Slashdot Mirror

← Back to Stories (view on slashdot.org)

Australian Astronomers Make Interstellar Hologram

Posted by Zonk on from the floaty-transparent-and-informative dept.

KentuckyFC writes "Australian astronomers say the way a beam of light from a pulsar is scattered by interstellar dust is analogous to the way a hologram is made. But to reconstruct an image of this dust, you've got to know what the light was like before it was distorted. With an impressive piece of computer optimization, these astronomers have worked out the 8000 coefficients that determine the light field and so have been able to produce an image of the interstellar medium (abstract on the physics arXiv)."

22 comments

  1. Astronomers make hologram? by BadMrMojo · · Score: 4, Funny

    To be fair, it sounds like the pulsar and the interstellar dust did all the hard work. The Australian astronomers just managed to notice it.

    1. Re:Astronomers make hologram? by Frozen+Void · · Score: 3, Insightful

      Information(such as hologram) doesn't exist outside the context of conscious systems able to interpret it. Light doesn't carry the information, the patterns are arising from temporal changes in light.

    2. Re:Astronomers make hologram? by MozeeToby · · Score: 1

      Perhaps "Astronomers Use Hologram-Like Effect to Determine Dust Cloud Structure" just doesn't have the same ring to it.

    3. Re:Astronomers make hologram? by $RANDOMLUSER · · Score: 2, Funny

      ...developing an algorithm that can simultaneously optimise the eight thousand coefficients that describe the electric field.
      Yeah. That's the easy stuff.
      --
      No folly is more costly than the folly of intolerant idealism. - Winston Churchill
    4. Re:Astronomers make hologram? by FooAtWFU · · Score: 3, Interesting

      Information(such as hologram) doesn't exist outside the context of conscious systems able to interpret it. Light doesn't carry the information, the patterns are arising from temporal changes in light. Maybe from the Philosophical standpoint, but there are a variety of other uses of 'information', including some very specific ones in Physics, where it is strongly related to Entropy.
      --
      The World Wide Web is dying. Soon, we shall have only the Internet.
    5. Re:Astronomers make hologram? by syousef · · Score: 1

      To be fair, it sounds like the pulsar and the interstellar dust did all the hard work. The Australian astronomers just managed to notice it. ...Only if by notice it you mean develop new mathematical techniques for extracting the data. In the same way you might "notice" the orbit of mercury doesn't quite fit Newton's model of Gravity.

      --
      These posts express my own personal views, not those of my employer
    6. Re:Astronomers make hologram? by Frozen+Void · · Score: 1

      That hologram was created from temporal changes in the light captured(with guesstimates about the fields the light goes through), it didn't exist in the light.
      Information in this case is an interpretation(or reification) of scientists parameters, light data, and correlation by computer into one hologram.

    7. Re:Astronomers make hologram? by alexgieg · · Score: 1

      Information (such as hologram) doesn't exist outside the context of conscious systems able to interpret it. Light doesn't carry the information, the patterns are arising from temporal changes in light.
      Information (such as holograms) are as much reality as the material substrate which carries them. Light is absolutely real, as is the information carried by it. The perceived patterns are the form, temporal changes in quantifiable electromagnetic fields are the matter, qualified light being the resulting ontological substance.

      To pretend otherwise, i.e., to bifurcate reality into perception as the subjective epiphenomena of indirectly quantifiable parameters, as if these constituted the whole reality of an entity, is an arbitrary philosophical proposition itself devoid of objective evidence. A table isn't "in reality" just a set of organized atoms. A table is "in reality" a table, which happens to have a complex structure which includes a subset of measurable characteristics, one of which we call "atoms".

      To be a "conscious system" is nothing more than to be an entity apt to perceive and actively interact with and over a broad range of non-quantifiable aspects of other entities, including but not limited to their direct and indirect formative universals.
      --
      Conservatism: (n.) love of the existing evils. Liberalism: (n.) desire to substitute new evils for the existing ones.
    8. Re:Astronomers make hologram? by Frozen+Void · · Score: 1

      See http://slashdot.org/comments.pl?sid=435874&cid=22243868

    9. Re:Astronomers make hologram? by alexgieg · · Score: 1

      That hologram was created from temporal changes in the light captured (with guesstimates about the fields the light goes through), it didn't exist in the light.
      The hologram that was obtained from temporal changes in the light captured is a fair approximation of the original one that existed (and still exists) in the it. Or, to be more precise, it is the same hologram, but with differing accidents.

      Information in this case is an interpretation (or reification) of scientists parameters, light data, and correlation by computer into one hologram.
      The information here is the recovering of qualitative (formal) realities constitutive of their quantifiable aspects. The fact that the same formal quality can be carried by completely different "materias", be it electromagnetic waves, mathematical formulas (including binary representation), imaginative representation, printed pictures etc., only further strengthens the perceived fact that forms, although only "interactive" while substances, are nevertheless independent from their carrying materia.
      --
      Conservatism: (n.) love of the existing evils. Liberalism: (n.) desire to substitute new evils for the existing ones.
    10. Re:Astronomers make hologram? by Retric · · Score: 1

      No the information was in the light. "There's all kinds of infromation locked in this data." Finding out what that information is like decoding an encrypted transmission the information is still there but finding out what it is still takes effort.

      There are year's worth of data from this object that's in the form of light that will one day reach the earth but is still in space for now. A specific picture they create may or may not accurately reflect the information stored in the light but at some level it's still an approximation of that information.

    11. Re:Astronomers make hologram? by Frozen+Void · · Score: 1

      Its only a model which doesn't exist without creating and observing it.
      The map is not the territory
      http://en.wikipedia.org/wiki/Map%E2%80%93territory_relation

  2. a white hole? by URL+Scruggs · · Score: 0, Offtopic

    Having done that, Walker and co say the information can be used to correct other observations of the [sic] such as timing measurements on the pulsar beams. The authors left the word out as if they were going to put it in later once they understood it, no wonder I don't understand the story. Maybe they've discovered whitespace.
  3. Genetic Algorithm by MozeeToby · · Score: 3, Interesting

    I'm interested in knowing what kind of algorithm they developed to solve this problem. It seems to me like it would be an excellent application of genetic algorithms as it is essentially a giant optimization problem. I sopose that assumes that you can recognize correct results when you see them though.

    1. Re:Genetic Algorithm by StonedYoda47 · · Score: 0, Offtopic

      Well, the correct results were a giant Foster's can, so yeah it was pretty easy for the Aussies to recognize. And yes, I realize that Foster's in Australia is not the same as Foster's in America. I prefer VB or Cascade myself.

    2. Re:Genetic Algorithm by jd · · Score: 4, Interesting
      Well, it depends on what exactly was optimized, but this is usually an iterative process where the next step is determined by herustics. So, yes, genetic algorithms would be fine for this. You keep going until whatever variable(s) you're optimizing hit a local minimum (the point at which herustics give up and decide all options will de-optimize the solution). You can either stop there or try another starting point to see if it produces a "better" result. If you keep going, then you've some stopping condition (eg: N successive runs in which no better result was obtained, or you have calculated more than some percent of the minima that system of equations would potentially allow for). If you've not calculated all potential minima, then ultimately "recognition" of correct results will be down to a gut instinct.

      This assumes that the system can't actually be solved or reduced/simplified to one that can without losing too much accuracy. If you can solve it, then all you have is some basic matrix algebra on an 8000x8000 array. Non-trivial, sure, but 4Gb of RAM and a good gaming machine (you want fast maths) would be adequate to crunch such data. Alternatively, an analogue computer would be ideal for a problem like this, as you'd have far greater precision and far greater parallelization. It would also take far more space and cost far more, but the world economy could do with a boost about now.

      --
      It's a small world and it smells funny; I'd buy another if it wasn't for the money; Take back what I paid (SoM)
    3. Re:Genetic Algorithm by hubie · · Score: 1

      If you link through to the paper, it is right there. Essentially to reconstruct the hologram you need to know the form of the electric field from the source. To do this they have a model for it that has thousands of parameters. To determine these parameters they use the Newton method of optimization, which is an iterative method. You guess a form for the input and crunch through the numbers to get an output. You then compare your output to what you measure. A difference function is constructed to determine how close the modeled and measured outputs are. You then tweak your parameters and try again until the difference function is minimized.

      To do the optimization you need to know how to tweak the parameters and you end up taking first and second order partial derivatives of your difference function. One thing you end up with is the Hessian matrix, which is a square matrix of second-order partial derivatives. With thousands of parameters in the model, the Hessian can be huge and very computationally expensive to calculate. In these cases, and this is what the authors did, one employs a quasi-Newton method that compromises by updating the Hessian instead of calculating all those partial derivatives. There are several ways to do the update and the authors went with an algorithm known as the BFGS method (this method is very popular and the code for it is freely available (and optimized for speed).

  4. Not always necessary by mstahl · · Score: 2, Interesting

    It's not always necessary to judge if a given solution is the solution, because often determining the optimality of a solution is tantamount to computing that solution analytically (i.e., not using genetic or EC techniques). For genetic algorithms it's only really necessary to determine the relative optimality of two solutions so that you can compare them and pick the best ones of the group quickly.

  5. Re:G A S P ! by Anonymous Coward · · Score: 0

    just like every story CmdrTaco posts is in someway related to his loves of underage boy cock and bathroom buttfucking.

  6. Like crystallography by sacremon · · Score: 3, Interesting

    It sounds like x-ray diffraction crystallography, where one has a pattern of scattering of an X-ray as it interacts with the atoms in a crystal. The difference here is that in the lab we tend to be dealing with regular crystals as opposed to presumably less organized clouds of dust. There have long been statistical methods for interpreting these data, called Direct Methods.

    --
    If you can't beat them, embrace and extend them.
  7. Well, at least it's not Girly by Anonymous Coward · · Score: 0

    Gotta love the credit line: http://arxiv.org/abs/0801.4183

    > Mark Walker (Manly Astrophysics)