US Lab Models Galaxy Cluster Merger

astroengine writes "The scales are mind-boggling and the physics is cutting edge, so how do you go about simulating the collision of two galactic clusters? Using some of the most powerful computers in the world, researchers at Argonne National Laboratory, the Flash Center at the University of Chicago and the Harvard-Smithsonian Center for Astrophysics have done just that."

Comments

Does this qualify as a big bang?

[ctmurray]

When two such large object collide in outerspace does it make any noise?

Re:Does this qualify as a big bang?

[lavagolemking]

No. Sound is the vibration of air molecules, so when you speak or drop something, it creates compression waves that travel through the air and vibrate your eardrum, which in turn creates waves in the fluid of your cochlea that stimulate hair cells connected to the acoustic nerve. Since outer space has (almost) no air, these waves have no medium on which to travel, and sound as we know it does not happen.

Re:Does this qualify as a big bang?

[trashpickinman]

Whoosh... Thats the sound of a joke going over your head.

Re:Does this qualify as a big bang?

[lavagolemking]

Except x-rays and gamma rays are light, being on the electromagnetic spectrum, and traveling at 299,792,458 m/s. Sound only travels around 340 m/s, depending on its medium. Also, if they were sound they wouldn't travel through space either.

Re:Does this qualify as a big bang?

[Yvan256]

It's sound, Jim, but not as we know it.

Re:Does this qualify as a big bang?

[Black Parrot]

Whoosh... Thats the sound of a joke going over your head.

If a joke goes over your head in outer space, does it make a woosh?

Re:Does this qualify as a big bang?

[Angst Badger]

No. Sound is the vibration of air molecules, so when you speak or drop something, it creates compression waves that travel through the air and vibrate your eardrum, which in turn creates waves in the fluid of your cochlea that stimulate hair cells connected to the acoustic nerve. Since outer space has (almost) no air, these waves have no medium on which to travel, and sound as we know it does not happen.

Well, yes and no. There's no sound in space that a human could hear -- especially over the deafening roar of their blood boiling in the near-vacuum of space -- but there is a tremendous amount of diffuse gas and dust in galaxies and galaxy clusters, through which compression waves travel, albeit very weakly and slowly. If you were to observe those waves, then you could convert that data into an audio waveform in the range of human hearing. I may be misremembering, but I seem to recall that a group of researchers did precisely that with the (vastly smaller, nearer, and more easily observable) waves of gas being propelled outward by the pulsar at the heart of the Crab Nebula.

And yes, I know that really stretches the human notion of sound, but objects the size of galaxy clusters stretch most of our petty human notions, so it only seems fair.

Re:Does this qualify as a big bang?

[dkleinsc]

I'm not sure about a big bang, but it's definitely a cluster f*.

Merger

[Anonymous Coward]

In a merger that size, the job losses must be astronomical.

Re:Near one of those simulated stars . . .

[toastar]

. . . does it have a planet with living beings running astronomical computer simulations?

not anymore

no sound, but it makes a huge...

[thejuggler]

disturbance in The Force.

Science by graphical bedazzlement

[rbmyers]

The Department of Energy totally loves this kind of publicity. They want you looking at their pretty pictures and saying "Oh, wow!" The bureaucrat with whom I constantly spar over this science (and computer budgets) by pictures denies that the pictures are all that important, but we are constantly bombarded by them. The science and the numerics here may be great or they may be garbage. It doesn't matter all that much, I claim, because the people who vote on budgets and write the checks would never know the difference. Might as well turn it all over to Pixar for all anyone could prove one way or the other.

Re:Science by graphical bedazzlement

[Sarten-X]

Graphics give understanding, though. A numeric analysis can show exactly what happens, but it doesn't convey a general idea of what's going on. Pictures are easier to understand, and show more information at once. There's a reason why the weatherman shows his forecasts on a giant map.

Speaking of giant maps, I visited the ANL recently, and saw a computer system being used for related research. If they're using the same visualization system (which looks REALLY similar to the video in TFA), then this graphical model could be shown on a giant screen, and the model could be rotated & zoomed at any point. It's science through pictures, not just pictures of science.

Re:Science by graphical bedazzlement

[Sarten-X]

That's because the Wall Street Journal, like so many others, confuses the meaning of the visualizations. They aren't results. Instead, they're great tools for finding what parts of the theory need a better test.

As a contrived example, let's say that this visualization shows that a plume of dark matter going in a particular direction at a particular time. Comparing the visualization at that time to known colliding clusters in the real world might help show where to point our telescopes for evidence of dark matter. It helps to create the initial hypothesis, reducing the number (and therefore the cost) of failed experiments.

Another use is for verification of a model. If we already know of several colliding clusters, this visualization should, be able to produce images that look very similar to those clusters. If not, then we know that there's something wrong with the model, and we can find ways to improve it.

Tying that in with your example, we now know that the fluid model used wasn't perfect. It's time for more analysis, experiments, and refinements, eventually resulting in a more thorough knowledge of our universe.

No scientist worth their salt will say that any model is absolutely perfect. In fact, the one you spoke of didn't. She said it was the "perfect model to do <a given job>," implying that it could do the job with the given parameters, and that deriving a completely new model wasn't necessary. The model itself is imperfect, but it fit the job perfectly. If the journalists presented the model as a prediction, that's the journalists' fault.

Hopelessly confused by dark matter.

[Anonymous Coward]

I'm confused by "As the two clouds of dark matter inside each cluster can only interact gravitationally"

If dark matter can interact gravitationally wouldn't this mysterious crap just accumulate in the gravity wells of massive objects like stars or even the earth the same way planets collect rocks and dust around them?

Especially since everyone seems to be saying that dark matter so outnumbers normal stuff wouldn't a significant portion of the total mass that contributes to gravity of our own sun and earth be from dark matter?

I don't doubt that dark matter contributes to gravity but to say that it has an effect in a way that would suggest it have "mass" is one of those moments where I go searching to find out what I don't understand this time because that makes no sense. If dark matter acted as "stuff" that had mass then surely it would clump!!

Photons are massless but they have energy and therefore contribute to the gravity field even though they are not effected by gravity in the same way a massive object would be...the only effect is travling thru the pit created in the metric by the presence of "stuff".

Please if there is anyone who can help me make sense of this I would be eternally grateful.

Re: Obviously cool ...

[Black Parrot]

but simulating galaxy collisions have been done before: http://www.galaxydynamics.org/

However, new to the simulation is dark-matter calculations.

Note that this is clusters, not galaxies.

Also, DM *has* been modelled in galactic collisions before. I don't know about clusters, though.

Re:Obviously cool ...

[wvmarle]

This is more than galaxies: this is about clusters of galaxies. Slightly bigger scale...

Re:Flash Center

[sensationull]

Flash, What better platform is there for simulating something that takes billions of years.

Re:Near one of those simulated stars . . .

[buchner.johannes]

Actually, galaxy collisions are thought to leave solar systems undisturbed, with only a handful of collisions. The reason is that the space between the stars are so large compared to their size. Gas merges and spiral arms are distorted, but a planet would be fine. This is also what is expected of the Andromeda galaxy merge.

Re:oh yes, dark energy

[Kagura]

It's better than fudging a cosmological constant into all of our equations.

Unless you still believe in the steady state theory.