So here we are. Apart from just a few minor technical details, theoretical physics is finished. We have a model that encapsulates everything we wish to know about our physical world. What else do we want?

Well, the Standard Model is nearly, but not quite, perfect. First of all, we could begin to complain about those twenty uncalculable constants. But if this were the only complaint there would probably be little we could do about it. Of course, numerous ideas have been suggested to explain the origin of these numbers, and theories have been put forward that purportedly ‘predict’ their values. The problem with all these theories is that the arguments they give are never compelling. Why should Nature care about some magic formula if without such a formula no real contradictions arise? What we really need is some fundamental new principle, such as the relativity principle, but we do not want to abandon all the other principles that are already known; these, after all, have been so tremendously helpful in discovering the Standard Model! The best place to look for a new principle is where our present theory has other weak spots.

A universal rule in particle physics is that, when particles collide with greater and greater energies, the effects of the collisions are determined by tinier structures in space and time. Suppose we had at our disposal a particle accelerator in which particles can be given 1000 times the energy that can presently be reached.