Believing that films were strictly for entertainment, Golden Age film producer Sam Goldywn is reputed to have said, "If you want to send a message, use Western Union." Notwithstanding a handful of so-called social problem films, Hollywood films do tend more toward the innocuous than the politically confrontational. Science fiction films, though, are often notable for their idea-driven narratives; social commentary, although not always profound, is a frequent element of sci-fi. It is not unusual for even low-budget, low-concept science fiction films to "send messages" about human nature or the relationship of humans and machines. Their lessons may be conveyed with all the subtlety of a Western Union telegram, but there is no denying that good science fiction films try harder than other genres to ask "deep" questions: Why are we here? What is our future? Will technology save or destroy us?
Though science fiction films vary widely in their politics and aesthetics, they share some key recurring elements. Stories often center on space travel, encounters with alien life-forms, and time travel. Settings are often futuristic and dystopic. Technology is notably advanced (in many futuristic societies) or absent (in post-apocalyptic societies destroyed by technological forces such as atom bombs). Spectacular sets, costumes, and special effects are common, though by no means de rigueur .
With its frequent focus on alien monsters and fantastic special effects, science fiction overlaps with two other genres, fantasy and horror. Indeed, some movies simultaneously embody both horror and science fiction, such as The Thing (1982), Planet of the Vampires (1965), The Fiend Without a Face (1958), and Alien (1979). It is futile to split hairs debating whether a film is truly science fiction, since so many movies mix elements of SF with horror and fantasy. It makes more sense to consider science fiction (like most genres) as existing on a continuum, where some films are mostly science fiction, and others contain only a few science fiction elements. As a rule of thumb, it is helpful to remember that pure fantasy films, such as The Lord of the Rings: The Fellowship of the Ring (2001), or pure horror films like Dracula (1931) tend to emphasize the power of magic and the supernatural, while pure science fiction films, such as The Andromeda Strain (1971), emphasize both the power of technology and scientific innovation and the power of the rational human mind.
Though science fiction films have a history of criticizing technology, they themselves frequently depend on the most advanced technological innovations. Stanley Kubrick's (1928–1999) 2001: A Space Odyssey (1968), for example, presented a very sophisticated 3-D simulation of outer space and spacecrafts. The film famously opens with apes using bones as tools, thus taking the first step toward evolving into humans. A bone tossed up into the air visually segues into a spinning spacecraft in the year 2001. With its spectacular visual celebration of scientific advancement, the film might initially appear to be pro-technology, but its villain is a murderous computer, HAL. Humankind's greatest technological achievement becomes its undoing, paralleling the earlier technological breakthrough, the bone, which was used by one ape to murder another. Evolution is presented, on some level, as devolution. For many viewers, however, 2001 's spectacular effects blunt its negative presentation of HAL; it is hard to interpret such a technologically sophisticated film as
Arguably, some of the best science fiction critiques of technology are in lower budget films such as Mad Max (1979) and A Boy and His Dog (1975), where wars have desolated the planet. Paralleling Kubrick's apes in their primitive ferocity, survivors are forced to make do with whatever technology they can scrounge up. The Omega Man (1971) is a post-apocalyptic film in which most of humanity has been destroyed by germ warfare. The hero is technologically sophisticated, while his brutal foes use primitive weapons and are explicitly opposed to technological advances. The movie is unique for being both post-apocalyptic and pro-technology. Other post-apocalyptic films, such as On the Beach (1959), deemphasize technological critique in favor of a focus on psychological realism and social analysis. Whether overt or more subtle, most science fiction films include some consideration of the positive or negative implications of technological and scientific achievements.