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Timing Inaccessibility and the Projection Bound: Resolving Maxwell's Demon for Continuous Biological Substrates

What's this about?

The brain is 100,000× more energy-efficient than silicon because it defers thermodynamic costs — computing reversibly until the moment it must commit to a discrete output.

Timing Inaccessibility and the Projection Bound: Resolving Maxwell's Demon for Continuous Biological Substrates

Version 2.0 now available

v2.0 (December 2025) extends the published paper with three new arguments: (1) Framework dependence of timing — what counts as "simultaneous" vs "sequential" depends on the measurement framework, making temporal structure framework-relative. (2) The "when" is created, not revealed — temporal order does not pre-exist measurement but emerges at projection. (3) AI substrate constraints — digital architectures cannot access the sub-Landauer integration regime regardless of scale, though behavioral approximation may remain possible.

The paper now explicitly traces the Maxwell's demon lineage (Maxwell → Szilard → Landauer → Bennett → this paper), showing how biological systems extend the resolution to continuous substrates via path degeneracy. The key insight: the Landauer-Bennett resolution assumed discrete memory states; biology operates with continuous dynamics where "memory" is structural correlation, not written bits.

Below the Landauer limit (3×1021\sim 3 \times 10^{-21} J), you can't irreversibly record when things happen without paying kBTln2\ge k_BT\ln 2 per stabilized order bit. This creates massive "path degeneracy" — exponentially many micro-trajectories (105010^{50} to 1010010^{100} in neural systems) that all look the same from the outside. Biology exploits this via a two-stage model: Stage 1 (reversible correlation) is thermodynamically cheap; Stage 2 (stabilization/projection) is where the cost appears.

Key findings

  • Derived the Projection Bound: energy cost scales with dimensional collapse, not bit operations

  • Two-stage model: reversible coupling (free) vs stabilization/registration (Landauer cost)

  • Path degeneracies of 10^42 to 10^94 (proteins) and 10^50 to 10^100 (neural)

  • Digital efficiency depends on projection boundary placement, not "digital vs analog"

  • Explains 10^5 to 10^8× efficiency gap between brains and silicon

Citation

Todd, I. (2025). Timing Inaccessibility and the Projection Bound: Resolving Maxwell's Demon for Continuous Biological Substrates. BioSystems (November 2025).
https://doi.org/10.1016/j.biosystems.2025.105632

Workflow: v1.0: Claude 4.5 Sonnet (Anthropic) for drafting; GPT-5 (OpenAI) and Grok (xAI) for review. v2.0: Claude 4.5 Opus (Anthropic) for extended framework-dependence, demon lineage, and AI implications; GPT-5.2 (OpenAI) for review. Author reviewed all content and takes full responsibility.