Data from 17 colliding black holes has provided the first real-world test of a theory that says gravity might not be local.
April 25, 2026
Original Paper
Gravitational-Wave Constraints on Causal Nonlocal Kernels: Ringdown Bounds and Spectral Density Limits from GWTC-3
SSRN · 6395478
The Takeaway
Standard physics assumes that gravity only acts on things that are right next to each other in space-time. These new observations of gravitational waves let researchers put strict limits on nonlocal gravity, which suggests that distant parts of the universe could be fundamentally linked. By analyzing the ringdown phase of black hole mergers, they were able to see if gravity deviates from Einstein's predictions. This is the first time we have ever had empirical data to test these exotic modifications of space-time. It moves us one step closer to confirming whether our standard understanding of local reality is actually correct.
From the abstract
We establish the first observational bounds on causal nonlocal extensions of gravity characterised by retarded Stieltjes-type kernels with positive spectral density ρ(µ) ≥ 0, using two complementary gravitational-wave channels. From a Bayesian ringdown analysis of 17 binary black hole events in the LIGO-Virgo GWTC-3 catalogue, we set the observational ceiling on universal fractional quasi-normal mode deformations at |εΩ| < 0.05 (90% C.L.), with a cumulative log Bayes factor ln B =-0.46 ± 0.77. B