I humbly dedicate this book to all those who commit their lives to enable the exploration of space by humans and machines. To those who make it possible by their engineering, scientific and medical research, by their creative achievements and imaginative practice. To those who are now still in elementary school, are able to look forward to the joy of discovery, and will be the ones who return to the Moon, take the first steps on Mars, the outer planets and their moons. And last but certainly not least, this book is dedicated to the men and women who spend their lives - sometimes sacrificing their lives - protecting the rest of us and our democracies so that we can spend our lives creating new worlds.