"The Last Question" Planetarium Show by Isaac Asimov

Rumble — The story deals with the development of a series of computers, Multivac, and its relationships with humanity through the courses of seven historic settings, beginning on the day in 2061 that Earth becomes a planetary civilization. In each of the first six scenes, a different character presents the computer with the same question, how the threat to human existence posed by the heat death of the universe can be averted: "How can the net amount of entropy of the universe be massively decreased?" That is equivalent to asking, "Can the workings of the second law of thermodynamics (used in the story as the increase of the entropy of the universe) be reversed?" Multivac's only response after much "thinking" is "INSUFFICIENT DATA FOR MEANINGFUL ANSWER."

The story jumps forward in time into later eras of human and scientific development. In each era, someone decides to ask the ultimate "last question" regarding the reversal and decrease of entropy. Each time that Multivac's descendant is asked the question, it finds itself unable to solve the problem, and all it can answer is (linguistically increasingly-sophisticated) "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER."

In the last scene, the god-like descendant of humanity, the unified mental process of over a trillion, trillion, trillion humans who have spread throughout the universe, watches the stars flicker out, one by one, as matter and energy end, and with them, space and time. Humanity asks AC, Multivac's ultimate descendant that exists in hyperspace beyond the bounds of gravity or time, the entropy question one last time, before the last of humanity merges with AC and disappears. AC is still unable to answer but continues to ponder the question even after space and time cease to exist. AC ultimately realizes that it has not yet combined all of its available data in every possible combination and so begins the arduous process of rearranging and combining every last bit of information that it has gained throughout the eons and through its fusion with humanity. Eventually AC discovers the answer - that the reversal of entropy is, in fact, possible - but has nobody to report it to, since the universe is already dead. It therefore decides to answer by demonstration, since that will also create someone to give the answer to. The story ends with AC's pronouncement:

And AC said: "LET THERE BE LIGHT!" And there was light