In thermodynamics, quality is term employed occasionally to describe the relation between the first law and second law in regards to how energy can exist in different forms: "high-grade quality" forms, namly that which can be transformed into mechanical work or electrical work, or "low-grade quality" forms, an example being heat; whereby, in this classification view, the second law or entropy increase is described as a decrease in “quality” of the total energy stored in a given system. [1]

The “quality” description of energy seems to have entered the field predominately with the publication of Leon Brillouin’s 1949 article “Life, Thermodynamics, and Cybernetics” wherein he defines "quality" to a significant degree and uses it in argument. [1]

In 1992, English physical chemist Peter Atkins, in his Creation Revisited, employs the “quality” view of energy mixed in with a "energy dispersal" view of the second law; a term which he says he borrowed from Freeman Dyson in his 1971 article “Energy in the Universe”, who supposedly introduces an “order of merit” for various forms of energy, with gravitational energy heading the list in possession of the highest quality, and cosmic microwave radiation at the bottom, with the lowest quality (in the sense that it corresponds to the ultimate heat sink, in the sense that there is no way in which this variety of energy can be further degraded). [2] Atkins defines “localized energy as energy with potency to be harnessed to do work, and therefore in some sense having ‘high quality’. In employing this term to outline his theory of existence, he states: [3]

“Everything is driven by decay. Everything is driven by motiveless, purposeless decay. By [the term] ‘quality’, [we mean] the extent of its dispersal. High quality, useful energy is localized energy. Low quality, wasted energy, is chaotically diffuse energy. Things can get done when energy is localized; but energy loses its potency to motivate change when it has become dispersed. The degradation of quality is chaotic dispersal. Such dispersal is ultimately natural, motiveless, and purposeless. It occurs naturally and spontaneously, and when it occurs it causes change. When it is precipitate it destroys. When it is geared through chains of events it can produce civilizations.”

1. Brillouin, Leon. (1949). “Life, Thermodynamics, and Cybernetics”, American Scientist, Vol. 37, pgs. 554-68; In: Biology and Computation: a Physicist’s Choice (pgs. 37-51), by H. Gutfreudn and G. Toulouse. World Scientific, 1994; In: Maxwell’s Demon 2: Entropy, Classical and Quantum Information, Computing (pgs. 73-87), Harvey S. Leff, Andrew F. Rex. CRC Press, 2003.
2. Dyson, Freeman. (1971). “Energy in the Universe”, Scientific American, 225(3): 50-59.
3. Atkins, Peter. (1992). Creation Revisited (pgs. 20-21). W.H. Freeman & Co.

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