Sci-fi uses the images that sf - starting with H.G. Wells - made familiar: space travel, aliens, galactic wars and federations, time machines, et cetera, taking them literally, not caring if they are possible or even plausible. It has no interest in or relation to real science or technology. It's fantasy in space suits. Spectacle. Wizards with lasers. Kids with ray guns. I've written both, but I have to say I respect science fiction enough that I wince when people call it sci-fi.
Ursula K. Le GuinThe fish in the creek said nothing. Fish never do. Few people know what fish think about injustice, or anything else.
Ursula K. Le GuinThere was a wall. It did not look important. It was built of uncut rocks roughly mortared. An adult could look right over it, and even a child could climb it. Where it crossed the roadway, instead of having a gate it degenerated into mere geometry, a line, an idea of boundary. But the idea was real. It was important. For seven generations there had been nothing in the world more important than that wall. Like all walls it was ambiguous, two-faced. What was inside it and what was outside it depended upon which side of it you were on.
Ursula K. Le Guin