Projection Geometry: A Minimal Geometric Framework for Non-Invertibility in Physical Measurement

This work introduces projection geometry as a minimal, purely geometric framework for understanding the fundamental limits of physical measurement. Modeling observation as a measurable projection from a system state space to an observable space, the paper shows that non-invertibility of this projection generically obstructs the existence of invertible observable dynamics—even when the underlying system evolves deterministically and invertibly. The results are derived using only basic assumptions about measurable spaces, projection maps, and physical interfaces, without invoking probability theory, quantum postulates, or statistical ensembles at the level of the obstruction. A central theorem demonstrates that, for generic (non fiber-preserving) dynamics, no consistent invertible evolution can be defined on observable states. The framework is supported by a set of objective facts drawn from geometry, physics, perception, and information theory, highlighting the roles of dimensional reduction, finite resolution, and selective coupling. These structural constraints imply that physical measurement is universally non-invertible: multiple distinct system states are operationally indistinguishable through any physically realizable interface. This perspective provides a unified geometric account of information loss, irreversibility, and observer dependence, and suggests that features often associated with quantum theory—such as apparent state collapse and operational equivalence—may arise as consequences of projection-induced non-invertibility.