The vast eruption of books about energy that has appeared in the past decade has yielded few that could properly be called learning or. alternatively. teaching texts. This one is based principally on ten years of course offerings to senior undergraduates and graduate students at the Massachusetts Institute of Tech- nology. and to middle-level and senior executives who attended accelerated study programs there. Teaching and learning are different; the first is an external act meant to stimulate the second. which is a very internal one. They are surely related. but it does not automatically follow that because I teach. the listener learns. This book. Learning about Energy. attempts to bridge that gap by putting in the hands of teachers. students. and independent readers a broad overview of the energy field. at a level that permits them to enter the more specialized topics with substantial perspective about the whole of it. The material is used for a one-semester course at M.I.T.. but could be one or two semesters there or elsewhere. according to how a thoughtful instructor might abridge some parts. or extend others via the numerous references. the problems at the ends of chapters. and current topics. Learning about Energy deals with energy as more than technology or eco- nomics or any other specific parts. It deals with energy as part of the fabric of civilization. This requires some elaboration. As people and societies need food.