..let's not pretend to know what's going on when the 'wave function' collapses....
The video discussed just describes the experiment, it's purpose is not to cover its weirdness - on the contrary.
The explanation of wave function collapse is hidden in my explanation, though. It's related to entanglement phenomena, which I'll try to explain by using of my broken English.
Try to imagine, you're a sailor, who is staying on the end of floating wharf, to which some boat is attached. Because the sea is stormy, everything (both sailor, wharf and boat) are wobbling up and down, but in different phases. From the perspective of sailor the boat sways randomly.
The observation of electron in double slit experiment is analogous to situation, when sailor touches the boat for a moment, thus exchanging some kinetic energy with it. What will happen, after then? The wharf and boat will start to oscillate
at phase. It means, the sailor will keep his relative position with respect to boat, so he cannot detect any boat wobbling anymore, because he moves by the same way. The wave function of boat has collapsed from perspective of that sailor.
Did you understood this mechanical analogy? If so, how it's related to AWT and double slit experiment? Well, by AWT both electron, both the particles of observer are formed by dense clusters of another undulating particles, recursively. At the moment, electron exchanges some energy with particles of observer during process of observation, the undulations of both systems aren't independent anymore: their internal fluctuations will undulate at phase, too. Briefly speaking, the observer will get
entangled with the electron observed. As the electron isn't undulating independently, its internal undulations will disappear from observer perspective, because the internal motion of both systems has been synchronized.
This is what we are calling a collapse of (electron) wave function. The observer and electron are now undulating like single body - the common center of mass of both objects is forming a private reference frame, a sort of independent island of reality inside of wave ocean - from this idea the concept of many worlds follows.
Was this explanation clear for you at least a bit? As you can see, it's surprisingly simple, if not trivial.
