Making our stories believable

No matter how fantastic our world or the things we want to put in it, we need to make the story we tell believable.  To make readers believe our stories we have to give everything that happens in them a reason for occurring.  Events and tech must have a meaning, not just be thrown in to add local colour.

Writing SF doesn't absolve us from the duty to create realistic characters.  Working out their backstory, their culture, history, beliefs and attitudes helps a lot with this.  And we're faced with the extra challenge of creating believable aliens.  

We're writing fiction for humans, that illuminates the human condition, and that has to modify what we might dream up as an alien.  It's hard to relate to a sentient black cloud, although I have one story where Starspeakers speak directly to the consciousness of the universe.  Some writers think that creating humanoid types of aliens is cheating, but I'm not so sure.  The theory of convergent evolution tells us that the same challenges force the same evolutionary design solutions to arise, so if humanoid shapes are the most efficient form for an apex predator it could turn out that they're common.

Of course, they're likely to have different senses from us.  They might see in a different light range, our hear a different set of frequencies.  Anne McCaffrey did that with her alien Gringg, most of whose speech is experienced by humans as rumbling sub-sonics.

If you want humans and aliens to co-exist, they're going to have to do so on an planet or in a space environment that humans can live in.  And that affects the design of your aliens.  If they breathe the same type of atmosphere as us, that automatically limits them.  CJ Cherryh neatly gets around this problem in the Chanur books by dividing space stations into two halves, for oxy-breathers and methane-breathers.  The alien methane-breathers she created are truly alien.  

We have to ground the future of an SF story in something that we can believe today.  This is much easier in near-future SF, where we can extrapolate the consequences of global warming or food shortages.  What we're after is to show how humans are affected by the tech of the future and alien contact.  Our stories question our achievements, hold us to account for our tech and our actions, and ask who we are and who we're becoming.  And making our stories believable gives them more impact and might just leave your readers feeling they have to do something about the issues you've flagged up in your story.