A still image of a visualization of the merging black holes that LIGO and Virgo have observed so far. The source video shows numerical-relativity calculations of the black holes’ horizons and the emitted gravitational waves, during the final few orbits of the black holes as they spiral inwards, merge and ring down. Each numerical-relativity calculation is consistent with one of the observations in the LIGO-Virgo catalog. As the horizons of the black holes spiral together and merge, the emitted gravitational waves become louder (larger amplitude) and higher pitched (higher in frequency). Credits: Teresita Ramirez/Geoffrey Lovelace/SXS Collaboration/LIGO-Virgo Collaboration