It is estimated that along with the four dimensions we live in; x, y, z, and time, another seven may exist. Although we can not concieve these other dimensions they are mathematically correct and possible.
Hopefully with the help of the LHC, we will be able to prove the string theory. If you haven't done so already, I suggest that you look into Brian Greene's book, "The Elegant Universe." In this book, he exquisitly explains the backbone of the string theory and everything associated with it. It would also be a good idea to go to PBS's website and search for "The Elegant Universe" series they have on their. Brian Greene narates it and is very interesting.
