Enlarge (credit: NASA/ESA) Ever since LIGO (and now Virgo) started picking up gravitational waves, theorists have gone nuts. The volume of papers on exciting possibilities seems to grow faster than the disk space available to accommodate them. If I were sensible, I would probably ignore them. But I'm not, and you, dear reader, will suffer along with me. When two black holes collide and merge, they emit gravitational waves, but we don't expect them to emit light.