Australian Astronomers Make Interstellar Hologram

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)."

Comments

Astronomers make hologram?

[BadMrMojo]

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.

Re:Astronomers make hologram?

[Frozen Void]

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.

Re:Astronomers make hologram?

[FooAtWFU]

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.

Genetic Algorithm

[MozeeToby]

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.

Re:Genetic Algorithm

[jd]

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.

Like crystallography

[sacremon]

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.