Two subjects, astrophysics and relativity, were combined in different proportions in the six papers that made up my dissertation (physics, Caltech, 1980). As I wrote in the introduction to that document, some of the work which I undertook was almost "pure" general relativity; the astrophysical universe supplied only a motivation or an application for the mathematical problem being investigated. Others of my studies were much more oriented toward the astrophysical; relativity appeared, at most, in a weak-field, slow-motion approximation. In either case, relativity and astrophysics acted synergistically, so that in their collaboration the whole was more than the sum of the separate parts.
On a larger scale, the same phenomenon has occurred in modern astronomy. Our understanding of the universe has been enriched by an influx of ideas from general relativity, especially as those ideas were applied to "violent" events such as quasars, collapses to form black holes, and the birth of the universe itself. Theoretical relativity has its very raison d'être grounded in astronomically-observed fact, and much of the development of the field was guided and nurtured through problems posed by astrophysics. More cross-fertilization between these two subjects will certainly follow the first confirmed observations of gravitational radiation.
So the partnership between astrophysics and relativity in my thesis is not a new one. The specific object that has frequently embodied that partnership, the neutron star, is also not new. Speculation about and theoretical work on the structure of neutron stars dates back to the 1930s, and evidence accumulated from pulsar observations beginning in the 1960s has both solidified and extended the theoretically-acquired knowledge. The human mind, however, always seems to retain a fascination with extremes: the highest, the hottest, the smallest, the fastest, etc. As (probably) the densest material objects in the universe, neutron stars have a natural attraction (^_^) --- and they have repaid the attention given them by yielding a stream of discoveries. As central as neutron stars have been to a variety of fields in modern astrophysics, it was fitting that they should supply a central core for several of the projects I undertook in grad school.
As I wrote in 1979 when concluding the introductory essay to my minimum opus:
The universe is an exciting place! In particular, the hot or fast or dense objects which bring relativistic effects into prominent display are interesting and rewarding subjects for investigation. Most of the work included in this dissertation has its ultimate roots in my personal fascination with astronomy, which began about the time I was six years old and first looked through a small telescope, and which developed during years of reading and asking stupid questions. I've finally understood a few things, at least in part, and have had some fun describing them in the chapters of this thesis. If I am required to give reasons or motivations for all that I've written herein, I must eventually fall back upon the enjoyment that it has given me. I suspect that the joy of discovering and of explaining one's discoveries is fundamental to a lot of people. If what I've done adds to anyone else's pleasure, or suggests something new and amusing for them to ponder, that's an unexpected bonus.
Two decades later, I agree.
Wednesday, March 29, 2000 at 18:19:21 (EST) = Datetag20000329