Reality is not what it seems The journey to quantum gravity

Review by New York Times Review

MAKING THEORETICAL PHYSICS accessible to the lay reader is no easy feat. The best popular science books welcome the novice while engaging and informing the more scientifically savvy. Compounding the author's challenge is the need to distinguish between speculation, ideas that might be verified in the future, and what is just fanciful thinking. In "Reality Is Not What It Seems: The Journey to Quantum Gravity," first published in Italy in 2014, the physicist Carlo Rovelli explains how he thinks about physics and his research on loop quantum gravity. He covers important ideas and developments, and readers with a basic curiosity about modern physics will find much to pique their interest. The book tours many of the crowd-pleasers of modern physics literature - quantum mechanics and general relativity, attempts at creating theories of quantum gravity and even time - as well as more speculative quantum gravity ideas. It is peppered with the usual names: Einstein, Newton , Plato , Aristotle, Democritus, Galileo, Dante and Lucretius. Rovelli explains that he wrote "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." This latest offering will attract readers to many important and relevant physics developments, some of which Rovelli presented in his earlier book, "Seven Brief Lessons on Physics." He nicely conveys the magnificence of the changes in physicists' worldview that have emerged in the last century as well as ideas that motivate his more recent research. However, Rovelli takes on some challenging issues - and reality is not always the way that he sees it. The science as presented isn't always correct, and interpretations are misleadingly presented as facts. Explaining quantum mechanics, Rovelli says: "Electrons don't always exist. They exist when they interact. They materialize in a place when they collide with something else. The 'quantum leaps' from one orbit to another constitute their way of being real: An electron is a combination of leaps from one interaction to another." Stocks may not achieve a precise value until they are traded, but that doesn't mean we can't approximate their worth until they change hands. Similarly electrons might not have definite properties, but they do exist. It's true that the electron doesn't exist as a classical object with definite position until the position is measured. But something was there - which physicists use a wave function to describe. Even well-established science isn't always correct. For instance, the ratio of the size of the universe to the Planck scale (perhaps the smallest-size scale) is 1060 not 10120. It's not a typo. "This is the order of magnitude of the universe we have indirect access to," Rovelli writes. "It is around 10120 times greater than the Planck length, a number of times that is given by a one followed by 120 zeros. Between the Planck scale and the cosmological one, then, there is the mind-blowing separation of 120 orders of magnitude. Huge." Rovelli's claims in his own research field - that "a gigantic rebound known as a Big Bounce instead of Big Bang" is what "seems to emerge from the equations of loop quantum gravity, when they are applied to the expansion of the universe" - aren't necessarily any better. The theory isn't sufficiently well developed to do the necessary calculations to establish such a claim and, furthermore, the theory fails to produce some essential ingredients of what we do know. All of this may seem nitpicky, but such errors and overstatements are concerning in a popular science book. At a time when people can disagree about the sizes of the crowds before their eyes, it should come as no surprise that they can disagree on scientific theories that are even harder to discern. But in today's toxic political climate, when deliberate ambiguity and "alternative facts" stand in for knowledge, it's never been more important for scientists and academics to be accurate in their presentation of what we know. I admire Rovelli's goals, but they would be better served if he were more careful. "Reality Is Not What It Seems" is "a travel book," Rovelli writes, "describing one of the most spectacular journeys that humanity has taken: a journey out of our limited and parochial views of reality, toward an increasingly vast understanding of things. A magical journey out of our common-sense view of things, far from complete." His many historical and philosophical digressions can be amusing, and anyone unfamiliar with the characters in the book will find much to enjoy here. Yet oversimplifications devalue these references too. It's a leap to say "the connection between problems posed by the scientists of antiquity and solutions found by Einstein and quantum gravity is, as we shall see, surprisingly close." Wedging old ideas into new thinking is analogous to equating thousand-dollar couture adorned with beads and feathers and then marketed as "tribal fashion" to homespun clothing with true cultural and historical relevance. Ideas about relativity or gravity in ancient times weren't the same as Einstein's theory. Art (and science) are in the details. Either elementary matter is extended or it is not. The universe existed forever, or it had a beginning. Atoms of old aren't the atoms of today. Egg and flour are not a soufflé. Without the appropriate care, it all just collapses. Science provides a systematic method of building up from the measured and tested ideas and equations we agree on to realms that we don't yet understand because measurements are not yet sufficiently precise or are too far outside our limited perspective. If presented correctly, the scientific view of reality clarifies many of the spurious controversies we often encounter by separating what we know from what we are still trying to understand. The beauty of physics lies in its precise statements, and that is what is essential to convey. Many readers won't have the background required to distinguish fact from speculation. Words can turn equations into poetry, but elegant language shouldn't come at the expense of understanding. Rovelli isn't the first author guilty of such romanticizing, and I don't want to take him alone to task. But when deceptively fluid science writing permits misleading interpretations to seep in, I fear that the floodgates open to more dangerous misinformation. A great chef once told me that many of his most talented colleagues had at one point been smokers and, as a result, tend to use a bit too much salt. This turns out in any case to be what many palates prefer. "Reality Is Not What It Seems" is a bit oversalted in an intellectual way. It isn't junk food. It's more akin to P F. Chang's. Everything on the menu looks enticing and perhaps even a bit exotic, and the service and ambience are pretty good. But the end product, though tasty, isn't always as nourishing and sustaining as one might have hoped. This is 'a travel book,' Rovelli writes, 'a journey out of our limited . . . views of reality.' LISA RANDALL is a professor of theoretical particle physics at Harvard University and the author of "Dark Matter and the Dinosaurs: The Astounding Interconnectedness of the Universe."

Copyright (c) The New York Times Company [January 1, 2017]

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Review by Booklist Review

A book on scientific thinking from 450 BCE through today, encompassing major theories (one of them, loop quantum gravity theory, developed by the author) and thinkers, sounds like work. This one, however, challenges theoretical physicist Richard Feynman's writings in providing clear explanations for even Einstein's theories. 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. Young adult patrons who are completing biography reports will appreciate the look at little-covered aspects of scientists' lives. For example, while most Einstein biographies focus on his professional life, Rovelli explains that little Albert was fascinated by his father's job building power stations, with the workings of electrical fields inspiring parts of Einstein Jr.'s famous theories. Though this translation from Italian is marred by some grammar mistakes and missing words, it is a worthwhile purchase, especially where readers enjoyed Rovelli's successful Seven Brief Lessons on Physics (2014).--Verma, Henrietta Copyright 2016 Booklist

From Booklist, Copyright (c) American Library Association. Used with permission.

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Review by Publisher's Weekly Review

In his latest explanatory work, Rovelli (Seven Brief Lessons on Physics), a theoretical physicist and proponent of loop quantum gravity, sets himself the difficult task of attempting to clarify for laypeople the most recent scientific theories about the nature of the universe. He begins with historical lessons, going back to philosophical questions posed in Western antiquity. Rovelli races forward through the work of Newton, Faraday, and Maxwell to get to how Einstein refined and added to the field theories of electromagnetism. One of the book's strengths is the picture Rovelli develops of how scientists build on the work of others. But the bulk of the book focuses on evaluating the perplexing nature of space and time, which, as they are commonly understood, appear to be little more than convenient constructs. "Space is created by the interaction of individual quanta of gravity," Rovelli writes, while "the world is made entirely made from quantum fields." The difficulty of understanding this aside, Rovelli smoothly conveys the differences between belief and proof, and concludes with a lovely chapter on being ignorant and eager for the next discovery. Rovelli's work is challenging, but his excitement is contagious and he delights in the possibilities of human understanding. (Feb.) © Copyright PWxyz, LLC. All rights reserved.

(c) Copyright PWxyz, LLC. All rights reserved

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Review by Library Journal Review

In this beautifully written book, Rovelli (director, the quantum gravity group, Centre de Physique Théorique, Aix-Marseille Université; Seven Brief Lessons on Physics) describes the state of theoretical physics today and how we got there. He starts with the ancient Greek philosophers, some of whom noted that assuming space to be infinitely divisible leads to logical paradoxes and a few who proposed that the world was composed of indivisible small pieces that are constantly in motion. Throughout, the author refers back to the ancients and explains how their intuition was markedly prescient. Today our model of reality has two parts: quantum mechanics and general relativity. However, singularities arise when, as with black holes, we allow an object with mass to shrink to a point, which brings the two theories into conflict. To eliminate the singularities, the author proposes a theory of quantum gravity, which assumes that space itself is composed of a huge number of incredibly small quanta-not an infinite number of infinitesimal points. With full disclosure, Rovelli tells us that this is a work in progress and that many disagree with him. But he makes a convincing argument for his position and includes a lovely explanation of why time itself may be an illusion. Verdict This is not an easy read, but it is worth the effort. It includes neither experimental support nor mathematical formulas; an excellent choice for the intelligent layperson.-Harold D. Shane, Mathematics Emeritus, Baruch Coll., CUNY © Copyright 2016. Library Journals LLC, a wholly owned subsidiary of Media Source, Inc. No redistribution permitted.

(c) Copyright Library Journals LLC, a wholly owned subsidiary of Media Source, Inc. No redistribution permitted.

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Review by Kirkus Book Review

When theoretical physicist Rovelli's Seven Lessons in Physics became an international bestseller in 2015, his Italian publisher proceeded to translate this, his previous book, which turns out to be an admirable addition to a popular genre: explaining what scientists know about the universe and their struggles to learn more.Most authors in this subject begin with the Greeks and make their ways through Newton, Galileo, and Maxwell to the glories of Einstein's relativity and the founders of quantum mechanics. In good hands, this is a smooth ride, and Rovellithe head of the Quantum Gravity group at Aix-Marseille University and one of the founders of the loop quantum gravity theoryis good. Then the story gets tougher. Relativity and quantum mechanics are incompatible, and physicists today are trying to combine them to produce a single, satisfying theory of everything. This requires complex ideas that dissect everything, space-time included, to a very, very tiny state where their quintessence emerges. Rovelli delivers a respectful nod to string theory, but he belongs to the rival school of quantum loop gravity, the central feature of which is that space itself is quantized. "The central prediction of loop theory isthat space is not a continuum," writes the author, "it is not divisible ad infinitum, it is formed of atoms of space,' a billion billion times smaller than the smallest of atomic nuclei." Got it? For some readers, the narrative will be a slog. Science buffs will admire Rovelli's lucid writing, but at some point, many will realize that they no longer understand. 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. Copyright Kirkus Reviews, used with permission.

Copyright (c) Kirkus Reviews, used with permission.

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INTRODUCTION Walking Along the Shore We are obsessed with ourselves. We study our history, our psychology, our philosophy, 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. Excerpted from Reality Is Not What It Seems: The Journey to Quantum Gravity by Carlo Rovelli All rights reserved by the original copyright owners. Excerpts are provided for display purposes only and may not be reproduced, reprinted or distributed without the written permission of the publisher.

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