A team of scientists proposes using gravitational waves to resolve the longstanding 'Hubble tension' in cosmology. The Hubble constant, which measures the universe's expansion rate, yields different values depending on whether calculations start from local or ancient cosmic observations. This discrepancy has puzzled physicists for over two decades.

Current methods rely on Type 1a supernovas for local measurements or the standard model of cosmology for distant observations. The new approach, called the stochastic siren method, analyzes background gravitational waves from distant black hole mergers to provide an independent measurement of the Hubble constant.

The technique could finally settle whether the universe's expansion rate differs between ancient and modern times. As gravitational wave detectors like LIGO-Virgo-KAGRA become more sensitive over the next six years, this method may provide the definitive answer needed to resolve one of physics' biggest mysteries.