Supersymmetry in the Standard Model allows unification of all fundamental forces apart from gravity at high energy, the M-theory Calabi-Yau manifold rolls 6 dimensions up in such a way that the parity-violating weak force is explained. Witten proved that 10-D strongly coupled superstring theory is equivalent to 11-D weakly coupled supergravity.
‘String theory has the remarkable property of predicting gravity’ -Edward Witten, Physics Today, April 96.
How beautiful... Just don't ask how well the only 'prediction' compared to experiment.
'There is, however, one physical prediction that string theory does make: the value of a quantity called the cosmological constant (a measure of the energy of the vacuum). Recent observations of distant supernovae indicate that this quantity is very small but not zero. A simple argument in string theory indicates that the cosmological constant should be at least around 55 orders of magnitude larger than the observed value. This is perhaps the most incorrect experimental prediction ever made...' - Woit, American Scientist, March-April 2002.