Scientific Colloquium
December 5,  2003


The study of celestial sources in their X-ray light has provided a powerful
new tool for discovery of new aspects of the Universe.  The astrophysical problems,
which were posed by the first discovery of extra-solar X-ray emissions, were solved
over a period of four decades.  This progress was made possible by the advent of
ever more sophisticated observations and techniques.  The scientific and technological
developments in particular areas of interest to the speaker will be described.