>Well, as soon as you "observe" it, we will no longer see an interference pattern That's not strictly true, because the experiment is observing the quantum, an

>Well, as soon as you "observe" it, we will no longer see an interference pattern That's not strictly true, because the experiment is observing the quantum, and it is seeing an interference pattern. The critical thing is that they're observing it after the quantum has gone through the slits, so as it passes through the slotted wall, it's wavefunction is not constrained. So the moment of observation is very important.