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China's PandaX Project Looks For Dark Matter In the Heart of a Marble Mountain

timothy posted about 6 months ago | from the In-hollow-halls-beneath-the-fells dept.

China 62

the_newsbeagle writes "Chinese engineers love their superlatives: Biggest dam, fastest train, etc etc. Now they've constructed the deepest underground dark matter detector beneath a mountain in Sichuan province. Such dark matter seekers have to be buried deep to shield them from cosmic rays, because that radiation would be picked up by the detector and could be confused for radiation generated by dark matter. Other dark matter detectors are similarly subterranean: LUX, in the United States, is at the bottom of an abandoned mine in South Dakota, and a European effort called XENON lies below the Gran Sasso mountain. The Chinese researchers hope their PandaX detector will finally reveal the much-hypothesized, never-seen dark matter particles known as WIMPs."

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XENON is US-led (4, Informative)

Xerxes314 (585536) | about 6 months ago | (#46126261)

Actually, XENON isn't a European project, it's an international collaboration with leadership in the United States and members in Europe and China. The device is in Europe, but that's sort of incidental. Here's the membership: XENON-100 [columbia.edu]

Re:XENON is US-led (0)

Anonymous Coward | about 6 months ago | (#46134329)

I saw 'PandaX' and thought, "man, that is the lamest X-Men spinoff title Marvel has come up with in a long time."

Re:XENON is US-led (1)

Absolutely.Geek (2913529) | about 6 months ago | (#46138165)

Where as I saw it and thought it was Kung-Fu Panda 10...

Dark Matter is only a filler (1)

evanh (627108) | about 6 months ago | (#46126263)

I predict (On nothing more than an opinion) it won't be found because the current models have simply not accounted for enough normal matter. We're only talking one decimal place, right?

Re:Dark Matter is only a filler (4, Informative)

femtobyte (710429) | about 6 months ago | (#46126337)

We're talking about that one decimal place before the decimal point: current observations indicate more than five times as much dark matter as known matter. It's not just a little bit of round-off error in how much dust there is between stars, but apparently most of the stuff in the universe (at least, before you get to "dark energy," which is "twice as big" again, but far more poorly understood).

That's 1 digit (2)

evanh (627108) | about 6 months ago | (#46126385)

Ah, so less than one decimal place then. Even closer than I thought.

Re:That's 1 digit (1)

Anonymous Coward | about 6 months ago | (#46126521)

The gap is large than that, as the 5:1 ratio given there is from things like the CMB, and not direct observation of matter. Direct observation of matter only finds about a quarter or less of the matter that the such a model predicts, so saying there is 5 times as much dark matter as matter already assumes there is a huge chunk of normal matter we haven't yet seen. No one is assuming we are omniscient and have seen all there is to be seen, although there are some quantitative upper bounds on specific kinds of visible matter in narrow contexts (e.g. microlensing searches).

Re:Dark Matter is only a filler (1)

Wycliffe (116160) | about 6 months ago | (#46126587)

Given the vast distance between stars, saying that most of the matter in the universe is dust between stars seems reasonable to me.
Isn't that like saying there is more dust floating in the air than there is in concentrated dust bunnies in your house?
Another example would be saying there is alot more water vapor in the air that what you see concentrated in the clouds.
I didn't do the calculation but it doesn't seem unreasonable to me to think there is more matter between us and the neared star than
there is concentrated in our sun's mass even at the extremely low densities of space which according to google is about 1 atom per
centimeter. Why do we need to introduce dark matter to get the math to work out?

Re:Dark Matter is only a filler (3, Informative)

femtobyte (710429) | about 6 months ago | (#46126621)

We can make estimates of the amount of dust out there based on the light we see from distant stars. Where there is dust, it will scatter light passing through it (and modify the spectrum). There are lots of open questions about how much and what kind of dust is out there --- this isn't a "solved" problem --- however, best estimates plus known uncertainties don't put this within range of explaining dark matter. So, we still need dark matter to "make the math work out."

Re:Dark Matter is only a filler (1)

AthanasiusKircher (1333179) | about 6 months ago | (#46126651)

Given the vast distance between stars, saying that most of the matter in the universe is dust between stars seems reasonable to me.

If there were that much dust, there would be a LOT more light scattering from stars and other effects.

Why do we need to introduce dark matter to get the math to work out?

It's not just like we have some random idea that there's a large amount of mass out there. The gravitational effects suggest it is concentrated in certain areas, certain parts of galaxies, etc. If the matter were simply dust or something concentrated enough according to those gravitational patterns observed, it would have major observable effects.

Beyond this, there are all sorts of more technical reasons why dark matter is unlikely to just be normal matter -- like all normal matter emits radiation, and we'd be able to detect it in background radiation patterns if there were that much out there. And also if all the dark matter were baryonic (e.g. MACHOs), it were seriously disagree with the observed distribution of elements in the universe. It would require the whole theory of the Big Bang (with its many self-consistent predictions) to be seriously flawed.

Re:Dark Matter is only a filler (0)

the_Bionic_lemming (446569) | about 6 months ago | (#46126671)

Why do we need to introduce dark matter to get the math to work out?

So someone that has a theory can make money pursuing it?

Re:Dark Matter is only a filler (2)

TapeCutter (624760) | about 6 months ago | (#46127481)

To explain the rotational speed of galaxies.

Re:Dark Matter is only a filler (2)

Baloroth (2370816) | about 6 months ago | (#46126761)

Because of Big Bang nucleosynthesis [wikipedia.org] . Long story short, we can look at how the universe formed from evidence left behind in the cosmic microwave background radiation, and see that it is impossible for normal baryonic matter to explain dark matter. That, and the Bullet Cluster [wikipedia.org] makes little sense without dark matter.

Re:Dark Matter is only a filler (3, Informative)

Maritz (1829006) | about 6 months ago | (#46126389)

Sounds like what you're talking about are compact halo objects [wikipedia.org] , e.g. brown dwarfs, black holes, etc. The broad consensus is that there is nowhere near enough of this material to explain the high velocity of stars in the outer parts of the galactic disk/s. Also we have observations such as the bullet cluster [wikipedia.org] which are very difficult to explain without proposing invisible gravitating material.

Having said that, you might be right, maybe we'll find out.

Re:Dark Matter is only a filler (1)

Immerman (2627577) | about 6 months ago | (#46126857)

So perhaps you can explain this to me: The bullet cluster is special because the observed gravitational lensing has largely broken free from the observed luminous matter, continuing on as though the collision had not occurred. But why would dark matter behave like that? As I understand it, in a galactic collision it is exceeding rare for more than trace amount of matter to actually impact each other, mostly it's all just gravitational interactions, and thus DM should be affected similarly. So why would it "pull free" from the collision? Without such an explanation it would seem to me to be a strong argument in favor of considering some of the alternative theories.

Re:Dark Matter is only a filler (0)

Anonymous Coward | about 6 months ago | (#46127051)

There seems to be a nice explanation [wikipedia.org] in the Wikipedia article about the cluster [wikipedia.org] :

The hot gas of the two colliding components, seen in X-rays, represents most of the mass of the ordinary (baryonic) matter in the cluster pair. The gases interact electromagnetically, causing the gases of both clusters to slow much more than the stars....

Note that they are actually saying exactly what you said; the stars have continued straight on; the gas, which is most of the visible mass, stopped. The real question is: why did the gravitational lensing follow the stars and not the gas?

Re:Dark Matter is only a filler (1)

Immerman (2627577) | about 6 months ago | (#46134629)

Concise and informative. Thank you.

Re:Dark Matter is only a filler (1)

femtobyte (710429) | about 5 months ago | (#46128575)

The reason that the dark matter separates is the same reason that it follows a different distribution from visible matter in other galaxies (a diffuse blob instead of a galactic plane): whatever the stuff is, it's very weakly interacting with everything else (including other dark matter). Normal matter experiences "drag" as you push one cloud of it through another --- from the particles interacting and bouncing off of each other (or, at least, more gently being pushed by electromagnetic radiation from other particles). These interactions, as particles clump and stick and drag, are what allow a galaxy to collapse into a flat disc (instead of a big, amorphous gas cloud). But Dark Matter hardly feels this "drag" at all --- it's extremely "slippery," so two clouds will pass through each other virtually undisturbed. The lack of interactions also makes it really hard (impossible, so far) to catch DM in the lab.

Re:Dark Matter is only a filler (1)

Maritz (1829006) | about 5 months ago | (#46129511)

In very broad brush strokes, the impression I get is that normal matter is 'sticky' in that it interacts with photons. Things get ionized, they clump up. Because dark matter is taken to not interact at all with photons or electromagnetic fields in general it tends to just pass right through. If you're talking about a diffuse material that *only* interacts gravitationally then what you'd expect is for it to crash on through while the baryonic gas gets waylaid by intervening material.

This is just my impression and I'm not an expert so I could be off.

Superlatives (0, Insightful)

Anonymous Coward | about 6 months ago | (#46126279)

Yeah, those Chinese engineers.

Like Superbowl.

Hah!

Re:Superlatives (-1)

Anonymous Coward | about 6 months ago | (#46126323)

Chinkiest armor.

Chinese Mountain, Italian Mountain... (1)

mbone (558574) | about 6 months ago | (#46126365)

We just had this last Friday, except that was for the search for WIMPs in an Italian mountain [slashdot.org] . Not much changed in the search for WIMPs in the last week.

Re:Chinese Mountain, Italian Mountain... (3, Insightful)

femtobyte (710429) | about 6 months ago | (#46126445)

We just had a story about "people doing something on a computer" last week. Not much has changed about the existence of computers since last week. No need to post articles bothering with the trivial details between one computer system and another --- it's all the same, once you've seen one. Only alert me when something new happens in the world.

Re:Chinese Mountain, Italian Mountain... (1)

mbone (558574) | about 6 months ago | (#46127013)

Yeah, the story editing on slashdot has always been poor. I just care more about the physics articles.

THIS IS A TITLE I HOPE YOU ARE HAPPY WITH IT (0)

Anonymous Coward | about 5 months ago | (#46128525)

He was mocking you.

Here at the end of the American era (2)

musmax (1029830) | about 6 months ago | (#46126419)

I can't help to feel a bit of both schadenfreude and melancholy. Being a westerner myself, I wonder if Neil Stephenson were more of a prophet than a futurist.

Re:Here at the end of the American era (0)

Anonymous Coward | about 6 months ago | (#46126463)

Well, maybe the Western efforts will beat the Chinese to discovery in this field --- what with having a higher density of WIMPs around their labs.

I will gladly pay you Tuesday (0)

Anonymous Coward | about 6 months ago | (#46126449)

for some Dark Matter today

Re:I will gladly pay you Tuesday (0)

Anonymous Coward | about 6 months ago | (#46126485)

OK; I just sent a bunch of dark matter your way. Catching it is your problem. I hope you've got the check in the mail, or the next particle beam I send in your direction won't be so weakly interacting.

WIMPs (4, Informative)

loosescrews (1916996) | about 6 months ago | (#46126487)

In case anyone was wondering, WIMPs are Weakly Interacting Massive Particles [wikipedia.org] .

Re: WIMPs (0)

Anonymous Coward | about 6 months ago | (#46126695)

Really? I thought they were looking for the kids who got beaten up and had their lunch money stolen every day

Re: WIMPs (0)

Anonymous Coward | about 6 months ago | (#46126759)

No, the eventual end-products of those are much easier to find in a lab, and have been known for centuries --- they're called "scientists."

Re:WIMPs (0)

Anonymous Coward | about 6 months ago | (#46127271)

Only on Slashdot would nerds need informing of what a WIMP is.

Re: WIMPs (0)

Anonymous Coward | about 6 months ago | (#46127607)

Not all nerds are astrophysicists. I for one am thankful for the clarification.

If this was a journalism site is complain about the bad journalism of not defining one's acronym. But alas, this is a crowdsourced press release site.

Re: WIMPs (0)

Anonymous Coward | about 6 months ago | (#46127593)

Oh so that's it. I thought they were after a system that has Windows, Icons, Menus and a Pointing device but no GUI.

Foam/warpage (0)

Anonymous Coward | about 6 months ago | (#46126491)

It seems likely that DM is akin to foam or a positive warpage of regions of spacetime. Such positive warpage of spacetime would appear to increase the gravitation of subsumed/circumscribed regions in the same way that negative warpage/depression normally results in gravitation.

As to the exact mechanism that would give rise to such positive warpage, one might speculate that matter-antimatter collisions are not nullifications as is normally assumed, but produce some sort of quasi-particles that are retained in spacetime and may give rise to baryonic matter in minute quantities. Most of it will never recombine into baryons, at least not for some time, and will be retained, causing the positive curvature.

Indeed, this foam may be responsible for the existence of normal matter altogether, as it may have protected the matter from collisions during/after the BB. The extra antimatter was able to collide with enough recombined matter from the froth to cancel itself out leaving our matter behind.

Re:Foam/warpage (0)

Anonymous Coward | about 6 months ago | (#46126511)

one might speculate that matter-antimatter collisions are not nullifications as is normally assumed, but produce some sort of quasi-particles that are retained in spacetime and may give rise to baryonic matter in minute quantities

If only we had large machines that monitored the production products of matter-antimatter reactions in detail millions of times a second.

Re:Foam/warpage (1)

Okian Warrior (537106) | about 6 months ago | (#46126539)

If only we had large machines that monitored the production products of matter-antimatter reactions in detail millions of times a second.

In order to test the OP's conjecture, you have to actually look for effects he is talking about. None of the big-iron systems have been looking for this effect.

Do you have a paper or citation link? I'd be very interested in any study that looked for effects due to the non-homogenoius distribution of dark matter.

Re:Foam/warpage (2)

femtobyte (710429) | about 6 months ago | (#46126603)

What collider experiments do look for is "missing mass" --- if the amount of stuff coming out doesn't add up to the stuff going in, minus known detector inefficiencies (indicating some new "invisible" particle being produced). So, people are looking for dark matter production --- anything that results in mass/energy being converted to unknown/undetectable forms --- in a systematic manner. You may not specifically be looking for "spacetime foam," but anything that doesn't mimic "ordinary" particles in firing detectors (thus would already be visible in existing DM searches) in sufficient quantities will be found.

Re:Foam/warpage (0)

Anonymous Coward | about 6 months ago | (#46126613)

Look into some of the matter-antimatter asymmetry work, unless the OP is suggesting energy is not conserved, in which case their might be bigger questions related to the loss of time translation symmetry via Noether's theorem. It kind of helps to have some sort of quantitative prediction in stead of some vauge words leaving people to guess what might actually be seen or not seen, or what to look for in terms of per-existing research.

Re:Foam/warpage (1)

femtobyte (710429) | about 6 months ago | (#46126527)

Who assumes matter-antimatter collisions are "nullfiications"? They don't produce "nothing," but spit out particles with the "combined" properties of the inputs --- i.e, back-to-back photons carrying the energy and momentum of the initial particle/anti-particle pair. Also, if DM is some localized warpage in space-time, why does it appear gravitationally bound to visible masses (i.e. accumulating in galactic halos)? Space-time wiggles (like gravity waves) don't behave that way in known theories. unless you're just stringing together random words with no meaning to sound smart.

A Marble mountain? A mountain made of marble? (2)

Almost-Retired (637760) | about 6 months ago | (#46126537)

A marble mountain? Here I've been under that impression that both granite and marble had a detectable amount of radioactivity of their own, so even given 20 miles of the stuff, there would still be a background count contaminating the data.. Can someone fact check me on that?

Cheers, Gene

Re:A Marble mountain? A mountain made of marble? (1)

Anonymous Coward | about 6 months ago | (#46126705)

The biggest worry for a dark matter experiment is neutrons. Alpha radiation and beta radiation are charged particles, and are stopped by a modest amount of material because the electromagnetic force is strong. Gamma radiation is photons, but because there are so many charged nuclei and electrons in matter, a gamma ray will eventually interact in enough shielding. Typically that's something like a a meter of lead. But neutrons aren't charged, so they don't experience the electromagnetic force, and so they can pass through shielding more easily.

What's worse is neutrons look similar to the signal they're looking for. A WIMP will recoil off a nucleus in the detector, leaving behind some energy. Charged particles are more likely to recoil off he electrons in the atoms. But neutrons also recoil off of nuclei, and so a lot of neutron radiation would make it difficult to pick out a WIMP signal.

The radiation from uranium, thorium, and potassium in the rock is mostly alpha, beta, and gamma radiation, and so they can shield it. But one of the biggest sources of neutron radiation is cosmic rays. A cosmic ray muon (which is like a heavy, unstable version of the electron) is heavy enough that it can knock neutrons loose from their nuclei. Muons are at almost a perfect charge to mass ratio that they can pass through matter without losing too much energy. It takes several thousand meters of water to shield from all the muons being created in the upper atmosphere. At the earth's surface, there's about one muon per square centimeter per second. Deep enough underground, you can cut that to one per square meter per day or better. That's something like a billion-found reduction in muons, which also means a large reduction in neutrons.

Re:A Marble mountain? A mountain made of marble? (3, Informative)

femtobyte (710429) | about 6 months ago | (#46126715)

Just about every kind of rock has background radiation of its own, which must be dealt with (some more than others). However, radiation from rocks is typically easier to deal with than cosmic rays from space --- it's lower energy stuff that can be blocked by a few extra layers of extra lead/copper shielding (carefully screened for even lower radioactivity), instead of energetic particles that go through hundreds of meters of material unhindered. You have to worry about things like radon (radioactive gas) seeping out of the rocks and getting into the equipment; but, these are known effects to watch out for deal with by proper ventilation/sealing.

Re:A Marble mountain? A mountain made of marble? (3, Interesting)

Almost-Retired (637760) | about 6 months ago | (#46128281)

I know that the detector tank in the bottom of Homestake is lead shielded, but that lead is very old, no newly mined lead in it. It had to be at least 100 years old to even be considered for recycling into that shielding. I used to live in Rapid City in the '60's, even have a wife I still miss buried there, but in those years, Homestake, 50 miles away in Lead, SD was an actively producing gold mine. And environmental disaster as it struggled to remain profitable, it eventually had to close, and I am glad that another use has been found for its extended underground.

The Lead/Deadwood area tried to survive on tourists, but I imagine much of that allure has faded after the state raided and closed the Pink Lady in the '70's, the countries oldest continuously operated whorehouse. The girls were clean, checked daily to keep them that way, and they contributed 5 to 7 million a year to the local charities. When they had the liquidation sale, somebody wanting a piece of history had to bid $50,000 just to get the front door. End of an era as it had been there, a fully functioning, locally respected member of the community for over 140 years. I felt a little sad at the passing of a legend.

Cheers, Gene

Re:A Marble mountain? A mountain made of marble? (1)

Baloroth (2370816) | about 6 months ago | (#46126775)

Generally speaking, the deeper the mine is the less likely it is to have to deal with cosmogenically activated radiation sources or direct cosmic radiation. Same reason that these kinds of experiments often use "ancient lead" [aspera-eu.org] that has been buried under the seas for thousands of years: the deeper you go. Stuff that has been underground for thousands or millions of years is vastly less likely to have been made radiative from the sun or other cosmic sources.

Re:A Marble mountain? A mountain made of marble? (2)

femtobyte (710429) | about 6 months ago | (#46126799)

Same reason that these kinds of experiments often use "ancient lead" [aspera-eu.org] that has been buried under the seas for thousands of years: Stuff that has been underground for thousands or millions of years is vastly less likely to have been made radiative from the sun or other cosmic sources.

Newly-mined lead is not radioactive due to the sun or cosmogenic sources, but because of isotopes of lead which are produced from decays of uranium and thorium (which already existed from the supernova remnants that formed our current solar system) --- see here [wikipedia.org] . So, you don't want lead that you've just mined from millions of years deep underground --- that stuff is still pretty hot. What you want is stuff that was mined by the Romans two millenia ago, separated from the underground crud full of uranium/thorium, and left to cool off since then.

Re:A Marble mountain? A mountain made of marble? (2)

Almost-Retired (637760) | about 6 months ago | (#46128297)

That's a far better explanation than mine, thanks. My wet ram, at nearly 80, doesn't always recall the scale of the age, just that it was old and they paid a high premium for it because it was old & well "cooled".

Cheers, Gene

Smart aleck's answer..... (1)

rts008 (812749) | about 6 months ago | (#46126825)

Go ahead and see how well you do making a mountain of marbles.
(hint: explore "angle of repose")

On a serious note, that radiation is fairly well known, and can be filtered out I assume.(I could be wrong)

Also, I am assuming that cosmic radiation may have different characteristics than underground(known?) radiation.
At least that is what I gathered from TFA.

Disclaimer: While astrophysics is a hobby interest, I am by no means an astrophysicist. If this comment lowers your IQ, I apologize. :-)

superlatives (2)

dwater (72834) | about 6 months ago | (#46126579)

> Chinese engineers love their superlatives

I wonder where they learned *that* from?

Re:superlatives (0)

Anonymous Coward | about 6 months ago | (#46126657)

3D PRINTING OF HUMAN ORGANS MEANS STAR TREK REPLICATORS ON MARS!!!! Certainly not from us! We're very reasonable and healthily skeptical.

Best foot forward... (0)

Anonymous Coward | about 6 months ago | (#46126595)

[Never let anyone see the undersides of your family.] AKA "Put your best foot forward" A chinese philosophy that dooms them to fail. So goes the "Biggest dam, fastest train" myth. It's all shiny until it fails. Cracks in a newly built dam. High speed trains held together with duct-tape. I'm surprised they didn't use duct-tape to hold together their mission on the moon. Or did they?

Takeaway for most Westerners (1)

Dahamma (304068) | about 6 months ago | (#46126731)

Don't worry, there is clearly lots of marble left to be mined, your future countertops will continue to be as cheap as your disposable electronics.

Hurray... (2)

hughJ (1343331) | about 6 months ago | (#46126753)

...a cosmology news story so a bunch of Slashdot armchair physicists without a lick of physics education past high school can tell the science community they've been doing it wrong for the last 70 years.

Re:Hurray... (0)

Anonymous Coward | about 6 months ago | (#46127291)

Hurray, another bigoted and narrow-minded pseudo-scientist who can't imagine that people outside academia actually have both the credentials and skills to analyze and talk about scientific matters.

After all, we all know that science works because it follows the model of the Catholic church, with a bunch of infallible experts at the top of the hierarchy!

Re:Hurray... (0)

Anonymous Coward | about 6 months ago | (#46128239)

As an actual scientist, while there are people outside of academia that have the ability to comment insightfully on various pure science research, they are almost never the ones posting on Slashdot, or many other websites. Too many things get posted that amount to a couple minutes of some armchair scientist's thoughts in isolation, like some ancient Greek philosopher who thinks understanding of the world can be deduced without looking at the world because poster didn't bother looking into the topic at all to see their idea contradicts already done experiments (sometimes experiments done in a intro level physics lab). Even if you potentially have the skills to talk about such things, it doesn't matter if you are too lazy to actually apply them and be self-motivated to find what is already out there at some basic level. Instead you end up with posters that get all indignant that you won't spend hours chasing down citations and calculations in response to their 5 minute post that lacks both, and end up with scientists deciding not to waste time trying to answer questions on the internet because of a noisy few.

Re:Hurray... (2)

hughJ (1343331) | about 6 months ago | (#46131557)

If people here were coming up with alternate theories that account for all the observations that we presently see that have continually point physicists to the conclusion that there's some substantial non-baryonic mystery component of the universe, then that would be fine. But most of the oh-so insightful wisdom being shed seems to come from people who haven't even bothered to brush up on the wikipedia articles on the topic.

While it's certainly unscientific to shut out alternate theories based solely on the 'authority' of whatever happens to be the prevailing theory of the period, that doesn't mean that repeating the same arguments rooted in absolute ignorance of the topic can be passed off as unclouded wisdom. You think physicists haven't considered that general relativity could be wrong for the last 100 years? Or that there's some deeply seated ideological tether to Einstein that keeps modern physicists from wanting to one-up him? Anyone who could come up with something that unseats general relativity would be a sure bet for a nobel prize, and put themselves in the history books.

Maybe the sort of posts I'm talking about are actually a vocal minority of repeat offenders, but it's still pretty depressing when the signal to noise ratio here about certain science topics is even worse than a place like Reddit. Probably because most of the people in less "nerdy" communities haven't had a childhood of praise of super intelligence for being able to program the family's VCR and power cycle the cable modem to fix the "broken" internet.

Re:Hurray... (0)

Anonymous Coward | about 6 months ago | (#46127293)

...and make a bunch of tired jokes than anyone familiar with the subject, i.e., nerds, will find lame.

Consider situations like these a litmus test for the makeup of those with mod points: You don't need a WIMP detector to clearly see the uninformed lamer signal in the sample.

Earth-swallowing black hole yet? (0)

Anonymous Coward | about 6 months ago | (#46127079)

Have the Chinese created the black hole that will swallow the Earth yet? What's taking them so long? Destroy the Earth already!

Looking in the wrong place (1)

outsider007 (115534) | about 6 months ago | (#46127195)

Everyone knows the best place to find dark matter is on Uranus

I know! (1)

cascadingstylesheet (140919) | about 6 months ago | (#46127411)

Hey, I know a dark subterranean place where you can find lots of WIMPS ...

This is probably and ignorant quesition... (0)

Anonymous Coward | about 6 months ago | (#46138311)

Why is there so much interest in searching for Dark Matter?

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