Does hard sci-fi change over time though? I'm not sure but I would imagine that pocket-sized nuclear reactors for instance were at one time plausible, if the st

Does hard sci-fi change over time though? I'm not sure but I would imagine that pocket-sized nuclear reactors for instance were at one time plausible, if the story was written when that was a case is it hard sci-fi? Or does it cease to be hard sci-fi as our understanding of the universe changes?