Scientists have made four new detections of gravitational waves—ripples in the fabric of space and time—emanating from separate black hole mergers. So far, the US-based LIGO and Europe-based VIRGO gravitational-wave detectors have recorded gravitational waves from a total of 10 black hole mergers and one merger of neutron stars. The new events are known as GW170729, GW170809, GW170818, and GW170823, in reference to the dates they were detected.