Protons are probably smaller than long thought
Ignorant outsider to the field here: I've often heard the claim that quantum mechanics has been verified to amazing accuracy, that its predictions match with reality to the maximum degree that our instrumental precision allows, etc. A 5% difference seems big enough that at least some of our experiments should have error limits less  than that. So how is it that this is only now being found, and there's still uncertainty surrounding it?I feel like I'm missing something fundamental here, and I'd like to know what it is.