As far as whats out there, there is no- humanly possible way to know for sure, you just have to have faith i guess. that link you had is nice, but check this one out, you'll need about 3 hours to go through it, so pop some popcorn and have a seat:
NOVA | The Elegant Universe | Watch the Program | PBS
Brian Greene is a wonderfull writer, but as he'll point out, when it comes to string theory, it's more philosophical than real science, I highly recomend you think on this