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Space Observatory May Have Found Dark Matter
Posted by
ScuttleMonkey
on Mon Sep 01, 2008 09:36 AM
from the of-course-it-supports-their-own-model dept.
from the of-course-it-supports-their-own-model dept.
KentuckyFC writes to mention that new data from the orbiting observatory PAMELA may shed some additional light on the question of dark matter. Still only a preliminary announcement, the new findings apparently support the "Minimal Dark Matter" model, in which a particle called a "Wino" is responsible.
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How dark? (Score:5, Funny)
The answer is none. None more darker.
Re:How dark? (Score:5, Funny)
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Re:How dark? (Score:4, Funny)
The bigger question: why does this matter? Quit leaving me in the dark!
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Re: (Score:3, Funny)
Just so you guys don't have to stop joking, the actual particles making up dark matter are called either WIMPs (weakly interacting massive particles) or WINOs.
We're not quite sure what the difference is though, or even if they care. The democratic convention was underway so they were all unavailable for comments.
Re: (Score:2, Funny)
Dare we dream - dark aluminum?!?
Blame those who can't answer back (Score:5, Funny)
Thats right, when you can't find the real reason blame those too drunk to respond.
Winos are not responsible for every single badass event in the universe you know.
It could just as easily have been this Pamela woman.
A wino? (Score:5, Funny)
So it gets drunk on dark energy , trips over a neutrino and falls down a black hole where no one can see it?
Re: (Score:3, Funny)
One time I saw a wino eating matter before a galaxy collision with another galaxy
I was like "dude, you have to wait"
Re:A wino? (Score:5, Funny)
Perhaps that could also prove Hawking radiation. Winos get drunk and then eat too much, and then emit Hawking radiation all over the nearest park bench.
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Re: (Score:2)
Yes. Typically into a space-gutter.
Again? (Score:5, Insightful)
Re:Again? (Score:4, Informative)
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Re: (Score:3, Funny)
Welcome to the world of sensationalist media.
Yeah but this is /. -- that kind of sensationalist attention-grabbing headline removed from the reality of the actual story would never happen around here ;)
Re:Again? (Score:5, Funny)
This is the grown-up internet. You're allowed to say "fuck" here.
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Re: (Score:3, Informative)
From TFA:
Yep, it's very much as you describe. Many of these models push the boundary of what can be called 'theory' in scientific terms, but they are the best we have so far. I think what's getting people excited is that the observations mentioned in TFA are predicted by a dark matter theory.
Re:Again? (Score:5, Insightful)
I very often see articles saying the Dark Matter is found. This has been going on for years already. Articles titled "Dark Matter Found". But later another article pops up again saying "Dark Matter Found" ...
So basically, they just don't know?
No, it shows that bloggers and reporters (and slashdot editors) need to sensationalize preliminary results or possible explanations to get readers.
Parent
Re:Again? (Score:5, Interesting)
Galactic clusters do not appear to have enough mass to account for their speeds. Similarly, Galactic rotation curves flatten out as if galaxies were shaped spherical balls, even though we can see they are discs. The very first thing that astronomers reached for to explain these phenomena was as yet unseen, or "dark" matter.
Personally (I am a lay person astronomically), I think Dark Matter raises more questions than it answers. While I acknowledge the effort, time and rigor that many astrophysicists have put into studying these phenomena, I still feel that dark matter, a substance which is invisible, intangible, and undetectable expect through its gravitational effects is too far of a step for physics to take without more evidence. I feel as a theory, dark matter is only a stepping stone on the way to a better explanation for what we are observing.
I think the theory has fed off its own inertia. While "Dark Matter" was proposed in the 1930's by Zwicky, he meant it only in the classical sense, i.e. dust, dim stars, etc. The dark matter we hear about today seems to be a product of the 1970s, and is I think a result of the influx of particle physicists into the discipline of cosmology beginning in that period. The particle physics community has had a history of success using assumptions and models that are counterintuitive and often bizarre. The idea we hear most of today of more "exotic" and inscrutable dark matter stems I think from this camp.
The proposal of alternative theories has also ironically lead to wider acceptance of dark matter. By proposing alternatives, sides and factions were created, as will always happen among groups of people when topics are in dispute. When a theory like MOND fails in a particular case, this has the effect of strengthening confidence in the Dark Matter model, even though it should do nothing of the sort. Only sold predictions which emerge from a model should inspire confidence in it, and despite all the fanfare, we have no way of measuring dark matter, even indirectly. The distribution of the dark matter "halos" or spheres, is still an unknown, and some galaxies do not appear to need dark matter at all.
All that said, Feynman's rebuttal still applies. The laws of nature do not have to be philosophically pleasing to us. The universe does not exist for our mental gratification. It can be as strange as it wants to be, and if we don't like it, that's out tough luck. So if dark matter makes predictions, and they fit the data we see, then it is a good model no matter how strange its premises.
All that said, at this time I would bet on a better theory emerging at some later date. Exotic matter, while it may work in subatomic circles, will not I think stand up to scrutiny in the macroscopic domain.
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Re: (Score:2, Interesting)
Personally (I am a lay person astronomically), I think Dark Matter raises more questions than it answers. While I acknowledge the effort, time and rigor that many astrophysicists have put into studying these phenomena, I still feel that dark matter, a substance which is invisible, intangible, and undetectable expect through its gravitational effects is too far of a step for physics to take without more evidence. I feel as a theory, dark matter is only a stepping stone on the way to a better explanation for what we are observing.
That certainly is the nightmare version of Dark Matter. However, most (if not all?) dark matter models do not in fact propose (other than gravitationally) noninteracting particles. They certainly must interact very weak with each other and ordinary matter but not per se not at all.
Dark Matter models make in fact verifiable predictions, such as annihilation products and rates (positrons in this case). They are valid science!
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I thought there was work using gravitational lensing to show that there is a halo around many galaxies, and a few galaxies showed no such halo.
Re:Again? (Score:5, Insightful)
It has worked in the past, though. Remember how the observed motion of Uranus differed from the predicted motion? A hypothesis was put forward that the difference was due to the gravitational effects of a large body of dark matter. After some mathematical work, the likely location of the dark matter was deduced, someone went to a telescope and had a look - and there it was. Time to crack open the champagne and think of a name for it, how about 'Neptune'?
It has failed in the past too: the motion of Mercury also differed from what was predicted, and the hypothetical planet Vulcan was suggested as the cause. Yet after many searches, there was no sign of Vulcan. It wasn't until the general theory of relativity replaced Newtonian gravity that this was cleared up.
Whether we're about to discover another Neptune, or another general relativity, remains to be seen; the point is that the Universe is pulling something weird on us, and that's interesting.
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Re:Again? (Score:5, Informative)
There's a big distinction between the general dark matter theory and particular candidates for dark matter. The general picture is supported by numerous different lines of evidence: not just galactic rotation, but by gravitational lensing, the microwave background, structure formation, etc. It has been much more successful than any modified gravity theory thus far. It's a good model thus far, and we'll drop it if other observations come along.
There are literally hundreds of specific theories of dark matter's composition, however, and those are individually on shakier ground. These are mostly particle physics models emerging from the 1980s. There are an infinitude of papers and preprint suggesting this or that candidate and what signatures it could generate. They do all make predictions, however, and our observations are getting good enough to test many of them. Between astrophysics and particle accelerators we have a real chance of figuring this out (and the PAMELA observation seems unusually interesting!)... but there are a lot of overblown claims in the media in the meantime.
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Re: (Score:2)
so, you think that it is impossible for particles that do not interact with the EM force?
Re:Again? (Score:5, Informative)
There is definitely such evidence - it comes from Big Bang Nucleosynthesis. The idea is that the light elements (deuterium, helium, lithium) were produced when the early universe had temperatures conducive to fusion. This phase only lasted a few minutes, and the abundance of the light elements today depends sensitively on the conditions during this period. The abundance of deuterium tells us pretty clearly that the total mass of matter (which affected the temperature profile during nucleosynthesis) was much greater than the total mass of ordinary matter (which participated in the fusion process). Similar evidence comes from the cosmic microwave background.
Astrophysicists did not initially want to believe that the missing matter was exotic, but there's some extremely compelling evidence!
Parent
Belief != Acceptance (Score:5, Insightful)
The very first thing that astronomers reached for to explain these phenomena was as yet unseen, or "dark" matter. Personally... I think Dark Matter raises more questions than it answers.
The reason they reached for Dark Matter is that it is the simplest explanation. It is very easy to imagine that there is more mass there than you can see. It is a lot harder to start adding new forces or modifying existing ones. It certainly raises new questions but that does not exclude it from being the simplest solution.
dark matter, a substance which is invisible, intangible, and undetectable expect through its gravitational effects is too far of a step for physics to take without more evidence.
Er...what do you think we are doing? We are looking for that evidence. You are contradicting yourself here: we think DM is the best explanation to date so we are now looking for evidence to confirm it. If we had "taken the step" and truly accepted Dark Matter as the truth why would we bother searching for evidence of it? Also there are very good reasons to think that it interacts through the weak force as well as gravity - although it is not a requirement.
The particle physics community has had a history of success using assumptions and models that are counterintuitive and often bizarre.
We have? What part of particle physics is counter-intuitive? I think you are getting confused between Quantum Mechanics (which is very counter-intuitive) and particle physics. The Standard Model of particle physics is generally very simple, straight forward and easy to understand at a basic conceptual level - it is even sometimes taught at secondary school level.
When a theory like MOND fails in a particular case, this has the effect of strengthening confidence in the Dark Matter model, even though it should do nothing of the sort.
Why is this wrong? If, as is the current case, all alternative theories to DM have series flaws, then you end up with only one candidate theory to test so naturally there will be more work being done on it. I think you are confusing belief with knowledge. A lot of us believe that DM is likely to be correct but none of us know it to be correct. As the best theory to date there is a lot of interest in proving it correct so we look for data to do that.
we have no way of measuring dark matter, even indirectly.
Wrong - there are ways to measure it directly but they depend on the type of dark matter. We can produce it directly in the LHC, we can search for its interactions with nuclei in low background locations deep underground like SNOlab. These experiments have already put limits on what the Dark Matter could be. So far they have not seen anything but that does not preclude them from seeing it.
Exotic matter, while it may work in subatomic circles, will not I think stand up to scrutiny in the macroscopic domain.
Parent
Re:Again? (Score:4, Insightful)
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Re:Again? (Score:5, Insightful)
> So basically, they just don't know?
The newsies, you mean? Correct. They just don't know. And not just about dark matter.
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Re: (Score:2)
I very often see articles saying the Dark Matter is found. This has been going on for years already. Articles titled "Dark Matter Found". But later another article pops up again saying "Dark Matter Found" and it'll have a totally different explanation
I don't think you're paying very close attention to what's being reported. Dark matter research isn't continually contradicting itself with new explanations every week.
In the late 1990s, some dark matter was found in the form of MACHOs (basically, brown dwarves and things), but it wasn't enough to explain what all the dark matter was. Since then, more attention has focused on WIMPs (new kinds of particles). Observational studies have continued which have been able to exclude some kinds of WIMPs (e.g., it
Re: (Score:2)
Oops, I meant neutralinos, not gravitinos.
Re: (Score:2)
No, there is no evidence that dark matter repels normal matter. In fact, it seems to attract normal matter through the same gravitational laws.
Is that a troll? (Score:2)
I was always of the impression that even if you shed light on dark matter you still wouldn't see it, and if you did , we already would. But I commend the initiative, and wish the best of luck to any and all who attempt to shedding some light on the matter of dark, shed some dark on the matter of light mass, shed some mass in order to become become light, or even just light some dark sheds.
Re:Is that a troll? (Score:4, Insightful)
I've always heard the opposite... That dark matter isnt any different at all from normal matter, it's just that we don't know where it is. We know it's out there someplace because the mathmatical models rely on there being "extra" mass out there still work when compared to reality.
Parent
Re:Is that a troll? (Score:5, Funny)
I've always heard the opposite
I'm afraid the OP was correct. You can't shed light on dark matter because the dark will suck all the light, just like the sun sucks dark so hard that the friction of the dark moving to the sun causes it to become very hot. The flow of dark towards the sun interrupted by the earth causes the side of the earth away from the sun to accumulate dark, thus causing Night. As the earth rotates the dark caught on the night side can then be pulled off, this causing the absence of dark known as Day.
What we call light bulbs are truly dark suckers as well. That is why light bulbs are hot, just like the sun. When a light bulb is full of dark and won't suck dark any more, it cools off. If you look in old light bulbs you can even seen the accumulation of dark.
And when he said shed some dark on the matter of light mass, shed some mass in order to become become light I think he was referring to the fact that dark is heavier than water (in the oceans, the deeper you go, the darker it gets).
I don't know about lighting dark sheds bit, though. Maybe someone else?
Parent
Ah, Darkons. (Score:2)
Re: (Score:2)
Re: (Score:2)
To clarify slightly, there are two kinds of dark matter. There is "dark ordinary matter", which is just gas and dust that we can't find. We've now found most of that. The vast majority of the missing mass, however, is NOT ordinary matter. This is the mysterious part.
Dark? Pls explain (Score:5, Interesting)
Back when I was in particle physics, we would pronounce "wino" to rhyme with neutrino, but we would still snicker about it.
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Back when I was in particle physics, we would pronounce "wino" to rhyme with neutrino
Funnily enough, in Oz it's the other way round - they pronounce neutrino to rhyme with wino... !
Re:Dark? Pls explain (Score:5, Informative)
The charged wino would not be a reasonable dark matter candidate for just the reason you give: it would interact with light and we would have detected it by now. The dark matter candidate should be uncharged and thus a partner of an uncharged particle, e.g. a zino or photino.
There's a terminology issue, however (here comes the boring part). The electromagnetic (photon) and weak forces (W+/- and Z) are understood to be aspects of a unified electroweak force. In electroweak theory its more convenient to talk of 3 W fields (+/- and neutral) and one neutral B field. The photon is a mixture of the neutral W and B, the Z is another such mixture.
The most common dark matter candidate (the lightest neutralino) is a mixture of the supersymmetric partners of these particles: the neutral bino and neutral wino (and two neutral higgsinos). We could just as well say that we're mixing the photino and zino (and two neutral higgsinos), but bino and wino are more common terminology.
The paper is speaking about a dark matter candidate which is primarily the neutral wino, with a little admixture of the other states. Note that this doesn't mean the dark matter is composed of multiple different particles, just that the one particle it is composed of is "in-between" these labels.
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Re: (Score:2)
A correction to myself: As other posters note, there is no mention in this article of winos. They are possible dark matter candidates in other papers, however.
Re: (Score:2)
egkino artypino => ablino-2, idayfrino
Re:Dark? Pls explain (Score:5, Informative)
I think the summary is just wrong. The arxiv article doesn't mention winos at all... perhaps the summary writer confused it with WIMP?
The DM canidate is specified to be a
in the article itself
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Re:Dark? Pls explain (Score:4, Informative)
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Finding things... (Score:3, Funny)
So, scientists say they may have found Dark Matter, eh?
I bet it was in the last place they looked...
I'll get me coat...
Ah, well... (Score:4, Funny)
I assume they used Hobonic detectors.
Not wholly kosher (Score:5, Insightful)
The linked article is a summary of a paper that has an analysis of data not written by the original PAMELA team who collected the data. The PAMELA team have not yet published their data or findings, although apparently have presented them at a conference in Stockholm.
The summary quotes the paper thusly: "The preliminary data points for positron and antiproton fluxes plotted in our figures have been extracted from a photo of the slides taken during the talk, and can thereby slightly differ from the data that the PAMELA collaboration will officially publish."
I am not familiar with the conference in Stockholm that the PAMELA data were originally presented at, but at every large conference I have attended, it is official policy that no photographs are allowed. Taking unpublished data without permission of the authors is theft, pure and simple. Submitting a paper on that data before the original authors do is unethical.
Certainly, such proclamations are made with scant and incomplete information (it could be that Cirelli and Strumia, the non-PAMELA authors, did indeed get permission from the PAMELA team, and everything is kosher), and I hope that either members of the PAMELA team or authors of the new paper might read Slashdot to explain what's going on.
Re: (Score:3, Insightful)
> Taking unpublished data without permission of the authors is theft, pure and simple.
No it isn't. One cannot steal data. It might be copyright infringement, and it might be unethical, but it is not theft.
> Submitting a paper on that data before the original authors do is unethical.
I agree.
Re: (Score:3, Interesting)
Not everyone thinks that way. Some of us think that publicly presented information is fair game. And just because I have not spent the necessary ef
Re:GNU know it better (Score:5, Funny)
Wino is a recursive acronym for "Wino Is Not Observable"
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Re:GNU know it better (Score:4, Funny)
It's GNU/Wino, damnit!
-
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Re: (Score:2)
Well the very fact that we're talking about Wino means it is observable, even if only by the absence of something else.
Wine.
From winehq [winehq.org], "Wine is a translation layer (a program loader) capable of running Windows applications on Linux and other POSIX compatible operating systems."
From dictionary.com:
emulator. 1. to try to equal or excel; imitate with effort to equal or surpass
3. Computers. a. to imitate (a particular computer system) by using a software system, often including a microprogram or a