An anonymous reader writes: SF author Charlie Stross has put together a short list of what he considers to be shibboleths for implausible science fiction. (If you're unfamiliar with the term, read the Wikipedia entry first.) So, what tops his list? "Asteroidal gravel banging against the hull of a spaceship. Alternatively: spaceships sheltering from detection behind an asteroid, or dodging asteroids, or pretty much anything else involving asteroids that don't look like [a pock-marked potato]." Another big red flag for Stross is when authors fail to appreciate Newton's second law, having their characters undergo impacts or accelerations that would turn them into a thin, reddish paste on their starship's hull. Some interesting examples from commenters include: futuristic yet manually-aimed weapons, technobabble as a plot device, and science officers with Ph.D. levels of expertise in dozens of fields. One of mine: entire races or planets full of people who behave the same, often based on some keyword. What are yours? Stross's focus is on books, but feel free to bring up movies and TV shows as well.