A Science Fiction Novelette first published in Astounding Science Fiction (September 1941 issue) by Isaac Asimov. This story was nominated for the 1941 Retro Hugo Award for short stories in 2016, along with "Robbie" and "Homo Sol".
Theremon 762 is a newspaper reporter who, for two months before the events of this story, has been discrediting the astronomers and their reports of an upcoming eclipse that will end their planet's Endless Daytime. He's there to convince the head of the observatory, Aton 77, to let him write an article about the eclipse from the point of view of the scientists, which provides a character for them to give exposition to.
Theremon and Aton live on Lagash, a planet in orbit around six suns. The story starts with the setting of the fifth sun, Gamma. In four more hours, Beta will be eclipsed by a moon that the astronomers discovered only a few months ago.
Theremon learns from Sheerin 501 about the cycle of civilization and destruction, where cities are burned every two thousand and fifty years. They discuss the Theory of Universal Gravitation, Darkness, and Stars. They're interrupted by the late arrival of two more astronomers, who explain their recent experiment with recreating what they know of the night sky. Then they're interrupted again by a member of the Cult trying to sabotage their equipment.
The eclipse begins, and the astronomers try to record every part of the event. While totality approaches, someone notices a smudge of darkness in the distance; it's the people from the nearest city, who likely have already started going insane. They barricade themselves against the invasion, but totality has arrived, making Beta completely eclipsed — and bringing a terrible cycle full circle, though not for any reasons that any of the characters could have anticipated...
This story has been adapted into episodes of Dimension X (episode fifty), X Minus One (episode twenty-eight), and Escape Pod (episode 100); adapted into films in 1988 and 2000; and adapted into a novel co-written by Robert Silverberg. The setting of Lagash also appeared in a Crossover called "Maureen Birnbaum After Dark", by George Alec Effinger. The original story has been anthologized over forty times, and Isaac Asimov would include it in six of his collections; Nightfall and Other Stories (1969), The Best Of Isaac Asimov (1973), The Edge Of Tomorrow (1985), Other Worlds Of Isaac Asimov (1987), The Asimov Chronicles Fifty Years Of Isaac Asimov (1989), and The Complete Stories, Volume 1 (1990).
"Nightfall" provides examples of:
- Aerith and Bob: "Latimer", the name of the cultist who infiltrates the observatory, is a real-life English surname, unlike Sheerin, Aton, Theremon, or the rest of the cast.
- Alien Sky: Lagash is a planet with six suns and one moon. Every 2,049 local years, the moon eclipses the sole remaining sun on one side of the planet, causing the people of Lagash to go insane and destroy their civilization. The scientists theorize that prolonged darkness, something the Lagashites have normally no experience with, is the culprit. It isn't just the darkness that drives the people insane; it's all the stars in it. Their astronomers had theorized that there might be other star systems, as many as twenty or even a hundred a number which another character whistles at, commenting that it would reduce their world to insignificance. Earth's sky would be enough of a shock, but Lagash is close to the center of the galaxy, and the splendor of a star-packed sky the sudden revelation of how vast the universe really is, and how indescribably tiny they are by comparison — is enough to crush even the most "prepared" mind.
- Apocalypse Anarchy: Lagash has six suns that periodically goes through an eclipse, producing one night of total darkness every couple of thousand years, which terrifies the people on the planet. They burn down their entire civilization in the freakout; then the survivors start over from scratch. By the time of the next eclipse, the only record of the previous one is in mythology.
- Apocalypse Cult: Lagash has a single holy book; the Book of Revelations. This book explains the cycle of destruction and rebirth that occurs over every two millennia. The cycle reaches its peak when the daylight ends and the Stars come out. The Stars "steal the souls of men" and burn down their civilization, causing the cycle to begin again.
- Apocalypse How: Society breaks down every two thousand years because the sight of all the stars in the nighttime sky drives everyone crazy. Entire cities are burned down and every scrap of accessible technology is destroyed.
- Binary Suns: Lagash has six suns, which provide Endless Daytime for the planet.
- Capital Letters Are Magic: When Sheerin 501 explains the new scientific law that the astronomers have figured out, he pronounces the capital letters in "Theory of Universal Gravitation". (It took Lagash scientists four hundred years to figure out Isaac Newton's theory, because they only had the six suns to work with — no visible planets or moons.)
- Chromosome Casting: Women and children are mentioned off-screen, but all of the on-screen characters are adult men.
- Claustrophobia: Due to their Endless Daytime, the people of Lagash are so afraid of the dark that 15 minutes without light is enough to cause a 10% chance of becoming permanently extremely claustrophobic. They discovered this pattern with a theme park ride called "The Tunnel of Mystery" that was just a short ride through a dark tunnel.
- Cosmic Horror Story: On the planet Lagash, the sky is always lit by at least one of the six suns for over two thousand years, until an eclipse. The concept of "darkness" is so foreign to them that one of the characters needs the concept explained, and torches are an experimental new technology. These eclipses have seemed to coincide with the collapse of past civilizations. A new scientific theory postulates that the night sky, and its resultant darkness has driven every previous civilization mad. On the eve of the next eclipse, the citizens of Lagash are about to find out whether this theory is correct. Though there's no Eldritch Abominations, supernatural / otherworldly intelligences, unfathomable godlike beings or any such things typically found in such stories; just a brilliant starry night of the sort which we on Earth might take for granted, but which forces the Lagashians to realise that, far from being the center of everything, they're actually just a very small part of an unimaginably bigger universe.
- Double-Blind What-If: As the story begins, the discovery of how gravity works is an extremely recent breakthrough that's revolutionized all of science. When Sheerin explains it, Theremon notes what a simple concept it is. Sheerin agrees, saying that it only took so long because they needed advanced telescopes to track some pretty minute wobbles in the motions of Lagash's suns. Sheerin then, as a thought experiment, proposes a planet with only one sun, saying that its hypothetical inhabitants would probably develop the theory much quicker, as they could observe the sun regularly going up and down with no telescopes required, just the naked eye.
- Earth Is the Center of the Universe: Subverted. The people of Lagash believed the universe to consist entirely of their world and its six suns. More even than the Darkness, it is seeing the stars beyond their own and the consequent revelation of how utterly insignificant they truly are that drives the people of Lagash irreversibly insane during the Nightfall.
- Eternal Recurrence: On Lagash, the sky is always sunlit due to the six suns that Lagash orbits inside of. Once every 2,049 years, when only one of the suns are in the sky, an eclipse covers the remaining star, plunging the world into darkness. This natural phenomenon causes everyone to go mad and start burning everything to generate whatever light they can, inadvertently returning civilization to the stone age. The twist is that the darkness is bad enough, but it's the appearance of the stars in numbers that no one on the planet can comprehend and the revelation of how insignificant they are that drives everyone crazy.
- Endless Daytime: Lagash is a planet whose star system has six suns. As a result, the planet is illuminated all the time. Well, almost. The climax occurs when the only sun left in the sky is eclipsed by a moon.
- Epigraph: The story is usually reprinted with a quote from Ralph Waldo Emerson preceding it, due to the way his quote inspired Dr Asimov to write a story about stars that only appear once every thousand years."If the stars should appear one night in a thousand years, how would men believe and adore, and preserve for many generations the remembrance of the city of God which had been shown!"
- Fantastic Naming Convention: The inhabitants of planet Lagash all have a name followed by a number, e.g. Sheerin 501, Beenay 25, etc.
- First Time in the Sun: Inverted Trope, because Lagash has six suns, creating Endless Daytime, and the climax occurs when the last sun in the sky is eclipsed, causing the first nighttime in over two thousand years. Also a Subverted Trope, because instead of being awed, as the Emerson quote that inspired the story suggests, a civilization-ending panic and insanity outbreak ensues.
- Go Mad from the Revelation: Lagash's six suns means an Endless Daytime, except for once every 2,049 years, when five suns set and the only sun left in the hemisphere is eclipsed by the moon. The scientists are trying to prepare civilization and themselves for the upcoming nightfall, but when it does occur, no-one is prepared for the thirty thousand Stars that suddenly appear in the night sky. This leads to the far more devastating revelation of how tiny and insignificant they are by comparison.
- Ignored Expert: The astronomers have been mocked for their doom-sayings, having announced a "dark body" that will eclipse Beta after the other five suns have set. One of the newspaper reporters who has been mocking them actually comes to get their side of the story during their announced eclipse, so that he can get the scoop on why they were wrong (and hedging his bets to get an even better story in case they were right).
- Irony: The characters are frantically trying to prepare society for the terrible effects that a sudden plunge into total darkness might have on a civilisation that knows only ever-present light. However, it turns out that the catalyst for driving everyone mad isn't so much the darkness, but the millions of smaller lights that suddenly appear when the stars can be seen, leading everyone to realise that far from being the centre of the universe, their world is actually very small and insignificant indeed.
- Just Before the End: Lagash is a pretty decent place to live, with a technology level about equal to Mid 20th Century America. The main difference between it and Earth is that there are six suns in the sky, causing darkness to be all but unknown on the world. Astronomers from a major University announce that five suns will set and an eclipse will cover the one remaining sun, plunging the hemisphere into darkness. The story ends with night falling for the first time in over 2000 years, and people going mad all over the planet.
- Madness Mantra: At the end of the short story, when five of the suns set and the last one is eclipsed by Lagash's moon, Aton begins to turn into a panicked madman, repeating his words frenetically." Stars — all the Stars — we didn't know at all. We didn't know anything. We thought six stars in a universe is something the Stars didn't notice is Darkness forever and ever and ever and the walls are breaking in and we didn't know we couldn't know and anything — "
- Most Writers Are Human: This story takes place on an alien planet, with humans-from-other-planets as the aliens so that their plight resonates with the reader.
- Most Writers Are Writers: Theremon 762 is a newspaper reporter who has come to the astronomy tower to report on the eclipse, and he's used as an audience proxy, providing someone the astronomers can explain things to.
- A Mythology Is True: Aton angers the cultists because after allowing him access to their holy scriptures, he used the evidence to prove the upcoming Darkness is due to an eclipse. The cultists are angry that their religion is being used to prove a scientific conclusion rather than a spiritual one.
- The Name Sake: The characters spend the story preparing for an eclipse of the last sun in the sky, plunging the world of Endless Daytime into the first night in 2,049 years. The characters can't even Title Drop the event, saying instead that Lagash will "enter a cave of Darkness".
- One-Word Title: "Nightfall", after the once-in-millennia event that dominates the story.
- Set the World on Fire: People set their cities aflame when darkness comes (about every 2,000 years) in order to get light And blot out the thirty-thousand stars visible in their nightsky.
- The Stars Are Going Out: (Inverted Trope) When the six suns of Lagash all set (or are eclipsed), which happens every 2,049 years, the population goes utterly insane and destroys civilization. The protagonists speculate that the blackness of night drives the people mad; in fact, they go mad when they look up at the night sky and see the thirty thousand stars around their little solar system (they are near the center of a globular cluster) and realize how much larger the universe is than they ever imagined, and how insignificant they are within it.
- Stealth Pun: The advanced society regresses to barbarism once the light from all six of their planet's suns are blocked. In other words, they enter a literal Dark Age.
- A Tale Told by an Idiot: The Sacred Scripture of the local Apocalypse Cult is explicitly one of these. Sheerin and Theremon discuss who it was that could have written down the original Book of Revelations. Once the civilization had been destroyed through everyone going mad, the only people coherent enough to recount what happened will be either children too young to consider the Night as something truly terrible, or someone who didn't have a lot of intelligence and sanity to begin with. Few take the Cult's warning seriously.
- Total Eclipse of the Plot: Lagash is a world with six suns, whose inhabitants have never known darkness of any kind, as there is always at least one sun visible at any given moment. When a once-in-2049-years eclipse occurs and plunges their world in darkness, the vast majority go completely bonkers.
- The Watson: Theremon 762 is a newspaper reporter who has come to the astronomy tower to report on the eclipse, and he's used as an audience proxy, providing someone the astronomers can explain things to.