Propagation-Based Degeneracies in Cosmological Redshift Measurements

We examine a class of propagation-based degeneracies in cosmological redshift measurements, showing that several key observational signatures commonly interpreted as evidence for metric expansion can arise instead from distance-dependent attenuation during signal propagation. By modeling light propagation through a structurally constrained medium characterized by finite impedance, we demonstrate that redshift, surface brightness evolution, and spectral coherence can remain observationally consistent with data while admitting a non-expanding spacetime interpretation. Under a generalized balance condition analogous to the Heaviside criterion in transmission theory, attenuation occurs without dispersion, preserving angular resolution and blackbody spectra. We argue that cosmological expansion emerges as an interpretative closure imposed at the observational level, rather than as a uniquely required dynamical inference. This work does not propose a complete alternative cosmology, but instead identifies a previously underexplored degeneracy in redshift-based inference pipelines, highlighting the need to distinguish between kinematic expansion and structurally induced propagation effects. We outline concrete observational tests—including time-dilation behavior, Tolman surface brightness scaling, and spectral coherence—that can discriminate between propagation-based and expansion-based explanations.