  In the past four decades a new type of astronomy has emerged, where instead
of looking up into the sky "telescopes" are buried miles underground or deep
under water or ice and search not for photons (that is, light), but rather for
particles called neutrinos. Neutrinos are nearly massless particles that
interact very weakly with matter. The detection of neutrinos emitted by the Sun
and by a nearby supernova provided direct tests of the theory of stellar
evolution and led to modifications of the standard model describing the
properties of elementary particles. At present, several very large neutrino
detectors are being constructed, aiming at the detection of the most powerful
sources of energy and particles in the universe. The hope is that the detection
of neutrinos from these sources, which are extra-Galactic and are most likely
powered by mass accretion onto black-holes, will not only allow study of the
sources, but, much like solar neutrinos, will also provide new information
about fundamental properties of matter.
