ALSO BY CARLO ROVELLI
The Order of Time
Reality Is Not What It Seems: The Journey to Quantum Gravity
Seven Brief Lessons on Physics
The First Scientist: Anaximander and His Legacy
RIVERHEAD BOOKS
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Copyright © 2020 by Adelphi Edizioni, SpA
Translation copyright © 2021 by Erica Segre and Simon Carnell
Originally published in Italy as Helgoland by Adelphi Edizioni, Milan, in 2020.
First published in English in Great Britain by Allen Lane, an imprint of Penguin Random House Ltd., London, in 2021.
First North American edition published by Riverhead Books, 2021.
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Library of Congress Cataloging-in-Publication Data
Names: Rovelli, Carlo, 1956– author. | Segre, Erica, translator. | Carnell, Simon, 1962– translator.
Title: Helgoland : making sense of the quantum revolution / Carlo Rovelli ; translated by Erica Segre and Simon Carnell.
Other titles: Helgoland. English
Description: First U.S. hardcover. | New York : Riverhead Books, 2021. | “Originally published in Italian under the title Helgoland by Adelphi Edizioni, Milan, in 2020”—Title page verso. | Includes bibliographical references and index.
Identifiers: LCCN 2020049573 (print) | LCCN 2020049574 (ebook) | ISBN 9780593328880 (hardcover) | ISBN 9780593328903 (ebook)
Subjects: LCSH: Quantum theory.
Classification: LCC QC173.96 .R6813 2021 (print) | LCC QC173.96 (ebook) | DDC 530.12—dc23
LC record available at https://lccn.loc.gov/2020049573
LC ebook record available at https://lccn.loc.gov/2020049574
Book design by Amanda Dewey, adapted for ebook by Maggie Hunt
Cover design: Jason Booher
pid_prh_5.7.0_c0_r0
To Ted Newman, who made me understand that I did not understand quantum theory
CONTENTS
LOOKING INTO THE ABYSS
PART ONE
I. A STRANGELY BEAUTIFUL INTERIOR
The Absurd Idea of the Young Heisenberg: Observables
The Misleading ψ of Erwin Schrödinger: Probability
The Granularity of the World: Quanta
PART TWO
II. A CURIOUS BESTIARY OF EXTREME IDEAS
Superpositions
Taking ψ Seriously: Many Worlds, Hidden Variables and Physical Collapses
Accepting Indeterminacy
III. IS IT POSSIBLE THAT SOMETHING IS REAL IN RELATION TO YOU BUT NOT IN RELATION TO ME?
There Was a Time When the World Seemed Simple
Relations
The Rarefied and Subtle World of Quanta
IV. THE WEB OF RELATIONS THAT WEAVES REALITY
Entanglement
The Dance for Three That Weaves the Relations of the World
Information
PART THREE
V. THE UNAMBIGUOUS DESCRIPTION OF AN OBJECT INCLUDES THE OBJECTS TO WHICH IT MANIFESTS ITSELF
Aleksandr Bogdanov and Vladimir Lenin
Naturalism without Substance: Contextuality
Without Foundation? Nāgārjuna
VI. “FOR NATURE IT IS A PROBLEM ALREADY SOLVED”
Simple Matter?
What Does “Meaning” Mean?
The World Seen from Within
VII. BUT IS IT REALLY POSSIBLE?
Acknowledgments
Notes
Illustration Credits
Index
LOOKING INTO THE ABYSS
Časlav and I are sitting on the sand a few steps from the shore. We have been talking intensely for hours. We came to the island of Lamma, across from Hong Kong, during the afternoon break of a conference. Časlav is a world-renowned expert on quantum mechanics. At the conference, he presented an analysis of a complex thought experiment. We discussed and rediscussed the experiment on the path through the coastal jungle leading to the shore, and then here, by the sea. We have ended up basically agreeing. On the beach there is a long silence. We watch the sea. “It’s really incredible,” Časlav whispers. “Can this be believed? It’s as if reality . . . didn’t exist . . .”
This is the stage we are at with quanta. After a century of resounding triumphs, having gifted us contemporary technology and the very basis for twentieth-century physics, the theory that is one of the greatest achievements of science fills us with astonishment, confusion and disbelief.
There was a moment when the grammar of the world seemed clear: at the root of the variegated forms of reality, just particles of matter guided by a few forces. Humankind could think that it had raised the Veil of Maya, seen the basis of the real. It didn’t last. Many facts did not fit. Until, in the summer of 1925, a twenty-three-year-old German spent days of anxious solitude on a windswept island in the North Sea: Helgoland—in English also Heligoland—the Sacred Island. There, on the island, he found the idea that made it possible to account for all recalcitrant facts, to build the mathematical structure of quantum mechanics, “quantum theory.” Perhaps the most impressive scientific revolution of all time. The name of the young man was Werner Heisenberg, and the story told in this book begins with him.
Quantum theory has clarified the foundations of chemistry, the functioning of atoms, of solids, of plasmas, of the color of the sky, the dynamics of the stars, the origins of galaxies . . . a thousand aspects of the world. It is at the basis of the latest technologies: from computers to nuclear power. Engineers, astrophysicists, cosmologists, chemists and biologists all use it daily; the rudiments of the theory are included in high school curricula. It has never been wrong. It is the beating heart of today’s science. Yet it remains profoundly mysterious, subtly disturbing.
It has destroyed the image of reality as made up of particles that move along defined trajectories—without, however, clarifying how we should think of the world instead. Its mathematics does not describe reality. Distant objects seem magically connected. Matter is replaced by ghostly waves of probability.
Whoever stops to ask themselves what quantum theory has to say about the actual world remains perplexed. Albert Einstein, even though he had anticipated ideas that put Heisenberg on the right track, could never digest it himself. Richard Feynman, the great theoretical physicist of the second half of the twentieth century, wrote that nobody understands quanta.
But this is what science is all about: exploring new ways of conceptualizing the
