“Although this book is about what we cannot know, it is also very important to understand what we do know. On this journey to the limits of knowledge, we will go through areas already mapped by scientists, to the very limits of the latest scientific achievements to date. Along the way, we will pause to consider those moments when scientists thought they had reached a dead end and further progress was impossible, but the next generation of researchers found other ways. This will allow us to take a fresh look at what we may today consider unknowable. I hope that by the end of our journey this book will be a comprehensive overview not only of what we cannot know, but also of what we already know.”