Introduction
Engineering used to be a down-to-earth profession. The Roman engineers, who provided civilized Europe with bridges and roads, did a job comprehensible to all. And this is still true in most branches of engineering today. Bridge-building has become a sophisticated science, the mathematics of optimum structures is formidable; nevertheless, the basic relationships are not far removed from common sense. A heavier load is more likely to cause a bridge to collapse, and the use of steel instead of wood will improve the load-carrying capacity.
Solid-state electronic devices are in a different category. In order to under- stand their behaviour, you need to delve into quantum mechanics. Is quantum mechanics far removed from common sense? Yes, for the time being, it is. We live in a classical world. The phenomena we meet every day are classical phe- nomena. The fine details represented by quantum mechanics are averaged out; we have no first-hand experience of the laws of quantum mechanics; we can only infer the existence of certain relationships from the final outcome. Will it always be this way? Not necessarily. There are quantum phenomena known to exist on a macroscopic scale as, for example, superconductivity, and it is quite likely that certain biological processes will be found to represent macroscopic quantum phenomena. So, a ten-year-old might be able to give a summary of the laws of quantum mechanics-half a century hence.* For the time being there is no easy way to quantum mechanics; no short cuts and no broad highways. We just have to struggle through. I believe it will be worth the effort. It will be your first opportunity to glance behind the scenes, to pierce the surface and find the grandiose logic of a hidden world.