Nightfall

by Robert Silverberg

The planet Lagash ("Kalgash" in the novel) is constantly illuminated by at least one of the six suns of its multiple star system. Lagash has areas of darkness (in caves, tunnels, etc.), but "night" does not exist.

A skeptical journalist visits a university observatory to interview a group of scientists who warn that civilization will soon end. The researchers explain that they have discovered evidence of numerous ancient civilizations on Lagash, all destroyed by fire, with each collapse occurring about 2,000 years apart. The religious writings of a doomsday cult claim that Lagash periodically passes through an enormous cave where mysterious "stars" appear. The stars are said to rain down fire from the heavens and rob people of their souls, reducing them to beast-like savages.

The scientists use this apparent myth, along with recent discoveries in gravitational research, to develop a theory about the repeated collapse of society. A mathematical analysis of Lagash's orbit around its primary sun reveals irregularities caused by an undiscovered moon that cannot be seen in the light of the six suns. Calculations indicate that this moon will soon obscure one of Lagash's suns when it is alone in the sky, resulting in a total eclipse that occurs once every 2,000 years. Having evolved on a planet with no diurnal cycle, Lagashians possess an intense, instinctive fear of the dark and have never experienced a prolonged period of widespread darkness. Psychological experiments have revealed that Lagashians experience permanent mental damage or even death after as little as 15 minutes in the dark, and the eclipse is projected to last for several hours.

The scientists theorize that earlier civilizations were destroyed by people who went insane during previous eclipses and—desperate for any light source—started large fires that destroyed cities. Oral accounts of the chaos from crazed survivors and small children were passed down through the ages and became the basis for the cult's sacred texts. Present-day civilization is doomed for the same reasons, but the researchers hope that detailed observations of the upcoming eclipse will help to break the cycle of societal collapse.

The scientists are unprepared, however, for the stars. Because of the perpetual daylight on Lagash, its inhabitants are unaware of the existence of stars apart from their own; astronomers believe that the entire universe is no more than a few light years in diameter and may hypothetically contain a small number of other suns. But Lagash is located in the center of a "giant cluster," and during the eclipse, the night sky—the first that people have ever seen—is filled with the dazzling light of more than 30,000 newly visible stars.

Learning that the universe is far more vast—and Lagash far more insignificant—than they believed causes everyone, including the scientists, to go insane. Outside the observatory, in the direction of the city, the horizon begins glowing with the light of spreading fires as "the long night" returns to Lagash.