Gravitational Echo Will Reveal the Number of Primordial Black Holes ⚡ экспресс

A black hole merger gives birth to a gravitational wave. Sometimes the wave’s path is blocked by a galaxy or a clump of dark matter, predicted by Zwicky and discovered by Rubin. A massive object, like a mountain slope, reflects the signal, and we receive echoes—copies with different delays.

Part of dark matter could be primordial black holes—objects from the time of the Big Bang. If there are many, they noticeably alter the pattern of gravitational echoes, even as a tiny admixture. New detectors, whose concept was advanced by Rainer Weiss, will measure the frequency and delays of such repeats.

A surprising fact: the delay between echoes can last months. In that time, light manages to travel tens of thousands of light-years, while the gravitational signal only crawls to us. By comparing the original pulse and its copies, astronomers will map out the distribution of ancient black holes more precisely than any telescope.