The Known Space stories span approximately a thousand years of history, from the first human explorations of our solar system to the colonization of dozens of nearby systems (and with references to events of a billion years ago!).
In the process, humankind encounters a half-dozen intelligent alien species, including:
- Pierson's Puppeteers - two-headed, cowardly and conspiratorial but technologically hyperadvanced
- the Kzinti - belligerent giant cat-like aliens with whom the humans fight several brutal wars (mostly offstage until the advent of the "Man-Kzin Wars" series of stories by other authors).
- the Outsiders - low-temperature fragile aliens that trade information and cruise deep space
- the Thrint - long-extinct telepathic galactic overlords
Also figuring in some stories are intelligent cetaceans and various offshoots of Homo sapiens' lineage.
The series also features a number of "gee whiz" inventions which figure as plot devices, including invulnerable starship hulls, transporter booths (used only on planetary surfaces), the lifespan-extending drug "boosterspice", and the "tasp" which is capable of stimulating the pleasure centers of the brain from a distance. The mileau can be viewed as representing the climax of the pre-cyberpunk era of science fiction, as the cyberpunk themes of information technology and competition of various sub-governmental groups do not figure in the stories.
An amusing and interesting aspect of the Known Space universe is that most of the planets colonized by humans are suboptimal for Homo sapiens (They were declared habitable by dumb robot probes and then colonized by generation ships). The planet Plateau in Tau Ceti system is Venuslike, with only a California-sized plateau rising high enough into the atmosphere to be habitable. Jinx, orbiting Sirius, is a massive moon of a gas giant, with gravity near the limits of human habitability and stretched by tidal forces into an egg shape, with a breathable atmosphere near the "poles" and the equatorial regions shrouded in dense murk (and inhabited by the dinosaurian native "Bandersnatchi"). Warhead was an uninhabitable Marslike world, the site of a Kzinti advance base until the humans hit it with an experimental weapon which tore a kilometers-deep gash into the crust. Most of the planet's atmosphere falls into this artificial crater, resulting in a breathable environment, and the planet is renamed Canyon and settled by humans.
Timeline of the Known Space universe.