Reality Is Not What It Seems: The Journey to Quantum Gravity

by Carlo Rovelli, Simon Carnell (Translator), Erica Segre (Translator)

Overview

From the New York Times–bestselling author of Seven Brief Lessons on Physics, a closer look at the mind-bending nature of the universe.

What are time and space made of? Where does matter come from? And what exactly is reality? Theoretical physicist Carlo Rovelli has spent his whole life exploring these questions and pushing the boundaries of what we know. Here he explains how our image of the world has changed over the last few dozen centuries.

In elegant and accessible prose, Rovelli takes us on a wondrous journey from Aristotle to Albert Einstein, from Michael Faraday to the Higgs boson, and from classical physics to his own work in quantum gravity. As he shows us how the idea of reality has evolved over time, Rovelli offers readers a deeper understanding of the theories he introduced so concisely in Seven Brief Lessons on Physics. His evocative explanations invite us to imagine, beyond our ever-changing idea of reality, a whole new world that has yet to be discovered.


From the Hardcover edition.

Product Details

ISBN-13:	9780735213944
Publisher:	Penguin Publishing Group
Publication date:	01/24/2017
Sold by:	Penguin Group
Format:	eBook
Pages:	288
File size:	14 MB
Note:	This product may take a few minutes to download.

About the Author

Carlo Rovelli, an Italian theoretical physicist, is the head of the quantum gravity group at the Centre de Physique Théorique of Aix-Marseille Université. He is one of the founders of the loop quantum gravity theory and the author of the international bestseller Seven Brief Lessons on Physics. Rovelli lives in Marseille, France.


From the Hardcover edition.

Read an Excerpt

INTRODUCTION
Walking Along the Shore

We are obsessed with ourselves. We study our history, our psychology, our philosophy, our gods. Much of our knowledge revolves around ourselves, as if we were the most important thing in the universe. I think I like physics because it opens a window through which we can see further. It gives me the sense of fresh air entering the house.

What we see out there through the window is constantly surprising us. We have learned a great deal about the universe. In the course of the centuries, we have come to realize just how very many wrong ideas we had. We thought that Earth was flat, and that it was the still center of our world. That the universe was small, and unchanging. We believed that humans were a breed apart, without kinship to the other animals. We have learned of the existence of quarks, black holes, particles of light, waves of space, and the extraordinary molecular structures in every cell of our bodies. The human race is like a growing child who discovers with amazement that the world consists not just of his bedroom and playground, but that it is vast, and that there are a thousand things to discover, and innumerable ideas quite different from those with which he began. The universe is multiform and boundless, and we continue to stumble upon new aspects of it. The more we learn about the world, the more we are amazed by its variety, beauty, and simplicity.

But the more we discover, the more we understand that what we don’t yet know is greater than what we know. The more powerful our telescopes, the more strange and unexpected are the heavens we see. The closer we look at the minute detail of matter, the more we discover of its profound structure. Today we see almost to the Big Bang, the great explosion from which, fourteen billion years ago, all the galaxies were born—but we have already begun to glimpse something beyond the Big Bang. We have learned that space is curved but already foresee that this same space is woven from vibrating quantum grains.

Our knowledge of the elementary grammar of the world continues to grow. If we try to put together what we have learned about the physical world in the course of the twentieth century, the clues point toward something profoundly different from what we were taught at school. An elementary structure of the world is emerging, generated by a swarm of quantum events, where time and space do not exist. Quantum fields draw together space, time, matter, and light, exchanging information between one event and another. Reality is a network of granular events; the dynamic that connects them is probabilistic; between one event and another, space, time, matter, and energy melt into a cloud of probability.

This strange new world is slowly emerging today from the study of the main open problem in fundamental physics: quantum gravity. The problem of synthesizing what we have learned about the world with the two major discoveries of twentieth-century physics: general relativity and quantum theory. To quantum gravity, and the strange world that this research is unfolding, this book is dedicated.

This book is a live coverage of the ongoing research: what we are learning, what we already know, and what we think we are be- ginning to understand about the elementary nature of things. It starts from the distant origin of some key ideas that we use today to order our understanding of the world and describes the two great discoveries of the twentieth century—Einstein’s general relativity and quantum mechanics—trying to put into focus the core of their physical content. It tells of the picture of the world emerging today from research in quantum gravity, taking into account the latest indications given by nature, such as the confirmation of the cosmological Standard Model obtained from the Planck satellite and the failure at CERN to observe the supersymmetric particles that many expected. And it discusses the consequences of these ideas: the granular structure of space; the disappearance of time at small scale; the physics of the Big Bang; the origin of black hole heat— up to the role of information in the foundation of physics.

In a famous myth related by Plato in the seventh book of The Republic, some men are chained at the bottom of a dark cave and see only shadows cast upon a wall by a fire behind them. They think that this is reality. One of them frees himself, leaves the cave, and discovers the light of the sun and the wider world. At first the light, to which his eyes are unaccustomed, stuns and confuses him. But eventually he can see, and he returns excitedly to his companions to tell them what he has seen. They find it hard to believe.

We are all in the depths of a cave, chained by our ignorance, by our prejudices, and our weak senses reveal to us only shadows. If we try to see further, we are confused; we are unaccustomed. But we try. This is science. Scientific thinking explores and redraws the world, gradually offering us better and better images of it, teaching us to think in ever more effective ways. Science is a continual exploration of ways of thinking. Its strength is its visionary capacity to demolish preconceived ideas, to reveal new regions of reality, and to construct new and more effective images of the world. This ad- venture rests upon the entirety of past knowledge, but at its heart is change. The world is boundless and iridescent; we want to go and see it. We are immersed in its mystery and in its beauty, and over the horizon there is unexplored territory. The incompleteness and the uncertainty of our knowledge, our precariousness, suspended over the abyss of the immensity of what we don’t know, does not render life meaningless: it makes it interesting and precious.
 
I have written this book to give an account of what—for me—is the wonder of this adventure. I’ve written with a particular reader in mind: someone who knows little or nothing about today’s physics but is curious to find out what we know, as well as what we don’t yet understand, about the elementary weave of the world— and where we are searching. And I have written it to try to communicate the breathtaking beauty of the panorama of reality that can be seen from this perspective.

I’ve also written it for my colleagues, fellow travelers dispersed throughout the world, as well as for the young women and men with a passion for science, eager to set out on this journey for the first time. I’ve sought to outline the general landscape of the structure of the physical world, as seen by the double lights of relativity and of quantum physics, and to show how they can be combined. This is not only a book of divulgation; it’s also one that articulates a point of view, in a field of research where the abstraction of technical language may sometimes obscure the wide-angle vision. Science is made up of experiments, hypotheses, equations, calculations, and long discussions; but these are only tools, like the instruments of musicians. In the end, what matters in music is the music itself, and what matters in science is the understanding of the world that science provides. To understand the significance of the discovery that Earth turns around the sun, it is not necessary to follow Copernicus’s complicated calculations; to understand the importance of the discovery that all living beings on our planet have the same ancestors, it is not necessary to follow the complex arguments of Dar- win’s books. Science is about reading the world from a gradually widening point of view.

This book gives an account of the current state of the search for our new image of the world, as I understand it today. It is the reply I would give to a colleague and friend asking me, “So, what do you think is the true nature of things?” as we walk along the shore on a long midsummer’s evening.

Table of Contents

Preface 1

Introduction: Walking Along the Shore 5

Part 1 Roots

1 Grains 15

Is there a Limit to Divisibility? 23

The Nature of Things 32

2 The Classics 41

ISAAC and the Little Moon 41

Michael: Fields and Light 53

Part 2 The Beginning of the Revolution

3 Albert 67

The Extended Present 69

The Most Beautiful of Theories 77

Mathematics or Physics? 91

The Cosmos 94

4 Quanta 109

Albert Again 110

Niels, Werner, and Paul 114

Fields and Particles are the Same Thing 126

Quanta 1 Information is Finite 130

Quanta 2 Indeterminacy 132

Quanta 3 Reality is Relational 134

But do we Really Understand? 137

Part 3 Quantum Space and Relational Time

5 Spacetime Is Quantum 147

Matvei 151

John 154

The Loops' First Steps 159

6 Quanta of Space 161

Spectra of Volume and Area 163

Atoms of Space 169

Spin Networks 171

7 Time Does Not Exist 175

Time is not What we Think it is 177

The Candle Chandelier and the Pulse 179

Spacetime Sushi 183

Spinfoams 186

What is the World Made of? 192

Part 4 Beyond Space and Time

8 Beyond the Big Bang 201

The Master 201

Quantum Cosmology 206

9 Empirical Confirmations? 210

Signs from Nature 214

A Window onto Quantum Gravity 218

10 Quantum Black Holes 222

11 The End of Infinity 230

12 Information 238

Thermal Time 249

Reality and Information 253

13 Mystery 258

Notes 266

Annotated Bibliography 270

Index 273

Editorial Reviews

Some physicists, mind you, not many of them, are physicist-poets. They see the world or, more adequately, physical reality, as a lyrical narrative written in some hidden code that the human mind can decipher. Carlo Rovelli, the Italian physicist and author, is one of them…Rovelli's book is a gem. It's a pleasure to read, full of wonderful analogies and imagery and, last but not least, a celebration of the human spirit.”—NPR Cosmos & Culture
 
“If your desire to be awestruck by the universe we inhabit needs refreshing, theoretical physicist Carlo Rovelli…is up to the task.”—Elle

“[Reality Is Not What It Seems] is simultaneously aimed at the curious layperson while also useful to the modern scientist… Rovelli lets us nibble or gorge ourselves, depending on our appetites, on several scrumptious equations. He doesn’t expect everyone to be a master of the equations or even possess much mathematical acumen, but the equations serve as appetizers for those inclined to get their fill, so to speak.”—Raleigh News & Observer

“With its warm, enthusiastic language and tone, [Seven Brief Lessons on Physics] is also deeply humanistic in approach, using words like elegant and beauty about a subject…that can seem impenetrably dense and abstract…Reality Is Not What It Seems takes much the same approach.”—New York Magazine

“Rovelli writes beautiful prose while walking the reader through the history and concept of 'reality' and what it all means for the yet to be discovered universe and thus our own lives.”—Pasadena Star-News

“Rovelli writes with elegance, clarity and charm. . . . A joy to read, as well as being an intellectual feast.”—New Statesman

“Rovelli offers vast, complex ideas beyond most of our imagining—‘quanta,’ ‘grains of space,’ ‘time and the heat of black holes’—and condenses them into spare, beautiful words that render them newly explicable and moving.”—On Being with Krista Tippett

“Rovelli’s lyrical language, clarity of thought, and passion for science and its history make the title a pleasure to read (albeit slowly), and his diagrams and footnotes will allow readers to understand the material better and tackle a more expert level of insight.”—Booklist

“Rovelli smoothly conveys the differences between belief and proof. . . his excitement is contagious and he delights in the possibilities of human understanding.”—Publishers Weekly

“Science buffs will admire Rovelli's lucid writing…Cutting-edge theoretical physics for a popular audience that obeys the rules (little math, plenty of drawings), but it's not for the faint of heart.”—Kirkus Reviews

“A fascinating adventure into the outer limits of space and into the smallest atom…Rovelli manages to break down complex, proven ideas into smaller, easily assimilated concepts so those with little to no scientific background can understand the fundamental ideas…Rovelli's infectious enthusiasm and excitement for his subject help carry readers over the more difficult aspects, allowing one to let the imagination soar…An exciting description of the evolution of physics takes readers to the edge of human knowledge of the universe.”—Shelf Awareness

“Rovelli draws deep physics into the light with rather greater success... He wears a broad erudition lightly, casually and clearly explaining.”—Read It Forward

From the Publisher

Here’s a flawless, up-to-date history of physics, from antiquity to yesterday (almost). One can’t tell that it’s translated from Italian, so smoothly does the narration flow. Narrator Roy McMillan’s voice gives the impression of a learned speaker embarking on a friendly explanation of abstruse concepts and discoveries. Having listened to many science audiobooks and other presentations, this reviewer says that this is one of the best. For example, quantum theory, well known to be opaque to even highly trained scientists, is described so lucidly that the listener almost understands it. That’s saying something. D.R.W. © AudioFile 2017, Portland, Maine

FEBRUARY 2017 - AudioFile

2016-10-20
When theoretical physicist Rovelli's Seven Lessons in Physics became an international bestseller in 2015, his Italian publisher proceeded to translate this, his previous book, which turns out to be an admirable addition to a popular genre: explaining what scientists know about the universe and their struggles to learn more.Most authors in this subject begin with the Greeks and make their ways through Newton, Galileo, and Maxwell to the glories of Einstein's relativity and the founders of quantum mechanics. In good hands, this is a smooth ride, and Rovelli—the head of the Quantum Gravity group at Aix-Marseille University and one of the founders of the loop quantum gravity theory—is good. Then the story gets tougher. Relativity and quantum mechanics are incompatible, and physicists today are trying to combine them to produce a single, satisfying theory of everything. This requires complex ideas that dissect everything, space-time included, to a very, very tiny state where their quintessence emerges. Rovelli delivers a respectful nod to string theory, but he belongs to the rival school of quantum loop gravity, the central feature of which is that space itself is quantized. "The central prediction of loop theory is…that space is not a continuum," writes the author, "it is not divisible ad infinitum, it is formed of ‘atoms of space,' a billion billion times smaller than the smallest of atomic nuclei." Got it? For some readers, the narrative will be a slog. Science buffs will admire Rovelli's lucid writing, but at some point, many will realize that they no longer understand. Cutting-edge theoretical physics for a popular audience that obeys the rules (little math, plenty of drawings), but it's not for the faint of heart.

Kirkus Reviews