Xi-Jing Wang

Future gravitational wave detectors will see millions of black hole mergers. Sometimes the signal won’t arrive just once—massive invisible objects, like mountains, will create echoes. By measuring the delays between repeats, scientists will determine what fraction of dark matter is made up of primor

The universe is full of black holes, but middleweights long eluded detection. Now distortions in radio signals have given them away, as if invisible masses altered the voice of distant bursts. These could be Big Bang relics hiding in dark matter.