  Forty years have passed since the first Explorer orbiting observatory - the
1958 mission used to discover the Van Allen radiation belts outside the
atmosphere - ushered in the modern age of space science. Even though in situ
observations of outer space are still restricted to measurements made within
the solar system, we now have access to a wide range of cosmic signals,
extending from the well understood microwave photons indicative of the earliest
epoch of the universe to those apparently inexplicable ultra-high energy
extragalactic cosmic ray particles that are too energetic (up to 50
Joules/each) to have survived passage through a cosmological extent of the
pervasive thermal relic radiation field. In this lecture the extremes of cosmic
ray physics are discussed within the context of particles having the lowest
energy (down to ~10**3 eV/nucleon) and highest energy (>10**20 eV), emphasizing
those aspects of astronomy, particularly gamma-ray and x-ray, that appear to be
especially revealing for these regimes.
