Carlo Rovelli The Order Of Time Quotes

It is like the point where the rainbow touches the forest. We think that we can see it—but if we go to look for it, it isn’t there.

The ability to understand something before it’s observed is at the heart of scientific thinking.

If I ask whether two events—one on Earth and the other on Proxima b—are happening “at the same moment,” the correct answer would be: “It’s a question that doesn’t make sense, because there is no such thing as ‘the same moment’ definable in the universe.” The “present of the universe” is meaningless.

All of the sons of Adam are part of one single body, They are of the same essence. When time afflicts us with pain In one part of that body All the other parts feel it too. If you fail to feel the pain of others You do not deserve the name of man.

It is entropy, not energy, that keeps stones on the ground and the world turning.

But it isn’t absence that causes sorrow. It is affection and love. Without affection, without love, such absences would cause us no pain. For this reason, even the pain caused by absence is, in the end, something good and even beautiful, because it feeds on that which gives meaning to life.

Temporality is profoundly linked to blurring. The blurring is due to the fact that we are ignorant of the microscopic details of the world. The time of physics is, ultimately, the expression of our ignorance of the world. Time is ignorance.

We inhabit time as fish live in water. Our being is being in time.

We can think of the world as made up of things. Of substances. Of entities. Of something that is. Or we can think of it as made up of events. Of happenings. Of processes. Of something that occurs. Something that does not last, and that undergoes continual transformation, that is not permanent in time.

O gentlemen, the time of life is short . . . And if we live, we live to tread on kings. Shakespeare, Henry IV, Part I (act 5, scene 2)

This is the disconcerting conclusion that emerges from Boltzmann’s work: the difference between the past and the future refers only to our own blurred vision of the world. It’s a conclusion that leaves us flabbergasted: is it really possible that a perception so vivid, basic, existential—my perception of the passage of time—depends on the fact that I cannot apprehend the world in all of its minute detail? On a kind of distortion that’s produced by myopia? Is it true that, if I could see exactly and take into consideration the actual dance of millions of molecules, then the future would be “just like” the past?

A stone is a prototypical “thing”: we can ask ourselves where it will be tomorrow. Conversely, a kiss is an “event.” It makes no sense to ask where the kiss will be tomorrow. The world is made up of networks of kisses, not of stones.

How long is forever?” asks Alice. “Sometimes, just one second,” replies the White Rabbit. There are dreams lasting an instant in which everything seems frozen for an eternity.

Things” in themselves are only events that for a while are monotonous

A moving object therefore experiences a shorter duration than a stationary one: a watch marks fewer seconds, a plant grows more slowly, a young man dreams less. For a moving object, time contracts.

Children grow up and discover that the world is not as it seemed from within the four walls of their homes. Humankind as a whole does the same.

The notion of “the present” refers to things that are close to us, not to anything that is far away. Our “present” does not extend throughout the universe. It is like a bubble around us.

We are the products of a long selection process of chemical, biological, and cultural structures that at different levels have interacted for a long time in order to shape the funny process that we are.

The heat of black holes is like the Rosetta stone of physics, written in a combination of three languages- quantum, gravitational, and thermodynamic- still awaiting decipherment in order to reveal the true nature of time.

If things fall, it is due to this slowing down of time. Where time passes uniformly, in interplanetary space, things do not fall. They float, without falling. Here on the surface of our planet, on the other hand, the movement of things inclines naturally toward where time passes more slowly, as when we run down the beach into the sea and the resistance of the water on our legs makes us fall headfirst into the waves. Things fall downward because, down there, time is slowed by the Earth.

Those who defend this way of thinking about reality—eternalism—frequently cite Einstein, who in a famous letter writes: For people like us who believe in physics the distinction between past, present and future is only a stubbornly persistent illusion.

Our “present” does not extend throughout the universe. It is like a bubble around us.

The world is not a collection of things, it is a collection of events.

Newton’s mechanics, Maxwell’s equations, quantum mechanics, and so on, tell us how events happen, not how things are.

Every day countless people die, and yet those who remain live as if they were immortals.

Time, as Aristotle suggested, is the measure of change;

The entire evolution of science would suggest that the best grammar for thinking about the world is that of change, not of permanence. Not of being, but of becoming.

None of the pieces that time has lost (singularity, direction, independence, the present, continuity) puts into question the fact that the world is a network of events. On the one hand, there was time, with its many determinations; on the other, the simple fact that nothing is: things happen.

As human beings, we live by emotions and thoughts. We exchange them when we are in the same place at the same time, talking to each other, looking into each other’s eyes, brushing against each other’s skin. We are nourished by this network of encounters and exchanges. But, in reality, we do not need to be in the same place and time to have such exchanges. Thoughts and emotions that create bonds of attachment between us have no difficulty in crossing seas and decades, sometimes even centuries, tied to thin sheets of paper or dancing between the microchips of a computer. We are part of a network that goes far beyond the few days of our lives and the few square meters that we tread. This book is also a part of that weave. . .

Every moment of our existence is linked by a peculiar triple thread to our past—the most recent and the most distant—by memory. Our present swarms with traces of our past. We are histories of ourselves, narratives. 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.

The entropy of a system depends explicitly on blurring. It depends on what I do not register, because it depends on the number of indistinguishable configurations. The same microscopic configuration may be of high entropy with regard to one blurring and of low in relation to another.

Change is ubiquitous. Only: elementary processes cannot be ordered along a common succession of instants. At the extremely small scale of the quanta of space, the dance of nature does not develop to the rhythm kept by the baton of a single orchestral conductor: every process dances independently with its neighbours, following its own rhythm. The passing of time is intrinsic to the world, it is born of the world itself, out of the relations between quantum events which are the world and which themselves generate their own time.

Abstract thought can anticipate by centuries hypotheses that find a use—or confirmation—in scientific inquiry.

We long for timelessness, we endure the passing of time: we suffer time. Time is suffering.

But the world is a quantum one, and gelatinous spacetime is also an approximation.

Aristotle is the first we are aware of to have asked himself the question “What is time?,” and he came to the following conclusion: time is the measurement of change.

Time passes more slowly for the one who keeps moving.

But there are not just two times. Times are legion: a different one for every point in space. There is not one single time; there is a vast multitude of them.

Scientists are not immune from talking nonsense.

The events of the world do not form an orderly queue, like the English. They crowd around chaotically, like Italians.

we understand the world by studying change, not by studying things.

Our fear of death seems to me to be an error of evolution.

Don’t take your intuitions and ideas to be “natural”: they are often the products of the ideas of audacious thinkers who came before us.

Fearing the transition, being afraid of death, is like being afraid of reality itself; like being afraid of the sun. Whatever for?

The mystery of time has always troubled us, stirring deep emotions. So deep as to have nourished philosophies and religions.

Wonder is the source of our desire for knowledge,1 and the discovery that time is not what we thought it was opens up a thousand questions.

And it seems to me that life, this brief life, is nothing other than this: the incessant cry of these emotions that drive us, that we sometimes attempt to channel in the name of a god, a political faith, in a ritual that reassures us that, fundamentally, everything is in order, in a great and boundless love—and the cry is beautiful. Sometimes it is a cry of pain. Sometimes it is a song.

It is in order to escape this anxiety that we have imagined the existence of “eternity,” a strange world outside of time that we would like to be inhabited by gods, by a God, or by immortal souls.

Things are transformed one into another according to necessity, and render justice to one another according to the order of time. “According to the order of time” (κατὰ τὴν τοῦ χρόνου τάξιν). From

What causes us to suffer is not in the past or the future: it is here, now, in our memory, in our expectations. We long for timelessness, we endure the passing of time: we suffer time. Time is suffering.

Music can occur only in time, but if we are always in the present moment, how is it possible to hear it? It is possible, Augustine observes, because our consciousness is based on memory and on anticipation.

Perhaps the rivers of ink that have been expended discussing the nature of the “continuous” over the centuries, from Aristotle to Heidegger, have been wasted. Continuity is only a mathematical technique for approximating very finely grained things. The world is subtly discrete, not continuous. The good Lord has not drawn the world with continuous lines: with a light hand, he has sketched it in dots, like the painter Georges Seurat.

It follows that the notion of certain configurations being more particular than others (twenty-six red cards followed by twenty-six black, for example) makes sense only if I limit myself to noticing only certain aspects of the cards (in this case, the colors). If I distinguish between all the cards, the configurations are all equivalent: none of them is more or less particular than others.18 The notion of “particularity” is born only at the moment we begin to see the universe in a blurred and approximate way.

There is no “truer” time; there are two times and they change relative to each other. Neither is truer than the other. But there are not just two times. Times are legion: a different one for every point in space. There is not one single time; there is a vast multitude of them.

(Even the attribution of the idea to Descartes seems wrong to me: Cogito ergo sum is not the first step in the Cartesian reconstruction, it is the second. The first is Dubito ergo cogito. The starting point of the reconstruction is not a hypothetical a priori that is immediate to the experience of existing as a subject. It’s a rationalistic a posteriori reflection on the first stage of the process in which Descartes had articulated a state of doubt: logic dictates that if someone doubts something, they must have thought about it. And that if they can think, then they must exist.

Is the daily spectacle of a revolving universe “illusory”? No, it is real, but it doesn’t involve the cosmos alone. It involves our relation with the sun and the stars. We understand it by asking ourselves how we move. Cosmic movement emerges from the relation between the cosmos and ourselves.

We can see the world without time: we can perceive with the mind’s eye the profound structure of the world where time as we know it no longer exists—like the Fool on the Hill who sees the Earth turn when he sees the setting sun. And we begin to see that we are time. We are this space, this clearing opened by the traces of memory inside the connections between our neurons. We are memory. We are nostalgia. We are longing for a future that will not come. The clearing that is opened up in this way, by memory and by anticipation, is time: a source of anguish sometimes, but in the end a tremendous gift.

[S]ong, as Augustine observed, is the awareness of time. It is time. It is the hymn of the Vedas that is itself the flowering of time. In the Benedictus of Beethoven’s Missa Solemnis, the song of the violin is pure beauty, pure desperation, pure joy. We are suspended, holding our breath, feeling mysteriously that this must be the source of meaning. That this is the source of time. Then the song fades and ceases. “The silver thread is broken, the golden bowl is shattered, the amphora at the fountain breaks, the bucket falls into the well, the earth returns to dust.” And it is fine like this. We can close our eyes, rest. This all seems fair and beautiful to me. This is time.

In the elementary equations of the world,13 the arrow of time appears only where there is heat.* The link between time and heat is therefore fundamental: every time a difference is manifested between the past and the future, heat is involved. In every sequence of events that becomes absurd if projected backward, there is something that is heating up.

In The Order of Time, physicist and author Carlo Rovelli sums up this dynamic beautifully: "It isn't absence that causes sorrow. It is affection and love. Without affection, without love, such absences would cause us no pain. For this reason, even the pain caused by absence is, in the end, something good and even beautiful, because it feeds on that which gives meaning to life.

Augustine’s exposition of the idea is quite beautiful. It is based on our experience of music. When we listen to a hymn, the meaning of a sound is given by the ones that come before and after it. Music can occur only in time, but if we are always in the present moment, how is it possible to hear it? It is possible, Augustine observes, because our consciousness is based on memory and on anticipation.

Hold on tight, because we are about to take off. “NOW” MEANS NOTHING 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.

In the elementary equations of the world,13 the arrow of time appears only where there is heat.* The link between time and heat is therefore fundamental: every time a difference is manifested between the past and the future, heat is involved. In every sequence of events that becomes absurd if projected backward, there is something that is heating up. If I watch a film that shows a ball rolling, I cannot tell if the film is being projected correctly or in reverse. But if the ball stops, I know that it is being run properly; run backward, it would show an implausible event: a ball starting to move by itself. The ball’s slowing down and coming to rest are due to friction, and friction produces heat. Only where there is heat is there a distinction between past and future. Thoughts, for instance, unfold from the past to the future, not vice versa—and, in fact, thinking produces heat in our heads. . . .

Ten years before understanding that time is slowed down by mass,21 Einstein had realized that it was slowed down by speed.22 The consequence of this discovery for our basic intuitive perception of time is the most devastating of all. The fact itself is quite simple. Instead of sending the two friends from the first chapter to the mountains and the plains, respectively, let’s ask one of them to stay still and the other one to walk around. Time passes more slowly for the one who keeps moving. As before, the two friends experience different durations: the one who moves ages less quickly, his watch marks less time passing; he has less time in which to think; the plant he is carrying takes longer to germinate, and so on. For everything that moves, time passes more slowly.

The entropy of the world in the far past appears very low to us. But this might not reflect the exact state of the world: it might regard the subset of the world’s variables with which we, as physical systems, have interacted. It is with respect to the dramatic blurring produced by our interactions with the world, caused by the small set of macroscopic variables in terms of which we describe the world, that the entropy of the universe was low. This, which is a fact, opens up the possibility that it wasn’t the universe that was in a very particular configuration in the past. Perhaps instead it is us, and our interactions with the universe, that are particular. We are the ones who determine a particular macroscopic description. The initial low entropy of the universe, and hence the arrow of time, may be more down to us than to the universe itself. This is the basic idea.

What works instead is thinking about the world as a network of events. Simple events, and more complex events that can be disassembled into combinations of simpler ones. A few examples: a war is not a thing, it’s a sequence of events. A storm is not a thing, it’s a collection of occurrences. A cloud above a mountain is not a thing, it is the condensation of humidity in the air that the wind blows over the mountain. A wave is not a thing, it is a movement of water, and the water that forms it is always different. A family is not a thing, it is a collection of relations, occurrences, feelings. And a human being? Of course it’s not a thing; like the cloud above the mountain, it’s a complex process, where food, information, light, words, and so on enter and exit. . . . A knot of knots in a network of social relations, in a network of chemical processes, in a network of emotions exchanged with its own kind.

And it seems to me that life, this brief life, is nothing other than this: the incessant cry of these emotions that drive us, that we sometimes attempt to channel in the name of a god, a political faith, in a ritual that reassures us that, fundamentally, everything is in order, in a great and boundless love—and the cry is beautiful. Sometimes it is a cry of pain. Sometimes it is a song. And song, as Augustine observed, is the awareness of time. It is time. It is the hymn of the Vedas that is itself the flowering of time.131 In the Benedictus of Beethoven’s Missa Solemnis, the song of the violin is pure beauty, pure desperation, pure joy. We are suspended, holding our breath, feeling mysteriously that this must be the source of meaning. That this is the source of time. Then the song fades and ceases. “The silver thread is broken, the golden bowl is shattered, the amphora at the fountain breaks, the bucket falls into the well, the earth returns to dust.”132 And it is fine like this. We can close our eyes, rest. This all seems fair and beautiful to me. This is time.

The physical substratum that determines duration and physical intervals—the gravitational field—does not only have a dynamic influenced by masses; it is also a quantum entity that does not have determined values until it interacts with something else. When it does, the durations are granular and determinate only for that something with which it interacts; they remain indeterminate for the rest of the universe.

as Hans Reichenbach suggests in one of the most lucid books on the nature of time, The Direction of Time,

Between the past and the future of an event (for example, between the past and the future for you, where you are, and in the precise moment in which you are reading), there exists an “intermediate zone,” an “extended present”; a zone that is neither past nor future. This is the discovery made with special relativity. The duration of this “intermediate zone,”* which is neither in your past nor in your future, is very small and depends on where an event takes place relative to you, as illustrated in figure 3.2: the greater the distance of the event from you, the longer the duration of the extended present. At a distance of a few meters from your nose, the duration of what for you is the “intermediate zone,” neither past nor future, is no more than a few nanoseconds: next to nothing (the number of nanoseconds in a second is the same as the number of seconds in thirty years). This is much less than we could possibly notice. On the other side of the ocean, the duration of this “intermediate zone” is a thousandth of a second, still well below the threshold of our perception of time, the minimum amount of time we perceive with our senses, which is somewhere on the order of a tenth of a second. But on the moon, the duration of the “extended present” is a few seconds, and on Mars it is a quarter of an hour. This means we can say that on Mars there are events that in this precise moment have already happened, events that are yet to happen, but also a quarter-of-an-hour of events during which things occur that are neither in our past nor in our future. They are elsewhere. We had never before been aware of this “elsewhere” because next to us this “elsewhere” is too brief; we are not quick enough to notice it. But it exists, and is real. This is why it is impossible to hold a smooth conversation between here and Mars. Say I am on Mars and you are here; I ask you a question and you reply as soon as you’ve heard what I said; your reply reaches me a quarter of an hour after I had posed the question. This quarter of an hour is time that is neither past nor future to the moment you’ve replied to me. The key fact that Einstein understood is that this quarter of an hour is inevitable: there is no way of reducing it. It is woven into the texture of the events of space and of time: we cannot abbreviate it, any more than we can send a letter to the past. It’s strange, but this is how the world happens to be.

Ten years before understanding that time is slowed down by mass,21 Einstein had realized that it was slowed down by speed.22 The consequence of this discovery for our basic intuitive perception of time is the most devastating of all.

The synthesis between Aristotle’s time and Newton’s is the most valuable achievement made by Einstein. It is the crowning jewel of his thought.

Physics does not describe how things evolve “in time” but how things evolve in their own times, and how “times” evolve relative to each other.*

Time has lost its first aspect or layer: its unity. It has a different rhythm in every different place and passes here differently from there.

We often say that causes precede effects and yet, in the elementary grammar of things, there is no distinction between “cause” and “effect.”* There

If the present has no meaning, then what “exists” in the universe? Is not what “exists” precisely what is here “in the present”? The whole idea that the universe exists now in a certain configuration and changes together with the passage of time simply doesn’t stack up anymore.

Proper time” depends not only on where you are and your degree of proximity to masses; it depends also on the speed at which you move. It’s a strange enough fact in itself, but its consequences are extraordinary. Hold on tight, because we are about to take

The difference between past and future does not lie in the elementary laws of motion; it does not reside in the deep grammar of nature. It is the natural disordering that leads to gradually less particular, less special situations.

The notion of “particularity” is born only at the moment we begin to see the universe in a blurred and approximate way.

Times are legion: a different one for every point in space. There is not one single time; there is a vast multitude of them. The time indicated by a particular clock measuring a particular phenomenon is called ‘proper time’ in physics. Every clock has its proper time. Every phenomenon that occurs has its proper time, its own rhythm.

But why should we belong to one of these special systems? For the same reason that apples grow in northern Europe, where people drink cider, and grapes grow in the south, where people drink wine; or that I was born where people happen to speak my native language; or that the sun which warms us is at the right distance from us—not too close and not too far away. In all these cases, the “strange” coincidence arises from confusing the causal relations: it isn’t that apples grow where people drink cider, it is that people drink cider where apples grow. Put this way, there is no longer anything strange about

Similarly, in the boundless variety of the universe, it may happen that there are physical systems that interact with the rest of the world through those particular variables that define an initial low entropy. With regard to these systems, entropy is constantly increasing. There, and not elsewhere, there are the typical phenomena associated with the flowing of time: life is possible, together with evolution, thought, and our awareness of time passing. There, the apples grow that produce our cider: time. That sweet juice that contains all the ambrosia and all the gall of life.

When we do science, we want to describe the world in the most objective way possible. We try to eliminate distortions and optical illusions deriving from our point of view. Science aspires to objectivity, to a shared point of view about which it is possible to be in agreement.

INDEXICALITY

It is what philosophers call “indexicality”: the characteristic of certain words that have a different meaning every time they are used, a meaning determined by where, how, when, and by whom they are being spoken. Words such as “here,” “now,” “I,” “this,” “tonight” all assume a different meaning depending on who utters them and the circumstances in which they are uttered. “My name is Carlo Rovelli” is true if I say it, but untrue if someone else not also called Carlo Rovelli uses the same phrase.

We observe the universe from within it, interacting with a minuscule portion of the innumerable variables of the cosmos. What we see is a blurred image. This blurring suggests that the dynamic of the universe with which we interact is governed by entropy, which measures the amount of blurring. It measures something that relates to us more than to the cosmos.

A small system S does not distinguish the details of the rest of the universe because it interacts only with a few among the variables of the rest of the universe.

It is the presence of abundant traces of the past that produces the familiar sensation that the past is determined.

If a subset of the universe is special in this sense, then for this subset the entropy of the universe is low in the past, the second law of thermodynamics obtains; memories exist, traces are left—and there can be evolution, life, and thought. In other words, if in the universe there is something like this—and it seems natural to me that there could be—then we belong to that something. Here, “we” refers to that collection of physical variables to which we commonly have access and by means of which we describe the universe.

it is simply a process that degrades and consumes the low entropy of food; it is a self-structured disordering, no more and no less than in the rest of the universe.

We are processes, events, composite and limited in space and time. But if we are not an individual entity, what is it that founds our identity and its unity?

And hence this is what time is: it is entirely in the present, in our minds, as memory and as anticipation.

The present is a localized rather than a global phenomenon.

The first is that every one of us identifies with a point of view in the world.

The second ingredient on which our identity is based is the same as for the chariot. In the process of reflecting the world, we organize it into entities: we conceive of the world by grouping and segmenting it as best we can in a continuous process that is more or less uniform and stable, the better to interact with it.

we are the reflection of the idea of ourselves that we receive back from our kind.

But there is a third ingredient in the foundation of our identity, and it is probably the essential one—it is the reason this delicate discussion is taking place in a book about time: memory.

The surprise has been that, in the emergence of familiar aspects of time, we ourselves have had a role to play. From our perspective—the perspective of creatures who make up a small part of the world—we see that world flowing in time. Our interaction with the world is partial, which is why we see it in a blurred way. To this blurring is added quantum indeterminacy. The ignorance that follows from this determines the existence of a particular variable—thermal time (chapter 9)—and of an entropy that quantifies our uncertainty.

It’s suffering because we must lose what we have and are attached to. Because everything that begins must end. What causes us to suffer is not in the past or the future: it is here, now, in our memory, in our expectations. We long for timelessness, we endure the passing of time: we suffer time. Time is suffering.

Because it is nothing but a fleeting structure of the world, an ephemeral fluctuation in the happening of the world, that which is capable of giving rise to what we are: beings made of time. That to which we owe our being, giving us the precious gift of our very existence, allowing us to create the fleeting illusion of permanence that is the origin of all our suffering.