Although... in my mind, they're not really curled up extra
   dimensions per se. Rather, that there's far more space than we
   can see and measure. Not curled up into strings but expansive,
   in an "outward" trajectory with far more "space" than we can
   imagine. In short, rather than going smaller, I'm thinking
   bigger. MUCH bigger. Maybe string theory encompasses this and
   I've misunderstood it. But it always struck me that they were
   trying to fit more dimensions in smaller spaces whereas I'm
   thinking of expansions into much larger spaces than we can ever
   know are there. Not useful for scientific inquiry I'm sure, but
   it's a fun brain game.