"The Last Question" is widely regarded by critics and fans as Isaac Asimov's greatest short story. It was also the author's favorite from his own corpus. It is certainly among his most innovatively conceived and finely crafted.
The question in question is "How can the net amount of entropy in the universe be massively decreased?" This is an appropriate ultimate question because entropy, in our present understanding of the cosmos, is the final conclusive phenomenon to which all of existence will reach.
Leonard Nimoy recorded this narration of it in 1966 for the Abrams Planetarium of Michigan State University. His iconic gravely voice was a perfect casting selection, especially since it was toward the beginning of his work in the role of Spock.