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.