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Frank Visser, graduated as a psychologist of culture and religion, founded IntegralWorld in 1997. He worked as production manager for various publishing houses and as service manager for various internet companies and lives in Amsterdam. Books: Ken Wilber: Thought as Passion (SUNY, 2003), and The Corona Conspiracy: Combatting Disinformation about the Coronavirus (Kindle, 2020).

The Search for a Coherent Cosmos

A Layman's Overview of Contemporary Physics

Frank Visser / ChatGPT

Modern physics has entered a reflective age. A century after Einstein reshaped gravity and the quantum pioneers revealed the atom's uncanny behavior, the field remains both triumphant and unfinished. Its predictive power is unparalleled—GPS, lasers, semiconductors, and cosmology all depend on its equations—but its conceptual foundations are fractured.

At the heart of this tension lies a paradox: two theories that work beautifully apart but clash together. Quantum mechanics, governing the microscopic realm, is probabilistic and indeterminate. General relativity, governing the cosmic, is geometric and deterministic. When physicists try to apply both to the same situation—say, at the singularity of a black hole or the beginning of the universe—the mathematics breaks down.

The quest to reconcile these pillars has produced a diversity of approaches, each with its own metaphysical flavor. The most accessible guides to this ongoing story—Brian Greene, Sean Carroll, Carlo Rovelli, Thomas Hertog, and others—show that the frontier of physics today is as philosophical as it is mathematical.

1. The Legacy of Einstein and the Quantum Revolution

Before looking at their differences, it helps to recall the two great revolutions of 20th-century physics.

Einstein's general relativity (1915) revealed that gravity is not a force acting at a distance, as Newton believed, but the curvature of spacetime itself. Matter tells space how to curve; space tells matter how to move. The equations describe the cosmos on the grandest scales—galaxies, black holes, the expansion of the universe—and they have passed every observational test.

Quantum mechanics (1920s), by contrast, describes a jittery micro-world of uncertainty. Particles are also waves; outcomes are probabilistic; observation plays a mysterious role. This framework underlies all of modern chemistry and particle physics, yet it defies classical intuition.

Each theory works perfectly in its own domain. But try to describe what happens inside a black hole or at the Big Bang, where quantum effects and gravity are both extreme, and the equations refuse to cooperate. A deeper synthesis—often called quantum gravity—is needed. That search defines much of today's theoretical physics.

2. Brian Greene and the String Landscape

Among the most ambitious attempts at unification is string theory, and its most gifted popularizer is Brian Greene, author of The Elegant Universe and The Fabric of the Cosmos. String theory proposes that the universe's basic constituents are not point-like particles but tiny vibrating strings. Each mode of vibration corresponds to a different particle—like musical notes on a cosmic violin.

For string theory to be mathematically consistent, spacetime must have extra dimensions—typically ten or eleven in total. These extra dimensions are curled up at scales far smaller than atoms, invisible to current experiments but potentially explaining the variety of forces and particles we observe.

Over time, however, string theory's mathematical richness became both its glory and its problem. The equations allow a vast number of possible solutions, each corresponding to a universe with different physical constants. This “landscape” could contain as many as 10⁵⁰⁰ distinct possibilities—a multiverse.

Greene embraces this implication as a natural extension of modern cosmology: if inflationary theory already suggests countless expanding “bubble” universes, string theory provides the mathematical scaffolding for their diversity. The anthropic principle—that we observe this particular universe because it allows for observers like us—offers a possible explanatory bridge.

Critics, such as Lee Smolin and Sabine Hossenfelder, argue that the multiverse dissolves physics into metaphysics, since no other universes are observable in principle. Yet for Greene and his colleagues, the power of the mathematics and its ability to encompass both gravity and quantum fields justify continued exploration.

Underlying this position is a mathematical Platonism—the conviction that the universe is, at its core, mathematical. If the math works, reality will follow.

3. Sean Carroll and the Quantum Realists

Sean Carroll, a cosmologist and philosopher of science, takes a different path. Rather than starting with gravity, he begins with quantum foundations. In Something Deeply Hidden and The Biggest Ideas in the Universe, Carroll argues that quantum mechanics should be taken literally. The notorious “measurement problem”—the question of when and how a quantum wave collapses into a definite outcome—is, for him, a pseudo-problem created by our resistance to the theory's implications.

Carroll advocates the Everett or Many-Worlds Interpretation. Every quantum event with multiple possible outcomes actually realizes all of them, each in a separate branch of the universe. The wave function never collapses; it simply evolves deterministically according to the Schrödinger equation. What we call “probability” reflects our limited perspective as beings living in one branch.

This picture sounds extravagant, yet Carroll insists it's the simplest reading of quantum mechanics—no hidden variables, no special rules for observers. The cost is ontological, not mathematical: we must accept an ever-branching reality.

Carroll's naturalism is rigorous. He rejects appeals to consciousness or mysticism in explaining quantum weirdness. His broader vision ties the micro to the macro through emergence: complex phenomena like life, time's arrow, and even meaning arise naturally from the interplay of quantum laws and thermodynamics. The universe, in his view, is self-contained—no supernatural input required.

4. Carlo Rovelli and the Quantum of Space-Time

If Greene seeks unity through mathematical elegance and Carroll through quantum realism, Carlo Rovelli seeks it through a radical rethinking of space and time themselves.

Rovelli's program, loop quantum gravity (LQG), rejects the idea that space is a continuous backdrop. Instead, it proposes that spacetime is made up of discrete loops or “quanta” of geometry. These loops form a dynamic network—sometimes called a spin network—whose nodes and links encode the fundamental structure of space.

In this picture, the smooth fabric of spacetime described by Einstein is an emergent approximation, like water appearing continuous though it's made of molecules.

Even more provocative is Rovelli's treatment of time. In The Order of Time, he argues that time is not an absolute flow but a relational concept that emerges from interactions. There is no universal “now”—only local processes and correlations.

Philosophically, Rovelli's worldview is relational realism: things do not have intrinsic properties independent of their relations to others. A particle's position, energy, or even existence is defined only in relation to another system.

This marks a subtle but profound shift from both Newtonian substance metaphysics and the more abstract mathematical Platonism of string theory. For Rovelli, reality is not a set of objects but a web of events. The universe, he writes, is “a network of kisses between things.”

Though still lacking experimental confirmation, loop quantum gravity has provided intriguing theoretical results—such as a possible resolution of black-hole singularities and a finite minimum size for space. To its advocates, it remains a leaner, conceptually cleaner alternative to string theory.

5. Thomas Hertog and the Evolution of Laws

Thomas Hertog, who worked closely with Stephen Hawking in Hawking's later years, introduces a still more radical idea: that the laws of physics themselves have evolved.

In On the Origin of Time, Hertog revisits the famous “no-boundary” model Hawking proposed, where the universe has no singular beginning but rather a smooth, self-contained origin in imaginary time. Building on this, Hertog argues that the universe's early quantum state was not governed by fixed laws but by proto-laws that crystallized as the cosmos cooled and expanded.

In other words, physics itself has a history. The “timeless” mathematical laws we discover may be emergent regularities, not eternal truths. This echoes ideas from biology—an evolutionary, self-organizing cosmos where stability and complexity gradually arise.

Hertog's vision challenges the traditional image of physics as a description of timeless principles. Instead, it portrays a participatory universe whose rules co-emerge with the reality they describe. The boundary between physics and metaphysics begins to blur, though without abandoning empirical grounding.

If Greene is a Platonist and Rovelli a relational realist, Hertog might be called a cosmic historicist: for him, even the laws of nature are subject to evolution.

6. Other Currents: Information, Symmetry, and Emergence

Beyond these major figures, other currents flow through modern theoretical physics. Increasingly, many researchers view information—not matter or energy—as the most fundamental concept. Quantum entanglement, black-hole entropy, and the holographic principle all suggest that physical reality might be a manifestation of deeper informational relationships.

In this spirit, physicists like John Wheeler spoke of “it from bit”: the idea that the universe's fabric arises from binary choices, quantum yes-no events. Today, quantum information theory provides new mathematical tools to explore this intuition, linking computation, thermodynamics, and gravity in surprising ways.

Others, like Nima Arkani-Hamed, pursue the search for hidden geometric symmetries that might replace spacetime as the ultimate arena of physics. Concepts such as the “amplituhedron” hint that space and time themselves could be emergent shadows of deeper algebraic structures.

Still others—Lee Smolin, Sabine Hossenfelder, Roger Penrose—propose alternative unifications, from causal sets to twistor theory, each reflecting a unique compromise between mathematical ambition and empirical restraint.

7. A Spectrum of Philosophical Temperaments

Seen together, these approaches represent more than technical variations; they embody different philosophies of science:

This diversity is not a weakness but a sign of intellectual vitality. Physics today is less a single march toward unification than a polyphony of hypotheses, each illuminating different aspects of the cosmic riddle.

8. The Experimental Frontier

What keeps all these visions tethered to reality is experiment, however distant or indirect.

Gravitational wave detectors like LIGO and Virgo confirm Einstein's predictions and open new windows on black holes.

Cosmic microwave background measurements probe the universe's earliest moments.

Particle accelerators continue to test the Standard Model, while dark matter searches remind us how much remains unseen.

Quantum computers and simulators test the boundaries between quantum theory and classical reality.

Yet the energies required to probe quantum gravity directly may lie forever beyond human reach. Theoretical elegance and indirect evidence may be the best tools we have. As Rovelli quips, “Physics advances when we learn how to ask better questions.”

9. The Philosophical Edge

Underneath the equations lies an ancient question: What kind of reality does physics describe?

Is the universe a timeless mathematical object (Greene)? A seamless natural process branching endlessly (Carroll)? A network of relations without absolutes (Rovelli)? Or an evolving cosmos still inventing its own rules (Hertog)?

Each vision carries a different sense of meaning. Some see beauty in immutable symmetry; others in open-ended becoming. The old dream of a single “theory of everything” may give way to a more pluralistic picture, where physics becomes less a final answer and more a map of possible realities.

10. Conclusion: A Cosmos Still in Formation

The story of modern physics is no longer a straightforward progression toward certainty but a dance between clarity and mystery.

Einstein unified space and time; quantum theory dissolved solidity into probability; today's physicists are learning that even the laws themselves may be contingent, relational, or informational.

As the boundaries between physics, philosophy, and metaphysics blur, one truth remains: the universe continues to surprise us. Every advance deepens our wonder at the fact that the human mind—an outcome of cosmic evolution—can glimpse the architecture of the cosmos that made it.

In that sense, contemporary physics is not merely a technical enterprise but a profound human story: a testament to our curiosity, our fallibility, and our yearning for coherence in an unfinished universe.

Or, as Carlo Rovelli once put it:

“The world is not a collection of things. It is a collection of events, of happenings. We are among them.”