Carlo Rovelli’s Radical View: Why Reality Exists Only Through Relations

The Physicist and the Puzzle: Redefining Quantum Reality

Carlo Rovelli, the renowned theoretical physicist and a leading figure in Loop Quantum Gravity (LQG) research, is perhaps best known to the public for his ability to distill complex science into poetic prose. Yet, within the physics community, Rovelli champions a truly radical departure from conventional thinking: Relational Quantum Mechanics (RQM). This interpretation of quantum theory suggests that the properties of the universe are not absolute, but exist only in relation to an observer or another physical system.

In a world where most physicists adhere to the standard (Copenhagen) interpretation or the Many-Worlds theory, Rovelli’s RQM offers a compelling, yet challenging, solution to quantum mechanics’ most persistent headache: the measurement problem. His perspective shifts the focus of reality from static ‘things’ with intrinsic properties to a dynamic, ever-changing network of ‘events’ and interactions.

Relational Quantum Mechanics: Properties Are Not Absolute

Relational Quantum Mechanics (RQM), first proposed by Rovelli in the mid-1990s, fundamentally challenges the classical notion that physical systems possess definite, objective properties independent of observation. Instead, RQM asserts that the state of a quantum system is only meaningful relative to another system—the observer.

To understand this, consider the core concept of superposition. Before measurement, a quantum particle (like an electron) exists in a mixture of all possible states simultaneously. The standard view struggles with how and why this superposition ‘collapses’ into a single definite state when measured by a conscious observer.

RQM eliminates the collapse problem entirely.

In Rovelli’s view, the collapse is not a physical change in the universe but a change in the information available to the observer. If System A measures System B, the state of B becomes definite relative to A. However, for a third system, C, which has not interacted with B, B remains in a superposition. All three descriptions—A’s, B’s, and C’s—are equally valid within their respective relational contexts.

The Pigeon Analogy

Rovelli often uses simple, everyday examples to illustrate this profound shift. He once described watching a pigeon bob its head as it walks. This action is not arbitrary; the pigeon bobs its head to stabilize its visual perception. The head movement is a necessary relational action required for the pigeon to perceive a stable, classical world. The stability of the world is not an intrinsic property of the world itself, but a consequence of the interaction between the pigeon’s visual system and its environment.

Key tenets of RQM:

• Relativity of States: The quantum state of a system is always relative to another system. There is no absolute, universal state description.
• No Universal Observer: RQM removes the need for a privileged, non-physical observer (like human consciousness) to cause wave function collapse. Any physical interaction between two systems constitutes a ‘measurement.’
• Information as Fundamental: The theory is deeply rooted in the idea that physical reality is fundamentally about the information systems have about each other.

Solving the Measurement Problem

The measurement problem is arguably the most significant conceptual hurdle in quantum mechanics. It asks: How does the smooth, continuous evolution of the wave function (governed by the Schrödinger equation) transition into the discrete, definite outcomes we observe in the classical world?

Standard interpretations offer difficult answers:

1. Copenhagen Interpretation: Postulates that observation by a classical apparatus (or consciousness) causes an instantaneous, non-physical ‘collapse’ of the wave function. This introduces an arbitrary division between the quantum and classical worlds.
2. Many-Worlds Interpretation (MWI): Suggests that the wave function never collapses; instead, every possible outcome of a measurement is realized in a different, branching universe. This solves the collapse problem but introduces an infinite number of unobservable realities.

Rovelli argues that RQM provides a cleaner solution by dissolving the boundary between the observer and the observed. Since every interaction is a measurement, and every state is relative, the concept of a universal, absolute collapse becomes unnecessary.

“The world is not made of things, but of relations, of interactions, of events. The properties of a system are not intrinsic; they are only defined when they interact with something else.”

This perspective aligns with the principles of General Relativity, which already taught us that concepts like simultaneity and distance are relative to the observer’s frame of reference. RQM extends this relativity to all physical properties, including quantum states.

The World as a Network of Events, Not Static Things

Beyond solving the measurement problem, RQM offers a profound philosophical shift regarding the nature of reality itself. Rovelli suggests we must abandon the notion of the universe being composed of static, enduring things and embrace the idea that it is composed of events.

In classical physics, a particle maintains its identity and properties over time, even when unobserved. In RQM, properties only manifest during an interaction—an event. When the interaction ceases, the specific property (like position or momentum) relative to that observer ceases to be definite.

This view is highly compatible with Rovelli’s primary field, Loop Quantum Gravity (LQG), which attempts to quantize gravity. LQG replaces the smooth spacetime continuum of Einstein with discrete, interconnected loops—a structure that is inherently relational and dynamic.

Implications for Time and Identity

If reality is a succession of events, the concept of time itself is altered. Time is not a universal flow but a measure of change and interaction. For Rovelli, the idea of enduring identity is an illusion created by the persistence of certain patterns of interaction.

Consider the following comparison of worldviews:

By emphasizing events and relations, RQM provides a framework where quantum mechanics is inherently complete, without needing external postulates (like collapse) or unobservable entities (like parallel universes).

The Philosophical Weight of Relationalism

Rovelli’s work has significant philosophical implications, aligning him with thinkers who emphasize process and change over substance and permanence. His perspective suggests that the subjective experience of reality—the stability and definiteness we perceive—is a result of the specific, highly complex relational network we are embedded in.

For a general audience, the most challenging aspect of RQM is accepting the lack of an objective, ‘God’s eye view’ of the universe. If the properties of a system are different for different observers (and those differences are not errors, but fundamental truths), then the concept of a single, universal reality dissolves.

However, Rovelli argues this is simply physics catching up to philosophy and our own lived experience. We already accept that velocity is relative; RQM simply extends this relativity to all physical attributes.

Why RQM Matters in 2025

As theoretical physics continues to grapple with unifying quantum mechanics and gravity, interpretations like RQM gain traction because they offer conceptual clarity. RQM provides a consistent, self-contained view of quantum mechanics that is fully compatible with the principles of special relativity, which emphasizes the relativity of frames of reference.

Furthermore, RQM is testable—not necessarily through direct experiments on the nature of reality, but through its potential to simplify and clarify quantum gravity theories like LQG, leading to new, verifiable predictions about the structure of spacetime at the smallest scales.

Key Takeaways: Rovelli’s Vision of Existence

Carlo Rovelli’s Relational Quantum Mechanics offers a compelling and elegant alternative to the standard interpretations of quantum theory, prioritizing interaction and perspective over intrinsic properties.

• Reality is Relational: A system’s properties are only defined in relation to another physical system (the observer).
• The Universe is Events: The fundamental constituents of reality are not static ‘things’ but dynamic ‘events’—interactions that define properties temporarily.
• No Absolute Collapse: The wave function collapse is not a universal physical process but a change in information relative to the specific observer involved in the interaction.
• Consistency with Relativity: RQM aligns quantum theory with the core principle of relativity, where different observers have equally valid, yet different, descriptions of the same phenomena.
• Philosophical Depth: This interpretation challenges the deeply ingrained human intuition of an objective, observer-independent reality, suggesting that existence is fundamentally a network of perspectives.

Conclusion: A Physics of Perspective

Carlo Rovelli’s radical perspective is a forceful reminder that the foundational laws of physics are far from settled. By advocating for Relational Quantum Mechanics, Rovelli pushes the boundaries of how we define existence, suggesting that the universe is less like a fixed stage and more like an intricate, ever-changing dance of interactions. His work provides not just a theoretical framework for quantum gravity, but a profound philosophical lens through which to view our place in a universe where everything is defined by its relationship to everything else. This relational view offers a path forward for physicists seeking a unified theory, grounding the bizarre nature of the quantum world in the familiar logic of relativity.