ORIGIN OF THE HIGHEST ENERGY COSMIC-RAYS

After briefly recalling the history of discovery of cosmic rays, the p resent status of the subject is discussed, Cosmic-ray particles with e nergy exceeding 10(20) eV have been detected, The origin of cosmic ray s remains an unsolved problem in physics and astrophysics. The nature of the source(s) as well as the physical mechanism(s) responsible for endowing the cosmic-ray particles with extremely high energies are not known with certainty, We discuss some recent ideas in this context wi th special emphasis on the problem of origin of the highest-energy cos mic rays.