Gravitational Flux from Cosmic Expansion Drives Galactic Dynamics

Rather than postulating dark matter or modified gravity, we attribute the acceleration beyond the local field, seen in galaxy rotation curves and velocity dispersions, to gravitational flux from cosmic expansion. This effect, of order 10⁻¹⁰ ms⁻², follows without free parameters from applying Gauss's flux theorem to all receding galaxies, reproducing the generalized Tully-Fisher and Faber-Jackson relations. Although isotropic on large scales, the enormous efflux of space cannot be ruled out by the shell theorem—formulated for stationary rather than dispersing matter—nor dismissed with distance, since the quadratic rise in galaxy number outweighs the inverse falloff of their potentials. From this perspective, space is not mere abstract geometry but a dynamic relativistic substance: a spin-2 boson, paired-photon vacuum with undulating energy density consistent with general covariance and tests of relativity. Accordingly, bodies move neither inward by inexplicable attraction nor outward by unexplained expansion, but by coupling, via mass, to space in flux. The Type Ia supernova data are consistent with space expanding through the influx of quanta released from matter in astrophysical processes, rather than implying a dark-energy-driven metric acceleration. Structures emerge on ever larger scales because the virial radii of efflux–influx balance lengthen as spatial density thins from the early universe to the present sparseness, giving rise to the observed cosmic gravitational redshift.