The 3 Body Mirror: Exact Return, Fibonacci Conjugacy, and the Nonlinear Boundary

A moving observer can recover the relative configuration of a three-body system from within it. Newtonian reflection and time reversal supply an exact inverse; a selected hyperbolic sector of the equal-mass Euler orbit realizes the Fibonacci transport Q2. The nonlinear system preserves the mirror relation, while its fourth-order normal form determines where linear conjugacy stops.We give an explicit realization of a mirror–return structure in the planar Newtonian three-body problem. Relative observations reconstruct the barycentric configuration without knowledge of the observer’s trajectory.