A "Green Flash" Sunset: Gone in 60 Seconds | Earth-Sun Science FriendsofNASA.org: One minute sunset with multiple “green flashes.” Location: Big Island, Hawaii, USA Witnessing green flashes at sunset is a rare event that many Sun watchers pride themselves on having seen. Once thought to be a myth, green flashes are now understood to occur when the Earth's atmosphere acts like a prism and a lens. Atmospheric layers create altitude-variable refractions that take light from the top of the Sun, disp