Lecture by Prof. Jayant Murthy, Senior Professor, Indian Institute of Astrophysics (IIA), Bangalore
Nightfall is usually considered to be the best science fiction short story ever written. It is set on the planet Lagash in a system with 5 suns. As a result, there is never any darkness except for one day every 2049 years when a combination of planetary motions results in darkness covering the entire planet. Civilization collapses in fire and has to be built again from scratch. Asimov, himself, did not worry about the plausibility of the system but, given the large variety in extra-solar systems, the lecture dwells into the question if such a system would be stable.
The lecture describes the background to the story and then our efforts to find a plausible system, which is now referenced in the Wikipedia article on Nightfall.
