Lies, Fictions And Yarns.
Sean pointed out another kind of untrue statement, an error. Thus:
But there is also a kind of statement that is intermediate between true and untrue. A scientific theory:
is the best current approximation to the truth;
explains some phenomena;
but is provisional - always subject to revision.
Some sf shows the scientific process:
in James Blish's They Shall Have Stars/Year 2018!, new discoveries are made despite personal conflicts between some scientists;
in Blish's The Quincunx Of Time, messages from the future assume different scientific paradigms;
in Poul Anderson's Starfarers, interstellar explorers encounter quantum intelligences that receive tachyonic messages from their future.
If a novel about a long interstellar expedition is based entirely on current knowledge and theories about remote stellar regions, then it is bound to be inaccurate because such an expedition would gain new knowledge and revise current theories.