And six of these small dimensions that we can't see. And the reason we can't see them is that their size has the same characteristic very small length. Certainly, if string theory is going to succeed in the long run as a convincing theory of unifying elementary particles and their forces, we are going to have to be able to perform experimental tests of the theory. Right now we are a little bit frustrated, in that we don't understand the theory well enough that we can make definitive predictions and tell our experimental colleagues that you should go and measure this and that, and if you find this result our theory is right, if you find that result our theory is wrong. We certainly hope that eventually we will be able to make predictions of that kind, but right now we cannot.
Super symmetry relates matter particles to force particles.
So, in the short term we need more modest goals. One reasonable goal, I think, is to try to account for known results within the framework of string theory. But, at the same time we are alert to the possibility that there could be qualitatively new features that would be experimentally observable. We hope that such predictions might emerge, but at the moment we really don't know what it will be. But there are certain dramatic possibilities that experimentalists should be alert for.