Quotes from Carlo Rovelli

Democritus himself, who had placed empty space at the basis of his world where atoms course, certainly wasn't crystal clear on the issue: he wrote that empty space is something "between being and non-being":

I am this long ongoing novel. My life consists of it. 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 as I was yesterday. To understand ourselves means to reflect on time. But to understand time, we need to reflect on ourselves.

The possibility of predicting something in the future obviously improves our chances of survival, and consequently, evolution has selected the neural structures that allow it. We are the result of this selection. This being between past and future events is central to our mental structure. This, for us, is the flow of time.

information is the measure of the number of possible alternatives for something. For example, if I throw a die, it can land on one of six faces.

For Plato, forms exist by themselves, in an ethereal ideal world of forms, a world of "ideas." The idea of a horse exists prior to and independently of any actual horse. For Plato, a real horse is nothing but a pale reflection of the idea of a horse. The atoms that make up the horse count for little: what counts is the "horseness," the abstract form.

This is the flow of time familiar from our experience. It is inside there that it nestles. Inside of us. The utterly crucial presence of traces of the past in our neurons. Proust could not be more explicit on this matter. Writing in the first book, "Reality is formed only by memory" and memory in its turn is a collection of traces-an indirect product of the disordering of the world.

Our moral values, our emotions, our lives are no less real for being part of nature, for being shared with the animal world, or for being determined by the evolution which our species has undergone over millions of years. Rather, they are more valuable as a result of this: they are real

Physics opens windows through which we see far into the distance. What we see does not cease to astound us. We realize that we are full of prejudices and that our intuitive image of the world is partial, parochial, inadequate

This is also true from a methodological point of view: a scientist orients his own research on the basis of epistemological ideas. He might be more or less aware of them. Very often to be aware of your own assumptions is far better than to be guided by methodological prejudices of which you are unaware.

The difference between past and future, between cause and effect, between memory and hope, between regret and intention . . . in the elementary laws that describe the mechanisms of the world, there is no such difference.

I think that the obscurity of the theory is not the fault of quantum mechanics but is rather due to the limited capacity of our imagination. When we try to "see" the quantum world, we are rather like moles used to living underground, to whom someone is trying to describe the Himalayas. Or like the men imprisoned at the back of Plato's cave.

Boltzmann was not taken seriously. At the age of fifty-six, in Duino, near Trieste, he committed suicide. Today he is considered one of the geniuses of physics.

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.

Therefore, the first meaning of quantum mechanics is the existence of a limit to the information that can exist within a system: a limit to the number of distinguishable states in which a system can be. This limitation upon infinity, this granularity of nature glimpsed by Democritus, is the first central aspect of the theory. Planck's constant h measures the elementary scale of this granularity.

Remember that a key result of quantum mechanics is precisely the fact that information is finite. The number of alternative results that we can obtain measuring a physical system* is infinite in classical mechanics; but thanks to quantum theory, we have understood that, in reality, it is finite. Quantum mechanics can be understood as the discovery that information in nature is always finite.

Books contain our history; our brains swarm with memories.

The solidity of the classical vision of the world is nothing other than our own myopia. The certainties of classical physics are just probabilities. The well-defined and solid picture of the world given by the old physics is an illusion.

Any description of a system is therefore always a description of the information a system has about another system, that is to say, the correlation between the two systems. The

And it's here that Einstein's extraordinary stroke of genius occurs, one of the greatest flights in the history of human thinking: what if the gravitational field turned out actually to be Newton's mysterious space? What if Newton's space was nothing more than the gravitational field? This extremely simple, beautiful, brilliant idea is the theory of general relativity.

The entire formal structure of quantum mechanics can be in large measure expressed in two simple postulates:1 The relevant information in any physical system is finite. You can always obtain new information on a physical system.

What role do we have as human beings who perceive, make decisions, laugh, and cry, in this great fresco of the world as depicted by contemporary physics?

We are for ourselves in large measure what we see and have seen of ourselves reflected back to us by our friends, our loves, and our enemies.

Only where there is heat is there a distinction between past and future.

This reads: "Delta S is always greater than or equal to zero," and we call this "the second principle of thermodynamics