Quantum Derivation of Rayleigh Scattering: Why the Sky is Blue and the Sunset is Red
Gennadirvich Andrey Ryabokon
Abstract
This explanation is based on the phenomenological decoherence principle presented in https://doi.org/10.5281/zenodo.18640591. According to this principle, the probability of maintaining coherence (e.g., the absence of scattering) is given by an exponential of the integral of the squared effective environmental field: C = C_0 exp(-alpha integral F^2 dx). We show how this principle, combined with quantum mechanics, naturally yields the famous Rayleigh law (λ^(-4)) that explains the color of the sky. We present an alternative derivation of the Rayleigh scattering cross section starting from a microscopic model of light scattering by independent molecules. The exponential attenuation law (Bouguer–Lambert–Beer law) is linked to the sum of squared scattering amplitudes of individual particles, which follows directly from the phenomenological decoherence principle. Using a three-dimensional harmonic oscillator as a model of a molecule, we compute the elastic photon scattering amplitude to second order in perturbation theory within the dipole approximation. The resulting cross section exhibits the characteristic ω^4 dependence, directly accounting for the blue color of the sky and the redness of the Sun at sunset. No empirical data are used; all results follow from first principles of quantum mechanics and the proposed decoherence principle. This publication is part of a broader conceptual program aimed at providing a unified phenomenological description of decoherence and attenuation processes. The framework is fully consistent with standard quantum mechanics and should be viewed as an organizing perspective rather than a proposal of new dynamics.