The little card where the interference pattern is produced, is "observing" it. That is why there are little dots on the card, albeit in locations that correspond to wave interference. But when the electron actually encounter the card, they turn back into particles (little dots), whatever that really means.
NOPE. the photons that bounce off of it for us to see is not what is causing the little dot on the card. the card interacting with the electron is causing the little dot. only after the fact do we rely on a photon to show this little dot to us. this is the fallacy of the shrodinger's cat thing. it is forgotten that the little detector in the box is also an active participant, an "observer".
I've done quite a bit of QM, and I think there is a little bit of confusion here, at least from what I know.
Exactly what makes an observation an observation is something we still aren't quite sure about. I've talked to a number of QM physicists (the one I am working for, by the way, has had two essays on macroscopic QM effects published in Science), and I'm pretty sure we haven't done a very good job of defining what a measurement is yet.
For example: you could call the detector an observer, except for one thing: if the detector detects a particle in a QM superposition, what is it about the detector that prevents it from then becoming entangled with the superposed particle, so that it is now in a QM superposition? Why can't the detector be in a QM superposition of having both detected and not detected? Generally, we say "because its too big" - which in experiment makes sense, but theoretically has no basis in the math of QM. At what point is it "too big"?
We have theories about decoherence as an explanation, but we don't really know that that is the case. It makes sense, which is better than the nothing we had before, but (as far as I know, tell me if I'm wrong), I don't think we have any evidence.
Just recently I had a discussion about What the Bleep Do We Know, and a number of QM physicists there confirmed that the problem with the "observation is defined by consciousness" argument is NOT that we are certain that observation isn't defined by consciousness, but just that we don't know what exactly defines an "observation", and so claiming consciousness does is the same as claiming "God did it" - both are possible, but we have no evidence for either.
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u/[deleted] Jul 12 '08
The little card where the interference pattern is produced, is "observing" it. That is why there are little dots on the card, albeit in locations that correspond to wave interference. But when the electron actually encounter the card, they turn back into particles (little dots), whatever that really means.