In fact, there are several holes, and they are being used as astronomical observatories. Lowered into each hole is a string knotted with basketball-sized light detectors. The detectors are sensitive to blue light emitted in the surrounding clear ice. Such light is expected from ice collisions with high-energy neutrinos emitted by objects or explosions out in the universe. The above picture was taken 750 meters below the surface, looking down into an abyss over 2000 meters deep.
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