# Entropy

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 Revision as of 18:31, 14 March 2010Goetzkluge (Talk | contribs) (→References - publication date corrected)← Previous diff Revision as of 09:05, 1 June 2012Jahsonic (Talk | contribs) Next diff → Line 1: Line 1: {{Template}} {{Template}} - In 1930, [[Gilbert Newton Lewis]] gave a simple explanation: ''"Gain in '''entropy''' always means loss of information, and nothing more."'' + In 1930, [[Gilbert Newton Lewis]] gave a simple explanation: ''"[[Gain in entropy always means loss of information, and nothing more]]."'' == Thermodynamics and Information == == Thermodynamics and Information ==

## Revision as of 09:05, 1 June 2012

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In 1930, Gilbert Newton Lewis gave a simple explanation: "Gain in entropy always means loss of information, and nothing more."

## Thermodynamics and Information

The term entropy is used in thermodynamics, information theory and mathematics. In classical thermodynamics entropy is a measure of the amount of energy in a physical system which cannot be used to do mechanical work. Here, the dimension for entopy is energy[Joule] devided by temperature[Kelvin].

However, if a measuring system is used where temperature has been replaced by thermal energy, then entropy is a dimensionless factor. In order to compute in such a measuring system the share of a ressource (e.g. energy or information) which is not-available to any determined or determinable operation, the measure of quantity of that ressource (e.g. using the units [Joule] or the pseudo unit [bit]) is multiplied by that factor. "Degree of unavailability" is the translation of "entropy" into plain English.

## Disorder

Explaining entropy using the term "disorder" often leads to confusion, because disorder itself can be understood in too many different ways. Example: If entropy is computed based on the distribution of ressources in a space, high concentration stands for minimum entropy and completely even distribution stands for maximum entropy. Depending on personal views, both stares could be seen as desirable states of high order.

## Significance of Entropy

The availibility (and unavailibility) of energy at certain locations and times is significant to the organisms in the biosphere. Therefore understanding entropy is important to humans. The biosphere is an open system, but this openess is bounded. Thus, the consumption of ressources (e.g. increasing unavailibility of energy and information) within the system can be compensated by export of entropy (e.g. import of availibility of energy and information) only to a limited degree. If the consumption exeeds the limit, among the various effects of increased entropy, "global warming" may be only one possible result. From a viewpoint of humans, the general effect of increasing entropy production beyond the limits of entropy compensation is the decreasing predictability of the processes within the biosphere. Practically this means: The availibility of ressources becomes less secure.

## Redundancy

Redundancy (based on the definition of information definition of redundancy ISO 2382-16) is the gap between the maximum entropy which a system can handle and the entropy which the system actually is experiencing. In the econometrics of welfare economics, the Theil inequality measure is a redundancy, as it expresses the distance between the entropy of a theoretically even ressource distribution and the entropy of a measured ressource dirstribution.