Amazing theories about something we really don't know much about. Rovelli first deconstructs our current suppositions about time, and there are so many. Then he explores a world without time as we know it. Then he reconstructs a concept of time that we can live with. Truly mind blowing, and there is only one formula in the whole shebang. I listened to it (read by Benedict Cumberbach) and then bought a hardback copy for further readings. ( )

Time is a human experience, it does not exist independently in the physical description of the world. This is a difficult but beautiful book, I read parts of it two or three times. Rovelli destroys the naive concept of time as a physical variable, by reference to the special and general theories of relativity, that show the duration of events vary depending on where the events occur in a gravitational field. His reconstruction of what time is for us starts with entropy, and he argues that the apparent flow of time is due to the low entropy of the primordial universe. He then locates time in our memory of our experiences, the story of our lives. The chapters open with verses from Horace's Odes, and Rovelli quotes from Hindu myths, discusses Husserl and Heidegger, recommends Proust as an expert in the science of memory. The penultimate chapter has a summary of the arguments of the rest of the book, and the last chapter is a reflection on the fear of death. p 142 "It is memory that solders together the processes, scattered across time, of which we are made. In this sense we exist in time. It is for this reason that I am the same person today that I was yesterday" ( )

Terrific read! Existential, deeply humane, challenging. A must re-read every year ( )

Fisica Quântica com um caldinho de filosofia.

O físico italiano, Carlo Rovelli, sucintamente, em pouco mais de cem páginas, abre um parênteses necessário para a compreensão do Tempo para além daquilo que vislumbramos como o “Nosso-Tempo”, a fonte inesgotável das nossas vertigens e do nosso mal-estar, que "contribuiu para construir catedrais de filosofia mais do que fizeram a lógica e a razão".

O Tempo-Uno é desconstruído ao longo do livro; com bastante experimentação, mas também com bastante provas, ele demonstra que o nosso tempo não é o mesmo tempo que rege ou regeu a gramática elemental do universo, o nosso tempo é uma aproximação de uma aproximação, e as portas para uma compreensão e percepção mais completa ainda estão abertas.

A estrutura do livro pelo próprio Carlo (a ordem é dele)

O presente comum a todo o universo não existe (capítulo 3).

A diferença entre passado e futuro não está nas equações elementares que governam os eventos do mundo (capítulo 2).

Quanto mais próximos estamos de uma massa (capítulo 1), ou nos movemos velozmente (capítulo 3), mais o tempo desacelera: não existe uma duração única entre dois eventos, há muitas durações possíveis.

Se deixamos de lado os efeitos quânticos, tempo e espaço são aspectos deuma grande gelatina móvel na qual estamos imersos (capítulo 4).

Na gramática elementar do mundo não existem nem espaço nem tempo: apenas processos que transformam quantidades físicas umas nas outras, cujas probabilidades e relações podemos calcular (capítulo 5).

Não existe variável “tempo” especial, não existe diferença entre passado e futuro, não existe espaço-tempo (Segunda Parte).

Nessas equações, as variáveis evoluem uma em relação à outra (capítulo 8). Não é um mundo “estático”, nem um “universo em bloco” onde a mudança é ilusória (capítulo 7); ao contrário, é um mundo de eventos e não de coisas (capítulo 6).

A viagem de volta foi o esforço de compreender como pode surgir (capítulo 9) a nossa sensação do tempo a partir deste mundo sem tempo.

A ignorância daí decorrente determina a existência de uma variável particular, o tempo térmico (capítulo 9), e de uma entropia quauantifica a nossa incerteza.

Assim, a orientação do tempo é real, mas perspéctica (capítulo 10): a entropia do mundo em relação a nós aumenta com o nosso tempo térmico. emos um acontecer de coisas ordenado nesta variável, que chamamos simplesmente de “tempo”; e o aumento da entropia distingue, para nós, o passado do futuro e conduz o desenvolvimento do cosmos. Determina a existência de vestígios, restos e memórias do passado (capítulo 11).

Cada um de nós é unitário porque reflete o mundo, porque constrói para si uma imagem de entidades unitárias ao interagir com seus semelhantes, e porque é uma perspectiva sobre o mundo unificada pela memória (capítulo 12).

A variável “tempo” é uma das tantas variáveis que descrevem o mundo. É uma das variáveis do campo gravitacional (capítulo 4): em nossa escala, não nos damos conta de suas flutuações quânticas (capítulo 5), portanto podemos pensá-lo como determinado: o molusco einsteiniano; em nossa escala, os batimentos do molusco são pequenos, podemos negligenciá-los. Assim, é possível pensá-lo como uma mesa rígida. Essa mesa tem direções, que chamamos de espaço, e a direção ao longo da qual a entropia aumenta, que chamamos de tempo. Na vida cotidiana, movimentamo-nos a velocidades pequenas em relação à velocidade da luz e, portanto, não vemos as discrepâncias entre os tempos próprios distintos de relógios distintos, e as diferenças de velocidade em que o tempo flui a distâncias diferentes de uma massa são pequenas demais para ser percebidas. No final, portanto, em vez de muitos tempos possíveis, podemos falar de um único tempo: o tempo da nossa experiência, uniforme, universal e ordenado.

"Mas o nosso pensamento não é apenas presa da própria fraqueza, ele também é ainda mais da própria gramática. Bastam alguns séculos para que o mundo mude: de diabinhos, anjos e bruxas passa a ser povoado por átomos e ondas eletromagnéticas. Bastam alguns gramas de cogumelos, para que toda a realidade se dilua diante dos nossos olhos e se reorganize numa forma surpreendentemente diferente. Basta passar algumas semanas tentando se comunicar com uma amiga que tenha tido um episódio de esquizoide sério, para se dar conta de que o delírio é um grande equipamento de teatro capaz de organizar o mundo, e que é difícil encontrar argumentos para distingui-lo dos grandes delírios coletivos que são o fundamento da nossa vida social e espiritual e da nossa compreensão do mundo. Exceto, talvez, pela solidão e pela fragilidade de quem se afasta da ordem comum…3 A visão da realidade é o delírio coletivo que organizamos, evoluiu e se mostrou bastante eficaz para nos trazer ao menos até aqui. Os instrumentos que encontramos para geri-lo e preservá-lo foram muitos, e a razão se mostrou um dos melhores. É preciosa.

Mas é um instrumento, uma ferramenta. Que usamos para manusear uma matéria feita de fogo e gelo; de algo que percebemos como emoções vivas e ardentes, que são a essência de nós mesmos. Elas nos levam, nos arrastam, e nós as revestimos de belas palavras. Elas nos fazem agir. E alguma coisa delas sempre escapa à ordem dos nossos discursos, porque sabemos que no fundo toda tentativa de organizar sempre deixa algo de fora.

E acredito que a vida, esta breve vida, é apenas isto: o grito contínuo dessas emoções, que nos arrasta, que às vezes tentamos calar em nome de um Deus, de uma fé política, de um rito que nos garanta que no fim tudo estará em ordem, numgrande, enorme, amor, e o grito é belo e resplandecente. Às vezes é sofrimento. Às vezes é canto.

E o canto, como observou Agostinho, é a consciência do tempo. É o tempo. É o hino dos Vedas que é, ele mesmo, o desabrochar do tempo. No Benedictus da Missa Solemnis de Beethoven, o canto do violino é pura beleza, puro desespero, pura felicidade. Ficamos presos a ele, segurando o fôlego, sentindo misteriosamente que esta é a fonte do sentido. Esta é a fonte do tempo.

Depois o canto se atenua, se aplaca. “Rompe-se o cordão de prata, se despedaça o candeeiro de ouro, o cântaro quebra na fonte, e a roldana cai no poço, o pó retorna para a terra.” E tudo bem ser assim. Podemos fechar os olhos, descansar. E tudo isso me parece doce e belo. Isso é o tempo."

( )

Carlo Rovelli’s (Theoretical physicist and founder of Quantum Loop Gravity) philosophical and existential little treatise on Time (relative, absolute, or lack thereof). Paradoxical—provokes both the mind and the spirit. ( )

Me gustó, para lo difícil del tema, bastante claro. ( )

An elegant plain language explanation of relativity and quantum theory, A bit of speculative South Asian metaphysics is thrown in, but fails to explain anything. ( )

Before reading this book, I had a naive and simplistic view of time, but this book made me realize both how wrong I was and how complex the whole issue of time really is. I read it fascinated by the insights about the true meaning of “time,” the puzzlement felt by physicists as they seek a deeper understanding of it, and the coveralls complexity of understanding time and breaking it down to its components parts. It’s the smallest possible level.
The concepts covered in the book are complex, technically detailed and require a lot of either background understanding or details explanation. The author offers the needed explanations in ways even ignorant people like me can understand.
This is not an easy read in terms of its content-the concepts are complex-but the author has made it seem easy to read through his careful, direct style.
I know a lot more now than I did before reading it and I feel good about what I have learned. ( )

Mind blown. ( )

This book by Carlo Rovelli is excellent and prompts you to think deeply about the concept of time.

It's an eminently readable book, and Carlo Rovelli's style is fluid and poetic.

I enjoyed the book tremendously. The last chapter, which is more philosophical than the others, is magnificent. It is a perfect way to end the book. ( )

I was reading this for the science and was disappointed. There is a lot of philosophizing here, chapters and chapters of it. ( )

I'm happy that I chose to listen to this rather than read it. At times it is so complex, so dense, that I would have been tempted to put a book down only to collect dust. Listening to the book, wonderfully read by the ubiquitous Benedict Cumberbatch, I could listen to those difficult passages, and move on, whether I fully understood or not. Perhaps I will revisit this book when the concepts of entropy and quanta are easier for me to grasp, if that ever occurs. My lack of comprehension in no way diminishes my admiration for this book and it's author, who manages to synthesize philosophy over millennia with recent scientific theory. This is a book that made me reconsider things that I had always believed fixed, with the newfound understanding that they are not. ( )

Physics, Metaphysics, and Poetry. I read the Audible version of this while driving to my hometown in another State (a solid book for such a mid-distance, 6 ish hr drive) and thus had the unique pleasure of having Alan Turing himself (as played in The Imitation Game and read here by Benedict Cumberbatch) lecture me on theoretical physics, metaphysics, philosophy, and poetry. If you're looking for a more concrete look at the exact theoretical physics at hand... this isn't the book you're going to want to pick up. If you're looking for more of an easy-read, high-level, pop science level look at whether or not time exists... this is a very good book from that perspective. And indeed, ultimately the text is all about perspective. At the most distinct levels, time simply does not exist, according to Rovelli. And yet obviously we humans experience time. So how can these two prior statements be resolved? Read this book for Rovelli's solid examination into the question and attempt at resolving this seeming paradox. Very much recommended. Particularly the Audible. :) ( )

A beautiful treatise on time. Though Carlo's usage of flowery language at times disrupts from his actual point and purpose, the message is still clear through it. Entropy = time. Time is nothing more than entropy, and entropy is the heat of change. That basically is for the full sum of the book. There is a few more digressions and topics than this, but the main, this is what it boils down.

He does a very good job of explaining it though. It is very thorough, and he does talk about a lot of other topics and ideas regarding time. Overall its a very intriguing and interesting book filled with lots of ideas. There just happens to also be a lot of extraneous things, not needed. Though they add to the book as a whole as a person who enjoys literature, for the more scientific bent, this might be a bit of a problem. ( )

An elegant and surprisingly readable discussion of the nature of time and whether it actually exists aside from the basics of human nature and the stubborn brain’s constant production of memory and anticipation. ( )

Take two. Time has swallowed my review. My first one anyway.

I wish I could take back the time, do it over, but entropy hit GR (or at least my internet connection) and something less than the total heat-death of the universe made me realign my perceptions of reality and time.

Oh, wait. That was this book!

Half historical science, some equations, the theoretical underpinnings of quantum loop theory, the role of entropy and heat in the determination of what makes TIME, and half philosophy and what makes our consciousness drag together all the underpinnings of the blur we call reality.

Together, this is physics and metaphysics. The Greeks got it pretty damn close, but then, so did St. Augustine and Heidegger and Kant. Is it all relative? Yep. Thank you, Einstein. Every point on the curve of our universe has its own particular Time. Now is meaningless since the relationship between every point can never intersect with the others. It's all past or future and THAT is all perception. Time is change, too, and not to put too fine a point on it, all we can really do is put a rate on it, never carve it up into its smallest particle.

So what about consciousness? It's all interpretation of what we see, baby. The stratifications of what we work by are just an approximation and it says nothing about how a child sees a day versus how an old person sees it.

Carlo Rovelli combines the two and does an admirable job of trying to reconcile it all.

Impossible, you say? Possibly, but he also gets 9 out of 10 points for style. :) Beautifully written.
( )

Before reading this book, I had a naive and simplistic view of time, but this book made me realize both how wrong I was and how complex the whole issue of time really is. I read it fascinated by the insights about the true meaning of “time,” the puzzlement felt by physicists as they seek a deeper understanding of it and the coveralls complexity of understanding time and breaking it down to its components parts. It’s smallest possible level.
The concepts covered in the book are complex, technically detailed and require a lot of either background understanding or details explanation. The author offers the needed explanations in ways even ignorant people like me can understand.
This is not and easy read in terms of its content-the concepts are complex-nut the author has made it seem easy to read through his careful, direct style.
I know a lot more now than I did before reading it and I feel good about what I have learned. ( )

Before reading this book, I had a naive and simplistic view of time, but this book made me realize both how wrong I was and how complex the whole issue of time really is. I read it fascinated by the insights about the true meaning of “time,” the puzzlement felt by physicists as they seek a deeper understanding of it and the coveralls complexity of understanding time and breaking it down to its components parts. It’s smallest possible level.
The concepts covered in the book are complex, technically detailed and require a lot of either background understanding or details explanation. The author offers the needed explanations in ways even ignorant people like me can understand.
This is not and easy read in terms of its content-the concepts are complex-nut the author has made it seem easy to read through his careful, direct style.
I know a lot more now than I did before reading it and I feel good about what I have learned. ( )

La mia comprensione è di tipo quantico, se ho afferrato bene un concetto questa comprensione è relegata ad un momento t' soggettivo; ho ricordo del momento, della comprensione ma non del concetto. Dev'esser colpa dell'entropia. ( )

An excellent book from Carlo Rovelli in which he explains how physicists understand time today. He starts with the everyday conception of time as "something that flows uniformly and equally throughout the universe", and shows how physics has revealed this to be "an approximation of a much more complex reality." He explains how relativity and quantum mechanics have shown time to be quite different when we look outside of the narrow confines of our everyday experience. The order of past, present and future is only partial and the speed at which time passes varies depending on speed and the presence of gravity. The fundamental equations of physics show no preferred direction for time, moving forwards and backwards in time are on an equal footing. He has quite an extensive discussion on how thermodynamics and entropy can give rise to the direction of time that we experience.

He starts with the theories that all physicists would agree on: general relativity and quantum mechanics, later in the book moving on his own interpretation of the implications of the work to combine these two theories, and in particular the program of loop quantum gravity that he is working on.

Rovelli has a great gift for providing clear explanations of complex theories and combining this with discussion of the philosophical implications. I couldn't put this book down, a delightful read. ( )

This book is hard to describe. It does you little good to hear that it is written by one of the world’s great scientist-writers, and even less that he is a founder of the field of loop quantum gravity in theoretical physics. I could report to you that Rovelli has a genius for unification. He translates the challenging language of the science of time and grounds it in a philosophical perspective that is illuminating, poetic, rare and rarefied. Rovelli’s book grapples with the unbridgeable gap between what our science indicates and our myopic human understanding of reality. We extrapolate from our limited interactions with the world through brains unequipped for the task. And yet Rovelli renders our struggle into sublime poetry. But this too does you little good to hear. I recommend the book most highly.

I offer one quote, evocative of time, the author citing the Hindu epic the Mahabharata: “Every day countless people die, and yet those who remain live as if they were immortals.”

Before I read this book I had no time for it; whilst reading it I had no time for anything else; after reading it I had no time for it...

Thinking again, this is a valiant attempt to explain Einstein's theory of relativity, which includes time as well as space. Perhaps time is a "by-product" of gravity, as, at the level of stars and planets movement is induced by gravity, and perceived movement of objects relative to each other allows us to "construct" time (temporal concepts with which to order our world). So, for example, "baroque" and jurassic" are useful concepts for us, but do not apply anywhere else, i.e. off-planet. For each planet with concious life-forms there could be said to exist "pools of time", each of which is strictly local. The fact that there are planets where days are longer than years seems to support this general hypothesis...

Italian physicist Carlo Rovelli shows he has a firm grasp of his subject very early on, describing his book as "a fiery magma of ideas, sometimes illuminating, sometimes confusing" (pg. 5). That's a very accurate description for where he then takes us in The Order of Time, a somewhat unlikely bestseller even when you consider the popularity of popular science. Unlikely, that is, until you recognise the evocative phrase Rovelli deploys there.

Fiery magma – it's this kind of phrasemaking that really helps the book rise above the pack (see also "the great fresco of the cosmos" (pg. 126) – perhaps it's just because he's Italian that he can get away with it). To be sure, his scientific thoughts are fascinating and, particularly in the first part, he is a gentle and lucid guide through spacetime and quantum mechanics. Compelling us to look with the "unhinged eye of the mind" (pg. 13) that is necessary to grapple with often counterintuitive concepts, Rovelli makes us rethink – legitimately – everything we thought we knew about time, even the fundamental stuff.

But it is the phrasing and the language that stands out. He unapologetically elevates poetry to the same table as physics and philosophy ("poetry is another of science's deepest roots: the capacity to see beyond the visible" (pg. 21)) and he moves between the three with a quicksilver ease. The book does become much more difficult to follow in Part Three (at one point, he even suggests some readers might want to skip ahead two chapters; this is never a good sign – either the words are necessary or they are not) but The Order of Time rouses itself to claim that one thing which always guarantees good reviews: a strong ending.

It is a book that will induce both headaches and awe; that will both disconcert and inspire you with the fact that the simple things are of astonishing complexity, with our existing scientific explanations "reveal[ing] themselves to be progressively more threadbare as we widen our gaze" (pg. 173n). But though Rovelli often loses us, even when we're paying attention, he brings us back ("we may smile now" (pg. 175)). Like the quantum wealth its author guides us through, The Order of Time is an astonishing weave. ( )

A recent review of this book on Goodreads contains the sentence "That's beautiful, even if I don't quite fully understand it.” I can’t help but suspect this attitude underlies many of the positive reviews. Rovelli is eloquent throughout, but after the first few chapters, his level of clarity seems to me to drop substantially.

In those early chapters, one of Rovelli's objectives is to disabuse us of the notion that “the present” exists in any absolute sense:

"What is happening ‘now' in a distant place? Imagine, for example, that your sister has gone to Proxima b, the recently discovered planet that orbits a star at approximately four light-years’ distance from us. What is your sister doing now on Proxima b? The only correct answer is that the question makes no sense. It is like asking 'What is here, in Beijing?' when we are in Venice. It makes no sense because if I use the word ‘here' in Venice, I am referring to a place in Venice, not in Beijing.”

He gives a lucid and satisfying explanation of this, and goes on to describe a way of looking at time as a network of events in which each one has a past and future but there is no global ordering of all the events.

Shortly thereafter, though, we speed through a diagram of wobbly light-cones arranged in a temporal loop, and I find myself wishing for more concrete examples to illustrate exactly what this implies. Several other ideas in the book come across hazily. Rovelli does not want us to believe we live in a “block universe” where everything is static and unchanging, but I could have benefited from more explanation of how (and why) else to conceptualize the present-less network of events he describes. There is a lot of intriguing discussion about the meaning of entropy, but the conclusions he suggests regarding the nature of time are difficult to follow or evaluate.

This book is probably not a good way to get a grasp on the subject matter, though it’s thought-provoking and sometimes moving.

"I am not this momentary mass of flesh reclined on the sofa typing the letter a on my laptop; I am my thoughts full of the traces of the phrases that I am writing; I am my mother’s caresses, and the serene kindness with which my father calmly guided me; I am my adolescent travels; I am what my reading has deposited in layers in my mind; I am my loves, my moments of despair, my friendships, what I’ve written, what I’ve heard; the faces engraved on my memory. I am, above all, the one who a minute ago made a cup of tea for himself. The one who a moment ago typed the word “memory” into his computer. The one who just composed the sentence that I am now completing. If all this disappeared, would I still exist? I am this long, ongoing novel. My life consists of it."

( )

Time is in Reality's Blurring: "The Order of Time" by Carlo Rovelli

"Among the strange phenomena was the sense of time stopping. Things were happening in my mind but the clock was not going ahead; the flow of time was not passing any more."

In “The Order of Time” by Carlo Rovelli

And it's here that Rovelli reveals a fundamental flaw in his thinking. On the one hand he argues that scientists have proven that time is discontinuous, and not what it may seem to the naked eye. On the other he sees his own drugged-out experiences (or worse: his memory of his subjective drugged-out experiences) as having an objectivity that doesn't require any questioning. He is convinced that his memory of his LSD inspired experience of time stopping is what actually happened. I would suggest (rather strongly) that perhaps it is not. Apart from his New Age druggy musings, which I'm sure are an entertaining read to folks who haven't really given much time to reading or thinking about time before, I find he has little new to offer. Emperor's new clothes again. Rovelli is an average thinker and certainly able to move between physics and philosophy with greater ease than for example Michuio Kaku’s crap (e.g. "The Future of Humanity".) Nevertheless, Smolin's take on time is much more interesting than Rovelli's.

Readers interested in this sort of thing (I hope there are many of them) might also like “Great Ideas in Physics” by Alan Lightman. The ideas in question being brief introductions to the conservation of energy, the second law of thermodynamics, the theory of relativity and quantum mechanics. The book is written from a 'liberal arts' perspective and has much to say about the philosophy of science, and a good deal to say about time, which is why I make the comparison. It does contain math, but only algebra - no calculus is required. The influence of the ideas on other areas of society is emphasized. Rovelli's best work has been done in collaboration with researchers such as Lee Smolin - specifically in the attempt to develop loop quantum gravity. Their work is explicitly opposed to that of string theory, & seeks to develop the possibility of experimental testing for the theory - which string theorists conspicuously do not.

In some ways, Rovelli's writing is as influenced by Calvino as it is by Einstein or Feynman - this is not simply writing in the tradition of explicating or popularising scientific inquiry; but rather writing which seeks to open new spaces of possibility for thinking through the very endeavour of the writing itself. There does seem to be an appetite for knowledge out there, although the problem (so it seems to me at least) with physics for a wide audience is that ultimately there is only so much that you can do without resorting to maths. A good example would be any of the 'popular' books written on physics by Paul Nahin. They are quite excellent, but they require the readership to be mathematically literate at least as far as differential equations. For that matter, so does Feynman. This is no problem for me, but I wonder who else reads this sort of thing apart from serious students of the subject? Hawking famously said that his publisher told him that every equation included halved the sales figures, but insisted on including E =mc^2 anyway.

It seems to me that the barrier of what can be done without maths (rather little) and what can be done with it (virtually everything) will remain insurmountable. A fact (if it is one) which gives me no pleasure at all to state.

NB: What a difference when compared to “Reality is not What It Seems”. ( )