Spin-Axis Organization and Orbital Spacing in Planetary Systems: A Phenomenological Radial-Wave Framework for Obliquity Correlation

Planetary obliquities—the angles between planetary spin axes and their orbital-plane normals—displaysubstantial variation across the Solar System. Classical explanations attribute axial tilts primarily toprimordial angular momentum, stochastic giant impacts, tidal evolution, and long-term gravitational perturbations. While these mechanisms account for many individual cases, the overall distribution of planetaryobliquities and orbital distances raises the possibility that additional large-scale dynamical organizationmay be present within rotating gravitational systems.In this work, a phenomenological framework referred to as Radial Waves is introduced to interpret correlations between planetary spin-axis orientation and orbital spacing. The framework proposes that rotationalsymmetry in approximately spherical gravitational systems can give rise to structured sinusoidal radialmodulation patterns. These patterns are not introduced as new physical fields or energy carriers; rather,they represent organized dynamical structures arising from rotational and gravitational coupling.Within this interpretation, orbital radii and planetary obliquities can be viewed as responses to positionwithin a radial modulation structure. Regions corresponding to radial troughs are associated with minimalobliquity states, while crest regions correspond to maximal axial tilt. Because radial wavelength increaseswith distance from the central body, the framework also suggests a tendency toward quasi-uniform orbitalspacing at larger separations.The proposed formulation does not modify classical gravitational theory, conservation laws, tidal evolutionmodels, or perturbative celestial mechanics. Instead, it provides a phenomenological geometric interpretation of planetary spin-axis organization within rotating gravitational systems. Possible implications forplanetary-system architecture are briefly discussed.