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Scientists have captured the clearest ever gravitational waves—ripples in the fabric of spacetime—a breakthrough that has resolved decades-old mysteries about black holes and the nature of our reality, according to a study published on Wednesday in Physical Review Letters.
Gravitational waves forged by an ancient merger between two massive black holes reached Earth on January 14 of this year, where they were picked up by the Laser Interferometer Gravitational-Wave Observatory (LIGO) located in Washington and Louisiana. LIGO has discovered hundreds of these waves, but the January event, known as GW250114, is the cleanest detection ever made with a signal-to-noise ratio of 80 (meaning that the signal is about 80 times louder than the noise).
The unprecedented clarity allowed scientists to confirm predictions about black holes that were made a half-century ago by pioneering theorists Roy Kerr and Stephen Hawking, known respectively as the Kerr metric and Hawking area theorem. According to the new study, the results represent “a milestone in the decade-long history of gravitational wave science,” a field that was born in 2015 with the historic first detection of these elusive waves.
“We had promised that gravitational waves would open a new window into the universe, and that has materialized,” said Maximiliano Isi, a gravitational-wave astrophysicist and assistant professor at Columbia University and the Flatiron Institute who co-led the study, in a call with 404 Media.
“Over the past 10 years, the instruments have continued to improve,” added Isi. “We are at a point now where we are detecting a collision of black holes every other day or so. That said, this one detection, which has an extremely high signal-to-noise ratio, really drives home how far this field has come along.”
Gravitational waves are subtle ripples in spacetime that are produced by energetic cosmic events, such as supernovas or mergers between black holes. Albert Einstein was the first to predict their existence in his 1916 general theory of relativity, though he was doubtful humans could ever develop technologies sensitive enough to detect them.
These waves oscillate at tiny distances that are thousands of times smaller than the width of a proton. To capture them, LIGO’s detectors shoot lasers across corridors that stretch for 2.5 miles and act like ultra-sensitive tripwires. The advent of gravitational wave astronomy earned the Nobel Prize in Physics in 2017 and marked the dawn of “multimessenger astronomy,” in which observations about the universe can emerge from different sources beyond light.
GW250114 has a lot in common with that inaugural gravitational wave signal detected in 2015; both signals came from mergers between black holes that are about 30 times as massive as the Sun with relatively slow spins. Gravitational wave astronomy has revealed that black holes often fall into this mass range for reasons that remain unexplained, but the similarity of the 2015 and 2025 events throws the technological progress of LIGO into sharp relief.
“Every pair of black holes is different, but this one is almost an exact twin” to the first detection, Isi said. “It really allows for an apples-to-apples comparison. The new signal is detected with around four times more fidelity, more clarity, and less relative noise than the previous one. Even though, intrinsically, the signal is equally powerful to the first one, it’s so much neater and we can see so much more detail. This has been made possible by painstaking work on the instrument.”
The high quality of the signal enabled Isi and his colleagues to test a prediction about black holes proposed by mathematician Roy Kerr in 1963. Kerr suggested that black holes are simple astrophysical objects that can be boiled down to just two properties: mass and spin. GW250114 was clear enough to produce precise measurements of the “ringdown” signatures of the merging black holes as they coalesced into a single remnant, which is a pattern akin to the sound waves from a ringing bell. These measurements confirmed Kerr’s early insight about the nature of these strange objects.
An illustration of the two tones, including a rare, fleeting overtone used to test the Kerr metric. Image: Simons Foundation.
“Because we see it so clearly for the first time, we see this ringing for an extended period where there is an equivocal, clear signature that this is coming from the final black hole,” explained Isi. “We can identify and isolate this ringing from the final black hole and tease out that there are two modes of oscillation.”
“It’s like having two tuning forks that are vibrating at the same time with slightly different pitches,” he continued. “We can identify those two tones and check that they’re both consistent with a single mass and spin. This is the most direct way we have of checking if the black holes out there are really conforming to the mathematical idealization that we expect in general relativity—through Kerr.”
In addition to confirming Kerr’s prediction, GW250114 also validated Stephen Hawking’s 1971 prediction that the surface area of a black hole could only increase, known as Hawking’s area theorem. Before they merged, the black holes were each about 33 times as massive as the Sun, and the final remnant was about 63 solar masses (the remaining mass was emitted as energy in the form of gravitational waves). Crucially, however, the final remnant’s surface area was bigger than the combined sum of the areas of the black holes that created it, confirming the area theorem.
“We are in an era of experimental gravitation,” said Isi. “We can study space and time in these dynamically crazy configurations, observationally. That is really amazing for a field that has, for decades, just worked on pure mathematical abstraction. We are hunting these things with reality.”
The much-anticipated confirmation of these predictions puts constraints on some of the most intractable problems in physics, including how the laws of general relativity—which governs cosmic scales of stars and galaxies—can coexist with the very different laws that rule the tiny quantum scales of atoms.
Scientists hope more answers can be revealed by increasingly sophisticated detections from observatories like LIGO and Virgo in Italy, along with future projects like the European Laser Interferometer Space Antenna (LISA), due for launch in the 2030s. Despite LIGO’s massive contribution to science, the Trump administration has proposed big cuts to the observatory and a possible closure to one of its detectors, which would be a major setback.
Regardless of how the field develops in the future, the new discovery demonstrates that the efforts of generations of scientists are now coming to fruition with startling clarity.
“It is humbling to be inscribed in this long tradition,” Isi said. “Of course, Einstein never expected that gravitational waves would be detected. It was a ludicrous idea. Many people didn’t think it would ever happen, even right up to 2015. It is thanks to the vision and grit of those early scientists who fully committed despite how crazy it sounded.”
“I hope that support for this type of research is maintained, that I’ll be talking to you in 10 years, and I will tell you: ‘Wow, we had no idea what spacetime was like,’” he concluded. “Maybe this is just the beginning.”
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