FLOWS AND SHOCKS IN ACTIVE GALAXIES AND THEIR NUCLEI

Observations of active galactic nuclei imply that shocks must be an es sential and important part of their structure. We outline the basic ob servations, and discuss those features which must be addressed by any physical model of active nuclei. These features, in particular the obs erved spectrum of strong emission and absorption lines, lead naturally to the conclusion that shocks are present. The velocity widths of the se lines, which range from hundreds to many thousands of kilometres pe r second, are most readily explained by models in which shocks play an important role in the generation of cool gas. The extreme parameters of the shocks in and around active nuclei provide a unique application for the physics discussed in this meeting.