Cosmic hum from black hole mergers could refine the universe’s expansion
Physicists propose using the faint, unresolved gravitational-wave background from countless distant black-hole mergers as an independent way to measure the expansion rate of the universe (the Hubble constant), potentially helping resolve the Hubble tension. Even without directly detecting this background, current data already place bounds on H0; upcoming detector upgrades could turn this into a precise measurement, offering a new tool for cosmology while highlighting limitations tied to population models and large uncertainties.
