The One Read online

  Copyright © 2023 by Heinrich Päs

  Cover design by Chin-Yee Lai

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  Cover copyright © 2023 by Hachette Book Group, Inc.

  Illustrations by Frigga Päs

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  First Edition: January 2023

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  Wheeler’s U was first published in Zurek 1990, p. ix. Reprinted with permission of the estate of John Archibald Wheeler.

  Library of Congress Cataloging-in-Publication Data

  Names: Päs, H. (Heinrich), author.

  Title: The one : how an ancient idea holds the future of physics / Heinrich Päs.

  Description: First edition. | New York, NY : Basic Books, 2023. | Includes bibliographical references and index.

  Identifiers: LCCN 2022019806 | ISBN 9781541674851 (hardcover) | ISBN 9781541674844 (ebook)

  Subjects: LCSH: Physics—Philosophy. | Monism. | One (The One in philosophy) | Quantum theory. | Cosmology.

  Classification: LCC QC6 .P2965 2023 | DDC 523.101—dc23/eng20220927

  LC record available at https://lccn.loc.gov/2022019806

  ISBNs: 9781541674851 (hardcover), 9781541674844 (ebook)

  E3-20221122-JV-NF-ORI

  CONTENTS

  Cover

  Title Page

  Copyright

  Dedication

  Epigraph

  Introduction: Stargazing

  1: The Hidden One

  2: How All Is One

  3: How One Is All

  4: The Struggle for One

  5: From One to Science and Beauty

  6: One to the Rescue

  7: One Beyond Space and Time

  8: The Conscious One

  Conclusion: The Unknown One

  Acknowledgments

  Discover More

  Further Reading

  Glossary

  Notes

  Bibliography

  About the Author

  Also by Heinrich Päs

  For Sara

  You are the One for me

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  From all things One and from One all things.

  —HERACLITUS

  There are many indications that, following the recursive pattern of scientific revolutions, we are now witnessing the beginning of the phase of crisis… This is the most complex and intense moment of scientific research, when revolutionary and unprejudiced ideas are needed for a real paradigm change.

  —GIAN GIUDICE, HEAD OF THE THEORETICAL PHYSICS DEPARTMENT, CERN

  To lend wings to physics once again.

  —FRIEDRICH WILHELM JOSEPH SCHELLING

  INTRODUCTION

  Stargazing

  ONE VERY EARLY MORNING IN MID-OCTOBER 2009, I was waiting alone in a deserted and pitch-dark alley in San Pedro, in the middle of the Chilean Atacama Desert, one of the driest spots on earth. Above me, countless stars were sparkling, so mesmerizing that I struggled to keep an eye out for the tour guide’s truck, coming to pick me up for a trip up to the Altiplano to watch the flamingoes stalking a secluded salt flat in the first light of the rising sun. Never before or after have I seen a more magnificent sky, though there have been other, similarly magical moments: counting shooting stars from the deck of a sailboat while crossing the Baltic Sea, practicing full-moon surfing off Waikiki Beach in Hawaii, or stepping out of a ski cabin at night, halfway up a mountain in the Austrian Alps, only to be stopped in my tracks by the bright band of the Milky Way’s galactic disk. In such moments, I have felt entirely small and insignificant and yet, at the same time, strangely at home in the universe.

  But what does it mean to feel at home in the universe? What do we actually mean when we talk about the “universe”? Etymologically, the word comes from the Latin universum, meaning something like “all things combined together into one.” Yet, when we speak of the universe, we usually refer to outer space, our cosmic environment, stars, planets, galaxies, a vast realm filled with countless objects. Apparently, what we refer to as the “universe” and what the term actually means have little in common, if anything at all.

  Almost all the celestial objects you can identify in the night sky belong to our own galaxy, the Milky Way, which in total hosts more than one hundred billion stars. And the Milky Way itself is only one among about a trillion galaxies. As impressive as these numbers are, these visible objects are only the tiniest part of the entire universe. For every star you can spot out there, there exists about ten times more mass in nonluminous matter, such as gas clouds billowing around in interstellar space. Even more so, for all ordinary matter there exists five times as much mass in “dark matter,” expected to be made of exotic, unknown particles floating across the universe. And finally, there exists three times more “dark energy,” the puzzling fuel that drives the fabric of space-time to expand faster and faster.

  So much for our “universe.”

  But according to modern cosmology, maybe even our universe is not everything—there may be more than just a single universe. Cosmologists now describe an epoch of accelerating expansion in the very early times, called “cosmic inflation.” The inflationary period terminates in a hot plasma, which we can identify with the Big Bang. But nobody knows what happened before inflation. Was there an absolute beginning? Or did inflation go on forever, and is it maybe still going on outside our own universe, in other regions of a “multiverse”? In that case it may continue to produce innumerable other “baby universes,” popping up in an eternally inflating space. This, actually, is quite possible.

  But that is not enough to account for “everything” either. Not even close! Beyond parallel universes, dark energy, dark matter, and trillions of galaxies with a hundred billion stars each, there may yet exist a realm of infinite possibilities, where everything that, in principle, could exist actually does. There you would find innumerable copies of yourself, my cat, your dog, the flamingoes of the Altiplano, everyone, of all stars and galaxies and everything mentioned above. These parallel realities are the different branches of Hugh Everett’s infamous “many worlds” interpretation of quantum mechanics. In fact, they constitute another—arguably more fundamental—layer of multiverse. Increasingly more physicists are willing to accept now that they are an inherent prediction of quantum mechanics—that a functional notion of quantum mechanics is increasingly difficult to sustain without “many worlds.”

  And even this is not the end of the story. In addition to these parallel worlds, the quantum world contains infinite arbitrary “superpositions” of these realities. These are realities in which cats are half dead and half alive and where you are not either sitting in a chair and reading a book in the United States or driving a rental car through Europe but where both activities and places are mixed up in a way implying one cannot decide which one is true. The quantum realm encompasses everything that could be and all possible blends of these would-be realities.

  Yet, standing there, under the stars, I still felt that feeling that many humans have shared: that I was somehow one with the vastness beyond myself. Is there a more daring, courageous, and flat-out overwhelming thought than to conceptualize “the whole material world,” everything from “celestial bodies” to “life upon the earth” and from the “nebula stars to the mosses on the granite rocks,” as the great German naturalist and discoverer Alexander von Humboldt portrayed the universe, as “One”?1

  It seems bizarre to believe all of this could be connected. It sounds like a fairy tale fabricated by mystics or madmen. Yet the conviction that the universe is all “one” and the experience that it is comprised of many things have been an enduring conflict for humanity since its earliest days. “From all things One and from One all things”: twenty-five hundred years ago, the Greek philosopher Heraclitus had expressed the thought of an all-encompassing universe in its most radical way.2 This notion that there is but one object in the universe, the universe itself, is known to philosophers as “monism,” from the ancient Greek monos, meaning “unique.” It has inspired Plato’s dialogues, Botticelli’s painting The Birth of Venus, Mozart’s opera The Magic Flute, and a major part of Romantic poetry from Goethe to Coleridge and Wordsworth. It has traveled with James Cook’s ships around the world and driven several of the founding fathers of the United States of America, even making its way into the US Declaration of Independence as “Nature’s God.” The One has h
ad such an influence on the world of ideas, on the arts and humanities, that its importance as a scientific concept is often overlooked. Taken at face value though, the hypothesis that “all is One” isn’t a statement about God, spirits, or subjective mental states; it is a statement about nature, about the particles, planets, and stars out there.

  As a theoretical physicist, for the past twenty-five years I have worked to figure out how tiny particles compose the world. Particles have thrilled me since the very first time I heard about them. Yet, fascinating as they are, what truly captivated me about these particles is how they can serve as a tool to uncover the foundations of reality. “What is everything made of?” was a question that started to occupy me when I still was in high school. This fascination was what got me into physics, earning me a PhD and finally a professorship. Particles kept me going when I was struggling with math, incomprehensible language, and feelings of inferiority. And particles were the driving force of my work when, over the following decades, I published more than eighty papers in refereed journals, when I wrote a Scientific American cover feature that got reprinted next to a piece by Stephen Hawking, and when my research made it three times onto the cover of New Scientist magazine. Of course, I’m not alone in this endeavor. I’m just a modest contributor in a global enterprise. There are some ten thousand researchers all over the world, including some of the most brilliant minds on the planet, working restlessly to find out how particles ultimately constitute what we see around us.

  Now I believe we are on the wrong track.

  Don’t get me wrong. Science’s most important task is to predict and explain the outcome of experiments, observations, and events. And particle physics does that with an unrivaled accuracy. Starting with a set of equations that fits onto a coffee mug, particle physicists predict the results of their experiments with a precision that would correspond to knowing the distance between London and Berlin up to less than a millimeter. But while particle physics is still more precise than any other discipline in science, it doesn’t tell the full story. Because if we pay attention to the full story, we will see that particles do not compose the world; it is the other way around.

  Ever since the discovery of the atom, physicists adhered to the philosophy of reductionism. According to this idea, nature could be grasped in a unified understanding by decomposing everything around us into pieces made up from the same tiny constituents. According to this common narrative, everyday objects such as chairs, tables, and books are made of atoms, atoms are composed of atomic nuclei and electrons, atomic nuclei contain protons and neutrons, and protons and neutrons consist of quarks. Elementary particles such as quarks or electrons are understood as the fundamental building blocks of the universe. Over the past fifty years, to work out and concretize this view, hundreds of thousands of pages have been filled with sophisticated equations full of strange symbols. To test these ideas, gigantic particle smashers have been built, tubes many miles long and worth billions of dollars, to accelerate subatomic matter close to the speed of light, let it crash together with violent impact, and search for even smaller or as-yet undiscovered pieces. With the help of NASA and the European Space Agency, engineering marvels have been launched into space to eavesdrop on the earliest incidents in the universe to understand how the world looked when it was but a soup of hot particles.

  This philosophy has been tremendously successful, but there is a blind spot. Atoms, protons and neutrons, electrons and quarks are described by quantum mechanics. And according to quantum mechanics, it is, in general, impossible to decompose an object without losing some essential information. Particle physicists strive for a fundamental description of the universe, one that discards no information. But if we take quantum mechanics seriously, this implies that, on the most fundamental level, nature cannot be composed of constituents. The most fundamental description of the universe has to start with the universe itself.

  Like any other professional physicist, I work with quantum mechanics on a daily basis. We use quantum mechanics to calculate and predict the results of the experiments, observations, and problems that interest us, be it particle collisions in giant accelerators, scattering processes in the primordial plasma of the early universe, or the behavior of electric or magnetic fields in a solid-state lab experiment. But while we almost always adopt quantum mechanics to describe specific observations and experiments, we usually don’t apply it to the entire universe.

  This has a mind-boggling consequence. As I will argue in this book, once quantum mechanics is applied to the entire cosmos, it uncovers a three-thousand-year-old idea: that underlying everything we experience there is only one single, all-encompassing thing—that everything else we see around us is some kind of illusion.

  Admittedly, the claim that “all is One” doesn’t sound like an ingenious scientific concept. On a first glance, it sounds absurd. Just look out the window. Most of the time there will be more than one car in the street. It takes two persons (at least!) for a love affair, “two or three” believers are required to hold a Mass, and twenty-two players are needed for a proper soccer game. Ages ago, astronomers convinced us that Earth is not the only planet in the universe, and today modern cosmology knows virtually innumerable stars.

  But quantum mechanics changes everything. In quantum systems, objects get so completely and entirely merged that it is impossible to say anything at all about the properties of their constituents anymore. This phenomenon is known as “entanglement,” and while it was pointed out by Albert Einstein and collaborators some eighty years ago, it is only now getting fully appreciated. Apply entanglement to the entire universe and you end up with Heraclitus’s dogma “From all things One.”

  “Hold on,” you may object. “Quantum mechanics applies only to tiny things: atoms, elementary particles, maybe molecules. Applying it to the universe doesn’t make sense.” You will be surprised to learn that there are increasingly many good hints that this conviction is wrong. Between 1996 and 2016 alone, six Nobel Prizes were awarded for so-called macroscopic quantum phenomena. Quantum mechanics seems to apply universally, a finding whose consequences are just starting to be explored.

  You may throw up your hands and protest that such a discussion is pointless. Physics seems to work just fine without any such metaphysical pondering. Fact is, it doesn’t. At present, physics is facing a crisis that forces us to reconsider what we understand as “fundamental” in the first place. Right now, the most brilliant particle physicists and cosmologists are alienated by experimental findings of extremely unlikely coincidences that so far defy any explanation. At the same time, the quest for a theory of everything is bereaving physics of its foundational concepts, such as matter, space, and time. If these are gone, what remains?

  Quantum cosmology implies that the fundamental layer of reality is made neither of particles nor of tiny, vibrating, one-dimensional objects known as “strings,” but the universe itself—understood not as the sum of things making it up but rather as an all-encompassing unity. As I will argue, this notion that “all is One” has the potential to save the soul of science: the conviction that there is a unique, comprehensible, and fundamental reality. Once this argument holds sway, it will turn our quest for a theory of everything upside down—to build up on quantum cosmology rather than on particle physics or string theory (currently the most popular candidate for a quantum theory of gravitation). Such a concept further implies the need to understand how it is possible that we experience the world as many things if everything is “One,” after all. This is ensured by a process known as “decoherence,” which is essential to virtually any branch of modern physics. Decoherence is the agent protecting our daily-life experience from too much quantum weirdness. And it realizes the rest of Heraclitus’s tenet: “from One all things.”

  As a consequence, we will have to work out how such a notion changes our perspective on philosophy’s deepest questions—“What is matter?” “What is space?” “What is time?” “How did the universe come into being?”—and even on what religious people call “God” (since for centuries, the concept of an all-encompassing unity was identified with God). We will also have to confront why monism is not more popular, if it follows so straightforwardly from quantum mechanics. Why does it sound so bizarre to us? Where does our intuitive, deprecative reflex come from? To really understand this bias, we have to venture into the history of monism.