If I use a narrow slit (e.g. two fingers) to view a distant streetlight, I can see an interference pattern parallel to the slit. Doesn't this mean that the photons passing through the slit must be phase coherent? If I am correct about coherence, then how does it occur? The photons leaving the streetlight are not coherent; are they? Excuse me if this question is stupid. I am just an old fuddy-duddy who just likes to think about physics.