SunsetThese opposing skylines, one a solid silhouette the other vaporous but vividly hued, were observed from the balcony of my home in Turin, Italy on January 13, 2011. Photographer: Piero Armando

Monte Viso, at 12,602 ft (3,841 m), is the prominent peak of the jagged Cottian Alps — at right center. A bonus of the long and often gray winter months here is that the Sun sets in the vicinity of the Cottian Alps. On occasion, as on this mid-January day, once the Sun clears the horizon the sky may flare in shades of coral and purple. The shorter wavelength colors of light (blues and greens) are scattered from our view when the Sun is below the horizon, leaving the longer wavelengths (reds and oranges) to steal the show, providing that the sky is not completely free of clouds or aerosols. A crystal clear sky results in drab sunset/sunrise colors.