A year ago, the LIGO-Virgo-KAGRA Collaboration recorded the clearest gravitational-wave signal seen so far. Dubbed GW250114, it arose from the merger of two black holes that were roughly 30 times the mass of the Sun. In September, the collaboration used the signal to confirm a key prediction about black holes and to test general relativity in the high-velocity, strong-gravity regime that prevailed during the merger (see Viewpoint: Landmark Black Hole Test Marks Decade of Gravitational-Wave Discoveries). Now the team has carried out a more comprehensive test [1]. The results deliver the most stringent single-event verification of general relativity to date and place tight constraints on possible deviations from that theory.
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