Giant Sheets Of Dark Matter Detected

Wandering Wombat writes "The largest structures in the universe have been, if not directly found, then at least detected and pounced upon by scientists. 'The most colossal structures in the universe have been detected by astronomers who tuned into how the structures subtly bend galactic light. The newfound filaments and sheets of dark matter form gigantic features stretching across more than 270 million light-years of space — three times larger than any other known structure and 2,000 times the size of our own galaxy. Because the dark matter, by definition, is invisible to telescopes, the only way to detect it on such grand scales is by surveying huge numbers of distant galaxies and working out how their images, as seen from telescopes, are being weakly tweaked and distorted by any dark matter structures in intervening space.' By figuring how to spot the gigantic masses of dark matter, hopefully we can get a better understanding of it and find smaller and smaller structures."

So ...

[supun (613105)]

is it 1x4x9?

Re:So ...

[ObsessiveMathsFreak (773371)]

It's 1x4x9 + 6, obviously!

Re:So ...

[AKAImBatman (238306)]

Actually, it's just the walls of the Universe. The simulation uses a 32 bit number to handle the coordinate system, so it needed to fit within 2^32 light years. I told God he should have used a 64-bit processor, but he complained that they were too expensive back in 1970. I bet he's kicking himself now, eh?

Simulation error

[0xABADC0DA (867955)]

You joke, but consider if the universe were a simulation -- quantum mechanics makes a lot more sense in term of a simulation. Things like spooky action at a distance become lazy evaluation. Quanta become memory locations, variables. And so on. Quantum mechanics is easy to simulate.

But how does one simulate gravity? It has to propagate in every direction at the something like speed of light or else -- god forbid -- information could travel faster than light. The whole concept of gravity, that every individual particle affects however slightly every other particle, is not possible to compute directly.

Now suppose the universe were simulated as a sparse matrix. Each cell could contain a gravity component that stored the aggregate gravity force from each of a certain number of directions (perhaps expressed as several point masses). Depending on the number of directions this would give highly accurate simulation at a small scale, where error is absorbed as noise, while being computable for the overall universe as a whole. However the error would magnify over great distances due to 'floating point' type errors accumulating.

What if what these people are seeing as dark matter is not matter at all, but simulation error. Perhaps even dark matter is related to a sparse simulation of the universe where intervening space is approximated by invisible masses that gravity affects but nothing else does. These mass would act to consolidate cells in the matrix to reduce the overall memory requirements.

Re:Simulation error

[teslar (706653)]

You joke, but consider if the universe were a simulation -- quantum mechanics makes a lot more sense in term of a simulation. Things like spooky action at a distance become lazy evaluation. Quanta become memory locations, variables. And so on. Quantum mechanics is easy to simulate. But how does one simulate gravity? It has to propagate in every direction at the something like speed of light or else -- god forbid -- information could travel faster than light. The whole concept of gravity, that every individual particle affects however slightly every other particle, is not possible to compute directly. Now suppose the universe were simulated as a sparse matrix. Each cell could contain a gravity component that stored the aggregate gravity force from each of a certain number of directions (perhaps expressed as several point masses). Depending on the number of directions this would give highly accurate simulation at a small scale, where error is absorbed as noise, while being computable for the overall universe as a whole. However the error would magnify over great distances due to 'floating point' type errors accumulating. What if what these people are seeing as dark matter is not matter at all, but simulation error. Perhaps even dark matter is related to a sparse simulation of the universe where intervening space is approximated by invisible masses that gravity affects but nothing else does. These mass would act to consolidate cells in the matrix to reduce the overall memory requirements.

That always gets me. People assume the universe is a simulation (unprovable in my opinion) and then proceed to explain a very small subset of physical phenomena in terms of computations they understand. Where does this idea that the Universe simulator would work anything like our computers come from? Consequently, how does the assumption that the Universe is a simulation help in any way given that it is unknown what computations give rise to it?

Another way to look at it: Every time a physicist describes a new effect with a formula, he has in fact given you a (mathematical) simulation of this effect. But that does not mean that this effect is a result from a simulation in the first place. And just because it is possible to think of a computational implementation that might behave similarly to an observed effect (which is a crude way of describing it mathematically if you can't do the maths) doesn't mean it is the result of a computational implementation in the first place. Assuming the Universe is a simulation does not add any insights, so why bother?

Also kinda reminded me of that old joke... An engineer thinks his equations are an approximation of reality but a Physiscist thinks reality is an approximation of his equations (meanwhile, the mathematician doesn't care....).

Re:

[jgarra23 (1109651)]

But how does one simulate gravity? It has to propagate in every direction at the something like speed of light or else -- god forbid -- information could travel faster than light. The whole concept of gravity, that every individual particle affects however slightly every other particle, is not possible to compute directly.


If your hypothesis is correct then we wouldn't know the answer to this because we are not the ones running the simulation & whoever is obviously has technology & knowledge greater

Re:

[Urza9814 (883915)]

My god. We're all just a game of Spore!

Re:

[SETIGuy (33768)]

Quantum mechanics is easy to simulate.

[yoda] Tried have you? [/yoda] If it's so easy, can simulate a single atom for me? Let's say a Beryllium atom of the most common isotope? Compute the exact energy levels of all of the electrons, and all of the electronic transitions. Now compare them to measured values and tell me again how simple it is to simulate quantum mechanics.

Re:Simulation error

[by Anonymous Coward]

> "Aw, shucks... you guessed it! Now I have to stop the simulation and start over."

"There is a theory which states that if ever anyone discovers exactly what the Universe is for and why it is here, it will instantly disappear and be replaced by something even more bizarre and inexplicable."

"There is another theory which states that this has already happened."

  - Douglas Adams, HHGTTG

Re:

[dintech (998802)]

Dear Customer,

I would like to draw your attention to the eBay listing from which you purchased your universe. You'll notice that your warranty period has expired and God Inc. can no longer supply you with end-user support. If you would like to purchase a new universe please subscribe to the apropriate religion for your area.

Kind Regards,
God Inc.

So they didn't really detect dark matter then

[Crazy Taco (1083423)]

So from what I gather, this is still more pie in the sky from dark matter proponents then? It has been argued that we don't need dark matter to explain the universe, and that a minor tweaking of Newton's law of universal gravitation would explain everything. As of yet, no one has truly detected/demonstrated dark matter particles.

If our fundamental laws are a bit off, then this bending/distorting of the light would be explained by that, and these dark matter constructions would be nothing but an illusion created by a mathematical error in our first principles. Therefore, until someone can actually demonstrate a dark matter particle, I am not jumping on this bandwagon. There are experiments underway to actually find dark matter, and for now I await their results.

Heh

[TheLink (130905)]

Given that > 90% of the stuff out there is not even made of the same stuff like us - in the great scheme of things we are:
a) Interesting
b) Not interesting
c) Both (don't you love quantum superpositions ;) )

Re:

[KublaiKhan (522918)]

Interesting or noninteresting to -whom- exactly?

It's really probably just a point of view issue. After all, should there be 'dark matter organisms' of some kind, they'd be most likely supremely uninterested in the likes of us for anything other than curiosity value. However, we're rather interesting to us, being as we -are- us and we tend to be somewhat self-interested.

Re:

[spun (1352)]

Dark matter isn't antimatter. Antimatter isn't dark. Dark matter only interacts with regular matter (including regular antimatter) through gravity.

Re: Interesting / Not interesting / Both

[gnick (1211984)]

I typically consider myself Interesting, but I never really know for sure until mod points are assigned. Occasionally, I'm Funny, Insightful, Informative, or Overrated... Sometimes all at the same time!

Re:Heh

[Red Flayer (890720)]

d) harmless
e) we won't know until "they" open the box
f) mostly harmless

Re:

[MenTaLguY (5483)]

Yes, exactly. We're seeing the gravitational effects of large concentrations of mass, but that mass is neither blocking nor emitting light. Hence (for lack of a better name) we call it "dark matter".

Let me be the first to say

[QuantumFTL (197300)]

Take that MOND [wikipedia.org]!

Soon all your adherents will have to move to studying a crazy theory that can't disproven, like String Theory!

I hear Hot Topic are already interested

[Channard (693317)]

Sheets of Dark Matter? I guess that's this season's goth clothing range sorted out then. Just when you thought it couldn't get any blacker than SuperBlack [transstudio.com]

Three times larger?

[amstrad (60839)]

The Virgo Supercluster [wikipedia.org] is 200 million light years in diameter. And I'm sure there are large superclusters known.

Re:Three times larger?

[Wandering Wombat (531833)]

That's not really "One structure", though... it's a lot of small structures close together. A big pile of sand isn't the same as a big sheet of glass.

Re:Three times larger?

[TheEmptySet (1060334)]

It's a good philosophical question though. When is a collection of things (say atoms, bricks and mortar, etc.) a thing and when is it just lots of things? Deep down atoms don't come anywhere near touching each other to make molecules and larger structures. I myself am just a collection of tiny dots floating in space a long way from each other.

Re:Three times larger?

[Wandering Wombat (531833)]

Well, atoms interact strongly with eachother, to the point that homogenous iron can withstand forces in excess of a thousand times it's own weight. A school of fish, which is more accurately comparable to that cluster, is not one BIG fish... it's a bunch of small fish all hanging out in the same area, and although they are close together, it would be quite easy, compared to the size and mass and force of the group, for them to be pulled apart.

Re:

[SlowMovingTarget (550823)]

When is a collection of things (say atoms, bricks and mortar, etc.) a thing and when is it just lots of things?

As the venerable sage, Grover, taught us all so long ago... "Near!" *bounce* *bounce* *bounce* *bounce* "Far!" *bounce* *bounce* *bounce* *bounce* "Near!" *bounce* *bounce* *bounce* *bounce* ...

It all depends on one's perspective.

Sheets and Filaments

[TheEmptySet (1060334)]

So we are to understand that dark matter, acted on only by gravity, forms sheets and filaments? We know very well what shapes distributions of particles form over time with only gravity acting on them and they look a lot like galaxies and very little like sheets and filaments. Can anyone clear this up for me?

Re:Sheets and Filaments

[KublaiKhan (522918)]

Kind of an odd thing to do, isn't it?

However, galaxies also form 'sheets and filaments' at extremely large scales, as well; presumably, should these folks figure out how to find smaller structures, they should look somewhat more familiar.

Re:Sheets and Filaments

[JustinOpinion (1246824)]

First, remember that the distribution of dark matter and ordinary matter are, actually, pretty similar (we find galaxies accumulated along the dark matter filaments, and at smaller scales see dark matter concentrated into galaxies).

Second, my understanding is that dark matter (whatever it is) must be fairly weakly-interacting. The normal matter that we see aggregating into stars and galaxies interacts with itself (the particles bounce off each other, exchanging momentum, and also they repel each other at very short distances). This interaction, in addition to gravity, dictates the shapes we see for ordinary matter.

Dark matter doesn't interact strongly (with matter, and presumably with itself), so it aggregates differently. Imagine a cluster of dark matter that is being gravitationally collapsed: as the particles get closer to each other, instead of bouncing off each other (and thereby e.g. transforming their large-scale kinetic energy into heat), they 'pass through' each other (actually just pass by each other without scattering). This means that the matter will aggregate differently (the dark matter particles will mutually gravitate and orbit, but can't coalesce).

I'm painting a simplistic picture, but the point is that there are some fundamental differences about how dark matter interacts, versus ordinary matter. I believe the filamentary structure itself is an artifact of the universe's inflationary epoch, where massive expansion has amplified small-scale quantum fluctuations into the very large-scale distribution we now see.

Re:

[KublaiKhan (522918)]

It may be possible that dark matter interacts normally with itself, but its weak interaction with what we can see makes the problem of resolution difficult.

If I were feeling particularly sci-fi, I'd probably call it something like 'gravitational bleed-over from close neighboring dimensions'.

Re:Sheets and Filaments

[exp(pi*sqrt(163)) (613870)]

> We know very well what shapes distributions of particles form over time with only gravity acting on them and they look a lot like galaxies and very little like sheets and filaments.

No. When we try to predict the large scale distribution of matter using simulations [physorg.com] we get filaments.

Re:Sheets and Filaments

[LionKimbro (200000)]

More than just simulations -- if you look at the SDSS [sdss.org] data, you can clearly see the filaments. Mitaka [nao.ac.jp] is a good way to see a summary of the data on a PC; Switch to launch mode, and then zoom all the way out. You'll see the filament form as you get closer to the present (the center,) and see things more homogeneous at the edges (in the past.)

Re:

[exp(pi*sqrt(163)) (613870)]

Right. But it's important to show that theory and observation are in agreement here: both give you filaments.

pounced upon?

[Numbah One (821914)]

so the scientists are lol cats? Oh, hai drk mater! i pownse on u!

When LOLcats attack

[eviloverlordx (99809)]

We r in ur universe, messin with ur drk mattr sheetz.

Re:pounced upon?

[by Anonymous Coward]

Lots of scientists are lol cats, remember Schrödinger's lolcat? I can has superposishun?

Re:

[rasputin465 (1032646)]

so the scientists are lol cats? Oh, hai drk mater! i pownse on u!

haha. I can has Nobul Pryzze?

The Rubber sheet analogy is WRONG!!!

[jameskojiro (705701)]

The whole rubber sheet of space time analogy is wrong, it is missing something.

Current analogy of space time:

Take a rubber sheet and stretch it out over a frame and drop a bowling ball and marble and drop them on it, they push down and those dents are gravitation fields in space-time.

New more correct analogy:

Take a swimming pool and fill it all the way to the top with water. THEN, stretch a rubber sheet over it and seal it so that no water leaks out. Then put your bolwing ball and marble on it. Draw a line running between the bowling ball and marble, and take that cross section, note that the bowling ball and marble behave the same way at close distance like they do above, but when they are a opposite sides of the pool there is a slight "repulsive" effect. We call that Dark Energy! This repulsive effect also can help stick objects together applying a "pressure" against all the other objects, hence "Dark Matter". This effect will also affect light waves moving past it, hence gravitational lensing.

I'll take my Nobel prize now!

Re:The Rubber sheet analogy is WRONG!!!

[Wandering Wombat (531833)]

Scientists never get invited to pool parties... you're just making them feel bad now.

Makes a lot of sense, though.

Re:The Rubber sheet analogy is WRONG!!!

[TobyRush (957946)]

Scientists never get invited to pool parties...

And there's good reason. I grew up in Los Alamos, NM, and the best part about doing our swimming merit badges at the county pool was having the dad of one of the scouts -- a LANL physicist -- come early to pick up his son. He'd have all of us at the shallow end of the pool, and he'd be standing there holding a pendulum. Based on the pendulum's swing, he'd either yell "jump in!" and we'd all jump in simultaneously, or "get out" and we'd all get out simultaneously. After doing this for four or five minutes, the entire pool was sloshing back and forth, spilling over onto the deck on each end, getting everyone's towels wet if they weren't on the bleachers.

We thought it was awesome. The lifeguards didn't.

Re:

[jameskojiro (705701)]

Oh almost forgot the water pressing back upwards is like the way space time relieves the stress of having massive objects concentrated in one area. You press down on one area of space time and space time bulges out in another more distant area. It is like the packing dilema try putting 1000 ping pong balls in a box that can only hold 999, when you put int he last one and force it in, it will push another one out.

If you took all the matter in the universe and spread it out evenly, it would put the same "p

Re:

[sm62704 (957197)]

Ok, so you got this car, see, and it's flying around the moon... what? You people don't have flying cars yet?

Well sorry guys, you're just too primitive to understand REAL physics. [uncyclopedia.org] Come back when you figure out where you're going to keep all the necessary penguins.

What? You don't even know about the penguins? Shocking! You'll never reach lightspeed the way you're going.

-Al Facentuari

Re:The Rubber sheet analogy is WRONG!!!

[JustinOpinion (1246824)]

The "rubber sheet" analogy is imperfect, but I don't think your revised analogy is correct.

Draw a line running between the bowling ball and marble, and take that cross section, note that the bowling ball and marble behave the same way at close distance like they do above, but when they are a opposite sides of the pool there is a slight "repulsive" effect. We call that Dark Energy!

"Dark energy" doesn't mean that normal matter is repulsive at large distances. Ordinary matter is always gravitationally attractive towards other ordinary matter, at all scales. Same for dark matter (whatever it is). "Dark energy" is, in fact, a "negative pressure" that pushes on spacetime itself, causing the universe to expand (and moreover gets stronger and stronger the lower its density becomes).

If dark energy sounds counter-intuitive: it should! Of course we don't really know what it is (yet), but the experimental evidence available thus far does not suggest that matter is repulsive at large distances, but rather that "something" fills spacetime and exerts an expansion force that is inversely proportional to its density.

This effect will also affect light waves moving past it, hence gravitational lensing.

Just to be clear: gravitational lensing also has nothing to do with dark energy... and nothing to do with dark matter specifically. Any source of gravity (ordinary matter, dark matter, etc.) will deflect the path of light rays (the effect is small but measurable). Thus gravitational lensing is a great way to determine the "amount of mass" within a volume of space. When that mass is correlated with brightness, we say it's ordinary matter (stars, etc.) and when that mass is correlated with seemingly empty patches of space (dark), we call it dark matter.

Thread Count?

[by Anonymous Coward]

So what's the thread count on these sheets? And no weaving multiple superstrings at a time to inflate the number please...

Pounced upon?

[winkydink (650484)]

WTF? Were the scientists wearing kitten costumes?

Journal Reference

[phizix (1143711)]

The journal article is available at http://dx.doi.org/10.1051/0004-6361:20078522 [doi.org]

Holly? is that you?

[russ1337 (938915)]

Because the dark matter, by definition, is invisible to telescopes.....

Reminds me of a certain Red Dwarf episode (obviously discussing Black holes instead of Dark Matter):

Holly: Well, the thing about a black hole - its main distinguishing feature - is it's black. And the thing about space, the colour of space, your basic space colour, is black. So how are you supposed to see them?
Rimmer: But five of them? Five massively collapsed stars, millions of miles across. How could you miss them?
Holly: It's typical, isn't it? You wait three million years with nothing, then five come along all at once.

Gravity, it is wrong

[sweetser (148397)]

Or at least our current mathematical description of it is wrong. We cannot explain how disk galaxies spin. We cannot explain how the big bang happens without the magic fairy dust for inflation. Now we have a large wall of dark matter. Oh, and there is dark energy for galaxy acceleration. One more thing, we cannot quantize our approach to gravity.

These are the reasons I work on a rank 1 field theory for gravity. For the details, read as much of this thread as you like: http://physicsforums.com/showthread.php?t=87097 [physicsforums.com] This is a LONG thread, more than 36k views, I make learn things along the way. Right now I am trying to find derive the Maxwell equations, and then the unified field theory, instead of using tensors. Quite a bit of fun. I have never had to write so many partial differential equations in my life.

Doug

Re:How can they tell this is caused by Dark Matter

[Big_Breaker (190457)]

You are throwing up your hands WAY too soon and crying occam's razor.

Atmospheric distortions are not consistent over time or different locations and those distortions do not "lense" like gravity does. Also standard astronomic technique is to have someone confirm your results with a different telescope, in a different part of the world.

It may not be dark matter, but it's not a smudge on their mirror either.

Re:

[Big_Breaker (190457)]

The point is that the phenomenon is occuring out in space on a huge scale at a huge distance. It is not something occuring on Earth or even in our solar system.

I agree that "dark matter" is not necessarily the cause. It could be a gravity wave or some other mechanism not associated with mass.

Re:What if....

[exp(pi*sqrt(163)) (613870)]

> What if it isn't dark matter at all? But the Universe actually bending?

But that's exactly how it's being treated by physicists. Here [wikipedia.org] are the very equations that physicists use to described the bending of spacetime by matter, dark or not.

Am I smarter than a Scientist?

[by Anonymous Coward]

No, you are not. Damn that's the dumbest thing I've read on Slashdot in a while. You aren't a physicist, okay? Don't pretend like you have any idea what you're talking about. Don't assume that you know more than Ph.D.s who've been studying this shit for decades. They've seen the effects in all directions around us, you saying there's brown dwarfs hiding out in all directions? Just shut up, you're making Slashdot a stupider place with your very presence.