In Reality Is Not What It Seems: The Journey to Quantum Gravity, theoretical physicist Carlo Rovelli takes readers on a fascinating expedition through the evolution of physics, culminating in one of the most ambitious quests in modern science: the search for a theory of quantum gravity. With poetic clarity and philosophical insight, Rovelli reconstructs the way we’ve come to understand space, time, and the very nature of reality—arguing that reality, as we perceive it, is a shimmering veil behind which lies a profoundly unfamiliar world.
This essay explores the main themes of Rovelli’s work, covering the historical development of physics, the concept of quantum gravity, and how this search challenges our deepest assumptions about space, time, and existence itself.
The Legacy of Classical Physics
Rovelli begins by paying homage to the intellectual giants who laid the foundations of science. The ancient Greek philosopher Democritus postulated that everything is composed of tiny, indivisible atoms moving through the void—a remarkably prescient idea that resonates with modern particle physics. Fast forward to Isaac Newton, who revolutionized our understanding with his laws of motion and universal gravitation. Newtonian physics provided a deterministic and mechanistic view of the universe, where time and space were absolute, and events unfolded in a predictable manner.
Yet, as Rovelli points out, this classical worldview began to crack with the advent of James Clerk Maxwell’s equations of electromagnetism, and later, Albert Einstein’s theories of relativity, which dramatically altered our notions of time and space.
The Relativity Revolution
Einstein’s special relativity in 1905 destroyed the idea of universal time. It showed that time is relative to the observer’s motion. Then, with general relativity in 1915, Einstein proposed that gravity is not a force between objects, as Newton thought, but rather a manifestation of the curvature of spacetime caused by mass and energy.
In this new model, space and time are not passive backgrounds—they are dynamic entities that bend and stretch. Time slows down near a massive object; light follows curved paths through warped space. Einstein’s equations not only explained the orbit of Mercury and predicted black holes but also laid the groundwork for our modern understanding of the cosmos.
Still, as Rovelli highlights, general relativity is a classical theory. It does not take into account the weird and probabilistic nature of quantum mechanics, which governs the microscopic world.
The Quantum Challenge
Quantum mechanics, developed in the early 20th century by pioneers like Planck, Heisenberg, Schrödinger, and Bohr, revealed a universe where particles behave like waves, exist in superpositions, and cannot be precisely known in terms of both position and momentum (Heisenberg’s uncertainty principle).
Quantum theory introduced a new language of reality—one of probabilities, non-locality, and entanglement. Yet while it has been stunningly successful in explaining phenomena at the atomic and subatomic levels, it remains fundamentally incompatible with general relativity.
General relativity treats spacetime as smooth and continuous. Quantum mechanics suggests that, at the smallest scales, reality is grainy, fluctuating, and uncertain. Bringing these two pillars of physics together has been one of the greatest unsolved challenges in science: the search for a theory of quantum gravity.
Loop Quantum Gravity: Rovelli’s Answer
Rovelli’s major contribution to physics is a theory called Loop Quantum Gravity (LQG). Unlike string theory, which seeks unification through tiny vibrating strings in higher dimensions, LQG attempts to quantize spacetime itself using principles from quantum mechanics and general relativity.
In LQG, space is not continuous. Instead, it is made up of tiny, discrete units—like pixels on a screen. These fundamental building blocks of space are loops of quantum fields, forming an intricate network known as a spin network. Over time, these networks evolve in what Rovelli calls a spinfoam.
In this framework, time itself is not fundamental. It emerges from interactions between these quantum loops. There is no universal “now.” Rather, time is relational—something that emerges from the way physical systems interact. This idea aligns with the philosophical view known as relationalism, which Rovelli defends throughout the book.
Time, Space, and Reality
One of the most radical implications of quantum gravity is that time may not exist as we normally understand it. This is deeply counterintuitive because our daily experience is steeped in temporal flow: past, present, and future. But at the most fundamental level, according to LQG, events are not ordered by a universal ticking clock. Instead, they are related by cause and effect in a web of interactions.
Similarly, space is not an empty container in which things happen—it is itself a dynamic structure that emerges from quantum events. What we call “reality” is not a fixed stage but a network of interactions. Particles, fields, and even the geometry of spacetime are not substances but processes—temporary nodes in a vast relational structure.
This leads to an almost Buddhist view of the world: nothing exists independently; everything arises from interactions. There are no absolute positions, no static substances—only relationships and change.
Philosophy and Physics Intertwined
Rovelli’s writing is notable not just for its scientific clarity but also for its philosophical depth. He draws on the ideas of Plato, Aristotle, Leibniz, and even Buddhist thinkers to reflect on the implications of modern physics.
He challenges the realist view that the world exists exactly as we perceive it. Instead, he adopts a relational view of the universe: reality is not made of things but of their interactions. The “self” is not a separate observer of the world but part of the web of relationships that constitutes it.
This philosophical stance aligns well with developments in quantum gravity, where traditional concepts like space, time, and matter dissolve at the Planck scale (10^-35 meters). Here, reality is not what it seems—it is stranger, more dynamic, and more interconnected than our minds can intuitively grasp.
Implications for the Future
If loop quantum gravity is correct, it could help us solve many outstanding problems in theoretical physics. It could explain what happens at the center of black holes or at the Big Bang, where classical theories break down. It might offer insights into dark energy, quantum cosmology, and the origin of the universe itself.
Moreover, quantum gravity could revolutionize technology, just as quantum mechanics did in the 20th century with transistors, lasers, and computers. Although still speculative, future applications could include quantum computing based on space-time architecture or new energy systems grounded in quantum gravitational fields.
Conclusion
Reality Is Not What It Seems is not just a physics book—it is a profound meditation on the nature of existence. Carlo Rovelli invites us to question the assumptions we hold about time, space, and substance. By weaving together history, science, and philosophy, he offers a compelling narrative of how humanity has peeled back the layers of illusion to get closer to the underlying truth of the universe.
Quantum gravity, especially as conceived through loop quantum gravity, paints a picture of a world made not of things but of events and relationships. At its deepest level, the universe is a tapestry of interwoven processes. Time is not linear; space is not smooth. And what we think of as reality is but a limited view of a far more intricate and astonishing cosmos.
As Rovelli eloquently writes, “We are made of the same stuff of which stars are made. We are born from the same process that forms galaxies. We are part of this world.” And understanding that world—not as it seems, but as it is—remains one of the greatest adventures of the human mind.
