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ward with the Large Underground Xenon experiment -- or LUX -- the world's most sensitive dark-matter detector.
• For most people, dark matter is a term that made their eyes glaze over in science class. But for Gaitskell and scientists like him, it's the mystery meat of existence.
• "It makes up a huge amount of the universe," said Kevin Lesko, of Lawrence Berkley National Lab, who is the principal investigator for the Sanford Underground Research Facility.
• Problem is, scientists can't see it.
• "It has to be there because of its effects through gravity, but it also has to have properties that make it very unusual -- otherwise, we would have detected it already," Lesko said.
• Regular matter -- people and planets, for example -- make up about 4 percent

of the total mass-energy of the universe, he said. Dark matter makes up about 25 percent.
• "So it's five times as much as us, and yet we've never directly observed it."
• Scientists hope the lab buried 4,850 feet beneath the earth's surface will change that.
• On Wednesday, Gov. Dennis Daugaard is to give tours of the underground lab for scientists, dignitaries and media. William Brinkman of the federal Department of Energy confirmed his plans to attend Tuesday, said

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