Planetary Freedom and Constructal Drivers of Earth's Architectures

Constructal Law states that finite-size flow systems evolve configurations that provide progressively easier access to the currents flowing through them. In the Freedom-Planet Signal Constraint Hypothesis (FP-SCH), this principle operates within variance landscapes established by planetary formation and dynamical history. These landscapes-environmental freedom in the Constructal sense, the external variability a flow system must have to morph toward better access-are summarized with a dimensionless, Earth-normalized planetary-freedom index, F_h. For modern Earth, F_h = 1.0 reflects the Moon-forming giant impact, sustained tidal forcing, mobile-lid tectonics, volcanic-outgassing variability, and orbital-axial climate cycles. Where such variance reaches the biosphere as recurrent ecologically significant excursions, characterized by excursion return time τ_e, long-term evolutionary success is governed by geometric-mean rather than arithmetic-mean fitness. The framework derives the crossover at which recurrent unfavorable states favor a class of variance-buffering flow-access architectures that preserve usable currents. On Earth, one major realization of this class was pursuit-escape architecture, a flow-access solution combining active mobile flow tracking, bilateral symmetry, cephalization, and compressed perception-action loops. FP-SCH hypothesizes that this realization favored concurrent predictive error minimization, coherent information sharing, and persistent goal maintenance (Triad concurrency) as a falsifiable downstream hypothesis. The framework yields ordinal predictions: low-F_h or strongly buffered worlds should favor slower, distributed, sessile, mutualistic, or dormant strategies, whereas higher-F_h or less-buffered worlds whose variance reaches the biosphere should favor active, mobile flow tracking. These predictions offer priors for biosignature interpretation. Earth is one observed Constructal realization under a relatively high-freedom planetary regime, not a universal template.