- During my entire research life, friends and curious people have asked me to explain what was going on in quantum gravity research. How was it possible to study new ways of thinking about space and time? Over and over again I have been asked to write a popular account of this research. While books on cosmology or string theory abound, a book describing the research on the quantum nature of space and time, and on loop quantum gravity in particular, did not yet exist. I have long hesitated, because I wanted to concentrate on research. Some years ago, after completing my technical book on the subject, I felt that the collective work of many scientists had moved the topic to a stage mature enough for a popular book. The landscape we are exploring is enchanting; why keep it hidden?
- But I still delayed the project, because I could not 'see' the book in my head. How to explain a world without space and time? One night in 2012, during a long solitary drive from Italy to France, I realized that the only way to explain in a comprehensible manner the ongoing modifications of the notions of space and time was to tell the story from the beginning: starting from Democritus, all the way through to the quanta of space. After all, this is how I understand the story. I began to design the entire book in my mind while driving, and got increasingly excited, until I heard a police car's sirens telling me to pull over: I was driving far above the speed limit. The Italian policemen asked me politely if I was crazy to drive at that speed. I explained that I had just found the idea I’d been seeking for so long; the policeman let me go without a ticket, and wished me good luck with the book. This is the book.
- This book was written and first published in Italian at the beginning of 2014. Shortly afterwards, I wrote a few articles on fundamental physics for an Italian newspaper. A prestigious Italian publisher, Adelphi, asked me for an extended version of these articles, to appear as a small booklet. This is the origin of the short book Seven Brief Lessons on Physics, which to my immense surprise has become an international bestseller and has opened a beautiful channel of communication between me and so many wonderful readers all over the world. The Seven Lessons were thus written after this book, and to some extent they are a synthesis of some of the topics you find here. If you have read Seven Brief Lessons on Physics and want to know more, to journey deeper into the strange world that book sketched, here you can find more.
- While the account of established physics I give here is presented from the peculiar perspective in which I understand it, it is largely uncontroversial. However, the part of this book that describes current research in quantum gravity is my own personal understanding of the state of the art. This is the region at the boundary between what we have understood and what we do not yet understand, and is still far from achieving consensus. Some of my physicist colleagues will agree with what I write here; others won't. This is true for all presentations of ongoing research at the frontiers of knowledge, but I prefer to state it upfront and clearly. This is not a book about certainties: it is a book about the adventure of moving towards the unknown.
- As a whole, this is a travel book describing one of the most spectacular journeys that humanity has taken: a journey out of our limited and parochial views of reality, towards an increasingly vast understanding of the structure of things. A magical journey out of our common-sense view of things, far from complete.
→ Marseille, 4 May 2016
Author's Note – vii
Preface: Walking along the Shore – xi
- PART ONE: Roots
- Grains – 3
- The Classics – 27
- PART TWO: The Beginning of the Revolution
- Albert – 51
- Quanta – 91
- PART THREE: Quantum Space and Relational Time
- Spacetime is Quantum – 125
- Quanta of Space – 138
- Time Does Not Exist – 151
- PART FOUR: Beyond Space and Time
Annotated Bibliography – 235
- Beyond the Big Bang – 175
- Empirical Confirmations? – 183
- Quantum Black Holes – 195
- The End of Infinity – 202
- Information – 209
- Mystery – 228
Notes – 239
Index – 245
Penguin; 1st edition (1 June 2017)
Text Colour Conventions (see disclaimer)
- Blue: Text by me; © Theo Todman, 2021
- Mauve: Text by correspondent(s) or other author(s); © the author(s)