The Standard Model unites electromagnetism and the two nuclear forces as spin-1 quantum fields propagating on a fixed spacetime background. Gravitation resists this treatment. General Relativity describes it not as a field on spacetime but as the curvature of spacetime itself, and this difference is structural rather than cosmetic. This paper identifies the specific features responsible: Weinberg's demonstration that Lorentz invariance forces a massless spin-2 field to couple universally to all stress-energy, the Weinberg-Witten theorem constraining composite gravitons, the appearance of unphysical singularities, and the two-loop ultraviolet divergence established by Goroff and Sagnotti, which shows that pure Einstein gravity is not renormalizable in the sense that electrodynamics is. Together these keep gravitation formally outside the electromagnetic spectrum even though it is measured and taught as a force. The paper then introduces the hypothesis developed across the remainder of this series, the Theory of NeoGravity, which proposes that gravitational attraction is a mechanical reaction load, the Radiative Undertow, returned upon matter by a space-filling Ether Plenum. The paper names, without qualification, the principal mainstream results weighing against this hypothesis, including the outward direction of measured radiation pressure and the MICROSCOPE constraint on composition-dependent free fall at one part in ten to the fifteenth, and shows that the latter constrains the mechanism so severely that any coupling proportional to thermal emission is excluded by roughly fourteen orders of magnitude. The paper closes with a roadmap of the seventeen papers that follow.
John Guagliardo (2026) studied this question.