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Animation of two black holes merging into one. In a new study, scientists used the clearest gravitational wave signal ever detected to “listen” to the sounds of distant black hole mergers and conduct the toughest test yet of Einstein’s gravity. . |Image source: SXS
Scientists have used the loudest gravitational wave signal ever to put Albert Einstein’s more than 100-year-old theory of gravity to its toughest test yet – and it passed again.
The signal, named GW250114, comes from the merger of two signals black hole — each about 30 times the mass of the Sun — are about 1.3 billion light-years from Earth. The event caused ripples in space-time called gravitational waves, which swept across Earth on January 14, 2025, and were detected by the U.S. Laser Interferometer Gravitational-Wave Observatory (LIGO).
Scientists say the incident is very similar to the events leading up to this incident. First direct detection of gravitational waves 2015. This suggests that the black holes in the two mergers were similar in size and distance from Earth.
However, the new signal recorded is roughly three times clearer than the 2015 breakthrough discovery, allowing scientists to test Einstein’s general theory relativity Tighter than ever.
“That was obviously the loudest incident,” Keefe MittmanA postdoctoral fellow at Cornell University’s Center for Astrophysics and Planetary Science and co-author of the new paper told LiveScience. “This event provides more information than anything we’ve seen before about some tests of general relativity.”
The unusual clarity of the signal stems from a decade of steady upgrades to the detector, Mittleman said. These improvements reduce noise sources that once interfered with cosmic signals, including seismic vibrations and even passing trucks. The detector is therefore sensitive enough to the tiny distortions in space-time caused by the recently detected black hole mergers (changes 700 trillion times smaller than the width of a human hair).
The findings are detailed in a study published Jan. 29 in the journal Physical Review Letters.
The “ring” of a black hole
Because the recently detected signal was so clear, Mittleman and his colleagues were able to zoom in on the brief post-merger phase (called “ringing”). During this stage, the newly formed black hole vibrates briefly – like a ringing bell – emitting gravitational waves in different patterns, or “tones,” that encode key properties of the black hole, including mass and spin.
In GW250114, the researchers detected two main tones of such merger predictions. Each tone produced independent measurements of the black hole’s mass and spin, and both matched, effectively verifying general relativitythe team reports in the study.
For the first time, scientists have also confidently discovered a subtler, more fleeting “overtone” that appears at the beginning of the ringing – another feature long predicted by general relativity.
“This event makes it very, very clear that the predictions of general relativity are indeed present in the signal, and that’s really exciting,” Mittleman told Live Science.
If measurements are inconsistent, he adds statement“As physicists, we have a lot of work to do to try to explain what’s going on and what the true theory of gravity is in our universe.”
An earlier analysis of the same event Published in September 2025confirming another major prediction rooted in general relativity proposed by Stephen Hawking more than 50 years ago. Hawking predicts black hole’s surface area – its size event horizon -Never shrinks, even if a large amount of energy escapes in the form of gravitational waves during the merger.
The two LIGO gravitational wave observatories in Washington state and Louisiana are about 1,880 miles (3,030 kilometers) apart. This allows scientists to measure millisecond differences in gravitational wave signals. |Image source: Virgo cooperation/CCO 1.0
In GW250114, scientists estimate that the two primordial black holes have a combined surface area of about 93,000 square miles (240,000 square kilometers) — about the size of Oregon. After the merger, the resulting black hole has a surface area of about 155,000 square miles (400,000 square kilometers) – nearly the size of California – consistent with Hawking’s predictions.
golden age
Despite general relativity’s repeated success in describing large-scale cosmic phenomena, physicists remain skeptical of the theory Cannot be a complete description Gravity in our universe. For example, it cannot explain dark matter or dark energy, which are required to hold galaxies and their star clusters together and explain the accelerating expansion of the universe, respectively. nor can it be fully reconciled quantum mechanicsa framework for governing nature at the smallest scales.
Scientists hope that gravitational waves produced by high-energy black hole mergers may one day show subtle deviations from Einstein’s predictions, which could reveal new physics.
The ringing phase is particularly promising for this type of testing, Mittleman said. Many Beyond Einstein theories predict slightly different vibrational patterns during the ringing phase, so measuring more than one tone, as his team did with GW250114, could help scientists constrain any possible deviations from general relativity.
If differences are found, researchers can compare the data with predictions from other gravity theories to determine which, if any, matches reality.
“There must be some way to resolve this paradox and make our theory of gravity consistent with our theory of quantum mechanics,” Mittleman said in a statement.
Next-generation detectors, including the proposed Einstein Telescope in Europe and the Space Explorer in the United States, will be ten times more sensitive than existing facilities. In addition to detecting more events like GW250114, these detectors will be able to observe low-frequency gravitational waves that correspond to more massive black holes, allowing scientists to detect a whole new class of these cosmic behemoths.
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—History of science: Detection of gravitational waves proves Einstein was right — September 14, 2015
——Large-scale international research shows that a weak “gravitational wave background” generated by black hole collisions is rippling in the universe.
–New research suggests Einstein’s unproven “gravitational memory” theory may be true
Researchers are also looking forward to the European Laser Interferometer Space Antenna (LISA), which is expected to observe gravitational waves from the supermassive black holes at the centers of galaxies. Planned to launch in 2035, LISA is expected to detect a large number of events And dozens of different hues can be revealed in a single black hole merger event, Mittleman said.
“We live in a regime where we don’t have enough data and we’re just sitting around waiting for more data to come in,” Mittman said. “Once LISA comes online, we’re going to be overwhelmed.”
If funding for gravitational wave science continues, he added, “we’re going to see more and more golden events and really start to learn amazing things about the gravitational nature of the universe.”
