What is the main conflict in Nightfall by Isaac Asimov?

"Nightfall" is a story about a planet that does not experience nightfall except once in every 2,049 years. On a planet where darkness is unknown, the expectation is that everyone will go insane from fear and claustrophobia, and that in their fear they will try to burn anything that will catch fire in order to produce light. Archaeological evidence has shown that about every 2,000 years, on at least nine different occasions, whole civilizations have disappeared. The assumption is that the fires get out of hand and everything is destroyed in the chaos of madness. To prevent the panic and help people prepare so that they might survive the next eclipse, the scientists are determined to leave proof of the real reason for the coming of the darkness.