This is something that has been coming up while reading/answering questions, and as I'm fairly new to the site I'm unsure what's acceptable/encouraged. In particular, it tends to come up when addressing questions on topics such as FTL travel, e.g. this one: Interplanetary vs Interstellar travel.

When someone wants to know about FTL specifically, the hard science answer is usually "FTL is impossible", and rightfully so. But SF involving FTL travel is both an enormously popular subgenre and a lot of fun, and it's an area where most people willing to suspend disbelief - so answers often take the angle of providing solutions that are satisfying to readers, or maximally compatible with suspension of disbelief, or most convenient in terms of constructing plotlines, as you'll see the answers to the question I linked.

I've chosen to use FTL as a case study because it comes up a lot, but this applies to more or less any question where some degree of handwaving is necesary to make the story work, and thus answering the question is a matter of deciding what kind of handwave will work best. I want to clarify - is there a risk of blurring the lines into writing/plotting advice? What makes the difference between a discussion of making an idea work in a way that's plausible, versus making it work in a way that's entertaining to read? Or is the latter not so much of a problem, within reason?

Test cases


"Slow [your FTL model] down to days [across interplanetary distances] and it's still a trip that people could make routinely, but it would be painfully slow for interstellar travel. Like if it takes, say, 2 days to get to Mars, that's an average speed of 3.1 million miles per hour. Incredible speed! But at that rate it would take you over 200 years to reach Alpha Centauri." - this excerpt from an answer feels good to me. It's providing a scientific explanation for something the author wants to contrive (how to have a story constrained to a single star system, but where interplanetary travel is still fast enough to be convenient.


(Invented so as not to call anyone out specifically)

I think you should make interplanetary travel take between a few weeks and a few months, as this will give your story an Age of Sail feel, allowing you to tap into those tropes. Long journeys raise the possibility of illnesses on board the ship, adds tension via the threat of malfunction/being stranded, and maybe adds drama if the long time spent out in interplanetary space, coupled with other factors, leads to a mutiny on board.

I feel that satisfying readers and their expectations/preferences is a part of worldbuilding, but maybe not the part this site wants to address? Given that it's the area which begins to overlap with discussion of general writing concerns like pacing, tension, providing meaningful but surmountable challenges for characters, avoiding a feeling of deus ex machina, and so forth.


These sort of questions are perfectly fine, and note that we also support fantastical and magic based questions.

The criteria for all questions, whether science based or not are:

  1. Are they about building a world (or more generally a universe/multiverse/whatever)?
  2. Are they answerable?

There are a lot of details that follow onto that such as the question needs to specify enough detail, be sufficiently constrained, etc. Fundamentally though unless the question has or maybe then we're talking about believability and self-consistency not real-world physics.

The 'Bad?' answer you give isn't even bad really. It would very much depend on the question that you are answering but I can see an answer like that being appropriate for some questions. As you rightly say though we do want to steer clear of plot/pacing/etc advice and we're actually currently discussing just where those lines should be drawn. There's a number of meta posts on the subject at the moment and expect to see more joining them soon.


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