A meteorological optical phenomenon that sometimes occurs transiently around the moment of sunset or sunrise. A green flash usually is seen at an unobstructed horizon, such as over the ocean, but is possible over cloud tops and mountain tops as well.
Green flashes occur because the Earth’s atmosphere can cause the light from the Sun to refract into different colors. When the conditions are right, a distinct green spot is briefly visible above the upper rim of the Sun’s disk; the green appearance usually lasts for no more than two seconds. Rarely, the green flash can resemble a green ray shooting up from the sunset or sunrise point.
The green flash phenomenon was popularised in 1882 by Jules Verne’s novel The Green Ray.