My purpose in writing this book is to enquire into the solar system and how it came to be. So much progress has been made in the past decade that this book has been completely rewritten from the first edition. The seven large chapters in that edition have been restructured into fifteen smaller ones that deal more readily with the increased flood of information.

As in the first edition, I have tried to place the solar system in the broader context of the universe. My excuse for venturing into fields such as cosmology is to reinforce the point that the solar system is a relative newcomer in the universe and came about through a fortunate sequence of chance events. A secondary purpose is to try to overcome the narrow and potentially hazardous specialization that is endemic in science and that I talk about in the Prologue. I have attempted to educate myself in fields remote from my own through discussions with many colleagues, listed in the Acknowledgments.

The book does not follow the usual descriptive arrangement of starting with Mercury and marching stolidly out through the giant planets to Pluto. Instead, the unconventional arrangement I have adopted here has arisen naturally as I have tried to explain how the system arose from the solar nebula and why the various bodies happen to be where they are. The result is that there are many associations that may at first sight seem surprising.