Editorial

Abstract

The 4th International LISA Symposium was held at the National Science Foundation Physics Frontier Center for Gravitational Wave Physics at The Pennsylvania State University on 19-24 July 2002. This special issue of Classical and Quantum Gravity is the proceedings of this meeting.LISA - the Laser Interferometer Space Antenna - is part of an international effort to open a new window on the universe. Not all things radiate light, but everything gravitates. Observations of the gravitational waves radiated by black holes and compact binary star systems, in our galaxy and beyond, can reveal details about these systems and their environments that are otherwise inaccessible.The international effort, of which LISA is a part, includes ground-based detectors, and the relationship between LISA and its ground-based detector 'cousins' was an important theme for this Symposium. LISA will observe gravitational waves in the 0.1 mHz to 0.1 Hz band, complementing observations made by ground-based detectors in the 10 Hz to several KHz band. Together they will explore nearly six decades of bandwidth in the gravitational-wave sky. LISA in particular will observe the gravitational waves radiated by the coalescence of black holes at the centres of colliding galaxies, and the inspiral of compact neutron stars or stellar-mass black holes onto these black holes, virtually anywhere in the universe. It will take a census of neutron star or close white dwarf binaries in our own galaxy and observe the formation of large black holes from the very first structures to form and collapse in our universe. In doing all these things, it will shed new 'light' on the first structures to form in the universe, explore the evolution of galaxies and the roles that black holes play in their structure, test relativity near the 'edges' of a black hole, and deepen our understanding of stellar and binary system evolution.A successful conference - and this LISA Symposium, like its predecessors, was very successful - does not just happen. It is the result of the work of many individuals and teams working together on scientific organization, travel, visa, lodging and financial logistics and planning. When all these things come together just right, as they did in July of 2002, it enables the speakers and participants to make something truly remarkable happen. It is my pleasure to thank the local organizing and scientific organizing committees, the accommodating staff of the Penn State Conference Center, and Penn State Transportation Services for their help and cooperation. I would like to single out for special thanks and appreciation the tireless Karen Brewster, whose energy, vigour and focus overcame all logistical obstacles, freeing the participants to focus on the exciting science that LISA will enable. In the end, however, it is the speakers and the participants who make a successful meeting. I look forward to the continued growth of the LISA Community and to meeting you all at the 5th International LISA Symposium, to be held at ESTEC in July 2004.Lee Samuel FinnPenn State University