The waves in space-time confirm the centenary theory

New observations of two merger black holes confirmed the predictions made decades ago by Albert Einstein, Stephen Hawking and Roy Kerr.

Ten years ago, scientists first took undulations in the fabric of space-time, known as gravitational wavesProduced by the collision of two black holes. Now helped by improved instrumentation and a good fortune, a newly observed black hole The merger offers the most final opinion so far on the behavior of black holes – and, in the process, provides a long -sought -after confirmation for key predictions by Albert Einstein and Stephen Hawking.

The latest measures come from the laser interferential wave observatory (Ligo), with analyzes led by astrophysicists Maximiliano ISI and Will Farr of the Flatiron Institute Center for Computational Astrophysics in New York. The results illuminate the properties of the black hole and the underlying structure of space-time, suggesting possible contact points between quantum physics and the general relativity of Einstein.

“This is the clearest opinion of the nature of black holes,” explains ISI, who is also a deputy professor to Columbia University. “We have found some of the strongest evidence to date that astrophysical black holes are the predicted black holes from the theory of general relativity of Albert Einstein.”

The results were recently published in the journal Physical examination letters by Ligo-Virgo-Kagra collaboration.

Black holes and gravitational waves

For massive stars, black holes mark the last stage of their life cycle. Their severity is so intense that even light cannot escape. When two black holes collide, they deform the space itself and generate gravitational waves which travel outwards through the cosmos, similar to the way a bell sounds after being struck.

These deforming undulations, called gravitational waves, can say a lot to scientists on the objects that created them. Just as a large iron bell emits different sounds from a smaller aluminum bell, the “sound” that a black hole fusion is specific to the properties of the black holes involved.

Scientists can detect gravitational waves with special instruments in observatories such as Ligo in the United States, Virgo in Italy and Kagra in Japan. These instruments carefully measure how long it takes a laser to browse a given path. While the gravitational waves extend and compress space-time, the length of the instrument, and therefore the journey time of light, changes carefully. By measuring these tiny changes with great precision, scientists can use them to determine the characteristics of black holes.

The newly reported gravitational waves were created by a merger which formed a black hole with the mass of 63 Suns and turning to 100 revolutions per second. The results took place 10 years after Ligo did the first detection of merger of black hole. Since this historic discovery, improvements in equipment and techniques have enabled scientists to obtain a much clearer overview of these space events.

“The new pair of black holes is almost twins at the first historic detection in 2015,” said ISI. “But the instruments are much better, so we are able to analyze the signal in a way that was not possible 10 years ago.”

With these new signals, ISI and his colleagues have given a complete look to the collision from the moment when the black holes first placed each other until the final reverberations while the merged black hole settles in its new state, which only occurred by milliseconds after the first contact.

Previously, the final reverberations were difficult to capture, because at that time, the ringing of the black hole would be very low. Consequently, scientists could not separate the ringing from the collision from that of the last black hole itself.

Unlock the ringing of black holes

In 2021, the ISI conducted a study with a cutting -edge method that it, Farr and others developed to isolate certain frequencies – or “tones” – using data from the 2015 black hole fusion. This method proved to be powerful, but the measures of 2015 were not clear enough to confirm key predictions on black holes. With the new, more precise measures, however, ISI and his colleagues were more convinced that they had managed to isolate the signal of longer of the final black hole. This allowed more unambiguous tests of the nature of black holes.

“Ten millisecondes seem really short, but our instruments are so much better now that it is enough for us to really analyze the last black hole,” explains ISI. “With this new detection, we have an extremely detailed view of the signal before and after the merger of the black hole.”

The new observations have allowed scientists to test a key conjecture dating from decades that black holes are fundamentally simple objects. In 1963, the physicist Roy Kerr used the general relativity of Einstein to mathematically describe the black holes with an equation. The equation has shown that astrophysical black holes can be described by only two characteristics: spin and mass. With new best quality data, scientists have been able to measure the frequency and duration of the ringing of the black hole fused more precisely than ever. This allowed them to see that indeed, the merged black hole is a simple object, described by its mass and its spin.

Observations were also used to test a fundamental idea proposed by Stephen Hawking called the Hawking area theorem. He indicates that the size of the horizon of the event of a black hole – the past line that nothing, not even light, can come back – can only develop. Testing if this theorem applies requires exceptional measures of black holes before and after their merger. After the first Black Hole merger detection in 2015, Hawking wondered if the signing of the merger could be used to confirm its theorem. At the time, no one thought it was possible.

In 2019, a year after Hawking death, the methods had improved enough for a first provisional confirmation to be used by using techniques developed by ISI, Farr and his colleagues. With four times a better resolution, the new data give scientists much more confidence than Hawking theorem is correct.

Black holes and time arrow

By confirming Hawking theorem, the results also refer to connections to the second law of thermodynamics. This law stipulates that a property which measures the disorder of a system, called entropy, must increase, or at least remain constant, over time. Understanding the thermodynamics of black holes could lead to progress in other areas of physics, including quantum gravity, which aims to merge general relativity with quantum physics.

“It is really deep that the size of the event horizon of a black hole behaves like entropy,” explains ISI. “It has very deep theoretical implications and means that certain aspects of black holes can be used to mathematically probe the true nature of space and time.”

Many suspect that future black holes fusion detections will no longer reveal the nature of these objects. During the next decade, detectors should become 10 times more sensitive than today, allowing more rigorous tests of the characteristics of black holes.

“Listening to tones issued by these black holes is our best hope of learning the properties of extreme space times they produce,” explains Farr, who is also a professor at Stony Brook University. “And while we build increasingly gravitational waves detectors, precision will continue to improve.”

“For so long, this area has been pure mathematical and theoretical speculation,” explains ISI. “But now we are able to see these processes amazing in action, which underlines the progress that there is – and will continue to be – in this area.”

Reference: “GW250114: Testing the law on the Hawking region and the Kerr nature of black holes” by Ag Abac, I. Abouelfettouh, F. Acernois, K. Ackley, C. Adamcewicz, S. Adhicary, D. Adhikari, N. Adhikari, RX Adhikari, et al. (Ligo Scientific, Virgo and Kagra Collaborations), September 10, 2025, Physical examination letters.
Doi: 10.1103 / KW5G-D732

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