Empirical Determination of Source Distance via Thermal Radiation and the Inverse Square Law

This paper presents a method for determining the distance to a radiative heat source by combining the Stefan-Boltzmann radiation law with the inverse square law of irradiance propagation. Controlled bench-scale experiments using a standard incandescent lamp as a calibrated thermal emitter demonstrate that source distance can be reverse-calculated from three measurable quantities: emitter surface temperature, emitter radius, and observed irradiance at the measurement point. Agreement between physically measured and calculated distances was within 1% across all trials. The same formulation is then applied to published solar parameters, yielding an Earth-Sun distance of approximately 149.98 × 10⁶ km, consistent with the accepted value of 1 AU to within 0.3%. This work provides an empirical proof-of-concept that radiative intensity data alone can serve as a viable non-visual distance metric, with potential utility in astrophysical modeling and remote sensing.