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Math Science

First "Observation" of Hawking Radiation 86

Posted by kdawson
from the simulation-or-experiment dept.
KentuckyFC writes "Italian physicists are claiming the first observation of Hawking radiation, but not from a black hole. Instead they've spotted it streaming from a sonic horizon in a Bose Einstein Condensate (abstract on the arXiv). That's consistent with previous predictions but they're claiming the 'first' even though the experiment was only a numerical simulation. Does that really count?"
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First "Observation" of Hawking Radiation

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  • by JeepFanatic (993244) on Thursday March 06, 2008 @10:45AM (#22662810)
    ... and they wanted to get First Post?
    • Look who is talking!
    • The story is grossly distorted -- what a surprise. I was going to say that at least it was distorted by author of the linked-to news item, rather than by the /. submitter, but now I see they seem to be the same person ("KFC" and "KentuckyFC").

      The abstract that is linked to merely claims "numerical evidence", not "first observation", and to get from that unobjectionable claim to the more sensational false accusation, one must distort the paper itself ( http://arxiv.org/pdf/0803.0507v1 [arxiv.org] ), which says:

  • and you get a black hole. but, don't feed it.
  • Doesn't Count (Score:5, Insightful)

    by ObsessiveMathsFreak (773371) <obsessivemathsfreak@@@eircom...net> on Thursday March 06, 2008 @10:50AM (#22662852) Homepage Journal

    Does that really count?
    No, no it does not.

    A numerical model is little more than a highly specific and round off error prone implementation of existing analytical results. All these guys have done, at most, is shown the correctness of Hawking's analysis. If that.
    • Well, it does prove that either our models of BEC are very accurate or there has been one hell of a coincidence. I don't think that they can say they were the first to discover this, but you may argue that they have produced evidence that supports the theory.

      If they had found no radiation, that would not have been proof of anything since a flawed simulation would produce a flawed result. However, the odds of this particular flawed result (producing hawking radiation under very specific circumstances)must
      • Re:Doesn't Count (Score:5, Informative)

        by Beetle B. (516615) <beetle_b@[ ]il.com ['ema' in gap]> on Thursday March 06, 2008 @11:57AM (#22663626)

        but you may argue that they have produced evidence that supports the theory.
        No, you can't.

        Without knowing the details of both theories, it's hard for me to judge. Basically, if their formalism is more or less isomorphic to Hawking's (without their realizing it) - then all they've done is do Hawking's work over again.

        If they used independent formalism to get Hawking radiation, then it's a good sign, and shows that their theory is consistent with Hawking's (and perhaps later someone will link the two).

        In either case, they did not produce any evidence. At best, they're saying, "If you look at this our way, it is consistent with what Hawking predicted."
        • I see what you are saying and I think it comes down to this. If the theory that hawking radiation is produced is derived from the same information that the simulation is derived from, very little is shown.

          If, however, the simulation is derived from seperate data (experimental, different aspects of BEC theory) then the results could be meaningful as they would show that the two different sets of data are in agreement.
        • If they used independent formalism to get Hawking radiation, then it's a good sign, and shows that their theory is consistent with Hawking's (and perhaps later someone will link the two).

          In either case, they did not produce any evidence.

          If they have correctly use an independent formalism to verify Hawking radiation, they may not technically have "produced" any new evidence, but it means that all the existing evidence that backs the independent formalism, now also counts as evidence towards Hawking radiation.

          [ I haven't read the fine article either. ]

          • by Bloater (12932)
            > If they have correctly use an independent formalism to verify Hawking radiation

            They have not verified Hawking radiation. They did not observe Hawking Radiation in a Bose-Einstein Condensate. They produced a computer program that draws an animation of what Hawking radiation might look like and then watched it - thus they "observed" the radiation just like you or I might observe the existence of Martians by looking at the right Bugs Bunny cartoon ("Look a Martian! And he's wondering where the ka-boom is!
            • They have not verified Hawking radiation.

              A verification consist of comparing the predictions made with one formalism with the predictions made with another (presumably more trusted) formalism, and see that they match.

              A validation consist of comparing the predictions made with one formalism with actual measurements, and see that they match.

              Verifications are not as strong as validations, but none the less quite useful. Typically it works the other way around though, we verify a numerical model against one or more analytical solutions. If they mat

        • Re: (Score:3, Insightful)

          but you may argue that they have produced evidence that supports the theory.

          No, you can't.

          I agree. Physics is an attempt to model the universe mathematically. The fact that two models agree says nothing whatsoever about whether either is an accurate map of the universe.

    • Right, "Garbage in, garbage out".

      That's the problem with computer simulations that are unsupported by real observations: you never know if there's a problem with your input data, a bug in your simulation program, or a serious weakness in the theory you are simulating, or some combination of all of these. So it's hard to believe your outputs until you can check them against a real measurement.

  • by jayhawk88 (160512) <jayhawk88@gmail.com> on Thursday March 06, 2008 @10:51AM (#22662866)
    That accurately describes about 90% of theoretical physics doesn't it?
  • 6 * 7

    It's just a numerical simulation, but everybody knows it counts anyway.
  • I am sorry, but I don't buy it... You have a theory how the world behaves. You do a numerical simulation based on that theory, and amazingly, it proves true. And you consider that a proof of your theory?
    I guess I will make a theory stating that fairies exist... simulate that in a computer, and when fairies appear in my simulation I write an article that I have observed fairies. Mmmmhh, this certainly sounds like proving ID.
    • by gardyloo (512791)

      I guess I will make a theory stating that fairies exist... simulate that in a computer, and when fairies appear in my simulation I write an article that I have observed fairies. Mmmmhh, this certainly sounds like proving ID.
      Sssssssshhhh! Do not give the IDers any ammunition with which to bullshit the public.
      • by rucs_hack (784150)
        Sssssssshhhh! Do not give the IDers any ammunition with which to bullshit the public.

        Since they live in the information equivilent of a closed and shackled ecosystem, this could hardly do any damage.
    • by CmdrGravy (645153) on Thursday March 06, 2008 @11:46AM (#22663484) Homepage
      Not quite, if you imagine the theory as a car then the scientists suspected it might have been a Porsche Cayenne 4x4 and once they had built their simulation ( imagine that as a carwash ) it turned out that it was indeed a Porsche Cayenne 4x4. However the amazing thing was that even though they hadn't considered the driver specifically in their simulation it did indeed turn out the simulated driver was a enormous wanker thus proving beyond doubt the truth of their simulation.
    • by spongman (182339)
      well, if your theory was consistent with known physical theories (modulo GUT), then couldn't you confidently say that modern physics predicts the existence of fairies.

      so, either:
      1) fairies exists
      2) physics is fundamentally wrong

      whichever it is, it's pretty profound.
    • by DougWebb (178910)

      I am sorry, but I don't buy it... You have a theory how the world behaves. You do a numerical simulation based on that theory, and amazingly, it proves true. And you consider that a proof of your theory?

      To turn it into a proof, you need to get the UN to claim that "every non-kook scientist in the world agrees that this is true, and every scientist who does not agree is a kook, or is being paid to disagree by a global corporate conspiracy that is trying to suppress this proof". Then you get the Nobel commi

    • Re: (Score:3, Interesting)

      by Chris Burke (6130)
      You have a theory how the world behaves. You do a numerical simulation based on that theory, and amazingly, it proves true.

      Well that's not exactly the case. We have a theory of how the world behaves, and Hawking Radiation is a predicted emergent property of that theory. It's not an axiom, it's a predicted consequence, so it isn't a given based on the theory. Here, we have a detailed simulation that shows that yes, if the underlying theory is correct, then we should expect to see Hawking Radiation.

      It is
  • by idontgno (624372) on Thursday March 06, 2008 @11:13AM (#22663078) Journal

    ...though the experiment was only a numerical simulation. Does that really count?

    If so, then many slashdotters are no longer virgins.

  • by TeknoHog (164938) on Thursday March 06, 2008 @11:17AM (#22663126) Homepage Journal

    My first thought from the headline was Unruh effect [wikipedia.org]. It's a kind of Hawking radiation you can get in a particle accelerator. It just happens that with black holes, the acceleration is due to gravity, but other sources of acceleration also work. There are huge decelerations from c to nearly 0 at heavy ion collisions, for example.

    I first heard of the effect when some fellow physicists were considering the idea of tiny black holes created in particle physics experiments. It turned out that the presence of Hawking-like radiation doesn't necessarily mean a black hole.

    Well, it also turns out that this has nothing directly to do with the article, but might be +i, interesting nevertheless.

    • Well, it also turns out that this has nothing directly to do with the article, but might be +i, interesting nevertheless.

      Your comments have everything to do with the paper in question.

      How ironic. Usually people don't read the article, then make irrelevant comments that they think are relevant; here you managed to do the exact opposite.

  • If you consider the cusp of the gravity well of the earth to be a simplistic representation of the event horizon then:

    an object travelling inside the well is doomed to never escape without additional energy.
    it will spiral to its death after some time period.

    If two objects at this same point collide and explode, then some of the matter will have gained additional energy and will escape the gravity well, the rest of the body will spiral to its doom.
    • by gardyloo (512791)
      I'm being pedantic here:

      1. Cusp? What cusp? That's not how the term is used, in either popular language, nor in physics.
      2. If I understand "cusp" to mean the location at which an object released from rest will *just* fall to earth, there's no such location. ALL objects will, from any location (given no other mass or energy in the universe, of course).
      3. If one allows an initial momentum to your object, then the "cusp" location can be anywhere
    • by ExecutorElassus (1202245) on Thursday March 06, 2008 @11:38AM (#22663378)
      yes, but Hawking radiation is somewhat different, and requires no material in the vicinity. It works like this: there are always opposite particles (say, positron-electron pairs) that spontaneously appear at the subatomic level. But in the normal universe, they immediately re-collide, giving back to the local space whatever energy was used to create them. That's a bad explanation (because I'm not a physicist), but it gives a rough picture. At the edge of an event horizon, however, there is a small - though nonzero - chance that one or the other particle will get sucked down the gravity well before it can remerge with its opposite. Thus the one that survived ambles off into space, no doubt pondering its cosmic parthenogenesis. The energy of the particle is - for reasons unknown to me - taken from the black hole. Also, this process steadily accelerates as the black hole continues to lose mass through the process: it eventually pops out of existence in a burst of gamma radiation.

      So, it's a little more complicated/interesting than you described; I'm sure it would be even better if someone here could describe it from an actual background in physics, instead of the armchair variety I can muster.
      • Re: (Score:3, Insightful)

        by UncleTogie (1004853) *

        It works like this: there are always opposite particles (say, positron-electron pairs) that spontaneously appear at the subatomic level.

        ...and you wonder why the ID crowd looks annoyed when they're not allowed to use the same "well, it just appeared!" argument...

        • You're probably just being funny, but just in case you're serious: Saying that a particle just appears is not the same as saying that a more complex entity just appears. These particles are just static (white noise) in the fabric of the universe.
          • Re: (Score:1, Insightful)

            by Anonymous Coward
            Wait a second, I thought we came from "static".
            • The processes aren't at all related. The surface of the oceans has waves constantly created and destroyed. There's nothing surprising that a bunch of water has waves appearing and disappearing constantly. The fabric of the universe has a similar sort of thing going on.
      • by ChronosWS (706209)
        I may be off the mark here, but I believe the energy comes from the black hole because the virtual particles are derived from the energy locked up in the space-time substrate itself - they don't just come from "nowhere", and their existence is not free in the entropic sense. The black hole is just a manifestation of this substrate, so any particles which temporarily appear must take their energy from it.
      • Re: (Score:2, Informative)

        by Anguirel (58085)
        The energy comes from the black hole because the mass comes from the black hole.

        The easiest way to conceive of it, in very basic terms, is that the Electron/Positron pair spontaneously converts to mass from the energy surrounding the black hole. The positron falls into the hole, and annihilates with an electron's worth of mass already in the singularity. The electron from the initial pair escapes. The black hole has been reduced in mass/energy by the amount of one electron.

        If the electron, instead, falls
      • Re: (Score:2, Interesting)

        Not quite my understanding. Positron-electron pairs don't get created spontaneously as this would violate the conservation of energy. However, a pair of what are called "virtual" particles can appear spontaneously if one of them has a negative mass.

        Now, a negative mass particle can't normally exist for very long, so it has to recombine in short order with the original particle and they cancel each other out.

        However if the negative mass particle is trapped by the event horizon, "not very long" gets stretch
    • by Cecil (37810)
      If two objects at this same point collide and explode, then some of the matter will have gained additional energy and will escape the gravity well, the rest of the body will spiral to its doom.

      Yeah, you'd think that, wouldn't you? Unfortunately, relativistic physics do not follow the same rules as newtonian physics, and the former are the rules you need to use for anything that may potentially have enough energy to escape a black hole.
    • by maxume (22995)
      That's not what the event horizon is. The event horizon is the point at which collisions will no longer matter and is derived from the black hole, not the momentum of a particle approaching it.
  • It's just a simulation... hawking radiation hasn't been observed in real life yet.
  • by Anonymous Coward

    Instead they've spotted it streaming from a sonic horizon in a Bose Einstein Condensate
    Eh? Is that some kind of new MP3 player?
  • by AbsoluteXyro (1048620) on Thursday March 06, 2008 @11:23AM (#22663214)
    How long until they "observe" a Fry, er, Hawking Hole? I could have swore I "observed" one on TV.
  • Shenanigans! (Score:5, Insightful)

    by multimediavt (965608) on Thursday March 06, 2008 @11:27AM (#22663266)
    I'm sorry, but I'm with the "no way this counts" camp. Theories have to be tested in the physical world to be proved. Theoretical physics included folks. That's why we have supercolliders and Z-machines, duh! Numerical analysis can help predict physical behavior but it is not law until it is proved in the real world. Sorry guys.
    • Re:Shenanigans! (Score:4, Insightful)

      by huckamania (533052) on Thursday March 06, 2008 @12:36PM (#22664088) Journal
      This is the 'new' science. First you have a theory, then you promote your theory, then someone takes a poll and then it becomes fact.

      Computer simulations are acceptable proof in the 'new' science. Even flawed computer simulations are acceptable proof as they prove that the simulations are getting better.
    • I'm sorry, but I'm with the "no way this counts" camp. Theories have to be tested in the physical world to be proved. Theoretical physics included folks. That's why we have supercolliders and Z-machines, duh! Numerical analysis can help predict physical behavior but it is not law until it is proved in the real world. Sorry guys.

      Sorry dude, experimental evidence doesn't prove squat either.

      Newton's experimental evidence for adding of velocities was correct until Einstein. And is corpuscular theory of light was correct until Young's "double slit" experiment. So even when an experiment demonstrates a theory, it doesn't prove it, is only shows that its not incorrect.

  • Ugh. (Score:3, Insightful)

    by stonecypher (118140) <stonecypher AT gmail DOT com> on Thursday March 06, 2008 @11:45AM (#22663456) Homepage Journal

    but they're claiming the 'first' even though the experiment was only a numerical simulation. Does that really count?
    No. Observed means "in the real world." These people should be ashamed of themselves. Physicists are supposed to have standards.
    • I think you're being a bit unjust to the physics community. I agree that the observation of Hawking radiation from a simulated BEC is not an `observation' as such, but the model, which the paper states involves no gravitational physics concepts and has shown to be a valid model based on current data, shows the presence of Hawking radiation. The fact that it is demonstrated in a system that is considerably better understood than quantum gravity is important for the following reason: Although i am not a cosmo
      • I think you're being a bit unjust to the physics community.

        By suggesting they have standards, and that as such, this small group of Italians is disgusting by contrast?

        but the model, which the paper states involves no gravitational physics concepts and has shown to be a valid model based on current data, shows the presence of Hawking radiation.

        Yes, and the Vatican's model showed crystal spheres. Models can show wrong things. That's what makes it disgusting that these people are claiming to have observed so

  • and they altered the phenomena by observing it.
  • God Exists! (Score:5, Funny)

    by serutan (259622) <.snoopdoug. .at. .geekazon.com.> on Thursday March 06, 2008 @12:07PM (#22663718) Homepage
    We've got millions of highly vivid simulations!
  • This is far from proof. But I would not really be surprised, just at an intuitive level, if Hawking radiation can be found at ANY type of horizon. Hawking radiation itself was predicted by a post-doc whose name I forget, promptly forgotten for several years, then it was picked up and championed by Hawking. Hawking himself wasn't the one who made the original connection between entropy and certain horizon equations, although he did start the process in motion with a proof that the area of the event horizon c

  • So they have 'observations' of a 'simulation' of a Bose-Einstein Condensate which 'theoretically' would behave with sound waves similarly to the way a black hole is 'theorized' to behave with regard to particles that pop into existence all the time and it's proof of Hawking radiation? There are just too many theoretical leaps here to give it any weight. If these sound waves were ACTUALLY observed in a real-world experiment and not a simulation then that would be a step closer. Can't they just make a simu
  • That's consistent with previous predictions but they're claiming the 'first' even though the experiment was only a numerical simulation. Does that really count?

    I'm prepared to be corrected, but doesn't that count as a prediction rather than an observation?

  • I hope so, because that would make me a fighter pilot, a train driver, and a theme park owner this week alone. I have after all used MS flight sim, MS Train sim and Trains, and Rollercoaster Tycooon. Oh I almost forgot I own a motorboat and a jet ski (Ship Sim 2008. We didn't say it had to be a GOOD simulation did we?). I'm so good I can ram a boat at high speed in a jet ski, duck under it instead of dying, and come out the other side!!! Come to think of it I rock, but only if simulations count!
  • Pfft.. I've detected Hawking Radiation spewing from the sonic horizon of my Bose Wave Radio for years!

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