A computer then compares the signals from several photoreceptors to calculate the path of the light streak in three dimensions. From that, scientists have a good idea of the neutrino's point of origin. High-energy neutrinos emerge from some of the most violent phenomena in the universe, including supernovas, quasars, and other types of active galaxies. Because neutrinos barely interact with matter, they reach Earth still carrying unadulterated information about the cosmic events that produced them. Photons of visible light, in contrast, can get absorbed, obscured, and altered by intervening matter on its way to Earth.
Photons are very gregarious.
They interact with everything. But Earth is constantly showered with a far greater abundance of low-energy neutrinos generated in the sun or created when cosmic rays strike atoms in the upper atmosphere. Scientists have built giant underground water tanks to detect these solar neutrinos. A hole drilled about a mile down into Antarctic ice becomes the new home for a string of 10 to 16 photoreceptors, which will detect the light produced when a neutrino collides with a proton. Courtesy of Robert Morse.