[Geezer (OP)]

Self explanatory question I hope.

[LeeE]

Well, while string theory is in agreement with other theories it can't be regarded as invalid, for it is as equally valid as the other theories with which it agrees.

For string theory to supplant those other theories though, it would need to successfully predict something that they don't.

[JP]

Smaller scales require higher energies.  If you exponentially scaled up the LHC, you could get to scales where the effects of the  strings become observable.  Such a test would be completely impractical with current technology, however.

[Soul Surfer]

As I see it superstring theory in all its ramifications coupled together into M theory effectively describes all possible universes with physical laws vaguely similar to ours so the problem is not to prove it generally but to try to identify from which part of the vast range of possibilities our universe originates and why.