Simulating the Universe with a zBox

An anonymous reader writes "Scientists at the University of Zurich predict that our galaxy is filled with a quadrillion clouds of dark matter with the mass of the Earth and size of the solar system. The results in this weeks journal Nature, also covered in Astronomy magazine, were made using a six month calculation on hundreds of processors of a self-built supercomputer, the zBox. This novel machine is a high density cube of processors cooled by a central airflow system. I like the initial back of an envelope design. Apparently, one of these ghostly dark matter haloes passes through the solar system every few thousand years leaving a trail of high energy gamma ray photons."

Comments

Read the entire paper: astro-ph 0501589

[StupendousMan]

You can read the entire paper in PDF or PS at astro-ph, a web site which collects preprints in the physical sciences. See

http://xxx.lanl.gov/abs/astro-ph/0501589

I read the paper quickly. The authors have to come up with a model which has virtually no observable consequences (otherwise, we would have seen this source of matter by now), but which can also be tested experimentally in the not-too-distant-future (or else it wouldn't be science). They predict that some of the cosmic-ray shower telescopes may be able to detect the little cloudlets of dark matter. We'll see.

Mirror

[Rufus211]

Maybe they should have use the zbox to host their site =)

http://rufus.hackish.org/~rufus/mirror/krone.physi k.unizh.ch/~stadel/zBox/

Re:I don't understand...

[Sique]

The problem in question is the number of distinguishable bodies. With weather you would have to go down to the single molecule in the air, to get a quite good prediction. In fact current weather models use cubes of air where the conditions are considered constant (same temperature, same pressure, same direction of air flow in the same cube) and take them as distinguishable bodies. Those models are a compromise between the sheer number of necessary elements, the number crunching limits of current calculation hardware and the difference between the used model and the reality.

With stellar bodies it's much more easy. The number of stellar bodies you need for a prediction is much smaller, the bodies themself can be considered almost constant for the whole calculation etc.pp. With the number crunching capacity of today's weather prediction centers you can simulate whole galaxies (if you consider stars constant, which they mainly are for about 10mio to 10bio years, depending on their mass). With the differences between your model and the measured reality you can spot elements you didn't simulate yet and add them to your model. The swiss team now was simulating clouds of about the mass of the earth and the size of the solar system and found that those added to the stellar simulation made a quite good fit to the measured data.

Re:I don't understand...

[orangesquid]

Well, you'd have to have a capture/drawing tool like Chemtool, and then something that could approximate polarity, electrical charge distribution, and bond length/strength. (Those involve things like electron orbitals, hence the subatomic.) Next, you'd have to have something that handles movement of fluids and gases with respect to the temperature, pressure, etc (gas laws and the partial diff. eqns. whose exact solution is one of the Clay instutite Millenium problems). Then, you'd have to have something that will predict what happens, probabilistically, when two or more molecules interact. These interactions would have to modeled in terms of molecular collisions, so that things like titration, stirring, etc, would be accurate.

Finally, you'd have something which would prepare an "answer" to each problem by waiting for a reasonable amount of precipitate to settle, or measuring pH, or simulating a gas chromatograph of the contents of the beaker.

Other helpful things would be crystallization and such. I would think that if you could simulate the physical laws and properties at a sufficiently low level, most things would arise automatically, but IANAC.