Blue Light in Dark Ice

Down in Antarctica, the "Ice Cube" neutrino telescope was completed this month. It is an amazing piece of gear in an awesome location. Essentially, they use a 1 kilometer square piece of pure Antarctic ice as the detector -- when a neutrino hits a water molecule, it makes a bit of blue light and from this light the direction of the neutrino can be determined. But there is a problem: cosmic rays can create the same kind of blue light. So there's noise. They need a filter, right? Yes, and for this purpose they use... THE EARTH. They put the blue light detector at the TOP of the cube and look DOWN, down through the Earth! Only neutrinos get through.

For more details: http://www.icecube.wisc.edu/info/explained.php