Flight To Forever, Poul Anderson, 1950

Anderson’s classic story of one-way time travel. You can go forward but not all the way backwards, and the stalwart 1950s protagonist, Martin Saunders, keeps skipping himself forward, along the surface of an infinite lake, hoping to find some civilization that has perfected backwards time travel so that he can return home to his girlfriend: the conveniently named Eve. He companion is killed in 2500 A.D., and he acquires a new one who searching the future for a sufficiently violent time that will have use for his martial skills. Martin stops in 50,000 A.D. and helps the Galactic Empress regain her throne, and is sent on alone into the future for his trouble. The human race eventually falls, and he is the last human man on Earth. Other races rise, but they are unable to help him. Eventually, weakly godlike entities upgrade his time machine to get him “home,” by having him dive ever deeper into the future. He sees the moon shatter and fall from the sky, the sun wither and die, and finally the heat-death of the entire universe, only for it to be reborn. Saunders keeps traveling, taking the longest way around. The universe is perfectly cyclical. He travels forward until he reaches the point at which he left, settling for the fretful girl who is certainly no beautiful Galactic Empress.

Saunders becomes The Last and First Man, cushioned on each end by millions of years. The exactly perfect cyclical universe is a bleak concept, a black pit of despair that for Neitzsche was the nightmare of being doomed to repeat every mistake you’ve ever made over and over again for eternity. But Anderson goes further than The Eternal Return, stripping uncertainty and free will from his minutely machined universe loop. It would take only the smallest of quantum hiccups in the deep past for conditions to change enough for Saunders to never have been born, or not a physicist, or or or. Anderson’s cold reality is stuck on repeat, growing more boring with every repetition of the same trillion trillion triliion sub-atomic events in perfect timing and order.

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