The Order of Time

by Carlo Rovelli

Let’s begin with a simple fact: time passes faster in the mountains than it does at sea level.

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.

a ball may fall, but it can also come back up, by rebounding, for instance. Heat cannot. This is the only basic law of physics that distinguishes the past from the future.

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.

The growth of entropy is nothing other than the ubiquitous and familiar natural increase of disorder.

This is what Boltzmann understood. 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.

entropy, as Boltzmann fully understood, is nothing other than the number of microscopic states that our blurred vision of the world fails to distinguish.

“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.

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

The idea that a well-defined now exists throughout the universe is an illusion, an illegitimate extrapolation of our own experience.

In other words, a minimum interval of time exists. Below this, the notion of time does not exist—even in its most basic meaning.

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.

“Time is composed of atoms, that is to say of many parts that cannot be further subdivided, on account of their short duration.”

You got to deep-six your wristwatch, you got to try and understand, The time it seems to capture is just the movement of its hands

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.

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

This is time for us. Memory and nostalgia. The pain of absence. 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.

I have had the unheard-of good fortune of experiencing a global vision of my being—not of a particular moment, but of my existence “as a whole.” I was able to compare its finite nature in space, against which no one protests, with its finite nature in time, which is instead the source of so much outrage.

It happens because the improbability of a correlation between two events requires something improbable, and it is only the low entropy of the past that provides such improbability. What else could? In other words, the existence of common causes in the past is nothing but a manifestation of low entropy in the past. In a state of thermal equilibrium, or in a purely mechanical system, there isn’t a direction to time identified by causality.

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. It is substantially a consideration made in the third person, not in the first,

The starting point for Descartes is the methodical doubt experienced by a refined intellectual, not the basic experience of a subject.)

My primary experience—if we grant that this means anything—is to see the world around me, not myself.

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

To a large extent, the brain is a mechanism for collecting memories of the past in order to use them continually to predict the future.

we are always in the present, because the past is past and therefore does not exist, and the future has yet to arrive, so it does not exist either. And he asks himself how we can be aware of duration—or even be capable of evaluating it—if we are always only in a present that is, by definition, instantaneous.

It is within my mind, then, that I measure time. I must not allow my mind to insist that time is something objective. When I measure time, I am measuring something in the present of my mind. Either this is time, or I have no idea what time is.

We can say that we measure duration with a clock. But to do so requires us to read it at two different moments: this is not possible, because we are always in one moment, never in two.

because our consciousness is based on memory and on anticipation. A hymn, a song, is in some way present in our minds in a unified form, held together by something—by that which we take time to be. And hence this is what time is: it is entirely in the present, in our minds, as memory and as anticipation.

for a sound naturalist wishing to avoid drowning in the useless vortices of idealism, the former (the physical world) comes first, while the latter (consciousness)—independently of how well we understand it—is determined by the first. It is an entirely reasonable objection, just so long as physics reassures us that the external flow of time is real, universal, and in keeping with our intuitions. But if physics shows us instead that such time is not an elementary part of reality, can we continue to overlook Augustine’s observation and treat it as irrelevant to the true nature of time?

ourselves included. We are stories, contained within the twenty complicated centimeters behind our eyes, lines drawn by traces left by the (re)mingling together of things in the world, and oriented toward predicting events in the future, toward the direction of increasing entropy, in a rather particular corner of this immense, chaotic universe.

our introspection is easily capable of imagining itself without there being space or matter, but can it imagine itself not existing in time?

Time, then, is the form in which we beings, whose brains are made up essentially of memory and foresight, interact with the world: it is the source of our identity.123 And of our suffering as well.

“Every day countless people die, and yet those who remain live as if they were immortals.”128