Haven't read through the whole thread, but I wanted to make sure that one point is abundantly clear:
The results of the double-slit experiment
does not change "when you watch it", at least not in the way that phrase implies. If you set up the double-slit experiment inside a black box and look the other way while you run the experiment, the results are
exactly the same as if you were to run the same experiments staring intently at it. Plain old visual observation don't mean a thing to the electrons, they're happy to go through both holes and interfere with themselves (creating the familiar interference pattern) whether or not
you are watching. That's a very common misunderstanding of the observer effect.
It's only when you set up a device to detect
which hole the electrons go through that the observer effect comes into play. To detect which hole the electron goes through, any probe you set up must necessarily interact with the electron, and by doing so it changes the electron's behavior. If the probe is determining which hole the electron goes through, then the electron only goes through one hole or the other. It's no longer able to do both an interfere with itself, so you get a standard (non-interference) distribution pattern.
Say, for example, you use a low-intensity light source in the visual spectrum as your probe (an electron passing through light will emit a flash, in this case at whichever hole the electron passes through). You run the experiment, and see no interference pattern because the light (being the observer) disturbs it, causing it to pass through either one slit or the other (it no longer does both). Now suppose you suspect that the light may be disturbing the results and preventing the interference pattern because the energy of the light is too high, so you decide to start increasing the wavelength to lower the energy of the light. Well, initially the results are exactly the same, lowering the energy of the light doesn't make the interference pattern come back.
But remember that the ability to resolve two positions in space with electromagnetic waves (like light) as a probe depends upon the wavelength. As soon as the wavelength is large enough that, although we still see the electrons, we can no longer tell
which hole they pass through, the interference pattern returns. Since the light can no longer differentiate which hole the electron goes through, the electron is once again free to go through both and interfere with itself. While we might still think of the light as an observer (it detects the electrons), it ceases to be relevant in the context of the observer effect because it no longer requires the wavefunction to collapse to a specific eigenstate.
In quantum mechanical terms, an observer is something which interacts with a particle in a way that forces the wavefunction to collapse to a particular eigenstate. I think this can help shed some light on the misunderstanding that informs pau's post above: human consciousness and observation are not requirements in quantum mechanics. The double-slit experiment illustrates this perfectly. The distribution pattern doesn't change at all "when you watch it"; it only changes when you set up instruments capable of differentiating which slit the electron passes through.