The law stating that the total amount of energy in any isolated system remains constant, and cannot be created or destroyed, although it may change forms
A principle stating that the total energy of an isolated system remains constant regardless of changes within the system. Principle of physics according to which the energy of interacting bodies or particles in a closed system remains constant, though it may take different forms (e.g., kinetic energy, potential energy, thermal energy, energy in an electric current, or energy stored in an electric field, in a magnetic field, or in chemical bonds [see bonding]). With the advent of relativity physics in 1905, mass was recognized as equivalent to energy. When accounting for a system of high-speed particles whose mass increases as a consequence of their speed, the laws of conservation of energy and conservation of mass become one conservation law. See also Hermann von Helmholtz