Carlo Rovelli

In nature, variables are not independent; for instance, in any magnet, the two ends have opposite polarities. Knowing one amounts to knowing the other. So we can say that each end “has information” about the other. There is nothing mental in this; it is just a way of saying that there is a necessary relation between the polarities of the two ends. We say that there is "relative information" between two systems anytime the state of one is constrained by the state of the other. In this precise sense, physical systems may be said to have information about one another, with no need for a mind to play any role. Such "relative information" is ubiquitous in nature: The color of the light carries information about the object the light has bounced from; a virus has information about the cell it may attach; and neurons have information about one another. Since the world is a knit tangle of interacting events, it teams with relative information. When this information is exploited for survival, extensively elaborated by our brain, and maybe coded in a language understood by a community, it becomes mental, and it acquires the semantic weight that we commonly attribute to the notion of information. But the basic ingredient is down there in the physical world: physical correlation between distinct variables. The physical world is not a set of self-absorbed entities that do their selfish things. It is a tightly knitted net of relative information, where everybody’s state reflects somebody else’s state. We understand physical, chemical, biological, social, political, astrophysical, and cosmological systems in terms of these nets of relations, not in terms of individual behavior. Physical relative information is a powerful basic concept for describing the world. Before “energy,” “matter,” or even “entity.”

His popular science book, Seven Brief Lessons on Physics, was originally published in Italian in 2014. It has been translated into 41 languages and has sold over a million copies worldwide. In 2019, he was included by Foreign Policy magazine in a list of 100 most influential global thinkers.

Rovelli discusses his religious views in several articles and in his book on Anaximander. He argues that the conflict between rational/scientific thinking and structured religion may find periods of truce ("there is no contradiction between solving Maxwell's equations and believing that God created Heaven and Earth"), but it is ultimately unsolvable because (most) religions demand the acceptance of some unquestionable truths while scientific thinking is based on the continuous questioning of any truth. Thus, for Rovelli the source of the conflict is not the pretense of science to give answers — the universe, for Rovelli, is full of mystery and a source of awe and emotions — but, on the contrary, the source of the conflict is the acceptance of our ignorance at the foundation of science, which clashes with religions' pretense to be depositories of certain knowledge.

Rovelli won the second prize in the 2013 FQXi contest "It From Bit or Bit From It?" for his essay about "relative information". His paper, Relative Information at the Foundation of Physics, discusses how "Shannon’s notion of relative information between two physical systems can function as [a] foundation for statistical mechanics and quantum mechanics, without referring to subjectivism or idealism...[This approach can] represent a key missing element in the foundation of the naturalistic picture of the world." In 2017, Rovelli elaborated further upon the subject of relative information, writing that:

In his 2004 book, Quantum Gravity, Rovelli developed a formulation of classical and quantum mechanics that does not make explicit reference to the notion of time. The timeless formalism is used to describe the world in the regimes where the quantum properties of the gravitational field cannot be disregarded. This is because the quantum fluctuation of spacetime itself makes the notion of time unsuitable for writing physical laws in the conventional form of evolution laws in time.

Carlo Rovelli is an Italian theoretical physicist and writer who has worked in Italy, the United States and, since 2000, in France. He works mainly in the field of quantum gravity and is a founder of loop quantum gravity theory. He has also worked in the history and philosophy of science. He collaborates with several Italian newspapers, including the cultural supplements of the Corriere della Sera, Il Sole 24 Ore and La Repubblica.

In 1994, Rovelli introduced the relational interpretation of quantum mechanics, based on the idea that the quantum state of a system must always be interpreted relative to another physical system (like the "velocity of an object" is always relative to another object, in classical mechanics). The idea has been developed and analyzed in particular by Bas van Fraassen and by Michel Bitbol. Among other important consequences, it provides a solution of the EPR paradox that does not violate locality.

This position led him to face the following problem: if time is not part of the fundamental theory of the world, then how does time emerge? In 1993, in collaboration with Alain Connes, Rovelli proposed a solution to this problem called the thermal time hypothesis. According to this hypothesis, time emerges only in a thermodynamic or statistical context. If this is correct, the flow of time is an illusion, one deriving from the incompleteness of knowledge.

In 1988, Rovelli, Lee Smolin and Abhay Ashtekar introduced a theory of quantum gravity called loop quantum gravity. In 1995, Rovelli and Smolin obtained a basis of states of quantum gravity, labeled by Penrose's spin networks, and using this basis they were able to show that the theory predicts that area and volume are quantized. This result indicates the existence of a discrete structure of space at a very small scale. In 1997, Rovelli and Michael Reisenberger introduced a "sum over surfaces" formulation of theory, which has since evolved into the currently covariant "spinfoam" version of loop quantum gravity. In 2008, in collaboration with Jonathan Engle and Roberto Pereira, he has introduced the spin foam vertex amplitude which is the basis of the current definition of the loop quantum gravity covariant dynamics. Loop theory is today considered a candidate for a quantum theory of gravity. It finds applications in quantum cosmology, spinfoam cosmology and quantum black hole physics.

In 1981, Rovelli graduated with a BS/MS in physics from the University of Bologna, and in 1986 he obtained his PhD at the University of Padova, Italy. Rovelli refused military service, which was compulsory in Italy at the time, and was therefore briefly detained in 1987. He held postdoctoral positions at the University of Rome, University of Trieste and at Yale University. Rovelli was on the faculty of the University of Pittsburgh from 1990 to 2000. He currently works in the Centre de Physique Théorique de Luminy of Aix-Marseille University. He has also held the post of affiliated professor in the Department of History and Philosophy of Science of the University of Pittsburgh.

Carlo Rovelli was born in Verona, Italy, on 3 May 1956. He attended the Liceo Classico Scipione Maffei in Verona. In the 1970s, he participated in the student political movements in Italian universities. He was involved with the free political radio stations Radio Alice in Bologna and Radio Anguana in Verona, which he helped found. In conjunction with his political activity, he was charged, but later released, for crimes of opinion related to the book Fatti Nostri, which he co-authored with Enrico Palandri, Maurizio Torrealta, and Claudio Piersanti.