In fantasy and science fiction anything is possible but not always plausible. Let's face it, there aren't too many science fiction novels out there that are 100% plausible. But sticking to the plausible makes for duller reading in a way. The reality about space is that it's well...VAST...and largely empty. Doesn't always make for exciting prose.
So, we've already bent the rules for the sake of entertainment. So what? That's what fiction is supposed to do: entertain! There's a place for entirely plausible SF. In fact, there's even a new genre for it. It's called Mundane SF.
But getting back to the rest of the SF universe, say you meet an alien. Say you're out there in space cut off from most other humans. And the alien is not all THAT alien. Would or could a human be attracted to one? Let's say it's mostly humanoid in appearance. Could we look past the appearance and the taboo? Could we be drawn to his or her personality and mind? Or would we actually find the physical otherness compelling? Or would it just be the attraction to something forbidden?
These are the questions that I'm toying with as I work on rewrites of Under the Suns of Sarshan. Who can guess how we'll react to a situation mankind has never encountered? I can only draw comparisons with Earthly "aliens", people who are very different from us in appearance and manner. Then it's a matter of pulling off that crossing of the line in a convincing way.
Comments welcome. After all, I'm writing for the reader.