Alpenglow is a term that photographers (and artists) use to describe a type of light that was often seen at the end of the day in the Alps, turning the snow-covered peaks a bright crimson red. A recent question posted over at Photo.net prompted me to reply, and I thought I would go ahead and repost an edited version of my reply here as well, including the photos.
Alpenglow; it wouldn’t surprise me a bit if it was Galen Rowell’s use of the term that popularized the word among photographers, namely to describe the reddish glow that would appear on the snow-crested Alps. Taken in a more common context, I describe alpenglow to people as the red and pink colored light that appears at either sunrise or sunset.
The reddish color lightwaves are the longest in the visible spectrum of electromagnetic energy. Of all the visible lightwaves, they also move the slowest. Light that has to travel through more atmosphere has most of the blue absorbed, so the slower red waves of color are actually the only ones that make it through to our eyeballs. As the sun sets (or rises; reverse the process) you can see a gradation of color rise in the eastern sky, pinkish red onto of blueish purple. As I actually once explained to Galen – this transition of color is really our horizontal view of the Terminator Line, which is the line between day and night that the space shuttle astronauts would see when looking down (vertical) on the planet. (It was a big deal to be able to know that I taught him something, however small, albeit thanks to my interest in astronomy.) The pinkish red light is actually sunset light that continues to rise in the sky as the sun dips below the horizon. The blue purple light is actually the shadow of the earth also rising into the sky. Mountains get the most red light since they are higher, but that same ligh can also light the underside of clouds after the sun has already dipped below the horizon.
Yes, you can see alpenglow at lower elevations including sea level. The primary difference is the amount of time that red light will be distinctly visible, before transitioning to a warm golden, or yellow light. When I did my book on San Francisco, I purposely shot the TransAmerica Pyramid as if it was a mountain peak. The red light did show on the building, but it didn’t last for more that 2 minutes. In the Eastern Sierra, you can watch the transition form pink to red to gold take over ten minutes or more. Again, the differnce in time that the effect lasts is totally related to the amount of atmosphere the light needs to travel through.
See more examples of Alpenglow in my Mountains, Yosemite, or Eastern Sierra Photo Galleries.
