Seven Brief Lessons on Physics

by Carlo Rovelli

The sun bends space around itself, and Earth does not turn around it because of a mysterious force but because it is racing directly in a space that inclines, like a marble that rolls in a funnel. There are no mysterious forces generated at the center of the funnel; it is the curved nature of the walls that causes the marble to roll. Planets circle around the sun, and things fall, because space curves.

If a person who has lived at sea level meets up with his twin who has lived in the mountains, he will find that his sibling is slightly older than he. And this is just the beginning.

a glimpse of reality, a little less veiled than our blurred and banal everyday view of it. A reality that seems to be made of the same stuff that our dreams are made of, but that is nevertheless more real than our clouded, quotidian dreaming.

These simple and clear lines are the real birth certificate of quantum theory. Note the wonderful initial “It seems to me . . . ,” which recalls the “I think . . .” with which Darwin introduces in his notebooks the great idea that species evolve, or the “hesitation” spoken of by Faraday when introducing for the first time the revolutionary idea of magnetic fields. Genius hesitates.

each element corresponds to one solution of the main equation of quantum mechanics. The whole of chemistry emerges from a single equation.

It’s as if God had not designed reality with a line that was heavily scored but just dotted it with a faint outline.

Or does it mean, as it seems to me, that we must accept the idea that reality is only interaction?

Quantum mechanics and experiments with particles have taught us that the world is a continuous, restless swarming of things, a continuous coming to light and disappearance of ephemeral entities. A set of vibrations, as in the switched-on hippie world of the 1960s. A world of happenings, not of things.

The difference between past and future exists only when there is heat. The fundamental phenomenon that distinguishes the future from the past is the fact that heat passes from things that are hotter to things that are colder.

Do we also consist only of quanta and particles? If so, then from where do we get that sense of individual existence and unique selfhood to which we can all testify? And what then are our values, our dreams, our emotions, our individual knowledge? What are we, in this boundless and glowing world?

Our moral values, our emotions, our loves are no less real for being part of nature, for being shared with the animal world, or for being determined by the evolution that our species has undergone over millions of years. Rather, they are more valuable as a result of this: they are real. They are the complex reality of which we are made. Our reality is tears and laughter, gratitude and altruism, loyalty and betrayal, the past that haunts us and serenity. Our reality is made up of our societies, of the emotion inspired by music, of the rich intertwined networks of the common knowledge that we have constructed together. All of this is part of the self-same “nature” that we are describing. We are an integral part of nature; we are nature, in one of its innumerable and infinitely variable expressions. This is what we have learned from our ever-increasing knowledge of the things of this world.