Planets In Science Fiction are fictional planets that appear in various media, especially those of the science fiction genre, as story-settings or depicted locations.
Before Galileo turned his telescope to the heavens, the planets of the Solar System were not recognized as worlds, or places where a person could potentially set foot; they were visible to observers merely as bright points of light, distinguishable from stars only by their motion.
In the system of Claudius Ptolemy (fl. c. 150), the Alexandrian astronomer whose works were the basis of all European astronomy throughout the Middle Ages and Renaissance, the planets were lights set into a series of transparent spheres turning around the Earth, which was the center of the one and only universe.Dante (1265–1321), in his Paradiso, describes the ascent of his narrator through the spheres of the Moon, the planets from Mercury to Saturn, and thence to the sphere of the fixed stars and the heavens of the angels. Dante implies that the light of the planets is a combination of light imparted by Divine will and the radiance of the blessed souls that inhabit the spheres. These planets are, however, entirely ethereal; they have light but no physical form and no geography.
Ludovico Ariosto, in his epic Orlando Furioso (1513), jestingly sent his hero to a Moon where everything lost on Earth eventually turns up; but it was not until Galileo discovered (1609–1610) that the Moon had surface features, and that the other planets could, at least, be resolved into disks, that the concept that the planets were real physical bodies came to be taken seriously. In 1543, Nicolaus Copernicus had already posited that the planets orbited the Sun as the Earth does; combined, these two concepts led to the thought that the planets might be "worlds" similar to the Earth. Public expression of such concepts could be dangerous, however; Giordano Bruno was martyred in 1600 for, among other things, imagining an infinite number of other worlds, and claiming that "Innumerable suns exist; innumerable Earths revolve about these suns ... Living beings inhabit these worlds" in De l'infinito universo e mondi ("Concerning the Infinite Universe and Worlds", 1584).