I understand the former part, but how do you arrive at the latter?
“but how do you arrive at the latter?”
By the seeming instantaneous interferance.
Re this topic, take a look at Wheeler’s thought experiment and actual implementations of it. Here’s an OK starting place: http://en.m.wikipedia.org/wiki/Wheeler’s_delayed_choice_experiment?wasRedirected=true
Too tired to get into it. Let’s just say it get very weird, with some clearly atemporal (from our frame of reference) aspects.