Perhaps the foregoing has given you the impression that, in the end, our efforts amount to not much more than continuously discovering new particle types, which are subsequently just added to our model. More or less by accident, we have arrived at a description that, for the time being, fits neatly with all we know at present, and we have dubbed it the ‘Standard Model’. But can one now conclude new things from it, something we could not possibly have known in advance, a prediction of something entirely new? The following story about the ‘anomalies’ could be an answer to this. This chapter is an intermission, a temporary local excursion interrupting our grand journey to the world of the small. We physicists are perfectionists. If our model shows a dirty spot, we want to clean it. History tells us that if we hit upon some obstacle, even if it looks like a pure formality or just a technical complication, it should be carefully scrutinized. Nature might be trying to tell us something, and we should find out what it is.

Some of the mathematical arguments in this chapter are too technical to explain in detail, but most of them can be translated into words. If you agree with many of my friends, and the publisher, that this chapter is unintelligible, skip it. I am going to make an attempt anyway to show to you how shrewd Nature is.