(green) light from the direct path to the observer. The remaining unscattered light is therefore mostly of longer wavelengths and appears more red. Some of the scattering can also be from sulfate particles. For years after large Plinian eruptions, the blue cast of the sky is notably brightened by the persistent sulfate load of the stratospheric gases. Some works of the artist J. M. W. Turner may owe their vivid red colours to the eruption of Mount Tambora in his lifetime. In locations with little light pollution, the moonlit night sky is also blue, because moonlight is reflected sunlight, with a slightly lower color temperature due to the brownish color of the moon. The moonlit sky is not perceived as blue, however, because at low light levels human vision comes mainly from rod cells that do not produce any color perception (Purkinje effect). Of sound in amorphous solids Rayleigh scattering is also an important mechanism of wave scattering in amorphous solids such as glass, and is responsible for acoustic wave damping and phonon damping in glasses and granular matter at low or not too high temperatures. This is because in glasses at higher temperatures the Rayleigh-type scattering regime is obscured by the anharmonic damping (typically with a ~λ−2 dependence on wavelength), which becomes increasingly more important as the temperature rises. Rayleigh scattering in gases, strictly speaking, is induced by microscopic dipole fluctuations in the electromagnetic field of visible light. In amorphous solids, theories have been proposed which argue that Rayleigh-type scattering arises due to wave scattering from macroscopic spatial fluctuations in the elastic shear modulus. More recently, however, a Rayleigh-type quartic dependence of the damping coefficient on the sound wavelength, ~λ−4, has been derived from first principles based on wave scattering from microscopic motions of the atoms or particles (i.e. the microscopic building blocks of the solid), known as "nonaffine" motions, which are of crucial importance for the elasticity of amorphous solids. The effect has been derived by Baggioli & Zaccone and numerically confirmed, independently, by Szamel & Flenner. The numerical analysis has also revealed that the ~λ−4 contribution from macroscopic fluctuations of shear modulus is quantitatively negligible compared to the ~λ−4 scattering contribution from nonaffine motions. Furthermore, the microscopic theory is able to recover the crossover from diffusive type ~λ−2 scattering which dominates at lower wavevectors to the Rayleigh-type ~λ−4 scattering at higher wavevectors. In amorphous solids - glasses