Locations in the Solar System besides the Earth have appeared as settings in fiction since at least classical antiquity, initially as an extension of the established literary form of the imaginary voyage to exotic locations ostensibly on Earth. The motif then largely fell out of use for over a millennium and did not become commonplace again until the 1600s with the Copernican Revolution. For most of literary history the principal extraterrestrial location was the Moon; in the late 1800s, advances in astronomy led to Mars becoming more popular. The discovery of Uranus in 1781 and Neptune in 1846, as well the first asteroids in the early 1800s, had little immediate impact on fiction. The main theme has been visits by humans to the Moon or one of the planets, where they would often find native lifeforms. Alien societies commonly serve as vehicles for satire or utopian fiction. Less frequently, Earth itself has been visited by inhabitants of the other planets, or even subjected to an alien invasion.
History
Ancient depictions Locations in the Solar System besides the Earth have appeared as settings in fiction since at least classical antiquity. The conceit of journeying to other worlds grew out of the established literary form of the imaginary voyage to exotic locations ostensibly on Earth, typified by Homer's Odyssey. The earliest stories visiting outer space visited other parts of the Solar System—in particular, the Moon. Science fiction scholar Adam Roberts writes that for the Ancient Greeks, specifically, the Moon and Sun could be thought of as part of the earthly realm of the sky, rather than the divine realm of the heavens, unlike the stars; Arthur C. Clarke comments that the classical planets visible to the naked eye as point sources of light were thought of as wandering stars, which made visiting them equally unthinkable. Speculation that the Moon might be inhabited appears in the nonfiction writings of Philolaus and Plutarch, among others. As the literary record from this era is very incomplete, there is uncertainty about the earliest interplanetary voyages in fiction; Roberts and science fiction historian Sam Moskowitz both posit that numerous such stories predating the known ones may have been lost to time. The earliest known example is Antonius Diogenes's Of the Wonderful Things Beyond Thule, which includes a journey on foot that reaches the Moon by going northwards. It is a lost literary work of uncertain date—with estimates ranging from the 300s BCE to the 100s CE—known only through a brief summary in Photius's 870 work Bibliotheca. The oldest surviving work of this kind is either of two stories by Lucian of Samosata from 160–180 CE: and True History. In Icaromenippus, the Cynic philosopher Menippus, inspired by the story of Icarus, attaches bird wings to his arms and flies to the Moon to get a better vantage point to resolve the question of the shape of the Earth. True History is a parody of fanciful travellers' tales—in the story, a ship is swept to the Moon by a whirlwind, and the all-male lunar inhabitants are found to be at war with the inhabitants of the Sun over the colonization of the "Morning Star"; science fiction scholar Gary Westfahl considers this reference to Venus the first appearance of any planet in the genre. After Lucian, the interplanetary voyage largely fell out of use for over a millennium—as did, according to Roberts, the genre of science fiction as a whole a few centuries later at the start of the so-called Dark Ages.
Copernican Revolution
Interplanetary voyages came into vogue again with the Copernican Revolution, a gradual process that began with the publication of Nicolaus Copernicus's 1543 scientific work De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres) positing that the planets revolve around the Sun rather than around the Earth and continued until Isaac Newton's work on the laws of motion and gravitation provided the necessary mathematical foundation to fully explain Copernicus's model more than a century later. There were nevertheless some antecedents. In medieval Europe, Dante Alighieri's 1320 poem the Divine Comedy visits the Moon and portrays it as the lowest level of Heaven, while in Ludovico Ariosto's poem Orlando Furioso (first version published in 1516, final version in 1532) the Moon is where items lost on Earth end up and it is visited by Astolfo to retrieve the sanity of the title character; Roberts views these narratives as separate from the science-fictional tradition of voyages into outer space inasmuch as they portray the other worlds as supernatural rather than material realms—in particular, Roberts contrasts them with Giambattista Marino's 1622 epic L'Adone, which, although it retains the then-outdated geocentric model in visiting the Moon, Mercury, and Venus, nevertheless treats them as worlds qualitatively akin to the Earth. Outside of Western literature, the 800s–900s Japanese folktale The Tale of the Bamboo Cutter is about a lunar princess on Earth who eventually returns to the Moon.
The first fictional lunar excursion with a science-based approach was written by Johannes Kepler, an important figure of the Copernican Revolution who provided the key insight that planetary orbits are not circular as had been previously assumed but elliptical and introduced a set of three laws of planetary motion. Kepler's Somnium, sometimes considered the first science fiction novel, was written chiefly to explain and advance the Copernican model. The book describes different populations of intelligent life on the near and far side of the Moon, both with adaptations to the month-long cycle of day and night based on exobiological considerations, and their astronomical perspective: for instance, the inhabitants of the near side are able to determine their location on the lunar surface and the time of day by observing the position of the Earth in the sky and the phase of the Earth, respectively. The first draft was written in 1593, before being revised in 1609 and then expanded until Kepler's death in 1630, ultimately being published posthumously in 1634; notes that this means that—contrary to the perceptions of some scholars—the story narrowly predates the invention of the telescope. Also in 1634, the first English-language translation of Lucian's True History by was published; Moskowitz credits this with launching the literary trend of interplanetary voyages, while Westfahl more modestly speculates that writers of such stories may have drawn inspiration from it, and Brian Aldiss, in the 1986 book Trillion Year Spree: The History of Science Fiction, comments that Lucian undoubtedly influenced later writers but ultimately concludes that the more general trends of the Age of Exploration were largely responsible for the profusion of fictional voyages to the Moon.
As no plausible method of space travel had yet been conceived, these stories employed supernatural or otherwise intentionally unrealistic means of transport, or had the characters visit the remote locations in dreams. Kepler's Somnium, although it depicts the conditions on the Moon in accordance with the most up-to-date science available at the time, nevertheless employs a daemon to make the voyage there. Francis Godwin's posthumously published 1638 novel The Man in the Moone uses migratory birds to reach the Moon, where a utopia is discovered. Godwin's book was both popular and influential, and inspired John Wilkins to add discussion of the practical considerations of travelling to the Moon to the third edition of his 1638 speculative nonfiction work The Discovery of a World in the Moone, published in 1640; Wilkins's work also contains an early reference to colonization of the Moon, treating it as a natural corollary to solving the transport issue. Cyrano de Bergerac's posthumously published 1657 novel Comical History of the States and Empires of the Moon and its 1662 sequel depict journeys to the Moon and Sun—both of which are found to be inhabited, with the protagonist of Godwin's novel being encountered on the Moon—using various devices, including the first fictional rocket.
The plurality of worlds
In the late 1500s and early 1600s, the idea of the plurality of worlds—that other celestial bodies in the Solar System, and maybe also outside of it, are worlds like the Earth and perhaps even inhabited—was controversial especially in the Catholic parts of Europe because it appeared to conflict with established religious views that asserted the primacy of Earth and humanity; Giordano Bruno was convicted of heresy and executed in 1600 in part for this belief. By the mid-1600s, however, the controversy had subsided to a degree and the topic appeared in the writings of Cyrano and others; by the end of the century, it was largely accepted. Two works played an important role in popularizing the concept: Bernard Le Bovier de Fontenelle's 1686 work Entretiens sur la pluralité des mondes (Conversations on the Plurality of Worlds) and Christiaan Huygens's posthumously published 1698 work Cosmotheoros. Both are primarily literary rather than scientific works; Guthke takes the apparent broad appeal of Cosmotheoros as evidence that contemporary readers viewed it mainly as science fiction. There are many similarities between the two works, but they differ in their conception of the inhabitants of the other planets: Fontenelle describes diverse and fundamentally nonhuman lifeforms adapted to the different environmental conditions of the Moon and planets in the Solar System, while Huygens describes beings that are essentially human on the grounds that Earth ought not be unique in this regard. Besides depicting a plurality of worlds in the Solar System, Fontenelle's work also popularized the related notion that other stars might have planetary systems of their own just like the Sun; while it dismisses the Sun and stars as possible abodes of life, it asserts that there are unseen planets orbiting the fixed stars that are also inhabited.
Through the 1700s Fiction literature about the Solar System continued to mainly take the form of satires and utopian fiction up until the late 1800s; Roger Lancelyn Green writes that the scientific advancements of the time may help explain the dominance of the satirical mode throughout the latter part of the 1600s and the 1700s, while J. O. Bailey writes that the satire "deepened and became more philosophical" in this period, whereas Kepler's approach of adhering to known facts of science was only emulated sporadically. Westfahl comments that up through the 1700s, authors "invariably imagined that other planets would have humanlike inhabitants" and used extraterrestrial locations for social commentary, as opposed to conceiving of truly alien societies as became common later in the history of science fiction. Early feminist science fiction writer Margaret Cavendish's 1666 novel The Blazing World—which describes another planet that is joined to the Earth at the North Pole—contains both utopian elements and satire of the Royal Society, the scientific establishment of the day. Gabriel Daniel's 1690 novel A Voyage to the World of Cartesius uses a voyage to the Moon and beyond to satirize the ideas of René Descartes, showing them to produce absurd results (such as the stars being invisible and tides not existing) and depicting Descartes's spirit as occupied with correcting God's errors. Trips to the Moon serve as vehicles for satire of the British political system in Daniel Defoe's 1705 novel The Consolidator and the South Sea Bubble in Samuel Brunt's 1727 novel A Voyage to Cacklogallinia. Among the rare exceptions to the trend are 's 1744 story "Die Geschwinde Reise", which describes a journey to a moon of Mars the author mistakenly believed he had discovered, and 's 1750 novel Relation du Monde de Mercure, the first novel focused specifically on Mercury.