The Fermi paradox is the discrepancy between the lack of conclusive evidence of advanced extraterrestrial life and the apparently high likelihood of its existence. As a 2015 article put it, "If life is so easy, someone from somewhere must have come calling by now."
Apocalyptic and post-apocalyptic fiction is a subgenre of science fiction in which the Earth's civilization is collapsing or has collapsed. The apocalypse event may be climatic, such as runaway climate change; astronomical, such as an impact event; destructive, such as nuclear holocaust or resource depletion; medical, such as a pandemic, whether natural or human-caused; end time, such as the Last Judgment, Second Coming or Ragnarök; or any other scenario in which the outcome is apocalyptic, such as a zombie apocalypse, cybernetic revolt, technological singularity, dysgenics or alien invasion.
Colonization is a trilogy of alternate history books by American writer Harry Turtledove. It is a series continuation of the situation set up in the Worldwar tetralogy, projecting the situation between humanity and The Race nearly twenty years afterward, in the mid-1960s.
The concept of self-replicating spacecraft, as envisioned by mathematician John von Neumann, has been described by futurists including physicist Michio Kaku and discussed across a wide breadth of hard science fiction novels and stories. Self-replicating probes are sometimes referred to as von Neumann probes. Self-replicating spacecraft would in some ways either mimic or echo the features of living organisms or viruses.
The Great Filter is the idea that in the development of life from the earliest stages of abiogenesis to reaching the highest levels of development on the Kardashev scale, there is a barrier to development that makes detectable extraterrestrial life exceedingly rare. The Great Filter is one possible resolution of the Fermi paradox.
Homeward Bound (2004) is a science fiction and alternate history novel by Harry Turtledove. It is the eighth and final work in his Worldwar series fictional universe. It follows the events of the Colonization trilogy and gives some closure to the storylines.
Colonization: Second Contact is an alternate history novel by American writer Harry Turtledove. It is the first novel of the Colonization series and the fifth installment in the Worldwar series.
Worldwar: In the Balance is a 1994 alternate history novel by American writer Harry Turtledove. It is the first novel of the Worldwar tetralogy, as well as the first installment in the extended Worldwar series that includes the Colonization trilogy and the novel Homeward Bound. The plot begins in late 1941, while the Earth is torn apart by World War II. An alien fleet arrives to conquer the planet, forcing the warring nations to make uneasy alliances against the invaders. Meanwhile, the aliens, who refer to themselves as the Race, discover that their enemy is far fiercer and more technologically advanced than expected.
Worldwar: Tilting the Balance is an alternate history novel by the American writer Harry Turtledove. It is the second book in the Worldwar tetralogy and in the extended Worldwar series, which includes the Colonization trilogy and the novel Homeward Bound.
Worldwar: Upsetting the Balance is an alternate history novel by American writer Harry Turtledove. It is the third novel of the Worldwar tetralogy and the third installment in the extended Worldwar series, which includes the Colonization trilogy and the novel Homeward Bound.
Worldwar: Striking the Balance is an alternate history novel by American writer Harry Turtledove. It is the fourth and final novel of the Worldwar tetralogy and the fourth installment in the extended Worldwar series, which includes the Colonization trilogy and the novel Homeward Bound.
The planetary systems of stars other than the Sun and the Solar System are a staple element in many works of the science fiction genre.
"The Road Not Taken" is a science fiction short story by American writer Harry Turtledove, in which he presents a fictitious account of a first encounter between humanity and an alien race, the Roxolani. Turtledove wrote a sequel, a short story entitled "Herbig-Haro".
Colonization: Down to Earth is an alternate history and science fiction novel by Harry Turtledove. It is the second novel of the Colonization series, as well as the sixth installment in the extended Worldwar series. British editions are entitled Colonisation: Down to Earth and are the second of the Colonisation series.
Colonization: Aftershocks is an alternate history and science fiction novel by Harry Turtledove. It is the third and final novel of the Colonization series and the seventh installment in the extended Worldwar series.
The Looking Glass, or Voyage of the Space Bubble, series is a military novel series created by author John Ringo and centering on the creation of trans-space portals known as "looking glasses" and the effect their discovery and the discovery of things via the portals have on life on Earth and off it. Ringo wrote the first book in the series alone, and has collaborated with physicist and author Travis S. Taylor beginning with the second book in the series. Books in the series are phrases taken from the poem Jabberwocky.
"Vilcabamba" is a 2010 science fiction short story by Harry Turtledove, notable both for its content and for the writer's unusual decision to publish it free online on tor.com and thus waive the royalties from its publication. The story would later be reprinted in Turtledove's short-story collection The Best of Harry Turtledove in 2021.
Bibliography of science fiction, fantasy, historical fiction and nonfiction writer Harry Turtledove:
