Gravitational waves refine cosmic expansion rate ⚡ экспресс
For the first time, scientists combined gravitational wave signals from merging neutron stars with data on how galaxies are distributed and bend light. This allowed them to measure the expansion rate of the Universe: 68 km/s per megaparsec. The new method could solve the puzzle of why different measurements give different speeds.
Measuring the universe’s expansion is like timing a race when the track stretches. Neutron star mergers act as standard sirens: their gravitational waves ring out with a known “volume,” so fainter signals mean greater distance.
A new study paired the siren from merger GW170817 with a galaxy map tracing matter, including dark matter (invisible mass first detected by Vera Rubin). The result: the Hubble constant (named after Edwin Hubble) is 67.9 km/s per megaparsec—so a galaxy 3.26 million light-years away recedes at that speed—with just 6.4% uncertainty.
This value eases a cosmic dispute: the early universe’s afterglow suggests slower expansion, while nearby exploding stars point to faster. The new number falls between them, highlighting the strength of cross-checking methods. Remarkably, the spacetime ripples from GW170817 jiggled our detectors by less than a proton’s width, yet clocked the universe’s growth.
🎯 The term 'standard siren' echoes 'standard candle,' but while candles use light, sirens use gravitational waves—a clever twist on an old cosmic yardstick.