The double‑slit experiment and its variants — delayed choice and quantum erasure — constitute the most central “paradox” in quantum mechanics: the act of observation itself changes the state of the observed system. Mainstream interpretations (Copenhagen, decoherence, many‑worlds) successfully describe the experimental phenomena, but none address at the ontological level the more fundamental question: why does the observer change reality? Based on the complete framework of the PFUSRC system, this paper identifies the deep predicament of mainstream physics: it lacks a unified ontological consensus at the foundational level, and can only use the “reported results” from the three‑dimensional projection layer to retrospectively explain the complete topological process of the four‑dimensional flow variables. This paper introduces the “Worm and Apple” cognitive model, providing a complete localization of the double‑slit experiment: 1. Interference fringes are static cross‑sections of multi‑path phase superposition from the Issuance Layer at the Projection Layer; their existence depends on the Valuation Layer having introduced no disruptive anchors; 2. Recording path information is equivalent to introducing a discrete topological anchor (“scar”) at the Valuation Layer, which alters the boundary conditions of TSRD collapse, changing the Projection Layer from interference fringes to a bimodal distribution; 3. The delayed choice experiment does not involve “changing the past,” but is a projective misreading by the Projection‑Layer observer of the temporal asymmetry of TSRD; 4. The quantum erasure experiment does not “erase” information, but switches the anchor from a “path marker” to a “phase‑relation marker,” allowing interference fringes to reappear at the Projection Layer; 5. The observer’s “bewilderment” stems from a self‑referential dilemma — the observer is itself part of the apple (PFUSRC‑162: the “True Self” is a self‑referential closed loop within the carrier), yet attempts to stand outside the apple to obtain "objective" information, using static results from the three‑dimensional Projection Layer to explain a four‑dimensional process. This paper further argues that mainstream physics lacks comprehensive cognition of both three‑dimensional dynamic variables and four‑dimensional flow variables, and can only use rigid three‑dimensional reported results to explain the complete process. The "strangeness" of the double‑slit experiment is not the essence of the quantum world, but a consequence of the observer forgetting that it too is part of the apple. This paper proposes three testable corollaries, transforming the observer problem from philosophical contemplation into experimentally decidable physical questions.
Zhenmin Wang (2026) studied this question.