General Relativity Survives a Tough Trial
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.
A black hole merger has three main stages: an inward spiral of two orbiting black holes, a crashing together of the bodies, and a relaxation process (ringdown) of the remnant black hole formed by the collision. During ringdown, the remnant emits gravitational waves in a set of specific modes, like a ringing bell producing distinct tones. If general relativity holds, the frequencies and decay rates of these modes should have particular values that are set entirely by the remnant’s mass and spin. But in some alternative theories, the modes also depend on hypothetical fields and the electric charge that the remnant could have.
The collaboration identified multiple ringdown modes in GW250114. Its measured frequencies and decay rates matched the predictions of general relativity, with uncertainties ranging from a few percent to tens of percent. By analyzing all three merger stages together, the team also set bounds on deviations from general relativity that are, in some cases, 2 to 3 times stronger than those obtained from combined analyses of dozens of other fainter signals.
–Ryan Wilkinson
Ryan Wilkinson is a Corresponding Editor for Physics Magazine based in Durham, UK.
References
- A. G. Abac et al. (LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration), “Black hole spectroscopy and tests of general relativity with GW250114,” Phys. Rev. Lett. 136, 041403 (2026).