So I just finished reading Brian Greene's The Fabric of the Cosmos. All the parts before the string theory talk on inflationary cosmology were really illuminating (the stuff on Higgs fields was particularly enlightening). Anyway, I'm certainly not an expert on any of this stuff, (do the PF forums mind that? I'm sure the Ph.D's and grad students who actually work on cosmology related questions like in the Fine Structure Constant thread don't enjoy crackpots with no training making threads on their outlandish theories, but is it okay for someone with a strictly qualitative understanding to lurk in these forums and ask occasional questions?) but when I got to the string theory section, it was nice to see some updates on where Greene left off in The Elegant Universe (All the stuff about M-Theory). Anyway, my question is this. I notice a lot of people say that string theory makes no predictions, or that the ones it does make require astronomical (literally) amounts of energy to test. My question is A) Does this matter? We were all cool with accepting the stuff of atoms way before we could see them, so why is string theory necessarily different? B) Aren't there in fact tests that could be done that would give a lot of backing to string theory? In his book Greene mentions that the 3 non-gravitational forces are bound to our 3brane and gravity is free to drift off into the extra dimensions. Shouldn't this be verifiable (since then the gravitational force does not in fact diminish with respect to the distance squared between two bodies, it just appears to do that since we only look at stellar/planetary scales, not on teeny tiny scales where rolled up spatial dimensions matter). Isn't this a test that could be done (difficult, but plausible and not requiring particle accelerators the size of the solar system)? I realize that detecting gravitational waves has been difficult enough as it is, but this sort of a test seems like a "in our lifetime" test, as opposed to the particle accelerators the size of the solar system type of tests. Basically, I was hoping to know what other experts in cosmology thought about string theory (when the only information you have on string theory comes from the guy who wrote several books on it, it seems sensible to seek out other opinions... It's like asking the Toyota salesman if the Camry is the best car around). From a non-technical perspective, it does seem elegant in describing why there are the sub-atomic particles there are and why they have the specific masses they have, just like inflationary cosmology helped to explain why space is so flat and why entropy started so low. It seems like without string theory, there are a ton of "things are this way because that's the way they are" just like before the theory of inflationary cosmology low entropy start conditions were that way just because that's the way they are (sort of anthropic explanations, and who likes them?). Anyway, yea, just curious what people who don't make their livings off writing books on string theory think about string theory and its verifiability and potential implications on cosmology. Thanks!