The Expansion Freedom Principle: A Single-Axiom Derivation of Mass, Gravity, and Cosmic Structure Without Dark Matter or Dark Energy

This paper proposes a single foundational axiom — everything seeks to expand as freely as possible — and derives from it the origin of inertial mass, Newton's laws, the equivalence principle, gravitational attraction, flat galactic rotation curves, large-scale cosmic structure, and the unnecessary nature of both dark matter and dark energy. The framework rests on two foundational recognitions. First, cosmic expansion is intrinsically acceleration: it continuously changes inertial frames, not merely displaces objects. This directly explains the origin of F=ma — a translation of F=kx from a static universe into an expanding one. Second, the natural state of any particle is free expansion analogous to light, extending Galileo's principle of inertia one step further. Binding forces (strong, electromagnetic, weak) resist free expansion, generating inertial mass via Mach's principle. Gravity emerges not as an attractive force but as the exclusion of bound matter from expanding voids — matter also tends to separate, but lags behind free space. The equivalence principle follows as a necessary consequence rather than an axiom. A critical distinction is established between dynamical orbital motion (solar system, Keplerian decline mandatory) and inertial motion (galactic outskirts, flat rotation curves). It is shown that no amount of added mass can eliminate Keplerian decline: flat rotation curves require a redefinition of the motion type itself, not additional mass. The effective gravitational flux area Aₑff (r) transitions from spherical at small scales to disk-like at galactic scales, reproducing both solid-body rotation in galactic cores and flat rotation in outskirts from geometry alone. The cosmic web is interpreted as the simultaneous maximization of expansion freedom for both voids and matter — its filamentary structure is direct observational evidence that matter itself tends to separate. Dark energy is unnecessary because free expansion costs zero energy; it is the ground state. This is v1. 0 of The expansion freedom principle and v6. 0 of the Gravitational Flux Transport Networks preprint series.