Associated Press
A sign warns visitors not to tap the glass of an above-ground version of the laboratory to be opened nearly 4,900 feet beneath the earth in Lead, S.D. Tuesday, May 29, 2012. The lab's experiments will include the world's most sensitive dark-matter detector. Scientists say that the Sanford Underground Research Facility _ housed inside the now-shuttered Homestake Gold Mine _ could help scientists understand the origins of the universe. (AP Photo/Amber Hunt)

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