"After my two attempts at gently raising the issue of string theory, one afternoon I stepped into Feynman's office to ask him what he really thought."Can we talk a little about string theory?" I asked. … "Don't you think there are aspects of it that seem very promising?""Promising? What does it promise? Does it promise to tell you the mass of the proton? No. What does it promise to tell you?""Well, no one knows how to extract any quantitative predictions yet, but—""You're wrong. It does make a quantitative prediction. Do you know what that is?"I looked at him. My mind was a blank."It requires that we live in ten dimensions. Is it reasonable to have a theory that requires ten dimensions? No. Do we see those dimensions? No. So it rolls them up into tiny balls or cylinders too small to detect. So the only prediction it makes is one that has to be explained away because it doesn't fit with observation.""