Helgoland

Quantum mechanics, born from Werner Heisenberg’s insights, underpins modern technology yet remains conceptually enigmatic. Carlo Rovelli explores its interpretations, advocating for the relational interpretation. This view posits that reality consists of interactions and events rather than permanent, isolated substances. The theory suggests a reality so subtle it "almost seems not to exist," challenging the classical notion of objective reality.

Heisenberg revolutionized physics by focusing on observable quantities, using matrices to describe atomic behavior and abandoning fixed electron paths. Schrödinger later proposed wave mechanics, representing electrons as waves. Max Born reconciled these by interpreting the wave function as probability, introducing fundamental indeterminacy. The concept of quanta, discrete energy packets identified by Planck and Einstein, highlights nature's granularity, governed by Planck’s constant.

Quantum mechanics reveals phenomena like superposition, where objects exist in contradictory states until observed, as illustrated by Schrödinger’s cat. Born’s probability interpretation of the wave function introduces fundamental indeterminacy. The granularity of nature, through quanta, implies energy is transmitted in discrete packets, challenging classical continuous views and replacing fixed trajectories.

Various interpretations attempt to resolve the wave function's mystery, including Many Worlds (infinite parallel realities), Hidden Variables (unobservable guides), and Physical Collapse (spontaneous wave function collapse). An alternative, QBism, views the wave function as an epistemic tool reflecting observer knowledge. Rovelli critiques these, proposing that science focuses on relations rather than an external observer or substance.

The classical view of a predictable world of particles was disrupted by quantum theory, requiring a constant questioning of concepts. Rovelli proposes that quantum theory describes how every object manifests to another, forming a dense web of interactions. Properties of an object are inseparable from these interactions; without interaction, a system has no determined properties. This leads to the radical idea that facts are relative to specific systems.

Entanglement describes how distant objects maintain a connection defying classical physics, with correlated features not predetermined. The relational perspective resolves this by stating properties only exist relative to an observer. Correlations become real when a third system interacts to compare entangled particles, emphasizing that there are no universal facts, only relative ones. This highlights the foundational role of relations.

Information is a physical correlation between variables. Quantum theory postulates finite maximal information and the possibility of new information, explaining the uncertainty principle. Contextuality—the understanding that objects don't possess independent states outside interactions—is central. Rovelli argues a naturalistic view sees properties as contextual and relational, moving away from the idea of substance towards a reality defined by connections and events.

Quantum mechanics redefines matter as a swarming web of interactions, narrowing the perceived gap between objective matter and subjective experience. Meaning emerges from relevant relative information, providing a physical link from organisms to their environment. By reinterpreting the self as an integrated process and matter as a network of relations, subjectivity is seen as a natural manifestation of organized complexity within an interconnected world.

Rovelli advocates for naturalism, where philosophy adapts to scientific discovery, echoing Bohr’s insight that phenomena descriptions must include experimental arrangements. This leads to the conclusion that an object's unambiguous description includes its interactors, as properties are contextual and relational. He draws parallels with Nagarjuna’s Buddhist philosophy of emptiness (shunyata), suggesting everything exists dependently, aligning with a web of interdependence.

Quantum decoherence explains why quantum interference is absent in macroscopic objects. The wave function is clarified as a conceptual tool for calculation, not a physical entity. Rovelli critiques other interpretations like Many Worlds and hidden variables, reinforcing that variables like position and velocity lack determined values outside of interaction. He highlights Ernst Mach’s influence on relative motion and the relevance of Bogdanov's holistic perspective.