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Signs of Dark Matter From Minnesota Mine

Soulskill posted more than 2 years ago | from the revenge-of-the-wimps dept.

Science 158

thomst writes "Juan Collar, team leader of COGENT, an experimental effort to detect WIMPs (Weakly Interacting Massive Particles), recently presented a paper detailing 15 months of data collected via a pure germanium detector located deep in a Minnesota mine which seems to confirm similar results reported by a European effort called DAMA/LIBRA. The results are particularly intriguing, because they appear to show a seasonal variation in the density of WIMPs that accords with models which predict Earth should encounter more WIMPs in Summer (when its path around the Sun moves in the same direction as the Milky Way revolves) than in Winter (when it goes the opposite direction). The most interesting thing about the COGENT experiment is that the mass of the WIMP candidates it records is significantly less than most particle physicists had predicted, according to popular models. (Ron Cowen wrote an earlier article about COGENT last year that goes into a lot more detail about how COGENT works, what its team expects it to find, and why.)"

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158 comments

winter? summer? (3, Insightful)

conspirator57 (1123519) | more than 2 years ago | (#36047300)

some of us live in the southern hemisphere, you insensitive clods!

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36047444)

toughen up or move north.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36047630)

Instead, why not have the summary give the *month* when Earth's path around the Sun moves in the same/opposite direction as the Milky Way revolves?

Re:winter? summer? (1)

pspahn (1175617) | more than 2 years ago | (#36047760)

The month appears to be irrelevant. The season is what is relevant. If the guy means to do a summer-time study in Minnesota to show that summer is when something happens, nobody is going to care what season it is in NSW. Lose the ego.

Re:winter? summer? (1)

arkenian (1560563) | more than 2 years ago | (#36048326)

The month appears to be irrelevant. The season is what is relevant. If the guy means to do a summer-time study in Minnesota to show that summer is when something happens, nobody is going to care what season it is in NSW. Lose the ego.

Actually quite the opposite. It is based on where the planet is in its orbit, which is based on the month, not the notional season. Unless I entirely misunderstand TFS, if the experiment had been in NSW, it would've had to be held in winter.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36048420)

...and the troll wins!

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36048504)

The experiment was not in NSW.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36048618)

The month appears to be irrelevant. The season is what is relevant. If the guy means to do a summer-time study in Minnesota to show that summer is when something happens, nobody is going to care what season it is in NSW. Lose the ego.

God, you're a fucking moron. I guess you probably represent most of the demographic on this site now. What arkenian wrote mirrors my sentiment, but he's much nicer about it and isn't 100% confident in his response (probably to be nice to you). Lose the ego.

Re:winter? summer? (1)

John Hasler (414242) | more than 2 years ago | (#36047450)

And the experiment should be duplicated there.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36047472)

My geraniums are just blooming too.

Re:winter? summer? (1)

Anonymous Coward | more than 2 years ago | (#36047488)

It is being duplicated there: DM-Ice [fnal.gov]

Re:winter? summer? (1)

physburn (1095481) | more than 2 years ago | (#36047988)

Good link, but its just a proposal and a test at the ice cube cosmic ray experiment so far. But yes it should be duplicated there. That will take some time though, DAMA took 13 years to get a decent signal (8 sigma I believe). So by 2020, we'll have a confirmation, maybe. And even then we'll still not really know what dark matter is.

---

Dark Matter [feeddistiller.com] Feed @ Feed Distiller [feeddistiller.com]

ah the antipodes (1)

circletimessquare (444983) | more than 2 years ago | (#36047506)

i would be angry at the sleight as well, except for the fact that, as an antipodean, you would instead feel pleasure at being overlooked

and my apologies for not writing this upside down and backwards and inside out in meaning, as is antipodean custom

Re:ah the antipodes (1)

Canazza (1428553) | more than 2 years ago | (#36047932)

So. what? Australia is Bizzaro world?
Would that make the Digiridoo the Bizzaro-Electric Guitar?

no (4, Funny)

circletimessquare (444983) | more than 2 years ago | (#36047976)

australia is known for arnold schwarzenegger, amadeus mozart, sigmund freud, franz ferdinand, the house of hapsburg, and "the sound of music"

please get a geography education

Re:no (1)

GuruBuckaroo (833982) | more than 2 years ago | (#36048490)

In accordance with Pope's Law [rationalwiki.org], I can't tell if this should be laughed at or laughed with. My parody detector is completely fried in these crazy years.

Re:no (2)

circletimessquare (444983) | more than 2 years ago | (#36048678)

two things:

1. yes, i am joking

2. as someone who has laughed at what others said in seriousness, and someone who has been mortified at what some meant as a joke, i share and feel your pain. the internet is a wondrous and frightening window on half-communicated things

Re:winter? summer? (2)

rossdee (243626) | more than 2 years ago | (#36047650)

For those of you that live in the southern hemisphere and don't have such seasons, winter is when it is cold. In Minnesota it can cool down to below 240K

(Yes I am aware that Antarctica has winter, but nobody lives there apart from penguins)

Re:winter? summer? (1)

garcia (6573) | more than 2 years ago | (#36048324)

Actually 230K. But hey, what's another 10 degrees Kelvin when we're already at more than 40 below zero.

Re:winter? summer? (1)

Bengie (1121981) | more than 2 years ago | (#36048996)

Coldest I've seen living in Wisconsin is -62c/-80f/211k including wind-chill. Local news said exposed skin could develop frostbite in 10-15 seconds. WI is right next to MN, so similar temps, although MN tends to take the brunt of the weather that the Rockys sends our way.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36049840)

Wind chill doesn't count when reporting temperatures. Stick to air temp and worry about the wind chill only if you're bothering to go outside.

Re:winter? summer? (1)

Anonymous Coward | more than 2 years ago | (#36047736)

some of us live in the southern hemisphere, you insensitive clods!

Yes, but statistically speaking, not very many of us do, and since Slashdot is a USA-based site, and even the summary mentions that the researchers were in the Northern hemisphere (Minnesota and Europe) it's pretty easy to figure out what they mean, even for someone who lives in a topsy-turvy land where up is down and presumably left is right and you have to wear magnetic boots to avoid falling off the Earth.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36047862)

> Yes, but statistically speaking, not very many of us do, and since Slashdot is a USA-based site, and...

Yes, but statistically speaking, WHOOOOSH!

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36048600)

Looks like we've lost another one to magnetic boot failure.

Re:winter? summer? (0)

Anonymous Coward | more than 2 years ago | (#36048382)

Everyone knows the southern hemisphere orbits the sun in the opposite direction of the northern hemisphere. So, people in the southern hemisphere will still experience more dark matter in their summer.

Umm, Guys... (-1)

fuzzyfuzzyfungus (1223518) | more than 2 years ago | (#36047312)

I hate to rain on your journal article; but you may have just discovered some of the coal we accidentally left down there when we finished mining...

Re:Umm, Guys... (1)

Anonymous Coward | more than 2 years ago | (#36047378)

Ummm -- Minnesota is not a COAL mining mecca; the Sudan mine is located in what is known as the Iron Range.

Re:Umm, Guys... (0)

Anonymous Coward | more than 2 years ago | (#36047448)

Hence the old WCCO running joke of "The Iron Ranger", with his trusty horse Taconite... I miss those days. :)

Re:Umm, Guys... (0)

Anonymous Coward | more than 2 years ago | (#36047756)

Typo -- you forgot the O -- Soudan.

Re:Umm, Guys... (0)

Anonymous Coward | more than 2 years ago | (#36047492)

The mine is iron ore.

Pretty good iron ore actually. 60%+ iron. Stuff that a magnet will stick to.

But it was too deep to mine economically.

You can tour the mine if you want, it's in Tower/Soudan, up by Ely and close to the Boundary Waters Canoe Area (a few hours drive from Duluth, MN). There's a mine tour and a physics lab tour.

THEY STILL MINE ?? (-1)

Anonymous Coward | more than 2 years ago | (#36047316)

Whodathunk ?? This is 2011 already !!

Population growth = more raw materials needed (1)

name_already_taken (540581) | more than 2 years ago | (#36047856)

Whodathunk ?? This is 2011 already !!

How do you think we get stuff? Magic? Recycling yields less that 100%, so as the population grows, we need to get more stuff out of the ground.

Science is good (4, Insightful)

Tsingi (870990) | more than 2 years ago | (#36047362)

Nice to see that we are still supporting science for the sake of science, not just science that turns into profits for some private corporation.

Re:Science is good (0)

Anonymous Coward | more than 2 years ago | (#36047404)

Just wait until they figure out how to charge you for dark matter.

Re:Science is good (1)

ArcherB (796902) | more than 2 years ago | (#36048330)

Just wait until they figure out how to charge you for dark matter.

Why? Nibbler will fling it at you for free.

Re:Science is good (1)

Coisiche (2000870) | more than 2 years ago | (#36047532)

Yeah, the stuff, despite these results, is still hypothetical but there's probably already sufficiently vague patents on it's commercial use. They'll proably get a cease and desist letter from a lawyer now. It's the way the world works.

Re:Science is good (1)

khallow (566160) | more than 2 years ago | (#36047990)

Unfortunately, information about the existence of dark matter is useful knowledge in improving our understanding of the universe and focusing the efforts of thousands of physicists and their support personnel. So it's not science for the sake of science.

Re:Science is good (1)

Anonymous Coward | more than 2 years ago | (#36048838)

Why do you use the word "unfortunately" and what is your point in response to Tsingi? You make a valid statement, but your post comes off as argumentative to the one you are replying to. I don't see what point you are trying to argue.

I think maybe you're just a dumbfuck. Or you're just disagreeing for the sake of disagreeing with his choice of words.

Re:Science is good (0)

khallow (566160) | more than 2 years ago | (#36049176)

Why do you use the word "unfortunately" and what is your point in response to Tsingi? You make a valid statement, but your post comes off as argumentative to the one you are replying to. I don't see what point you are trying to argue.

Let's look at two phrases from Tsingi's post:

science for the sake of science

and

profits for some private corporation

Why should I consider the former as somehow being "nicer" than the latter? As I see it, "science for the sake of science" is merely being unaccountable with Other Peoples' Money (OPM). There's no interest in the usefulness of the science. It's a comfortable myth for OPM-fueled researchers to embrace.

At least with science for the sake of profits for some private corporation, you are doing something useful (and usually doing it with your own money not OPM).

We also need to note that he presents a false dichotomy. Science can be pursued for reasons other than private profit or science for its own sake.

The "focusing the efforts of thousands of physicists and their support personnel" is a genuine economic value beyond any scientific consideration. Physicists, their staff, and their equipment aren't cheap. And it expands human knowledge in a useful and concrete way.

Re:Science is good (1)

thegreatemu (1457577) | more than 2 years ago | (#36049196)

knowledge in improving our understanding of the universe ... So it's not science for the sake of science.

Ummm, methinks you should look up the definition of science

Re:Science is good (1)

khallow (566160) | more than 2 years ago | (#36049406)

Ummm, methinks you should look up the definition of science

And why would that help? I already know the common definitions of science. But to indulge your wishes, I went ahead and looked. Didn't see any insights there. Science isn't understanding of the universe, it's an activity which can improve understanding of the universe or it can generate "knowledge" for which there is no and never will be practical application.

Exciting to see it get sorted out (2)

pavon (30274) | more than 2 years ago | (#36048536)

This is especially interesting to me because another experiment failed to detect any evidence of dark matter [nature.com], which seemed to contradict the (not quite statistically significant) hints that CDMS may have detected dark matter last year.

I'm also confused about which experiment this is. It says it is in the Soudan mine in Minnesota, but it isn't mentioned on either [umn.edu] of the websites [umn.edu] for the mine. Is it part of MINOS or CDMS, or is it something separate?

Regardless, I have been really excited about these detectors for the last couple years (even more so than the LHC), and it is great to start seeing data.

Wait.... (1)

Anonymous Coward | more than 2 years ago | (#36047410)

Why are the nerds trying to detect the wimps?

Re:Wait.... (0)

Anonymous Coward | more than 2 years ago | (#36047938)

We have found the wimps, and we are they.

that always bothered me (2)

circletimessquare (444983) | more than 2 years ago | (#36047578)

http://en.wikipedia.org/wiki/Milky_Way [wikipedia.org]

"The Sun orbits around the center of the galaxy in a galactic year—once every 225-250 million Earth years."

has there ever been any research into odd or bad events in our geological record that occur with 237 million year frequency?

because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting? everything from asteroids to comets to various kinds of background radiation to fundamental particles could potentially vary periodically, according to this 237 million year loop

yes, i take solace that most stuff around us is orbiting right along with us

but not all of it

Re:that always bothered me (1)

Anonymous Coward | more than 2 years ago | (#36047678)

Just google "what happened 250 Million years ago" from Science Daily Nov 28, 2006 - http://www.sciencedaily.com/releases/2006/11/061126121112.htm [sciencedaily.com] The earth experienced its biggest mass extinction about 250 million years ago, an event that wiped out an estimated 95% of marine species and 70% of land species. New research shows that this mass extinction did more than eliminate species: it fundamentally changed the basic ecology of the world's oceans.

Re:that always bothered me (0)

Anonymous Coward | more than 2 years ago | (#36047828)

The heliosphere should keep most stuff out.

Even if there's some sort of rogue planet/mega asteroid belt out there the scales are so massive it's bafflingly unlikely that anything would come into the solar system let alone do anything.

But there is always the chance.

I'd be more worried about your every day comets/asteroids smashing into the Earth.

Re:that always bothered me (4, Informative)

Framboise (521772) | more than 2 years ago | (#36047972)

Note that the solar system co-rotates with the Milky Way matter around it, so the 225-250 Myr period with respect to an inertial frame is not relevant for dramatic effects. The sometimes discussed effect linked with massive extinction is the periodic crossing of the Milky Way plane, which occurs about every 35 Myr. The last great extinction ocurred 65 Myr ago, so one should have seen at least one or two of these plane crossing.

Another possibility is the solar system crossing spiral arms, with period of order of 150 Myr, but this is debated.

 

Re:that always bothered me (0)

Anonymous Coward | more than 2 years ago | (#36048396)

Note that the solar system co-rotates with the Milky Way matter around it,

But not, as this experiment shows, with respect to the dark matter.

Re:that always bothered me (1)

FatLittleMonkey (1341387) | more than 2 years ago | (#36048042)

The Permian-Triassic Extinction [wikipedia.org], "the Earth's most severe extinction event", occurred ~250Mya.

However, you have to ask what danger could be fixed in space, relative to the Milky Way's position relative to the position of background galaxies. Everything is moving relative to everything else, why would a line between the centre of our galaxy and an arbitrary deep space object be a permanent danger?

Re:that always bothered me (2)

kasperd (592156) | more than 2 years ago | (#36048050)

right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting?

There couldn't possibly be anything static lurking around in that part of space, the gravity would pull it towards the centre of the galaxy. so, whatever was there would have to be moving around the galaxy at the same pace. It is of course not entirely impossible that there are objects in a non-circular orbit, but if there was we wouldn't be meeting it at the same spot every time, and I could imagine that the trajectory of such an object would be quite irregular due to the gravity of other objects it would meet on its way.

Re:that always bothered me (1)

Dcnjoe60 (682885) | more than 2 years ago | (#36048080)

http://en.wikipedia.org/wiki/Milky_Way [wikipedia.org]

"The Sun orbits around the center of the galaxy in a galactic year—once every 225-250 million Earth years."

has there ever been any research into odd or bad events in our geological record that occur with 237 million year frequency?

because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting? everything from asteroids to comets to various kinds of background radiation to fundamental particles could potentially vary periodically, according to this 237 million year loop

yes, i take solace that most stuff around us is orbiting right along with us

but not all of it

It's not just the sun that orbits the center of the galaxy, but the entire solar system, including all of the rest of the solar systems. So assuming they are all rotating at the same rate in relationship to each other, then there isn't any new space to be plowing through.

Put differently, whatever was in the space we currently occupy 237 million years ago has also moved away and is occupying different space. Now if your concern is some rogue comet or something that passes through this spot every 237 million years and is not affected by the gravity of the other bodies in the galaxy, well that risk would be extremely small. The likelihood of a single object (or even multiple ones) in an orbit around the center of the galaxy but in a different plane that would intersect with our solar system at the same time every 237 million years, while not impossible, it certainly improbably.

Even a radiation burst from a distant star or pulsar aimed directly this way every 237 million years would require the distant object to be stationary compared to our solar system moving through it to be able to hit the same spot every 237 million years.

In short, it's not that our solar system is revolving around the center of the milky way galaxy every 237 million years, it is that the entire milky way galaxy is revolving around its center every 237 million.

yes, this is correct (1)

circletimessquare (444983) | more than 2 years ago | (#36048278)

my supposition is also absurd because the milky way itself is "moving" (orbitting?), in relation to other galaxies. there is no fixed point we are moving against

however, it is a slightly intriguing possibility, no? that say, some fundamental constant we take for granted as constant actually might vary slightly across a 250 million year period... for some reason. wouldn't that be interesting? yes, this is wild conjecture, but you could certainly sit around and construct a few "what ifs" that would suggest such a possibility. even though we aren't remotely able to ask serious science questions about such a hypothetical periodicity to... something, right now in our scientific maturity

at least the thought is the basis for some perhaps compelling speculative science fiction, if not real science

Re:yes, this is correct (0)

Anonymous Coward | more than 2 years ago | (#36048808)

however, it is a slightly intriguing possibility, no?

Not really.

Re:yes, this is correct (1)

cyberchondriac (456626) | more than 2 years ago | (#36049192)

Don't feel bad, it's occurred to me too.
Improbable, yes, quite, but not absolutely totally impossible- after all, there is much to the universe still not understood.. like dark matter. (Personally I blame anti-dark matter ;-D )
Seriously though, if there is something in the galaxy that caused the mass extinction, and it's location at any given time is randomized by the effects of gravity, it's not totally comforting to know we could still come across it at some point, and never even know when it's coming. Or if a totally separate but physically identical effect (gamma ray burst, for example) happens. OTOH, I think the odds are in our favor.

sayeth the great medieval poet, donald rumsfeld: (1)

circletimessquare (444983) | more than 2 years ago | (#36049284)

"There are known knowns; there are things we know we know.
We also know there are known unknowns; that is to say we know there are some things we do not know.
But there are also unknown unknowns – the ones we don't know we don't know."

Re:that always bothered me (1)

Bengie (1121981) | more than 2 years ago | (#36049810)

Being that the Earth is on the outer edge of the galaxy, I could see the Milky Way plowing into some intergalactic radiation and us getting pushed to the front of it could cause issues. Or anything else like that.

But more than likely, something that happened 237mil years ago was just a one time thing and just so happens to align with another number.

Re:that always bothered me (1)

ImprovOmega (744717) | more than 2 years ago | (#36048432)

because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years.

More accurately, we're plowing through space we've never plowed through before, in the context of the universe. The Milky Way is *also* moving through space at about 2.1 million km/hr or 600 km/s [astrosociety.org]. I suppose it all depends on your reference frame.

Signs of Dark Matter From Minnesota Mine (1)

Chrisq (894406) | more than 2 years ago | (#36047586)

Signs of Dark Matter From Minnesota Mine

Coal?

Re:Signs of Dark Matter From Minnesota Mine (1)

Black Parrot (19622) | more than 2 years ago | (#36049092)

Signs of Dark Matter From Minnesota Mine

Coal?

Yeah, that's why the call it "Coal Dark Matter".

The Soudan Mine can be toured (4, Interesting)

swb (14022) | more than 2 years ago | (#36047662)

The lab is located in a lower (the lowest?) level of the Soudan Mine. This mine is also a state park and you can tour the mine.

The tour (when I took it, about 9 years ago) took you down to the same level as the lab, which I think is the lowest level of the mine or within a level or two of the lowest level.

You ride a mine cart to a room where extraction of iron ore took place, hear some details about early mining, including a lights-out experience where they show you what it was like with nothing more than old-fashioned arc lamps on the miner's helmets.

Before you leave this level, you get to go into the lab area and get a look around. I don't think you go much past the entry way, but it's neat anyway.

The mine had a fire recently and I don't know if the tours are back in operation, but I believe they have every intention of continuing with them once they fix whatever happened.

Re:The Soudan Mine can be toured (4, Interesting)

unimacs (597299) | more than 2 years ago | (#36047942)

My family took the tour a couple of summers ago. Interesting history. They used to keep mules down there for months at a stretch. They were often in complete darkness. When brought back up to the surface they had to have their eyes covered until they were acclimated to light. The original miners used candles and the mining company made them pay for each one so they wouldn't be wasted (and to recoup some of the already paltry wages they were paying). If you are ever in that area it's definitely worth seeing, but frankly there's not too many reasons to visit that part of the state.

Re:The Soudan Mine can be toured (1)

hedwards (940851) | more than 2 years ago | (#36048004)

Charging for candles had nothing to do with wasting candles, it had to do with ensuring that the miners could never make enough to pay their debts. Same as it was for coal miners. Each pay check would dig them deeper in debt.

Re:The Soudan Mine can be toured (0)

Anonymous Coward | more than 2 years ago | (#36048380)

Not too many reasons, unless you enjoy the outdoors - then this area is your playground. Recently the Minnesota Department of Natural Resources purchased a large plot of land directly adjacent to the Soudan Mine - they now call this area Vermilion State Park. Some of the best fishing in the state, and in turn the world, is in this area. Most of this region is state or national forest land - an individual can hike for months on end and not be out of the wilderness. Personally, if I could find a sustainable income up there I would move in a heartbeat - unfortunately the trees don't need tech support :(

Re:The Soudan Mine can be toured (1)

plsenjy (2104800) | more than 2 years ago | (#36048724)

Not too many reasons, unless you enjoy the outdoors - then this area is your playground. Recently the Minnesota Department of Natural Resources purchased a large plot of land directly adjacent to the Soudan Mine - they now call this area Vermilion State Park. Some of the best fishing in the state, and in turn the world, is in this area. Most of this region is state or national forest land - an individual can hike for months on end and not be out of the wilderness. Personally, if I could find a sustainable income up there I would move in a heartbeat - unfortunately the trees don't need tech support :(

Yaaaawn. Another spot not worth visiting because the hotel doesn't have a decent T1 connection. Why would I visit a place if I can't boot up my computer and see the exact same online content that is available to me at home?

Re:The Soudan Mine can be toured (4, Interesting)

Zenaku (821866) | more than 2 years ago | (#36048592)

They charged the miners for candles, dynamite, and pretty much every other supply. See, (if I recall correctly from when I took the tour several years ago) the miners were not actually employees -- they were independent contractors. The company sold them supplies, let them into the mine, and then bought whatever ore they hauled out. This was mostly done to screw them. They could spend 18 hours a day hauling iron out of the mine for the company and yet not turn a profit.

Also, incidentally, my group also took a full tour of the lab while we were down there -- I think they are happy to give tours, they just aren't regularly scheduled. We had called a few days before and one of the grad students working there met us and showed us around. Sadly, I was not struck by any super-power-granting science beams.

Re:The Soudan Mine can be toured (0)

Anonymous Coward | more than 2 years ago | (#36048976)

I actually took a tour there with my highschool physics class from Harbor City International School down in duluth back in 2008.

The elevator ride down was perhaps the most intense moment of my entire life, it's pitch black and shakes the hell all over the place.

On one of the doors they actually have a sign from the old mining days labeled "No woman through this door". I snapped a picture of it with the student teacher lady standing next to it, it was perfect.

Get a life! (0)

Anonymous Coward | more than 2 years ago | (#36047666)

If the experiment is based in the Northern Hemisphere the reference can be assumed to be spring or Summer in the Northern Hemisphere.

Sounds like another feeble open source acronym (0)

Anonymous Coward | more than 2 years ago | (#36047708)

Giant Interacting Massive P ..... er, nevermind.

Did anyone else completely misinterpet the title? (1)

jpstanle (1604059) | more than 2 years ago | (#36047912)

When I first saw the title of the thread, my initial reaction was "How the hell is there dark matter in Minnesota? Did they find Nibbler's litter box or something?"

Re:Did anyone else completely misinterpet the titl (2)

Dcnjoe60 (682885) | more than 2 years ago | (#36048106)

Well, if it is a coal mine, wouldn't you expect it to be full of dark matter? ;)

The problem with seasonal variation... (5, Interesting)

Troggie87 (1579051) | more than 2 years ago | (#36047962)

I did my physics undergrad at the University of Minnesota Duluth, and they graciously let me play around in the mine on occasion. I don't do much particle physics anymore so I'm not particularily equipped to judge their results, but I can say that all kinds of seasonal errors can be introduced in these experiments. Cosmic rays have a seasonal variation for example. Another that happens at Soudan for sure and possibly in Italy is seasonal variation in background radiation. The air circulation at Soudan is largely passive, and there is lots of radon gas seeping from the rocks. In the cold winter the exchange is excellent, but in the summer the circulation is terrible and you get anywhere from 5 to 10 times the radon background in the cave (air in the cave is warmer than outside in the winter and cooler in the summer, you can do the math).

I'm not saying either of those are the cause of this, but there is good reason to squint hard at anything claiming "seasonal evidence" when the claim is extrordainary (in the sense that it is way off from any model). Scientists should be skeptical of this, especially since they are claiming a result before theory suggests a result should even be possible.

Re:The problem with seasonal variation... (0)

Anonymous Coward | more than 2 years ago | (#36049652)

It should be relatively straightforward to check for temperature-induced variations in the results: just dissasemble the equipment and reassemble it in a similar mine in the southern hemisphere. If what is being detected comes from outside of the earth you should still get the same effect independent of location, and it'll be higher during the cold season. Or reassemble somewhere near the equator, where there aren't any pronounced seasons.

The cosmic-ray angle is interesting, but according to TFA they planned for this already.

I wonder about the guided tours someone else mentioned already. Are these detectors so sensitive that a tourist with a wristwatch with (radioactive) glow in the dark needles would be detected? I bet the volume of tourists also has a seasonal variation.

(OT) Fortune generator (0)

arielCo (995647) | more than 2 years ago | (#36048166)

I'm also glad to see that /. is working on the fortune generator. Too bad it blurts all fortunes in ROT-13. Hint for the curious:

< uglymess.txt tr '[A-Za-z]' '[N-ZA-Mn-za-m]' | sed 's/%/\n\n/g' > clean.txt

Re:(OT) Fortune generator (1, Troll)

arielCo (995647) | more than 2 years ago | (#36048176)

Corrected:

< uglymess.txt tr '[A-Za-z]' '[N-ZA-Mn-za-m]' | sed 's/ % /\n\n/g' > clean.txt

Re:(OT) Fortune generator (0)

Anonymous Coward | more than 2 years ago | (#36050004)

I wondered what that was. I just had a glance and it all just seemed to be in Cthulu-speak.

So now the Dark Matter is... (0)

Anonymous Coward | more than 2 years ago | (#36048862)

really just becoming Emo Matter?

Not so clear cut (5, Interesting)

thegreatemu (1457577) | more than 2 years ago | (#36049304)

There's a huge controversy right now in the field. The DAMA/Libra experiment has been claiming an 8-sigma excess for years which they say is consistent with dark matter, but they keep getting excluded by other experiments, most notably CDMS and Xenon. Every time their favored region is excluded, they come up with a new way to reanalyze their data to make it consistent again. But they have not ever released any of their data to the community (and hold patents on the type of crystal they use for their detector) so it's impossible to directly verify.

CoGeNT first released hints of a low-energy excess which could be consistent with DAMA-type dark matter about a year ago. I was at the APS conference earlier this week where Collar released the seasonal modulation results which make it seem even more likely that they see the same thing as DAMA. However, just the next day, CDMS presented an analysis of their low energy data which is below their normal dark matter threshold (because the rate of background events in that region is quite high and poorly understood). They showed that, even if they didn't account for the known sources of background, the rate in their detector is inconsistent with CoGeNT's. As many people rightly point out, CoGeNT is seeing an exponential signal near threshold, which is what you'd expect to see in just about any detector with or without dark matter present.

The whole situation is muddled even further by politics and personalities. Collar is respected as a scientist, but is also generally agreed to be an asshole. When he announced the annular modulation result, he spent 25 minutes of his talk attacking xenon on mostly pointless grounds, then had only a single slide showing the important result of the modulation. He finds tiny holes in other's analyses, but doesn't often present a very convincing picture of his own.

tl;dr: The community is far from agreeing that what he and DAMA have seen are in fact WIMPs. CDMS and Xenon tend to have better established analysis programs and pay more attention to their systematics, and they still rule out both DAMA and CoGeNT. However, I think everyone at this point agrees they are seeing something interesting, just likely not WIMPs.

TV Show related to this (0)

Anonymous Coward | more than 2 years ago | (#36049346)

You can find out more about this in "Through the Wormhole with Morgan Freeman", this particular subject is in episode 8 (the last one)

Way, WAY off topic, but ... (0, Offtopic)

thomst (1640045) | more than 2 years ago | (#36049744)

On April 27, I posted this comment [slashdot.org] on another story about an entirely different topic. Eventually, it got modded to +3 Insightful. Then, this morning, I discovered it had been modded all the way down to -1 Overrated.

There's only one reason why a single moderator would spend that many mod points on down-modding a single post: to put it below the browsing threshold of virtually all /. readers. The question is, "Why?" And I suspect the only credible answer to that question is, "Because he is so consumed by dedication either to communism or to libertarianism (the two political philosophies whose fundamental assumptions I criticized in the post), that he feels compelled to suppress any criticism of it for which he is unable to muster an argument in response.

Now, because communists are so thin on the ground around here, I have my strong suspicions which philosophy my censor espouses - but it doesn't matter either way, because, in either case, this is clearly a case of someone systematically attempting to suppress dissenting speech. The act of suppression itself is one of craven philosophical cowardice, and it does nothing whatsoever to enhance the credibility of the political philosophy it purports to defend. To the contrary, it merely establishes that the moderator, at least, can muster no useful counter-argument. Instead, he substitutes moderation abuse for intelligent discourse.

In the interest of fairness, I urge you to read my comment [slashdot.org]. Whether or not the down-mod is undone, it deserves at least that much consideration.

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