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Space Science

How To Destroy a Black Hole 364

Posted by Soulskill
from the put-it-in-a-michael-bay-movie dept.
KentuckyFC writes "The critical concept that makes a black hole black is the event horizon: a theoretical boundary in space through which light and other objects can pass in one direction but not the other. Since light cannot escape the event horizon, it must be black. The event horizon is a nuisance to astrophysicists because it hides the interesting new physics that must go on inside a black hole. What they would like is a way to get rid of the event horizon so that they can see what goes on behind it. It turns out that just such a thing may be possible, say physicists. According to the mathematics of general relativity, the event horizon should disappear if a black hole were fed enough charge and angular momentum relative to its mass. However the calculations are so fiendish (PDF) that nobody knows whether the black hole would shed this extra angular momentum and charge before it could settle into a stable 'naked' state. However, the possibility that the event horizon could be destroyed raises the question of what astrophysicists would see behind this veil. According to some, black holes are regions of spacetime with infinite curvature called singularities. Many believe that 'naked' singularities cannot exist in nature. And yet there are enough question marks to suggest that this mystery is far from settled."
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How To Destroy a Black Hole

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  • Why am I getting a DEP when trying to open that PDF link?

  • This is just damned neat. Destroy a black hole! Observe a singularity! Watch the cosmos bend into itself! Or...?

    The best science is the stuff that ends in a big question mark. e.e. cummings nailed it on the head: "always the beautiful answer who asks a more beautiful question."

  • I thought this was another story about somebody wanting to nuke the Gulf of Mexico.

  • by postbigbang (761081) on Friday June 11, 2010 @11:26AM (#32536942)

    All of my lost left sox.

    Two bolts from my motorcycle.

    The lost chord.

    George Bush's dignity.

    Several B-19s last seen headed towards Bermuda.

    An iPhone 4G prototype.

    Darl McBride's balls.

    And I'm sure there's more.

  • Isn't the event horizon the point at which the gravitational pull of a black hole becomes so powerful that not even light can escape? How on earth will feeding the black hole more mass make the event horizon go away? I thought more mass meant more gravity..
    • by Jeng (926980)

      Yes, but its gravity on our side of the event horizon which should pull the event horizon towards the mass perhaps opening a window in the event horizon.

      I could be very wrong.

    • Re:IANAA (Score:5, Informative)

      by Remus Shepherd (32833) <remus@panix.com> on Friday June 11, 2010 @12:06PM (#32537676) Homepage

      (Disclaimer: I Am A Physicist, but this is not my area of expertise, and only the experts understand those equations.)

      It's not feeding it mass that does the trick; it's feeding it charge and angular momentum. The only reason you feed it more mass is because you need mass to carry the charge and momentum into the hole.

      What you get if you feed it charge and angular momentum is a spinning monopole. I think they are postulating that a spinning monopole causes rotational frame dragging [wikipedia.org], and if you do it right you can get the charged frame dragging effects to cancel out the gravitational effects -- namely, the event horizon.

      After you do all that, what will be left? Like the article says, nobody knows. That's why it's exciting.

  • Steve Jobs won't allow you to discuss it or show it on your iPhone/Pad

    And the Australian Government will track every time you mention it in e-mail or surf the web to the site

  • See? The writers of StarGate SG-1 already knew this when they wrote the 200th episode, which had the line: "The singularity is about to explode!"

    ...I really need a life, don't I?
    • Re: (Score:3, Interesting)

      by Unordained (262962)

      And yet, a small / primordial-enough black hole, after evaporating down to (and just below) its critical mass, could be seen as exploding back into flat-space, no? So the phrase could make sense?

  • by DriedClexler (814907) on Friday June 11, 2010 @11:30AM (#32537012)

    Since light cannot escape the event horizon, it must be black.

    Right, because anyone imprisoned anywhere must be black, because only blacks break the law and get locked up.

    • So, if we change the name to !white will that make you happy?
    • Re: (Score:3, Informative)

      There are people who think you are joking, and that is my best guess. The problem with your joke (if it is a joke) is that there are actually people who think there is something racist about using the word "black" in the term "black hole". I believe that there was a story on here about that one to two years ago (no, I'm not going to go search for it). Even if it wasn't on here, there was such a story in that time frame.
  • by Lord Lode (1290856) on Friday June 11, 2010 @11:30AM (#32537018)

    I once read a bit about black holes, and one of the things I read was: a black hole doesn't necessarily have to be very dense. It can also be sparse (and the larger, the sparser it can be). For example, if you'd take a lot of stars and planets, and put them together (but not too close together), then at one point if you make this large enough, it'll also be a black hole: there appears an event horizon around all this matter. But inside of it are still stars with gaps between them, maybe some planets orbiting around them, ... So now I wonder, if the above is true: can someone live inside that? Would there be any noticeable difference between being inside of that, and the other side (the outside) of this event horizon?

    • by magsol (1406749)
      I think Slashdot had an article a few months ago, regarding a new theory that hypothesized our known universe actually existing within a giant black hole. Or was it inside a wormhole? It might have been the latter, given that black holes are, by definition, exceedingly dense. I've never heard of "sparse" black holes before, since they have to be dense in order to form in the first place.
    • In theory, yes. (Score:5, Informative)

      by maillemaker (924053) on Friday June 11, 2010 @11:42AM (#32537226)

      One of the problems with approaching a black hole (aside from massive amounts of radiation around ones actively eating matter) is the fact that the force of gravity increases as you approach the mass responsible for the gravity.

      With small black holes, as you approach (feet first) the difference in gravitational pull at your feet would be many times larger than the gravitational pull at your head. You would be literally ripped apart, down to the molecular level. This is known as "Spaghettification".

      http://en.wikipedia.org/wiki/Spaghettification [wikipedia.org]

      However, with a large enough black hole, you should be able to pass the event horizon before these tidal forces grow large enough to rip you apart. Of course, this does you no good, because once you are inside the event horizon you cannot exert a great enough force to prevent yourself from falling deeper until the forces ARE great enough to rip you apart.

      But for a large black hole, in theory, you could cross the event horizon without being ripped apart.

    • by Jugalator (259273)

      If you go inside the event horizon (i.e. where we can't see what's going on), regardless how big the black hole is, it is still inevitable that what goes in, must continue going in until it approaches the singularity, or whatever is there where our laws of physics break down. I use to look at the event horizon as something that is per definition the border where things mustn't go in, and where it must. So I don't think that environment is stable enough for life to thrive in; it'd inevitably enter the singul

    • by quercus.aeternam (1174283) on Friday June 11, 2010 @11:49AM (#32537356) Homepage

      It seems to me that in order for an established orbit to exist on the event horizon, the orbiting matter would have to be going at the speed of light. I would further presume that any matter orbiting within the event horizon would have to be /exceeding/ the speed of light.

      To my knowledge, matter cannot travel at or beyond the speed of light.

      • by Luyseyal (3154)

        The event horizon can be thought of as a photon gas where the photons "orbit" at the speed of light. My philosophical position is that <hand-waving>all the matter is converted into energy at the event horizon due to the extreme physics going on</hand-waving>, so the black hole itself is just a photon gas and everything in it travels at c.

        -l

    • If you were inside a black hole you'd probably see crazy stuff happening like the universe expanding at an ever faster rate and all your calculations about the total mass of the universe that are derived from observing velocities over periods of time would be way off.

    • Re: (Score:3, Informative)

      by bcrowell (177657)

      I once read a bit about black holes, and one of the things I read was: a black hole doesn't necessarily have to be very dense. It can also be sparse (and the larger, the sparser it can be). For example, if you'd take a lot of stars and planets, and put them together (but not too close together), then at one point if you make this large enough, it'll also be a black hole: there appears an event horizon around all this matter. But inside of it are still stars with gaps between them, maybe some planets orbitin

  • Really? (Score:2, Insightful)

    by Tarchan (1021797)
    I thought that the event horizon of a black hole was caused by the immense gravity of the main body. Just an area of space around the black hole where light would be unable to maintain enough momentum to escape the gravitational pull of the singularity. I don't even want to try understanding the calculations that this theory was derived from. If you were able to remove the event horizon, would that not mean that you would be destroying the singularity itself?
    • Re:Really? (Score:4, Interesting)

      by Statecraftsman (718862) * on Friday June 11, 2010 @11:41AM (#32537190) Homepage
      The singularity is a lie. By which I mean, it's not as if this mass is all really in one infinitesimal dot...it's just that you do any characterization of that mass when even light can't escape. So no, you wouldn't be destroying the singularity since we don't really know that's what it is, but, if they do happen to change the black hole by adding charge and angular momentum, and it allows radiation to escape it will cease to be a black hole.

      I would like to find a black hole that's just barely massive enough and then try this.

      Finally, I think they're just trying to do a thought experiment whereby they change the shape or topology of the event horizon. Imagine a toroidal event horizon for example.
    • Re:Really? (Score:5, Insightful)

      by cyber0ne (640846) on Friday June 11, 2010 @12:00PM (#32537580) Homepage
      I'm not an expert on this by any means, but here's my two cents...

      Try not to think of it in terms of light trying to escape in a straight line and just not being strong enough to do it. Instead, think of the straight line as not being straight. Gravity wells curve space-time (a Google Images search for "spacetime" will yield some familiar diagrams of spheres resting on a fabric), and the event horizon of a singulatiry is the point in that curvature where it's so "steep" that it curves back in upon itself. This is difficult to show in the aforementioned diagrams, because it's less about the picture and more about the math behind it.

      Basically, from behind the event horizon it's impossible to escape not because you don't have enough force to get away but because all paths lead back to the singularity.

      If somebody with more knowledge/expertise on the subject can correct/elaborate, please do.
    • If you were able to remove the event horizon, would that not mean that you would be destroying the singularity itself?

      No. The only reason the event horizon exists is because gravity is pulling so hard that light can't escape. If you were to alter the system so that the pull of gravity is weaker, or is offset by some sort of relativistic frame dragging effect (which is I think what they're postulating here), then the event horizon could disappear while the singularity remains.

      Think of the classic space-time fabric picture, where a black hole is an infinite vortex punched down through the fabric. They're pushing the fabri

  • by pitdingo (649676) on Friday June 11, 2010 @11:34AM (#32537068)
    I sure am dumb
  • Naked Event Horizon (Score:4, Interesting)

    by Rockoon (1252108) on Friday June 11, 2010 @11:35AM (#32537074)
    We always hear about singularities necessitating event horizons, but the converse is most certainly not true. An event horizon may exist without a singularity inside of it.

    It depends on scale more than anything. Small black holes almost certainly require a singularity, but a black hole the mass of a galactic cluster actually has a very low average density. So while at the event horizon space-time is very much distorted, on the inside it may not be distorted enough to overcome common everyday forces (the trick of treating a collection of mass as a point source of force doesnt work from inside that collection of mass)
    • Exactly -- why go into space for zero gravity, when we've got an area of zero gravity right here inside our own planet? We should drill down, not rocket up!

    • Re: (Score:3, Insightful)

      but a black hole the mass of a galactic cluster actually has a very low average density. So while at the event horizon space-time is very much distorted, on the inside it may not be distorted enough to overcome common everyday forces (the trick of treating a collection of mass as a point source of force doesnt work from inside that collection of mass)

      Now my brain hurts, could we already be inside an enormous black hole?

  • Photons cannot escape because they are red-shifted due to time dilation. This means that the horizon will vary depending on the level of energy trying to escape it. For example, an X-ray might escape where an infra-red photon wouldn't. All or part of a huge energy blast may or may not escape, depending on its frequency, level and position. Whether it would affect the hole itself seems problematic.
    • Re: (Score:3, Informative)

      by alyosha1 (581809)

      Uh, no. An X-ray photon and an infra-red photon have the same velocity, c. They have different frequencies. Neither will escape a black hole, which is pretty much defined as a body having an escape velocity greater than c.

    • Re: (Score:3, Informative)

      The event horizon isn't wavelength-dependent. It's the place where the escape velocity equals the speed of light.

      • by $RANDOMLUSER (804576) on Friday June 11, 2010 @12:55PM (#32538630)

        The event horizon is ... the place where the escape velocity equals the speed of light.

        Ding ding ding - we have a winner. This is the point that so many cosmology shows on Discovery Channel or Science Channel (or whatever) completely fail to mention; they keep describing black holes as "so massive, even light can't escape" without explaining why (Michio Kaku, Alex Fillipenko, (sp) I'm looking at you). See Wikipedia [wikipedia.org] for the details, but the important point is that escape velocity is dependent on an object's mass divided by its radius. So if mass goes high enough, or radius low enough, you get an escape velocity greater than the speed of light: AKA an event horizon.

        Say it again, and remember it later:
        The event horizon is ... the place where the escape velocity equals the speed of light.

  • Hello,

        Suppose you were falling into a black hole, and you didn't get turned into spaghetti (as might be possible if you're approaching the event horizon of a supermassive black hole). Would the event horizon seem to retreat before you? I mean, light can't escape a black hole's event horizon as we see it, but if you're falling in, wouldn't you be able to see further into the black hole as you fall?

    --PM

    • Due to time dilation, it takes a seemingly infinite amount of time to reach an event horizon because your speed will approach the speed of light. So it is impossible for an observer to reach an event horizon without an infinite amount of time.
    • Re: (Score:2, Interesting)

      by dcmoebius (1527443)

      Hello,

      Suppose you were falling into a black hole, and you didn't get turned into spaghetti (as might be possible if you're approaching the event horizon of a supermassive black hole). Would the event horizon seem to retreat before you? I mean, light can't escape a black hole's event horizon as we see it, but if you're falling in, wouldn't you be able to see further into the black hole as you fall?

      --PM

      Well, since sight depends on light reflecting off of objects to work... No, as you approached the event horizon, you still wouldn't be able to see into the black hole, as no light would be escaping (hence no visual information conveyed).

      As to other point, no, the event horizon would not appear to be receding. You would seem to be approaching it normally (from your perspective), however due to time dilation, the rest of the universe would seem to be aging quite rapidly compared to you.

  • Oh no... (Score:5, Funny)

    by Tenek (738297) on Friday June 11, 2010 @11:57AM (#32537518)
    liberate tutamae ex inferis
  • I understand that this is important science, but what a weird gap in scientific knowledge when we are considering how to collapse a black hole when we can't stop the damn oil leak. Maybe we should get some of these guys involved.
  • Most of the calculations about black hole are based on steady state. However, the time it takes to reach this state is of order of event horizon size divided by speed of light. Larger the black hole, larger the time. Thus if you have a black hole of the size of our visible physical universe, it can take billions of years to reach steady state. During this billions of years, life can go on normally! In fact the equation of universe with omega greater than one (which means that the whole universe would eventu

  • A significant number believe that singularities cannot exist in the first place, naked or otherwise.

    Anyway, if a singularity could exist, it would be a point of infinite curvature in space-time, i.e. a point of infinite mass. As such I don’t see any way for it to not create an event horizon.

  • however I will argue that to make it work it may end up being a matter of trying to collide two black holes into each other with great speed. Further that though I wouldn't be surprised if that speed ends up being c.

  • I'm guessing you'd cause the black hole to eject particles that hopefully would be structured enough to provide us with information about what's happening beyond the event horizon or they might be completely random and tell us nothing. The summary and the article itself seem very confused. They portray the event horizon like it's some kind of shell that surrounds the core of the black hole hiding it from view. The event horizon is more like an asymmetric field that you need to find the right frequency to

  • Jeez, it's like these dudes have never watched Star Trek.

  • If you are inside an event horizon (you can't ever see anything outside of the event horizon),
    then if something enters your event horizon you are now able to see it, thus
    invalidating the premise of the event horizon.

    That means either:

    1) Event horizon's do not exist.
    2) You can't *really* enter an event horizon from the outside.

  • misleading title (Score:4, Informative)

    by bcrowell (177657) on Friday June 11, 2010 @12:33PM (#32538212) Homepage

    The title of the paper is "Destroying black holes with test bodies," and the language about "destroying" black holes is echoed in both the arxiv blog summary and the /. summary. This may be somewhat misleading. They're actually talking about processes that would strip away the event horizon, leaving behind a naked singularity. The black hole wouldn't have been "destroyed," but just changed into a different form. The authors themselves put the word "destroying" in quotes in the paper.

    The paper doesn't settle this one way or the other. It says shows that if you use a certain set of approximations, the result is that the event horizon can go away. However, there is no particular reason to believe that the approximation is correct.

    The real issue here isn't whether a black hole can actually be transformed this way, it's the question of whether cosmic censorship [wikipedia.org] holds. If cosmic censorship fails, then general relativity is fundamentally flawed as a classical field theory, because it fails to make predictions. John Earman's famous way of expressing this is that anything could come out of a naked singularity: lost socks, green slime, even horrible things like Nixon's "Checkers" speech or Japanese monster-movie creatures.

  • by MetricT (128876) on Friday June 11, 2010 @12:39PM (#32538314) Homepage

    I did Ph.D. research on this exact subject a decade ago, and at a quick glance I didn't see anything new in this paper. A spinning and/or charged black hole in theory can be spun or charged to the point where a naked singularity would appear. But, the harder you spin/charge the black hole, the harder it tries to neutralize itself by preferentially emitting particles of a given angular momentum or charge. So the equality probably is a physical limit. I thought someone had proven that years ago, but I've been out of the field for a while.

    This looks kind of like someone wrote a paper so they could go to a conference or something. There doesn't appear to be anything earth-shattering (or black hole-shattering) here.

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