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Space Earth

Micro-Black Holes Make Poor Planet Killers 314

Posted by timothy
from the they-don't-even-make-good-nightclubs dept.
astroengine writes "Physicists are getting excited about the possibility of micro-black holes (MBH) being produced by the LHC and an international group of researchers have done the math to see what kind of impact they could have on the Earth. Unfortunately, if you're a megalomaniac looking for your next globe-eating weapon, you can scrub MBHs off your WMD list. If a speedy MBH is produced, flying through our planet, it will only have a few seconds to accrete the mass of a few atoms. It would then be lost to space where it will evaporate. If a slow MBH is produced, dropping into the Earth where it sits for a few billion years, the results are even more boring."
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Micro-Black Holes Make Poor Planet Killers

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  • by amazeofdeath (1102843) on Friday November 13, 2009 @09:13AM (#30085686)

    I guess I know what kind of girl to look for now ;)

  • by Anonymous Coward on Friday November 13, 2009 @09:13AM (#30085690)

    Sorry, but I really feel the need to be afraid of something irrational.

  • Poor MBHs (Score:3, Funny)

    by Rik Sweeney (471717) on Friday November 13, 2009 @09:18AM (#30085742) Homepage

    Ironically, it sucks to be them :)

  • by Phoenix (2762) on Friday November 13, 2009 @09:19AM (#30085750)

    Sadly however, people will read this article and will still freak out about how the LHC is going to doom us all.

    • by elrous0 (869638) *
      Yeah, but those are the same people who think aliens are traveling across the vast distances of interstellar space to play ass-grab with rednecks in trailer parks. You have about as much chance of educating the unwashed masses as you do of convincing them to become washed masses. Best to keep sedating them with sports.
    • by L4t3r4lu5 (1216702) on Friday November 13, 2009 @10:11AM (#30086194)
      How could we not read it like that?!

      "... if you're a megalomaniac looking for your next globe-eating weapon,... a speedy MBH ... flying through our planet... will only have a few seconds to accrete the mass of ... the Earth ."

      WE'RE DOOMED!

    • by jeffmeden (135043)

      Why worry? I am a firm believer that causality is forcing the LHC to not work, since if it did, it would un-create itself across the entire timeline.

  • by JoeDuncan (874519) on Friday November 13, 2009 @09:20AM (#30085752)
    ... I guess someone forgot to tell Nero

    How much red matter does the LHC use anyway?

  • And where exactly does the MBH evaporate to? Or is that all part of the mystery?
    • > And where exactly does the MBH evaporate to?

      In all directions.

      • What happens to everything it's sucked in? Does that get spat out again?

        • by Thanshin (1188877)

          Everything sucked in is already on Earth. About thirty years ago. Saving the whales, or somesuch.

        • Re:Evaporate? (Score:5, Informative)

          by gclef (96311) on Friday November 13, 2009 @10:02AM (#30086100)

          Mass = Energy...it evaporates by emitting other forms of energy (light, etc).

        • Re:Evaporate? (Score:5, Informative)

          by Maximum Prophet (716608) on Friday November 13, 2009 @10:15AM (#30086242)
          Photons pop out of the vacuum all the time. A photon and an anti-photon (or do they call it a virtual photon) will appear at the same time, and as long as the pair doesn't stick around longer than the mass * Plank's constant, conservation of mass is preserved.

          If the photon and anti-photon appear at the edge of a black hole, sometimes the photon goes off, and the anti-photon gets sucked into the black hole where it cancels some of the mass of the black hole. Thus it looks like the BH is radiating and evaporating, but nothing actual leaves the BH.

          *Note: I've left out some details, and my terminology might be off.
          • Wouldn't there be equal odds of the photon entering the black hole as the anti-photon? If so, wouldn't the mass remain constant?

            My understanding is that black holes do lose mass, but I'm just not quite sure how it really works...

            Ok, according to a quick look on wikipedia [wikipedia.org]

            Physical insight on the process may be gained by imagining that particle-antiparticle radiation is emitted from just beyond the event horizon. This radiation does not come directly from the black hole itself, but rather is a result of virtual particles being "boosted" by the black hole's gravitation into becoming real particles.

            A slightly more precise, but still much simplified, view of the process is that vacuum fluctuations cause a particle-antiparticle pair to appear close to the event horizon of a black hole. One of the pair falls into the black hole whilst the other escapes. In order to preserve total energy, the particle that fell into the black hole must have had a negative energy (with respect to an observer far away from the black hole). By this process, the black hole loses mass, and, to an outside observer, it would appear that the black hole has just emitted a particle. In reality, the process is a quantum tunneling effect, whereby particle-antiparticle pairs will form from the vacuum, and one will tunnel outside the event horizon.

            I'm not exactly sure how 'preserving total energy' works in this context, but I think I'll trust Hawking on that one.

          • Re:Evaporate? (Score:5, Informative)

            by crazyeti (1677994) on Friday November 13, 2009 @11:56AM (#30087510)
            There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle. And your explanation of the uncertainly principle is wrong. The time-energy formulation says (uncertainty in time) * (uncertainty in energy) = hbar, so the time limit for the life of the virtual particles is Planck's constant / energy (or Planck's constant divided by mass, since mass and energy are proportional and we measure the mass of these particles in units of electron-volts anyhow). Note that if it's mass * hbar, as you have above, then the higher the mass is, the longer the particles can stick around! That's exactly backwards. It's the tiny little particles that are flickering in and out of existence, not huge massive objects! If it were mass*hbar, you'd have virtual planets, stars and galaxies - the larger the object the more likely it would be to suddenly appear out of nowhere! This is an amusing thought but doesn't accurately describe the reality that we find ourselves living in.
          • Re: (Score:3, Informative)

            by crazyeti (1677994)
            There's no such thing as an anti-photon. In the case you are describing - pair production - both of the particles are virtual particles. They can be an electron and a positron (anti-electron), a quark and its anti-quark, etc - any particle/antiparticle pair. However a photon is its own anti-particle. (See http://en.wikipedia.org/wiki/Antiparticle [wikipedia.org] ) And your explanation of the uncertainly principle is wrong. The time-energy formulation says (uncertainty in time) * (uncertainty in energy) = hbar, so the
        • by jabuzz (182671)

          Sort of, but in a different form, known as Hawking radiation [wikipedia.org]

    • Re:Evaporate? (Score:5, Informative)

      by ChowRiit (939581) on Friday November 13, 2009 @10:12AM (#30086206)

      Particles. A hand-waving description of what happens is as follows:

      Pairs of particles (one matter, one antimatter) form randomly near the event horizon. One quantum-tunnels out of the black-hole and so appears to an observer outside the black-hole to have been emitted. Therefore, to conserve energy, the other particle must have negative energy and thus the black-hole loses a tiny parcel of energy (and thus mass).

      The main point is that, because the particle was formed near the event horizon and didn't come from the black-hole itself, it carries no information out - thus, while the black-hole loses mass, no information can escape.

    • Where does water evaporate to? Black hole evaporation is not quite the same; it's the release of Hawking radiation, rather than the release of gaseous water molecules, but it's the same general idea. The substance of the black hole is converted (slowly) into radiation and escapes. Because energy is just a much less dense version of matter, this means that the black hole loses mass until eventually it doesn't have enough left to remain a black hole. There's no magic or mystery any more than there is in t
    • Photons pop out of the vacuum all the time. A photon and an anti-photon (or do they call it a virtual photon) will appear at the same time, and as long as the pair doesn't stick around longer than the mass * Plank's constant, conservation of mass is preserved.

      If the photon and anti-photon appear at the edge of a black hole, sometimes the photon goes off, and the anti-photon gets sucked into the black hole where it cancels some of the mass of the black hole. Thus it looks like the BH is radiating and ev
  • I'm sure there's somebody on /. who can answer this:

    Correct me if I'm wrong, but I thought to be a black hole you had to be 2 things.
    1. a singularity
    2. heavy/massive enough to stop anything from escaping

    If you've got a singularity (worst case in our example) that's the mass of the earth, how's that supposed to stop any light/matter/etc escaping? It's not massive enough!

    or am I missing something.

    Also, please excuse my lack of correct terminology. IANAAP

    • Radius (Score:5, Informative)

      by Moraelin (679338) on Friday November 13, 2009 @09:40AM (#30085900) Journal

      Well, the key isn't just mass, but also radius. Gravity (I'll go newtonian, just because I'm lazy) increased linearly with mass, but decreases with the square of the radius. So for example, if you packed something the mass of Earth in just half the size of Earth, the gravity on the surface would be 4 times that of Earth. Squeeze it into a quarter of the size of Earth and get 16 times the gravity on the surface. Squeeze it small enough and you have a black hole.

      If you do the proper maths, the Schwarzschild radius of a black hole with the mass of Earth is about 9mm.

      Which really means, don't think something that will suck matter and bend light spectacularly all the way to Alpha Centauri. It means that if light happens to go within 9mm of that singularity, it ain't coming out. But farther away, it's still a body with the mass of Earth. The moon's orbit will still have the same radius for example.

      • by imamac (1083405)
        Incredibly helpful. Thank you!
      • Ok, so what would happen if one of these super-mini black holes were to, say, have matter thrown at them from opposite directions at close to the speed of light, with the equivalent energy of a family car hitting an immovable object at 1000MPH? Would that potentially cause it to grow?

        IANATP, but you seem to be quite well informed.
        • Let's do the maths (Score:4, Informative)

          by Moraelin (679338) on Friday November 13, 2009 @10:53AM (#30086744) Journal

          Well, yes, any matter you throw at it (and energy converts neatly to matter too) can only cause it to grow. But there's still the problem of how much and how close.

          But, really, let's do some simple maths.

          Let's say we want to produce a black hole the size of a helium atom. You know, big enough to occasionally actually bounce into stuff and gobble it up. (Remember, only matter coming closer than the Schwarzschild radius is actually gobbled up.) It's not a big black hole, but it has the potential to grow. So we apply:

          r = (2G/c^2) * m ... Where the thing in brackets is approx 1.5 * 10^-27 m/kg. We'll want to get a hole measuring 3x10^-11 m. So we'd need a mass of 2x10^15 kg, or two millions of millions of metric tons.

          Yep, that huge a mass will only gobble stuff up if it comes within 3x10^-11m of it. But it's a start, and as an evil genius you may have to start small ;)

          To produce that hole, the protons we throw at it, as a total, will have to have the equivalent of that much mass in energy.

          Let's transform that into MeV though, since we are talking energy. 1MeV is about 1.8x10^-36 Kg. Let's round to 2x10^-36, since we're only doing a back-of-the-napkin calculation, and are only interested in rough ballpark figures. So we're talking about 10^51 MeV

          If we got that energy from uranium, and assuming that we could (A) split every single U235 atom, and (B) capture 100% of the released energy, each atom split releases 180 MeV. (RL reactors don't come even close in both aspects.) Again, let's round it up to 200. (In my fantasy land, reactors are better than 100% efficient;)

          That works out to about 5*10^48 uranium atoms split. Avogadro's number being about 6x10^23, that's about 10^25 moles of uranium. (Again, I'm only interested in the order of magnitude. Plus, we rounded up in the other direction before, so it evens up.) And a mole of U235 weighs 235 grams, or about half a pound or almost a quarter kilo.

          We're talking about 2 to 3 times 10^24 kilos of uranium, or 2 to 3 times 10^21 _tons_ of U235. That's 2-3 thousand billions of billions of tons of U235. Or about a hundred thousands of billions of billions of reactor-grade enriched uranium. Completely used up in a 100% effective reactor.

          So basically yes we _could_ make a bigger black hole by keeping throwing stuff at it, close to the speed of light, but the energy requirements are nuts even to get a hole the size of a helium atom. We don't even _have_ the kind of reactors and capacitors where you could split a hundred thousands of billions of billions of reactor-grade uranium and dump it all into just creating a black hole.

    • by vadim_t (324782)

      It will trap light alright, just not at the Earth's radius.

      If all of the Earth was squeezed into a tiny point the gravity would remain the same for things that are where the ground used to be.

      But as you get closer to it, it will grow, until you can't escape anymore.

    • by Ihlosi (895663)

      If you've got a singularity (worst case in our example) that's the mass of the earth, how's that supposed to stop any light/matter/etc escaping? It's not massive enough!

      A singularity with one Earth mass will be _tiny_. That means light and matter can get so close to it that they won't be able to escape. Of course, if you're one Earth radius away from it, it'll just exert as much gravitational pull as the real Earth.

    • substitute massive for dense. BH are dense objects, but they don't need to be massive. As long as you squeeze enough mass in a tiny enough place - hence the theoretical possibility of MBH forming - you have a black hole (pardon me if I oversimplified this).
    • Well lets think for a 2D black hole. As 3d Ones are hard to picture in your head. So Imagine a plane of streachy rubber. That will represent normal space time. Then you take 2 objects say a bowling ball and a pin needle. You put the bowling ball down its massive weight has distored space time and made a large hole where an object say Rowling a marble across the plain when approaching the bowling ball would fall in the well. Next you take a pin needle you create a very small hole with the same angles as t

    • by necro81 (917438) on Friday November 13, 2009 @10:07AM (#30086142) Journal
      In principle, any mass, if packed densely enough, could become a black hole. For each mass - from a cluster of atoms to an entire galaxy - there is a calculable quantity called the Schwarzschild radius [wikipedia.org]. If you could somehow pack the mass so that it fit inside a volume smaller than that mass's Schwarzschild radius, the force of gravity would invariably overcome all other forces and cause the mass to become a singularity. The Schwarzschild radius also defines the "edge" of the black hole - if anything, including light, gets closer than one Schwarzschild radius from the central mass, it will not be able to escape. In other words, at the Schwarzschild radius, the escape velocity [wikipedia.org] is the speed of light.

      It is easy to see how the core of a really big star could collapse on itself in a supernova - there's just so much mass, coupled with the force of the explosion. However, our own sun could become a black hole - if some as-yet unknown physical process could squeeze its entire mass into a 6-km diameter sphere. The Schwarzschild radius of one solar mass is about 3 km.

      It is important to note that, were this to happen tomorrow, the Earth and the other planets would continue to orbit the black hole sun exactly as they have done for billions of years. The gravity of the sun hasn't changed, because its mass hasn't changed. If you were, however, unfortunate enough to come within 3 km of the center of the black hole sun, that's the last the universe would ever see of you. (As a practical matter, you'd be doomed long before then, simply because no rocket would be powerful enough to bring you away once you got closer than a few thousand kilometers. To escape the black hole sun once you were, say, 3.1 km away, you would need to somehow achieve a speed near to the speed of light, which we simply can't do.)

      It is also important to note that you would not be sucked into a black hole if you came within 3 km of the center of the sun as it exists today, shining hot and bright. This is because 99.999% of the mass of the sun lies outside of that 3 km radius and so "doesn't count" in terms of the force of gravity. Aside from instantly transforming into plasma from the heat, you would actually feel far less gravity than you would on the Moon. (For reasons why, see here [wikipedia.org].) Remember: a black hole would exist only if you could compress the whole mass of the sun into that 3-km radius spherical volume. This can be applied to just about any mass. The Schwarzschild radius of the Earth is about 9 mm - smaller than a grape. This gives you a sense of how densely you'd have to pack things if you wanted to make an Earth-mass black hole. For a pair of protons smashed together at high energies - as in the LHC - I think you need to bring in other areas of physics than just general relativity. Suffice to say the Schwarzschild radius would be much, much, much smaller than the size of a proton, which in turn is much, much, much smaller than the size of an atom, which is much smaller than the distance between atoms in most solids. So in order for a micro-black-hole to accumulate mass, it would need to pass very close, on the order of its Schwarzschild radius, to the nucleus of another atom. At the length scales we are talking about, that's about as likely as me randomly shooting off a bb gun and hitting a passing bird a kilometer away.

      So rest easy, the world isn't about to end.

      I apologize for the long answer, but I hope it has answered your question.
    • by ChowRiit (939581) on Friday November 13, 2009 @10:07AM (#30086144)

      A black hole is any body tightly packed enough that its escape velocity is greater than the speed of light. Because material, as a result of this, can ONLY travel towards the centre of mass (outward travel, sideways travel and staying stationary are all forbidden this therefore HAS to form a singularity, as matter is all forced to head towards and occupy a single point.

      The distance from the object where the escape velocity drops below the speed of light is the event horizon (aka the Schwarzschild radius), within this sphere* no light can escape so we call this sphere the black hole. In the centre of it is the singularity, which is the "true" black-hole.

      All objects have Schwarzschild radii, however this radius is only a "real" radius if it exceeds the radius of the object. Wikipedia claims the Schwarzschild radius of the Earth is 9mm, so Earth would form a black-hole itself if it were compressed to smaller than 9mm in radius.

      The key point is that a "black-hole" is not an object, per se, but a region of space from which light cannot escape. The "object" would be the singularity in the centre. From outside the black-hole, there's no real difference from a star of the same mass in terms of gravity.

      *rotating black holes have a slightly different shape, depends on the speed of rotation.

  • What people don't realize is that this study was funded by companies that produce black holes.

  • Well... (Score:2, Funny)

    by hyperion2010 (1587241)

    This sucks.

  • can we use a micro-black hole to power a stargate? as ZPM's are hard to find.

    • by ChowRiit (939581) on Friday November 13, 2009 @10:30AM (#30086424)

      Black-holes are not a source of energy (excluding the monumentally tiny energy output via Hawking radiation), any energy gained harnessing black-holes would be from the accretion disk around them in which particles accelerating towards the black-hole emit radiation due to friction among themselves. However, you'd likely need a stellar-mass black-hole to get a realistic accretion disk going.

      Anyway, ZPMs aren't hard to find, you just need Ancient-built replicator civilisations or time travel.

  • by MacAnkka (1172589)
    Am I the only one who reads MBH as mega black hole, not micro black hole? It's confusing. If the prefix is micro, it would make sense to use a letter that actually means micro, instead of a letter that represents mega.
    • by ChowRiit (939581)

      It is somewhat confusing, I agree, as the greek letter "mu" normally represents micro, and "SMBH" is the normal acronym for Super Massive Black Hole (black holes at the centres of galaxies that weigh millions of times the mass of the sun).

  • Sam Hughes will be so disappointed

  • Come on guys, this is not rocket science!

  • used a time machine made with mini black holes, in case you guys have forgotten..

  • by RealErmine (621439) <commerce@@@wordhole...net> on Friday November 13, 2009 @10:40AM (#30086592)
    I'm more worried about the possibility of a resonance cascade.
  • ...where it will evaporate...

    I'm no physicist, by any stretch of the imagination, but black holes "evaporating" just doesn't sound right to me.

  • Been Done (Score:5, Informative)

    by DynaSoar (714234) on Friday November 13, 2009 @11:01AM (#30086822) Journal

    TFA calculates the likely results based on higher dimensional brane physics. It was done earlier in more classical relativity maths and the results summarized in Alan Boyle's Cosmic Log. The max mass was greater and thus life time longer. Still, mass and accretion never crossed the limit that would allow it to reach whatever they call critical mass for these thing. The example given was that if it were charged and it were trapped within the electron cloud of an atom (both conditions lending it additional life span), it would circulate there on the order of weeks before encountering an electron which it could then consume. Even if it did so it would evaporate before it could hit the run away point, and would likely evaporate before eating even one electron. The specific results were different but the conclusion the same - too small to live long enough to do any damage.

    Another point made in Cosmic Log (I don't recall if it was the same person/calculations) was that quantum black holes (a more correct descriptor than 'mini-') of the mass and life span hypothesized would be likely to occur regularly in the atmosphere due to incoming primary cosmic rays. Those have been impacting the Earth for billions of years, and we're still here. The hypothesized Hawking radiation is not obvious, thus these may not even be occurring. In any case, their creation would be a highly improbable event.

    That last assertion is strictly conjecture based on calculations by my Brambleweeny 57 sub-meson brain. Now if you'll excuse me I'm for a nice hot cup of tea.

  • by arthurpaliden (939626) on Friday November 13, 2009 @11:26AM (#30087128)
    A week before they turn it on to produce the MBH and destroy the Earth I will buy anyones home for 5 cents on the dollar so they can spend their last week in a continuous state of Party.
  • by jameskojiro (705701) on Friday November 13, 2009 @01:35PM (#30088750) Journal

    I think the LHC has destroyed the world multiple times now. It is just that we here and now are the survivors of the disasters....

    According to the Multi-verse theory, each quantum fluctuation creates a new universe or timeline.....

    Because we are alive and well and not consumed by a black hole, that means in "our" branch of the multiverse we haven't created a Black Hole that swallows earth "yet".....

    But fear not because Even if the LHC were to create a earth consuming black hole, strangelet, way to lower the energy level entire universe leading to it's immediate destruction. We will survive because at least one branch of timeline will survive by failing to create these anomolies and go on to branch out some more to survive whatever weird physics experiments we dream up of go arwy.....

    The only problem is when creating black hols and exotic matter that is large enough to reduce quantum probability and then we are really screwed.

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