Gravity as falling space: the exterior equivalence principle, a speed limit for space, and a hypothesis under which collapse forms no horizon

The equivalence principle is normally applied from inside a rocket: no localexperiment within it can distinguish acceleration from gravity. Einstein’s ownderivations, however, used an outside view, in which the rocket moves throughspace, a premise never stated as part of the principle. Extending the correspon-dence to that outside view, the exterior equivalence principle, reveals a mismatch:an accelerating floor moves to meet downward light, but a floor held static ingravity does not. We propose that gravity is falling space, Acceleration FieldSpace (AFS), a physical flow added to the metric of general relativity (GR) thatmoves past static bodies at the local escape velocity. The Lorentz factor of astatic body in this inflow is the Schwarzschild coefficient, giving gravitationaltime dilation, radial length contraction and mass–energy. For one body AFS isthe Gullstrand–Painlev´e form of the Schwarzschild metric, so it reproduces thefour classical tests exactly. The departure is one hypothesis additional to GR:that the flow is real, so that moving through space and space moving past areone relative motion. The speed limit c then applies to the flow relative to anybounded source, so no sphere is trapped, no horizon forms, and a compact objectmust have a surface outside 2GM/c^2. The exterior and the prompt ringdownare unchanged, but the surface returns echoes, re-radiates the energy of accretedmatter and has a non-zero tidal deformability; current data allow only a surfaceextremely close to 2GM/c^2. A sketched velocity-dependent source law keeps theflow below c for any density; its dynamical completion is left open