Neutrinos have an enormous penetrating power. This is due to the fact that they carry no electrical charge and that they are subject only to the weak interaction. Since they have no electrical charge, neutrinos cannot be detected directly but only through interaction with a collision partner such as an atomic nucleus.

If for example a high energy muon neutrino interacts with an atomic nucleus the neutrino may disappear and an energetic muon is ejected from the collision. Its trajectory follows essentially along the projection of the initial direction of the incident neutrino. Since the muon possesses electrical charge it can be detected with conventional methods. Its trajectory, direction of motion and energy can be determined and likewise that of the neutrino and therefore the direction to the source, but not its distance. Thus, a detector that can determine trajectory and direction of motion of a muon can be used as a muon neutrino telescope.

Since neutrinos belong to the class of weakly interacting particles, their so-called interaction cross section is extremely small, i.e., they are very rarely subject to interaction with a collision partner. This explains their extreme penetrating power.

The properties of muons are very similar to those of neutrinos. They, too, are subject to the category of weak interactions, however, they have a much larger mass. Since they carry electrical charge they are also subject to electromagnetic interactions which, in comparison to neutrinos, reduce their penetrating power significantly, but compared to other particles it is still very large. As an example a muon that has an energy of 10^12 eV can penetrate about one kilometer of water.