WYSIWYG Physics and the End of Determinism
Perhaps the most fundamental conceptual question facing physics is the nature of time. Relativity describes time as a dimension of spacetime, and like the three dimensions of space, the dimension of time is fixed and without a preferred direction. The future, as well as the past, is set in stone. At the same time, however, physics acknowledges the increase in entropy as a universally valid empirical law, and it recognizes quantum randomness.
The tension among the reversibility and determinism of physics, the empirically validated Second Law of thermodynamics, and quantum randomness underlies many of physics’ conceptual difficulties. Is the flow of time toward the future real or just an illusion? Does the future already exist, only to be revealed to us? Do we have free will and a moral responsibility for our choices? Does randomness arise from unknowable external interactions? Given that our universe, by definition, has no surroundings or external interactions, does the determinism of physics imply that all possible outcomes are manifested in separate branches of an exponentially branching universe? These questions are unresolved and continue to be debated.
Determinism and reversibility are logical consequences of classical mechanics. Classical mechanics considers the physical state, which underlies our observations, as completely defined by perfect measurement. It defines perfect measurement in the limit of zero thermal noise, even if we cannot reach that limit in practice. The laws of mechanics, when applied to the classical state, precisely specify all states, past and future. The classical mechanical state is also non-contextual. Positions and motions are defined with respect to an inertial reference frame. We can easily convert from one reference frame to any other and preserve all information. The state’s information is independent of the particular reference frame from which it is defined. This expresses the non-contextuality of the classical mechanical state.
Quantum mechanics upended the classical concept of state. It revealed that the inability to precisely measure positions and motions is a fundamental limitation — it is not just a practical or instrumental limitation. Quantum mechanics defines a system’s observable state by a wavefunction, which can only specify positions and motions in terms of probabilities. The wavefunction itself, however, is reversible and deterministic. It precisely specifies the probabilities of a quantum system’s measurement results and the changes in probabilities over time. The wavefunction preserves the determinism of reversibility of the classical mechanical description of state, even though their descriptions are radically different.
Quantum mechanics preserves another key feature of classical mechanics, non-contextuality. A quantum system’s measurable properties, even including whether it is particle-like or a wave-like, depend on how it is measured. Quantum measurements are fundamentally contextual. However, quantum mechanics employs quantum tomography to define the wavefunction non-contextually, using measurable information from all possible contexts. This defines the wavefunction as objective and independent of any particular measurement framework, context, or observer.
The quantum wavefunction allows describing quantum states as superpositions of measurable states. A measurable state, with definite measurable properties, is described as an eigenfunction. A superposed wavefunction is the sum of eigenfunctions, describing the simultaneous superposition of measurable eigenstates. For example, when a radioactive particle is first created, it exists as a definite measurable eigenstate. After a period of time, however, its measurable properties are no longer definite. Measurement might reveal the original particle, or it might reveal its decay products. The quantum wavefunction describes the particle as a superposition of all possible measurement outcomes.
The wavefunction describes an isolated quantum system as deterministic and reversible. The nature of the underlying physical state, as it exists isolated, unperturbed, and unobserved, however, is strictly a matter of interpretation. The mainstream Copenhagen Interpretation asserts that the wavefunction is complete. This implies that the quantum system’s underlying physical state is also reversible and deterministic as long as it remains isolated from external perturbations.
Erwin Schrodinger tried to illustrate the absurdity of assuming the completeness of the wavefunction. He imagined putting a radioactive particle, a cat, and a detector which releases cyanide gas if the particle decays, into an isolated box. At preparation, the wavefunction describes a live cat. Sometime later, the wavefunction describes the probabilities of observing a dead cat or live cat. Determinism and completeness of the superposed wavefunction implies that the initial particle and cat evolve to an indefinite superposed state of decayed-undecayed particle and live-dead cat (see figure). Only when the veil of isolation is broken at observation, does the system statistically actualize into a dead cat or live cat.
To avoid the implications of the Copenhagen Interpretation, Hugh Everett proposed his Many Worlds Interpretation. He traded the absurdity of superposed cats and observation-induced actualization for the absurdity of an exponentially branching universe, in which everything that can happen does happen in splitting branches. Even we, as observers, are split, with each of our split selves perceiving the random actualization of a single possibility. From the objective perspective of the universe as a whole, however, there are no physically superposed states and no random actualizations.
Both the Copenhagen Interpretation and Many Worlds Interpretation assume the completeness of the wavefunction, each with its own metaphysical implications. Whether the wavefunction completely specifies the underlying physical state, however, is another unresolved and debated question.
There is a strong sentiment among many physicists to accept quantum mechanics as the extremely useful tool that it is, and not to question its metaphysical or philosophical implications. Richard Feynman is credited with saying: “The philosophy of science is as useful to scientists as ornithology is to birds.” Efforts to understand the meaning of quantum mechanics are countered with the edict: “Shut up and calculate!”
Seeking an objective interpretation of physical reality is more than an idle intellectual exercise, however. The universe is not a static block in spacetime, unchanging for eternity. Recognizing the objective reality of irreversible processes and explaining their behavior in terms of fundamental physical principles is essential if we want to understand how nature works. Advancing physics beyond its current focus on states, and understanding the irreversible and spontaneous emergence of complexity, require nothing less than a major shift in our interpretation of physical reality.
By abandoning physics’ deeply ingrained assumption of non-contextuality, the WYSIWYG Conceptual Model (WCM) recognizes irreversibility and randomness as fundamental properties of the physical state [1]. The WCM has as its principal premise “What You can See is What You Get.” WCM makes no assumptions for anything that cannot be measured or observed. It makes no assumptions for unmeasurable and unknowable properties of state. It makes no assumptions for hidden quantum variables. It is based on empirically sound assumptions, empirical facts, and logic.
The WCM’s premises are empirically well documented. Its first premise assumes only measurable properties matter. Its second premise includes temperature as a measurable and well-defined physical property. Its third premise is that absolute zero temperature, and measurement in the total absence of thermal noise, are unattainable idealizations. The WCM defines perfect measurement as a reversible and information-preserving transformation from a system’s initial state to a reference state in equilibrium with the system’s actual surroundings at a positive temperature. By its first postulate, WCM defines the physical state by perfect measurement. The WCM state is independent of any particular reference state in the system’s surroundings, so it is objective. It is also explicitly contextual, in that the state depends on the system’s actual surroundings, and there is no information-preserving transformation for changes in the surroundings’ temperature.
The WCM starts with the non-contextual state of a classical or quantum system. It ignores unmeasurable properties, and adds contextual properties of state, as measured from the system’s surroundings. Ambient temperature is defined by the temperature of the system’s surroundings with which a system interacts or potentially interacts. The WCM then partitions the system’s total energy into contextually defined parts. Ground state energy is the positive energy of the system’s reference state in equilibrium with the system’s surroundings. Exergy is the potential work by the system on the reference state, and ambient heat is the remaining energy. Ambient heat is heat at the ambient temperature, and it has zero potential for work on the ambient reference state. The WCM defines entropy as the ratio of ambient heat to ambient temperature. The WCM entropy is a generalization of the statistical mechanical entropy and a generalization of the von Neumann entropy for quantum systems [1]. The WCM’s contextual properties supplement physics’ measurable and non-contextual properties, and together, they completely describe the WCM state, as it exists with respect to surroundings at a positive ambient temperature.
The WCM resolves many of the conceptual questions facing physics. By establishing entropy as a physical property of state, the WCM establishes the Second Law of thermodynamics as a fundamental law of physics, not just empirical law, and it establishes the thermodynamic arrow of time as fundamental. A radioactive particle exists as an unstable but definite state, until it spontaneously and irreversibly decays to another definite state. At no point does the particle, or an entangled cat, exist as a superposed state or split into separate worlds. There is only the irreversible and random transition of a metastable state to a state of higher stability. As described in [1,2], the WCM resolves the problem of quantum nonlocality. It explains the correlations of simultaneous measurements without superdeterminism or “spooky” superluminal action at a distance. And as described in [1,3], it explains the evolution of open dissipative systems toward higher functional complexity and stability, which is manifested from subatomic scales to cosmic scales. The WCM is based on simple assumptions and its implications are straightforward. Its simplicity, however, belies its transformational expansion of physics from its traditional focus on static states to include irreversibility, randomness, and the evolution of complexity.
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1. https://www.preprints.org/manuscript/202007.0469/v5
2. Action at a Distance — No Spookiness, No Superdeterminism
3. https://medium.com/discourse/the-arrow-of-functional-complexity-b789a39f0892
