionally, it's the photon that's doing the "observing" of the electron. Really, there would be much less confusion about this issue if physicists stopped saying "observe" and said "interact" instead. It's the interaction that causes the wavefunction to collapse.

So, no, in terms of the collapse of the electron's wavefunction, it doesn't matter what the photon goes on to strike next, whether it's a human or a camera or a dog or a tree stump. The "observation" already occurred when the photon hit the electron.

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    $\begingroup$ So people on youtube putting so much importance on consciousness is a bunch of bunk? $\endgroup$
    – Tom Woods
    Sep 1 '15 at 21:10
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    $\begingroup$ Yes - it's not really their fault, though. Physicists like to say that wavefunction collapse is due to "observation" when they actually mean "interaction". All the pseudoscience around the connection between consciousness and wavefunction collapse is just an elaboration on that simple misunderstanding. $\endgroup$
    – Brionius
    Sep 1 '15 at 21:13
  • $\begingroup$ Note that the concept of "quantum consciousness" (the idea that consciousness is a fundamentally dependent on macroscopic quantum effects) is a separate unrelated issue that isn't settled. $\endgroup$
    – Brionius
    Sep 1 '15 at 21:14
  • $\begingroup$ Incorrect, the wave function won't collapse if there's no way of knowing the "which way" information. See Double Slit Quantum Erasure experiments. "observe" actually mean to know the which way information. Now the question is interesting, since when a non conscious entity (like a PC) knows it, that won't collapse the WF. Only if a human may know which way the photon chose, it collapses. It's an interesting question - does it work for other conscious beings? An Animal, or a baby that sees the results on a monitor? $\endgroup$
    – Kof
    Jan 12 '18 at 20:28

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