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Space Science

No Naked Black Holes 317

Posted by kdawson
from the also-no-hair dept.
Science News reports on a paper to be published in Physical Review Letters in which an international team of researchers describes their computer simulation of the most violent collision imaginable: two black holes colliding head-on at nearly light-speed. Even in this extreme scenario, Roger Penrose's weak cosmic censorship hypothesis seems to hold — the resulting black hole (after the gravitational waves have died down) retains its event horizon. "Mathematically, 'naked' singularities, or those without event horizons, can exist, but physicists wouldn't know what to make of them. All known mechanisms for the formation of singularities also create an event horizon, and Penrose conjectured that there must be some physical principle — a 'cosmic censor' — that forbids singularity nakedness ..."
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No Naked Black Holes

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  • by suso (153703) * on Monday October 06, 2008 @12:19AM (#25269755) Homepage Journal

    Oh jeez.

  • They're all Greek to me.
    • by MrKaos (858439)
      Are you serious, Offtopic!!!!! doesn't anyone get that joke. duuuuhhhhhhhhhh!
      • by bsDaemon (87307)

        Isn't Kaos Greek? Then, you would be able to understand the equations. I get it, I just don't have mod points.

        • Re: (Score:2, Funny)

          by weetabeex (1065032)
          I don't. But then again, I fail to understand most of what's going on at slashdot most of the time...
  • by bonch (38532) on Monday October 06, 2008 @12:31AM (#25269821)

    Does anyone else get sad at the thought that there are so many weird things in the universe you may not learn the answers to in your lifetime? What if everyone posting here never finds out the reason for the cosmic censor? Sort of depressing.

    • Or you could look at the bright side and celebrate all the things we know, instead of living in the darkness of 3,000 years ago.

      Or, if you want to go new age, just have "faith" in the singularity, life extension, cryonics and postulate that the probability is that you'll be immortal.
    • by fortunato (106228) on Monday October 06, 2008 @02:08AM (#25270225)

      Does anyone else get sad at the thought that there are so many weird things in the universe you may not learn the answers to in your lifetime?

      I would submit that this is the lament of every intelligent being since the dawn of time (assuming there is a dawn of time).

      • by Skazz11 (1035412) on Monday October 06, 2008 @06:33AM (#25271207)

        Having the massive intellect to comprehend the answers to all these questions does not make one less depressed.

        Marvin.

      • Re: (Score:3, Funny)

        by 10am-bedtime (11106)

        Does anyone else get sad at the thought that there are so many weird things in the universe you may not learn the answers to in your lifetime?

        I would submit that this is the lament of every intelligent being since the dawn of time (assuming there is a dawn of time).

        I get sad assuming there be intelligent beings about. Oh well...

      • by sznupi (719324)

        It got harder for us not that long ago...when we realised there's apparently nothing fundamental that would stop technological progress to the point allowing indefinite life extension.

        But we're not sure at all if we'll see those days.

        • by HuguesT (84078)

          Nothing fundamental as far as we know, but we are not there yet (as far as I know, at leat :-)

        • Indeed. My father made some passing comments about my generation being the one which would see "indefinite life extension" which (unsurprisingly perhaps) got lodged in my mind. Recently I realised it's still probably a long way off and having to readjust a rather large assumption I hadn't realised I'd made.... :(

    • Re: (Score:2, Interesting)

      by XSpud (801834)
      But imagine we knew everything about the universe. No more Hubble telescopes, an end to space exploration, nothing to hypothesize, dream about and discuss outside our known cosmic knowledge. I would find _that_ depressing.
    • by mcgrew (92797) * on Monday October 06, 2008 @09:17AM (#25272211) Homepage Journal
      Not the least. If I knew everything, I would no longer have the joy of learning.
  • by aussie_a (778472) on Monday October 06, 2008 @12:32AM (#25269827) Journal

    Penrose conjectured that there must be some physical principle â" a 'cosmic censor' â" that forbids singularity nakedness...

    God, is that you?

  • by unassimilatible (225662) on Monday October 06, 2008 @12:34AM (#25269837) Journal
    Seems to me, most people on Slashdot likely *only* experience singularity nakedness.
  • by Flentil (765056) on Monday October 06, 2008 @12:35AM (#25269847) Homepage
    If photonst have weight, they can be effected by gravity, and a black hole can form around any object with sufficient mass to trap light. That's all there is to it. There is no magical singularity where the laws of physics break down. There doesn't need to be.
    • Re: (Score:2, Funny)

      There is no magical singularity where the laws of physics break down. There doesn't need to be.

      Whatever helps you sleep at night, dude.

      • Re: (Score:3, Interesting)

        by Hurricane78 (562437)

        He's right tough.

        Just because we can't look inside, doesn't mean that everything breaks down inside.

        People often see a black hole as something magical, and think, the Schwarzschild radius is some magical wall.
        It's just the distance, at which gravitation is stronger than everything else, so we can't get useful information from the inside. Although maybe with entangled particle-pairs we could get information out!)

        About the inside we know nothing. It's not the physics that break down. It's the formulas and the

        • by Kandenshi (832555) on Monday October 06, 2008 @02:03AM (#25270203)

          If I'm recalling correctly Hawking addressed that issue in Brief(Briefer?) History of Time. He explained that for small black holes the difference in how strongly gravity is pulling one end of you(feet) compared to the other end(head) would tear you apart before you could reach the event horizon. Large black holes (on the order of millions of stellar masses, like the ones at the center of galaxies) would be a much more gentle ride intially. In fact he said, you could pass right through the event horizon and not notice anything particularly weird happening. You wouldn't even notice. Nevertheless as you get closer to the singularity at the center you'd still get ripped apart.

          • by paul248 (536459)
            But time is moving slower inside the black hole than outside. Wouldn't you get a helluva sunburn from all the radiation ever to hit the black hole over the remaining life of the universe?
            • Re: (Score:3, Interesting)

              by QuantumPion (805098)

              Time is only moving slowly as viewed by an outside observer. An observer would see you take an infinite amount of time to cross the event horizon. But from your point of view, time continues on as normal.

              As you cross the event horizon you wouldn't notice anything unusual, you would still see the outside universe behind you and the event horizon would still appear in front of you. In fact, from your own point of view, you would never reach the event horizon, it always appears in front of you at the same dist

              • Re: (Score:3, Interesting)

                by Hurricane78 (562437)

                No, GP is right. Your time would pass normal for you, but the time of everything outside the black hole would pass faster and faster, meaning you'd get more and more radiation and faster and faster star movement, until the sky is completely white. But I guess you'd be dead by then.

        • by uberdilligaff (988232) on Monday October 06, 2008 @06:58AM (#25271311)
          Remarkably well said.

          A black hole isn't some mystical thing unrelated to the other cosmological objects. Black holes are just stars that have consumed most of their fuel through fusion over billions of years, then collapsed. But consumed doesn't mean the mass is all 'burned up' and gone, but converted from hydrogen and helium into heavier elements that are harder to participate in further fusion reactions, resulting in decreasing internal pressure from energy being released by the star. If the conditions are right, the compacting force of gravity from all the 'star stuff' that's left exceeds the declining expansive pressure provided by the fizzling nuclear reactions inside the star, and it ultimately collapses into an incredibly small size. If the size is less than the Schwarzschild radius, it will become a black hole.

          But it's still just a lump of star stuff with mass like what the star had, but in a dramatically smaller package. It doesn't suddenly go on a cosmic rampage, marauding around and sucking up everything in sight. If something external has sufficient distance and velocity that it would have flown by or orbited the former star, then it will fly by or orbit the hole, as these parameters are solely determined by the masses of the star/hole and the external thing. If something would have fallen into the star, it will fall into the hole as well. Whether it falls into a black hole or a star, it's not coming back out.

          Astronomers infer the properties of black holes from what they can observe about the objects that are influenced by them, and from what they observe about the progression of stars throughout their lifetimes. Just because we can't see into black holes doesn't mean they are totally mysterious.
          • Re: (Score:2, Interesting)

            by hobbit (5915)

            But it's still just a lump of star stuff with mass like what the star had

            Is there any theoretical limit to the formation of new elements? Might there exist, in large black holes, ones with atomic numbers in the thousands? Are we sure that they will continue to behave according to the laws of physics as we know them?

            These are not rhetorical questions -- I'm genuinely interested.

            • Re: (Score:2, Informative)

              by Mr. Slippery (47854)

              Might there exist, in large black holes, ones with atomic numbers in the thousands?

              IANAA (I am not an astrophysicist) but IIRC before a collapsing star gets to the black hole stage it would (however briefly) go through a point where gravity was sufficient to collapse atoms - a neutron star. So I don't think there are any atoms in such a black hole. (Of course, that's theory, no one has made the observation to check!)

              However, not all black holes from from stellar collapse. I have no idea what the theory

    • by earlymon (1116185) on Monday October 06, 2008 @02:54AM (#25270403) Homepage Journal

      Photons have no mass but do have momentum.

      The Lorentz transform causes a breakdown for E in E=mc^2/sqrt(1-v^2/c^2) where v=c. And when you have enough gravity to bend space such that it folds in on itself - light cannot escape, despite being massless but gaining momentum from the gravity well - you have a singularity.

      One can't just say that equations break down, but physics do not. The equations are the language used to express the known physics.

      So, there is a singularity, there needs to be, and it isn't magical - unless you mean magical in the sense of wonderful.

    • Re: (Score:3, Funny)

      by iwein (561027)
      If photonst have weight

      That would cause some other hairy problems, spelling being the least of them.

    • by HuguesT (84078)

      1- Photons have no rest mass but they have energy and momentum (or relativistic mass). They are affected by gravity as they follow geodesics in spacetime, which are defined by the local mass-energy.

      They original experimental proof of general relativity was by Eddington who showed that the mass of the Sun bends light in the way predicted by GR.

      2- Mass by itself is not sufficient to "trap" light. A given mass contained within a given volume is, however, i.e a given density. A sufficient density creates an eve

    • by mikael (484)

      Photons don't have mass, otherwise they would never be able to travel at the speed of light- the energies required would be way too much.

      "Pair production" [wikipedia.org] is strange though. Fire a high energy photon (at gamma wave energies) at a heavy nucleus (say plutonium), and the photon splits into an electron and positron.

    • Re: (Score:3, Informative)

      First I'll correct your spelling by removing the spurious t from photons.

      Then there is the miss-use of the term black hole, at least according to my concept. From what you wrote, the proper term s/b "event horizon". You can see anything on this side of it, but whats inside it cannot be seen since the horizon diameter is in fact the distance from this object where the escape velocity equals C.

      Now here is a conjecture for you, an expansion of your idea if you will.

      Assume a large mass, whose gravity is so st

  • by Tau Neutrino (76206) on Monday October 06, 2008 @12:37AM (#25269853)
    ...the maximal Cauchy development of generic compact or asymptotically flat initial data is locally inextendible as a regular Lorentzian manifold.

    Right?
  • Non-Condradiction (Score:5, Interesting)

    by Toonol (1057698) on Monday October 06, 2008 @12:42AM (#25269879)
    Quantum physics was baffling to me (still is, actually), but I eventually came to see it as a way that nature avoided some inherent paradoxes and contradictions that were present when you took classic physics down to the level of fundamental particles. I have no doubt that, on a larger scale, the same principle applies: Somehow, someway, the laws of physics will always resolve with no singularities, no contradictions, no divide-by-zero-error, no infinities. If our formulas seem to indicate that one will be found, I suspect our understanding is incomplete.
  • by fahrbot-bot (874524) on Monday October 06, 2008 @01:22AM (#25270021)

    Penrose conjectured that there must be some physical principle -- a 'cosmic censor' -- that forbids singularity nakedness...

    Which is why the DVDs "Physicists Gone Wild" were never really successful. Although the LHC did turn up as the hottest collider in Europe, so far still no naked singularities.

  • Confucius say "Physicist who say there is no naked singularity should examine their equations through a peep hole."

  • Shhh (Score:4, Funny)

    by caspy7 (117545) on Monday October 06, 2008 @01:49AM (#25270139)

    You had me at naked...

  • I can't get over this sort of story. "We programmed our INCOMPLETE understanding of the cosmos into this simulation, which tells us X, therefore X is more likely."

    Anything based on a computer simulation is based on our arbitrarily incomplete knowledge. To base even the least significant conclusions upon it seems laughably irresponsible and unscientific.

    But hey, I was a music major, so what do I know.

    • by D.A. Zollinger (549301) on Monday October 06, 2008 @02:35AM (#25270335) Homepage Journal

      A few years ago, I might have agreed with you. After all, on a basic level you are correct, if we program what we know into a simulation, the simulation will be based on what we know!

      Last semester I took a class in complex system, and it really opened my eyes about what computer simulations can do for us in providing unexpected behavior. Most of this is because we have a pretty good grasp on simple systems, and can take those simple systems and program them into a computer with rules of interaction to see how they will interact without human guidance.

      Let me give you an example: Most everyone here at one point of time or another have programed "Life [wikipedia.org]" into a computer. We understand the rules, we understand the program itself, and we understand how everything is going to work, but until you actually run the program, you would never have expected the results! How could you have predicted the formations that would develop? The stable formations, the chaotic formations, the moving formations? Much less how these formations would interact when they collide?

      I think in a way this is what was being simulated in the program mentioned above. We think we have a pretty good idea about the simple systems which make up a complex entity like a black hole. But how do these simple systems interact when they encroach upon another black hole? Assuming we really do understand these simple systems, and that they stay constant, I think this simulation gives us a reasonable expectation as to how black holes will react to a collision.

    • by Ihlosi (895663) on Monday October 06, 2008 @03:33AM (#25270547)

      Anything based on a computer simulation is based on our arbitrarily incomplete knowledge. To base even the least significant conclusions upon it seems laughably irresponsible and unscientific.

      We eagerly await your analytical solution to the n-body-problem. I mean, it's really simple stuff, right?

      Until you're finished, we'll have to calculate all those spacecraft trajectories with computer simulations.

  • by supernova_hq (1014429) on Monday October 06, 2008 @02:39AM (#25270353)

    ...the most violent collision imaginable: two black holes colliding head-on at nearly light-speed.

    What about 3 black holes colliding head-on at nearly light-speed?

    • The author just lacks imagination.

    • Because there aren't three black hole colliding - there are two black holes colliding and then a third one colliding into the result. Remember they are travelling at the almost speed of light so the collision won't take very long.

    • Re: (Score:3, Insightful)

      by Loibisch (964797)

      You probably need to get yourself an extra few dimensions to make 3 particles collide exactly head-on.

  • Since the most common model for the creation of a naked singularity involves a rapidly spinning black hole, I fail to understand why there should be any expectation that colliding two black holes head-on would have that effect. This sounds like pseudo-science... "look, something that wasn't expected to create a naked singularity doesn't seem to do that in a simulation, so they can't exist!"

  • by LingNoi (1066278) on Monday October 06, 2008 @08:50AM (#25271949)

    Perhaps someone could educate me here but how accurate is this because surely we've never done any study into the effects of gravity at the speed of light. Doesn't gravity act differently at this speed?

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