Gravitational Waves Finally Prove Stephen Hawking's Black Hole Theorem (newscientist.com) 40
Physicists have confirmed Stephen Hawking's 1971 black hole area theorem with near-absolute certainty, thanks to gravitational waves from an exceptionally loud black hole collision detected by upgraded LIGO instruments. New Scientist reports: Hawking proposed his black hole area theorem in 1971, which states that when two black holes merge, the resulting black hole's event horizon -- the boundary beyond which not even light can escape the clutches of a black hole -- cannot have an area smaller than the sum of the two original black holes. The theorem echoes the second law of thermodynamics, which states that the entropy, or disorder within an object, never decreases.
Black hole mergers warp the fabric of the universe, producing tiny fluctuations in space-time known as gravitational waves, which cross the universe at the speed of light. Five gravitational wave observatories on Earth hunt for waves 10,000 times smaller than the nucleus of an atom. They include the two US-based detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) plus the Virgo detector in Italy, KAGRA in Japan and GEO600 in Germany, operated by an international collaboration known as LIGO-Virgo-KAGRA (LVK).
The recent collision, named GW250114, was almost identical to the one that created the first gravitational waves ever observed in 2015. Both involved black holes with masses between 30 and 40 times the mass of our sun and took place about 1.3 billion light years away. This time, the upgraded LIGO detectors had three times the sensitivity they had in 2015, so they were able to capture waves emanating from the collision in unprecedented detail. This allowed researchers to verify Hawking's theorem by calculating that the area of the event horizon was indeed larger after the merger. The findings have been published in the journal Physical Review Letters.
Black hole mergers warp the fabric of the universe, producing tiny fluctuations in space-time known as gravitational waves, which cross the universe at the speed of light. Five gravitational wave observatories on Earth hunt for waves 10,000 times smaller than the nucleus of an atom. They include the two US-based detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) plus the Virgo detector in Italy, KAGRA in Japan and GEO600 in Germany, operated by an international collaboration known as LIGO-Virgo-KAGRA (LVK).
The recent collision, named GW250114, was almost identical to the one that created the first gravitational waves ever observed in 2015. Both involved black holes with masses between 30 and 40 times the mass of our sun and took place about 1.3 billion light years away. This time, the upgraded LIGO detectors had three times the sensitivity they had in 2015, so they were able to capture waves emanating from the collision in unprecedented detail. This allowed researchers to verify Hawking's theorem by calculating that the area of the event horizon was indeed larger after the merger. The findings have been published in the journal Physical Review Letters.
I don't understand how this isn't obvious (Score:2)
I'm honestly confused. Wouldn't a higher mass black hole have a bigger event horizon?
Can someone give a slightly more indepth description of what interesting fact was shown here?
Re: I don't understand how this isn't obvious (Score:5, Informative)
You wouldn't expect the relationship to be linear for area. You would naively expect the merging to increase volume linearly, but area more slowly. When you put two spheres of clay together, their surface areas don't sum linearly, but their volumes do.
Re: I don't understand how this isn't obvious (Score:5, Informative)
Re: I don't understand how this isn't obvious (Score:2)
Re: I don't understand how this isn't obvious (Score:2)
Re: I don't understand how this isn't obvious (Score:1)
It's not strictly true that you'd only see light from behind you after you'd passed the horizon. You could see radiation from sources close in front of you that were also falling into the well. The radiation from these could reach you but of course would never make it out.
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nothing about that would be sudden though. You wouldn't know if you were 1" inside or 1" outside the event horizon, for example.
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A black hole compresses matter into a smaller space. Would two black holes compress even further, i.e. does more mass inside a black hole cause more compression? Hawking felt that a black hole was 'maximum compression' and thus this theory was stated, and now is has finally proven.
Just because something is obvious, doesn't mean its reality until proven. If you don't know better, its obvious the sun moves around the earth. A different perspective and more data was needed to prove otherwise.
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I think what you are stating would imply that the volume of the black hole would remain the sum of the volumes of the two black holes. Hawking is predicting that the black hole will be bigger than that still. This is saying that the surface area (of the event horizon) of the black hole is at least as big as the surface areas of the two constituent holes combined. In the way you are explaining it, that means the black hole actually "decompressed". That's not really true though because Hawking doesn't say an
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Correct. A higher mass means a bigger event horizon.
The formula for this is the Schwarzschild radius, r = 2GM/C^2 where G is the gravitational constant, M is mass and C is the speed of light. So yes, the higher the mass, the bigger the event horizon.
Which maps neatly onto this observation that when the blackholes merged the resultant blackhole was not smaller than the radius predicted by adding the two masses together.
Though its more a vindication of Schwarzschild since the conclusion flows naturally from
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I'm honestly confused. Wouldn't a higher mass black hole have a bigger event horizon?
Yes, intuitively you are right. The question is "how much bigger".
Can someone give a slightly more indepth description of what interesting fact was shown here?
Let me try.
Hawking said "bigger enough, that the area of the event horizon of the new black hole will have an area at least as large as the area of the two previous black holes combined". That's interesting because (at this point my understanding is based on normal Euclidean math - I don't think it can be wrong, but maybe someone will correct me - is there a special case?) surface area increases as radius^2 whilst volume increases as radius^3
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Mod parent informative. I also appreciate the clarification of "still-standing" theories downthread [slashdot.org].
Sorry about the anon Yo Mama joke. I just couldn't resist. ;-)
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This isn't about surface area, though. Event horizon is not the surface area of a black hole
Re:One non-inconsistent observation != PROOF (Score:5, Informative)
You are right technically, but what this actually does is disproves other competing theories such as "all the mass disappears inside and the black holes look exactly the same after as they did before" or the idea that "the volume of the event horizon depends on how big the squashed thing inside the blackhole is and will remain the same".
After this observation, Hawking's theory is one of the last ones left standing, so it's "proven" until someone comes up with a better different one that also matches this data.
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I came to post the same....except that bit about the girls.
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Yeah, we need to come up with a name for when there is a post that you really align with, but then in the very last line the author drops some nonsense. Conspiracy theory, why this political party ruined, racial stuff, or just the old standby of gender blaming. Totally unrelated to anything about the subject matter, just something to get off their chest.
Maybe a "Inappropriate non-sequitur" tag. Or something like "The poster was clearly educated but like many in the 2020's has had their brain melted over
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It shows that in this case it is not smaller than the sum, it DOES NOT PROVE that it cannot be smaller.
The word "prove" appears only in the headline, nowhere in the body of the article. Headlines being eye-catching summaries is pretty common practice. Common practice also includes - for scientific matters - drilling down to the source papers to find the purest, rawest, most accurate information.
New Scientist used to be good. Then the girls took over.
Stephen Hawking's black hole theorem
An exceptionally loud collision between two black holes has been detected by the LIGO gravitational wave observatory, enabling physicists to test a theorem postulated by Stephen
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New Scientist used to be good. Then the girls took over.
Couldn't find this on the New Scientist Web site, but Wikipedia says the editors have been
Roger Highfield (2008–2011)
Sumit Paul-Choudhury (2011–2018)
Emily Wilson (2018–2023)[22]
Catherine de Lange (2023–)[23]
Possible post hoc fallacy. And, as you note, one bad article (or headline) doesn't prove that all articles are bad. I assume you have other evidence to support your hypothesis. I don't have any opinion on the goodness of New Scientist.
Re:One non-inconsistent observation != PROOF (Score:4, Informative)
1. This is one observation that shows two merged black holes have an event horizon with an area not smaller that of the sum of the event horizons of the merging black holes. How is that a PROOF of a theorem stating that "when two black holes merge, the resulting black hole's event horizon -- the boundary beyond which not even light can escape the clutches of a black hole -- *cannot* have an area smaller than the sum of the two original black holes" ?!
"Proves" might be too strong, but the No Hair theorem [wikipedia.org] (also not "proven") states that all stationary black holes "can be completely characterized by only three independent externally observable classical parameters: mass, angular momentum, and electric charge." So all black holes are, in effect, identical and what applies to this collision should apply to all.
The paper itself also doesn't say that the surface area of the merged black hole is equal to the sum of the surface areas of its consituents; it just says, "Hawking’s area law, also known as the second law of black hole mechanics, which states that the total area of the black hole event horizons cannot decrease with time."
To put it another way, this theorem and these observations are consistent with the present understanding of general relativity, in contrast to some competing alternatives. On the other hand, their analysis assumes that certain aspects of GR are correct.
2. Is this theorem really "Stephen Hawking's Black Hole Theorem" ? Did he have no other black hole theorems?
Yes, of course he did. Alternative headline: "Observation provides evidence that one of Steven Hawking's black hole hypotheses is not always wrong." Also Hawking wasn't the first or only person to propose this theorem, but, you know, fame has its privileges.
I'm curious how they were able to measure the areas of the black holes, especially both before and after the merger. How long does it take for two black holes to merge? LIGO has only been operational for ten years. "To test the area law, we infer the initial black hole areas using premerger data that exclude up to five merger signal cycles and the final black hole area using postmerger data with one-mode or two-mode models at their earliest time of applicability. ... We extract the properties of the initial and final black holes independently from the premerger and postmerger signal respectively, discarding data in between. ... We therefore infer the black hole properties from the inspiral signal and interpret them directly as the infinite-separation quantities."
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Different fields have different standards of proof. The most rigorous that I'm aware of, is in mathematics, wherein a proposal that almost all the experts think must surely end up being true, can be heavily studied and yet remain "unproven" for an arbitrarily large number of centuries, until eventually someone finds an actual real-world use case for the math that you get if it's NOT true. (The poster child for this is non-Euclidean geometry, but there are lots of other exa
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That's a hell of a lot of energy. (Score:5, Interesting)
Meanwhile... (Score:5, Informative)
As the NYT succinctly put it in their headline [nytimes.com]: "Happy Birthday, LIGO. Now Drop Dead."
Eppur si muove!
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Re:Meanwhile... (Score:5, Informative)
If it is already paid for, why would it need further funding?
I can't tell if you're being intentionally dense or not, so I'll err on the side of naivete. The construction and operational validation has been paid for, which is the largest part of the cost. The ongoing costs are things like salaries, materials and supplies for subsequent operation, maintenance, and improvements, which are far smaller.
There is no scientist I have ever met who thought LIGO was, in the end, a poor choice of investment of national research funds. There were plenty prior to its stunning first detection (myself included) who thought they were chasing ghosts, but all of those doubters have been converted. The important thing to understand is that LIGO's contributions weren't just detection of a black hole merger (in itself, a hugely important event because it demonstrated the hypothesized existence of gravitational waves), but the establishment of a new field of astronomy based on gravitation, an entirely new means to observe the universe that provides information previously completely unobtainable. Our eyes have been opened where we were previously blind, and the ongoing results are, and continue to be, astounding.
There's a nice fact sheet summary at: https://www.ligo.caltech.edu/s... [caltech.edu]
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Re:Meanwhile... (Score:4, Funny)
Just tell his dementia riddled brain that LIGO can detect people in the country illegally. He will overnight you a blank check.
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Just tell his dementia riddled brain that LIGO can detect people in the country illegally. He will overnight you a blank check.
Well, LIGO did find your mom. ;-)
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Re: Bad summary (Score:2)
didn't we establish that he's a fraud? (Score:2)