Let us say we have source that can emit a single photon. We can in principle detect when the photon leaves the source due to the momentum kick. Now let us say this single photon passes through both slits and forms a dot on the far right of the screen. Now if we draw paths through the two slits, the path going through the left slit to the dot on the screen is longer than the path through the right slit due to simple geometry. If the path through the right slit is consistent with the speed of light, then anything traversing the path from the left slit must be travelling faster than the speed of light to arrive at the same time as the photon that passed through the right slit and constructively interfere with it. Alternatively, if the longer path through the left slit is consistent with the speed of light, then the photon going through the right slit must have been delayed somewhat to arrive at the back screen at the same time as the part that followed the left path. What is though to happen here? Is the answer neither, because quantum particles are not precisely located in space at any given time?