Sabine Hossenfelder - Existential Physics: A Scientists Guide to Lifes Biggest Questions

Lost in Math: How Beauty Leads Physics Astray

Experimental Search for Quantum Gravity (editor)

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, its 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 Im writing this book.

During more than a decade in public outreach, I noticed that physicists are really good at answering questions, but really bad at explaining why anyone should care about their answers. In some research areas, a studys purpose reveals itself, eventually, in a marketable product. But in the foundations of physicswhere I do most of my researchthe 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 dont care much whether quantum mechanics is predictable; they want to know whether their own behavior is predictable. They dont care much whether black holes destroy information; they want to know what will happen to the collected information of human civilization. They dont care much whether galactic filaments resemble neuronal networks; they want to know if the universe can think. People are people. Whod 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, Im just a physicist. Im not competent to speak about consciousness and human behavior and such.

Nevertheless, the young mans 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 universeincluding you and I and your grandmothermust respect. Not all ideas about life and death and the origin of human existence are compatible with the foundations of physics. Thats knowledge we should not hide in obscure journals using incomprehensible prose.

Its not just that this knowledge is worth sharing; keeping it to ourselves has consequences. If physicists dont 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. Its 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, its hard to tell our gobbledygook from any other.

However, my aim here is not merely to expose pseudoscience for what it is. I also want to convey that some spiritual ideas are perfectly compatible with modern physics, and others are, indeed, supported by it. And why not? That physics has something to say about our connection to the universe is not so surprising. Science and religion have the 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 science are not fixed; they move as we learn more about the world. Correspondingly, some belief-based explanations that once aided sense-making 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 Bergsons lan 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 lan vital, this is an outdated and useless idea that explains nothing. I will get to this in chapter 4, and in chapter 6 Ill discuss the consequences this has for the existence of free will. Another idea ready for retirement is the belief that our universe is especially suited to the presence of life, the focus of chapter 7.

However, demarcating the current limits of science doesnt only destroy illusions; it also helps us recognize which beliefs are still compatible with scientific fact. Such beliefs should maybe not be called