Energy and Movement

We use the word “energy” daily to refer to different things. We are told, for instance, that certain food does not provide sufficient energy; we are told about the exploitation of energy resources; or we are warned by the politicians about the energy crises. When we are tired, we have “no energy.” We also hear about alternative sources of energy and the mention, by some religions and pseudosciences, of spiritual energy—and so on. But what is energy? In general, and in the sense used in this book, energy is “the potential to produce change,” the capacity to act, transform, or set in motion. Other accepted meanings that we will use refer to energy as a natural resource and as the technology associated with exploiting and using the resource, both industrially and economically.