“The capriciousness of the flash led some scientists to suggest it was a purely physiological phenomenon rather than a physical one. . . . It is true that if you close your eyes after looking at a bright red light the afterimage will be greenish. Those who held to this explanation clearly had never personally beheld the green flash. The afterimage from retinal fatigue is a dull complementary image that only slowly fades after some tens of seconds. The green flash is a brilliant emerald tint that lasts for only a split second before it too follows the set sun below the horizon.”

—Aden & Marjorie Meinel, Sunsets, twilights, and evening skies, 1983.