Standard Model: String Theory

String theory unites the theories for quantum mechanics, relativity and gravity, but doesn't work when confined to the three dimensions that people normally think of.  It would work if there were more dimensions, so some scientists theorize that there are small dimensions.  Humans can't move in or around these smaller dimensions, but smaller particles would be able to move.  Most ideas about String theory predict 10 dimensions, but the Boson theory predicts 26 and the M-theory 11.  These theories also postulate that some of the smaller dimensions could be circular or overlapping.

I think that it might be impossible for people to see these dimensions or be able to move in them, but the effects of them might be visible on particles that move around these dimensions.  Just like gluons, the force-carrier particle of strong nuclear force, have only been observed indirectly, potentially the dimensions of string theory could been seen indirectly.  Some physicists think that at high enough energies the different 'strings' could be seen, however the energies required are around 10^4 higher than energy in the Large Hadron Collider.  Another idea to test the small dimensions is by using gravity, it is theorized that gravity is stronger in smaller dimensions and that mini black holes could be formed.  I think that on a smaller enough scale and with enough energy it would be possible to prove string theory, but just like how it took a long time to prove the existence of quarks, it will take awhile for the technology to catch up to the theories.