Light as a Density-Bound Carrier

The speed of light c is treated in modern physics as a universal invariant — the anchor
of spacetime, the metronome of causality, and the foundation of the relativistic framework.
The Cohesion UFT (Gilbert 2025–2026) predicts that this invariance is local rather than
universal: c is the propagation rate of light within Earth’s density layer, not a property of
empty space as such. In a substrate-driven universe, light is a carrier whose propagation rate
is governed by the resistance of the substrate it traverses. Higher substrate density produces
higher resistance and slower propagation; lower density produces lower resistance and faster
propagation.
This paper develops the formal operator set for density-bound light propagation, derives two new cosmological consequences not yet stated in the Cohesion UFT series, and
presents the resulting experimental predictions. The two new contributions are: (1) a
density-dependent redshift decomposition z = zvel + zdens that separates the velocity-driven
and density-driven components of observed redshift; and (2) a distance correction factor
Λc = cE/vvoid that relates Earth-frame distance measurements to the true distances in a
variable-propagation universe. Both are falsifiable with existing or near-future observational
programmes.
This paper is an extension of the Scaling GR framework [3] and the Cosmological Dynamic [5]. The GPS argument establishing the locality of c is developed in [3] and is not
repeated here.
Scope and Prior Work. The variable-propagation hypothesis — that the effective speed
of light varies with substrate density — was introduced in the Scaling GR paper [3], which
established the GPS argument: all precision measurements of c have been made within
Earth’s gravitational and density envelope, and GPS validates c only within that envelope.
This paper accepts that argument as established and extends it to derive specific cosmological
predictions. The claims here are predictions of an unvalidated hypothesis. They are stated
as predictions, not established results.