Existential Physics: A Scientist's Guide to Life's Biggest Questions

Existential Physics: A Scientist's Guide to Life's Biggest Questions

by Sabine Hossenfelder
Existential Physics: A Scientist's Guide to Life's Biggest Questions

Existential Physics: A Scientist's Guide to Life's Biggest Questions

by Sabine Hossenfelder


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“An informed and entertaining guide to what science can and cannot tell us.” The Wall Street Journal

“Stimulating . . . encourage[s] readers to push past well-trod assumptions […] and have fun doing so.” —Science Magazine

From renowned physicist and creator of the YouTube series “Science without the Gobbledygook,” a book that takes a no-nonsense approach to life’s biggest questions, and wrestles with what physics really says about the human condition

Not only can we not currently explain the origin of the universe, it is questionable we will ever be able to explain it. The notion that there are universes within particles, or that particles are conscious, is ascientific, as is the hypothesis that our universe is a computer simulation.  On the other hand, the idea that the universe itself is conscious is difficult to rule out entirely. 
According to Sabine Hossenfelder, it is not a coincidence that quantum entanglement and vacuum energy have become the go-to explanations of alternative healers, or that people believe their deceased grandmother is still alive because of quantum mechanics. Science and religion have the same roots, and they still tackle some of the same questions: Where do we come from? Where do we go to? How much can we know? The area of science that is closest to answering these questions is physics. Over the last century, physicists have learned a lot about which spiritual ideas are still compatible with the laws of nature. Not always, though, have they stayed on the scientific side of the debate.

In this lively, thought-provoking book, Hossenfelder takes on the biggest questions in physics: Does the past still exist? Do particles think? Was the universe made for us? Has physics ruled out free will? Will we ever have a theory of everything? She lays out how far physicists are on the way to answering these questions, where the current limits are, and what questions might well remain unanswerable forever. Her book offers a no-nonsense yet entertaining take on some of the toughest riddles in existence, and will give the reader a solid grasp on what we know—and what we don’t know.

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Product Details

ISBN-13: 9781984879455
Publisher: Penguin Publishing Group
Publication date: 08/09/2022
Pages: 272
Sales rank: 15,622
Product dimensions: 8.90(w) x 6.10(h) x 1.10(d)

About the Author

Sabine Hossenfelder is presently a research fellow at the Frankfurt Institute for Advanced Studies, Germany, and has published more than eighty research articles about the foundations of physics, including quantum gravity, physics beyond the standard model, dark matter, and quantum foundations. She has written about physics for a broad audience for fifteen years and is the creator of the popular YouTube channel “Science without the Gobbledygook.” Her writing has been published in New Scientist, Scientific American, The New York Times, and The Guardian (London). Her first book, Lost in Math: How Beauty Leads Physics Astray, appeared in 2018.

Read an Excerpt

Can I ask you something?” a young man inquired after learning that I am a physicist. “About quantum mechanics,” he added, shyly. I was all ready to debate the measurement postulate and the pitfalls of multipartite entanglement, but I was not prepared for the question that followed: “A shaman told me that my grandmother is still alive. Because of quantum mechanics. She is just not alive here and now. Is this right?”

As you can tell, I am still thinking about this. The brief answer is, it’s not totally wrong. The long answer will follow in chapter 1, but before I get to the quantum mechanics of deceased grandmothers, I want to tell you why I’m writing this book.

During more than a decade in public outreach, I noticed that phys-icists are really good at answering questions, but really bad at explain-ing why anyone should care about their answers. In some research areas, a study’s purpose reveals itself, eventually, in a marketable product. But in the foundations of physics—where I do most of my research—the primary product is knowledge. And all too often, my colleagues and I present this knowledge in ways so abstract that no one understands why we looked for it in the first place.

Not that this is specific to physics. The disconnect between experts and  non-experts  is  so  widespread  that  the  sociologist  Steve  Fuller claims that academics use incomprehensible terminology to keep insights sparse and thereby more valuable. As the American journalist and  Pulitzer  Prize  winner  Nicholas  Kristof  complained,  academics encode “insights into turgid prose” and “as a double protection against public consumption, this gobbledygook is then sometimes hidden in obscure journals.”

Case in point: People don’t care much whether quantum mechanics is predictable; they want to know whether their own behavior is predictable. They don’t care much whether black holes destroy information; they want to know what will happen to the collected infor- mation of human civilization. They don’t care much whether galactic filaments resemble neuronal networks; they want to know if the universe can think. People are people. Who’d have thought?

Of course, I want to know these things too. But somewhere along my path through academia I learned to avoid asking such questions, not to mention answering them. After all, I’m just a physicist. I’m not competent to speak about consciousness and human behavior and such.

Nevertheless,  the  young  man’s  question  drove  home  to  me  that physicists do know some things, if not about consciousness itself, then about  the  physical  laws  that  everything  in  the  universe—including you and I and your grandmother—must respect. Not all ideas about life and death and the origin of human existence are compatible with the foundations of physics. That’s knowledge we should not hide in obscure journals using incomprehensible prose.

It’s not just that this knowledge is worth sharing; keeping it to ourselves has consequences. If physicists don’t step forward and explain what physics says about the human condition, others will jump at the opportunity and abuse our cryptic terminology for the promotion of pseudoscience. It’s not a coincidence that quantum entanglement and vacuum energy are go-to explanations of alternative healers, spiritual media, and snake oil sellers. Unless you have a PhD in physics, it’shard to tell our gobbledygook from any other.

However, my aim here is not merely to expose pseudoscience forwhat it is. I also want to convey that some spiritual ideas are perfectlycompatible with modern physics, and others are, indeed, supportedby it. And why not? That physics has something to say about our connectionto the universe is not so surprising. Science and religion havethe same roots, and still today they tackle some of the same questions:Where do we come from? Where do we go to? How much can we know?

When it comes to these questions, physicists have learned a lot in the past century. Their progress makes clear that the limits of scienceare not fixed; they move as we learn more about the world. Correspondingly, some belief-based explanations that once aided sensemaking and gave comfort we now know to be just wrong. The idea, for example, that certain objects are alive because they are endowed with a special substance (Henri Bergson’s “élan vital”) was entirely compatible with scientific fact two hundred years ago. But it no longer is.

In the foundations of physics today, we deal with the laws of nature that operate on the most fundamental level. Here, too, the knowledge we gained in the past hundred years is now replacing old, belief-based explanations. One of these old explanations is the idea that consciousness requires something more than the interaction of many particles, some kind of magic fairy dust, basically, that endows certain objects with special properties. Like the élan vital, this is an outdated and useless idea that explains nothing. I will get to this in chapter 4, and in chapter 6 I’ll discuss the consequences this has for the existence of free will. Another idea ready for retirement is the belief that our universeis especially suited to the presence of life, the focus of chapter 7.

However, demarcating the current limits of science doesn’t onlydestroy  illusions;  it  also  helps  us  recognize  which  beliefs  are  still compatible  with  scientific  fact.  Such  beliefs  should  maybe  not  be called unscientific but rather ascientific, as Tim Palmer (whom we’ll meet  later)  aptly  remarked:  science  says  nothing  about  them.  One such belief is the origin of our universe. Not only can we not currently explain  it,  but  also  it  is  questionable  whether  we  will  ever  be  able to explain it. It may be one of the ways that science is fundamentally limited.  At  least  that’s  what  I  currently  believe.  The  idea  that  the universe itself is conscious, I have found to my own surprise, is difficult  to  rule  out  entirely  (chapter  8).  And  the  jury  is  still  out  on whether or not human behavior is predictable (chapter 9).

In brief, this is a book about the big questions that modern physics raises, from the question whether the present moment differs from the past, to the idea that each elementary particle may contain a universe, to the worry that the laws of nature determine our decisions. I cannot,  of  course,  offer  final  answers.  But  I  want  to  tell  you  how much scientists currently know, and also where science crosses over into mere speculation.

I  will  mostly  stick  with  established  theories  of  nature  that  are backed up by evidence. All of what I am going to say, therefore, should come with the preamble “as far as we currently know,” meaning that further scientific progress might lead to revision. In some cases, the answer to a question depends on properties of natural laws that we do not yet fully understand, like quantum measurements or the nature of space-time singularities. If so, I will point out how future research could help answer the question. Because I don’t want you to hear just my own opinion, I have added a few interviews. And at the end of the book, you’ll find a brief glossary with definitions of the most impor- tant  technical  terms.  Terms  in  the  glossary  are  marked  bold  when they first appear in the text hereafter.

Existential Physics is for those who have not forgotten to ask the big questions and are not afraid of the answers.

Table of Contents

Preface xiii

A Warning xvii

1 Does the Past Still Exist? 1

2 How Did the Universe Begin? How Will It End? 23

Other Voices #1 Is Math All There Is? An Interview with Tim Palmer 43

3 Why Doesn't Anyone Ever Get Younger? 51

4 Are You Just a Bag of Atoms? 79

Other Voices #2 Is Knowledge Predictable? An Interview with David Deutsch 95

5 Do Copies of Us Exist? 105

6 Has Physics Ruled Out Free Will? 125

Other Voices #3 Is Consciousness Computable? An Interview with Roger Penrose 143

7 Was the Universe Made for Us? 151

8 Does the Universe Think? 169

Other Voices #4 Can We Create a Universe? An Interview with Zeeya Merali 191

9 Are Humans Predictable? 199

Epilogue: What's the Purpose of Anything Anyway? 217

Acknowledgments 225

Glossary 227

Notes 231

Index 239

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