  The symmetry between quarks and leptons suggests that neutrinos should have
mass. As embodied in the grand unified theory SO(10) this yields masses that
can only be detected by neutrino oscillations. Such oscillations could be very
important for supernova physics. Present observations of solar neutrinos when
combined with standard solar model calculations imply particular parameters for
neutrino masses and mixings. If the solar model is somewhat relaxed quite
different possibilities emerge, which yield very different predictions for
future experiments.
