[SoylentOrange]

Every good fiction writer knows (or *should*) that the only thing that ever keeps fantasy believeable- from Star Wars to Lord of the Rings- is the characters. We have no idea what a hyperdrive or a ringwraith is, but we know people, and we know how people act. We can buy that the millenium falcon can go faster than light because Han Solo smacks Luke Skywalker's hands away from the controls like any knowledgeable person would to a naieve tagalong poking around anything else expensive and dear to us.

Readers insinuate themselves into your characters, all of them, to some degree. They believe the situation and setting, no matter how outlandish, because the characters believe in it, even if it's just enough belief to disbelieve it, and so by believing in the character they believe in their beliefs. When they can't believe the characters, they can't believe in their beliefs, and thus the whole scenario crumbles.