Physicists confirm by observations for the first time Hawking’s theory of black holes

There are some rules that even the most extreme things in the universe must follow. The central laws of black holes predict that the region of their event horizon – the boundary where nothing can escape – will never shrink. This law is Hawking’s area theory, named after the physicist Stephen Hawking, who derived this theory in 1971.

Fifty years later, physicists at MIT and elsewhere confirmed the Hawking zone theory for the first time, using observations of gravitational waves. Their results appeared today in physical review message.

In the study, the researchers took a closer look at GW150914, the first gravitational wave signal detected by the Laser Interferometer Gravitational Wave Observatory (LIGO), in 2015. The signal is the product of two inspiring black holes giving birth to new black holes, along with a large amount of Energy that is propagated through space-time in the form of gravitational waves.

If the Hawking region theory is correct, then the horizon area of ​​the new black hole cannot be smaller than the total horizon area of ​​the original black hole. In the new study, physicists re-analyzed signals from GW150914 before and after the cosmic collision and found that the total area of ​​the event horizon did not decrease after merging – a result they reported with 95% confidence.

Their findings are confirmation of the first direct observations of Hawking’s zone theory, which has been proven mathematically but has not yet been observed in nature. The team plans to test future gravitational wave signals to see if they will further confirm Hawking’s theory or be a sign of new law-perverting physics.

“It’s possible that there will be zoos with different compact objects, and while some are black holes that follow Einstein and Hawking’s laws, others are possible,” said lead author Maximiliano Essie, a NASA postdoctoral fellow at MIT, Maximiliano Essie. different monsters.” Kavli Institute for Astrophysics and Space Research. “So it’s not like you take this test once and it’s done. You do this once, and that’s the beginning.”

Co-authors of the content on this paper are Will Farr of Stony Brook University and the Flatiron Center for Computational Astrophysics, Matthew Geisler of Cornell University, Mark Schell of Caltech, and Saul Tiukolsky of Cornell University and Caltech.

the era of vision

In 1971, Stephen Hawking proposed area theory, which launched a series of fundamental ideas about black hole mechanics. The theory predicts that the total area of ​​the black hole’s event horizon—and all black holes in the universe, for that matter—will never decrease. That statement oddly parallels the second law of thermodynamics, which states that the entropy, or degree of disorder in an object, must never decrease.

The similarities between the two theories suggest that black holes can behave as thermal objects that emit heat – a puzzling proposition, as it is believed that black holes essentially never allow escape or radiation. In the end, Hawking squared the two ideas in 1974, showing that black holes can have entropy and emit radiation over very long periods of time if quantum effects are taken into account. This phenomenon has been dubbed “Hawking Radiation” and remains one of the most fundamental discoveries about black holes.

“It all started with Hawking’s realization that the total area of ​​the black hole’s horizon would never decrease,” Issy said. “The District Code exemplifies the golden age of the 1970s where all these ideas were generated.”

Hawking and others have since shown that area theory works mathematically, but there was no way to compare it to nature until LIGO. First detection of gravitational waves.

Upon hearing of the results, Hawking immediately contacted LIGO’s co-founder, Kip Thorne, Feynman Professor of Theoretical Physics at Caltech. The question is: Can the discovery confirm area theory?

At that time, the researchers did not have the ability to select the necessary information in the signals, before and after merging, to determine whether the final horizon region was not decreasing, as Hawking’s theory postulated. It wasn’t until a few years later that the development of the technique by Isi and his colleagues, when testing the laws of the region, became possible.

before and after

In 2019, Isi and colleagues developed technology for echo extraction Immediately after the peak of GW150914 – when the two original black holes collided to form a new black hole. The team used this technique to select specific frequencies, or pitches for loud effects, which they could use to calculate the mass and main rotation of the black hole.

The mass and rotation of a black hole are directly related to the region of its event horizon, and Thorne approached them, bearing in mind Hawking’s question, with a follow-up: Can they use the same technique to compare signals before and after merging, confirming the region theory?

The researchers accepted the challenge, and once again split the GW150914 signal into peaks. They developed a model to analyze the signal before the peak, which corresponds to the black hole’s inspiration, and to determine the mass and rotation of the two black holes before they merge. From this estimate, they calculated the total horizon area — an estimate roughly equal to about 235,000 square kilometers, or roughly nine times the size of Massachusetts.

Then they used their previous method to extract the “ring” or reflection of the newly formed black hole, for which they calculated its mass, rotation, and finally the area of ​​its horizon, which they found to be 367,000 square kilometers (about 13 times the area of ​​the Bay State).

“The data show with great confidence that the area of ​​the horizon has increased after the merger, and that the law of the area is met with very high probability,” Issy said. “It is a relief that our results agree with the model we expected, and confirm our understanding of this complex black hole merger.”

The team plans to carry out further tests of the Hawking region theory, and other old theories of black hole mechanics, using data from LIGO and Virgo, its Italian partners.

“It’s exciting that we can think in new and innovative ways about gravitational wave data, and ask questions that we thought we couldn’t do before,” said Issy. “We can continue to extract bits of information that speak directly to what substrates we think we understand. One day, this data might reveal something we didn’t expect.”

This research was supported in part by NASA, the Simmons Foundation, and the National Science Foundation.

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