SF is rife with tropes (say that quickly ten times).
In mainstream lit, a trope is a figure of speech: metaphor, simile, irony, or the like. Words used other than literally. In SF, a trope is more: science used other than literally. I think of an SF trope as a willing-suspension-of-disbelief contract between author and reader.
Tropes. That’s how SF stories get (to name a few) faster-than-light travel, telepathy, and time travel. Author and reader agree -- despite contradiction with prevailing scientific theory and/or the lack of supporting evidence -- to include such an element in a story.
Let’s start with FTL. Clearly many of us want fast interstellar travel in our SF. Consider these media franchises: Star Trek, Star Wars, Stargate, Aliens. In the written form: Brin’s Uplift universe, Niven’s Known Space, and Herbert(s)’s Dune series.
So why FTL? To plot on worlds we might want to colonize. To plot with aliens enough like us (e.g., oxygen breathers) to covet the worlds we will. Astronomy has long eliminated the other worlds of this solar system from consideration.
It wasn’t always so. Once there was Terra Incognita. Homer could confront Odysseus with fabulous creatures somewhere in the Mediterranean. Not that long ago, leading scientists thought Mars was hospitable to life and even saw evidence there of intelligence.
Many SF authors and readers have embraced the trope of FTL travel. Or is it a trope? That is, is FTL a fantasy? That’s the subject of an upcoming post.