Cosmology, the study of the universe, arouses a great deal of public interest, with serious articles both in the scientific press and in major newspapers, with many of the theories and concepts (e.g. the 'big bang' and 'black holes') discussed, often in great depth. Accordingly the book is divided into three parts : Part 1 is readable (and understandable) by anyone with a nodding acquaintance with the basic language of cosmology: events, lights paths, galaxies, black holes and so on. It covers the whole story of the book in a way as untechnical as possible given the scope of the topics covered. Part 2 covers the same ground again but with enough technical details to satisfy a reader with basic knowledge of mathematics and/or physics. Part 3 consists of appendices which are referred to in the other parts and which also contain the highly technical material omitted from Section 2.