Space fold

Faster than light

Some works discuss Einstein's general theory of relativity and challenges that it faces from quantum mechanics, and include concepts of space travel through wormholes or black holes. Many writers, however, gloss over such problems, introducing entirely fictional concepts such as hyperspace (also, subspace, nulspace, overspace, jumpspace, or slipstream) travel using inventions such as hyperdrive, jump drive, warp drive, or space folding. Invention of completely made-up devices enabling space travel has a long tradition — already in the early 20th century, Verne criticized H. G. Wells' The First Men in the Moon (1901) for abandoning realistic science (his spaceship relied on anti-gravitic material called "cavorite"). Of fictitious drives, by the mid-1970s the concept of hyperspace travel was described as having achieved the most popularity, and would subsequently be further popularized — as hyperdrive — through its use in the Star Wars franchise. While the fictitious drives "solved" problems related to physics (the difficulty of faster-than-light travel), some writers introduce new wrinkles — for example, a common trope involves the difficulty of using such drives in close proximity to other objects, in some cases allowing their use only beginning from the outskirts of the planetary systems.