Known Space is the fictional setting of many of Larry Niven's science fiction stories. In general terms it is the name given by humans to the collection of stars and planets near the Earth, out to some 50 light years, which have been explored and settled in the books set in it. 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 some billion years ago).

Warning: Wikipedia contains spoilers

In the process, humankind encounters several intelligent alien species, including:

  • the Kzinti, belligerent giant cat-like aliens with whom the humans fight several brutal wars – mostly offstage until the release of the Man-Kzin Wars short-story collections, largely by other authors;
  • the Outsiders, low-temperature fragile aliens that cruise deep space and trade information, introducing FTL travel to humans;
  • Pierson's Puppeteers, a technologically advanced race of three-legged, two-headed creatures descended from herd animals, and noted for their cowardice;
  • the Pak, interstellar relatives of humanity whose life-cycle evidences the purpose of human old age;
  • the Kdatlyno, a species who see by way of sonar and create sculptures intended to be "felt", seen by Kdatlyno, felt by Humans and licked by Puppeteers;
  • the Thrintun, a long-extinct species which ruled the galaxy through telepathic mind control;
  • the Tnuctipun, used by the Thrintun as genetic engineers;
  • the Bandersnatchi, colossal sluglike creatures, originally created by the Tnuctipun to be grown as a food source by the Thrintun;
  • the Trinocs, named for their three eyes;
  • the Martians, recently extinct;
  • the Grogs, sessile furry cones, which can control animals telepathically.

Also figuring in some stories are intelligent cetaceans and various offshoots of Homo sapiens lineage.

An amusing and interesting aspect of the Known Space universe is that most of the planets colonized by humans are suboptimal for Homo sapiens. The planets were measured and declared habitable by "dumb" robot probes who were then followed by sleeper ships who had to make the best of a bad situation:

  • Plateau in the Tau Ceti system is Venus-like, with a California-sized plateau rising high enough into the dense atmosphere to be habitable
  • Jinx, orbiting Sirius, is a massive moon of a gas giant, stretched by tidal forces into an egg shape, with gravity near the limits of human habitability. The poles lie in vacuum, the equatorial regions are Venus-like (and inhabited by the Bandersnatchi); the zones between have atmosphere breathable by humans. Jinx's poles become a major in vacuo manufacturing area.
  • We Made It orbiting Procyon, got its name because the first colony ship crash-landed. The planet's axis is pointed along the plane of the ecliptic, creating ferocious winds during half of the planet's year, forcing the people to live underground.
  • Warhead was an uninhabitable Mars-like world being used as a military outpost by the Kzinti, until it was hit with an experimental weapon which tore a long, kilometers-deep, but narrow hole into the crust. Most of the planet's atmosphere fell into this artificial canyon, resulting in a breathable environment. The planet was then renamed Canyon, for the crater, and settled by humans in a huge city running up the crater wall.
  • Wunderland is an inhabitable planet circling Alpha Centauri, and was one of the earliest colonies in Known Space's human history.

Asteroid belts are usually extensively colonized in Known Space, as well. Sol's is known as The Belt, while Alpha Centauri's is known as the Serpent Swarm.

The series also features a number of "gee whiz" inventions which figure as plot devices, including invulnerable starship hulls, stasis fields, 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 milieu 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.

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