It's quite amusing to note that an author who has a book in every Dewey decimal number should consider The Last Question his all-time favorite short story.

That is not to say, of course, that The Last Question is one of Asimov's lesser pieces of fiction, indeed, far from it. The story displays a genius which forces the limits of both science and spirituality to reveal that the two universes share common borders.

The story unfolds as follows: Two computer technicians, having returned in quite a drunken state from a party late one Saturday night, decide to play around with a new artificially intelligent computer that they had recently been appointed to operate. They pose what they feel is an interesting question: Can the fate of humanity be changed? Can entropy be reversed? Multivac replies by saying that there is, as of the moment, insufficient data, and that it will continue its computations. Our next view comes from a hundred years later, a time when anyone has access to Multivac through the use of small communicators. A family on an interstellar voyage ponders the same question, and they pose a query to Multivac. The answer remains the same. In the coming centuries and millennia, the same question occurs to more and more people, as entopy becomes a more immediate problem. At one point, Multivac gets placed into four dimensional hyperspace so that anyone anywhere within our three dimensional universe has access to Multivac with equal convenience. Every time the question is asked, however, Multivac responds by saying that the data does not suffice, and that it will continue its computations. Finally, the heat death of the universe spells the end of life in three dimensions. Multivac, unperturbed, continues to hack at the problem. After an indeterminable amount of time, it finally solves the problem. To answer The Last Question of how entropy may be reversed, Multivac simply says:

"Let there be light."

Although The Last Question remains a memorable piece of science fiction, time travel does not constitute one of its premises. No one zips back and forth in time within the narrative. Instead, time travel is employed as a narrative device, to let people from different points in history to speak with their own voices. It might even conceivably be Asimov himself recounting the tale, although he would need access to the three scientific gizmos (the time machine, the invisibility suit, and the teleportation device) to be able to travel around his universe and witness how the story unfolds so that he may later write it.