You probably heard about this announcement from LIGO yesterday, but I thought I should add some details, and shift the emphasis of the story to where it really belongs: The previous detections of gravitational waves (GW) all originated from the merging of large black holes.  Such mergers can produce relatively strong, but very brief GWs – just a small fraction of a second.  And they produce nothing else – no light or other electromagnetic radiation.  Therefore, these observations could not be confirmed by optical telescopes or other detectors. In contrast, this event, dubbed “GW170817” because it was detected on Aug. […]