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posted by janrinok on Sunday June 01 2014, @02:59PM   Printer-friendly
from the it-keeps-getting-more-complicated dept.

Zilong Li and Cosimo Bambi with Fudan University in Shanghai have come up with a very novel idea--those black holes that are believed to exist at the center of a lot of galaxies, may instead by wormholes. They've written a paper [abstract], uploaded to the preprint server arXiv, describing their idea and how what they've imagined could be proved right (or wrong) by a new instrument soon to be added to an observatory in Chile.

From the article:

Back in 1974, space scientists discovered Sagittarius A* (SgrA*) - bright source of radio waves emanating from what appeared to be near the center of the Milky Way galaxy. Subsequent study of the object led scientists to believe that it was (and is) a black hole - the behavior of stars nearby, for example, suggested it was something massive and extremely dense.

What we're able to see when we look at SgrA* are plasma gasses near the event horizon, not the object itself as light cannot escape. That should be true for wormholes too, of course, which have also been theorized to exist by the Theory of General Relativity. Einstein even noted the possibility of their existence. Unfortunately, no one has ever come close to proving the existence of wormholes, which are believed to be channels between different parts of the universe, or even between two universes in multi-universe theories. In their paper, Li and Bambi suggest that there is compelling evidence suggesting that many of the objects we believe to be black holes at the center of galaxies, may in fact be wormholes.

Plasma gases orbiting a black hole versus a wormhole should look different to us, the pair suggest, because wormholes should be a lot smaller. Plus, the presence of wormholes would help explain how it is that even new galaxies have what are now believed to be black holes - such large black holes would presumably take a long time to become so large, so how can they exist in a new galaxy? They can't Li and Bambi conclude, instead those objects are actually wormholes, which theory suggests could spring up in an instant, and would have, following the Big Bang.

Related Stories

Gravitational Fields Around Black Holes Might Eddy and Swirl 9 comments

We started this month with a story about how Black Holes at Center of Galaxies Might Instead be Wormholes. Now, an article out on Phys.org proposes Gravitational Fields Around Black Holes Might Eddy and Swirl.

From the article:

The team decided to study fast-spinning black holes, because a fluid-dynamics description of such holes hints that the spacetime around them is less viscous than the spacetime around other kinds of black holes. Low viscosity increases the chance of turbulence -- think of the way water is more swirly than molasses.

The team also decided to study non-linear perturbations of the black holes. Gravitational systems are rarely analyzed at this level of detail, as the equations are fiendishly complex. But, knowing that turbulence is fundamentally non-linear, the team decided a non-linear perturbation analysis was exactly what was called for.

They were stunned when their analysis showed that spacetime did become turbulent.

There is a related article, also on Phys.org, spacetime could be like a very slippery superfluid which notes:

In this sense, general relativity would be the analogue to fluid hydrodynamics, which describes the behaviour of fluids at a macroscopic level but tells us nothing about the atoms/molecules that compose them. Likewise, according to some models, general relativity says nothing about the "atoms" that make up spacetime but describes the dynamics of spacetime as if it were a "classical" object. Spacetime would therefore be a phenomenon "emerging" from more fundamental constituents, just as water is what we perceive of the mass of H2O molecules that form it.

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  • (Score: 3) by yellowantphil on Sunday June 01 2014, @03:36PM

    by yellowantphil (2125) on Sunday June 01 2014, @03:36PM (#49920) Homepage

    The phys.org article didn't mention where the authors thought the wormholes might go, so I checked the abstract on arxiv.org. It turns out that they have no idea:

    The supermassive black hole candidates at the center of every normal galaxy might be wormholes created in the early Universe and connecting either two different regions of our Universe or two different universes in a Multiverse model.

    I would imagine that the wormholes would lead to other wormholes in the the centers of other galaxies, whether those galaxies are in our universe or a different one. But I suppose that one of the wormholes could lead to a space station populated by beings that look strangely like humans.

  • (Score: 5, Interesting) by geb on Sunday June 01 2014, @03:46PM

    by geb (529) on Sunday June 01 2014, @03:46PM (#49923)

    This is one thing that science fiction almost always shows badly. A wormhole is not a shimmery magical door, or a swirly tear in spacetime. If you're looking at the input side of it, a wormhole looks pretty much exactly like a black hole. A wormhole is a black hole that goes somewhere. A black hole is a wormhole without the other side. A wormhole is not a friendly thing that you can keep locked up inside your spaceship and turn on when required.

    I would bet that they don't find any evidence of stable natural wormholes. A stable wormhole needs negative gravitation to prevent it from collapsing, and negative mass allows you to do all sorts of silly causality-breaking things. If you mix negative mass with frame dragging, as in a Tipler cylinder, you can do time travel maneuvres that the many worlds hypothesis can't save you from.

    • (Score: 4, Interesting) by maxwell demon on Sunday June 01 2014, @06:03PM

      by maxwell demon (1608) Subscriber Badge on Sunday June 01 2014, @06:03PM (#49948) Journal

      A stable wormhole needs negative gravitation to prevent it from collapsing, and negative mass allows you to do all sorts of silly causality-breaking things.

      Given that wormholes by themselves allow you to do all sorts of silly causality breaking things, the fact that you need something else allowing such things is not that bad. Indeed, one could even consider it consistent: To enable something you can use to break causality (wormholes), you need something you can use to break causality (a material with negative energy density).

      BTW, doesn't dark energy give negative gravitation (as it accelerates the expansion, I'd say it does)? Has anyone ever calculated the effect of dark energy on potential wormholes?

      --
      The Tao of math: The numbers you can count are not the real numbers.
      • (Score: 2, Interesting) by Anonymous Coward on Sunday June 01 2014, @06:28PM

        by Anonymous Coward on Sunday June 01 2014, @06:28PM (#49959)

        Yes. The statement that you need negative mass is not, strictly speaking, accurate. You need a negative gravitational charge, which is mass + 3 * pressure * c^2. So to get something that has a negative gravitational effect, you have to violate the "weak energy condition", which is rho + 3*p*c^2 >= 0. Violating this gives you p -rho, and once you start violating *this* then you end up riddled with problems of causality the likes of which make wormholes' own violations pale into insignificance. A dark energy like this is known as "phantom" and would lead to a "big rip", at which point you're more or less concerned about the rate at which the universe is accelerating its expansion and not so concerned about throwing yourself into a black hole in the hopes that it contains a wormhole.

        • (Score: 3, Interesting) by maxwell demon on Sunday June 01 2014, @06:55PM

          by maxwell demon (1608) Subscriber Badge on Sunday June 01 2014, @06:55PM (#49966) Journal

          But I think that assumes a dark energy density which is constant throughout the universe (cosmological-constant like). But given that we have no clue what dark energy actually is we can't be sure about that (sure, in the universe at large it seems to be evenly distributed, but then, the universe at large is itself quite homogeneous; we don't know what happens with it under extreme conditions, for example in wormholes).

          BTW, how does the Higgs field react to wormhole curvature? I seem to remember that it is or was considered as a candidate for early inflation, so it obviously has the potential to generate negative gravitation under the right conditions.

          --
          The Tao of math: The numbers you can count are not the real numbers.
          • (Score: 2, Interesting) by Anonymous Coward on Sunday June 01 2014, @07:27PM

            by Anonymous Coward on Sunday June 01 2014, @07:27PM (#49971)

            Slow-roll does, certainly, but that Laplacian encodes the spatial gradients -- it's g_{\mu\nu}\nabla^\mu\nabla^\nu, or (1/\sqrt{-g})*(d/dx^\mu)(\sqrt{-g}(d/dx^\nu)). Though certainly I might have got it wrong the gradients are there. The actual form I wrote it in though, yes, that's written in a coordinate system that wouldn't make much sense in the vicinity of a black hole, though you could always swap to a set of coordinates where you could write it like that locally.

            We could certainly model what happens in extreme conditions, such as in some kind of hypercircular strut inside a wormhole. The gradients there will definitely muck it up, you're right, but that doesn't necessarily mean it can't be configured such that you still get a repulsive effect. Of course, it *might*. I'm not aware of anyone who's actually done the calculation.

            Likewise I have no idea how the Higgs acts near the singularity of a hole (which is what the inside of a wormhole would look like -- basically two holes connect and instead of a singularity you have a kind of hypertube which is the Einstein-Rosen bridge, but without something with negative rho+3p you're going to find the bridge closing in front of you, a bit like a gruesome version of Xeno's paradox.) That's a really good question. I suspect that you won't be able to get it moving slowly enough in its own potential, and since it interacts by definition with everything in sight it's probably quite agitated inside a hole. But frankly a realistic calculation would be so tricky, accounting for the backreaction of the Higgs itself on the hole for instance, that it's probably not been done - it would be interesting to see. In its extreme it would probably look like a Schwarzschild-de Sitter which is a black hole in a spacetime with a non-zero cosmological constant.

    • (Score: 2) by rts008 on Monday June 02 2014, @12:12AM

      by rts008 (3001) on Monday June 02 2014, @12:12AM (#50038)

      A wormhole is not a shimmery magical door, or a swirly tear in spacetime. If you're looking at the input side of it, a wormhole looks pretty much exactly like a black hole. A wormhole is a black hole that goes somewhere. A black hole is a wormhole without the other side.

      I have to ask where the info you are presenting here is coming from?
      IIRC, all of that is still in the hypothesis and theory stage.

      When did we send probes or astronauts into wormholes and black holes...and get data/information back out? If we did, it is news to me!!
      And when did this occur and who did this wonderous thing that should be the news of the century? (all I see is this article proposing a hypothesis on wormholes possible existence)

      I don't think you need Hollywood's astrophysics expertise, you seem quite imaginative enough on your own.

      • (Score: 2) by geb on Monday June 02 2014, @08:04AM

        by geb (529) on Monday June 02 2014, @08:04AM (#50118)

        Wormholes are one class of solutions to the equations of general relativity. That is where the idea originally came from. That is where our descriptions of them are derived from. Even though they probably don't exist, we know quite well what they would look like if they did.

  • (Score: 1, Funny) by Anonymous Coward on Sunday June 01 2014, @04:26PM

    by Anonymous Coward on Sunday June 01 2014, @04:26PM (#49930)

    ,,,there is a hole in their logic. Which one is what is under debate.

    Now, considering the Milky Way is a spiral galaxy with one hole or another in the middle of it then perhaps the religious can also spin their logic. Provided whichever hole it is has the galaxy spiralling into it of course, one could say God pulled the lever to flush what He created and that the earth and its occupants are headed towards the hole. Could that be the number we are to calculate? The one that reveals when the Earth is to arrive at the hole? Disintegrate due to the related pressures of gravity? Collide with other bodies of mass headed down the drain with us? Etc. Hey, maybe they will come up with some useful numbers while they try to figure it out. Perhaps even collide with the Truth!

    So, which one is it? The hole or the doughnut?

    • (Score: 2, Insightful) by Anonymous Coward on Sunday June 01 2014, @05:01PM

      by Anonymous Coward on Sunday June 01 2014, @05:01PM (#49938)

      I think you're slightly confused as to the nature of a black hole.

      • (Score: 2) by maxwell demon on Sunday June 01 2014, @06:10PM

        by maxwell demon (1608) Subscriber Badge on Sunday June 01 2014, @06:10PM (#49951) Journal

        Eventually indeed all (ordinary) matter of the galaxy will fall into the central black hole (assuming there's no other disturbance, like another galaxy colliding with ours), because of friction and emission of gravitational waves. However, this will happen long after the last star has burned out.

        --
        The Tao of math: The numbers you can count are not the real numbers.
        • (Score: 1, Interesting) by Anonymous Coward on Sunday June 01 2014, @06:36PM

          by Anonymous Coward on Sunday June 01 2014, @06:36PM (#49963)

          This also isn't true. You're assuming

          1) The black hole at the centre of the galaxy is assymmetric enough to emit gravitational radiation itself, which is unknown but possible.
          2) The rate at which binary systems in the galaxy as a whole emit gravitational radiation is sufficient to cause them to inspiral -- which it very much is not, since the emission of the gravitational waves acts instead to symmetrise the system, meaning that the binary (or tertiary etc.) systems will tend to collapse *on themselves* while their centre of mass continues to orbit as before. This is unlikely to be so since we know of many binary systems that have singularly failed to fall into the centre of the galaxy despite one or even both of their members being M type stars and roughly as old as the galaxy itself.
          3) That the rate of friction, both physical with matter in the galaxy, and dynamical with other stars in the galaxy, is significant enough to cause an inspiral within the lifetime of stars in the galaxy. That it isn't is amply demonstrated by the sheer numbers of M type stars which are as old as the galaxy itself.
          4) That these effects, if present, will be short on the timescale of the black hole's own lifetime. While it is true that a supermassive black hole has a very low rate of Hawking emission and a correspondingly vast lifetime, it is still not at all clear that the rates of friction and of "emission of gravitational radiation" are anything like high enough to cause a significant inspiral. Indeed, it seems much more likely that the rate of inspiral is extremely long in relation to stars' own lifespans and that instead the stars in our galaxy will have burned themselves into tedious carbon/iron/neutron husks many untold billions of years before there would be significant inspiral.

          These being so, I don't think it's particularly fair to say that everything will inevitably slam into the black hole at the centre of our galaxy, since on a timescale shorter than any of these effects we will also be colliding with Andromeda, with a significant disruption of stellar orbits and a far more significant interplay between the two supermassive holes than anything with any of the stars.

          That everything in the universe is likely to end up in a black hole of one form or another is less controversial -- decay rates are slow, and ultimately it seems that most if not all future-direct timelike geodesics will terminate within some event horizon or other. The interesting thing that that implies is that the later end-state of all this energy is not going to be within black holes at all, given that they evaporate, but rather in a low-energy uniform bath of radiation.

          • (Score: 3, Informative) by maxwell demon on Sunday June 01 2014, @07:35PM

            by maxwell demon (1608) Subscriber Badge on Sunday June 01 2014, @07:35PM (#49972) Journal

            1) The black hole at the centre of the galaxy is assymmetric enough to emit gravitational radiation itself, which is unknown but possible.

            No, I wasn't assuming that. The orbiting stars emit gravitational radiation due to the very fact that they orbit around the center of the galaxy. They do so even if they orbit a completely spherical black hole (or even if what they orbit isn't a black hole at all). Yes, it's extremely little gravitational radiation, but it's not zero.

            2) The rate at which binary systems in the galaxy as a whole emit gravitational radiation is sufficient to cause them to inspiral -- which it very much is not, since the emission of the gravitational waves acts instead to symmetrise the system, meaning that the binary (or tertiary etc.) systems will tend to collapse *on themselves* while their centre of mass continues to orbit as before. This is unlikely to be so since we know of many binary systems that have singularly failed to fall into the centre of the galaxy despite one or even both of their members being M type stars and roughly as old as the galaxy itself.

            The stars (no matter whether solitary stars or binary system, all orbit the center of the galaxy. That's the rotation I'm referring to.

            3) That the rate of friction, both physical with matter in the galaxy, and dynamical with other stars in the galaxy, is significant enough to cause an inspiral within the lifetime of stars in the galaxy. That it isn't is amply demonstrated by the sheer numbers of M type stars which are as old as the galaxy itself.

            This one I explicitly did not assume. Quite the opposite: I explicitly states that it will happen long after the stars burned out, that is the exact opposite of what you claim I assumed. Of course the matter of the stars doesn't magically disappear when stars burn out (some of it will go into local black holes, but for those the same mechanisms apply).

            4) That these effects, if present, will be short on the timescale of the black hole's own lifetime.

            You're right, I indeed did not take Hawking radiation into consideration; that might indeed save the matter from falling into the black hole (note however that the black hole only starts to shrink after the CMB temperature falls below the black hole's Hawking temperature, which for supermassive black holes is extremely low.

            Indeed, it seems much more likely that the rate of inspiral is extremely long in relation to stars' own lifespans and that instead the stars in our galaxy will have burned themselves into tedious carbon/iron/neutron husks many untold billions of years before there would be significant inspiral.
            And not coincidentally, my post you replied to contains the following sentence: "However, this will happen long after the last star has burned out." I think for a short two-sentence post, it's not to much to ask that you read both sentences before you answer.

            These being so, I don't think it's particularly fair to say that everything will inevitably slam into the black hole at the centre of our galaxy, since on a timescale shorter than any of these effects we will also be colliding with Andromeda

            Well, my post you replied to also contained the following: "(assuming there's no other disturbance, like another galaxy colliding with ours)" so I already explicitly accounted for that possibility. But thanks for the information that this will indeed happen.

            tl;dr: The only mistake in my post is that I forgot about the Hawking radiation, which may indeed allow the matter in the galaxy escape the black hole by the black hole evaporating away before the matter reaches it (ignoring the collision with Andromeda, a fact I didn't know about but which is already accounted for in the conditions I gave).

            --
            The Tao of math: The numbers you can count are not the real numbers.
            • (Score: 1, Interesting) by Anonymous Coward on Sunday June 01 2014, @08:22PM

              by Anonymous Coward on Sunday June 01 2014, @08:22PM (#49983)

              Ouch, I just got served. Full and unreserved apologies.

              • (Score: 2) by maxwell demon on Sunday June 01 2014, @08:43PM

                by maxwell demon (1608) Subscriber Badge on Sunday June 01 2014, @08:43PM (#49985) Journal

                Well, no problem, we all make mistakes. Anyway, after all you did identify a mistake in my post, namely that I forgot the Hawking radiation. Since we are speaking about the competition of processes which are all very slow, it isn't obvious (at least not to me) which one would eventually win (for an undisturbed galaxy).

                BTW, I just now notice that there's another possibility I didn't think of: An accelerating expansion of the universe might rip the galaxy apart before the black hole in the center had time to eat it (assuming it would otherwise live long enough).

                --
                The Tao of math: The numbers you can count are not the real numbers.
                • (Score: 3, Interesting) by yellowantphil on Sunday June 01 2014, @08:56PM

                  by yellowantphil (2125) on Sunday June 01 2014, @08:56PM (#49990) Homepage

                  which one would eventually win (for an undisturbed galaxy)

                  I hear that the Andromeda Galaxy has been eyeing us suspiciously for a while now, and Wikipedia tells me that we only have 3.75 billion years or so until a collision.

                  There is probably a reason this can't happen, but what if the Andromeda and Milky Way galaxy centers are the endpoints of a single wormhole? What happens if the wormhole endpoints collide? Does the wormhole just disappear, or maybe does some spacetime get severed, leaving a tiny, doughnut-shaped universe that used to be the wormhole?

                  • (Score: 1, Interesting) by Anonymous Coward on Sunday June 01 2014, @10:02PM

                    by Anonymous Coward on Sunday June 01 2014, @10:02PM (#50007)

                    Both ends would just be a black hole, so a nice big black hole with a highly disturbed galaxy orbiting around it.

                    Entertainingly, that's actually supposition -- good luck calculating what happens when black holes collide. We can basically do it, but we're always rather inhibited by concepts such as an "event horizon". The problem is that an event horizon is total, but grows as a black hole takes in mass, which unfortunately means that something which at time x is well outside what looks like the event horizon is in fact well inside the event horizon as seen from x + 100000000 years. This has a... complicating effect on simulations, which are also somewhat hindered by the tendency of your grids to fall into the black hole.

                    We also have no idea what would happen if two singularities crashed, not least since we can't model a singularity anyway, by definition. What to my mind would be even more fascinating would be to take one Schwarzschild hole (spherical, non-rotating) and smash a Kerr hole (non-spherical, rotating) into it. This is fascinating because the internals are totally different: a Schwarzschild hole has that famous inevitable singularity lurking greedily in your future; but a *Kerr* hole's singularity is both cylindrical with a nice friendly hole in the middle of it, and doesn't lurk inevitably in your future anyway. On the diagrams (Schwarzschild: http://online.kitp.ucsb.edu/online/colloq/hamilton1/oh/penrose_Schwpar.gif [ucsb.edu] Kerr: http://www.phys.utk.edu/daunt/Astro/Overheads/BH/Penrose%20Rotating%20BH.jpg [utk.edu]) the Schwarzschild singularity is horizontal, and since all motion has to be in lines 45 degrees from vertical and moving upwards, you're fucked. This is a "spacelike" singularity since it cuts across timelike motion. The Kerr singularity, on the other hand, is vertical, and we can easily see that if we're clever we can avoid it, particularly given the hole in its insides. Of course, have fun trying to navigate inside a black hole and rather you than me because not just your sense of direction but your very sense of *dimension* will be fucked up, but even so. The interest would be what happens? The Kerr hole will evidently disrupt the Schwarzschild geometry such that it can't be Schwarzschild anymore, that's straightforward, and the end result will be another Kerr hole, through conservation of angular momentum if nothing else, but how does it get there? What happens to the singularities? How do they restructure themselves? What would happen if we smacked a Schwarzschild hole with *two* counter-rotating Kerr holes? Or, even better, with six of them, keeping all possible isotropy?

                    So far as I know, these questions are unanswerable except that we basically know the starting and ending states. It doesn't help that as soon as you fire a Kerr hole at a Schwarzschild you can't use *either* solution and have to model it numerically. (Both Schwarzschild and Kerr are global; they assume there is no other gravitating matter in the universe.)

                    Something else along the same lines would be to take a Schwarzschild hole, and then fire an electron into it, dead at the centre. This imaprts a charge. A *charged* spherical black hole is a Reisser-Noerdstrom hole, and internally it looks a lot like Kerr. The singularity isn't cylindrical but it also isn't inevitable. So firing that one electron into the hole has totally rearranged the hole's insides. How about firing it in off-centre? Then the hole picks up a tiny angular momentum along with its tiny charge, and becomes what is known as a Kerr-Newman -- charged and rotating. The insides are basically identical to a Kerr with unimportant differences, but again the fundamental nature of the hole has changed.

                    I think the thing to take away from this is that if we're under attack from aliens using a wormhole we should just squirt a few electrons into it and that's their wormhole fucked. Unless they're instead navigating inside a Kerr and coming from that weird patch of space with a naked singularity glowing in the middle (which the diagram above is slightly oddly calling an "antigravity universe" and I'm not totally sure why), in which case we can just chuck rubbish into it against the spin until it balances, and then that's their wormhole dead.

                    • (Score: 0) by Anonymous Coward on Monday June 02 2014, @11:58AM

                      by Anonymous Coward on Monday June 02 2014, @11:58AM (#50162)

                      Something else along the same lines would be to take a Schwarzschild hole, and then fire an electron into it, dead at the centre. This imaprts a charge. A *charged* spherical black hole is a Reisser-Noerdstrom hole, and internally it looks a lot like Kerr. The singularity isn't cylindrical but it also isn't inevitable. So firing that one electron into the hole has totally rearranged the hole's insides. How about firing it in off-centre? Then the hole picks up a tiny angular momentum along with its tiny charge, and becomes what is known as a Kerr-Newman -- charged and rotating. The insides are basically identical to a Kerr with unimportant differences, but again the fundamental nature of the hole has changed.

                      Actually, the electron has an intrinsic angular momentum (spin!), therefore even a centrally falling electron will give the black hole an angular momentum. BTW, from a quantum mechanical point of view, you'll change it from a bosonic to a fermionic black hole (assuming those terms make actually sense for black holes).

                      Another interesting fact is that the gyromagnetic ratio of a charged black hole is 2, just as for an electron (without QED corrections, but then, the black hole gyromagnetic ratio is calculated without QED corrections ass well). Now if you assume the electron were a black hole, what would be its radius? Well, it turns out the electron violates the restrictions for charged black holes; a Reisser-Noerdstrom solution for those parameters would be a naked singularity.

                      Maybe if we want to know what the interior of a black hole really looks like, we have to look no further than to the electron.

                      • (Score: 0) by Anonymous Coward on Monday June 02 2014, @08:20PM

                        by Anonymous Coward on Monday June 02 2014, @08:20PM (#50391)

                        "Actually, the electron has an intrinsic angular momentum (spin!), therefore even a centrally falling electron will give the black hole an angular momentum. BTW, from a quantum mechanical point of view, you'll change it from a bosonic to a fermionic black hole (assuming those terms make actually sense for black holes)."

                        Ah, but as I suspect you know we'd need a quantum theory of gravity to know how the spin of an electron would interact with the spin of a black hole - they're related, but distinct, concepts. I've no doubt that in a quantum description of a black hole whatever the quantum analogue of the hole's angular momentum is would interact with the spin angular momentum of the electron, but I'm not feeling up to speculating just how at the minute. (It's possible that people working on loop quantum gravity have an idea. Alas, I don't know all that much about loop quantum. My impression is both that it's still hard to add matter into the theory, and also that the hole solution they have is Schwarzschild only, but I'm years out of date.)

                • (Score: 1, Interesting) by Anonymous Coward on Sunday June 01 2014, @09:45PM

                  by Anonymous Coward on Sunday June 01 2014, @09:45PM (#50002)

                  I wouldn't overstate Hawking radiation *too* much -- it gets increasingly slow for increasingly large black holes. I think what's more likely to happen is mergers of dead galaxies will feed the hypermassive black holes at a rate far in excess of the infall from those galaxies -- the various frictions genuinely close to negligible and then, eventually, after many, many tens or hundreds of billions of years, those deadened stars will have started to fall in too. But there's other processes at play, too -- stars are always flung out of galaxies, let alone during mergers, and while yes it's true that future timelike infinity will be in a black hole that's a genuine infinity, whereas it's possible that even the likes of protons are unstable and will decay to radiation quite possibly long before encountering a hole. (Then, eventually, all those holes will themselves have decayed back to radiation, which will occasionally collide with enough energy to make matter -- or even tiny holes, and then back to radiation, like little eddies in the superlong wavelength radio waves. If we believe Penrose then since distance becomes quite meaningless in a pure-radiation universe, we could have a phase transition back to the radiation-dominated era at the start of another big bang, but he has never published anything on that one.)

                  With acceleration, it really does depend on what's causing that. The acceleration is a feature of a smooth universe, and any local gradients will muck up the pressure, quite possibly enough to stop it from locally being "anti-gravitational" at all. A gradient-dominated field would have an equation of state of w=-1/3 (so satisfying the weak energy condition, barely, rather than violating it), and a velocity-dominated field has a super-stiff equation of state w=-1. The equation of state will therefore be highly position-dependent and range between -1 and 1, and we need between -1 and -1/3 to get an acceleration. It's possible then that an acceleration caused by a quintessence will not tear galaxies apart because it simply won't act that way in the presence of lumpy matter. This effect is naturally heightened if the field couples to matter, such as a Galileon, a chameleon or a symmetron.

                  On the other hand, if it's a cosmological constant we still don't have to worry, since even though this will keep an equation of state of -1 everywhere and in every spacetime, we have solutions for things like Schwarzschild-de Sitter (black hole in the presence of a cosmological constant) or Lemaitre-Tolman-Bondi-de Sitter (spherical cluster in the presence of a cosmological constant) and the solutions are stable. The point is that acceleration in this way is a facet of the *global* spacetime, assuming that that spacetime looks like Robertson-Walker and obeys its evolution equations. On a local level, and GR is nothing if not a local theory, it's not necessarily the case.

                  (Having fun with phantoms, though, and yeah you'll rip your galaxy apart long before the hole eats it all.)

                  Sorry again for being a douche; you're right, somehow in a two-line post I missed an important point in my haste to spew a load of things on page which while broadly accurate were almost irrelevant to your post, which had nothing wrong with it (except perhaps a couple of missed edge cases).

  • (Score: 2) by Subsentient on Sunday June 01 2014, @06:29PM

    by Subsentient (1111) Subscriber Badge on Sunday June 01 2014, @06:29PM (#49960) Homepage Journal

    How do you think I travel to Universe 2?

    --
    "It is no measure of health to be well adjusted to a profoundly sick society." -Jiddu Krishnamurti
  • (Score: 3, Interesting) by zeigerpuppy on Sunday June 01 2014, @10:32PM

    by zeigerpuppy (1298) on Sunday June 01 2014, @10:32PM (#50017)

    Forgive me if I've missed something but it seems their argument hinges on the idea that black holes are more numerous and smaller than predicted so some of them must be wormholes.

    Ok, let's go with that logic for a moment.
    My question is, if wormholes act like black holes but are dumping the incoming mass somewhere else in the universe/multiverse then why don't we also see the exit wormholes, which would presumably be very bright objects - maybe white holes?

    Maybe this is a candidate for gamma ray bursters, I guess as the material got accelerated through a wormhole it would emerge with quite a bang from the other end, then again this would probably produce a jet of material, which as far as I know has not been observed from objects other than candidate black holes.

    • (Score: 2) by GreatAuntAnesthesia on Monday June 02 2014, @08:34AM

      by GreatAuntAnesthesia (3275) on Monday June 02 2014, @08:34AM (#50123) Journal

      > My question is, if wormholes act like black holes but are dumping the incoming mass somewhere else in the universe/multiverse then why don't we also see the
      > exit wormholes, which would presumably be very bright objects - maybe white holes?

      So what is it?

    • (Score: 0) by Anonymous Coward on Saturday June 07 2014, @05:36PM

      by Anonymous Coward on Saturday June 07 2014, @05:36PM (#52669)

      Meanwhile, in another part of the multiverse, astrophysicists are pondering the question: "We reckon white holes are a sort of space-time wormhole, but where does their energy/matter come from?"

    • (Score: 0) by Anonymous Coward on Saturday June 07 2014, @09:09PM

      by Anonymous Coward on Saturday June 07 2014, @09:09PM (#52762)

      How about the big bang? We had one of those, seemed like a fair amount of matter.

      • (Score: 0) by Anonymous Coward on Sunday June 08 2014, @06:45AM

        by Anonymous Coward on Sunday June 08 2014, @06:45AM (#52885)

        OK, so bad form to reply to one's own post, but I've been toying with this in the back of my brain. So, suppose we're dealing with wormholes instead of black holes. Suppose further that my earlier supposition that the "exit" is a new universe, a big bang resulting in a new aspect of the multiverse. Let's consider our own universe. You can only see back so far, 13.8 billion years or so. It's an event horizon, sort of in the opposite direction of a back/worm hole's.

        So, maybe a star undergoes gravitational collapse, becomes a singularity with an event horizon in our universe, everything blows out as the big bang of a sort of pocket universe. The event horizon prevents interaction, a boundary between universes, so to speak.

        Take it a little further. If the above is true, then the singularity would contain, effectively, the compressed spacetime of another universe collapsed to a single point. If that singularity comprised the entirety of the space and time of another universe, then anything that EVER fell below the event horizon in our universe must ALWAYS have existed in the "pocket" universe (if something gets blasted into the timeline of another universe, wouldn't it make sense that it existed in EVERY time in that universe, which would keep with the conservation of energy of that universe [can't have new matter just blasting in from a white hole from another universe, breaks the rules]).

        So the tidal forces at the event horizon in our universe rips matter apart for billions of years, drops it below the event horizon into the singularity that is another universe, and the entirety of everything that ever fell below that event horizon pops out as the big bang of a new universe.

        This is, of course, all wildly speculative, but it's a fun thought experiment with all kinds of interesting consequences.

  • (Score: 1) by Walzmyn on Monday June 02 2014, @12:41AM

    by Walzmyn (987) on Monday June 02 2014, @12:41AM (#50045)

    How does this get called a novel idea? Maybe they've got a novel bit of Math behind it but I've been hearing this idea from scientists and sci fi writers for decades.

    • (Score: 0) by Anonymous Coward on Monday June 02 2014, @07:33AM

      by Anonymous Coward on Monday June 02 2014, @07:33AM (#50115)

      Unless you can point me to a paper -- or, apparently, a story -- with the same idea I'm not inclined to believe that. Please bear in mind that "the black hole at the centre of the galaxy might be a wormhole!!!!!!!" isn't the novelty in the paper. Papers in astronomy are very rarely entirely convulsive and are instead incremental. The title *should* explain what the enhancement is, and the abstract is structured so that the first half summarises the issue and the second half the enhancement. So here the title is

      "Distinguishing black holes and wormholes with orbiting hot spots"

      which clearly states that the novelty is that they think they can distinguish between a supermassive black hole and a supermassive wormhole through what they dub as "orbiting hot spots". To learn precisely what those actually are, and what prospects we might have to do this in reality, we have to dig further. So lets look at the abstract.

      "The supermassive black hole candidates at the center of every normal galaxy might be wormholes created in the early Universe and connecting either two different regions of our Universe or two different universes in a Multiverse model. Indeed, the origin of these supermassive objects is not well understood, topological non-trivial structures like wormholes are allowed both in general relativity and in alternative theories of gravity, and current observations cannot rule out such a possibility."

      This is a summary of the current state of affairs, which has been speculated over for quite a few decades, as you say.

      "In a few years, the VLTI instrument GRAVITY will have the capability to image blobs of plasma orbiting near the innermost stable circular orbit of SgrA*, the supermassive black hole candidate in the Milky Way. The secondary image of a hot spot orbiting around a wormhole is substantially different from the one of a hot spot around a black hole, because the photon capture sphere of the wormhole is much smaller, and its detection could thus test if the center of our Galaxy harbors a wormhole rather then a black hole."

      This is the novel part, that there will be an instrument called GRAVITY attached to the VLTI which will be observing Sagittarius A*, and that the authors have developed a means that they believe could allow us to distinguish between the black hole and the wormhole.

      So unless you're actually meaning that sci-fi authors have for decades been speculating on the relatively arcane idea that we might see hotspots dancing around black holes and wormholes that are characteristically different, I think you're probably mistaken. And let's face it, it's not the type of idea that particularly easily leads to fascinating plots.