Scientists recently utilized a groundbreaking gravitational-wave signal, named GW250114, to put Albert Einstein’s theory of gravity to the ultimate test—and it held up once again.
This powerful signal originated from the merger of two black holes, each about 30 times heavier than our sun, situated roughly 1.3 billion light-years from Earth. When these black holes collided, they created ripples in space-time known as gravitational waves, which reached Earth on January 14, 2025. The Laser Interferometer Gravitational-Wave Observatory (LIGO) in the U.S. was able to detect these waves.
Interestingly, this latest signal was recorded with about three times the clarity compared to the first direct detection of gravitational waves in 2015. As Keefe Mitman, a researcher involved in the study, noted, “This one event provided more information than everything we’ve seen before regarding certain tests of general relativity.”
Years of improvements to LIGO’s detectors helped enhance the clarity of this recent signal. These upgrades reduced noise from sources like seismic vibrations and activity from nearby roads, allowing scientists to detect minute distortions in space-time—changes as tiny as 700 trillionths of a meter.
In a detailed study published in the journal Physical Review Letters, researchers were able to analyze the merger’s unique “ringdown” phase, where the newly formed black hole wobbles like a bell. This phase allowed scientists to glean important details about the black hole’s mass and spin, echoing predictions made by Einstein’s general relativity.
The merger event validated another long-standing theory by Stephen Hawking: a black hole’s event horizon, or surface area, can never shrink, even after mass and energy are lost during a merger. For instance, the combined surfaces of the two original black holes was about 93,000 square miles—similar to Oregon’s size—while the resulting black hole grew to approximately 155,000 square miles, close to California’s size.
Despite the successes of general relativity, physicists believe it may not fully explain gravity in our universe. It struggles to address dark matter and dark energy, which are crucial in understanding galaxy formation and the universe’s expansion. Gravitational waves from massive black hole mergers could help identify any discrepancies in Einstein’s predictions and lead to new discoveries in physics.
Next-generation detectors like the proposed Einstein Telescope and the U.S.-based Cosmic Explorer are set to be ten times more sensitive than current facilities, aiming to uncover previously hidden truths about black holes. The European Laser Interferometer Space Antenna (LISA), launching in 2035, is expected to detect even more gravitational waves, offering greater insights into supermassive black holes located at the centers of galaxies.
As Mitman puts it, “We’re entering a golden age of gravitational wave astronomy.” With continued funding and advancements, scientists anticipate a wealth of data that could redefine our understanding of gravity and the universe.
For further reading, check out the study in Physical Review Letters here.
