Oddly enough, SF on the screen can take more liberties than SF on the page. Mistakes are still annoying, but one reason films and TV shows get away with it is the persuasive power of the visual medium. Sometimes it can make even the most discerning watcher believe, even if only for a moment, that yes, these spaceships bank and whoosh because...well, because they just do. The needs of the medium are different. The creators of Star Trek knew perfectly well that spaceships don't whoosh, but the silent motion on the screen just didn't give the dramatic effect they wanted. (Sometimes it doesn't work, though, and that's when you wind up yelling back at the screen.)

But in written stories, you have to create it all in the mind of your reader. So unless you can present powerfully persuasive reasons why something should seem to violate the laws of nature, you have a much better chance of keeping the reader on your side by a) knowing your science, and b) respecting it. Often, this means doing some research. (See Research section).

This doesn't mean you can't play with ideas or stretch them beyond the bounds of known science. But you should do so knowingly, and have a clear explanation in your own mind for the liberties you're taking. One way or another, you must persuade the reader to go along with you - either because you explain, or through the sheer power of your storytelling.