
"The Last Question" is a science fiction short story by Isaac Asimov, first published in Science Fiction Quarterly in November 1956. Asimov considered it his favorite of all his own works. Told in seven vignettes spanning billions of years, the story follows humanity's recurring attempts to answer a single question: can entropy be reversed? It begins in 2061, when two technicians drunkenly pose the question to Multivac — a vast supercomputer that has just solved Earth's energy crisis. The story then leaps forward through the ages. Civilization spreads across galaxies, merges with its machines, and eventually transcends physical form entirely. Yet across all this time, the question goes unanswered. Every iteration of the computer, growing ever more powerful and abstract, can only respond: "THERE IS AS YET INSUFFICIENT DATA FOR A MEANINGFUL ANSWER." At the end of time, with the universe cold and dark and humanity long dissolved into a collective consciousness, the last mind poses the question one final time — then ceases to exist. Only the computer remains, alone in hyperspace, still working on the problem. When it finally finds the answer, there is no one left to hear it. So it does the only logical thing. Few short stories attempt to cover several trillion years of history. Fewer still stick the landing.
https://users.ece.cmu.edu/~gamvrosi/thelastq.html
tl;dr: likely as long as the lifespan of the universe.
Asimov's 'The Last Question' is another good one that's in line: https://users.ece.cmu.edu/~gamvrosi/thelastq.html
> After all, I undertook to tell several trillion years of human history in the space of a short story and I leave it to you as to how well I succeeded. I also undertook another task, but I won't tell you what that was lest l spoil the story for you.
I also liked a couple stories from Ted Chiang's Stories of Your Life and Others.
I did not know about this. Arthur C Clarke was indeed my favourite at that time (even now).
Asimov, however, killed it with his two goosebump-good shorts, Nightfall and Last Question.
(Asimov's is better. Also, the version of this one in my memory is better than the actual story, in that "There is now" is better than the rather clunky equivalent in the story. I suppose it's possible that I'm remembering a different, slightly better written, story with the exact same idea.)