oritteropo says... She addresses this in a follow-up video (still doesn't have the real experiment, but does have Neil deGrasse Tyson): vil said: Was hoping for an actual experiment. You cannot both "detect" a photon/electron before it "enters a slit" and have it go through and "detect" it again at the back. That part is (probably) hogwash. Detection at this scale really means fatal crash or at least deflection. From what has been observed it would appear that in such an experiment an individual electron takes all the possible paths through both slits and the "waves" that "interfere" are waves of probability of the particle passing through detection points. While it might as well be magic, really, QED does have observable rules, and this video might make it appear as though one could change the outcome by blinking an eye, which is not the case. To make any headway stop thinking about tiny marbles. Think about tiny cartoon characters moving so fast they are smudged to invisibility whirring their tiny appendages around - you can only tell which particle and where it is if you swat it or it hits a wall and stops moving. There is no "detect but keep going as if nothing happened".