ABSTRACT
State collapse is a very peculiar process, and I will have a lot more to say about it through this book. However, it is not the only way that quantum states can change. For most of the time, the various quantum systems in nature wander about the universe not being involved in experiments, yet clearly things can and do change. Any self-respecting theory must be capable of describing the ordinary business of a world in which things interact with one another, change, and develop. Part of our dealings in this chapter will be to develop the machinery that quantum theory uses to portray the changes of ordinary development and the, rather more mysterious, changes due to measurement.
