Scientists Expand Knowledge of Dark Matter 211
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."
How appropriate... (Score:5, Funny)
Nothing for you to see here. Please move along.
The dark matter that you can see... (Score:2)
-- Serious Black (attrib.)
Uncertainty (Score:3, Insightful)
Re:Uncertainty (Score:5, Funny)
Re:Uncertainty (Score:2, Funny)
Just another point of view (Score:5, Insightful)
Re:Just another point of view (Score:5, Informative)
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 [slashdot.org].)
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 (Score:5, Informative)
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 (Score:3, Informative)
We are considerably closer. The conceptual mechanism of turbulence is more understood now - it seems that turbulence is caused by finite-dimentional strange attractors [wikipedia.org] 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 exponenti
Re:Just another point of view (Score:3, Informative)
That's Navier-Stokes [wikipedia.org]
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Damnit! I follow every link to "strange attractor", because I figure that someday one is going to show Anjelina Jolie. Leave it to slashdot to disabuse me of that notion every damned time...
Re:Just another point of view (Score:3, Funny)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Isn't our concept of "chaos" just a matter of "too many variables" anyway? Or at least "too many variables to be easily comprehended?"
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Predictions allow you to check an existing hypothesis, but to make more progress requires a better understanding of what is actually happening.
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
The phrase "quantum mechanics" refers to both non-relativistic and relativistic quantum mechanics (the latter being quantum field theory). If you can't even get the lingo straight, what's the point in replying?
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
The courses at my uni appear to distinguish between vanilla Quantum Mechanics and Quantum Field Theory. Of these I've only taken the former, so I'm aware that my lingo may not be up to scratch.
Re:Just another point of view (Score:3, Insightful)
This is more
Re:Just another point of view (Score:2)
At the same time, I have to say it is Wolfram, the self proclaimed pioneer and genius, who wrote a book full of proofs that start with "I am quite convinced..." or "It seems to me...". But nevertheless some of the stuff he did is quite interesting.
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:2)
Re:Just another point of view (Score:4, Interesting)
Godel [miskatonic.org] 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
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 (Score:5, Insightful)
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 (Score:2)
Re:Just another point of view (Score:2)
I was going way OT, I was not talking about turbulence in particular I was agreeing with the GP who suggested there are things humans will never know.
"but this knowledge comes from outside the logical system"
Re:Just another point of view (Score:2)
Godel's theorem says nothing about "unknowability". It is about provability within a consistent axiomatic system.
I know any amount of stuff by means other than proving it within a consistent axiomatic system. I know my name. I know my favourite colour. I know I'm wasting my time trying to explain something on Slashdot.
Likewise, it is perfectly possible to know if a given theorem
Re:Just another point of view (Score:2)
A fairly canonical example of this idea is the continuum hypothesis. If you look at the counting numbers, you can put them all into one infinite
Re:Just another point of view (Score:2)
Our mind is a model of reality, I belive (but cannot prove) that it is based o
Re:Just another point of view (Score:3, Interesting)
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 entang
Re:Just another point of view (Score:3, Insightful)
Re:Just another point of view (Score:3, Insightful)
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 (Score:2)
Re:Just another point of view (Score:2)
I think that's a good example. "Spooky" is a good word - things we don't understand are, historically, spooky. So, since it's spooky, we should accept that we don't understand it.
The thing is, every so often a pretty simple theory comes along that explains these things rather elegantly. And then they're not spooky anymore.
It
papers linked to (Score:3, Informative)
Gravitational solution to the Pioneer 10/11 anomaly [arxiv.org]
Galaxy Cluster Masses Without Non-Baryonic Dark Matter [arxiv.org]
Galaxy Rotation Curves Without Non-Baryonic Dark Matter [arxiv.org]
Other Interesting stuff:
The Calphysics Institute [calphysics.org] and my earlier post [slashdot.org] about the Calphysics research.
Re:Just another point of view (Score:5, Informative)
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.
not consistent with observation (Score:2)
Re:Just another point of view (Score:2)
The Ministry of Silly Walks (Score:5, Funny)
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 (Score:5, Funny)
Re:The Ministry of Silly Walks (Score:5, Funny)
"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 (Score:3, Funny)
Telescopes of Unusual Size? (Score:2)
Re:The Ministry of Silly Walks (Score:2)
Dragonfly -
Damn Right, America's Got Optics! New'n Friggin' Largest Yet!
Ssshhhh... (Score:5, Funny)
Thats because we've secretly replaced the regular dark matter with Folger's Crystals!
Lots of it, and really damned hot? (Score:4, Interesting)
weird internal modes? (Score:2)
Maybe the dark matter has some kind of weird internal
Re:weird internal modes? (Score:5, Informative)
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:weird internal modes? (Score:2)
Now there may be other reasons to assume that there's also no weak interaction between dark matter a
Re:weird internal modes? (Score:2)
The SUSY partner of the neutrino, neutralino, is considered a WIMP and a dark matter candidate. But again this was before these findings so they might be cancelled out as well.
Re:So um (Score:2)
I suppose it could, but that wold be kind of like formulating geometry for the first time based entirely on a blurry photograph. I meant we have these huge super colliders which have given us pretty accurate measuements of the currently known forces. We've even fund that he weak and electro-magnetic fields perfectly align at certain temperatures. So without a way of testing, it still serves us best to fiddle with n
Re:Lots of it, and really damned hot? (Score:2)
Re:Lots of it, and really damned hot? (Score:2)
Re:Lots of it, and really damned hot? (Score:2)
The assumption is that at the dark matter can in principle interact with other things in the universe through non-gravitational means (most likely the weak force), so at some point in the early universe when reaction rates were much much much higher, it would have been in equilibrium with everything else (including the photons that would eventually become the cosmic microwave background (CMB)).
At some point the reaction rates would become low enough that the average dark matter particle
Re:Lots of it, and really damned hot? (Score:2, Interesting)
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 twink
Re:Lots of it, and really damned hot? (Score:2)
All of the asteriods and other rocky debris in our solar system is dark.
To my understanding dark matter is not defined as something that doesn't naturally give out light, but something that emits no light or radiation. The earth does emit light; that which is reflected off it from the sun, likewise for the moon. If I understand dark matter correctly, it wouldn't reflect the light from the sun, even i
Re:Lots of it, and really damned hot? (Score:2)
I thought the fact that dark matter has mass (and therefore substance?) was why galaxies hold together when they shouldn't. But how is that possible, if dark matter doesn't interact with normal matter in any observable way? And if it does interact with normal matter, where's it all hiding?
Re:Lots of it, and really damned hot? (Score:2)
Of course, light is affected indirectly through gravitation. However, normally gravitation doesn't shield light, it just bends it (the bending of light by the sun's gravitation was one of the first successful tests of General Relativity).
And yes, light would slow down a bit, since gravitation causes a slowdown of time (e.g. seen from space, the light on earth's surface is a bit slower, even when in
Re:Lots of it, and really damned hot? (Score:2)
Re:Lots of it, and really damned hot? (Score:3, Informative)
Re:Lots of it, and really damned hot? (Score:2)
Of course, different matter takes place in different interactions (e.g. only quarks and gluons take place in the strong interaction, electrons etc. don't; gluon and neutrino don't interact electromagnetically, the gluon doesn't even interact through the weak interaction). Now there's a priori no reason why there shouldn't be a particle which only interacts through gravity. (I couldn't im
Actually it makes sense (Score:2)
Re:Lots of it, and really damned hot? (Score:2)
I don't think that temperature is necessarily inconsistent with anything, but I've not read the papers yet.
No references (Score:5, Interesting)
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 (Score:2)
Re:No references (Score:3, Informative)
You mean now it's real? (Score:2, Funny)
Or for more of a
Obligatory (Score:5, Funny)
Dark Matter (Score:2, Funny)
"Scientists Expand Knowledge of Dark Matter" (Score:2, Funny)
AHAH... I got it!! (Score:4, Funny)
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
Re:AHAH... I got it!! (Score:2)
However, beware of the followers of the dark energy god religion. They argue that only dark energy can be the real god, because unlike dark matter, it's everywhere in the universe. Also it's powerful enough to accelerate the universe as a whole, while dark matter only acts in a galactic range. Also, the fact that we can learn something about the dark matter, like its distribution, shows that i
Re:AHAH... I got it!! (Score:2)
Still assumes the answer (Score:2, Insightful)
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 phl
Re:Still assumes the answer (Score:4, Informative)
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
Re:Still assumes the answer (Score:2)
I like your analogy. I fear it's correct.
In other news... (Score:5, Funny)
Re:In other news... (Score:2, Funny)
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
Interesting research... (Score:2)
Reminds me Homer, author of Illiad and Odyssey. We don't know if he existed, but we know he was blind.
Here's what makes me unhappy (Score:5, Insightful)
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
Inflation explained? (Score:2)
All Before . . . (Score:2)
Yeah, but it's like I was telling the Old Lady just the other night. It's really not so much the size, as how its used. I think Andromeda gets a whole lot more use out of itself than we do with the Milky Way. And, I find a hard time calling our galazy the Milky Way. I mean, Milky Ways have no nuts in them--and our galaxy
possibly related current publications (Score:2)
"... radial velocity measurements of red giants in the Galactic dwarf spheroidal (dSph) galaxy Leo I based on data taken with Gemini's Multiobject Spectrograph GMOS. These data, reaching out to the galaxy's nominal tidal radius, permit us to trace its velocity dispersion profile across the whole area of Leo I. By means of detailed dynamical modelling we discuss the implications on this dSph's dark matter halo and mass profile."
Popper is dead...long live predictions (Score:2)
Re:Dark Matter Blows (Score:5, Funny)
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:Dark Matter Blows (Score:3, Insightful)
-Rob
Re:What does local universe mean? (Score:5, Informative)
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! :)
Re:What does local universe mean? (Score:2)
Ah, bring back the days of the ancient Arabian astronomers who could come up with poetic names like Mintaka, Bellatrix, Deneb, Sirius... the Local Group contains galaxies with names like:
Re:What does local universe mean? (Score:5, Informative)
Re:Did they forget to carry the 2? (Score:2)
If there are only a few dozen people that can understand general relitivity, then I sincerly hope they've checked all their figures. Time for more automated equation verification?
Re:I say dupe... (Score:2)
Now, you cannot really shed light on dark matter anyway, because the light will just go through it.
Re:huh? (Score:2, Interesting)
We don't assume Omega=1... (Score:3, Informative)