Absolute neutrino masses provide a key to physics beyond the standard model.
We discuss the impact of absolute neutrinos masses on physics beyond the
standard model, the experimental possibilities to determine absolute neutrinos
masses, and the intriguing connection with the Z-burst model for extreme-energy
cosmic rays.Comment: 11 pages, 4 figures. Talk given by H. Paes at the NOON2001 workshop,
ICRR, University of Tokyo, Kashiwa, Japan; 2 references update