Ayres, Robert U., an American physicist, is noted for his description of the role of thermodynamics in the economic process; he is a known critic of standard economic growth theory. He is the founder of the fields of ecological economics and industrial ecology. In Resources, Environment, and Economics (1978) he describes the inconsistency of the closed, cyclic model of standard economics with the First Law of Thermodynamics, which states that what low-entropy matter and energy enters the economic process as useful raw materials must ultimately leave the process and return to nature as high entropy wastes. He performed many of the first detailed empirical analyses of mass balances for specific materials in the U.S. economy. He also developed formal theoretical and empirical models of the U.S. economy that explicitly accounted for the role of energy in technological change in the U.S. economy.