# So...black holes don't exist now? **URL:** \ **Category:** Factual Questions\ **Created:** [September 24, 2014, 10:20pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470 "2014-09-24T22:20:15Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 25, 2014, 12:55pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/21 "2014-09-25T12:55:51Z")
> [@Knorf](#): > > It’s like a movie not being screened for critics: never a good sign. > > Also, many or maybe even most scientific papers, including those exhaustively peer-reviewed and vetted, turn out substantially or even entirely incorrect. > > This story has B.S. written all over it. > > We can safely continue accepting that black holes exist. I don’t really understand this view. The paper very clearly states that it is a numerical investigation of the hydrodynamic properties of a collapsing, inhomogeneous star. It’s a model and this model, assuming the math is consistent, shows that just before the Schwartzchild radius a “bounce” occurs which prevents a black hole from forming. So that’s fascinating, if it’s true. It says nothing about what we’ve seen in galactic cores that we’ve labelled black hole. There is something there and the effects are pretty clear. This simply says that the current collapse models need to be reconsidered and refined further. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [September 25, 2014, 1:03pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/22 "2014-09-25T13:03:11Z")
> [@KarlGauss](#): > > Just to be clear, both the paper in question and the comments above (i.e. **Grey** ’s quote), seem to be stating that Hawking Radiation is not emitted by a black hole _per se_ but, rather, arises from the intense gravitational field just outside the event horizon. Have I got that right? > > If so, does that imply that the detection of Hawking Radiation would not necessarily imply the existence of a black hole (i.e. it could come from any _very_ strong and compact gravitational field, and not just from a BH)? No, as I understand it Hawking radiation arises from the tearing apart of the particle-antiparticle pairs that arise out of quantum fluctuations and annihilating one but not the other – i.e.- removing it from the universe, so that the other becomes a real particle. This requires the companion to fall through an actual event horizon. > [@Mangetout](#): > > This sounds a whole lot like the ‘you weren’t there!’ argument that creationists are so fond of. Everything is ‘inference’. Everything. Yes, but a rather academic distinction. Some inferences are based on much more direct evidence than others and carry qualitatively different levels of confidence. The inference that the sun exists can be fairly said to be qualitatively different than the inference that a supermassive black hole exists at the center of our galaxy, so that in practical discussion the former is regarded as an observed certainty and not an inference. ---
**Author:** ![Grumman](https://avatars.discourse-cdn.com/v4/letter/g/43a26b/32.png) [@Grumman](https://boards.straightdope.com/u/Grumman)\ **Post date:** [September 25, 2014, 1:16pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/23 "2014-09-25T13:16:22Z")
> [@Habeed](#): > > I read [a paper](http://arxiv.org/pdf/0908.1803.pdf) on hypothetically forming an artificial black hole. The problem is that you must cram an incredible amount of mass-energy into the black hole before it is even stable enough that it won’t evaporate instantly. This makes creating an artificial one incredibly difficult. Were you to simply try to squeeze mass together, the moment it passes the threshold to become a black hole, hawking radiation is so intense that the black hole instantly evaporates. > > The proposed method that has a chance of working is to fire relativistic rods that have to total about 1 million tons of mass-energy. The rods slam into each other and create a compressed point of matter so dense that it won’t evaporate from hawking radiation. The problem is that there might not be enough mass in our solar system to build the apparatus needed to do this. Problem? I’d say that’s a good thing. I don’t really want the last words of humanity to be “Hey y’all, watch this!” > [@Grey](#): > > I don’t really understand this view. The paper very clearly states that it is a numerical investigation of the hydrodynamic properties of a collapsing, inhomogeneous star. It’s a model and this model, assuming the math is consistent, shows that just before the Schwartzchild radius a “bounce” occurs which prevents a black hole from forming. The view is not complex: _saying_ your numerical investigation shows X is not equal to your numerical investigation showing X. Peer review is meant to be an independent verification of this step, and choosing to bypass that independent verification and go straight to telling the ignorant masses that you’re right is not a good sign. ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 25, 2014, 1:33pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/24 "2014-09-25T13:33:27Z")
The original OP’s cite has only two quotes from the paper’s author. > [@](#): > > “I’m still not over the shock,” said Mersini-Houghton. “We’ve been studying this problem for a more than 50 years and this solution gives us a lot to think about.” > > “Physicists have been trying to merge these two theories – Einstein’s theory of gravity and quantum mechanics – for decades, but this scenario brings these two theories together, into harmony,” said Mersini-Houghton. “And that’s a big deal.” And just so people understand the current paper is a refinement of an early paper presented in the peer reviewed journal, Physics Letters B. That paper can be found here - [Backreaction of Hawking radiation on a gravitationally collapsing star I: Black holes? - ScienceDirect](http://www.sciencedirect.com/science/article/pii/S0370269314006686) So outside of the paper, the author doesn’t seem to cast her results as carved in stone, the paper is a refinement of a previously peer reviewed journal published article and the math, if consistent, seems to show that current stellar collapse models need to to be refined. Still not seeing how that isn’t science. ---
**Author:** ![Knorf](https://avatars.discourse-cdn.com/v4/letter/k/58956e/32.png) [@Knorf](https://boards.straightdope.com/u/Knorf)\ **Post date:** [September 25, 2014, 2:07pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/25 "2014-09-25T14:07:46Z")
> [@Grey](#): > > Still not seeing how that isn’t science. Who said it wasn’t science? ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 25, 2014, 2:13pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/26 "2014-09-25T14:13:41Z")
So, in this proposed theory, is most of the mass radiated away, leaving behind some remnant of the star? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 25, 2014, 2:27pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/27 "2014-09-25T14:27:04Z")
> [@Knorf](#): > > Who said it wasn’t science? > [@](#): > > In other words, it’s not Real Science ™ and the “It’s not peer reviewed” and “like a film without a prescreening” attitude I was originally replying to. Sure it might ultimately turn out to be missing key terms but that doesn’t mean it isn’t of value. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [September 25, 2014, 2:29pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/28 "2014-09-25T14:29:15Z")
> [@wolfpup](#): > > Yes, but a rather academic distinction. Some inferences are based on much more direct evidence than others and carry qualitatively different levels of confidence. The inference that the sun exists can be fairly said to be qualitatively different than the inference that a supermassive black hole exists at the center of our galaxy, so that in practical discussion the former is regarded as an observed certainty and not an inference. I don’t disagree that there are different levels of confidence (and differing degrees of inference), but at the same time, when someone talks about what we ‘see’, in the context of some distant astronomical object (or, for that matter, a subatomic particle or something else that is local, but not naked-eye visible), we don’t really need to nitpick them on the word ‘see’, do we? ---
**Author:** ![Grey](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Grey](https://boards.straightdope.com/u/Grey)\ **Post date:** [September 25, 2014, 2:54pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/29 "2014-09-25T14:54:38Z")
> [@cmyk](#): > > So, in this proposed theory, is most of the mass radiated away, leaving behind some remnant of the star? Careful, it isn’t a theory. What they did was combined an Einstein model of gravity (General Relativity) with a hydrodynamic model of the star. Fluid equations are typically right nasty bastards to solve so people do numeric modelling. This numeric model seems to show that as the other layers rush towards the Schwartzchild radius Hawking radiation peaks leading to a loss of mass preventing the collapse from passing through the Schwartzchild radius and becoming a black hole. Now, the model breaks down when the inner layers they’re modelling bounce back out. They crash through the outer layers still “falling” inwards and the numeric methods the’re using breakdown at that point. That leaves open the question of do these modelled stars just explode or evaporate away. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [September 25, 2014, 3:33pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/30 "2014-09-25T15:33:22Z")
> [@](#): > > We discover that the stars explode instead of collapsing to a black hole, as they get close to their last stage of collapse, just when Hawking radiation reaches a maximum, but they never cross what would have been the apparent horizon. I suspect that this is the problem right here. Apparent horizons are a lot easier to work with than actual ones, but there’s a reason they’re called “apparent”. If you cross an actual event horizon, you’re not “bouncing back”. And it’s long been known that it’s possible to cross an actual event horizon without ever encountering an apparent horizon. It may well be that a collapsing star never actually crosses an apparent horizon, either, and if so that would be an interesting result, but it would hardly be earthshaking. ---
**Author:** ![Exapno\_Mapcase](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/exapno_mapcase/32/1051_2.png) [@Exapno\_Mapcase](https://boards.straightdope.com/u/Exapno_Mapcase)\ **Post date:** [September 25, 2014, 3:33pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/31 "2014-09-25T15:33:51Z")
> [@njtt](#): > > The connotations of ‘seen’ and ‘“inferred” from certain measurements (very likely manifest as a numerical printout), via a lot of theory and some quite complex math’ are vastly different. ‘Seen’ implies that there is really no room for any doubt about it, and opinions are most unlikely ever to change. What I said brings out the reality that there is actually enormous scope for reasonable doubt on all sorts of grounds, and opinions are quite likely to change. > > No, nobody has ever _seen_ black holes at the center of galaxies. What have been considered our best theories, up until now, _imply_ that they should be there, but what are considered our best theories changes all the time, and the whole point of this thread is that the theories relevant to black holes may be in the process of changing right now. Physicists are practical people. Although the extremes they explore raise numerous philosophical issues, my understanding is that the vast majority of them take the attitude “shut up and do the science.” The current consensus (again, in my understanding) is that the objects detected in the centers of many, many galaxies are black holes because that answer is far better than any other answer that was postulated. If black holes can’t exist, then either one of the other rejected and inferior answers must be reconsidered or a wholly new explanation must be invented. That’s a huge deal. It’s such a huge deal that it alone casts doubt on the statement. Other scientists are saying that she fails to consider some important issues. Maybe her math only goes a portion of the way. We do think we “see” black holes because what our instruments do in fact record at a variety of wavelengths make a picture that seems to be answerable only by a black hole. This isn’t a Creationist thread where the basic nature of science has to be explained. If what we see as a black hole isn’t a black hole is a legitimate question that doesn’t really require any parsing. ---
**Author:** ![cmyk](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cmyk/32/3353_2.png) [@cmyk](https://boards.straightdope.com/u/cmyk)\ **Post date:** [September 25, 2014, 4:03pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/32 "2014-09-25T16:03:30Z")
> [@Chronos](#): > > I suspect that this is the problem right here. Apparent horizons are a lot easier to work with than actual ones, but there’s a reason they’re called “apparent”. If you cross an actual event horizon, you’re not “bouncing back”. And it’s long been known that it’s possible to cross an actual event horizon without ever encountering an apparent horizon. It may well be that a collapsing star never actually crosses an apparent horizon, either, and if so that would be an interesting result, but it would hardly be earthshaking. I’m very skeptical about what’s being claimed. As one of this board’s de facto astrophysicists, can you weigh in, by fact or opinion, on this model? ---
**Author:** ![eschereal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/eschereal/32/18939_2.png) [@eschereal](https://boards.straightdope.com/u/eschereal)\ **Post date:** [September 25, 2014, 4:30pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/33 "2014-09-25T16:30:53Z")
Perhaps what we observe is the ongoing process of catastrophic stellar collapse, not the result? At the event horizon, time dilation is so extreme that for practical purposes, time stops wrt our frame of reference. So black holes could always fail to form, but they would take such a long time, for the distant observer, between collapse and bounce-back that we could never actually hope to see the explosion that rips them apart. In other words, black holes may be a physical impossibility, but in real-world terms, we might as well proceed as though they actually exist. There are just no actual singularities or regions where the laws of physics fail. ---
**Author:** ![Topologist](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/topologist/32/3208_2.png) [@Topologist](https://boards.straightdope.com/u/Topologist)\ **Post date:** [September 25, 2014, 5:20pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/34 "2014-09-25T17:20:39Z")
> [@robert\_columbia](#): > > It’s not being published in a peer reviewed journal, or even being presented at a legit conference. In other words, it’s not Real Science ™. I’m a mathematician, not a physicist, so I won’t comment on the paper itself, but I want to correct a misunderstanding of the arXiv. Posting something to the arXiv is not meant to be considered publication or replace publication – it’s a preprint archive. It replaces what we used to do, mailing pre-publication versions of our papers to all our friends and colleagues to get their comments and suggestions. It allows updated versions to be posted and also allows you to note eventually where the final version got published, if it was good enough to pass peer review. Not incidentally, it also allows you to publicly establish priority while your work is being discussed. Passing around pre-publication work has always been part of math and science and the arXiv is just a way of facilitating it. What’s premature and unfortunate, perhaps, is the attendant press release. ---
**Author:** ![halfreal](https://avatars.discourse-cdn.com/v4/letter/h/ccd318/32.png) [@halfreal](https://boards.straightdope.com/u/halfreal)\ **Post date:** [September 25, 2014, 5:23pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/35 "2014-09-25T17:23:02Z")
I can’t claim any educational basis for an opinion on my part, but my BS detector suggests to go with this response from the article I linked to above ([Physicist Claims to Have Proven Mathematically That Black Holes Do Not Exist | IFLScience](http://www.iflscience.com/physics/physicist-claims-have-proven-mathematically-black-holes-do-not-exist) ) : > [@](#): > > “The [paper] is nonsense,” Unruh said in an email to IFLS. “Attempts like this to show that black holes never form have a very long history, and this is only the latest. They all misunderstand Hawking radiation, and assume that matter behaves in ways that are completely implausible.” > > According to Unruh, black holes don’t emit enough Hawking radiation to shrink the mass of the black hole down to where Mersini-Houghton claims in a timely manner. Instead, “it would take 10^53 (1 followed by 53 zeros) times the age of the universe to evaporate,” he explains. > > “The standard behaviour by such people [who don’t understand Hawking radiation] is to project that outgoing energy back closer and closer to the horizon of the black hole, where its energy density gets larger and larger,” he continued. “Unfortunately explicit calculations of the energy density near the horizon show it is really, really small instead of being large-- Those calculations were already done in the 1970s. To call bad speculation “has been proven mathematically” is, shall we say, and overstatement.” ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [September 25, 2014, 5:28pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/36 "2014-09-25T17:28:46Z")
> [@Chronos](#): > > I suspect that this is the problem right here. Apparent horizons are a lot easier to work with than actual ones, but there’s a reason they’re called “apparent”. If you cross an actual event horizon, you’re not “bouncing back”. And it’s long been known that it’s possible to cross an actual event horizon without ever encountering an apparent horizon. It may well be that a collapsing star never actually crosses an apparent horizon, either, and if so that would be an interesting result, but it would hardly be earthshaking. The quoted statement is what doesn’t square for me though: an apparent horizon is a necessary condition for Hawking radiation ---
**Author:** ![Yumblie](https://avatars.discourse-cdn.com/v4/letter/y/76d3ee/32.png) [@Yumblie](https://boards.straightdope.com/u/Yumblie)\ **Post date:** [September 25, 2014, 5:39pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/37 "2014-09-25T17:39:17Z")
> [@njtt](#): > > The connotations of ‘seen’ and ‘“inferred” from certain measurements (very likely manifest as a numerical printout), via a lot of theory and some quite complex math’ are vastly different. ‘Seen’ implies that there is really no room for any doubt about it, and opinions are most unlikely ever to change. What I said brings out the reality that there is actually enormous scope for reasonable doubt on all sorts of grounds, and opinions are quite likely to change. > > No, nobody has ever _seen_ black holes at the center of galaxies. What have been considered our best theories, up until now, _imply_ that they should be there, but what are considered our best theories changes all the time, and the whole point of this thread is that the theories relevant to black holes may be in the process of changing right now. [This](https://www.youtube.com/watch?feature=player_detailpage&v=MDrY4g522q8#t=189) is probably the closest we’ll get to “seeing” black holes in the near future. It pretty conclusively shows that there exists something that is very 1) massive, 2) small, and 3) dim. I don’t know of anything that would fit those criteria other than a black hole. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [September 25, 2014, 5:40pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/38 "2014-09-25T17:40:51Z")
[Comment about time dilation and the Hawking radiation already addressed above] ---
**Author:** ![rsa](https://avatars.discourse-cdn.com/v4/letter/r/839c29/32.png) [@rsa](https://boards.straightdope.com/u/rsa)\ **Post date:** [September 26, 2014, 3:33am UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/39 "2014-09-26T03:33:35Z")
> [@Topologist](#): > > I’m a mathematician, not a physicist, so I won’t comment on the paper itself, but I want to correct a misunderstanding of the arXiv… Speaking of the arXiv, are there any interesting stories about the origin of [xxx.lanl.gov](http://xxx.lanl.gov/) and why Cornell ended up with it as an alias for [lanl.arXiv.org](http://lanl.arXiv.org) while the Los Alamos National Labortory had to settle for [www.lanl.gov](http://www.lanl.gov/)? My guess is that some Republican made a stink about government money being spent on pornographic science research. 🙂 Sorry about the off-topic question. ---
**Author:** ![Half\_Man\_Half\_Wit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/half_man_half_wit/32/21766_2.png) [@Half\_Man\_Half\_Wit](https://boards.straightdope.com/u/Half_Man_Half_Wit)\ **Post date:** [September 26, 2014, 4:02pm UTC](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470/40 "2014-09-26T16:02:05Z")
Just some quick points before I have to dash out: [ol] [li]No, this doesn’t show black holes don’t exist. Even if correct, it only shows that they can’t be formed via stellar gravitational collapse, but there are other plausible ways of producing them.[/li][li]No, this isn’t a unification of general relativity and quantum mechanics. If everything holds up, it’s a significant achievement in doing quantum mechanics on a dynamic general relativistic background, much like Hawking’s original calculation was a significant achievement in doing quantum mechanics in curved spacetime.[/li][li]Yes, it’s serious science—publication on the arXiv, as **Topologist** above notes, is part of the usual procedure of producing papers in physics these days. Still, it would have been preferable to wait for peer review.[/li][li]Finally, there’s good reason to be sceptical of the result (there’s good reason to be sceptical of basically any result that tries to overthrow decades of scientific thought with a single blow—sure, those things turn out right sometimes, and when they do, it’s the most exciting thing that can happen in science, but they turn out right exceedingly rarely). Many other physicists, such as Bill Unruh quoted above, or [Sabine Hossenfelder on her blog](http://backreaction.blogspot.de/2014/09/black-holes-declared-non-existent-again.html), have pointed to some at least questionable details of the derivation.[/li][/ol] [Previous page](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470.md?page=1) [Next page](https://boards.straightdope.com/t/so-black-holes-dont-exist-now/699470.md?page=3)