I saw one of those multipart string theory explanations on Utube years ago. I was feeling in the mood to get brainy, so I watched the whole thing, and string theory is an interesting curiosity. So it starts out, and I'm like, "OK this is good. This makes logical sense," and I was looking forward to becoming an expert. But then in part two or three, they fessed up with a let down. The guy said something like, "And this is the part of string theory that even the physicists can't explain." I can't remember what that part was, but without it, in my wee brain anyway, the whole theory of strings falls apart. If I remember right, what I was hoping for was an explanation of how they knew about the existence of vibrating strings. The problem seemed to be that they didn't really, and I ended up feeling gypped.