Asimov's Nightfall

A classic science fiction novel, Nightfall was first published as a short story in the September 1941 issue of Astounding Science Fiction, written after some friendly persuasion by the editor of the magazine - John W. Campbell. The story was later adapted into a complete novel, and one that was acknowledged to be an incredible piece of science fiction (but it was not just science fiction, but a psychological look at a society when it suddenly encounters a very changed environment and raises questions about how humans respond to unknown stimulus). The influence and power of this story was such that it was declared in 1968 as the best science fiction short story ever written prior to the establishment of the Nebula Awards (the awards were established in 1965) by the Science Fiction Writers of America.


Nightfall has a pretty simple story. The story deals with human (like) society on an alien planet Lagash (Kalgash in the novel adaptation) that has a unique sky. It has a total of 6 suns all around it the stellar configuration (the various suns being Onos, Dovim, Trey, Patru, Tano, and Sitha). Because of these 6 suns, the planet is always in light and the inhabitants have not known darkness. They are so habituated to always having light that standing a time of darkness can be unnerving for most people. For example, a new amusement park ride that promises a time of total darkness has scared and traumatized many people.
The story has 3 main plots that all move to the same merger. There are the archaeologists who make the discovery that the ground strata of the planet seems to indicate that civilization builds up and then destroys itself, and that this has not happened once, but seems to keep on happening in a cycle. The researches are puzzled as to why such a thing keeps on happening, after all, most civilizations advance and maybe stagnate, but don't keep on going through a repetitive cycle of advance and decline.
Similarly, physicists discover that the there are irregularities in the orbit of Kalgash around its primary sun Onos. After more studies, the conclusions that they keep on heading towards is a horrifying one. The discovery is that the planet has a so far unknown satellite that causes the irregularities, and plotting the orbits of the planet, the satellite and the 6 suns lead to a conclusion that just cannot be true. After all, everybody knows that the planet has always had sunlight, so how can there be a time of many hours when the suns and the satellite reach a position where there is no light on the planet. Such a situation can cause mass hysteria and madness.
And then there is the political angle. There is a group known as the Apostles of the Flames, that calls itself as an ancient society; their belief (like a religious belief) is that civilization dies out with the appearance of darkness and then the stars that unleash fire. They are trying to gain more authority and political power.
These 3 combine together to reach a conclusion - every 2,049 years, the sole sun on one side of the planet is eclipsed for half a day, and this is a time when society (never having experience darkness) will go through madness and anarchy, with fire and chaos.
The rest of the novel is about this time coming closer, and then what happens when that time appears. This is a fascinating propounding of the state of the human mind, its irrationality in believing weird faiths and religious fervor when faced with a new thing.