A faint cosmic hum could solve the Universes expansion mystery

Astronomers have long known the universe is expanding-but exactly how fast remains one of the biggest mysteries in cosmology. Different techniques for measuring the Hubble constant stubbornly disagree, creating the so-called Hubble tension. Now researchers at the University of Illinois Urbana-Champaign and the University of Chicago have unveiled a bold new way to weigh in on the debate using gravitational waves-the faint ripples in spacetime produced by colliding black holes.