Neutrinos are hard to spot because they are small and have no charge and very little mass.
The vast majority of them rip right through the Earth without stopping. Since they rarely interact, high-energy neutrinos tend to travel in straight lines, thereby revealing the location of the energetic regions of the universe from which they originate. It is for this reason that they are of profound interest to astronomers. A cone of Cerenkov light reveals the direction of the original neutrino. Although other detectors have already made important contributions to this field, a large detector is required to catch rare, high-energy neutrinos.