String Theory is lost in a wilderness of mathematical confusion. The things it "explains" may be true, but it is not the case that string theory adds any new understanding. The problem is a combination of the mathematics being too hard and the physics being too high-energy to be experimentally accessible; but the first of these is the more fundamental. There are plenty of things that experiment already measures that a proper fundamental theory ought to explain, namely the 17 or so arbitrary parameters currently necessary to stick in to the "standard model". If Greene, Witten, et al could just derive the fine-structure constant or the quark and lepton mass ratios from string theory using pure mathematics, it would completely justify string theory and they would be the most deserving Nobel Prize winners since Einstein; but they can't, and in fact the later versions of string "theory" are getting further and further away from being able to do this.
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