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January 27, 2014 4:12 PM   Subscribe

From I Fucking Love Science: "In a paper posted online this week Professor Stephen Hawking claimed that black holes do not exist - at least, not as we currently understand them. He claims that the traditional notion of a black hole's "event horizon" from which nothing can escape, even light, is incompatible with quantum physics. If so, physicists will have to redefine black holes entirely."

"According to Hawking, "The absence of event horizons mean there are no black holes - in the sense of regimes from which light can't escape to infinite". His paper "Information Preservation and Weather Forecasting for Black Holes" has not yet been published or peer reviewed, but can be freely read online. Typically, the scientific community and media would wait until the peer review process was complete before sitting up and taking notice, but when the author is Professor Stephen Hawking things change a little. Hawking has studied black holes for decades and was the first to challenge the notion that nothing can escape a black hole. He theorized that black holes emit a type of radiation now known as "Hawking radiation", an idea now widely accepted.

According to his new paper, rather than an event horizon, black holes have an "apparent horizon". This apparent horizon only holds matter and energy temporarily, and it is eventually released. This idea would reconcile quantum theory and general relativity's predictions for black holes, and solve the "black hole firewall paradox" that has been plaguing physics for the last two years.

You can read his paper online, or you can read the extensive discussions in both Nature and New Scientist to gain a greater understanding of this new hypothesis."
posted by runcibleshaw (44 comments total) 23 users marked this as a favorite

 
Via Stack Exchange: Why does Stephen Hawking say black holes don't exist?
posted by Blazecock Pileon at 4:14 PM on January 27 [3 favorites]


The scientific community, perhaps, but the media is all too willing to jump on unpublished, unreviewed stuff as long as it has a catchy hook -- witness the "Facebook will lose 80% of its users" boomlet last week.
posted by aaronetc at 4:24 PM on January 27 [2 favorites]


This apparent horizon only holds matter and energy temporarily, and it is eventually released.

Sounds like a hook to bring Omega back as next year's big Doctor Who villain.
posted by RonButNotStupid at 4:27 PM on January 27 [4 favorites]


Isn't this just an outgrowth of Hawking's encyclopedia bet, where he disavowed actual event horizons in favor of apparent horizons?
posted by klangklangston at 4:29 PM on January 27


Yay! The ending of Poul Anderson's "Dialogue" becomes less completely awful!
posted by Zed at 4:32 PM on January 27


Yay! The premise of Andromeda becomes more plausible (even if the story arc goes off the rails in the late seasons).
posted by Pirate-Bartender-Zombie-Monkey at 4:35 PM on January 27 [2 favorites]


Damn! Now Event Horizon will seem so dated!
posted by brundlefly at 4:44 PM on January 27 [19 favorites]


Newspaper headline writers and editors are sometimes so dense that not even the lede can escape, thus proving that black holes are real.
posted by Joey Michaels at 4:49 PM on January 27 [10 favorites]


Black Holes are pretty extreme objects (infinitely dense singularities etc) and trying to explain how they work and fit in with everything else has been tying Physics in knots for decades. In contrast, the idea that they might not ever form in the first place is a lot tidier. This reminds me of another theory that states that Black Holes (as classically understood) cannot exist: instead (some say) they are Magnetospheric Eternally Collapsing Objects
posted by memebake at 4:56 PM on January 27


Relevant
posted by goethean at 4:59 PM on January 27


Just going on the links here, so apologies if I'm totally wrong.

Hawking is solving the Firewall Paradox by redefining what a black hole is. Rather than giving up Unitarity (Which I don't really understand, but apparently its loss would have crazy implications for things like the Second Law of Thermodynamics?) he's saying that the black hole will eventually give up the information that it sucked inside along with all that energy. So no firewall.
posted by Kevin Street at 5:08 PM on January 27 [1 favorite]


V.I.N. CENT disagrees with Stephen Hawking. That shit is real!
posted by Chuffy at 5:10 PM on January 27 [4 favorites]


"I call it a Hawking Horizon."
posted by backseatpilot at 5:18 PM on January 27 [21 favorites]


I cannot favorite that enough.
posted by runcibleshaw at 5:19 PM on January 27


From the Nature link:
Now Hawking proposes a third, tantalizingly simple, option. Quantum mechanics and general relativity remain intact, but black holes simply do not have an event horizon to catch fire. The key to his claim is that quantum effects around the black hole cause space-time to fluctuate too wildly for a sharp boundary surface to exist.

In place of the event horizon, Hawking invokes an “apparent horizon”, a surface along which light rays attempting to rush away from the black hole’s core will be suspended. In general relativity, for an unchanging black hole, these two horizons are identical, because light trying to escape from inside a black hole can reach only as far as the event horizon and will be held there, as though stuck on a treadmill. However, the two horizons can, in principle, be distinguished. If more matter gets swallowed by the black hole, its event horizon will swell and grow larger than the apparent horizon.

Conversely, in the 1970s, Hawking also showed that black holes can slowly shrink, spewing out 'Hawking radiation'. In that case, the event horizon would, in theory, become smaller than the apparent horizon. Hawking’s new suggestion is that the apparent horizon is the real boundary. “The absence of event horizons means that there are no black holes — in the sense of regimes from which light can't escape to infinity,” Hawking writes.
posted by Kevin Street at 5:25 PM on January 27


I wish he'd make up his mind... amirite?
posted by runcibleshaw at 5:29 PM on January 27


At least this will make interstellar travel a lot safer.
posted by Flashman at 5:30 PM on January 27 [3 favorites]


There's nothing really to go on in the posted paper. I've heard it being talked about in terms like 'not much more than a lengthy abstract'.
I think we need to wait for him to say more and not go overboard about it right now just because of his fame.
posted by edd at 5:37 PM on January 27


As much as everyone loves Stephen Hawking, doesn't he need to submit to peer review like every other scientist? I don't want to get excited about this until other physicists have had a chance to poke holes in it.
posted by double block and bleed at 5:45 PM on January 27 [1 favorite]


Overboard? It's not like I'm burning my physics textbooks (Lies! It's all lies!) - this is just an interesting packet of concepts to unravel and try to understand. The Firewall Paradox thing alone is really cool.
posted by Kevin Street at 5:46 PM on January 27


"Damn! Now Event Horizon will seem so dated!"

Sequel: Apparent Horizon where Sam Neill only seems possessed by the devil, but is really just in need of psychiatric intervention.
posted by klangklangston at 5:51 PM on January 27 [10 favorites]


It's actually a transcript of a talk, not a paper really. It's not the sort of thing you would submit for peer review.
posted by edd at 5:57 PM on January 27


I'm with edd on this.

Just a comment about the problem that the people worried about the black hole firewalls are wrestling with. The issue is what happens immediately after you pass a black hole's event horizon. We've always been perfectly fine with throwing our hands up about what happens at the black hole's center (the singularity), where classical general relativity predicts infinite energy density. Well, not perfectly fine, we of course want to know what the hell is going on with quantum gravity and all that, but we are pretty sure that something interesting and new can occur when the local energy density goes to infinity, so the fact that our models predict Crazy Shit is ok - it's an extrapolation into a regime where we expect it to go wrong.

However, a black hole horizon has no particularly interesting LOCAL properties. The energy density and metric curvature (the local property of gravity that tells you what the force of gravity at that point will be) at the event horizon are completely well behaved. While for a very small black hole (you know, a solar mass or so), before you pass the event horizon you'd be ripped to shreds by the tidal forces, that's nothing particularly special, it's just a property of the very small size of the object in question (planets have a similar sphagettification effect, except it only is noticeable on other large objects like moons. It's called the Roche Limit). A big enough black hole classically should have no interesting effect when you pass the event horizon; we could in principle be passing the event horizon of an immense (Universe-scaled) black hole right now, and nothing of note would occur. Thus, if something needs to be changed at the event horizon, it signals a real problem with physics we thought we understood well.

The firewall is a solution to a particular problem that arises when you follow the consequences of Hawking's famous original observation about black holes: namely that they have entropy and thus temperature. I'll have to think more about how to explain the issues to you all, but basically firewall proponents think the Universe needs to completely thermalize anything infalling into a black hole as soon as it passes the event horizon. So when you pass this locally boring part of spacetime (that is only special when you look non-locally, i.e., when you notice that oh yes, there is a fucking enormous compact mass over there), you get hit by a wall of fire and get thermalized. Which seems problematic. But not doing this could also be problematic.

This is outside my expertise, and its a very volatile subject, so I'm not ready to give anything resembling a run-down of the topic and the pros and cons. I don't have any idea of what the right answer is, and extremely smart people come down on both sides of the issue. Hawkings solution is to say (it seems) that while we can think about an idealized black hole with a real event horizon, and thus firewall problems once you turn on quantum gravity, any actual black hole will have quantum fluctuations in the event horizon location that prevents the problem from being realized. At least, that appears to me to be what he is saying.

As for the peer-review thing, again, arXiv is a pre-print server. We in theoretical physics have a different attitude towards peer review than other sciences, namely, we are willing to put things out to the community before peer review because in principle we're all able to read a theory paper and decide on our own whether its correct, and we have strong career reasons not to look like fools in front of our colleagues. (Not that other scientists don't, just that theoretical physics is something you can do with a pencil and paper, no expensive lab required). arXiv evolved out of an informal mailing list of preprint papers that got circulated around to the Big Physics Departments before the Internet, and this online version is an infinitely better and more democratic process. Most papers on it eventually get peer reviewed by a journal, and the arXiv posting gets updated to reflect that (you can see on arXiv pages the version number, usually v2 or v3 is the post-peer reviewed, corrected version). Not every paper gets submitted to a journal. Some are talks written down or otherwise just not worth the trouble for the authors, some just never make it past the referee. We in the field usually can tell from context which papers are not submitted for good reasons, but it can be confusing for a science journalist or interested member of the public. It's not ideal, I realize, but arXiv is an amazing resource in general.

Anyway, Hawking is not the only Big Name in physics to have an opinion on the firewall issue. Polchinsky, Bousso, Banks, and nearly every other person who thinks a lot about the intersection of GR and QM has proposed ideas which break various long-held beliefs about how the Universe is to varying degrees. We don't know who, if anyone, is right, but it is tremendously exciting. Hawking is a name that people outside my community recognize, so his contribution gets special attention. That's fine, just remember you're looking at an area of active debate, not long-settled science, and at least one very smart person is going to be wrong in the end.
posted by physicsmatt at 6:13 PM on January 27 [27 favorites]


The scientific community, perhaps, but the media is all too willing to jump on unpublished, unreviewed stuff as long as it has a catchy hook -- witness the "Facebook will lose 80% of its users" boomlet last week.

The 80% thing also supports Hawking's redefinition of Black Holes.
posted by srboisvert at 6:59 PM on January 27


klangklangston: "Isn't this just an outgrowth of Hawking's encyclopedia bet, where he disavowed actual event horizons in favor of apparent horizons?"

So, you didn't read the article?
posted by IAmBroom at 7:11 PM on January 27


physicsmatt: "As for the peer-review thing, again, arXiv is a pre-print server. We in theoretical physics have a different attitude towards peer review than other sciences, namely, we are willing to put things out to the community before peer review because in principle we're all able to read a theory paper and decide on our own whether its correct, and we have strong career reasons not to look like fools in front of our colleagues. (Not that other scientists don't, just that theoretical physics is something you can do with a pencil and paper, no expensive lab required)."

I'd say another difference is: it's easier to bullshit (and even innocently misdirect) people in disciplines that are many-deep and many-wide, so peer-review is more important if one is reporting, say, about the unusual tibias of one species of tree frog, or how drug X interacts with protein Y in Z% of people tested.
posted by IAmBroom at 7:32 PM on January 27


Sequel: Apparent Horizon where Sam Neill only seems possessed by the devil, but is really just in need of psychiatric intervention.

This is a movie I want to see.
posted by Ray Walston, Luck Dragon at 7:45 PM on January 27 [1 favorite]


This is so not news.

Hawking is not only not the only physicist to have an opinion on the black hole issue, he is not the first person to say *any* of the things said in his only-2-page-long paper that contains no equations.

The worst part is *he* knows this. The controversy about firewalls that brought all of these things to the fore has been brewing for 1.5 or 10 years (depending on how you look at it). Hawking is aware of that, and his paper doesn't really make a claim otherwise.

The journalists, however, say "oh Hawking says it! Now it must be true!"
Blegh.
Science journalism is fucking atrocious.

(I am done ranting now and will not comment further in this thread in an effort to not raise my blood pressure).
posted by nat at 9:06 PM on January 27 [2 favorites]


"So, you didn't read the article?"

I read the ones above the fold. Do you have something to contribute?
posted by klangklangston at 9:27 PM on January 27


Damn! Now Event Horizon will seem so dated!

Are we ready for another Event Horizon, only with more impregnation?
posted by homunculus at 12:03 AM on January 28


just remember you're looking at an area of active debate, not long-settled science

THIS
IS
SCIENCE

/kicks physicsmatt into black hole
posted by obiwanwasabi at 1:56 AM on January 28 [4 favorites]


Science journalism is fucking atrocious.

Especially when the media outlet has an antiscience axe to grind:

"Stephen Hawking now says light and information may be able to escape from black holes, doing an about-face on the objects that helped cement his reputation."

In other words, "look at them scientists, even the most famous of the lot are like weathervanes" - oh sorry, I didn't mean to talk about weather.
posted by hat_eater at 4:10 AM on January 28 [5 favorites]


Rufus Sewell is in talks to star in Animus, a movie that's described as Event Horizon meets Alien, about an astronaut who gets an alien infection and then turns into the "ultimate alpha male" who "dominates and impregnates" all the women.

Um, this is neither Event Horizon nor Alien, it is Species 2. What the fuck, people.
posted by Steely-eyed Missile Man at 6:20 AM on January 28 [2 favorites]


So when you pass this locally boring part of spacetime (that is only special when you look non-locally, i.e., when you notice that oh yes, there is a fucking enormous compact mass over there), you get hit by a wall of fire and get thermalized. Which seems problematic. But not doing this could also be problematic.

I thought black hole complementarity resolved that?
posted by empath at 6:47 AM on January 28


Why does Stephen Hawking say black holes don't exist?

What would I do if I was Stephen Hawking?

Shit.

1. Make friends with Xzibit, and pimp out my wheelchair including hydraulics
2. Make all sorts of assertions with serious evidence.
3. Have other people assert them.
4. DESTROY 2 & 3.
5. Have this be my theme song while I move around on my wheelchair.

Students, they pay homage, but haters say Hawk fell off
How physicist, My last paper is still referenced
They want to know if he still got it
They say black holes changed, they want to know how I feel about it...

posted by hal_c_on at 10:10 AM on January 28


There's a lot of journalism about science-themed subjects. There's not a lot of science journalism.

I would echo physicsmatt's analysis of arXiv, although I don't think it takes much exposure to it to get a good feel for the status of entries - especially if you have a spin through looking at other papers in the same area as the one of interest. Journalists are - or should be - equipped with some fairly good filters for judging the quality of information, even if it's increasingly hard to act on them properly, and the combination of the Web as a whole and arXiv in particular provides plenty of clue if you're minded to go look.

This applies if you're not a journalist, but are interested enough to have spent some time informing yourself of an area of interest: if your motivation is self-education, rather than (say) finding stuff that bolsters a strongly-held opinion, you can't help but grow the right tentacles to pluck the good stuff out of the grunge.

In the case of this latest Hawkinalia, I have already set my Hawkin filter quite high - I don't really follow what he does or says, as his recent work hasn't scratched any particular itch - so only went to look after a couple of friends had asked me whether the media scrum was saying something important. My process then was:

1. Read MSM reports
2. Fail to understand MSM reports. Which means -
a: I'm missing something important, or
b: They don't understand what they're typing
3. Go and see what specialist blogs are saying - Aha! Now understand MSM reports. 2b applies.
4. Check original arXiv post, with context from 3.

At which point, I had an opinion I was fairly comfortable with - which didn't actually require understanding anything other than pop science levels of the issue in hand. I could go back to my pals and say - eh, well, it's mildly interesting but doesn't justify the profile, and if you want to get ready for Big Fun with Black Holes, pay attention to what's going on at galactic central.

And move on with life (currently refreshing what I know - very little - of the current state of thinking of the origins of cosmic rays).

This sort of filtering process, while fallible, does limit the amount of time I spend gnashing my teeth over MSM science reporting and gives me a good chance of sifting out those occasions where, yes, there's a good lead to something I'd like to know. It's a lot harder in other areas (medical research is one bugbear), so set your controls and be prepared to do more work accordingly.
posted by Devonian at 10:28 AM on January 28


Um, this is neither Event Horizon nor Alien, it is Species 2. What the fuck, people.

If there's lots of splatter, gore, and viscera of which next to none shows up in the trailer so unsuspecting sci-fi fans wander into it, it'll be EH.
posted by Pirate-Bartender-Zombie-Monkey at 10:39 AM on January 28


Yeah, he's real smart until Batman punches him out by proxy.
posted by Smedleyman at 11:33 AM on January 28


klangklangston: "I read the ones above the fold. Do you have something to contribute?"

Yes: read the links below the fold, too. Ordinarily I don't have the time to read the links for you, but since you're so damned busy, I guess I'll make an exception this time:

From the "black hole firewall paradox"link:

He and the Caltech physicist Kip Thorne even made a bet with a dubious Preskill in the 1990s about about whether or not information is lost in a black hole. Preskill insisted that information must be conserved; Hawking and Thorne believed that information would be lost. Physicists eventually realized that it is possible to preserve the information at a cost
...
Susskind’s argument that information could be recovered without resorting to quantum Xeroxing proved convincing enough that Hawking conceded his bet with Preskill in 2004, presenting the latter with a baseball encyclopedia from which, he said, “information can be retrieved at will.” But perhaps Thorne, who refused to concede, was right to be stubborn.

posted by IAmBroom at 12:28 PM on January 28


Not much of a contribution, then. Yes, the bet is referenced. And yes, this seems like an outgrowth of the position that Hawking took when conceding the bet, that event horizons are unworkable and apparent horizons are the solution.
posted by klangklangston at 1:15 PM on January 28


I thought black hole complementarity resolved that?

The so-called AMPS paper from 2012 discussed in the "black hole firewall paradox" link argues that the BHC claims of 1) unitarity; 2) "semi-classical" physics outside the event-horizon; and 3) an infalling observer not experiencing anything unusual; are inconsistent. (I won't attempt to explain why because I am definitely not a physicist and I can't follow their argument). (Also, in some slides from a presentation Polchinski gave last year he mentions a "strong complementarity" that might offer another solution, but says it is "not yet well-formulated").

I am trying to read the paper, though, and have questions for any actual physicists who might care to answer: What do they mean that Hawking radiation is "pure"? What do they mean by dividing it into "early" and "late" parts? It seems like a temporal division: "we... make the division after the Page time when the black hole has emitted half of its initial entropy" -- but then they say that the "purity" of the radiation implies that the early and late modes are fully entangled. This is a consequence of unitarity? ("an observer making measurements on the early radiation can know the number of photons that will be present in a given mode of the late radiation"). And where does the "firewall" actually come from? In the Scientific American article, Polchinski says, "if you lose the entanglement... it means you’ve put some kind of sharp kink into the quantum state right at the horizon. You’ve broken a bond, in some sense, and that broken bond requires energy." Does entanglement have an associated energy?
posted by junco at 11:03 PM on January 28 [1 favorite]


Stephen Hawking’s Blunder on Black Holes Shows Danger of Listening to Scientists, Says Bachmann

No, Stephen Hawking Did Not Say Black Holes Don't Exist
posted by homunculus at 4:22 PM on February 1 [2 favorites]


New Type of Star Emerges From Inside Black Holes: Born inside black holes, “Planck stars” could explain one of astrophysics’ biggest mysteries and may already have been observed by orbiting gamma ray telescopes, say cosmologists
posted by homunculus at 8:23 PM on February 6 [2 favorites]


Are We Living in a Black Hole? Our universe may reside within a vast, black hole.
posted by homunculus at 12:23 PM on February 19 [1 favorite]


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