Reality Is Not What It Seems: The Journey to Quantum Gravity by Carlo Rovelli (PDF)

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“The man who makes physics sexy . . . the scientist they’re calling the next Stephen Hawking.” —The Times MagazineFrom 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.

User’s Reviews

Editorial Reviews: Review “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.”—Elle “[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 elegant and 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.”—Pasadena Star-News“Rovelli writes with elegance, clarity and charm. . . . A joy to read, as well as being an intellectual feast.”—New Statesman“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.”—Booklist “Rovelli smoothly conveys the differences between belief and proof. . . his excitement is contagious and he delights in the possibilities of human understanding.”—Publishers Weekly“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.”—Kirkus Reviews“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.”—Shelf Awareness“Rovelli draws deep physics into the light with rather greater success… He wears a broad erudition lightly, casually and clearly explaining.”—Read It Forward About the Author Carlo Rovelli is a theoretical physicist who has made significant contributions to the physics of space and time. He has worked in Italy and the United States and currently directs the quantum gravity research group of the Centre de Physique Théorique in Marseille, France. His books, including Seven Brief Lessons on Physics, The Order of Time, and Helgoland, are international bestsellers that have been translated into more than fifty languages. Excerpt. © Reprinted by permission. All rights reserved. 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. 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Reviews from Amazon users which were colected at the time this book was published on the website:

⭐I read Carlo Rovelli’s book about quantum gravity (for the first time, it will take me a few goes, at least, to get all that is in it.) He is quite a good writer and this book, like his seven lessons in physics, is clear and extremely literate (I imagine he wrote it in Italian, but the English is smooth and demotic and lucid. It is a pleasure to read, which is not the norm in books that try to explain physics to non-specialists; God help the guy who tries to read the specialist literature.After a review from Democritus to Einstein et al, he gives us three big conclusions. At the smallest level, the universe is granular, relational, and indeterminate. He makes some other amazing statements like that ‘time’ disappears at this level and that things only exist when they collide into each other (or as ‘events’ as he puts it.) I have a notion about these other statements, but I have to determine if I understand the big three first.Everything (like Democritus and Feynman told us) is made of “atoms” or actually irreducible ‘quanta.’ Each of which is a unit of stuff that cannot be further divided; matter is not infinitely divisible (NB; big point.) Eventually, you get to a tight-pack of Plank scale bits of somethingness that all fit together. They in their constellation are gravity, space, and at bottom, everything else.There is no overarching, organizing anything outside these quanta. Time is absolutely a characteristic of the situation of the observer and the variable being measured “in” or as “time;” it measures differently at different altitudes and in different circumstances of proximity to matter and because of other factors. There are times all over the place and they do not generalize. At the level of the granular quanta, it disappears as a factor entirely.The stuff of the universe is not strictly determined in terms of how things interact and the results of any given intervention in it. We can pretty much depend on certain things happening as if by cause and effect on the macro level, but on the basic level, you get all kinds of stuff going on that is not absolutely predictable based on the setting conditions. This is the quantum probability/uncertainty thing, but it has to be understood in one of two ways; either it means our tools or our theory is inadequate and we don’t understand what is going on entirely, or the way the universe works is not determined by rules associated with forces, etc., and compatible with mathematics but instead things do their own thing, which usually results in rule governed outcomes, but doesn’t always.I am here confronted with the issue of the void that keeps on giving me a problem; there is no such thing as nothing and stuff cannot move around in it. Nothing cannot function either as a nominative, nor accusative, nor prepositional object in a sentence relating to stuff that exists except insofar as it is used to designate and absence that serves no purpose (e.g. “nothing happened,” or “you know nothing,” or “it is surrounded by nothing,” none of which are statements to be taken literally.) Therefore, matter cannot be conceptualized as floating around or moving in nothing or a ‘void’ (which is either nothing something and cannot function as both.) Democritus knew this right at the start; “space” he explained both is and isn’t nothing. He was just being gnomic and communicating that his atomic theory needed more work.If that is so, and how can you say anything else and be sane? Then certain conclusions follow. The quanta, for example, that make up everything are the whole show. There is nothing else in the cosmos but them, configured as they be. They are not in nothing (the statement doesn’t mean anything.) Nor are they in ‘space’ since they are space. They are not held together by gravity because they are gravity.More to the point, they are not held together by gravity because they are not “held together” at all. Since there is only these quanta irreducible and adhesive upon each other, they relate to no other cohesive force, they just are together with nowhere else to go.That means the quanta do not move; they cannot. There would have to be some medium of environment into which they could go and there isn’t anything but they themselves. They are irreducible so they cannot split into smaller chunks to let others slither through them. Since there is nothing but them, they have no interstices; there isn’t anything else in the cosmos that could come between them. Thus, you have inseparable grains and nothing else and these grains are where they are in relation to each other, but there is no force or principle or anything else that affects them all, like time or gravity or space or motion.They are not determined by any law or cause or force because no such thing exists outside of them (I am deliberately repetitious because the notion blows my mind.) For that reason, the prediction of occurrences among them is hit or miss. This is the part the author doesn’t exactly state, but if I am following him, the cosmos works something like this: There is no Aristotelian/Newtonian ‘time’ at the level of the quanta, but they configure according to the warped, curved, four-dimensional morphology of space-time. That is to say the that way the quanta fit together is not only according to the three axes of a prism, but also in relationships of sequence within the prism’s extension. That means that the entirety of the universe, including what we call past and present and future exists with all the quanta co-existent in all parts of space-time.Should this be the state of play of the cosmos, and I believe it is both in general relativity and in Rovelli’s construction (he calls it “loop” theory to distinguish it from the feckless “string” theory he deprecates) then, there is no determinacy or any causes or effects or any changes at all; just all the bits configured exactly how they are and the positions they have relative to each other and the observer are not caused by anything but just are.So, the discoveries of things are like looking at a map of twelve inches by six inches but only being able to see it a centimeter at a time from the left-hand margin. You guess what is coming in the next centimeter(s) based on what you already have seen of the terrain on the map, but a sink-hole or an inexplicable mountain peak can turn up on the map that relates to nothing else on the landscape, it is just there. The cosmos is like that; things don’t pop in and out of existence; the quanta that are there are just the quanta that are there, the observer has inferred the quark or electron out of stuff that he saw in one part of the map, but it isn’t to be inferred as in the next slice because the (existing) configuration of space-time just isn’t like that.The notion that only events exist is basically pretty anthropomorphic if you ask me, almost solipsistic. You only measure something by looking at it, which is a kind of collision. Since you cannot talk about things you cannot measure, only measured things exist according to this view. I think we can stretch and hazard that stuff exists even when not being measured, but I think the point is precious and not all that interesting.Change is something the observer infers when he looks over the cosmos along a sequence of space-time and mistakes the irreducible quanta, each of which is a grain that extends the Plank scale in ALL FOUR dimensions, as continuous, surviving unities across time. Parmenides knew this.Goedel understood this too, which is why he said that time travel is not a silly idea. As Einstein said, all parts of the cosmos are always available to the observer. They are all co-existent, which means they are all made of different stuff. Continuity is mental construction of the imaginative observer. (You can ask Descartes how the observer arises from these quanta and you will get an answer no more satisfactory than one I can give you, but consciousness is no more extraordinary than any of the rest of this stuff.)If I am right, and this is what the professor is saying, then what a great book since it made something quite clear to me that I had not understood hitherto.If I misunderstood it all (like I usually do) then I cannot blame him, and I still really enjoyed the book.

⭐Rovelli’s book is strongest when it considers the history of science. The author has an understanding of these things the way only a European can. Ptolemy’s Almagest, Archimedes’ The Sand Reckoner, Alice Calaprice’s childrens’ letters to Einstein, J. A. Wheeler talking on web of stories — it’s great stuff (mostly now accessible online). But where Reality Is Not What It Seems falls down is in the theory. Physicists are fond of describing their theories as beautiful, powerful, and elegant, but many of these are really ugly, weak, and awkward. If quantum gravity were a stock pick, I’m not buying it. Besides the history of science stuff, and some poetic writing, I can’t understand why so many reviewers were so taken in by this simplistic book. Scientific authors can have two main goals when writing a book like this one: secondarily, to make some extra pocket cash if the book turns out to be a best seller (as this one did), but primarily to implant their idea into the public consciousness that this is good science worth the funding. Perhaps now there will be more junkets of physicists to Italy.Lee Smolin’s The Trouble With Physics was the first major work to criticize string theory. This was particularly significant because Smolin himself admitted to being a former string theorist. But by the end of that book, Smolin revealed that he had now abandoned string theory for something new that he called quantum gravity. So, now we know what has happened to some of these chagrined string theorists: they emigrated to quantum gravity.Quantum gravity has many of the same problems as string theory. It appears in retrospect reasonably ridiculous now that anyone would ever think that the fundamental components of the universe are vibrating strings. Maybe string theorists were doing something listening to their stereos at a time when rock and roll was the biggest thing going, or maybe that would be making them sound cooler than they actually were. But it may make even less sense now to say that the fundamental component of the universe is timeless spinfoam. Quantum gravity begins with the credibly interesting idea that the world might be quantized and discrete rather than infinitesimally divisible and continuous. The intuition for this may be the relative success of digital signal processing over analog signal processing in electrical engineering through the quantization of digital information, and the widespread use of digital computers that ensued, or from real analysis in number theory and the mathematics of Cantor. But the problems begin as soon as the quantum gravity theorists step beyond the original idea and begin trying to do something with the equations. Rovelli makes a little graph with nodes and links, and calls them spin networks (never mind that what spin really is was never adequately explained by Dirac, who sidestepped the question of what may actually be spinning, and how to make the speed of the spin consistent as being under the speed of light, by just labeling the spin as intrinsic), and then makes loops between the nodes that he calls gravity, but this doesn’t take us far.Consider the Planck length — ten to the negative thirty-third centimeters. Rovelli says this is the basic thing, it defines the smallest indivisible unit of space, and he explains how it arises out of the uncertainty principle of Heisenberg. But this sounds in the end like numerology with exponents. It could be a theoretical limit or there could be things that are smaller. The uncertainty principle could merely be a statement of a measurement approximation at a certain spatial dimension of reality if you happen to be trying to measure something by bouncing a photon against it. Perhaps there will be some future way of measuring that is more minimally invasive, but the uncertainty principle is not necessarily inconsistent with there being things that are smaller than the Planck length.Consider Rovelli’s argument in favor of quantum gravity as explaining the Big Bang. There are several problems with this. One is a central problem with the Big Bang itself that physicists don’t ever really logically give due consideration. If the initial state of the universe is what physicists appear to be saying it is, with all this matter present in one place ready to explode, then why wasn’t the universe initially a black hole? There are all kinds of problems as to why the universe would be in the initial state that they say it was in ready to explode, and one would have to at least completely buy into an iffy spontaneous symmetry breaking to resolve any of them, but this is another big problem. Rovelli distracts us from this with an interesting idea of gravitational time dilation in the black hole during which occurs a Big Bounce. If the universe began somehow from some prior universe’s black hole in a gravitational Big Crunch, Rovelli then says the Big Bounce occurs in slow motion over many billions of years by our temporal frame of reference due to the gravitational time dilation. However, the problem here is that there is no explanation as to why any Big Bounce — which is presumably going to be relatively weak because it is only due to quantum effects — is in any way going to be strong enough to overcome the gravity of a black hole to begin a new universe again. Never mind that all the evidence is that the universe is only expanding, and will never reverse into a Big Crunch. Moreover, let’s assume that it is possible that our universe began from a black hole of a prior universe as an exploding Big Bounce. Then the universe would be getting smaller every time this happens because there would be less matter in it. Okay, now. Let’s try to add Penrose’s Conformal Cyclic Cosmology. Then the universe begins again with everything scaled down to a smaller size, with all the subatomic particles being regenerated at a conformally smaller spatial dimension of scale in a new Big Bang. But we would all like to know how this ‘phase transition’ to a new universe can ever actually happen, why whatever laws of physics would necessitate that the ratios of the sizes of the particles and the physical constants and the forces would be replicated at a smaller scale again in a new universe. String theory’s initial motivation was to address this issue, but it never made any headway, instead getting bogged down in the mathematics, and the program was forgotten. All of our notions of what might constitute a Big Bang are tied up in our observations of chemical explosions, or in the historicity of physics, where the development of the atomic bomb in the same decades as the development of the idea of the Big Bang fused and confused these ideas together.There is a role for quantum gravity, but Rovelli’s isn’t it. There is quantum gravity in trying to understand what is happening to the soup of atomic nuclei in a neutron star where all the empty space is compressed out of the electron orbitals of the atom, or maybe in a quark soup at the core of a black hole where all the empty space is compressed out of the distances between the protons and neutrons of the atomic nucleus. There are actually some concepts in astrophysics called spaghettification and nuclear pasta that describe some of this, where neutron stars have a ‘gnocchi phase’, a ‘lasagna phase’, a ‘bucatini phase’, and an ‘antispaghetti phase’. In the words of Dave Barry, “I’m not making this up!” Perhaps there is an even denser state, a super black hole if you will, where all the empty space is compressed out of the quarks, leaving a soup of whatever the components of quarks are. It is a fact that the universe as we now know it is almost all empty space at every dimensional scale — this is true of the space in the solar system, between the stars, or between the galaxies. I read somewhere that an atomic nucleus is like a twenty-five cent piece on the fifty yard line of a football stadium that is an atom, and that protons and neutrons are similarly proportioned with mostly empty space between the quarks.Consider the sum of over histories. Rovelli says that quantum gravity resolves this problem because everything is now discrete and there are no infinities. However, there isn’t any evidence presented to show that physicists have actually made any progress with this. Yes, you could see how conceptually making things discrete might resolve divergences of a sum over histories, but the book is too thin on the ground to show that quantum gravity actually does this. The sum over histories has been a royal pain to physicists for some time now, and maybe the problem is somewhere in the application of the sum over histories itself, which was not very well thought out from its beginning. (Feynmann, who developed this theory, was maybe never a really deeply logical thinker.)Rovelli almost gets it right in my opinion when he begins to talk at the end about information theory. But he uses the thermodynamic entropy equation of phase space instead of the information entropy equation of Shannon, and gets everything confused and backwards when he puts thermodynamics — historically reflected by the industrial revolution — superior to time, and so has to conclude that time doesn’t really exist. (Maybe we should blame this on Hawking’s theory of the thermodynamic entropy of black holes.)The book’s provocative title shouldn’t let it hook you in. Sometimes reality is just what it seems to be if you are looking at it carefully. Sometimes it’s not. But for every school of the ancient world with a Democritus, there were likely hundreds that believed that the fundamental elements of the universe were turtles, or elephants, or string music.

⭐I read a LOT of books on science for the non-scientist by some very effective communicators, but this is easily the most beautifully written book that I have read on any subject for a long while. I don’t know if this is a translation from Italian or if Prof. Rovelli wrote it in English, but either way this is not only a very clear and interesting explanation of some very complex physics, but the language used is absolutely wonderful. Enchanting, which is not a word I use ordinarily…

⭐I like Carlo Rovelli’s writing, so I’m a bit biased to start with. However, in my defense he does write extremely well and conveys difficult concepts with startling clarity In this book Carlo takes us on the journey to Quantum Loop Gravity, a concept which attempts to join General Relativity with Quantum Electrodynamics, without anybody disappearing in a puff of purple smoke leaving nothing but their boots. It isn’t entirely successful. Starting with the Greeks we look and some general philosophical aspects so everybody is nicely grounded in 2,000 years ago, and nothing much changes until Newton. At this point everybody is happy, nice deterministic universe, off to church on Sundays in the sure knowledge it won’t make any difference. Then along came Max Planck, Schrödinger (him of the missing pet cat) and Heisenberg, this little gang of trouble makers caused a lot of uncertainty. But after a while a bunch of clever people, notably Julian Schwinger, Richard Feynman and Freeman Dyson, (nothing to do with vacuum cleaners), had a good look and decided we could explain almost everything by looking at the interaction of fields. Carlo runs with this idea, going to back to the by now rather simplistic ideas of Newton (to be fair, he saw the elephant in the room *and* measured it’s gravitational force!) and begins to put forward an idea of how these fields could explain gravity without the universe doing a credible impersonation of an Ouzelum bird. The end of the book is quite complicated, but well worth it for the simple reason you are still reading at that point! Also, as a history of physics in a nutshell, it shines for it’s brevity but without loosing important detail. Every paragraph is worth reading twice. I digress. It’s a damn good read, worth bunging a few groats Carlos way, you won’t be sorry. That good enough?

⭐It was a great walk through history, from the Greeks at Miletus, to the present day search for what is gravity. This walk through history is valuable, because it shows how scientific knowledge develops, and how hypotheses are subsequently validated through experiment, or shown to be unhelpful. It also shows how people depend on their predecessors work to make progress, and refine knowledge. At each stage in the process, theories produce something which gives a basis for practical developments. A future scientist then refines that nderstanding, which may reveal anomalies in the previous theory, or description of the world. This doesn’t negate the previous work, but adds to understanding, and may then allow the development of new practical applications. It’s a great little book, and easy to follow, even though the few mathematical formulae quoted will be a foreign language for most people.

⭐This book starts off by going back to the ancient Greeks – I think this is a mistake. Nobody wanting to read about Quantum Gravity is interested in the ideas of the ancient Greeks. At times it’s obvious that it has been translated from Italian. It’s only a thin book but by half way through I was bored with it.

⭐I bought this book a month ago and have been reading a little bit every day. Being a ‘non scientist’ and someone who never achieved an O Level in Maths or Physics I am always a bit nervous that I will find this type of book too difficult but I didn’t need to worry. It is really interesting and the author presents the information in a straightforward way that makes you want to keep reading. I ration myself to a section every day so I can absorb what I am reading but it is really hard to put down. Having completed the book I am seriously in awe of the author – thank you so much for presenting so much information in a way that a ‘lay person’ like myself can understand.

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