Effective Mass Emergence and Drag-Enforced Speed Limits : Photon Inertia, Vacuum Drag, and Frame Dragging as a Unified Speed-Limit Mechanism

Special relativity postulates the speed of light c as a universal constant without providing a physical mechanism for its enforcement. The standard geometric interpretation treats c as a property of spacetime structure rather than the result of a physical force opposing further acceleration. This paper proposes a complementary mechanical framework derived from a single starting point — the mass-energy equivalence relation E=mc² — without recourse to quantum field theory, zero-point field formalism, or spacetime geometry. The central argument is threefold. First, mass is not an intrinsic fixed property of matter but an energy-speed relationship: E=mc² implies that any object carrying sufficient energy at sufficient speed manifests mass-analogue behaviour, including resistance to further acceleration. Second, nominally massless particles such as photons carry energy and momentum and therefore possess effective relativistic mass proportional to their frequency (m_rel = hf/c²); at the extreme energies corresponding to the speed limit, this effective mass generates inertial drag equivalent in effect to the resistance experienced by massive particles at high velocity. Third, the physical medium in which this drag operates is identified as the quantum vacuum fabric, with frame dragging (the Lense-Thirring effect from rotating massive bodies) as the observable large-scale signature of the same vacuum-mass coupling that enforces the speed limit locally. The framework shares its conclusion — inertia as an emergent property of vacuum interaction — with the Quantum Vacuum Inertia Hypothesis (Haisch, Rueda and Puthoff, 1994) and subsequent work by Nickisch and Mollere (2002), but arrives via an independent and structurally simpler route. The novel contributions of this paper relative to prior work are: the E=mc² derivation pathway (prior work used zero-point field formalism), the explicit extension to photons as experiencing effective drag through their relativistic mass, and the unification of local vacuum drag with large-scale frame dragging as a single physical mechanism.