Spacetime is expanding, and has been since the big bang. We think of this as happening on the very largest scales, and so it is. But it is happening on the very smallest scales too—spacetime is the ground of existence on all scales, after all. Why, then, aren’t hydrogen atoms (say) getting bigger? Why isn’t the ‘space’ between nucleus and electrons growing at a rate of tens of metres per second? There are several possible answers to this question, and here’s one: the subatomic particles, out of which the material cosmos is constructed, are ‘actually’ the rents and fundamental flaws in spacetime magnified to the materiality by expansion itself.
Ooh, scare-quote overload. Still: a good SFnal, if not a good Physics, idea.