If you write in the science fiction genre you are probably going to encounter more dialogue challenges than other genres. Science fiction has a lot of traps and if you aren’t aware of them you run the risk of writing something that comes across as silly.
One of the first things that will affect your dialogue is how far in the future your story is set. If your story is set in the present or the near future, people will likely speak pretty much as they do today. But if it’s set more than ten years in the future or in an alternate universe, you will face some of the same challenges as writing period dialogue.
Basically you will want to avoid modern slang, idiom and cultural references. You need to work from a more generic use of language without becoming too formal and without losing a sense of character.
Some writers create new slang for their future/alternate world. For example, Star Wars (written by George Lucas) abbreviated the word “android” to “Droid,” which emphasized how common robots were in that culture. Aliens (story by James Cameron and David Giler & Walter Hill, screenplay by James Cameron) introduced “stay frosty” as a future version of “be cool.” And the recent incarnation of the TV show Battlestar Galactica (created by Glen A. Larson and Ronald D. Moore) very effectively used the made-up word “frak” to replace a certain swear word that was forbidden on their cable channel.
This technique can help your fictional world feel more real. Remember how in Blade Runner (screenplay by Hampton Fancher and David Peoples), they used both the term “replicant” for the human like robots and the derogatory term “skin job.” That gave us a subtle sense of the way the robots were perceived by society in the imagined future of the movie.
Alien Languages
If your story involves aliens you will have to decide how to deal with their language. B-movie sci-fi has sometimes had humans land on a new planet only to discover all the aliens speaking English. This is a little ridiculous, of course.
If your aliens are invading Earth you can always just say they learned English from TV signals or something in anticipation of the invasion. Avatar (written by James Cameron) took a variation on this approach – when the story starts the humans had already taught the Navi English. The Navi did have their own language – which was occasionally used with subtitles – but this plot device meant most of the movie could take place without requiring the audience to read.
If you’re doing a space opera story with lots of alien races and cultures the easy way out is the “universal translator” technology like they used in Star Trek (created by Gene Roddenberry). On the other hand, embracing the challenge can add realism to your universe. If you take that path you will face the same issues as stories that use foreign languages. The difference is you may have to actually create this foreign language!
Star Wars used this approach and employed a wide range of tools to deal with it. Chewbacca speaks Wookie and we never understand what he’s saying. But Han Solo does and we grasp the meaning of Chewbacca’s howls from Han’s responses (though Chewbacca doesn’t speak English, he understands it). In the scene with Han Solo and Greedo or with Jabba the Hut in the sequels the filmmakers use subtitles. And they also include C-3PO as a robot who can translate thousands of languages. In Return of the Jedi (story by George Lucas, screenplay by Lawrence Kasdan and George Lucas) the characters (and the audience) simply don’t understand the Ewoks until C-3PO is available to translate. The result is a more linguistically believable fantasy universe.
Exposition
Probably the biggest challenge in most sci-fi is the technical exposition. Science fiction by definition deals with future technology that you’ll have to explain to the audience. How you deal with this depends a lot on whether you’re using a science fiction world as a backdrop for another type of story or whether technology is actually a critical part of your theme.
Star Wars is really an adventure movie set in the future while Alien (story by Dan O’Bannon and Ronald Shusett, screenplay by Dan O’Bannon) is a horror movie set in space. In these kinds of movies you want to spend as little time as possible talking about the technology. In fact, when Lucas started explaining the force and light sabers and so on in the second trilogy it got a little painful. In the first movies they just existed and we accepted it.
However, you do still need to make sure the rules of the technology are clear. Otherwise, the audience will feel like anything is possible and that will kill a lot of the tension in your story.
Star Trek has teleportation technology. Little time is spent on the science behind it, but the rules are clearly established. People generally have to be fairly still and have a communicator for the operator to lock onto. The range of the teleporter is roughly the distance from a planet’s surface to a space ship. They can’t teleport someone between solar systems. The writers can then use these rules to create dramatic situations, such as in the most recent movie version where Scotty had to teleport people who were falling.
If your story is more pure sci-fi and deals with the impact of a certain technology on society you may want to spend more time on the ideas behind that technology. Minority Report (screenplay by Scott Frank and Jon Cohen) is a good example. It introduces the technology of precognition to explore themes of fate. This requires a more thorough explanation of the nature of the precognition technology.
The Matrix (written by Andy & Larry Wachowski) is another good example. The themes of the movie relate to reality and perception. The technology of the virtual world is a device to explore those themes. Thus discussions of the agents as virtual representations of computer programs are not just informational but thematic. And perceptual concepts like déjà vu are given a technological twist to add depth to the story.
Regardless of how much exposition you need, it’s key to deliver it in a palatable and dramatic fashion. See my post on exposition for more on this.