All science-fiction stories lie on a spectrum somewhere between what they call Soft Sci-fi and Hard Sci-fi. The soft kind basically tells you something, and you just have to believe it. “Light sabers work, hyperspace is real. You’ll just have to take our word for it.” Hard sci-fi is written by people like Isaac Asimov who really know their science. They write detailed explanations of imaginary things that makes them feasible. in fact, so feasible that they sometimes inspire real inventions. The Physics of Why leans heavily towards the soft side, but sometimes sounds like hard science. That’s because I, as the author, know just enough science to BS my way through it.