In the last hundred years, modern physics and cosmology have shown that there exist regions of the universe forever beyond our reach, hidden by truly ultimate horizons. Such regions exist in those remote parts of the universe where, from our point of view, space expands faster than the speed of light. They are found in black holes, where the gravity is strong enough to retain even light within its field of attraction. And in the realm of the very small, quarks must remain forever confined to their world of extreme density and can never be removed from it. The aim of this book is to describe these ultimate horizons, how they were discovered, how they shape our view of the world, and what clues we have about a world beyond them.

Helmut Satz is professor of theoretical physics at Bielefeld University in Germany. A pioneer in the study of matter at extreme temperatures and densities, he and his group initiated the investigation of such matter using computer simulation techniques, providing results that were essential for the start of high energy nuclear collision experiments. Satz spent many years on the staff of Brookhaven National Laboratory and also at CERN, in Geneva, where he provided theoretical guidance to the experimental groups. In Bielefeld, he served for several years as director of the Center for Interdisciplinary Research, supporting the dialogue between the different fields of research. Prof. Dr. Helmut Satz University of Bielefeld 33619 Bielefeld Germany