Join 3,572 readers in helping fund MetaFilter (Hide)


UniverseNewsFilter: Scientists claim to have detected dark matter
May 15, 2007 9:12 PM   Subscribe

UniverseNewsFilter: Scientists claim to have detected dark matter! Here are NASA's press release, feature page and multimedia presentation. For an explanation what dark matter is, I refer you to this page. After all that excitement, you can sit down and work out how much dark matter is in the Milky Way.
posted by Kattullus (30 comments total) 3 users marked this as a favorite

 
Didn't they say that last year? I mean its not like dark matter is a controversial idea, and technically the earth and everything on it is made up of "Baryonic" dark matter. Normally when people talk about dark matter they mean "non-baryonic" dark matter. Even then, the idea of non-baryonic dark matter is not that controversial. If someone figured out what it was then that would be a big deal.
posted by delmoi at 9:20 PM on May 15, 2007


At last, direct evidence of phlogiston aether handwavium dark matter!
posted by semantic scope at 9:23 PM on May 15, 2007


Man, that sounds oddly familiar.
posted by cortex at 9:27 PM on May 15, 2007


oy
posted by longsleeves at 9:29 PM on May 15, 2007


...work out how much dark matter is in the Milky Way.

Not nearly enough, if you ask me.
posted by Zinger at 9:33 PM on May 15, 2007


Zinger - I hear they make them with pig fat now.
posted by Artw at 9:34 PM on May 15, 2007


Hey now, while I publicly recanted my belief in the existence of handwavium, I still haven't given up hope on phlogiston. The Stahl-Becher model of the Universe explains a lot that other, newer and shinier theories don't, such as why it burns when I pee.
posted by Kattullus at 9:34 PM on May 15, 2007


I'm tucking into a nice big slice of Devil's Food in your honor, Kat.
posted by Dizzy at 9:35 PM on May 15, 2007


It's really made of nougat.
posted by Balisong at 9:45 PM on May 15, 2007


"When endeavouring to explain the aforecited experiment, it seems to me that most philosophers were blinded by a desire of victory, or distinction, and therefore have obstinately adapted the facts to their hypotheses, exhibiting indolence in avoiding laborious speculations that might have led to the discovery of the true laws of nature."
posted by semantic scope at 9:50 PM on May 15, 2007


Ok, so wtf is it? Great post Kattullus, but it's still a teaser!
posted by orthogonality at 9:53 PM on May 15, 2007


But uv course dark matter vus inwented by the Russians!!!
posted by ZachsMind at 9:57 PM on May 15, 2007


I haven't tried to keep up on the details, so maybe there's a reason for why the cosmologists keep trying to explain dark matter as being something esoteric.

It doesn't seem to me that such weird stuff (e.g. WIMPS) is necessary. All you need to do is look at pictures of the Sombrero Galaxy and it's pretty obvious that there's a lot of dark matter, and it's pretty ordinary dust and stuff like that.
posted by Steven C. Den Beste at 10:15 PM on May 15, 2007


Meh. It's just the soul of Jerry Falwell, released from its fleshy prison.
posted by UbuRoivas at 10:18 PM on May 15, 2007


it is sensible to suppose that phlogiston alone provides the key for understanding the whole of reality

Exactly, semantic scope (great find).

Orthogonality, apparently, if we could see it and it span inside a cube, this is what it would look like (quicktime). As to a proper answer to your question, I'd rather leave that to people who can tell their ass from their Higgs boson.
posted by Kattullus at 10:22 PM on May 15, 2007


Note to SCDB and delmoi.
posted by weapons-grade pandemonium at 10:25 PM on May 15, 2007 [1 favorite]


Which part of this is The Force?
posted by stavrogin at 10:54 PM on May 15, 2007 [1 favorite]


Last year's kickass Chandra observations of the Bullet Cluster seem like a pretty viscerally convincing piece of evidence for some kind of dark matter other than the usual cold gas and dust. (I don't know whether that particular observation rules out, say, zllions of cold starless planetoids, though.)
posted by hattifattener at 11:05 PM on May 15, 2007


Models suggest that about 23 per cent of the total mass is made up of dark matter, while the remaining 73 per cent is something even odder: a dark energy that drives the Universe’s expansion.
Next: mimes present their views on string theory and teen pop divas discuss conformational changes in DNA due to steroid hormone binding.
posted by Slithy_Tove at 11:51 PM on May 15, 2007 [2 favorites]


enlightenment
utube french commentary
posted by hortense at 11:53 PM on May 15, 2007


To quote the first link:
James Jee, of Johns Hopkins University in Baltimore, Maryland, who led the discovery team, said: “This is the first time we have detected dark matter as having a unique structure that is different from the gas and galaxies in the cluster.

The bullet cluster has the dark matter tracing the galaxies but not the gas. So it's maybe an interesting result from that perspective I guess. As Jee continues:

"Although the invisible matter has been found before in other galaxy clusters, it has never been detected to be so largely separated from the hot gas and the galaxies that make up galaxy clusters.

“By seeing a dark matter structure that is not traced by galaxies and hot gas, we can study how it behaves differently from normal matter."


I'm yet to see any papers myself yet, but it sounds like it'll be interesting in what it tells us about dark matter as well as giving us more evidence that it really is out there.

Lastly, as weapons-grade pandemonium links, it has to be mostly nonbaryonic - notably big bang nucleosynthesis tells us how many atoms we can have.
posted by edd at 1:44 AM on May 16, 2007


NewScientist has an interesting article this month about colliding Universes(!) - if there are multiple Universes, they could be colliding with each other - since other Universes have different types of matter and laws, they may pass through un-noticed, but may leave a signature in the background radiation, pattens such as the "Axis of Evil". Some research here.
posted by stbalbach at 5:36 AM on May 16, 2007


It doesn't seem to me that such weird stuff (e.g. WIMPS) is necessary. All you need to do is look at pictures of the Sombrero Galaxy and it's pretty obvious that there's a lot of dark matter, and it's pretty ordinary dust and stuff like that.

I haven't tried to keep up on the details...

Or even the basic ideas, sounds like. You think astronomers don't already know about dust?
posted by DU at 5:41 AM on May 16, 2007


Note to SCDB and delmoi.

Okay, in your note you wrote:
Yes, it is wholly mysterious. Look ... Ninety-six percent of the universe is made of something that has mass (gravitational attraction), yet it is NOT MADE OF ATOMS.
Non-atomic mass may seem mysterious to you, but it does not see mysterious to me, as we have known about non-atomic mass for a long time. I don't exactly see why "NOT MADE OF ATOMS!!!!1112" is so shocking.
posted by delmoi at 8:11 AM on May 16, 2007


There's a bit of clarification that needs to come in there. Lets think about things we've picked up in laboratory experiments that have mass that aren't atoms or parts of atoms:
* a bunch of subatomic particles that aren't part of atoms but that don't live long
* neutrinos

The ones that don't live long don't live long, and the neutrinos just won't sit in one place long enough for a galaxy to form around them.

Something else, something mysterious because we've not seen it in the laboratory, is the dark matter in question here.

On the other hand I wouldn't call the suggestion that there's a new form of matter out there 'shocking' even if said matter is 'mysterious', so I can sympathise with delmoi on that front, and as he also says in his first comment it doesn't seem to me that it should be terribly controversial
posted by edd at 9:06 AM on May 16, 2007


Alternate theories of gravity are unpopular, sure, but this article about conclusive proof of Dark Matter is all hype. Let's also not forget the need to account for Dark Energy, too.

The largest caveat in the article is "Although astronomers don't know what dark matter is made of, they hypothesize that it is a type of elementary particle that pervades the universe." Without a viable candidate, it's still completely ad hoc. You might as well call it God-matter. (too belligerent?)

Usually when a theory is inadequate to describe the known observations, it gets replaced by a more complete theory with even more explanatory power than was previously available. This professor has recently piqued my interests concerning theories of conformal gravity (to handle both the rotation dynamics of galaxies and the expansion of the universe), which also ties in nicely with M-theory (string theoretic).

For some reason, "Einstein-love?", people don't want to leave themselves open to a more complete theory of gravity. There's no reason not to treat M-theory and Alternate Theories of Gravity as equally likely as Unknown Elementary Particles.

That's where the Large Hadron Collider will come in. (Main Goals) The burden of proof rests on the shoulders of both cosmologists and particle physicists. IMHO, the jury is still out!
posted by quanta and qualia at 1:04 PM on May 16, 2007


'The largest caveat in the article is "Although astronomers don't know what dark matter is made of, they hypothesize that it is a type of elementary particle that pervades the universe." Without a viable candidate, it's still completely ad hoc. You might as well call it God-matter. (too belligerent?)'

With all due respect, that's just daft. Dark matter's called dark matter because it doesn't have much, if anything, to do with light. So it's dark. This is a useful distinction. The same doesn't apply to the label 'God-matter' which you have seemingly come up with just because it's bound to kick up a fuss.

'they hypothesize that it is a type of elementary particle that pervades the universe'
Yes, because if it's not an elementary particle then what the heck is it supposed to be? It can't be non-elementary because all the known elementary particles are ruled out! And it has to pervade the universe because whichever direction we want to look in we see evidence for it.

'Usually when a theory is inadequate to describe the known observations, it gets replaced by a more complete theory with even more explanatory power'
Feel free to come up with one. I do not know a cosmologist or particle physicist who wouldn't be ecstatic if you did. Unfortunately noone has, and dark matter remains, I think, the best bet.

'For some reason, "Einstein-love?", people don't want to leave themselves open to a more complete theory of gravity. There's no reason not to treat M-theory and Alternate Theories of Gravity as equally likely as Unknown Elementary Particles.'
I think alternate gravities get plenty of look in. That said, there isn't, unfortunately for those who think physicists are foolishly proposing phlogistons without good reason, a particularly strong candidate right now.

I will agree that the jury is still out though.
posted by edd at 4:00 PM on May 16, 2007


'they hypothesize that it is a type of elementary particle that pervades the universe'
Yes, because if it's not an elementary particle then what the heck is it supposed to be? It can't be non-elementary because all the known elementary particles are ruled out! And it has to pervade the universe because whichever direction we want to look in we see evidence for it. -edd


In my defense, if it's not an elementary particle and it doesn't interact with electromagnetic radiation or matter via any means other than to distort the gravitational space-time, then it seems to be a tool of design and hence on an article of faith I declare it must be God-matter. Please note the strong snear of sarcasm. :-) No insult intended.

There's no confirmed evidence of dark-matter (of the unusual Einsteinian General Relativity saving kind). Now, we can propose NEW AD HOC unusual matter, or we can propose a NEW MORE COMPLETE theory of gravity. I lean towards the more complete theory of gravity, which would include quantum gravity, over an enormous amount of ONLY GRAVITATIONAL matter with the brief aside that we still need the mechanism for cosmic expansion. So, my hyperbolic coinage of God-matter merely reflects my own distrust of faith-based categorization of phenomena. We need testable hypothesis, not convenient fits to data. We need theories that make predictions, not theories that merely say "I can model our reality in this way so as to motivate our dark-matter hypothesis."

Make sense? I'm not offended if it doesn't, nor will I be when I have to admit I am wrong. Just for now, that's the way I see it.

P.S. Dark matter is ad hoc because it's invoked merely to explain what we've already seen. It has no more explanatory power than calling it God-matter. It's just that God-matter would not fit within our usual model of particles and fields. So, dark-matter is not as far a stretch as God-matter, but they are in the same vicinity until dark-matter develops some powers of prediction-- something that (my) God-matter will never do.

P.P.S. The proponents of dark-matter would say the universe is cool enough now to have such a symmetry breaking. There could be an abundance of matter that only interacts very very weakly to the extent that it only couples via the gravitational force. Sure, fine, what's your model, and what does it predict? What are the elementary particle candidates? That's all I'm saying.
posted by quanta and qualia at 8:36 AM on May 17, 2007


There's really not this idea that dark matter is definitely there and that modified gravities are definitely wrong. It's just wrong to suggest that astrophysicists are saying one is definitely right and one is definitely wrong - I'm not saying that's what you're saying, because it's not clear, but it's something that deserves clearing up.

'We need testable hypothesis, not convenient fits to data. We need theories that make predictions, not theories that merely say "I can model our reality in this way so as to motivate our dark-matter hypothesis."
There's very much an awareness that theories should be predictive. That dark matter is largely favoured doesn't mean it's somehow unpredictive (we've already ruled out many models of dark matter as I've said).

'Dark matter is ad hoc because it's invoked merely to explain what we've already seen.' - more than that, it explains multiple observations made through several methods. It's not chucked in randomly to patch things up willy nilly, consistency checks are made.

There could be an abundance of matter that only interacts very very weakly to the extent that it only couples via the gravitational force. Sure, fine, what's your model, and what does it predict? What are the elementary particle candidates? That's all I'm saying.
Axions, lightest supersymmetric particles.... all motivated from particle physics and not astrophysics, but which are CDM candidates? They don't even have to couple exclusively to gravitation (axions don't), just sufficiently weakly to other forces, like neutrinos.

It's an open question, everyone recognises that it's an open question, but most opinion is that dark matter is behind it. Claiming that a modification to gravity is less ad hoc than proposing particles that already have independent motivation is, I think, currently pretty unjustified.
posted by edd at 5:05 PM on May 17, 2007


Good discussion so far. :-) And, certainly does need clearing up. Last I heard about axions was troublesome, but as you say no need to rule it out completely. It really does depend on the supersymmetry models one buys into as potentially leading (okay maybe one doesn't need buy a suspersymmetry model at all, but i'm taking that risk now) to the solution, and from the colloquia (admittedly much well above my comfort level) didn't seem more than conjecture, although potentially testable. The better colloquia I've attended have suggested particle physics theory that fits nicely with conformal gravity. Granted some of that is attributable to the presenter, but this is my bias.

The God-matter hypothesis was a bit of a joke considering the number of "plausible" theories on dark matter and dark energy. Didn't mean to equate it to the sophistication of real honest QCD. Again, thank you for keeping me honest, too. This openness is certainly why LHC is so very exciting!
posted by quanta and qualia at 7:40 PM on May 17, 2007


« Older "When a marriage dies, what should be done with th...   |   Is it 2000 bucks worth of offe... Newer »


This thread has been archived and is closed to new comments