For Day #8 of Short-Story Month, here are some takes on two of the most popular themes in speculative fiction: Time travel and Immortality.

For starters, two of the twistiest time-travel stories Robert A. Heinlein wrote: “By His Bootstraps” (1941) and “All You Zombies,” (1959). No spoilers here, but both involve time paradoxes. In “All You Zombies,” at least one character is intersex. Heinlein considered “Zombies” one of his favorites of his stories and he included it in the 1963 author’s choice anthology “The Worlds of Science Fiction.”  All of Heinlein’s short stories are good reads.

Time travel was a regular theme of author Jack Finney in novels like “Time and Again,” and short stories like “The Third Level.” Writing in the 1950s, many of Finney’s stories evoke the past as innocent and nostalgic. But not always; “Such Interesting Neighbors” deals with refugees from the future, and time begins to go haywire in “I’m Scared.” If Jack Finney isn’t a household name, some of his stories are; he wrote “Invasion of the Body Snatchers.”

Immortality has been a theme in fiction for as long as it’s been a dream of humankind. There have been at least two stories that take that statement literally. L. Sprague DeCamp’s “The Gnarly Man” is about Gaffney, a man seeking medical attention for his leg, which was broken and never set right a long, long, long time ago. Gaffney is an immortal Neanderthal who inspired the legends of the crippled Roman god Vulcan. There are at least two stories about immortal cavemen; the other is “Old Man Mulligan” by P. Schuyler Miller. (One of them might have created Vandal Savage, the immortal caveman who became a Sumerian king and fought the Justice Society in the 1940s comic books. But I digress.)

The 1998 anthology “Immortals,” edited by Jack Dann and Gardner Dozois includes an introduction where the editors speculate that since, a century ago people were lucky to make it through their thirties, we are living in an era of greatly extended life.

We may not have found immortality, but that is close.