“The man who makes physics sexy . . . the scientist they’re calling the next Stephen Hawking.” —
The Times Magazine
From the New York Times–bestselling author of Seven Brief Lessons on Physics, The Order of Time, and the forthcoming Helgoland, a closer look at the mind-bending nature of the universe.
What are the elementary ingredients of the world? Do time and space exist? And what exactly is reality? In elegant and accessible prose, theoretical physicist Carlo Rovelli leads us on a wondrous journey from Democritus to Einstein, from Michael Faraday to gravitational waves, 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 deeper explanations of the theories he introduced so concisely in
Seven Brief Lessons on Physics. Rovelli invites us to imagine a marvelous world where space breaks up into tiny grains, time disappears at the smallest scales, and black holes are waiting to explode—a vast universe still largely undiscovered.
“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.”
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
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.”
“Rovelli writes with elegance, clarity and charm. . . . A joy to read, as well as being an intellectual feast.”
“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.”
“Rovelli smoothly conveys the differences between belief and proof. . . his excitement is contagious and he delights in the possibilities of human understanding.”—
“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.”—
“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.”
“Rovelli draws deep physics into the light with rather greater success... He wears a broad erudition lightly, casually and clearly explaining.”
—Read It Forward
Carlo Rovelli, an Italian theoretical physicist, is the head of the Quantum Gravity group at the Centre de Physique Théorique of Aix-Marseille University. He is one of the founders of the loop quantum gravity theory and the author of
Seven Brief Lessons on Physics, an international bestseller translated into over forty languages, and the forthcoming
The Order of Time. Rovelli lives in Marseille, France.
Walking Along the Shore
We are obsessed with ourselves. We study
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.