It really depends. In the 30s and 40s, many scifi [comic books] were largely based on well defined and plausible rocket theory. Hollywood though... I guess the

It really depends. In the 30s and 40s, many scifi [comic books] were largely based on well defined and plausible rocket theory. Hollywood though... I guess the distinction between scientific hypotheses and scifi that extends beyond well understood science is that you have to have scientifically rigorous reasons to think the hypothesis might be true. So not mere notions, e.g. there is no cold fusion reaction hypothesis anymore.