ABSTRACT
The study of gamma rays from astronomical sources has made many contributions to astronomy but none has been so startling and so revolutionary as the study of gamma-ray bursts (GRBs). The discovery of GRBs has provided one of the great puzzles in astrophysics in the last few decades and it has introduced the astronomical community to a whole new concept in astronomy: the astronomy of objects seen only once and then only for a very short time (figure 13.1). That these fleeting bursts should not be a local phenomenon but should originate in sources at cosmic distances is even more surprising. They are the most luminous emissions in the universe in any wavelength band and are perhaps the brightest phenomenon since the Big Bang. Because they are at cosmological distances, they offer a new tool for the exploration of objects on the edge of the observable universe.
