The Information-Theoretic Universe

Information seems to be an intangible and contextual concept, more relevant to philosophy than physics. Yet, surprisingly, it appears to reside at the very foundations of reality.

In the following, an overview of the still unfolding information-theoretic paradigm shift in physics is presented¹.

Midjourney / Prompt: “surrealistic complex network in which the nodes are hexagons.”

Information is Physical

• Landauer's principle shows how erasing information increases entropy by dissipating heat. Notably, for reversible manipulations of information, this is not the case.
• Information can be converted to energy. The inspiration for the experiments demonstrating this possibility came from Maxwell's demon, an information-theoretic puzzle emerging in the early days of the formulation of thermodynamics. Landauer's principle was crucial in solving the apparent paradox.

Shannon's Information Theory

• The notion of information is formally related to thermodynamics. Colloquially, information measures order, and entropy measures disorder.
• Information is quantized as binary digits or bits. Symbolically, represented by 0 and 1.
• Every aspect of today's digital information technology depends on information theory.

Computation

• Information processing is achieved by the flipping of bits.
• The history of computation includes the ancient Greek Antikythera mechanism, Blaise Pascal, Gottfried Wilhelm Leibniz, Charles Babbage, Ada Lovelace, Norbert Wiener, Konrad Zuse, Claude Shannon, and Alan Turing.
• Kurt Gödel's mathematical incompleteness, extended by Gregory Chaitin, finds its computational counterpart in the halting problem.
• Computation is a prime example implementing the principle of the simplicity of complexity. Seemingly simple programs have the power to generate great complexity. Think of fractals. Stephen Wolfram was among the first to point out this consequential fact of reality.

Quantum Information

• A qubit is a quantum superposition of the states 0 and 1. Every elementary particle can encode one qubit, for instance, as spin-up and spin-down states.
• As a consequence, any measurement performed in quantum mechanics is an interrogation of nature, yielding a yes/no, or 0/1 answer. In other words, when a superposed qubit is observed, it unveils one bit of classical information.
• The history of quantum information began with the no-cloning theorem, inspired by the work of a group of hippie physicists at the University of California, Berkeley, dabbling in psychedelics, Eastern mysticism, and parapsychology.
• Today, the "second quantum revolution" is defined by technological developments enabled by quantum information and quantum computing, including quantum teleportation and entanglement. It began unfolding towards the end of the last century.
• Quantum information has inspired new approaches to understanding quantum mechanics. The quantum world appears less puzzling when viewed from an information-theoretic perspective. Indeed, QBism and relational quantum mechanics are two novel interpretations of quantum mechanics that are encouraged by quantum information.
• The 2022 physics Nobel prize was related to quantum information, namely in the context of entanglement. Anton Zeilinger, one of the three awardees, once exclaimed: “What I believe but cannot prove is that quantum physics requires us to abandon the distinction between information and reality.”
• Quantum information cannot be destroyed. It is a fundamental conserved quantity like energy or matter.

Quantum Computing

• Historically, Richard Feynman sparked the initial interest in quantum computers in 1981. Four years later, David Deutsch showed how entangled qubits could unlock computational powers that are unattainable for classical computers.
• As quantum mechanics is conceptually impossible to understand, so is quantum computing, and much written about it is wrong.
• The theoretical computer scientist Scott Aaronson explains that the art of quantum computing is to "choreograph a pattern of constructive and destructive interference" of superpositions yielding the right answer.
• Seth Lloyd understands the entire universe as a quantum computer. When elementary particles interact, they exchange information and thus compute. To this day, the universe can have performed no more than 10¹²⁰ logical operations on 10⁹⁰ bits. Moreover, any quantum simulation is not really that different from what it is simulating.
• Quantum computers are currently still severely restricted by their capacity to error-correct, an essential ingredient of any digital information processing.

Holography

• Stephen Hawking discovered that black holes radiate thermal energy, leading to black hole thermodynamics.
• Jacob Bekenstein realized that the entropy of a black hole is only related to its surface area. In other words, the total information content of a black hole is stored on the surface of the event horizon containing it and not in its volume. The first signs of holography emerged.
• Bekenstein later realized that this applied not only to black holes. The information content of a volume of space is constrained by its surface. Space becomes voxelated with the information capacity of about one bit per Planck volume. If you pack more information into a region of space, a black hole must form.
• A holographic principle was spelled out by Gerard 't Hooft and later Leonard Susskind and Raphael Bousso in the context of string theory. However, the most famous implementation of holography is Juan Maldacena's AdS/CFT correspondence, seen by many as the most relevant output of string theory. In this framework, a quantum gravity theory in five dimensions is equivalent to a quantum field theory without gravity on its four-dimensional boundary.
• As black holes radiate, they evaporate. This leads to one of the most famous puzzles in physics: The black hole information paradox. Namely, what happens to the information contained in the black hole when it ceases to exist? Recently, progress has been made, leading to a very technical mix of wormholes, the holographic principle, emergent spacetime, quantum entanglement, and quantum computers.
• One cutting-edge theory claims that wormholes, non-local connections in spacetime emerging from Einstein's general relativity, are equivalent to quantum entanglement. Essentially, the theory states that spacetime is an emergent phenomenon. The idea is encoded as ER=EPR.

Information, Entropy, and Complexity

• Information is required to describe the complexity of a system—for instance, algorithmic complexity from algorithmic information theory.
• Generally speaking, the universe evolved from a state of exceptionally low entropy and will maximize it in the distant future. Complexity, in contrast, grows and then fades as entropy increases.
• Unexpectedly, entropy is a driver of self-organized structure formation. Non-equilibrium thermodynamics spells out the details of what are called dissipative structures, discovered by Ilya Prigogine. They are configurations of matter that can efficiently absorb high-quality, low-entropy energy from the environment and dissipate heat back into it, thus temporarily evading the death sentence imposed by thermal equilibrium. Examples are vortices in flowing water, Jupiter's Great Red Spot, convection cells, and reaction-diffusion systems. While the overall entropy increases in the universe, as dictated by the second law of thermodynamics, dissipative structures temporarily organize as pockets of low entropy.
• Jeremy England continued with the work on dissipative structures, formalizing dissipative adaption. Specifically, he showed how self-replication is an efficient dissipation mechanism. Organic life can now be understood as metabolic pathways, efficiently dissipating energy and increasing the universe's entropy. Life is not a cosmic coincidence but an expression of a teleological force of universal organization.
• Information reaches its full potential within the context of living organisms: it now has meaning. Agency, intentionality, volition, and purpose in biological systems are related to semantic information. This is meaningful information an organism has about its environment that allows it to maintain its existence in a state of low entropy. Indeed, any system constructed to record information about its environment and to operate with maximal energetic efficiency has to be predictive. The theory of causal entropic forces describes the emergence of intelligence in terms of entropy maximization. Life and cognition are the results of cosmic information processing.

The Metaphysics of Information

• At the core of reality, it seems we find a computational engine that needs to be fed with information. This informational ontology was first endorsed by the eminent physicists John Wheeler and Carl Friedrich von Weizsäcker. Wheeler famously exclaimed: "it from bit."
• B. Roy Frieden postulated the principle of extreme physical information. Utilizing this framework based on Fisher information, he found a unifying principle for physics. Specifically, he could derive Newton's second law, Lorentz transformations, classical electrodynamics, Einstein's field equations describing gravity, statistical physics, and the wave equations of relativistic quantum mechanics. Moreover, it can be shown how scaling laws also naturally emerge from Frieden's principle. Information geometry generalizes Fisher information and is a useful tool for studying complex systems.
• The philosophy of information notes that knowledge and information are members of the same conceptual family.
• Digital ontology is the notion that the ultimate nature of reality is digital and that the universe is a computational system. This philosophy has many proponents who study computation and information. The notion is also known as digital physics. The philosopher of information Luciano Floridi, however, proposes an informational structural realism and refutes a digital ontology.
• Holography presents a duality of theories. In other words, the equivalence of one representation related to the bulk of a volume to another expressed on the surface area enclosing it. Some scholars suspect that underlying the duality is a more fundamental theory related to information. Overall, it is conjectured that holography is a foundational principle of quantum gravity.

Midjourney / Variation of same prompt

The Cutting Edge

• A novel theory aimed at explaining fundamental physics is called constructor theory, developed by Deutsch and Chiara Marletto. It deals with counterfactual explanations, i.e., events that could have happened. Information plays a key role. Constructor theory has been utilized to explain the second law of thermodynamics in terms of quantum information. We have come full circle. Beginning with thermodynamics, specifically the relationship between entropy and information, the information-theoretic paradigm was uncovered, next to information's potential as ontological primitive, only to find quantum information underlying thermodynamics.
• Metaphysically, most scientists are in support of physicalism. This is the commonsensical but naïve assumption that at the foundations of reality, we find a physical substrate from which everything can be derived, including consciousness. Moreover, reality is understood as observer-independent. This philosophical inclination has become a cherished belief for many, even in the face of over a century of quantum weirdness, hinting at a radically different ontology and the unexplainable emergence of complexity on Earth. Moreover, modern philosophers of mind see the failure of physicalism to account for the subjective nature of consciousness as a further indication that it is ill-informed. Perhaps the metaphysics of information can help physicalists wean off the hope that reality must make sense to us at an ontological level. Specifically, information seems to fulfill the reductionist's dream of a singular basis of reality. The multifaceted and powerful context given by the concept of information makes it a likely ontological primitive, transcending space, time, and matter from which cosmic complexity is derived.
• The next question is how consciousness fits into the information-theoretic paradigm.

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¹The above is a very concise overview of Chapter 3 of a book I am currently writing about the fundamental nature of reality and consciousness. The working title is The Sapient Cosmos: What a Modern-Day Synthesis of Science and Philosophy Teaches Us About the Emergence of Information, Complexity, Consciousness, and Meaning. See this post for more information.

Previous posts include:

1. Thinking about the Mind
2. Physics and Philosophy
3. The Philosophy of Science: An Idiosyncratic Primer