There have been (theoretical) proposals to use them to communicate with submarines: http://www.physics.ucla.edu/~hauser/neutrino_communication_paper/siljah_mod.

There have been (theoretical) proposals to use them to communicate with submarines: http://www.physics.ucla.edu/~hauser/neutrino_communication_paper/siljah_mod.htm http://www.physics.ucla.edu/~hauser/neutrino_communication_p... > Neutrinos have many properties that would make them superior even to the extremely low radio frequencies. Because neutrinos are nearly unaffected by matter, a neutrino beam could traverse directly through the earth from the transmission site to the submarine. A directional beam would allow confidential information to be passed only to the intended recipient. Neutrino communications would also be totally jam-proof. As an additional benefit, a neutrino message could be received in the deepest of waters, leaving a submarine less vulnerable to enemy attacks.