One hundred years after burning Giordano Bruno at the stake, the Vatican, under the weight of an avalanche of experimental information obtained with optical telescopes, officially recognized heliocentrism as Catholic canon. Within the last 40 years, however, the limitations of the optical telescope have become increasingly apparent. This motivates the search for alternative means of collecting astronomical information. Neutrinos are 'fundamental' particles in the sense that, like quarks or electrons, they are believed to have no constituents. This is contrasted with protons, for example, which are believed to contain three smaller quarks.
Neutrinos interact only by means of the 'weak' interactions, which are, indeed, quite weak.
A typical neutrino produced in the interior of the Sun will travel unscathed through a light-year of lead before interacting. Alternatively, neutrinos from the edge of the Universe will easily penetrate the interstellar medium without being absorbed or deflected.