Spacers were the fictional first humans to emigrate to space in Isaac Asimov's Robot and latterly related Foundation and Empire series. In these stories, about a millennium thereafter, they severed political ties with Earth, and embraced low population-growth and extreme longevity (with lifespans reaching 400 years) as a means for a high standard of living, in combination with using large numbers of robots as servants. At the same time, they also became militarily dominant over Earth.
Asimov's novels chronicle the gradual deterioration of the Spacer worlds and the disappearance of robots from human society. The exact details vary from book to book, and in at least one case—the radioactive contamination of Earth—later scientific discoveries forced Asimov to retroactively reconfigure his own future history. The general pattern, however, is as follows:
In the vague period between Asimov's near-future Robot short stories (of the type collected in I, Robot) and his novels, immigrants from Earth establish colonies on fifty worlds, the first being Aurora, the last Solaria, and all fifty inscribed in the Hall of the Worlds located on Melpomenia, the nineteenth. Sociological forces possibly related to their sparse populations and dependence on robot labor lead to the collapse of most of these worlds; their dominance is replaced by new, upstart colonies known as "Settler" worlds.
In Foundation and Earth, Golan Trevize visits several of these worlds. We learn the eventual fate of Aurora, setting of The Robots of Dawn, and also Solaria, the setting of its predecessor The Naked Sun.
Known Spacer worlds
Although Asimov never listed all the fifty Spacer worlds, some of them can be inferred from the author's and others' novels and short stories. Some of them are:
- Acrisia (from Mark W. Tiedemann's Mirage)
- Capella (from Mark W. Tiedemann's Chimera)
- Hesperus - the smallest and furthest from Earth, it was colonized by Spacers from Faunus (from the novelette "Mother Earth")
- Inferno (from Roger MacBride Allen's Caliban trilogy)
- Keresia (from Mark W. Tiedemann's Chimera)
- Melpomenia (from Foundation and Earth)
- Osiris (from Mark W. Tiedemann's Chimera)
- Pallena (from Mark W. Tiedemann's Mirage)
- Proclas (from Mark W. Tiedemann's Chimera)
- Saon (from Mark W. Tiedemann's Mirage)
- Solaria, colonized by Spacers from the nearby planet Nexon
- Theia (from Mark W. Tiedemann's Chimera)
In Asimov's short-story collection I, Robot, it is mentioned that the first extra-solar Earth colonies had recently been settled, in the wake of Gregory Powell and Mike Donovan's initial historic hyperspatial jump in "Escape!". In the novel The Robots of Dawn, it is established that the planet Aurora was originally known as "New Earth," during the first few centuries following its colonization by Earthmen (in the Tau Ceti star system), and was the first planet settled by Man outside of Earth's solar system. Therefore, it can be inferred that Aurora/New Earth is that same very first extrasolar colony settled during the timeframe of the stories featured within I, Robot, during the mid-21st Century.
Asimov's novel Nemesis hints that the Spacers may have been descendants of human beings selected by a non-human intelligence for their mental characteristics. However, except for a brief mention in Forward the Foundation, the Nemesis plotline is entirely unlinked with the rest of Asimov's science-fiction canon. (The internal logic of the Robot-Empire-Foundation saga demands that robots be present on Earth prior to the Spacer worlds' colonization, yet Nemesis contains no robots, making the continuity difficult to accept.)
Further, another story within the story arc establishes the Spacers' mastery of myco-food (food derived from fungi), which they then retain all through history up to their inclusion in the Imperium on Trantor in the sector of Mycogen. The Spacers' control of myco-food makes the farming operations of Solaria seem more puzzling, until we remember that Solaria was aberrant even by Spacer standards and remained so in the later book Foundation and Earth as a real example of menace to the Second Foundation itself.
In a somewhat similar vein, Mark W. Tiedemann's "Robot Mystery" trilogy also portrays the Spacers as a group genetically distinct from Earthpeople and their Settler descendants. Tiedemann's trilogy, set between The Robots of Dawn and its sequel Robots and Empire, attempts to update Asimov's work to reflect more recent scientific and science-fictional speculation, for example explaining the lack of nanotechnology in Asimov's robot-ridden society. According to Tiedemann's Aurora (2002), the cumulative effects of genetic alterations (due partly to nanotech devices since abandoned) separated Spacers from the rest of humanity, to such an extent that the word "human" in the Three Laws of Robotics may no longer apply to them. In Robots and Empire, Gladia stated Spacers are too genetically different from Earthmen to interbreed, although it was never proved. This might explain why the remnant of Aurorans failed to dissolve in the wider population even after twenty thousand years.
Settlers are human colonists that replaced the earlier Spacer emigrants who were in dominance in the vague period between Robot series near-future short stories (of the type collected in I, Robot) and novels.
Emigrants from Earth establish colonies on fifty worlds, the first being Aurora, the last Solaria, and the Hall of the Worlds located on Melpomenia, the nineteenth. However, sociological forces possibly related to their sparse populations and dependence on robot labor lead to the collapse of most of these worlds; their dominance is replaced by new, upstart colonies known as Settler worlds in the Milky Way galaxy. Comporellon was the first colonized world of the Settlers. Unlike their Spacer predecessors, the Settlers detested robots, and so by the time of the Empire series, robotics is almost an unknown science.
The Settlers were born from a movement founded by noted Earth hero and police officer Elijah Baley, who had some years earlier, become the first Earth born human in centuries to travel beyond Earth (to the Spacer colony world Solaria and later colony Aurora to investigate murders) and to walk under open skies as opposed to remaining in the underground cities all Earthmen then lived in. The experience of doing so had a profound effect on Baley, who upon his return from Solaria, he began gathering young risk takers, willing to reject the stasis of life within the cities and struggle against the now culture wide agoraphobia now experienced by all Earth born humans. Over time the movement began to grow and progressed from simply practicing to overcome the agoraphobia and began studying manual agriculture, determined to learn how to survive without robotic aid.
The governments of Earth took a dim view of Baley's movement, but his status as a hero to the public and his political connections with the Spacers kept the early Settlers unmolested and they gradually grew to become a major force in Earth's politics and led by Baley's son Ben Baley they managed to achieve their goal, settling what would be named 'Baleyworld'. From there the Settler's expanded with a far greater speed than the Spacers ever demonstrated and soon surpassed their long living cousins in number of planets held, if not in technology, which prompted concern and threats from the conservative side of the Spacer government.
Unlike the Spacers who took a haughty view of Earth, the Settlers revered the Homeworld, turning to Earth to arbitrate any disputes between them and believing their connection to Earth's past made them superior to the advanced but now stagnant Spacers.
In the novel The Robots of Dawn, Asimov reveals why the majority of Settlers came from the short-lived Earth population, as opposed to Spacer worlds, which would have used humaniform robots in the process.
By the time of the sequel, Robots And Empire, the number of the Settler worlds exceeded a hundred ("about half" of the "hundreds of... planets... recorded and studied").
(In Asimov's novel Nemesis, the main colony is a member of the collection of orbital colonies known as the Fifty Settlements. It should not be confused with the later Settlers that are the matter of this article, as it is possible that the Fifty Settlements were the basis for the fifty Spacer worlds in the Robot stories.)