Why Green Flash Sunset Sightings Are Surging Across Coastal Skies This Winter
By James H. Sterling
Every green flash begins with the atmosphere functioning as an immense, curved prism. Under normal daytime conditions, sunlight travels through a relatively thin vertical slice of air, keeping all colors blended into direct white or yellowish light. When the sun touches the horizon, its path through the atmosphere stretches up to 40 times longer than at midday.
This extended path forces atmospheric dispersion into action. Air bends short wavelengths of light (violet, blue, and green) more sharply than long wavelengths (orange and red). As the solar disk drops, the red and orange images set first, vanishing beneath the curvature of the Earth. The green, blue, and violet disks remain refracted slightly higher, hovering briefly above the horizon line.
Violet and blue light should theoretically be the last colors visible. They rarely reach human eyes because of light scattering. Fine molecules in the atmosphere, the same mechanism described by Rayleigh scattering, scatter violet and blue wavelengths across the sky long before they reach an observer at sea level. Green light survives the journey with sufficient intensity, delivering that isolated, incandescent flash.
James Sterling reports on renewable energy developments, climate policy, ecological conservation, and green tech innovations around the globe.
