Rovelli is a quantum physicist, who specializes in quantum gravity. On the side, he writes pop-science books. This one is in his wheelhouse. His preferred quantum model is not the Copenhagen Interpretation favored by Bohr and Heisenberg, though they were on the right track focussing on measurement. Bohr wrote, “Whereas in classical physics the interaction between an object and the measuring apparatus can be overlooked—or if necessary can be taken into account and compensated for—in quantum physics this interaction is an inseparable part of the phenomenon.” Rovelli’s model is not Everett’s Many-Worlds or David Bohm’s Pilot Waves, though he helpfully explains and extracts from both, as well. Rovelli’s conception is strange, beautiful, and mystical, while being, obviously, still grounded in hard science. “The keystone of the ideas in this book, is the simple observation that scientists, and their measuring instruments as well, are all part of nature. What quantum theory describes, then, is the way in which one part of nature manifests itself to any other single part of nature…. To understand nature, we must focus on these interactions rather than on isolated objects.” Rovelli is blunt about how his conception of quantum physics necessarily modifies his view of reality, “The discovery of quantum theory, I believe, is the discovery that the properties of any entity are nothing other than the way in which that entity influences others. It exists only through its interactions.”
Rovelli begins, “Quantum theory predicts granularity, quantum leaps, photons and all the rest, on the basis of adding a single equation of eight characters to classical physics. An equation which says that to multiply position by speed is different from multiplying speed by position. The opaqueness is complete.” Rovelli’s world is one that is fundamentally based on interaction and subjectivity. Quantum mechanics “describes the elementary and universal grammar of physical reality underlying not just laboratory observations but every type and instance of interaction…. Any interaction between two physical objects can be seen as an observation.” This requires a new way of conceptualizing reality. “The properties of an object are the way in which it acts upon other objects; reality is this web of interactions. Instead of seeing the physical world as a collection of objects with definite properties, quantum theory invites us to see the physical world as a net of relations. Objects are its nodes…. There are no properties outside of interactions…. If the electron is not interacting, there are no properties. This is a radical leap. It is equivalent to saying that everything consists solely of the way in which it affects something else. When the electron does not interact with anything, it has no physical properties. It has no position; it has no velocity.”
The relational nature of reality has consequences. Objectivity is dispensed with. Everything is subjective. “No universal set of facts exist…. Facts relative to one observer are not facts relative to another. It is a shining example of the relativity of reality…. The joint properties of two objects exist only in relation to a third. To say that two objects are correlated means to articulate something with regard to a third object: the correlation manifests itself when the two correlated objects both interact with this third object…. The existence of a third object that interacts with both the systems is necessary to give reality to the correlations. Everything that manifests itself does so in relation to something…. Entanglement is not a dance for two partners, it is a dance for three…. Entanglement is therefore far from being a rare phenomenon that occurs only in particular situations: it is what happens, generically, in an interaction when this interaction is considered in relation to a system external to it.”
The inescapability of the subjectivity of nature is hard to fully wrap one’s head around. “If the world consists of relations, then no description is from outside it. The descriptions of the world are, in the ultimate analysis, all from inside. They are all in the first person…. If we imagine the totality of things, we are imagining being outside the universe, looking at it from out there. But there is no “outside” to the totality of things. The external point of view is a point of view that does not exist…. The world is this reciprocal reflection of perspectives…. The relational perspective shows that physics is always a first-person description of reality, from one perspective.”
In conclusion, Rovelli dips his head into dualism and consciousness, considering mind and matter. For Rovelli, everything is relative. “If we think in terms of processes, events, in terms of relative properties, of a world of relations, the hiatus between physical phenomena and mental phenomena is much less dramatic. It becomes possible to see both as natural phenomena generated by complex structures of interactions…. At the physical level, the world can be seen as a web of reciprocal information.” The subjective nature of reality is, once again, fundamental. “The best description of reality that we have found is in terms of events that weave a web of interactions. “Entities” are nothing other than ephemeral nodes in this web. Their properties are not determined until the moment of these interactions; they exist only in relation to something else…. Every vision is partial. There is no way of seeing reality that is not dependent on perspective—no point of view that is absolute and universal.”
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