You can ‘fire’ a photon from a laser at some initial time, and then at some later time you are highly likely to detect it at another position just as though it went there along a straight-line path from the laser at the speed of light. It seems the ‘reason’ you detected it at B is that it left A and reached B along the most direct path. What’s wrong with that tidy story of cause and effect? Sometimes there really is no harm in telling it as if it happens that way. But we must try as hard as we can to keep that ‘as if’ in sight.
