Brian Greene has a nice and wise
IHT). It starts with Einstein's attempts to find the unified field theory and explains why he couldn't succeed since he didn't know the nuclear forces and deliberately decided to ignore quantum mechanics.
Greene returns to the beginnings of physics and Newton's unification of celestial and terrestrial gravity, electromagnetism, quantum mechanics. It is then explained how Glashow, Salam, and Weinberg made the next important steps to unify the forces. The previous attempts couldn't unify all forces and remove the singularities, string theory can.
A brief history of string theory is followed by many examples of existing or conceivable experimental setups to verify various scenarios or calculations of string theory, including the LHC, mini-black-holes, RHIC, corrections to CMB, and others.
Brian emphasizes that string theory doesn't change anything whatsoever about the scientific method, in a sharp contrast with a rather widely held myth. Although one needs a lot of mathematics, the goals and the criteria to decide about the theory's validity are what they always have been and the experimental verification is the only final arbiter. Brian Greene as well as every other string theorist would stop working on the theory if it were shown that it is internally inconsistent or incompatible with reality - which however hasn't happened.
He points out that even if it is impossible to determine the parameters of Nature uniquely, a unified theory would still be a huge achievement. He also addresses certain comments that a research direction should be given up if it doesn't satisfy an arbitrary timetable. Greene determines that this suggestion is, well, silly.
String theory continues to offer profound breadth and enormous potential. It has the capacity to complete the Einsteinian revolution and answer the deepest questions. Do we know for sure that we will reach the end? We don't know but science requires tolerating uncertainty.
And that's Brian's memo. ;-)
Thanks to David G.