Most of Asimov's stories are not hard SF and he frequently plays very loose with science when it suits his story (or occassionally a point he is trying to make through the story.)
This is clearer in the Foundation Series than it is in his Robot books, but it becomes blatantly obvious in The End of Eternity which only barely pays lip service to science, yet makes beautiful points about human nature in a painstakingly crafted and entertaining story.
My position on SF is close to how Philip K Dick put it: in SF the main characters aren't people, they're ideas. SF that purports to be scientifically rigorous in some way, or in some way predicting the future, seems to me to be missing the point. Science fiction is about today; it is about the world right now. SF is interesting in so far as it makes you consider the current condition in a different way. In so far as it is scientifically accurate, then it is speculative prediction, not science fiction.
I remember what some italian? guy wrote in the prologue of the Spanish edition of Lem's Star Diaries: that some kind of science fiction, like what Swift or Lem wrote, is about the present, not the future, a critic of our current society, disguised as a futuristic tale.
Considering how much he knew about science (he wrote tons of non fiction science books) if there are scientific inaccuracies in his stories it was by deliberate choice to further the story, and not out of ignorance.
This is clearer in the Foundation Series than it is in his Robot books, but it becomes blatantly obvious in The End of Eternity which only barely pays lip service to science, yet makes beautiful points about human nature in a painstakingly crafted and entertaining story.