Cataclysmic cosmological events, such as the merging of 2 black holes, distort the fabric of the universe. Gravitational waves produced by merging black holes were first detected by the US National Science Foundation Laser Interferometer Gravitational-Wave Observatory (LIGO) in 2015. The researchers studied the event from the moment the black holes first collided, until the merged black hole settled into its new state just milliseconds later. Left panel: Frequency and decay time (half-life) of the different ‘ringdown’ tones measured in the 2025 black hole merger (GW250114). The black markers indicate the values predicted for a Kerr black hole.