Green Flash

A green flash is a refractive phenomenon in which the top edge of the setting—or, less frequently, rising—sun momentarily turns emerald green. It is usually seen over a low distant horizon, such as that of the ocean or a prairie, when the sky is clear. It occurs primarily because the atmosphere acts like a weak prism, refracting sunlight and separating it into different colors. The green color lasts from a fraction of a second to two seconds. What is a green rim and when can it be observed? More...

A green flash is a phenomenon in which part of the sun appears to suddenly change color for about 1 or 2 seconds. The brief flash of green light is seen more often at sunset than at sunrise.

This fleeting spectacle is caused by the refraction of sunlight, which is particularly significant at sunset and sunrise when the light travels through more of the Earth's atmosphere. The atmosphere bends the sunlight passing through it, separating the light into its different colors, much like a prism bends and splits sunlight into rainbows, according to Cornell University.

The various colors of light bend different amounts based on their wavelengths; shorter wavelengths (blue, violet and green) refract more strongly than longer wavelengths (yellow, orange and red). As such, blue and violet light are scattered by the atmosphere while red, orange and yellow are absorbed, leaving the green light the most visible during the few seconds when the sun sets below or rises above the horizon.

A green flash is a refractive phenomenon in which the top edge of the setting—or, less frequently, rising—sun momentarily turns emerald green. It is usually seen over a low distant horizon, such as that of the ocean or a prairie, when the sky is clear. It occurs primarily because the atmosphere acts like a weak prism, refracting sunlight and separating it into different colors. The green color lasts from a fraction of a second to two seconds.