Dimension in physics

I have a solid understanding of topological dimension. I heard that some string theororists think that the universe is >= 10-dimensional, but that the extra 7+ dimensions are too small for us to encounter. How can a dimension be small; is it just a model for what is observed, or is it based in theory?

>>10
is it any wonder
I thought of going in physics then thought what job would i be able to get with that.

want fries with that?