Look Away From the Sunset
If you resist the urge to follow the sun at sunset and instead look to the east, you may be rewarded. The subdued yet spectacular glow on the horizon in the eastern sky is the the effect of the earth’s terminator overtaking us. As twilight descends on us, we see the cross-section of the terminator with the light of sunset layered above the purple of the penumbral shadow that is twilight. Sunset over the snow covered Appalachian Mountains northwest of Roanoke, Virginia.
The Aerial Horizon 