Energy in the Universe

O ne need not be a poet or a mystic to find Blake's definition of energy more satisfying than the defini­ tions given in textbooks on physics. Even within the framework of physical science energy has a transcendent quality. On many occasions when revolutions in thou'ght have demolished old sciences and created new ones, the concept of energy has proved to be more valid and durable than the definitions in which it was embodied. In Newtonian mechanics energy was defined as a property of mov­ ing masses. In the 19th century energy became a unifying principle in the con­ struction of three new sciences: thermo­ dynamics, quantitative chemistry and electromagnetism. In the 20th century energy again appeared in fresh disguise, by Freeman J. Dyson