Our conference - opening today - has two aims in view: first, to commemorate some milestones in the development of the studies of close binary systems whose anniversaries fall in these years, as well as to take stock of our present knowledge accumulated through out preceding decades, in order to consider where do we go from here. This summer, 310 years will have elapsed since the first ec lipsing binary - Algol - was discovered in Bologna by Geminiano Montanari (1633-1687) to be a variable star; and 198 years have gone by since John Goodricke of York (1764-1786) established the fact that Algol's light changes were periodic. Moreover, it is al most exactly (to a month) now 100 years since Edward Charles Pickering (1846-1919) of Harvard Observatory in the United States took the first steps towards the development of systematic methods of analysis of the light changes of Algol and related systems - a topic which will constitute the major part of the programme of our present conference. The three dates recalled above illustrate that the discoverers of such celestial objects and observers of their light changes have been systematically ahead of the theoreticians endea vouring to understand the significance of the observed data by de cades and centuries in the past - a fact which, incidentally, con tinues to hold good (albeit with a diminishing lead-time) up to the present."

The area of diffuse astrophysical media is enormous and ranges over circum stellar to extragalactic scales. The physical conditions can vary from cool dusty gases to collections of relativistic particles. Flows in such media are set up by en ergy and momentum injection from winds, jets and explosions. The study of these phenomena involves physics, chemistry and, inevitably, hydrodynamics. One of the most important aspects of this study is the ever increasing overlap between theory and observation. Indeed, it can be argued that the only way to really understand these complex flows which can never be duplicated under terrestrial conditions, is to encourage this overlap, and this was one major aim of this Conference. Because of the long theoretical and observational association of the Manchester Group with this general area, Manchester seemed an appropriate venue for this Con ference. But in fact this long association and the actual year of the Conference are connected. In 1951 Franz Kahn joined the Astronomy Department at Manchester University and immediately the study of diffuse media, particularly the hydrody namic aspects, commenced and has flourished ever since. Franz became Head of the Astronomy Department in 1981 following the retirement of Professor Z. Kopal, who founded the Department and was instrumental in attracting Franz to it. In 1993, Franz retired from this position and a most serendipidous coincidence was his election to the Royal Society announced shortly before the Conference.

Our conference - opening today - has two aims in view: first, to commemorate some milestones in the development of the studies of close binary systems whose anniversaries fall in these years, as well as to take stock of our present knowledge accumulated through out preceding decades, in order to consider where do we go from here. This summer, 310 years will have elapsed since the first ec lipsing binary - Algol - was discovered in Bologna by Geminiano Montanari (1633-1687) to be a variable star; and 198 years have gone by since John Goodricke of York (1764-1786) established the fact that Algol's light changes were periodic. Moreover, it is al most exactly (to a month) now 100 years since Edward Charles Pickering (1846-1919) of Harvard Observatory in the United States took the first steps towards the development of systematic methods of analysis of the light changes of Algol and related systems - a topic which will constitute the major part of the programme of our present conference. The three dates recalled above illustrate that the discoverers of such celestial objects and observers of their light changes have been systematically ahead of the theoreticians endea vouring to understand the significance of the observed data by de cades and centuries in the past - a fact which, incidentally, con tinues to hold good (albeit with a diminishing lead-time) up to the present.