SIOUX FALLS, S.D. — Scientists hoping to detect dark matter deep in a former South Dakota gold mine have taken the last major step before flipping the switch on their delicate experiment and say they may be ready to begin collecting data as early as February.

What's regarded as the world's most sensitive dark matter detector was lowered earlier this month into a 70,000-gallon water tank nearly a mile beneath the earth's surface, shrouding it in enough insulation to hopefully isolate dark matter from the cosmic radiation that makes it impossible to detect above ground.

And if all goes as planned, the data that begins flowing could answer age-old questions about the universe and its origins, scientists said Monday.

"We might well uncover something fantastic," said Harry Nelson, a professor of physics at University of California, Santa Barbara and a principal investigator on the Large Underground Xenon experiment. "One thing about our field is that it's kind of brutal in that we know it's expensive and we work hard to only do experiments that are really important."

This one hasn't been cheap, at about $10 million, but like the discovery of the Higgs boson – dubbed the "God particle" by some – earlier this year in Switzerland, the detection of dark matter would be a seismic occurrence in the scientific community.

Scientists know dark matter exists by its gravitational pull but, unlike regular matter and antimatter, it's so far been undetectable. Regular matter accounts for about 4 percent of the universe's mass, and dark matter makes up about 25 percent. The rest is dark energy, which is also a mystery.

The search in South Dakota began in 2003 after the Homestake Gold Mine in the Black Hills' Lead, S.D., shuttered for good. Scientists called dibs on the site, and in July, after years of fundraising and planning, the LUX detector moved into the Sanford Underground Research Facility, 4,850 feet below the earth's surface. It took two days to ease the phone booth-sized detector down the once-filthy shaft and walkways that originally opened for mining in 1876 during the Black Hills Gold Rush.

There, the device was further insulated from cosmic radiation by being submerged in water that's run through reverse osmosis filters to deionize and clean it.

"The construction phase is winding down, and now we're starting the commissioning phase, meaning we start to operate the systems underground," said Jeremy Mock, a graduate student at the University of California, Davis who has worked on the LUX experiment for five years.

Carefully submerging the delicate detector into its final home – a water-filled vat that's 20 feet tall and 25 feet in diameter – took more than two months, Mock said.

Scientists are currently working to finish the plumbing needed to keep the xenon as clean as possible. The xenon, in both liquid and gas form, will fill the detector and be continuously circulated through a purifier that works much like a dialysis machine, pulling the substance out to remove impurities before pushing it back into the detector.

Keeping the water and xenon pristine will help remove what Nelson called "fake sources" – or stuff that scientists have seen before, such as radiation, that could serve as false alarms in their efforts to detect dark matter.

Nelson likens the experiment to Sherlock Holmes' approach to discovering the unknown by eliminating the known.

Once the data start to flow, it'll take a month or two before the detector is sensitive enough to claim the "most-sensitive" title, Nelson said.

After that, the scientists involved hope to start seeing what they covet most: something they've never seen before.

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    In the late 18th century, King Gustavus III of Sweden was rumored to have carried out a strange experiment to determine the harmful health effects of coffee. Two identical twins who had been condemned to death had their sentences commuted to life in prison on the condition that one would drink three pots of coffee per day, and the other three pots of tea, for the rest of their lives. The only problem was that the doctors assigned to monitor the cases died before either of the patients did, their observations lost--as the story goes, the tea drinker died first, and there's no record of the coffee-drinker's death. The experiment proved nothing, suffering from a lack of rigor (to say the least). Source: Uppsala University, "Coffee - rat poison or miracle medicine?"

  • Simulated Anthrax On The Subway

    In June 1966, the U.S. Army's Special Operations Division secretly dispersed harmless bacteria in the New York Subway system to model the effects of an outbreak of more harmful germs. According to Army reports, "Test results show that a large portion of the working population of New York City would be exposed to disease if one or more pathogenic agents were disseminated covertly in several subway lines at a period of peak traffic." Source: Deadly Cultures: Biological Warfare Since 1945. Wheelis, Rózsa, and Dando. Harvard University Press, 2006.

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    Operation Big Itch, 1954, was an attempt to discover the potential of weaponized fleas. The operation, part of the Cold War-era United States biological weapons program, took place at Dugway Proving Ground in Utah. According to "Using the flea as weapon," an article in the Army Chemical Review, "In the United States, the plague flea concept was competing against the use of mosquitoes, flies, ticks, and lice. Of these concepts, the United States put most of its energies behind weaponizing yellow fever in combination with the Aedes aegypti mosquito."

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    U.S. Army Surgeon William Beaumont (above) found an extraordinary patient in Alexis St. Martin, a Canadian trapper who was injured in a hunting accident and left with a hole in his belly that led directly into his stomach. Beaumont attached a string to various foods, including oysters and rare roast beef, and introduced them into the wound to observe the rates of digestion. Despite the unorthodox techniques, this research would later lead to the discovery of the importance of stomach acid in digestion, earning Beaumont the epithet "father of gastric physiology." Source: Experiments and observations on the gastric juice, and the physiology of digestion. Beaumont, Martin and Combe. Maclachlan & Stewart, 1838

  • Candy For Mental Patients

    In 1945, Sweden's new National Dental Service commissioned research, now known as the Vipeholm experiments, in which researchers gave subjects large amounts of sticky sugary candy in order to study the development of cavities. This might not have been so controversial, except that the subjects couldn't give consent to their participation: "The use of mentally handicapped subjects was criticized in the Swedish press and all studies on mentally handicapped individuals were stopped in 1954," according to Topics In Dental Biochemistry by Mark Levine (Springer, 2010).