Gravity as Vacuum Refraction

Einstein's General Relativity treats gravity as the curvature of spacetime: mass curves the fabric, and light follows curved geodesics. This is mathematically elegant but ontologically mysterious — what is spacetime, and how does mass curve it?

This paper shows that "spacetime curvature" is a mathematical fiction for the wave sector. The real mechanism is vacuum refraction: mass polarises the vacuum, creating gradients in the local refractive index. Light bends toward regions of slower c — just as light bends into glass. For light propagation, gravity is not geometry — it is optics.

Crucially, this paper provides the physical mechanism for why mass polarises the vacuum — a gap left unaddressed by previous polarisable vacuum theories. The vacuum is not empty: it is permeated by a continuous sub-threshold ambient electromagnetic background — the natural sea of transient field displacements constituting the vacuum's baseline polarisability. Matter particles are concentrated electromagnetic field structures (solitons) that act as macroscopic boundary conditions on this ambient background. Through mutual polarisation equilibrium, the local ambient field density increases near matter, raising the effective refractive index and slowing local light speed. The gradient forms as this redistribution falls off with distance.

The Schwarzschild metric — the heart of GR — is derived without invoking curvature, treating space as flat with variable light speed. This reproduces GR's predictions for light — gravitational lensing, Shapiro delay, photon orbits — while providing a clear physical mechanism.

Black holes are not singularities in spacetime; they are regions where the refractive index becomes so high that light cannot escape (total internal reflection). Gravitational waves are not "ripples in the fabric"; they are longitudinal density waves in vacuum polarisation affecting light propagation.

This paper addresses the wave sector — how light bends in vacuum gradients. How matter responds (falling objects, orbits, equivalence principle) requires introducing matter as finite soliton structures, developed in OFT 4.