This year marks the anniversary of a serendipitous discovery made by Victor Hess in his 1912 balloon flight: the discovery of what later was called the cosmic radiation. Attempts to understand this enigmatic phenomenon provided the motivation for developments that greatly affected the course of physics and astronomy through the following century. First, early studies of cosmic-ray interactions in the atmosphere laid the foundations of high-energy particlephysics, before accelerator laboratories entered this field in the mid-1900's. Subsequently, stratospheric balloons and space probes begun to make possible direct observations of cosmic rays above the atmosphere. These observations led to other entirely new areas of research: particle astrophysics, astronomy with gamma-rays and x-rays, and space plasma physics. Among the numerous institutions involved in cosmic-ray research world-wide, the University of Chicago played a major role from the 1920's to the present time. We shall review some of these activities, from the emotional battles about the nature of the cosmic rays in the early times, to particle physics experiments in the 1930's and 1940's, to in-situ studies in space and on balloons since the 1960's, and to the return to ground-based installations at present.

Argonne Physics Division Colloquium Schedule