When was the law of conservation of energy introduced?
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In 1850, William Rankine first used the phrase "the law of the conservation of energy" for the principle.
Conservation of energy
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The conservation of energy is a common feature in many physical theories. From a mathematical point of view it is understood as a consequence of Noether's theorem, developed by Emmy Noether in 1915 and first published in 1918. The theorem states every continuous symmetry of a physical theory has an associated conserved quantity; if the theory's symmetry is time invariance then the conserved quantity is called "energy". The energy conservation law is a consequence of the shift symmetry of time; energy conservation is implied by the empirical fact that the laws of physics do not change with time itself. Philosophically this can be stated as "nothing depends on time per se".
In other words, if the physical system is invariant under the continuous symmetry of time translation then its energy (which is canonical conjugate quantity to time) is conserved. Conversely, systems which are not invariant under shifts in time (an example, systems with time dependent potential energy) do not exhibit conservation of energy – unless we consider them to exchange energy with another, external system so that the theory of the enlarged system becomes time invariant again. Conservation of energy for finite systems is valid in such physical theories as special relativity and quantum theory (including QED) in the flat space-time.
Conservation of energy
1419#71
In the eighteenth century, the law of conservation of energy was yet to be fully formulated or established, and the nature of heat was debated. One approach to these problems was to regard heat, measured by calorimetry, as a primary substance that is conserved in quantity. By the middle of the nineteenth century, it was recognized as a form of energy, and the law of conservation of energy was thereby also recognized. The view that eventually established itself, and is currently regarded as right, is that the law of conservation of energy is a primary axiom, and that heat is to be analyzed as consequential. In this light, heat cannot be a component of the total energy of a single body because it is not a state variable, but, rather, is a variable that describes a process of transfer between two bodies. The adiabatic process is important because it is a logical ingredient of this current view.
Adiabatic process
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These developments led to the theory of conservation of energy, formalized largely by William Thomson (Lord Kelvin) as the field of thermodynamics. Thermodynamics aided the rapid development of explanations of chemical processes by Rudolf Clausius, Josiah Willard Gibbs, and Walther Nernst. It also led to a mathematical formulation of the concept of entropy by Clausius and to the introduction of laws of radiant energy by Jožef Stefan. According to Noether's theorem, the conservation of energy is a consequence of the fact that the laws of physics do not change over time. Thus, since 1918, theorists have understood that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time.
Energy
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The earliest constants of motion discovered were momentum and energy, which were proposed in the 17th century by René Descartes and Gottfried Leibniz on the basis of collision experiments, and refined by subsequent researchers. Isaac Newton was the first to enunciate the conservation of momentum in its modern form, and showed that it was a consequence of Newton's third law. According to general relativity, the conservation laws of linear momentum, energy and angular momentum are only exactly true globally when expressed in terms of the sum of the stress–energy tensor (non-gravitational stress–energy) and the Landau–Lifshitz stress–energy–momentum pseudotensor (gravitational stress–energy). The local conservation of non-gravitational linear momentum and energy in a free-falling reference frame is expressed by the vanishing of the covariant divergence of the stress–energy tensor. Another important conserved quantity, discovered in studies of the celestial mechanics of astronomical bodies, is the Laplace–Runge–Lenz vector.
Noether's theorem
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In 1918 it was proved that the law of conservation of energy is the direct mathematical consequence of the translational symmetry of the quantity conjugate to energy, namely time. That is, energy is conserved because the laws of physics do not distinguish between different moments of time (see Noether's theorem).
History of energy
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Following a meeting between McCarthy and Professor Sir Eric Ash in July 2007, Ash reported that "the "Orbo" is a mechanical device which uses powerful magnets on the rim of a rotor and further magnets on an outer shell." During this meeting, McCarthy referred to the law of conservation of energy as scientific dogma. However, conservation of energy is a fundamental principle of physics, more specifically a consequence of the unchanging nature of physical laws with time by Noether's Theorem. Ash said that there was no comparison with religious dogma since there is no flexibility in choosing to accept that energy is always conserved. Rejecting conservation of energy would undermine all science and technology. Ash also formed the opinion that McCarthy was truly convinced in the validity of his invention but that this conviction was a case of "prolonged self-deception."
Steorn
23982079#3
The National Appliance Energy Conservation Act of 1987 amended the Energy Policy and Conservation Act and was introduced and supported by democratic Senator Bennett Johnston, Jr. from Louisiana in January 1987. The new amendments to the act established minimum efficiency standards for many household appliances, including:
National Appliance Energy Conservation Act
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Introduced by Ed Miliband MP, the then-Secretary of State for Energy and Climate Change, the Energy Bill had its first reading on 19 November 2009. On 7 December of the same year, the Bill received its second reading and first debate, during which the Labour Party and the Liberal Democrats agreed on the continuation of the Energy Bill to become law, while facing opposition from the Conservative Party. While Miliband received questions over grid access, gas storage, and the Government's support of the European "super-grid," the Bill was passed to the committee stage.
Energy Act 2010
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Mass and energy can be seen as two names (and two measurement units) for the same underlying, conserved physical quantity. Thus, the laws of conservation of energy and conservation of (total) mass are equivalent and both hold true. Einstein elaborated in a 1946 essay that "the principle of the conservation of mass [...] proved inadequate in the face of the special theory of relativity. It was therefore merged with the energy conservation principle—just as, about 60 years before, the principle of the conservation of mechanical energy had been combined with the principle of the conservation of heat [thermal energy]. We might say that the principle of the conservation of energy, having previously swallowed up that of the conservation of heat, now proceeded to swallow that of the conservation of mass—and holds the field alone."
Mass–energy equivalence
1406138#0
The National Energy Act of 1978 (NEA78) was a legislative response by the U.S. Congress to the 1973 energy crisis. It includes the following statutes:The legislative initiative was introduced by President Carter. The package was a major step in the legislation of the energy field, both the supply and the demand side. The package has soon been followed by Energy Security Act, 8 acts signed by president Carter in 1980. This sequel package addressed energy conservation and development of renewable energy sources.
National Energy Act
67088#14
Engineers such as John Smeaton, Peter Ewart, , Gustave-Adolphe Hirn and Marc Seguin recognized that conservation of momentum alone was not adequate for practical calculation and made use of Leibniz's principle. The principle was also championed by some chemists such as William Hyde Wollaston. Academics such as John Playfair were quick to point out that kinetic energy is clearly not conserved. This is obvious to a modern analysis based on the second law of thermodynamics, but in the 18th and 19th centuries the fate of the lost energy was still unknown.
Conservation of energy