The physics of neutrinos - uncharged elementary particles that are key to helping us better understand the nature of our universe. This title shows how studies of neutrinos produced by such phenomena as cosmic rays in the atmosphere and nuclear reactions in the solar interior to provide striking evidence that neutrinos have mass. 'This is a very useful book written by notable experts in the field. It covers all aspects of the theory, phenomenology, experiment, and astrophysical implications of neutrinos."-Paul Langacker, professor emeritus, University of Pennsylvania