thermodynamics

Study of the laws governing the transformation of heat energy to and from other forms of energy, thus of the efficient design and working of heat engines (such as the gas engine and the steam engine). Its 3+1 laws are as follows: (1) First law: No form of energy can be created or destroyed but may be transformed from one to another. Therefore the total energy in the universe remains the same. (2) Second law: It is impossible for heat to travel from an object at a lower temperature to another object at a higher temperature. Stated by the German physicist Rudolf Clausius (1822-1888) in two parts as, "Heat cannot be transferred from one body to a second body at a higher temperature without producing some effect," and "The entropy of a closed system increases with time." (3) Third law: It is impossible to reduce any system to a level of absolute temperature or 0 Kelvin (-273.15°C or -459.67°F). (0) Zeroth law of thermodynamics (that underlies all the above laws): If two systems are in thermal equilibrium with a third system, all three systems are in thermal equilibrium with one another.