Super-Kamiokande Built in an abandoned mine, the "Super-K" neutrino detector surrounds 50,000 gallons of super pure water with 11,200 photomultiplier tubes. To give an idea of the scale, that object in the distance is two men in a rubber raft. courtesy of the Science and Technology Facilities Council of the UK
From Popular Science:
The questions that plague particle physicists and cosmology buffs seem fundamental, but it's startling how little we really know about some of them; for instance, why does matter exist? Researchers in Japan are undertaking the most sensitive subatomic particle experiment ever ventured in attempt to get to the bottom of that question, shooting neutrinos nearly 300 miles under the mountains, straight through the bedrock under Japan to a detector on the opposite coast, in an attempt to hash out exactly why neutrinos appear to spontaneously change from one kind to another.
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