Reading notes of “The order of time” by Carlo Rovelli

Time is a strange thing. When we don’t need it, it is nothing. Then, suddenly, there is nothing else. It is everywhere around us, also within us. It seeps into our faces. It seeps into the mirror, runs through my temples…between you and I it runs silently, like an hourglass. Oh, Quin Quin. Sometimes I feel it flowing inexorably. Sometimes I get up in the middle of the night and stop all the clocks.

— Hofmannsthal

“The order of time” is a very scientific & poetic book about time, physics, life. I finished this book in 3 days after watched the movie “tenet”. Below are some sentences I quoted from this lovely book.

We inhabit time as fish live in water.

Reality is often very different from what it seems.

Wonder is the source of our desire for knowledge.

We conventionally think of times as something simple and fundamental that flows uniformly, independently from everything else, from the past to the future, measured by clocks and watches.

Time passes faster in the mountains than it does at sea level.

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. Things fall downward because down there, time is slowed by the Earth.

Down is a time word, not a space word. Things fall down because they fall down in the direction in which time is passing more slowly. — Quora

There is no “truer” value, they are two currencies that have value relative to each other. There is no “truer” time; there are two times and they change relative to each other.

In the elementary equations of the world, the arrow of time appears only where there is heat. Only where there is heat is there a distinction between past and future.

The entropy never decreases. Delta S is always greater than or equal to zero. It is the second principle of thermodynamics and it is the only equation of fundamental physics that knows any difference between past and future. The only one that speaks of the flowing of time.

It is the entropy, not energy, that drives the world. What makes the world go round are not sources of energy but sources of low entropy.

Heat is the microscopic agitation of molecules. Hot tea is tea in which the molecules are very agitated, In an ice cube, warming up and melting molecules become increasingly agitated and lose their strict connections.

Thermal agitation is like a continual shuffling of a pack of cards: if the cards are in order, the shuffling disorders them. In this way, heat passes from hot to cold, not vice versa. The growth of entropy if nothing order than the ubiquitous and familiar natural increase of disorder.

Entropy is nothing other than the number of microscopic states that our blurred vision of the world fails to distinguish.

For everything that moves, time passes more slowly.

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

In the below picture, a continuous trajectory towards the future returns ti the originating event, to where it began:

Near to a black hole, the lines converge toward it: this is because the mass of the black hole slows time to such a degree that, at its border (“horizon”), time stands still.

Time is elastic in our personal experience of it. For centuries, we have divided time into days, the days into hours.

Aristotle: time is the measure of change: if nothing changes there is no time.

Newton: “True” time that passes regardless, independently of things and of their changes.

Granularity is ubiquitous in nature: light is made of photons, the particles of light.

There is no single time: there is a different duration for every trajectory; and time passes at different rhythms according to place and speed. It is not directional; the difference between past and future does not exist in the elementary euqations of the world; its oritentation is merely a contigent aspect that appears when we look at things and neglect the details. In this blurred view, the past of the universe was in a curioysly “particular” state. The notion of the “present” does not work; in the vast universe there is nothing that we can resonably call “present”. The substratum that determines the duration of time is not an independent entity, different from the others that make up the world; it is an aspect of a dynamic field. It jumps, fluactuates, materializies only by interacting, and is not to be found beneath a minimum scale.

World is a network of events. The difference between things and events is that things persist in time; events have a limited duration.

A cloud above a mountatin is not a thing, it’s 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.

We understand the world by studying change, not by study things.We describe the world as it happens, not as it is. Newton’s mechanics, Maxwell’s equations, quantum mechanics and so on, tell us how events happen, not how things are. We understnad the world in its becoming, not in its being.

If by “time” we mean nothing more than happening, then everything is time. There is only that which exists in time.

People like us who believe in physics, know that the distinction between past, present and future is only a stubbornly persistent illusion.The grammar of many mordern language conjugated verbs in the “preset”, “past,” and “future” tense. (there are no present, past, future tense in chinese, brilliant).

There is a time to be born and a time to die, a time to weep and a time to dance, a time to killl and a time to heal. A time to destroy and a time to build.

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

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 clearning 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.

Our fear of death seems to me to be an error of evolution. Fearing the trasition, being afraid of death, is like being afraid of reality itself; like being afriad of the sun. Whatever for?

I think of death as skin to a well-earned resst. The sister of sleep. We can close our etes, rest. This all seems fair and beautiful to me. This is time.

My thoughts:

1. Research about entropy in information theory and probability point of view.
2. Why entropy is the reason for time flow from past to future and not vice versa. what is the cause and what is the result?
3. For everything that moves, time passes more slowly. If time slower, will the pointer of the clock run slower? what is the difference?
4. The mathematician study how things change, not of how they are. They will be about events, not thing. As for people, they are not who they are, but what their life has been.

Reference:

[1] “The order of time” by Carlo Rovelli