'Fingerprints' of Black Hole's Event Horizon Detected For First Time (phys.org) 21
Researchers say they detected the first gravitational-wave "fingerprints" of a black hole's event horizon by analyzing the final moments of the powerful GW250114 merger. The findings support Einstein's general relativity and may eventually help probe frame dragging and quantum fluctuations near black holes. Phys.org reports: For the new research published in Nature, an international team of researchers analyzed data from the strongest gravitational wave ever recorded, known as GW250114, detected by the LIGO observatory in January 2025. By isolating the last burst of waves -- known as "direct waves" -- from this black hole merger, the scientists said they were able to extract information from closer to an event horizon than ever before. "This black hole horizon concept normally appears in science fiction," lead study author Sizheng Ma of the Perimeter Institute for Theoretical Physics in Canada told AFP. "But now we are really able to touch the region around the horizon with gravitational data," he added. "Sometimes I cannot believe this is really happening."
The last stage of two black holes merging is like a spoon stirring a glass of water, Ma explained. The resulting swirl in space creates the ripple of gravitational waves that travel at the speed of light in all directions. If the metaphorical spoon is stirring close enough to the black hole's event horizon, "this offers us a chance to decode the physics around that region," Ma said. By supporting the theory of general relativity, the results "proved that Einstein was correct again," he added.
The scientists emphasized that more research was needed to decipher what can be gleaned about event horizons using this method. But they did detect information about how black holes twist space around themselves as they rotate -- a phenomenon known as "frame dragging." "This is similar to pushing a glass into a table and twisting it, so that the tablecloth winds up around it," Maximiliano Isi, a gravitational wave astrophysicist at Columbia University, told AFP. In the future, the scientists hope to find signs of tiny changes known as quantum fluctuations. "In this way, we can really probe this near-horizon region to look for new physics," including searching for a deviation from general relativity, Ma said.
The last stage of two black holes merging is like a spoon stirring a glass of water, Ma explained. The resulting swirl in space creates the ripple of gravitational waves that travel at the speed of light in all directions. If the metaphorical spoon is stirring close enough to the black hole's event horizon, "this offers us a chance to decode the physics around that region," Ma said. By supporting the theory of general relativity, the results "proved that Einstein was correct again," he added.
The scientists emphasized that more research was needed to decipher what can be gleaned about event horizons using this method. But they did detect information about how black holes twist space around themselves as they rotate -- a phenomenon known as "frame dragging." "This is similar to pushing a glass into a table and twisting it, so that the tablecloth winds up around it," Maximiliano Isi, a gravitational wave astrophysicist at Columbia University, told AFP. In the future, the scientists hope to find signs of tiny changes known as quantum fluctuations. "In this way, we can really probe this near-horizon region to look for new physics," including searching for a deviation from general relativity, Ma said.
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Better description, please (Score:5, Informative)
I was able to glean a tiny bit more from the article abstract (lack of Unicode support makes copy/paste difficult):
Still, without being in the gravitational-wave field, it's still pretty hard to see what all the fuss is about.
Re:Better description, please (Score:5, Informative)
Still, without being in the gravitational-wave field, it's still pretty hard to see what all the fuss is about.
Ha, just like being close to a supernova can cause such extreme neutrino flux you can actually die of radiation from it interacting with your body, being within a couple of horizon widths of the merger can probably put such excessive stress on your body from the force of sloshing space time as to actually kill you. Which is kind of insane.
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What’s left off this article is the technicality of what an event horizon is, for there are several types depending on how you look at it. For example, there is the formal event horizon, which is the boundary across which light rays internal to it won’t reach outward but this is nebulous and spread out across space and time. Then there is the apparent horizon, which is the colloquial one people are more familiar with that is the schwarzchild radius static in a moment of time and space that is the boundary where light rays can’t escape from. When two black holes merge, as the two separate horizons approach each other, the localized spacetime can become closed off from the rest of the visible universe without passing either of those two radiuses and before they merge because the average mass in that spacetime vicinity forms a horizon around the two merging black holes. PBS Spacetime [youtube.com] has a nice episode on it. Detailed measurements of mergers will give us a better understanding of the entire picture of how these events play out and shape spacetime.
Still, without being in the gravitational-wave field, it's still pretty hard to see what all the fuss is about.
Ha, just like being close to a supernova can cause such extreme neutrino flux you can actually die of radiation from it interacting with your body, being within a couple of horizon widths of the merger can probably put such excessive stress on your body from the force of sloshing space time as to actually kill you. Which is kind of insane.
Thank you for your added content.
What I meant by "without being in the gravitational-wave field" was less about physically being close to the merger, and more along the lines of "unless you are a physicist that is deep into the literature and nuances of this field". I can see now the double-meaning of my comment: being close to the actual merger would definitely be worthy of fuss.
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Fingerprints of the event horizon? What the hell does that even mean?
It means they asserted a definition of exactly where the rainbow ends, and thereby found the pot of gold.
The pot of gold being that their publishing-grind slop made it into the news and gilds their resume. It's the ultimate win for the modern academician.
skeptical astrophysicist (Score:4, Interesting)
From the cited article;
Sean McWilliams, an astrophysicist at West Virginia University, was skeptical that the gravitational wave frequency analyzed by the scientists was actually "dictated" by the event horizon.
For this reason, "the actual observed signal doesn't really tell us anything about the horizon or the other properties directly related to it," he told AFP.
Re:skeptical astrophysicist (Score:4, Interesting)
Yes (Score:2)
its like a spoon stirring water. Wait no its not. Love the analogies people come up with.
What would happen (Score:2)
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You'd never be able to pull your head out, not that it was likely in the first place.