Scientists Expand Knowledge of Dark Matter

nife00 writes "BBC News is reporting that British scientists at Cambridge have expanded the current understanding of the mysterious particles known as dark matter." According to the article: "[The Cambridge Team] has at last been able to place limits on how it is packed in space and measure its "temperature". "It's the first clue of what this stuff might be," said Professor Gerry Gilmore. "For the first time ever, we're actually dealing with its physics," he told the BBC News website."

Comments

How appropriate...

[Jugalator]

I just got this when first clicking on this article...

Nothing for you to see here. Please move along.

:-p

Uncertainty

[helioquake]

Give me the sensible error bar estimate on the mass, if they want to be scientific about it.

Re:Uncertainty

[drgonzo59]

They did, but it is very dark and hard to see.

Re:Uncertainty

[LiquidCoooled]

Holly: Well, the thing about a black hole - it's main distinguishing feature - is it's black. And the thing about space, your basic space colour is black. So how are you supposed to see them?

Just another point of view

[erroneus]

http://science.slashdot.org/article.pl?sid=06/01/2 5/1436243 -- This article points to the idea that there is no such thing as dark matter and explains everything with gravity. Now we're back to dark matter again? I still like science and all that but there are people who don't understand that "we don't really know everything" and that science as we know it today is merely an attempt at forming an understanding of our universe, not a definite mapping.

Re:Just another point of view

[drgonzo59]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate. For example the math works out for QM, but I don't think anyone can understand or conceptualize what is happening during entanglement (Einstein called it "spooky action at a distance" and never quite got to accept it).

Or when someone is talking about multi-dimensional spaces, it is easy to express it in a mathemtical form (R^6 or C^6), but what does that mean in reality, how would you think about such a space?

(Speaking of the 6 dimensions, there was an article on Slashdot about how the dark matter doesn't exist but instead we see what we do because "space has 6 dimensions".here.)

The point is that, just like dogs will never be able to solve integrals with the brain power they have now, so humans likewise might not be capable of understanding certain phenomena from the physical universe we live in.

Re:Just another point of view

[Beryllium Sphere(tm)]

That article dealt with only one kind of observation, namely how fast stars orbit the center of a galaxy.

Dark matter theory would be on pretty tenuous ground if it only explained one kind of observation.

There are features of the light from the Big Bang that are tough to explain without dark matter. The relative abundance of various nuclear isotopes is a sensitive gauge of conditions during the Big Bang, and again dark matter is the closest thing we have to an explanation.

>science as we know it today is merely an attempt at forming an understanding of our universe, not a definite mapping.

Isn't that the fun of it? My wife had a professor who always looked upward when he dropped a piece of chalk. He explained that we don't have real proof that gravity will always work, just an assumption that it will work like it always has, and if the chalk ever fell upward he sure didn't want to miss the event.

Oh, and that paper about explaining orbital motions without dark matter may have been mistaken in its methods. People who know more than we at Slashdot do have pointed out what they consider fatal flaws.

Re:Just another point of view

[meringuoid]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate. For example the math works out for QM, but I don't think anyone can understand or conceptualize what is happening during entanglement (Einstein called it "spooky action at a distance" and never quite got to accept it). Or when someone is talking about multi-dimensional spaces, it is easy to express it in a mathemtical form (R^6 or C^6), but what does that mean in reality, how would you think about such a space?

You needn't go off with such physical exotica as QM and multidimensional spaces. Conceptually they're weird, but they're relatively simple mathematically. Indeed, that's the great value of such mathematics: it gives us the language with which to accurately describe the unimaginable.

For a problem that seems to be truly beyond human intelligence, try turbulence. The mathematics to describe laminar fluid flows are well developed and understood, have been for centuries... but nobody has got the hang of turbulent flow. Even with supercomputer numerical simulations, you can only get so far. Proper modelling of turbulence has baffled the best minds for hundreds of years, and still we're not really any closer.

Re:Just another point of view

[S3D]

Proper modelling of turbulence has baffled the best minds for hundreds of years, and still we're not really any closer.

We are considerably closer. The conceptual mechanism of turbulence is more understood now - it seems that turbulence is caused by finite-dimentional strange attractors in phase space (good news because navier-stocks equations phase-space is infinetly-dimentional). The bad news is that strange attractors inherintly unstable in numeric simulations and amount of calculation grow exponentially with simulation time.

Re:Just another point of view

[killjoe]

It is said that on his deathbed Neils Bohr said "when I die, I am going ask god about relativity and turbulence. I think he can tell me something about relativity".

Re:Just another point of view

[jeffs72]

Sorry to be a stickler, but you're talking about one of my relatives :)

That's Navier-Stokes

Re:Just another point of view

[TapeCutter]

"could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate."

Godel has already shown that no system of description is adequate, this is independant of of the amount of brain power on hand (or in head). People often wonder why maths is so good at describing the Universe, I belive it is because it is actually describing the model used by the brain to create the illusion of "I". ie: The simulated Universe containing the simulated self we all carry around in our heads. The "physical universe we live in" is an illusion.

A favourite quote from the above link: Although this theorem can be stated and proved in a rigorously mathematical way, what it seems to say is that rational thought can never penetrate to the final ultimate truth ... But, paradoxically, to understand Gödel's proof is to find a sort of liberation. For many logic students, the final breakthrough to full understanding of the Incompleteness Theorem is practically a conversion experience. This is partly a by-product of the potent mystique Gödel's name carries. But, more profoundly, to understand the essentially labyrinthine nature of the castle is, somehow, to be free of it.

I find the quote interesting because it relates a similar experience to religious conversion, ie: acceptance of the unknowable.

Re:Just another point of view

[awol]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate.

Absolutely. To detect something one must have a tool of finer resolution than the thing itself. By corollary to understand something must one have a tool that has a "finer" resolution? I believe that one cannot understand things like entanglement with a lump of tissue (ones brain) that does not itself have the capacity to make use of entanglement (or the like) itself. As such there are things that are beyond the resolution of our reasoning organ.

What is kind of exciting is the idea that we might build a machine that is not so limited to harvest the impact of these incomprehensible quantum events. Much like we have build machines to exceed the mechanical limits of our physical bodies (cars, cranes, planes etc). It will be weird though when we start to rely on machines that are using results that the machines cannot explain to us because our brains are inadequate.

Re:Just another point of view

[Starker_Kull]

Actually, Godel did no such thing - he demonstrated that in any formal system of logic sufficiently complex to encapsulate basic arithmetic, there will be unprovable statements which are nonetheless true. Note that the reason we can say these unprovable statements are true is because that if they were false, there would exist a provable counterexample to the statement (i.e. an example of the falseness), and thus the statement would not be unprovable - but this knowledge comes from outside the logical system. In other words, he demonstrated that there will be true statements in a logical system that can never be proven within that system to be true; a hypothetical example might be Goldbach's conjecture, that any even number > 4 is the sum of two (not necessarily distinct) primes. If this was, in fact, true, but was somehow "unprovable", we would be left in the uncomfortable position of seeing billions of examples where it is true, not a single example where it was false, but of course there would always be an infinity of cases we didn't check yet. This is, in fact, the present state of our knowledge - and thus why I used it as an example. Of course, some clever egg might stumble upon a proof of Goldbach's conjecture tomorrow - people used to use Fermat's Last Theorem as a potential example of something that might be true but unprovable, until Wiles proved it. This is the problem, that we have no way of knowing what is unprovable in mathematics, because if we did have such a way of "knowing" (i.e. proving that a proposition is unprovable) for a specific proposition, we would have just proven it true, and thus it would not be unprovable! So we will never know what is not provable - we will only suspect that one of Godel's unprovable but true phantasms is staring us in the face.

My point (longwindedly) is that this has little or nothing to do with the physical, mathematically modeled, problems at hand here; if you want a better idea of the type of barrier we are facing in this case, you would be better served by complexity and information theory; look up Shannon and Chaitin for more info - that is the type of problem involved in turbulence simulation, not logical issues of provability and incompleteness.

Re:Just another point of view

[Capt'n Hector]

*Ahem*. Dogs certainly do know calculus.

Re:Just another point of view

[Mr. Slippery]

I was actually wondering, could it be the case that we might not even be able to understand and explain some phonemena simply because our brain power is not adequate.

It sometimes strikes me that every model of the universe is an instance of lossy compression; it's small enough to fit into the human mind and gives you the gist of what's going on, but data is lost.

Re:Just another point of view

[drgonzo59]

Well, that was the point of my post. We are using QM to build things. The math seems to predict the phenomena. Quantum encryption works with entanglement and there has been experimental proof. But it seems that we cannot really understand it. Other phenomena are likewise. So I was wondering whether there is actually a limit as to how much our brains can understand. In other words some phenomena we will comprehend as the science progresses, but some we will never be able to wrap our head around.

This is more of a philosophical debate I guess. Some scientists have claimed that knowing the math and having the equation is all we need, there is no need for conceptual models in our head. Others claim that is not enough and they would want to understand what is really going on.

The Ministry of Silly Walks

[malia8888]

Using the biggest telescopes in the world, including the Very Large Telescope facility in Chile, the group has made detailed 3D maps of the galaxies, using the movement of their stars to "trace" the impression of the dark matter among them and weigh it very precisely.

Doesn't the name "Very Large Telescope facility" sound like it is out of a Monty Python sketch, sort of like the "Ministry of Silly Walks"?

Further, I am struck with the thought that dark matter is "Silly Putty" which has gone off a bit.

Re:The Ministry of Silly Walks

[(negative video)]

I'm personally more amused by the proposed OWL telescope, which stands for OverWhelmingly Large. It's makes you wonder what they will call the next one after that. The So Enormously Large that Gosh We're All Really Impressed Telescope?

Re:The Ministry of Silly Walks

[fruey]

"The So Enormously Large that Gosh We're All Really Impressed Telescope" sounds like it just might be accepted, were it not for the fact that the acronym SELGWARIT is a little difficult to remember, and lacks punch or reference to an animal with good eyesight (or a large animal, perhaps).

You could however, with minor adjustments, get it sounding just nice with a good acronym to boot, viz : ELEPHANT Enormously Large Exceedingly imPressive Huge Array mind-Numbing Telescope".

Re:The Ministry of Silly Walks

[maxwell demon]

That's nothing against T.REX, the Telescope of Really EXtreme size!

Ssshhhh...

[Donut2099]

"For the first time ever, we're actually dealing with its physics,"

Thats because we've secretly replaced the regular dark matter with Folger's Crystals!

Lots of it, and really damned hot?

[interiot]

The article mentions that there's quite a bit more of it than normal matter, and that it's about 10,000 degrees (... C?). Is that consistent? It just sounds odd for dark matter to have such a higher energy level than normal matter, weakly interacting or not.

Re:Lots of it, and really damned hot?

[LiquidCoooled]

I wondered this as well.

Technically, shouldn't anything which doesn't emit light come under the banner Dark Matter?

The Earth and Moon don't naturally emit light so would be difficult if impossible to see with a telescope.
All of the asteriods and other rocky debris in our solar system is dark.

All of this is moving at a lot more than a few centimeters a year.

There can't be that much large fragments in the blackness of space because they would block our own view of the stars and lots more would appear to twinkle than currently are seen to? (negate atmosphere by using hubble)

Re:Lots of it, and really damned hot?

[Starker_Kull]

That's the amusing part; as far as I understand it, no. The whole dark matter thing is rather touchy because of this - it describes something that only interacts via gravity. Remember that our sense of "interaction" (touching, burning, etc.) are all based on electromagnetic forces, so this dark matter could be passing through us right now and we would not notice it (much like neutrinos, which pass through us by the billions per second). Of course, at least neutrinos have the decency to OCCASIONALLY interact with normal matter, or we would have never detected them at all, only hypothesized their existence to make various important laws (like conservation of momentum and particle spin) work.

It's an intriguing idea, though. The reason ordinary matter piles up into big chunks like planets and stars is not just gravity, but the OTHER forces that keep it "stuck" together. Without that, matter would just be cruising along, looping around due to gravity, perhaps even "colliding", but without a method of storing or dissipating their kinetic energy (chemical bonds, which allow "heat" or vibrational motion energy), they will never stop moving or agglomerate or anything like that, making them more like a perfect gas without a container but with gravity. Neat stuff.

I just hope there is some way of directly detecting this dark matter (have it interact with something in a particle chamber in such a way that dark matter is required to explain the observation), or at least have it fall naturally out of the Standard Model or a successor, or it is going to have an aethereal feel (pun intended) about it.

No references

[Random Walk]

I'll probably never understand why newspapers are never able to quote any references for their news. Even in the absence of a published refereed paper, I would expect that there is at least a preprint or press release from the research group... apparently BBC news is convinced that their readers will drop dead on the floor if they encounter a hyperlink leading to something more than just random blurb from a journalist.

Actually, they don't even say whether 'Professor Gerry Gilmore' is part of the group that did this research, or whether he is just someone they asked 'Hey guy, what do think about this stuff?'. I.e. they don't even identify clearly any member of this 'Institute of Astronomy, Cambridge, team'.

Re:No references

[FinestLittleSpace]

The BBC news 'lack of linking' can get on my nerves a bit, but they DO hide in the right hand bar a 'related links' section whihc you can just about see....and is sometimes useful

papers linked to

[Falcon040]

Links here for related papers:

Gravitational solution to the Pioneer 10/11 anomaly
Galaxy Cluster Masses Without Non-Baryonic Dark Matter
Galaxy Rotation Curves Without Non-Baryonic Dark Matter


Other Interesting stuff:
The Calphysics Institute and my earlier post about the Calphysics research.

You mean now it's real?

[Zadaz]

I thought measuring the temperature of dark matter was like measuring the distance to the celestial sphere.

Or for more of a /. reference, like measuring the quantity in the bit bucket.

Re:Dark Matter Blows

[meringuoid]

Dark Matter should hook up with the cosmological constant, they'd make the perfect couple.

Already done; look up 'dark energy'. Now, if you'll excuse me, I've left my dinner in the oven and I think it's burning; I smell phlogiston. Damn, with such delays I'll never get this new suit ready for the Emperor in time...

Re:What does local universe mean?

[meringuoid]

"It now looks as though the Milky Way is the biggest galaxy in the local Universe, bigger even than Andromeda. It was thought until just a few months ago that it was the other way around."

Could someone explain what the "local universe" is? And how does this compare to the entire universe?

Our local cluster of galaxies - which IIRC consists of three giant spirals and a whole bunch of small cloudlike galaxies - is unimaginatively titled the Local Group.

Hitherto it's been thought that the Andromeda galaxy was the largest in this group, with our own Galaxy about two thirds its size. Now, it seems that's not the case... damn, my childhood astronomy books lie to me again! :)

Obligatory

[SeaFox]

So I guess you could say they're shedding some light on dark matter?

Re:What does local universe mean?

[joe user jr]

Probably they mean the Local Group: "the group of galaxies that includes our galaxy, the Milky Way. The group comprises over 30 galaxies, with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a 10 million light year diameter (see 1 E23 m for distance comparisons). The group belongs to the Virgo Supercluster."

Dark Matter

[ben_1432]

What's so hard to understand about it? It's the heaviest, densest matter available and it powers spaceships duh. Oh yeah, and Nibbler craps it.

"Scientists Expand Knowledge of Dark Matter"

[Anonymous Coward]

... they're making dark matter smarter?

AHAH... I got it!!

[DaedalusHKX]

Dark Matter == God.

Yep... dark matter and he who cannot be seen are one and the same... see?

Now, onward to forming a new religion.

Dark Matterism.

I wonder what country we'll butcher to spread THAT religion??

Anyone??

~D

Still assumes the answer

[AlecC]

I was hoping that this would provide some real evidence for Dark Matter. I have a problem with something so massive which, as far as I can see, is invented to explain a single fact: the anomalously fast rotation of galaxies.

But this article doesn't do that. It says, as I understand it, if the rotation of galaxies is caused by dark matter then dark matter has these properties. If the unexpected rotation is caused by something else, then this is just a curious kind of meta-measurement,

It is a bit like the phlogiston theory. If fire were caused by the release of phlogiston, you could measure the mass of phlogiston - and come out with a negative mass. Which is perfectly logical, but counter-intuitive. Further investigation then makes the phlogiston theory even less attractive - but in the short term, the theory can be patched to work.

Re:Still assumes the answer

[rknop]

I was hoping that this would provide some real evidence for Dark Matter. I have a problem with something so massive which, as far as I can see, is invented to explain a single fact: the anomalously fast rotation of galaxies. ...and the anomolously high velocity dispersion of clusters, and matter evolution models that go from the observed fluctuations in the Cosmic Microwave Background to the observed distribution of matter today, and the anomalous amount of gravitational lensing seen in various cluters...

The galaxy rotation curves are the cleanest and best piece of evidence, but there's a lot of evidence for dark matter. It's a major paradigm in astronomy, without which quite a number of things would be lacking an explanation.

-Rob

In other news...

[jettoki]

British scientists at Cambridge have also placed limitations on the possible properties of the luminiferous aether. "We're pretty sure it's not yellow," says one researcher, "and we've also ruled out blue and pink. It's nice to know that we'll soon have figured out both this dark matter stuff and the luminiferous aether. Then we can start puzzling out those epicycles again."

Re:In other news...

[maxwell demon]

Of course, dark matter and luminiferous aether are one and the same. Isn't that obvious? This explains immediatly why we cannot see it: It's not something in the way of light, but it's the medium of light itself!
BTW, the dark energy is also solved. It's phlogiston. You know, phlogiston has negative weight, therefore it causes anti-gravitiaion. This neatly explains why dark energy causes acceleration of the universe expansion.
The epicycle problem isn't yet completely solved, but it's likely that the enormous heat of the dark matter comes from the friction of the planetary machinery.

Re:weird internal modes?

[Stalyn]

What the findings suggest is that dark matter isn't exotic matter but a different kind of matter all together. The hierarchy of forces according to interaction goes gravity -> electroweak -> strong. This means all matter we know of interacts with gravity, all matter (until recently) interacts with the electroweak force and a subset of matter, quarks, interacts with the strong force. Note, quarks also interact with the electroweak force since protons and neutrons have electric charge and these particles are made of quarks. However leptons, like the electron do not interact with the strong force.

Now it was possible that dark matter could interact with the electroweak force but very weakly and therefore undetectable at large scales. It was assumed that this meant they were very cold and at very low energy states. However if they are moving at 9km/s that would mean they have high energy states. Therefore if they did interact with the electroweak force, they would be absorbing or emitting photons. But they aren't.

So we have a new type of matter with that only interacts with standard matter(leptons, quarks) via the gravitational force.

Re:Dark Matter Blows

[rknop]

It's always fun to watch people on Slashdot without a clue what they're talking about dismiss so much of our current understanding of cosmology with such an unjustified supercilious attitude.

-Rob

Here's what makes me unhappy

[rknop]

Here's what makes me unhappy:

The Cambridge University team expects to submit the first of its results to a leading astrophysics journal in the next few weeks.

I don't like this "press release before publication" mode of doing science. It's all about making sure that you get the attention and public recognition, and not about propery distributing the results so that others can understand and evaluate what you've done. Alas, it seems that Marketing Is All in the modern world, and not just in the USA any more. You can be sure that the institutions who house these scientists love to get the attention and so forth.

I'd be happier if the paper had already been accepted by some real journal, with a preprint available on www.arxiv.org. As it is... we have a press release and a pop-sci article about an intersting result that's hard to truly evaluate. The article is mostly good and sounds reliable, but in my experience these pop-sci articles usually get something wrong. (For instance, even though 10,000 degrees sounds "hot", given the likely mass of the Dark Matter particle, it still is "cold" in the cosmological sense of "cold dark matter", which really means "nonrelativistic dark matter". I'm not sure how much of a surprise that temperature is, but it's probably not enough to make CDM wrong.)

-Rob

Re:huh?

[Myrano]

I'd guess they just mean the local cluster of galaxies, that is, the group of galaxies around us that we are gravitationally bound to. It's been known for a while that the Milky Way is larger than average, but Andromeda (which we are on a collision course with) was thought to be larger than us. I'm skeptical, myself, but it would be awesome if we did turn out to be bigger. 'Cause that kind of thing is cool.

We don't assume Omega=1...

[jpflip]

Dark matter is thought to make up >80% of the matter (slow-moving stuff which clumps under the influence of gravity) in the universe. There are lots of reasons for thinking that this stuff is out there:

• galaxy rotation curves (you're right that this alone doesn't tell us about the universe's energy budget, just that of galaxies)
• gravitational lensing (a surprisingly independent measure of the stuff in galaxies and galaxy clusters)
• structure formation (you need more matter than the visible amount for the structure we see to form quickly enough)
• the cosmic microwave background (the shape of the first two peaks of its spectrum tells us about matter and dark matter densities)

Dark energy seems to make up the remaining 70% (25% dark matter, 5% ordinary matter). The evidence for this comes from the acceleration of the universe's expansion, which is a fairly amazing thing.

You don't actually need to assume that Omega=1 (the universe is flat), because these different lines of evidence pick out a unique consistent solution. There's a great plot at LBL showing this. We don't need an ad-hoc assumption that Omega=1 anymore!