This paper presents a formal experimental protocol designed to detect and measure the precise boundary between the reversible quantum world and the irreversible classical macro-world. Based on Andrei Sakharov's concept of metric vacuum elasticity, we propose that the quantum-to-classical transition is governed by a strict yield strength of the vacuum, occurring at a critical mass of 27 picograms. For a monodisperse silica (SiO₂) microsphere, this threshold corresponds to a critical diameter of 2.863 microns. Below this threshold, the vacuum undergoes purely elastic, reversible deformation, preserving time-reversal symmetry (t → −t). Above it, the vacuum experiences plastic flow, triggering energy dissipation and the objective emergence of the arrow of time. We outline the optomechanical infrastructure, a 5-point scanning grid using levitating microspheres, a comprehensive noise budget, and explicit falsifiability criteria to distinguish this model from the smooth decoherence models of Diósi and Penrose.