... on, but the idea is clear: the universe is the way it is because the matter and the force particles have the properties they do. But is there a scientific explanation for why they have these properties? ... it is only part of the reason string theory has generated such excitement. String Theory as the Unified Theory of Everything In Einstein's day, the strong and the weak forces had not yet ... particles—their number, the strength of the force they convey, the gauge symmetries they respect—though, does depend crucially on the precise geometrical form of the curled-up dimensions. And so,...