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Science

Optical Black Holes in the Lab 194

Posted by jamie from the don't-talk-to-me-about-dumb-holes dept.
spaceorb writes "According to researchers ... it may be possible to create black holes by creating a vortex of fluid that swirls at velocities comparable to the speed of light. Follow the above link for the theoretical discussion or here for the story on unisci.com." These are optical analogues of black holes, not really gravity wells, but they may advance our understanding of the real thing.
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Optical Black Holes in the Lab More

Optical Black Holes in the Lab

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  • Re:This is why Science is dangerous. (Score:1)

    by Anonymous Coward
    I suppose the Church felt the same way when the light bulb was invented. Also when they discovered electricity and when they figured out that the earth was not flat. "you can't go beyond the ocean. You will fall into the abyss". I reccomend some restrainment first of all. First and foremost if the scientists felt they would wipe out the whole planet they would not go ahead with something like this. After all they ARE humans too with families and friends and everything that goes with being human. Secondly unless you TRY and discover you WILL NOT discover. Thirdly if you read some theory on black holes ( i reccomend stephen hawkins works) you will find out that a black hole with mass 1g is just THAT. A black hole with 1g. DISPITE popular beliefe black holes do NOT suck matter in them and grow larger. In fact if the SUN turned into a black hole tomorrow the earth would still be where it is today. It would not get "sucked in".

  • Re:Velocity is relative (Score:1)

    by Anonymous Coward
    Aargh. No. That's the point of relativity. No matter how you do it, light always goes at the same velocity. The observer's perception of mass, length and time adjusts to maintain this...

  • Superfluid black holes (Score:1)

    by Anonymous Coward
    Related subject: Jacobson and Volovik have done some work on making superfluid black hole analogues [arxiv.org] instead of the optical ones being discussed here.

  • Light (Score:3)

    by Anonymous Coward on Tuesday February 01, 2000 @08:02AM (#1316426)
    The actual speed of the photons is not reduced going through a medium. (this is the part of relativity) What is reduced is the apparent speed to an opserver (an important distinction). This is due to collisions with particles and fields that misdirect the photon along a much longer path through the object. (I know this is a very elementry explaination, but I fear going deeper)

    What this vortex will do is make that path of misdirect infinitly long (ie a cirle like). Therefor the photon will never make it back out.

    This is 'simular' to the idea of refraction in optical cable, the material is such that the light is always refracted back within itself (if it enters at a certain angle). what the vortex does is make a circular optical cable with prefect refraction trapping all light within itself. (I know this is an over simplification)

    Gork the Enchanter
  • I still only have 5Gigs of storage. Shared over 3OS's on 2 computers.

    1.4Gigs of its MP3s too.
  • And copper acts as a waveguide for EM waves. Thats why he said 'light' as it doesnt necessarily mean visable light.
  • If only :)

    I expect you could make a 'sonic black hole' using the same idea as this one, but the trouble is that this method doesnt seem to SUCK the light in like a gravitational black hole does. It has to hit part of the vortex to be captured.

  • I'll believe it when I see it (Score:3)

    by Yarn ( 75 ) on Tuesday February 01, 2000 @04:08AM (#1316430) Homepage
    "You wont"
    "doh!"

  • Someones been watching too much TV :-)

  • Gotta be:
    "A tornado, for example, attracts with ease substantial ``test particles'' such as cars"

    :-)

    dylan_-


    --

  • Physics is...not my strong suit. I don't claim it to be so, I'm not an expert in this field, I'm an outside observer that just has a few questions...

    For one, exactly how do they propose to keep the water in liquid form?

    Water remains liquid only at certain temperature/pressure ratios. Creating a vortex rather quickly creates large pressure differentials(almost by definition), and dumping light into something that isn't going to be able to spit it back out is going to increase temperature. How is the entire mass going to be kept in that one relatively small range that keeps the material liquid? Granted, an excessively smooth container might allow superheating of the fluid(water cannot boil unless there are microscopic ledges upon which bubbles may form, apparently), but having this fluid in contact with *any* other substance is going to create seriously ugly amounts of heat by way of friction.

    Even supposing one could accelerate such a material to near-luminal speeds, at minimum a Zero-G environment and a vacuum would be required.

    But that's one heck of a supposition! Assuming a massive objects could be spun at such extreme rates is...generous. Am I wrong, here?

    I must also ask where the concept of absorption has gone. For a while there, I was imagining they were describing a merger between fiber optic cable and a roach motel--light got in, then was forced to spin round and round the vortex forever. But who said that the water would become instantly clear? As it spun around, wouldn't more and more of it be converted to heat until there was no light left? I'm not slowing down light if I move it through a fiber optic cable that's a kilometer long but on a spool only a foot thick. The light still moved a kilometer, even if (from my "perspective") it only moved a foot. But fiber optic cable is very transparent; water isn't nearly as such--particularly water that bubbles and is highly agitated.

    And how would light enter the system if the outside walls of the vortex were so particularly
    chaotic? This part, I'm really missing.

    Something just seems...wrong here. Someone care to clue me in?

    Yours Truly,

    Dan Kaminsky
    DoxPara Research
    http://www.doxpara.com
  • the speed of light in vacumn is always constant. As light is just a traveling electromagnetic wave it can be retarded by a material it is travelling in
  • Its not a black hole. It is an optical black hole which just means that light gets stuck in this vortex. It will no more emit hawking radiation than a mirrored room (which hence traps light). This vortex is not gravitational does NOT slow time or any such thing.
  • .... When can I Order my own TARDIS [tardises.gf]???

    ;)

    Your Working Boy,

  • It seems to me that there are some tricky special relativity thingies that these guys are forgetting.

    Roger.
  • > Next, it only takes an infinite amount of time
    > for a particle to cross the event horizon from
    > the outside perspective of an observer who is
    > not falling into the hole. To the particle or an
    > astronaut falling into the horizon, the trip is
    > quite short. Therefore, to say that black holes
    > only exist asymptotically is incorrect.

    Two frames of reference:

    From the perspective of the outside observer, what occurs is as described, the infalling object (albeit ripped apart tidally) slows and asymptotically approaches the event horizon, which over a very long but finite time shrinks until it vanishes.

    From the perspective of the infalling observer, (which has been torn into subatomic particles and radiation by the tidal forces), it seems to cross the event horizon without delay -- except that there is no event horizon any more. During the short trip, the black hole has evaporated, and all the particles which had at one time or another been gravitationally captured outside the event horizon will be now "emitted" where the hole has just ceased to exist (but billions of years later from the perspective of outside observers).

  • Asymptotic Black Holes (Score:3)

    by whig ( 6869 ) on Tuesday February 01, 2000 @02:19AM (#1316439) Homepage Journal
    It will be interesting to see whether they can actually create an "optical black hole", or just asymptotically approach one. Assuming that Hawking is correct, and that black holes emit a quantum radiation which reduces their mass as one-half of a particle/antiparticle pair escape, evaporating in a finite time, and considering the time dilation which requires an infinite time for a particle to actually cross the event horizon, then black holes only exist asymptotically. That is, trapped particles move inward as the event horizon shrinks, and cross it only as it evaporates.
  • Lord, can somebody teach those physicists the concept of the paragraph????
    --
    " It's a ligne Maginot [maginot.org]-in-the-sky "
  • So if you swirl the stuff at the speed of C in the substance, it should glow nice and blue due to Cherekenov (spelling probably out) radiation, which happens when you accelerate matter through a medium faster than C in that medium. It just dumps the energy as photons.

    C = speed of light.
  • I wonder if it is a mistake or volontary ?
  • No, it's not. The 'light'speed in copper for example is about 200.000 KM/s. Which is darn slow when you're trying to maximise cable length on a 100 Mbps network...
  • True, but I suggest you go back and read a little Einstein. That is the whole concept, the velocity of light is a constant.

    Special Relativity.
  • Conservation may or may not work inside a sigularity or it may be transmitted to another point in this usniverse or another one. Since (luckily) we don't have any close singularities we haven't been able to study what happens inside them. It's very possible these photons are slowed down to an almost absolute stand-still (like in a Bose-Einstein condensate) and are actually accepted into the singularity as more mass. The energy of the photon increasing the energy of the singularity but the increased mass of the singularity counterbalances the energy inserted into the singularity. That would make it theoretically possible for conservation to work within a singularity. Singularities don't suck in light like a vacuum, they warp space-time and bend the path of the light into infinite vortexes. Light whose path isn't bent 100% would be sent off in on a tangent of the event horizon if it didn't smack through the matter swirling in the event horizon.

  • Re:Hmm (Score:1)

    by Tim C ( 15259 )
    ...unless, of course (as it states in the article), the dielectric constant of the fluid is sufficiently high. In that case you need only accelerate the fluid to a relatively low speed to achieve the same effect.

    As for the comment about centrifugal force, if the fluid were (say) contained inside a closed cylinder, which it nearly filled, it would have nowhere to go, and so, no way to break up. (Although that may not be a problem anyway, if the dielectric constant is sufficiently high; they mention materials which reduce the speed of light down to a few metres per second...)

    Cheers,

    Tim
  • A black hole (in the sense of a gravitational black hole) actually destroys the photons etc.

    No, that is not possible; conservation of energy expressly forbids such a thing from happening. In this case, as in all others, the energy is simply converted to some other form.

    As for a brick being the same thing, that is also incorrect. The difference is that even the brick reflects light, otherwise you would be unable to see it. A black hole, however, not only does not reflect any light at all, it actually "sucks in" light that strays too close. In the case of the "fluidic black hole", presumably any light that strays too close to the vortex will similarly be sucked in.

    Cheers,

    Tim

  • Re:Maintaining Liquidity (Score:3)

    by dillon_rinker ( 17944 ) on Tuesday February 01, 2000 @05:26AM (#1316450) Homepage
    As another poster indicated, they are using a Bose-Einstein condensate, not water. I believe that a Bose Einstein condensate was used in the last year to slow the speed of light passing through it to some ridiculously low value, like 38 miles per hour. If this were the speed of light in a particular medium, then it wouldn't take too much to make the medium go faster than that.
  • Almost right.

    The velocity of light in a vacuum is constant. Most of the time, the speed of light in an object is usually only fractionally smaller than the speed of light in a vacuum, and as a reuslt the difference is usually ignored to simplify things for the person doing the mathematical calculations (physics classes, for instance).

    However, there are certain exotic materials and methods that can be used to slow the speed of light down drastically. This would be one application of those materials/methods.

  • > It will no more emit hawking radiation than a mirrored room (which hence traps light). This vortex is not gravitational does NOT slow time or any such thing.

    From the Article:

    "Since light in an optical black hole would behave analogously to matter in a real black hole, these light-trapping whirlpools would permit laboratory study of Hawking radiation, the hypothetical emissions from evaporating black holes; this radiation, which consists of particles made near the hole's boundary, is next-to-impossible to observe directly since it is obscured by the cosmic microwave background."

    The article also mentions that they are using condensates, the same stuff that slows the speed of light to around 38 miles per hour (to an outside observer). Now, since c is a constant, that means that the conditions in the condensate are either such that 1) distance has increased, or 2) time has slowed down. So, it probably does slow time down as well.

    --
    Evan "If people would read the articles, 75% of the content on /. would be eliminated".

  • I think it's more along the lines of this...
    Light is *not* a constant speed, it is only a constant for a given energy density of space.

    When light travels through air, or water, it slows down (albeit not by much).
    I Think the theory goes that if you make it pass through a gas with a very high density.. it slows down even more.. and a BEC (Bose-Einstein Condensate) I believe can be used to create a gas or other transparent material with a very high energy density (BEC, if I recall, is basically a whole bunch of atomic nuclei stuck together acting like one large atom.. something like that).
    If this density is high enough, and the material is trasparent, in theory the speed of light throug the material could be slowed extremely.
    You are right, though.. they will make a whirlpool spinning at near light speed because they have slowed the speed of light ;)



  • This could lead to effective miniblinds?
  • take a stick and put one of those black holes at one end and a handle with laser emitters all around at the other end. Set the laser freq. at the proper freq. of the black hole and point them at the singularity...
    Tah dah!!! you made yourself a nice lightsabre!!!
  • it's hilarious and informative.
  • Well, perhaps not the optical black hole but this idea from the article: In the meantime, physicists are also pursuing the idea of creating "acoustical black holes" (dumb holes), regions that capture and trap sound waves. could come in very handy indeed.

    Need some peace and quiet? Try our new Portable Model NahNahNahICan'tHearYou(tm). Used like a normal Walkman(tm), this portable version of the ABH frees you up from all those irritating sound waves you didn't want to hear! Relax and read the paper while standing next to a jet engine! Experience the complete peace of space without the millions of dollars in training needed to get there! Selectively eliminate the sounds of barking dogs, crying children, nagging spouses, co-worker PC startup WAVs and more!

    If you live near an airport, why not ask for a free demonstration of our mid-size Dead Quiet(tm)- suitable for all single-story residences. Eliminate those pesky sound waves from passing jets and imagine you're at the quiet country house you couldn't afford in the first place!

    * It is not advisable to operate the NahNahNahICan'tHearYou(tm) Portable Personal Accoustical Black Hole while operating machinery or driving. ABH Technologies Limited does not endorse standing next to jet engines during operation. Example used for illustrative purposes only.

  • They never said water, what they said was

    "a Bose-Einstein condensate or a rubidium gas"

    -NF
  • Bricks do not produce Hawking Radiation. It's that quantum effect that makes this experiment exciting and unusual.

    Hawking radiation originates in the background of virtual particles in the universe -- particles that appear spontaneously from nothing along with their antiparticles, then collide and exterminate themselves. This background energy is a vital part of our models of the universe.

    Stephen Hawking theorized that near a black hole some these virtual particles would be sucked into the black hole while their antiparticles would remain free. Thus, some virtual particles become permanent and real particles, and the black hole effectively radiates them into space. Conservation of mass states that the black hole must then be shrinking slowly in size...but that's not important here, with the laboratory optical black hole.

    The optical black hole will have the same effect as a real one; virtual particles will be trapped within it, and their antiparticles will fly free. (Note that the trapped particles may be either matter or antimatter -- the radiated particles will be the opposite of the ones trapped.) Scientists will then be able to measure this Hawking Radiation and test some very central theories of cosmology and quantum physics.

    Theoretically (and there's a point at which the theory is so remote, it's only fantasy...but here goes), an optical black hole *might* be configured to collect the radiated antiparticles as a bose condensate themselves. Then the optical black hole serves a purpose -- it's an antimatter generator. But that's really, really far beyond what they're trying to do now.

    ...
    Remus Shepherd
    Yes, I am a physicist. Yes, I do play one on Usenet.


  • yes. transparent metals are being worked on at DARPA.

  • Light is *not* a constant speed, it is only a constant for a given energy density of space.

    This is not quite correct. The speed of light in a dielectric depends on the index of refraction, n, of the medium; n is in turn a function of the magnetic permeability, mu, and dielectric constant, epsilon of the material. At the root of it all mu and epsilon are functions of the molecular and electronic structure of the medium, as well as the frequency of the light itself. Thus, two materials with similar densities but very different dielectric constants will have very different indices of refraction, and hence light will propogate within them at different speeds. What's more, even for a single material, n (and hence the speed of light) will in general vary with wavelength. This is called "dispersion", and it is responsible for such diverse phenomena as rainbows, prisms, and smearing of pulses from pulsars.


    The important thing to remember is that only the speed of light in vacuo functions as an absolute "speed limit". Particles can and do exceed the speeds of light in dielectric media, causing them to emit Cerenkov radiation in the process.


    -r

  • I'm not sure what you're getting at. I don't doubt that the effects on photons look similar to the effects of Kerr black holes on photons. However, the authors mention studying Hawking radiation in the laboratory as a possible application of the effect. That's not going to happen unless the system also affects matter the way a black hole would, which in fact it does not. There is a shallow analogy between the two in that the equations of motion for photons are similar, but the authors suggest that the analogy goes much deeper than that, and I doubt very much that it does.


    -r

  • The rigorous explanation for why materials are or are not transparent is a little hairy, but here's an explanation that, while a little oversimplified, captures the flavor of what's happening


    Imagine you have a lump of some material. The electrons circling the atoms or molecules of the material have some characteristic structure that depends on the elements involved, how the electrons are shared in any molecular bonds in the material, and how the atoms or molecules are arranged in the bulk material (proximity of other atoms or molecules distorts the energy levels for orbiting electrons). This latter factor, by the way, is the difference between coal and diamond.


    Now, along comes an electromagnetic wave, which is really just an electric field oscillating with a magnetic field. The electrons in the material are going to feel a force due to the E field (in this naive treatment we'll ignore the magnetic field). What's more, that force will want to drive the electrons to oscillate, but those oscillations will be resisted by forces that depend on the factors I mentioned above. The punchline is that the more the electrons are free to respond to the electric field's driving force, the more energy they will dissipate, the more the incoming light will be attenuated, and hence the more opaque the material will appear. Conversely, if the electrons are not free to respond, the light is not attenuated (much) and the material appears transparent. As you might expect, for any given material the response of the electrons varies greatly with frequency (just like the case of mechanical resonators). This gives rise to all sorts of phenomena, which you can find described in any good optics text.


    Now, in the case of conductors (like metals) the electrons are very free to move around (that's what gives them their conductivity), and hence you would expect them to quickly dissipate any electromagnetic waves incident on them, and that is generally the case. Typically the ``skin depth'' for metals is about 1/6 of a wavelength. However, as you go to higher frequency, things get complicated again, because the conductivity has a wavelength dependence. Generally that dependence takes the form of a strong drop off in conductivity above some characteristic frequency. Evidently, this characteristic frequency is well above visible light frequencies for naturally occurring metals.


    Another poster mentioned that DARPA is working on transparent metals. Presumably, then, their line of attack is to try to find some alloy with a crystalline structure that makes that alloy's characteristic frequency lower than visible light frequencies. If and when they succeed, it will be interesting to see what that does to the metal's other characteristics like malleability and ductility.


    Hope that helps (and I hope I didn't post it too late for you to get back around to reading it at some point).


    -r

  • Re:Hawking Radiation. (Score:3)

    by Robert Link ( 42853 ) on Tuesday February 01, 2000 @11:22AM (#1316464) Homepage

    The optical black hole will have the same effect as a real one; virtual particles will be trapped within it, and their antiparticles will fly free.

    I am skeptical that these "optical black holes" will trap particles as well as they trap light. Particles have no problem traveling faster than the speed of light within the dielectric, so long as they do not exceed the speed of light in vacuo. Thus, particles should be able to escape these things, even if light cannot. In other words, these beasts have no true event horizon, and so any analogy to astrophysical black holes is suspect.


    Robert Link

    Also a physicist. Gave up on Usenet a long time ago.

  • Authors hung up on "not even light can escape" (Score:4)

    by Robert Link ( 42853 ) on Tuesday February 01, 2000 @12:28PM (#1316465) Homepage
    The authors appear to think that the salient property of a black hole is the pop science description that "not even light can escape its pull." Thus, they reason, if light cannot escape, it must be a black hole. This just isn't the case. Indeed, the authors' own text hints at this: "The concerned reader should note that optical black holes are safe. They would attract only light..." This property is, of course, fundamentally different from what you expect of a true (that is, astrophysical) black hole, and so we should be skeptical of any further analogies between these "light traps" and black holes. In particular, I see no reason that these things should emit Hawking radiation. Certainly the "virtual particle trapped inside the event horizon" interpretation of Hawking radiation fails because there is no event horizon.


    What's more, from the standpoint of General Relativity these constructs don't look anything like a black hole. The stress-energy tensor (the relativistic analog of mass density) is virtually unchanged by the modest rotational flows light traps made from Bose-Einstein condensate would require, meaning that these constructs should have exactly the gravitational properties you would expect of a static body of liquid in the laboratory (i.e. none to speak of). That means no space-time curvature, no ergosphere or frame dragging, no gravitational redshift, and no time dilation. For example, if they directed a stream of muons through these things they should find the muons' decay lifetime basically unchanged from what it would be if they sent the muons through the same liquid while it wasn't rotating.


    I believe the authors make an important mistake when they say "... a moving dielectric medium acts on light as an effective gravitational field." That is clearly not true because this putative "gravitational field" does not obey the equivalence principle; viz. it accelerates light but not matter. The mistake is comparable to saying, "A charged pith ball in an accelerating train car will experience an `effective electric field' which will tend to accelerate it." and proceeding to compute the electromagnetic properties of this moving field. The analogy falls flat because the acceleration is not caused by an electric field, and so it can't be expected to act like one when you study its influence on anything else in the train car. Similarly, although you can compute a gravitational field that would trap light in the same way as these constructs, that doesn't mean that there is actually a gravitational field present, nor does it mean that other effects that would be present for the gravitational field you calculated will actually show up in your apparatus.


    None of that means that this isn't interesting research, of course, but as far as I can tell the connection to black holes and astrophysics is nonexistent.


    -r

  • Thing is, a 1g black hole will be *very* small indeed, probably (and I haven't done the math) smaller than elementary particles, which means even if it were stable (no hawking radiation), it would be unlikely to actually intersect any matter. So, if you dropped it through your table, you could probably wait for it to come back to you, as it will enter a free orbit at this point, and won't mysteriously stop at the center of the Earth. A larger black hole (large enough to actually absorb something), might be slowed by passing through the Earth (but, thinking about this, it might actually speed up until it left the atmosphere. Friction doesn't apply to event horizons, y'see, so the only force that could slow it down would be gravity. Now, you have two orbitting masses, one of which is gaining mass from the other, and the fact they intersect is irrelevant...)

    You wouldn't be worrying about this anyway, because a 1g black hole would rapidly release rather a lot of energy as it evaporates (E=mc^2...), so you'd probably have some rather more exciting problems to work on... (Like how to reattach severed limbs)

    Andrwe.
  • "about 200.000 KM/s"

    uhm, ok, let us review significant figures. You just quoted a number to six decimal places, or one part in 400,000, but prefixed it with the word "about."

    It occurs to me that you could be using "." to mean "," but if you want me to accept that, you had better use the correct abbrviation for kilometer, which is km, not KM (Kelvin Mega?).

    As others have said, you also oughta be more precise when you talk about light speed in an opaque medium.
  • Oh come on "-1, troll," it is so obviouly a joke.
    Any culture that cannot laugh at itself does not deserve to exist.
  • People with high karma get automatic +1's to any comment they do not specifically designate "No Score +1 Bonus." That's why there is no reason specified for his score.
  • My guess is that if the black hole you dropped into the earth were big enough to have a net gain in mass as time progressed (ie it is not evaporating faster than it eats), then you would not get "a century or so." Since the growth of the hole would most likely be fit by y=x^x or some other god-awful function, we'd either be completely safe, or quickly dead.

    On the other hand, I am basing this on almost no information. Can anyone point us to a well thought out mathematical model of this?
  • You are right, if the sun turned into a black hole, Earth would go on happily orbiting because the gravitational effects out here would not change. [Perhaps the added spin of the sun would make a bit of a difference, but I don't know what is conserved in this case]

    However, there is a large difference between a 1g block of steel and a 1g black hole if you are trying to keep it sitting on a table [or in any other non-vacuum]. The steel and the hole will have the same gravitational effect if you are 2cm away from the center of each, but anything very close to the hole WILL get sucked in, because the gravity DOES make the escape velocity rise to above the speed of light as you move towards it. If you "set" your 1g black hole down on the table, it would not and could not be supported and would fall straight thru any matter in its way until it got to the center of the earth. As it went and once it was there, it most definitly continue to suck matter in. Perhaps the rate of suck would be very small at first, since particles have to get real close in order to be trapped, but the more that it eats, the more it sucks.

    On the other hand: A 1g black hole would evaporate (read: explode) very quickly due to hawking radiation.

    And: They are not making black holes anyway, that is just an analogy, RTFArticle.
  • Good point about it not stopping at the center. I never thought of that, and I think a whole lot of science fiction writers miss it as well.

    At some point I will do the math for [1g black hole versus density of particles it will encounter] and [time it takes to explode due to hawking radiation], but right now I am too overworked already.
  • > No,but seriously, even if you could create a > conductive core which could touch a black hole > (precisely on the event horizon) any electricity
    > would instanty be consumed by the hole itself; > or rather the matter entering the hole > (electrons being a component of matter but
    > inexistent without it)

    But that's exactly the point... electric charge is always conserved. If electrically charged matter enters a black hole, the black hole must now have electric charge.

    An even better way to charge a black hole would be simply to set up a bunch of electron guns, and shoot at the hole for a while. Eventually it'll get a charge, at which point some magnets would be just fine in moving it. True, it'd have a huge inertia, but it'd move.

    In general, true black holes (not these optical ones) have 3 properties:

    1) Mass
    2) Charge
    3) Angular momentum. (i.e. spin)

    All other information disappears.

    Thus the saying, "black holes have no hair"

  • Well, it seens it is always the samething.
    Today, they build the dam thing in a Lab. Next week, you will be able to buy one of them for a couple thousand bucks at ebay. Them they hit the shelves at Amazon and other places...

    In a year or so they will be comming free with your favorite breakfast cereal...

    Hmmm...I think that not even Galactus would have dreant of that. Should make a nice sauce to go with planets.

    Of course they had already had the technology to do this on the past [slashdot.org], but it seens they had improved something on security since.
  • I think that you are trying to be funny, but just in case its not that (or for clueless moderators): The speed of light in a given medium is constant. When light will switch over from one medium too another, it will merely refract. So no BSOD, because the light will be swapping media, and refracting to account for the swap.
  • It would be even better if you could magnetically
    hold the vortext a certain distance from the laser
    handle, that way you wouldn't have to worry about
    the stick getting caught on something if the
    laser didn't cut fast enough :)
  • If you shine a bunch of light into one of those and then suddenly make it stop spinning, what happens?

    --

  • What happens when you turn it off? Does all the light that was trapped come back out and burn everything around it? Sounds nasty to me.

    Where is my mind?

  • Re:Scares the hell out of me! (Score:3)

    by CausticPuppy ( 82139 ) on Tuesday February 01, 2000 @04:15AM (#1316479)
    Read the article! They're NOT making a black hole, it's just an optics experiment. They want to study the effect of light in a moving medium, where the speed of light in that medium is very slow. They won't even have to "stir" it that fast. The worst that could happen is that, as more photons pile up at the "event horizon", where they will eventually just be absorbed by the medium and converted to heat, it will raise the temperature of the bose-einstein condensate enough to undergo a phase change (back to regular old cold rubidium atoms, I suppose). There may be a dim flash of light during the phase change... just a guess.
    The whole experiment is about as dangerous as playing with a laser pointer.
  • c is only a constant in a vacuum. The speed of light slows down in other media due to refraction. The distance hasn't increased nor has time slowed down. Light is just slower in other media.

    There would, however, be a localized time dilation effect in a vortex medium that was moving at near-c velocities.
  • The flash......
  • ...who exactly is going to stir this liquid at the speed of light?
  • Through a mirale of modern science we have found what to do with all those AOL disks
  • I beleive the comment you're referring to is this:
    Consider a specific example of a flowing fluid, a vortex. Such a vortex is frequently spontaneously formed when water flows out of the drain of a bathtub. (The common myth is that the bathtub vortex rotates in one direction on the northern hemisphere and in the opposite direction on the southern part of the globe, which is wrong.)


    Unfortunatly this opinion is backed up by other sources: Bad Coriolis [psu.edu]
    The direction of rotation of a draining sink is determined by the way it was filled, or by vortices introduced while washing. The magnitude of these rotations may be small, but they are nevertheless gargantuan by comparison to the rotation of the earth
    And for the Simpsons fans out there...[2F13] Bart vs. Australia [snpp.com]
    I thought Lisa knew better: Coriolis effect does NOT determine which way the toilets and sinks drain.
    [...]The Coriolis Effect
    This is a real effect, but it isn't strong enough to affect the direction of water flow down a sink or bathtub. Any claims to the contrary are urban legends and can be scientifically refuted. Please consult the sci.physics FAQ for more information.


    There are other sources - check Google [google.com]. Of course there are probably sites out there that encourage the myth, but that's the nature of myths.
  • In answer to your question I agree it's a myth. In defence of including the first link - all I did was to include two random links - maybe not a good idea in view of the reaction it received.

    From the 2nd link, it refers to the sci.physics FAQ - which I hope would be a reputable source of information: Which Way Will my Bathtub Drain? [ucr.edu]
    Question: Does my bathtub drain differently depending on whether I live in the northern or southern hemisphere?

    Answer: No. There is a real effect, but it is far too small to be relevant when you pull the plug in your bathtub.


    wrt your comment on the author of the first site, I'm inclined to agree.
  • RECIPE FOR MENTAL BLACK HOLE:

  • There is actually:

    Black holes can be electrically charged, and can therefore be moved using magnetic fields.
  • It would be rather amusing if they managed to create one and it started sucking down everything we know. That would rock.

  • Optical Black Holes reference:

    U. Leonhard and P. Piwnicki, Physical Review Letters, 84, 822-825(2000).

    This is the actual reference to the paper proposing optical black holes. It has been published in what is arguably the most respected physics journal(not some speculative rag). Many of you are asking about a material in which the speed of light is very slow. Such a material was demonstrated last year:

    L. V. Hau, S. E. Harris, Z. Dutton, and C. H. Behroozi, Nature(London) 397, 594(1999).

    In this paper Hau et. al. demonstrated that light traveling through a Bose Einstein Condensate is slowed to a mere 17 m/s. This is slower than most bicycles ride(as illustrated by the cover of that weeks nature). To find out what Bose Einstein Condensate is you can refer to:

    Anderson, M. H., Ensher, J. R., Matthews, M. R., Wieman, C. E. & Cornell, E. A. Observation of Bose-Einstein condensation in a dilute atomic vapor. Science 269, 198-201 (1995).

    Now go to your local University Physics Library and look a few of these things up before advertising your ignorance and pronouncing that this is bullshit just cause you read some bullshit article on real science

  • ... if you would you would understand, that it's not a real black that will be created but something that will have similar behaviour... Jeez,... its those scientist you seem to distrust so much that've told you all they suppose about black holes. They're the ones who make back of the envelope estimates. Yet you think you (clearly someone who gets all his knowledge from SF-comic books or movies) understand the dangers better than they do,... oh puh-lease, If you know nothing, understand nothing and have no clue whatsoever what you are talking about just shut up will you... (Oh yeah, real (wo)men post their name) J.
  • ... if you would you would understand,
    that it's not a real black that will be
    created but something that will have
    similar behaviour...

    Jeez,...

    its those scientist you seem to distrust
    so much that've told you all they suppose
    about black holes. They're the ones who
    make back of the envelope estimates. Yet
    you think you (clearly someone who gets all
    his knowledge from SF-comic books or movies)
    understand the dangers better than they do,...

    oh puh-lease,

    If you know nothing, understand nothing
    and have no clue whatsoever what you are
    talking about just shut up will you...

    (Oh yeah, real (wo)men post their name)


    J.

    P.S. sorry messed up lay-out last time
  • Lawyers have found a way to create black holes on the "internet" by creating a vortex of lawsuits that swirls at velocities comparable to the speed of information.

    "We are very exited by this" says a spokesman for the Unmoving Picture Association "Maybe it is possible to create a device so that information cannot escape its proximities, or at least bend over"

  • If an optical black hole can be created by passing light through a medium that causes the light to slow down relative to the speed of the vortex, does this mean that the observed effect (specific-frequency light can't escape) is caused completely by the vortex? This could lead me to believe that a REAL black hole only creates a gravity well because it creates such a strong vortex in the medium of spacetime. This may already be the common belief of black holes, but I always thought that a black hole was just a massive point in space that sucked stuff straight into it and matter falling into it followed the path of a vortex. Could it be that the gravity well surrounding a singularity is CAUSED by the vortex action around it?
  • Making black holes scares the hell out of me anyways, so I don't think it's interesting at all.
  • Of course, users of modern universes will gleefully point out that, in theirs, light rarely actually swaps -- it pages using an LRU algorithm.

    Just through enough storage at it, and it won't ever swap. 640 kilophotons should be enough for anyone.
  • So no BSOD, because the light will be swapping media, and refracting to account for the swap.

    Of course, users of modern universes will gleefully point out that, in theirs, light rarely actually swaps -- it pages using an LRU algorithm.

  • Destruction of the Universe Possible? (Score:3)

    by cburley ( 105664 ) on Tuesday February 01, 2000 @06:26AM (#1316497) Homepage Journal
    The velocity of light in a vacuum is constant. Most of the time, the speed of light in an object is usually only fractionally smaller than the speed of light in a vacuum, and as a reuslt the difference is usually ignored to simplify things for the person doing the mathematical calculations (physics classes, for instance).

    However, there are certain exotic materials and methods that can be used to slow the speed of light down drastically. This would be one application of those materials/methods.

    Then it sounds like this experiment, modified, could result in the instantaneous destruction of the universe:

    First, get the light within the artificial vortex to slow down.

    Then, place the device containing the experiment within a good-quality vaccuum, like an Electrolux (or an old VAX).

    At that point, the light within the experimental device has a problem -- it's supposed to go the speed of light 'cause it's in a vaccuum, but it's supposed to go slower because it's going through some other materials.

    The result of this contradiction might be the immediate destruction of the entire universe, followed by some quick behind-the-scenes fixing of microcode bugs and a reboot. (This sort of crash is known by the heavenly hackers as a "BSOD", or "Black Suck of Death".)

    (Or, we might just learn which if these "laws" is wrong!)

  • Why don't they work on something that will suck up all the silly comments on /. so then noone has to worry about Moderation and Meta Moderation and all that.

    How do we do this?
  • You seem to be confused. Yes, both say a sealed box and an optical "black hole" stop you seing light in a basic sense, there are large diferences that you seemed to have missed.

    A black hole (in the sense of a gravitational black hole) actually destroys the photons etc. as they enter it. A box simple stops the light getting to your eyes. The light is still in that box, and it would eventually be converted into other energy forms (I.E heat).
  • Well, i suppose i was close. Must remember to get hold of a copy of Dr Hawkings book. :)
  • ::raises hand:: How exactly do you make light go slower? I thought it was the one thing that was always constant, no matter what. But then again, I never did do very well in Physics. :)
  • ''If a sufficiently fast-spinning vortex of these or similar materials could be created, light inside the fluid could lose maneuverability and become trapped in the vortex'' Hmmm sounds like a different approach of making light emitting fluids like the jellyfish dna-method. :)


    Regards,
  • It is theoretically possible to create a black hole in one's own basement/backyard. Many of you may be familiar with digital sampling. One of the main priciples behind digital sampling is that in order to get a decent digital copy of an analog sound is to ensure that your sampling frequency is at least twice your highest analog signal frequency. To ensure with out a doubt that you have a quality digital sample we simply need to drive the sampling frequency toward infinity. The amount of energy required to make an infinitely small time slice will theoretically create a small black hole. Of course, as it sucks things in, it will grow in size.

  • How exactly do you make light go slower?

    One method of making light go slower is to use a window. Light travles at approx 200,000 km/s in glass, compared with almost 300,000 km/s in air.

    The speed of light is not constant. The speed of light in a vacuum is constant. The speed of light in a Bose-Einstien Condensate (which is what these folks are planning to use) is far far slower than the speed of light in glass or in air or in a vacuum.

  • The text shows that these only trap light by chemical means in order to simulate a black hole, there is no actual gravity well produced :)
  • BTW there is no theoretical or practical means of containing a gravity well black hole

    A black hole will contain you before you can contain it :)
  • Ive tried electrical fields before, but the grass was imperfect :)

    No,but seriously, even if you could create a conductive core which could touch a black hole (precisely on the event horizon) any electricity would instanty be consumed by the hole itself; or rather the matter entering the hole (electrons being a component of matter but inexistent without it)

    I however do know of one plausible way of moving (not containing) a very small black hole: you can 'tow' an object of simmilar mass infront of you black hole and the black hole will be constantly attracted to your object, and so long as your object doesn't approach the event horizon you are safe - quite how you re orient yourself to stop your 'hole' is another matter :)
    The major problem with moving a hole this way is a - there is no scientific proof or disproof that an 'event' can exist in any other place other than where it begins.
    b - the energy needed to pull your 'equally massive object' would somewhere in the order of 10_-100,000,000,000Nm

    As for how much matter you would need to create a charge high enough to charge the event horizon; every particle in the universe might be a good start.

    And if you could use an electronic field to attract a hole, your still left with the same problem of how to generate enough energy to move your cosmic 'tow' vehicle.

    The bottom line is that a gravity well at critical mass (a black hole) the size of a teacup would have roughly equal mass to 1 sun: if it oversteps critical mass, you haven't got enough fingers & toes to count the relative mass....
  • Yes but the inertia of even the smallest black hole (smallest critical mass to cause an event) is so incomprehesibly massive (literally) that if you got you magnets to 'attract the hole', the magnets + whatever they were attached to would rather go to the hole than the hole come to you...... not: I cant remember what the smallest possible critical mass of on 'hole is but I saw the figure and remeber being blow away by it! My brain hurts: lets go talk about OSS now (another blackhole some would say) :)
  • Thats more or less what I said :)
  • It seems that everything you talk about relating to black holes is a paradox, it tookme a few seconds to work this out (because they expect you to know what *they* are talking about):

    Here goes: They use the word 'comparable' when it may have been better to use 'relative'.

    The gist of it is you can't accelerate matter up to the speed of light; therefore you slow the light down instead. So you don't need a whirlpool which spins at hundreds of thousands of miles
    per hour :)

    It would be interesting to see if some of Steven Hawkings theory is correct, and if you haven't read the 'brief history of time' go out and buy now! (but not from amazon.com) its worth it just to have on the coffee table when friends are round
    (friend:"ooh, whats that book about" you:"well....") ;)

    Maybe you all understood better than I, just thought I would post this incase anyone was left scratching their head.....

  • Re:This is why Science is dangerous. (Score:3)

    by Eythain ( 120617 ) on Tuesday February 01, 2000 @03:04AM (#1316511)
    But these are black holes we're talking about here.

    Actually, no we aren't. Not in the important sense of a gravitational singularity. This is merely something that simulates some aspects of a black hole, namely that light goes in and doesn't come out. Theory suggests that this violates preservation of information, meaning that there must be some other force at work countering it. That's the radiation part. To examine this would be an interesting insight into a realm we don't know much about.

    But this is not a dangerous experiment in any way. Your armageddon scenario fails because there isn't any actual singularity in the picture.

    -- Eythain

    PS Besides, the 30 minutes calculation for a real balck hole is way off, or rather, that would depend entirely on the mass of the black hole in question. A natural black hole from a collapsed neutron star would squish us before we even got close, whereas a quantum black hole we could concievably make would probably be so small it would evaporate, or even if it wasn't, it would not significantly affect the Earth (I mean, it's not likely we can make a black hole a significant fraction the mass of Earth, where would that mass come from?) while growing. Since a singularity this small is basically point sized (even the event horizon), it would be severely limited in how quickly it could swallow matter. So relax, we'd certainly have a century or so to evacuate, even in the worst case scenario.

    A good book on that horror scenario would be Earth, by David Brin.

  • Many of you are asking about a material in which the speed of light is very slow. Such a material was demonstrated last year:

    Yeah, but accelerating it in any manner is going to add plenty of energy so that light moves much faster.

  • If this were the speed of light in a particular medium, then it wouldn't take too much to make the medium go faster than that.

    Er, yeah, but if you try to move the medium, you're going to add plenty of energy, and then you'll no longer have a Bose-Einstein condensate. I can't see how you'd be able to do this without finding a different material capable of slowing the light down.

  • But that's one heck of a supposition! Assuming a massive objects could be spun at such extreme rates is...generous. Am I wrong, here?

    If you recall the story ran here a while back, researchers have been able to slow down the speed of light to just a few meters/second. Using this technique, it would be possible to create a vortex that would be able to trap this slow moving light. Therefore, it is not necessary to speed up the vortex by millions of miles an hour - just fast enough to trap the slow moving light.
  • Even if we were talking about a gravitational black hole, it would not be particularly dangerous at the sizes we're talking about. What makes a black hole a black hole is not its mass, but its density. Theoretically, if you replaced our sun with a black hole of the same mass, Earth's orbit would remain unchanged, because the gravitational force is still given by Newton's equation F=(G(Msun*Mearth))/a^2 (G is the universal constant of gravitation, a is the semimajor axis of earth's orbit). If we took a bucket of water and compressed it into its Schwarzchild radius (that's how you make a black hole, by the way), which would be a couple millionths of a meter (I don't have time to calculate the actual radius now), at normal distances the gravitational effects of this black hole would be the same as for an ordinary bucket of water. It's only when you get near the event horizon (which is the same as the Schwarzchild radius, btw) that you get those wonky relativistic effects.

    Seems some of us are forgetting our high school physics.

    --Kevryn
  • I suggest we use a modified toilet as a proper water vortex accelerator.

    After all, who wants to see that water anyway? ;)

  • In the meantime, physicists are also pursuing the idea of creating "acoustical black holes" (dumb holes),

    It's already been done: Courtney Love and her band.

  • Scientists have already slowed the speed of light to somewhere around 50Km/h or so. Can't quite remember where the story is located, anyone have a link? BTW, it was done by sending light through substances at near absolute zero temps.

    -Elendale (err... I have nothing witty to say here)

  • I've seen something similar done with a Biro and a pint of Guinness. Once you stir the Guinness quick enough, a vortex is created which sucks the ink out of the Biro.
  • This has the possiblity of becoming a large scientific field, as studying a real black hole would be rather difficult (only possible assuming we ever figure out intersteller travel anyway) this could provide a lot of insight on the mechanics of the universe, with the added bonus of not having to leave our own back yards, so to speak :)
  • The idea is to use a medium where light is only going something like a few meters per second, check out the article.
  • Umm...did you read the article? these are optical black holes, they only affect light, and these "holes" would be a parellel to what happens to mass in a real black hole. So unless you are composed entirely of photons, I don't think you have too much to worry about.
  • "The idea is to use a medium where light is only going something like a few meters per second..."

    A medium? That sounds more like sorcery than science. Is it done with crystals?

    I think that if science can invent air brakes (presumably to help us brake wind), then why not invent light brakes to slow their light down? This is different than brake lights which are just an indicator (usually of the speed of traffic, not light).

    Also, if they slow the light down, wouldn't it only be an optical brown hole? And since it's not a real black hole (or brown), but only an optical one, what's to prevent people from checking it out and saying, "I just don't see it"?
  • What a load of bunkum. There's a world of difference (yuk yuk yuk) between an optically inescapable region and a gravitationally inescapable one.

    Else I just made a black hole by lighting a cylume stick inside a brick, or putting a flashlight in a draw an closing it. Or drawing the blinds.

    Rotating fluid faster than the speed of light within it is like putting a brick on the table and saying that it's going faster than the speed of light within it. Or sitting stock still in a vacuum and saying you're going faster than the speed of sound.

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