Newly discovered ripples in spacetime put Einstein’s general relativity to the test

The universe is filled with a cacophony of colliding black holes

By Claire Cameron edited by Clara Moskowitz

When black holes collide, the crash generates ripples in the fabric of spacetime – gravitational waves. These distortions travel far out into the universe, but by the time they reach Earth, they have become weak, making them extremely difficult to detect. Thanks to a global network of observatories—called the Laser Interferometer Gravitational-Wave Observatory (LIGO), Virgo, and the Kamioka Gravitational-Wave Detector (KAGRA)—scientists have found many of these tiny wobbles in spacetime. And now the collaboration has released its latest dataset, more than doubling the number of detections.

The results reveal that our universe resonates with cosmic collisions. Some of the waves originate from pairs of colliding black holes, and others appear to have come from collapsing black holes and neutron stars—the dense, dead cores of massive stars—as well as from two neutron stars collapsing.

The new catalog also reveals a larger variety of known black holes, including some that appear warped and others that spin incredibly fast. Together, the observations are “phenomenal,” says Zsuzsanna Márka, an associate scientist at Columbia University who was previously involved in the LIGO-Virgo-KAGRA collaboration.

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“We’re really pushing the edges, seeing things that are more massive, spin faster and are more astrophysically interesting and unusual,” Daniel Williams, a research fellow at the University of Glasgow and a member of the collaboration, said in a statement.

The expanded set of detections allows astronomers to test Albert Einstein’s general theory of relativity, which asserts that gravity is a geometric property of spacetime.

Doing so could help answer the field’s holy grail, says Szabolcs Márka, a professor of physics at Columbia University who has worked with LIGO and is married to Zsuzsanna Márka. “What is beyond Einstein’s general theory of relativity? Large catalogs pave the way for deep understanding of these enigmas,” he says.

According to the theory, mass distorts the shape of spacetime, causing objects to move on curved paths near heavy masses. The gravitational waves produced by these cosmic collisions will reveal new details about this distortion that may confirm or challenge the predictions of Einstein’s theory.

The catalog is detailed in a forthcoming special issue of Astrophysical Journal Letters, as well as an accompanying journal article that was recently published online. Soon it may be possible to release real-time data from the collaboration, says Márkas.

“Each new gravitational wave detection allows us to unlock another piece of the universe’s puzzle in ways we couldn’t just a decade ago,” Lucy Thomas, a co-author of the paper and a postdoctoral fellow at the LIGO Lab at the California Institute of Technology, said in the statement. “It is incredibly exciting to think about what astrophysical mysteries and surprises we can uncover with future observing runs.”

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