A LOCUS article by Kelly Lagor discusses how accurate the science in science fiction needs to be:Putting the Science in Science Fiction
She distinguishes two aspects of the use of science in stories, "how science plays a role in a story’s message" and "how it is portrayed within the story itself." She quotes numerous SF writers on the issues of factual accuracy of the science in fiction, the author's responsibility to the reader, and how the reader's trust can be won and kept. Elizabeth Bear, for instance, "distinguishes between how different types of stories require different types of accuracy."
Personally, I lean strongly toward the "accuracy required" end of the opinion spectrum. If, as one author quoted mentions, the science in the story is based on present-day facts and theories, it's particularly important not to violate that present-day knowledge, because some readers will certainly notice and object. In a more speculative, futuristic story, the writer has more scope for imaginative variation. And then there are the familiar tropes with no solid basis in contemporary science, such as FTL drives and time travel, which can be accepted as fictional premises for the sake of setting up the background for the plot.
In works that use science fiction tropes for purposes of allegory or satire rather than quasi-realistic extrapolation from real-world facts and theories, I concede that accuracy doesn't hold the highest priority.
The only science fiction I've written consists of stories in the Darkover anthologies. Hard-SF people might not consider Darkover true science fiction because of the unproven status of psychic powers in real life. Although my vampire fiction features naturally evolved, not supernatural, vampires, I don't venture to call it SF because the biology of my vampire species isn't worked out in depth. I include just enough of a biological rationale for their traits to (I hope) suspend the reader's disbelief. So it's more like "science fantasy."
Regardless of faithfulness to current factual knowledge, the writers surveyed in Lagor's article agree that authors must consistently follow the established rules of their fictional worlds. This precept applies to both science fiction and fantasy (not to mention all kinds of "realism" as well). That's one reason I prefer to write fantasy; one can invent one's own rules as long as they make internally consistent sense.
Margaret L. CarterCarter's Crypt