Description This preprint reframes Crookes’ radiometer as a compact metrology experiment for Quantum Measurement Units (QMU) within the Aether Physics Model (APM). The radiometer is a cross-domain transducer: incident optical delivery produces a steady mechanical torque, but only through an intermediate rarefied-gas boundary-layer mechanism. Standard presentations often mix radiometric, thermodynamic, kinetic-theory, and rigid-body units, which obscures dimensional structure. QMU is used here to make that structure explicit and to reduce the analysis to a small set of primitive anchors plus dimensionless channel functions. The paper emphasizes the modern mechanism (thermal transpiration / thermal creep and edge-mediated rarefied-gas stresses), rather than radiation pressure. Two observed signatures are treated as immediate consequences of the same rectification chain: (i) the black (hotter) face trails; and (ii) the torque peaks at intermediate pressure and vanishes in a hard vacuum. The derivation isolates three stages: (1) optical delivery (treated as a conserved transport content, with interchangeable ledger expressions), (2) surface conversion into a thermal asymmetry, and (3) gas-mediated rectification into tangential stress and net torque. A practical reporting template is included so that laboratory datasets can be published in a ledger-closed form. The template separates what is controlled (illumination, geometry, environment) from what is observed (rotation versus time) and what is reduced (torque, mechanical power, and dimensionless closure ratios). A minimum-instrumentation protocol is also provided for factory-sealed radiometers with unknown internal gas and pressure. This protocol uses a dark spin-down “drag index” as an empirical pressure proxy and produces a kinematic, ledger-first scalar that can be compared across lighting conditions without requiring absolute pressure measurement or a separate inertia measurement. For reproducibility, an appendix provides a short reference script that converts time–RPM traces into the reduced quantities and QMU-normalized scalars used in the template. SI units are confined to an appendix as a bridge for laboratories that measure in conventional instrumentation but wish to report ledger-closed, dimensionless QMU scalars. What is included The manuscript PDF (radiometer model, protocol, and reporting template). Optional: a small reference script for data reduction (time/RPM to reduced scalars).
David Thomson (2026) studied this question.