US Lab Models Galaxy Cluster Merger 89
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."
Does this qualify as a big bang? (Score:4, Funny)
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Only if the irradiation of countless barren worlds has a sound.
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Re:Does this qualify as a big bang? (Score:5, Informative)
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? (Score:5, Funny)
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Whoosh... Trumpets! Thats the sound of a joke going over his head in a scifi movie!
Re:Does this qualify as a big bang? (Score:5, Funny)
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?
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No, we could see them if out eyes could pick up those, but we would never hear them.
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Technically, humans can hear some microwaves too because of the heating and cooling of your brain or inner ear. The US Air Force also has a patent on it. [wikipedia.org] Supposedly, they can literally make you hear completely intelligible voices - according to the US Air Force.
Re:Does this qualify as a big bang? (Score:5, Funny)
It's sound, Jim, but not as we know it.
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Re:Does this qualify as a big bang? (Score:5, Interesting)
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.
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Larry Niven's outsiders [wikipedia.org] and star seeds [wikipedia.org] could probably hear the sounds of the collision.
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Strictly speaking, sound does not need to be in air. Any gas, solid, or liquid will transmit sound (varyingly well).
Huh. Will plasma transmit sound? I'm guessing not very well...
IANAP
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Will plasma transmit sound? I'm guessing not very well...
I'd guess the opposite, as interactions between ions in plasma are a lot easier (delivered through electromagnetic force caused by the electric charge) than interactions between atoms/molecules in neutral gas (delivered through collisions).
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So ... if we were to vibrate your cochlea directly, without the manipulation of air (i.e. bone conduction [wikipedia.org]), you're not hearing sounds, you're just having aural hallucinations?
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However, on such a scale as this, who is to say this isn't similar to two clouds colliding? I would hazard a guess that on some microscopic level there is definitely a sound of water droplets colliding when two clouds merge. On a universal scale, I'd say two galaxies colliding would be quite close, proportionally, to that sound.
no sound, but it makes a huge... (Score:3, Funny)
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I don't know if it makes any noise, but it does feel like having your brain smashed out by a slice of lemon wrapped 'round a large gold brick.
Re:Does this qualify as a big bang? (Score:5, Funny)
I'm not sure about a big bang, but it's definitely a cluster f*.
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define noise.
Merger (Score:5, Funny)
In a merger that size, the job losses must be astronomical.
Near one of those simulated stars . . . (Score:1)
Re:Near one of those simulated stars . . . (Score:4, Funny)
. . . does it have a planet with living beings running astronomical computer simulations?
not anymore
Re:Near one of those simulated stars . . . (Score:5, Informative)
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.
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what does "handful" mean, in terms of percentage of solar systems?
for instance, I understand that there are a lot of pluto sized objects orbiting our solar system. how close would a star (from another galaxy, which means it's moving in a completely different direction than the local surrounding stars) have to get to disturb those objects? I realize that in order to disturb a solar system, you need to disturb planet orbits (or destroy planets), but in order to seriously harm a civilization, considerably less
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In other words: one Bruce Willis isn't going to be enough.
Obviously cool ... (Score:1, Informative)
but simulating galaxy collisions have been done before: http://www.galaxydynamics.org/ [galaxydynamics.org]
However, new to the simulation is dark-matter calculations.
Cool none-the-less.
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Re: Obviously cool ... (Score:5, Informative)
but simulating galaxy collisions have been done before: http://www.galaxydynamics.org/ [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.
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Re:Obviously cool ... (Score:5, Informative)
This is more than galaxies: this is about clusters of galaxies. Slightly bigger scale...
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This is more than galaxies: this is about clusters of galaxies. Slightly bigger scale...
But what's a few orders of magnitude between friends?
Science by graphical bedazzlement (Score:2, Insightful)
Re:Science by graphical bedazzlement (Score:5, Insightful)
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.
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Re:Science by graphical bedazzlement (Score:5, Informative)
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 [intel.com]. 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.
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So what you're saying is that science grants should be decided by people who know something about science? That's a great idea.
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Acceptance by whom?
The pretty pictures are for PR, or gross visualization. Are you arguing that scientists should try to make their work more unpalatable to the public?
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Car Analogy (Score:1)
Hopelessly confused by dark matter. (Score:3, Interesting)
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.
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Bought that until you said "aether". Nice one! Almost got me to write an angry reply...
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If dark matter acted as "stuff" that had mass then surely it would clump!!
I don't know about the scale of stars and planets, but it is strongly believed that DM "clumps" in and around galaxies. The effect on the rotation curves was one of the first things that tipped off the probable existence of such stuff.
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I have similar ideas about dark matter. To me, DM is simply a way for scientists to explain their way out of issues we do not really understand. It's matter, but can not be detected. Doesn't interact with anything, apparently not even itself (in this simulation those "DM cores" simply pass through one another!), other than that it works on gravity. It's like aether - we don't know how it works, so we make something up to make it work. That's how it feels to me.
There are problems with modeling galaxies: the
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The same is true for gravity, science does not know what it is just describes how it behaves. Essentially ALL the fundemental forces and dimentions in the universe are "miricales" that have no explaination.
BTW the oldest star is thought to be 13.2byo, the universe is 13.7byo, meaning the first stars formed some 0.5 billion years after the big bang.
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"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?"
Other way around. Normal matter (the minority) tends to clump in areas where there's lots of dark matter. Dark matter itself clumps, as you predict it would, but not to the extent that normal matter does. Normal matter clumps partly due to gravity, but to make nice tight clumps like stars yo
Flash Center (Score:2)
the Flash Center at the University of Chicago
They used Flash to simulate a galactic collision?
And you thought it wasn't good for anything...
Re:Flash Center (Score:4, Funny)
Flash, What better platform is there for simulating something that takes billions of years.
Big Deal (Score:1)
oh yes, dark energy (Score:2, Informative)
Let's bundle up all of the errors in our model of the universe
and call it "dark energy". I say... "it is dark as ignorance".
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Unless you still believe in the steady state theory.
The Flash Center? (Score:1, Funny)
Oh man, Apple's going to be pissed!
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Also:
But that's ok, we know what will happen when two galaxies collide.
Reached the same result with 200 lines of Python (Score:1)
For a highly technical idea... (Score:2)
I've seen these in the 1990s (Score:2)
I have the utmost faith in this model... (Score:2)
... considering we can't even model our own climate with any semblance of accuracy.