The cosmos is full beyond measure of elegant truths; of exquisite interrelationships; of the awesome machinery of nature.
—Carl Sagan, “The Shores of the Cosmic Ocean"
episode of Cosmos: A Personal Voyage (1990)
Until now we have concentrated on the observations and theory of GRBs. The events have shown themselves as a complex, panchromatic phenomenon that can arise from a variety of different progenitors in both the nearby and distant Universe. The GRB community has succeeded in measuring the diversity of basic parameters of the explosions and clearly learned a great deal about the physics of the emission mechanisms. But despite a raft of certainties, we could fill a book with what we do not know. ...