superkuh 17 hours ago [–]
Coherence isn’t what you think it is. It is not an “alignment in phase” of the sinusoid, like all the lay diagrams show. It isn’t even being the same frequency. In the early days of quantum physics the light sources were mercury arc lamps (muliple freqs) that achieved coherence by shining through tiny pinholes.
Coherence is being a point source. Stars, except for our sun since it is too close, are coherent light sources.
— Hacker News
2022.10.27 Thursday ACHK