Galaxies Floating on a Dark Matter Stream

Darkman, Walkin Dude writes "A team in Switzerland has discovered that most of the small satellite galaxies around the Milky Way's near-twin, Andromeda, are lined up in a single plane that slices through Andromeda's spiral disc. Using images from the Hubble space telescope, soon to be decommissioned, the researchers found that 9 of the 14 of Andromeda's satellites lay on a relatively narrow plane bisecting Andromeda. From the article: 'The team believes the plane could have formed in several ways. In one scenario, the galaxies may have fallen towards Andromeda along an invisible filament of dark matter. Computer simulations show these filaments can form a cosmic web along which galaxies flow.'"

Comments

Sombrero Galaxies and You

[eldavojohn]

These are called Sombrero Galaxies. I believe M 104 is the most famous since it was first noticed on May 11th, 1781.

Does dark matter hold our universe together in a web? Perhaps, though this would mean that there is no such thing as truly empty space as a small amount of dark matter would have to exist. Perhaps what lays beneath the edges of our universe is nothing in the sense of it being devoid of dark matter?

Check this out:

Consider this fact: In the air we breathe, each cubic centimeter contains roughly 5 X 1019 atoms. In contrast, the intergalactic medium has a density of only 10-6 particles per cubic centimeter--each atom inhabits a private box a meter on each side. This would seem to suggest that there is not much matter in the intergalactic medium. But, given the enormous volume between the galaxies, it quickly adds up: The combined atomic mass of intergalactic gas exceeds the combined atomic mass of all the stars and galaxies in the universe--possibly by as much as 50 percent! There is indeed something in empty space

From this article.

While this article only mentions computer simulations, many scientific groups have gone along further researching, convinced that the cosmic web does exist. Some people have based most of their work on dark matter and the cosmic web though I believe it is still speculation and has yet to be accepted by the science community as a whole. I've read some crazy stuff about dark matter, like how it might be the "gravity particle" that is attracted to matter uniformly and causes the gravitational pull between objects. And even crazier books suggesting that the only way we'll ever be able to communicate between parallel existences is by lowering and raising these gravity particles.

Now, the slashdot community seems to be fairly educated and extremely opinionated so how about it--does dark matter exist? If so, since it is very difficult to detect, what are its defining properties?

re: Sombrero Galaxies and You

[InstrumentControl]

posted by eldavojohn:
        "Consider this fact: In the air we breathe, each cubic centimeter contains roughly 5 X 1019 atoms. In contrast, the intergalactic medium has a density of only 10-6 particles per cubic centimeter"

Probably a stupid question. For this amount of inter-galactic stuff, should there not be a significant amount of "scattering" of all
radiation ? Has or can this scattering effect been measured ?

Also, the linked article (www.newscientist.com/article.ns?id=dn2624) said that this stuff - "confined into filaments means that a very strong gravitational field must be pulling it into place. According to theory, only dark matter can do the trick." Why can only "dark" matter be the cause ?

I shall cast my shame unto the waters. I still do not understand "dark" matter. Would one of you good physical science people do some explainin' to a simple-minded redneck ?!?

Re:Sombrero Galaxies and You

[Stalyn]

Actually dark matter can be proved or disproved... it just hasn't been yet. Also there is indirect evidence for dark matter. Do you believe in String Theory? Dark matter has more evidence and theoretical weight than string theory.

Re:Sombrero Galaxies and You

[Tatarize]

Sure, seeing as there's no evidence for string theory and no evidence for Dark Matter we are currently 0 to 0. Now, string theory is an attempt to tie quantum mechanics together with relativity and kind of does that. But, Dark Matter is just an attempt to fix what we speed we think galaxies should rotate at according to Newton and what speed they do rotate at.

String theory at least has meshing two obviously true theories together, whereas Dark Matter has the job fixing bad math. And if this article's suggestion of galaxies riding an invisible stream of dark matter is any suggestion, it might as well be the great cosmic boogie-man of physics. Oh, your calculations don't add up... there must be dark matter. Halos of invisible matter that can't be detected by any way other than having our calculations wrong. I'm sorry, Newton's equations were just a stab at it. They work for our solar system. You don't make up new matter to fix wrong theories which honestly shouldn't work at the galactic level.

No, I don't have a better model for it. The suggestion that "Dark Matter is the best model we have," doesn't change anything. It's a bad model. How about back in the 1700s when all that vital element crap was the rage of Biology. There was no better theory. Having a sort of God molecule dividing the organic and inorganic was a crap answer, but it was the best we had at the time. It doesn't negate the fact that that too was a bad answer. Last I checked, nobody has really worked out a perfectly reasonable cosmology to explain why we had the Big Bang, although there's the answer that "God did it." This is, the only answer we have, should we accept that too.

Just because I don't have a better answer, doesn't make invisible halos of undetectable superheavy matter correct. I would need some actually solid evidence to suggest that that is the case before I accept it. Ockam's Razor would tend to suggest that bad math is a better explanation.

Eric Lerner

[Bloater]

The team believes the plane could have formed in several ways. In one scenario, the galaxies may have fallen towards Andromeda along an invisible filament of dark matter. Computer simulations show these filaments can form a cosmic web along which galaxies flow.'

Eric Lerner is looking less and less like a crank with every new cosmological experiment, I think this is exactly what his plasma filament theory of the intergalactic medium has been predicting.

a name for it

[heatdeath]

If they eventually find more evidence for these "dark matter streams", and start naming them, I think "the styx" would be a completely awesome name for such a stream.

He has fellow-travellers...

[leonbrooks]

...here. With some uberkewl photos to back up what they're saying.

Re:Dark Matter theory in laymen's terms

[Anonymous Coward]

unlike your childish gods, things like Dark Matter can be theorised and tested. It is still a relatively new theory and we lack the instruments to do the measurement. But that will come with time. Yet after thousands of years we still lack any hint of a proof of the existence of a "divine presence". You might as well be a native dancing around a sacred rock.

The enormous amount of resources wasted on churches and religion means that someone needs a slap in the face and i dont think it is the scientific community.

Dark matter and the multiverse

[alex_guy_CA]

I've heard Dr. Michio Kaku theorize that dark matter is the gravitational effect of the matter of other universes that are close to ours. I found that to be an intriguing thought, bringing two pretty wild ideas, dark matter and multiple universes, together in a coherent and even intuitive way.

ahref=http://www.mkaku.org/rel=url2html-18972http: //www.mkaku.org/>

Empty Space

[jd]

There is no such thing as empty space, as that would violate all kinds of laws of physics. (It would exist in a constant state of entropy, there would be zero quantum uncertainty, it would allow for the possibility of an absolute frame of reference, etc.)

In general, the popular belief is that ALL of space is filled with "quantum foam", which contains a mass of virtual particles whose sum (over any statistically significant volume) will be zero. These virtual particles are not "dark matter", precisely for that reason - dark matter (if it exists) sums to extremely large values.

These virtual particles are of all sorts and would include quantum wormholes and quantum black holes amongst others. Now, although on average quantum foam has absolutely zero impact, it can have very local, short-lived effects. Hawking radiation would be one. It may be possible these local variations can account for everything "dark matter" has been attributed to.

"Empty space" contains (according to theorists) all sorts of other exotic phenomena. "Superstrings", for example, which have negative gravity and essentially fill all of the other functions attributed to "dark matter" PLUS being one step closer to unifying gravity with all of the other forces, at the cost of having to live in a twelve-dimensional universe (or is it 15, now? Superstring theorists keep adding more.)

Again, though, superstrings would eliminate the need for "dark matter" and would even be a "better" explanation for the odd layout of those galaxies. The antigravitational effect of superstrings would rip apart galaxies that weren't threaded, so threading is exactly what you'd expect. (I wonder if they're POSIX threads?)

These all assume, of course, that anything new is required at all. Current theories that require something to be present may simply be consequences of being based on observation, as observation requires something to be present to be observed. You cannot observe nothing, because you can never prove that it truly is nothing, only that it lacks all the somethings that you would normally observe.

The gravitational models of the galaxy that required "dark matter":

• were based on Newtonian physics and took no account of relativistic effects on space, time, mass or distance. Nor did it take account of the finite speed of gravity. It also missed out on all quantum cosmology, though I couldn't name how that would impact things.
  
• lacked a lot of the information that has recently been discovered (such as the warped shape of some of the structure) which would mean that gravitational sources would be incorrectly placed
  
• have assumed the Milky Way to be stable, whereas it has collided with galaxies many times (and will do so again within the lifetime of our sun), which means that estimates of momentum in the early galaxy will be waaay off
  

Now, it can be argued that that was not the only model that required "dark matter", but I will argue that if we keep the dark matter in, we now introduce errors by having variables that try to compensate for something that doesn't happen. I will also argue that cosmologists should verify that ALL of the factors I've listed have in fact been taken into account with all these other "dark matter" scenarios.

This is not to say I'm convinced by the other theories, either. I don't like adding large numbers of variables purely to eliminate other variables. That's messy and a sign of really bad science. The quantum foam, for my money, seems to be the "best" of a bunch of really screwball ideas, and is probably sufficient to account for all of the effects that everything else is intended to describe.