For those who watch gravitational waves roll in from the universe, GW250114 is a big one. It’s the clearest gravitational wave signal from a binary black hole merger to date, and it gives researchers an opportunity to test Albert Einstein’s theory of gravity, known as general relativity.

“What’s fantastic is the event is pretty much identical to the first one we observed 10 years ago, GW150914. The reason it’s so much clearer is purely because our detectors have become much more accurate in the past 10 years,” said Cornell physicist Keefe Mitman, a NASA Hubble Postdoctoral Fellow at the Cornell Center for Astrophysics and Planetary Science in the College of Arts and Sciences.

Mitman is a co-author of the paper analyzing the wave, “Black Hole Spectroscopy and Tests of General Relativity with GW250114,” published in Physical Review Letters on Jan. 29. It was written by the LIGO Scientific Collaboration, the Virgo Collaboration in Italy and the KAGRA Collaboration in Japan. Cornell researchers have been leading contributors to the LIGO-VIRGO-KAGRA project since its beginning in the early 1990s.

The gravitational wave GW250114, a ripple in space-time set off by two black holes colliding, reached U.S.-based Laser Interferometer Gravitational-Wave Observatories (LIGO) on Jan. 14, 2025. Each wave is numbered by the date it was detected and the LIGO-VIRGO-KAGRA team announced this one in September 2025. It conforms to general relativity, Mitman and collaborators have found in their analysis, although they and others theorize that not all binary black hole collisions will, which offers an opportunity to explore fundamental laws of physics.

When two black holes merge, the collision rings like a bell, emitting specific tones characterized by two numbers, Mitman said: an oscillatory frequency and a damping time. If you measure one tone in data from a collision, you can calculate the mass and spin of the black hole formed in the collision. But if you measure two or more tones in the data – which a clear signal such as GW250114 allows – each is effectively giving you a different mass and spin measurement, according to general relativity.

“If those two measurements agree with one another, you are effectively verifying general relativity,” Mitman said. “But if you measure two tones that don’t match up with the same mass and spin combination, you can start to probe how much you’ve deviated away from general relativity’s predictions.”

GW250114 was clear enough for the researchers to measure two tones and constrain a third. All agree with Einstein’s general relativity.

What if they had not?

“Then we would have had a lot of work to do as physicists to try to explain what’s going on and what the true theory of gravity would be in our universe,” Mitman said. It’s possible, he and collaborators believe, that future gravitational waves will fall outside Einstein’s general relativity theory, giving insight into unresolved questions.

Physicists suspect that Einstein’s theory of general relativity is wrong at some point because it doesn’t account for a lot of things in the universe related to gravity, such as dark energy and dark matter, Mitman said. Also, general relativity breaks down when physicists try to make it consistent with the physics they use to describe the quantum realm.

“There has to be some way to resolve this paradox to make our theory of gravity consistent with our theory of quantum mechanics,” Mitman said. “Along those lines, we expect there to be some deviation from Einstein’s classical prediction, where you might see signatures of quantum gravity imprinting themselves on these gravitational wave signals.

“The hope is that we’ll see these deviations one day and that will help guide us along what the true theory of quantum gravity might be.”

Kate Blackwood is a writer for the College of Arts and Sciences.