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US Lab Models Galaxy Cluster Merger

samzenpus posted more than 3 years ago | from the we're-going-to-need-more-ram dept.

Space 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."

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Does this qualify as a big bang? (3, Funny)

ctmurray (1475885) | more than 3 years ago | (#33780132)

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

Re:Does this qualify as a big bang? (1)

DarkKnightRadick (268025) | more than 3 years ago | (#33780148)

Only if the irradiation of countless barren worlds has a sound.

Re:Does this qualify as a big bang? (1)

Mitchell314 (1576581) | more than 3 years ago | (#33780208)

It's a small "ping" sound, with a slight echo.

Re:Does this qualify as a big bang? (4, Informative)

lavagolemking (1352431) | more than 3 years ago | (#33780224)

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? (5, Funny)

trashpickinman (1078113) | more than 3 years ago | (#33780270)

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

Re:Does this qualify as a big bang? (0, Offtopic)

MobileTatsu-NJG (946591) | more than 3 years ago | (#33780568)

Whoosh... Trumpets! Thats the sound of a joke going over his head in a scifi movie!

Re:Does this qualify as a big bang? (5, Funny)

Black Parrot (19622) | more than 3 years ago | (#33780648)

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? (0)

Anonymous Coward | more than 3 years ago | (#33781316)

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?

Maybe it went under your head, but you were upside-down.

Re:Does this qualify as a big bang? (1)

lavagolemking (1352431) | more than 3 years ago | (#33781362)

See parent comment.

Re:Does this qualify as a big bang? (0)

Anonymous Coward | more than 3 years ago | (#33780326)

Well that's the classical sound definition, but technicly if humans could hear the highest frequencies man knows atm, say x-ray or gamma, we could be hearing allot of whitenoise comming from space.

Re:Does this qualify as a big bang? (2, Informative)

lavagolemking (1352431) | more than 3 years ago | (#33780392)

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? (1)

nedlohs (1335013) | more than 3 years ago | (#33783666)

No, we could see them if out eyes could pick up those, but we would never hear them.

Re:Does this qualify as a big bang? (1)

GooberToo (74388) | more than 3 years ago | (#33786436)

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? (4, Funny)

Yvan256 (722131) | more than 3 years ago | (#33780482)

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

Re:Does this qualify as a big bang? (1)

Charliemopps (1157495) | more than 3 years ago | (#33780592)

All the air that exists, is in outerspace. So I'd say your argument is flawed.

Re:Does this qualify as a big bang? (4, Interesting)

Angst Badger (8636) | more than 3 years ago | (#33780776)

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? (1)

LurkerXXX (667952) | more than 3 years ago | (#33783198)

Larry Niven's outsiders [wikipedia.org] and star seeds [wikipedia.org] could probably hear the sounds of the collision.

Re:Does this qualify as a big bang? (0)

Anonymous Coward | more than 3 years ago | (#33780896)

He might mean the noise of generated gravity waves as well.. ;)

Re:Does this qualify as a big bang? (1)

kwerle (39371) | more than 3 years ago | (#33780904)

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

Re:Does this qualify as a big bang? (0)

Anonymous Coward | more than 3 years ago | (#33781354)

That's a headscratcher, as IANAP also. If sound can travel through a gas I guess it can travel through plasma.

Re:Does this qualify as a big bang? (1)

Urkki (668283) | more than 3 years ago | (#33787132)

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).

Re:Does this qualify as a big bang? (1)

MartinSchou (1360093) | more than 3 years ago | (#33781916)

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?

Re:Does this qualify as a big bang? (0)

Anonymous Coward | more than 3 years ago | (#33782950)

Not to mention that this is basically a collision of two clouds anyway. They just merge into each other.

Re:Does this qualify as a big bang? (1)

L4t3r4lu5 (1216702) | more than 3 years ago | (#33783308)

You may be thinking of nebulae. They are clouds of dust and gas.

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.

Re:Does this qualify as a big bang? (0)

Anonymous Coward | more than 3 years ago | (#33786454)

Sound is not *only* the vibration of "air" molecules. Sound, as vibration, can travel through most gases and liquids.

So, if you were close enough to the permiter of the collision(s), and able to survive, where the gases were jetting out and being thrown off of the stars, then yes you would hear the sound.

no sound, but it makes a huge... (2, Funny)

thejuggler (610249) | more than 3 years ago | (#33780300)

disturbance in The Force.

Re:Does this qualify as a big bang? (1)

Sean_Inconsequential (1883900) | more than 3 years ago | (#33780370)

With the distances between stars in a galaxy, it is unlikely that the stars in those galaxies will actually collide. Though a galactic merger will cause rapid star formation.

Re:Does this qualify as a big bang? (1)

Yvan256 (722131) | more than 3 years ago | (#33780402)

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? (4, Funny)

dkleinsc (563838) | more than 3 years ago | (#33780966)

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

I head it. (1)

dogzdik (1700552) | more than 3 years ago | (#33791796)

I head the crash... it just depends on HOW you listen for them.

.

The shock waves travelling through air have their equivalents in space composed of other streams - gravity, light, rays, etc.

.

The background noise - isn't just "noise", it's the cosmic bangs, crashes and echos of eons long gone.

Re:Does this qualify as a big bang? (1)

rgviza (1303161) | more than 3 years ago | (#33794824)

define noise.

simulate this! (0)

Anonymous Coward | more than 3 years ago | (#33780188)

What about Galaxy Zoo .. http://www.galaxyzoo.org/

Merger (5, Funny)

Anonymous Coward | more than 3 years ago | (#33780198)

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

Re:Merger (0)

Anonymous Coward | more than 3 years ago | (#33780694)

That's why they're doing simulations. They need to get shareholder approval.

Slashdot has patented modelling CLUSTER FUCKS (-1, Troll)

Anonymous Coward | more than 3 years ago | (#33780200)

Because that's what this place is one big cluster fuck!

Near one of those simulated stars . . . (1)

Mitchell314 (1576581) | more than 3 years ago | (#33780202)

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

Re:Near one of those simulated stars . . . (3, Funny)

toastar (573882) | more than 3 years ago | (#33780214)

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

not anymore

Re:Near one of those simulated stars . . . (4, Informative)

buchner.johannes (1139593) | more than 3 years ago | (#33780998)

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:Near one of those simulated stars . . . (1)

chichilalescu (1647065) | more than 3 years ago | (#33782376)

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 disturbance is needed. For instance, a rogue moon sized object going through the asteroid belt might put a lot of them on different trajectories (that no longer correspond to the stable kepler orbits the planets are in).

Re:Near one of those simulated stars . . . (1)

Gotung (571984) | more than 3 years ago | (#33784324)

A solar system or planet might be "fine" in the astrological sense, but there is likely a much higher chance of objects in Oort clouds getting disturbed and sent hurtling towards your friendly neighborhood M class planet.

In other words: one Bruce Willis isn't going to be enough.

Obviously cool ... (1, Informative)

ProfM (91314) | more than 3 years ago | (#33780256)

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.

Re:Obviously cool ... (1)

Sean_Inconsequential (1883900) | more than 3 years ago | (#33780422)

There is also GalCrash [cwru.edu] .

Re:Obviously cool ... (-1, Troll)

Anonymous Coward | more than 3 years ago | (#33780552)

Yawn. Every story has to have some troll downplaying it from the "Simpsons did it" angle. Fuck off. It's all been done before in a previous universe. Shut your fucking face and enjoy the ride.

Re: Obviously cool ... (4, Informative)

Black Parrot (19622) | more than 3 years ago | (#33780586)

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.

Re: Obviously cool ... (1)

Mt._Honkey (514673) | more than 3 years ago | (#33783980)

I used to do simulations of galaxy collisions, and dark matter is the easiest part to put into the simulation because it is assumed to be collisionless. It just goes wherever the gravitational potential points it (of course, calculating that gravitational potential can be somewhat complicated if you want to smooth over the rough spots caused by the finite number of particles simulated). The hard part is the gas, which has much more complicated physics due to the collisions, heating, cooling, and radiation on top of the gravitational physics. This also removes the scale-independence from dark-matter-only simulations. These are some of the reasons why early galaxy simulations were largely of elliptical galaxies, because they contain negligible amounts of gas.

Re: Obviously cool ... (1)

Limburgher (523006) | more than 3 years ago | (#33785846)

I don't think a galactic collision would realy influence Depeche Mode all that much. . .

Re:Obviously cool ... (4, Informative)

wvmarle (1070040) | more than 3 years ago | (#33780728)

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

Re:Obviously cool ... (1)

ImprovOmega (744717) | more than 3 years ago | (#33796206)

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

But what's a few orders of magnitude between friends?

Somebody already did the modeling. (-1, Offtopic)

Anonymous Coward | more than 3 years ago | (#33780284)

His name was E. E. Smith.

Bad things happened.

Beware Boskone!

TrOll (-1, Troll)

Anonymous Coward | more than 3 years ago | (#33780304)

Science by graphical bedazzlement (2, Insightful)

rbmyers (587296) | more than 3 years ago | (#33780354)

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 (5, Insightful)

Sarten-X (1102295) | more than 3 years ago | (#33780658)

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 (1)

rbmyers (587296) | more than 3 years ago | (#33781030)

The DoE recently published a "prediction" that showed the oil from Deepwater Horizon racing up the east coast. As far as I'm concerned, the assumptions and methodology of the simulation were indefensible, but that didn't stop the Wall Street Journal from picking it up. While the DoE's *official* position was that the simulation wasn't necessarily credible as a "prediction," one of the NCAR scientists involved was quoted as saying that they realized that they had "the perfect model" for predicting the fate of the oil. The "prediction," of course, as compared to reality, was complete nonsense. As it stands, we still don't really know what happened to all that oil, but a picture in the Wall Street Journal left the impression that, not only did the DoE know exactly what was going to happen, but that what was going to happen was likely catastrophic. That's not science. That's not even defensible. Flow visualization has a long, important, and honorable history in fluid mechanics, but, in the past, you actually had to make some actual fluid flow to get a visualization. Now all you have to do is turn a computer on, and, if the results don't look completely crazy, people are led to believe that the science is credible. Maybe it is. Maybe it isn't.

Re:Science by graphical bedazzlement (4, Informative)

Sarten-X (1102295) | more than 3 years ago | (#33781312)

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.

Re:Science by graphical bedazzlement (1)

rbmyers (587296) | more than 3 years ago | (#33782084)

You're talking to someone who has done a fair bit of simulation and listened to others describe their own simulations. The simulation the Wall Street Journal bought into was wildly beyond naive. I told the author to ask an oceanographer, and he did. A later article, without simulation pictures, gave a much more accurate assessment of the unknowns. I'm not an oceanographer, but I've done ocean simulation, and I'm very familiar with the computational techniques employed. As a predictive tool for that situation, what NCAR and the DoE did was absurdly naive. People often have things wildly wrong and keep cranking out wrong results and briefing to them for years. I've seen it. I've been through it. Yes, simulations can be an aid to the imagination, sometimes a powerful aid, but the simulation itself is not science, and it's the confusion of pictures with science that bothers me. It's not a question of models being sometimes less than perfect. Sometimes, they are just WRONG. In the case of the Wall St Journal simulation, the results were complete misdirection. Not a useful clue to anything. The simulation assumes that dye injected into the mixed layer, and that is neutrally buoyant and passively follows the surface currents is a good proxy for the oil in the Gulf. None of that is remotely true for the Deepwater Horizon situation. The oil had complicated behavior that is different in so many ways from a passive dye tracer that it is hard to enumerate them. The "scientists" who cranked up the $100 Million code should have been smart enough to know that without even turning a computer on. As so often happens, though, they got a picture and could make up a good story to go with the picture, so the fact that it was a total waste of time and money is lost in the shuffle. I will concede one lesson learned: the DoE had no useful tools for predicting the fate of the oil in a catastrophic spill. For the problem presented for the Slashdot article at hand, there are not just the usual difficulties of fluid mechanics, but exotic physics that are, at this point, completely speculative. Those calculations are *expensive*, Asrophysics is awash in data. Maybe complicated, expensive simulations of unknowable accuracy are the only way to get a handle on the data, but it's pretty desperate science, and, with so much data out there, I wonder about the level of effort and credibility that is given to simulation. I certainly think that, "Oh, wow" is unjustified.

Re:Science by graphical bedazzlement (1)

ceoyoyo (59147) | more than 3 years ago | (#33781098)

So what you're saying is that science grants should be decided by people who know something about science? That's a great idea.

Re:Science by graphical bedazzlement (1)

rbmyers (587296) | more than 3 years ago | (#33783556)

Knowing something about science, unfortunately, is not enough. The problem with pretty pictures is that they are far too easy to make, and the level of detail offered by a typical fluid mechanical simulation implies something about the accuracy of the calculation that is often unsupportable in theory or in practice. What's the point of gorgeous pictures if the prediction is incorrect? We don't really know all that much about the detailed physics of hurricanes. Predictions of hurricane tracks are notoriously unreliable as have been "hurricane season" forecasts. Google "met office criticism" for a snapshot of the kind of criticism that the British office for predicting climate and weather has come under. The forecasters and the funders know *something* about science, but maybe not enough. My point here is that the engaging visual detail of fluid mechanical simulations has led to far too much uncritical acceptance of work that is often highly speculative and maybe, as a prediction, just flat out wrong.

Re:Science by graphical bedazzlement (1)

ceoyoyo (59147) | more than 3 years ago | (#33784242)

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?

Re:Science by graphical bedazzlement (1)

rbmyers (587296) | more than 3 years ago | (#33785844)

Scientists should be very careful about creating misimpressions of how well a problem is understood by misuse of color graphics. In the past, you would have gotten an "artist's conception." Now we get "simulations." The difference to which the actual physics are understood or accurately represented may not be all that great. When people discover, as some must have in the case of the Gulf oil spill, that what they're been fed is useless or worse, they rightfully become skeptical of the scientific enterprise. The fact that so much cutting-edge physics is still speculative is completely lost, and we wind up with misunderstandings of what science can and cannot do. It would come as a surprise to the general public, for example, that there is much about the simulation of fluid flows that is not understood. Computational "scientists" want their computers paid for and their work funded. What happens in the pursuit of that goal is often not only not science, but antithetical to science.

Car Analogy (1)

ijakings (982830) | more than 3 years ago | (#33780412)

Just some minor damage around the red shifting, thatll buff out.

Hopelessly confused by dark matter. (3, Interesting)

Anonymous Coward | more than 3 years ago | (#33780488)

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:Hopelessly confused by dark matter. (0, Troll)

insufflate10mg (1711356) | more than 3 years ago | (#33780562)

The Earth and Neptune and Sirius are all affected by gravity, why don't they simply clump up? Dark matter is quite accurately simulated in this endeavour, though we are unsure of the direct significance of the results. The dark matter reacts to semi-traditional gravitational forces, but only with other dark matter. Dark matter does not, in any way, react with the normal matter we are familiar with; this is because dark matter is simply the type of unusual matter that a black hole spits out once it absorbs regular matter.

The only possible interaction we could have with dark matter is when you turn on a walkie-talkie and hear static -- that static is deemed unpredictable simply because we can't model the dark matter creating it precisely enough. One of the reasons dark matter doesn't directly interact with light matter is because it can actually have nine electrons in its valence shell, hence making it unable to "fit" into the aether that we have access to. That being said, it is nearly impossible to accurately simulate its behavior and the scientists who took on this endeavour are to be praised for effort but ignored for their 'precision'.

Re:Hopelessly confused by dark matter. (1, Insightful)

Anonymous Coward | more than 3 years ago | (#33780588)

Bought that until you said "aether". Nice one! Almost got me to write an angry reply...

Re:Hopelessly confused by dark matter. (0)

Anonymous Coward | more than 3 years ago | (#33781454)

The scary part is, for all we know of dark matter he could be right.

Re:Hopelessly confused by dark matter. (1)

Black Parrot (19622) | more than 3 years ago | (#33780576)

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.

Re:Hopelessly confused by dark matter. (1)

wvmarle (1070040) | more than 3 years ago | (#33780840)

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 calculations simply do not match up with the observations. So then the calculations are amended until they match up with the observations, and in this case DM is introduced. What it is no-one knows, I have not even seen any reasonable explanations of what it could be, but it nicely makes calculations work out (especially as we don't know how much DM there really is so that remains a variable to play around with).

What is clear to me is that on astronomical scales, our gravitational models break down. We will have to come up with a new model - until then maybe continue to work with DM, for lack of a better solution. There is simply a lot we don't know about in this world, that's for sure.

Or think about the issue of the age of the universe. The current consensus is 13 bln years or so, but then you still hear about stars being of a similar age (the problem there is that they formed when the universe was considered still too hot for stars to form), or objects with possibly higher age, so that again is not something we can be really sure of. When this DM thing is settled we probably will also have to redo the universe age calculations.

Re:Hopelessly confused by dark matter. (1)

TapeCutter (624760) | more than 3 years ago | (#33781566)

"What it is no-one knows"

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.

Re:Hopelessly confused by dark matter. (1)

ceoyoyo (59147) | more than 3 years ago | (#33781126)

"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 you need friction to slow everything down and make it stick together. Dark matter wouldn't do that.

Re:Hopelessly confused by dark matter. (0)

Anonymous Coward | more than 3 years ago | (#33794104)

It's believed that dark matter does clump, under the relatively weak influence of gravity. In colliding enourmous structures, electromagnetic forces have a much greater effect on passing particles of gas, plasma and dust than gravity does, accounting for most of the slowing and eventual settling of these particles. Dark matter in both structures, which is not believed to interact electromagnetically, passes without substantial slowing. This would tend to create separation between dark matter and visible matter that was previously clumped together. Observations of the effects of this separation in clusters provide the most direct evidence we have of the existence of dark matter.

The largest, fast, safe, inexpensive virtual game (-1, Offtopic)

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Flash Center (1)

The Yuckinator (898499) | more than 3 years ago | (#33780572)

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 (3, Funny)

sensationull (889870) | more than 3 years ago | (#33780740)

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

Big Deal (1)

aashenfe (558026) | more than 3 years ago | (#33780764)

I have a screensaver that does this already.

meaningless (0)

Anonymous Coward | more than 3 years ago | (#33780782)

We can't explain why the galaxy is as it is but we think we can simulate galaxy's colliding? What the universe is expanding at an increasing rate!? But that doesn't fit.. oh wait.. here's some dark energy and dark matter... all good. What is it? Umm.. its something that makes the formulas add up.. nothing more. Is there a problem? Hey we don't want to mess with our "knowns"! Its easier to stick this on so it still works...

oh yes, dark energy (1, Informative)

goffster (1104287) | more than 3 years ago | (#33780802)

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".

Re:oh yes, dark energy (0)

Anonymous Coward | more than 3 years ago | (#33781062)

I call it "God"...

i call it a dimensional boundary (1)

chronoss2010 (1825454) | more than 3 years ago | (#33781792)

and were all sliding along and if you think extra dimensionally this boundary is everywhere but the more gravity you get the more you come into contact with it and as its a repellent it slides you away. THAT'S my lil theory....

Re:oh yes, dark energy (2, Insightful)

Kagura (843695) | more than 3 years ago | (#33782040)

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

Unless you still believe in the steady state theory.

Re:oh yes, dark energy (0)

Anonymous Coward | more than 3 years ago | (#33782574)

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

1. That's an opinion.
2. It's a distinction without a difference anyway.

The Flash Center? (1, Funny)

Anonymous Coward | more than 3 years ago | (#33780860)

Oh man, Apple's going to be pissed!

Re:The Flash Center? (1)

froggymana (1896008) | more than 3 years ago | (#33780972)

It should really be the HTML5 center.

Awesome use of computer power... (0)

vrythmax (1555425) | more than 3 years ago | (#33780978)

still no cure for cancer.

Re:Awesome use of computer power... (1)

suso (153703) | more than 3 years ago | (#33784398)

Also:

  • Climate change starting to affect things
  • No real defense against something like an asteroid hitting the earth.
  • Communications still affected by solar flares
  • Also, could you make the battery in my cell phone last longer.

But that's ok, we know what will happen when two galaxies collide.

Reached the same result with 200 lines of Python (1)

ttsiod (881575) | more than 3 years ago | (#33782620)

My naive Python simulator of gravity (200 lines) reached the same conclusion - expansion occurs. See the video and get the code from here: http://users.softlab.ntua.gr/~ttsiod/gravity.html [softlab.ntua.gr]

Pfft big deal (0)

Anonymous Coward | more than 3 years ago | (#33783118)

I've been doing this repeatedly for years using Xscreensaver.

Ah shit (0)

Anonymous Coward | more than 3 years ago | (#33783376)

A merger of two galaxies means the population of a least one galaxy will now all lose their jobs.

For a highly technical idea... (1)

Notquitecajun (1073646) | more than 3 years ago | (#33783430)

Imagine a Beowulf Cluster of these!

I've seen these in the 1990s (1)

peter303 (12292) | more than 3 years ago | (#33783652)

So they can make them 10,000 times larger now. Whats the point of this post?

I have the utmost faith in this model... (1)

rgviza (1303161) | more than 3 years ago | (#33794920)

... considering we can't even model our own climate with any semblance of accuracy.

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