Gamma-ray bursts continue to confound astrophysicists nearly a quarter century after their discovery (Klebesadel, Strong, and Olson 1973). Despite intense study by observers and theorists alike, no one knows for sure what they are, where they come from, or even whether or not they are a single phenomenon.
There are many reasons for this. The bursts occur at largely random times and come from largely random directions. We know their positions on the sky only approximately. They are a non-thermal phenomenon that exhibits a great diversity of time histories and a wide range of characteristic spectral energies. Furthermore, we know no quiescent counterparts of the bursts at radio, infrared, optical, ultraviolet, X-ray, or gamma-ray energies, and thus study of the bursts is isolated from the rest of astronomy and astrophysics. As a result, astronomers have been unable to bring the power of ground-based and space-based telescopes to bear on the questions of their nature and the distance scale to them. At present, those who study gamma-ray bursts have only the laws of physics and the properties of the bursts themselves to guide them.