At Los Alamos National Laboratory, fiberglass cones await the arrival of particles from a cosmic-ray shower. Each cone, part of an experiment called CYGNUS, contains a plastic sheet that scintillates when a particle strikes it; a phototube at the top of each cone senses the faint burst of light.
Throughout the 1930s and 1940s, scores of young physicists scaled mountaintops in an effort to record ever higher energy cosmic-ray showers striking Earth.
Our planet acts as a filter to screen unwanted background noise, particularly from neutrinos created in cosmic-ray showers in the atmosphere near the North Pole.
In addition to greater sensitivity, this array would benefit from improved shielding against spurious signals from overhead cosmic-ray showers. "You could build a cube a kilometer on a side," he says.