British physicist Jim Al-Khalili, author of "On Time: The Physics That Makes the Universe Tick," discusses why time flows in only one direction, and why time travel into the past is highly unlikely - but not yet completely ruled out.

Cinematographer Brendan Uegama discusses how he and his teammates created a fictional world for "Star City," an Apple TV series that traces a dramatically different version of the U.S.-Soviet space race.

A podcast double-feature delves into scientific and social issues raised by the "Disclosure Day" movie. Our guests are Adam Kirsch, author of "We Want to Believe"; and Meg Charlton, author of an alien-abduction novel titled "Voyagers."

Nisi Shawl discusses the genesis of "The Curve of the World," a newly published novel about an ancient odyssey from Crete to the Pacific Northwest that science-fiction pioneer Vonda N. McIntyre finished writing just before her death in 2019.

SETI astronomer Seth Shostak talks about the parallels between the alien connection in "Project Hail Mary" and the real-world search for signs of extraterrestrial intelligence.

Now Elon Musk wants to build a city on the moon before building a city on Mars. Biologist Scott Solomon, author of a new book titled "Becoming Martian," sizes up the prospects for building a city anywhere that's beyond Earth.

Aerospace consultant Roger Myers explains why space nuclear power will play a big role in the competition between the U.S. and China to establish bases on the moon in the 2030s.

Space scientist Les Johnson tells the story behind his role in creating "Pluto," the last novel in sci-fi master Ben Bova's Grand Tour series and one of the first works of fiction to incorporate revelations from NASA's New Horizons mission.

Cherokee science-fiction author Daniel H. Wilson blends ancient tales about extraterrestrials with up-to-date speculation about alien visitations in a new novel called "Hole in the Sky."

Washington Post staff writer Christian Davenport, author of "Rocket Dreams," discusses the parallel space races between America and China, and between Elon Musk and Jeff Bezos.