2019_wiener_Cybernetics - Énergies, Temps & Cosmotechniques

Cybernetics: Or Control and Communication in the animal and the machine === > [!tldr] Tags > #Cybernetics #Control theory #System theory #type/book > [!info] Meta Data >**FirstAuthor**:: [[Wiener, Norbert]] > **Title**:: Cybernetics: Or Control and Communication in the animal and the machine > **Year**:: 2019 > **Citekey**:: [[2019_wiener]] > **itemType**:: book > **Publisher**:: The MIT Press > **Location**:: Cambridge, Massachusetts > **ISBN**:: 978-0-262-53784-1 > **ISSN**:: > > [!Cite] > Wiener Norbert, _Cybernetics: Or Control and Communication in the animal and the machine_, Second edition, 2019 reissue., Cambridge, Massachusetts, The MIT Press, 2019, 303 p. > > %%[@2019_wiener]%% > **URL**:: . > > **Related**:: . > > **Attachment**::[PDF](zotero://open-pdf/library/items/U2SH84KB). --- > [!important] Synthesis > **Contribution**:: > > [!Abstract] > > "Cybernetics is the interdisciplinary study of controlling the flow of information in systems with feedback loops, be they biological, mechanical, cognitive, or social. This book is widely cited for laying the theoretical foundations of information theory and influencing the development of error-correcting servomechanisms, autonomous navigation, analog computing, artificial intelligence, and neuroscience"-- >> --- # Note "Reissue of the 1961 second edition.". --- # Annotations%% begin annotations %% ### Imported: 2026-09-24 10:47 am Quote > His views are captured in the introduction to the second edition of Cybernetics Quote > In doing this, we have made of communication engineering design a statistical science, a branch of statistical mechanics. ... The notion of the amount of information attaches itself very naturally to a classical notion in statistical mechanics: that of entropy. Just as the amount of information in a system is a measure of its degree of organization, so the entropy of a system is a measure of its degree of disorganization; and the one is simply the negative of the other.8 Quote > A very important idea in statistical mechanics is that of the Maxwell demon. ... We shall actually find that Maxwell demons in the strictest sense cannot exist in a system in equilibrium, but if we accept this from the beginning, and so not try to demonstrate it, we shall miss an admirable opportunity to learn something about entropy and about possible physical, chemical, and biological systems. Quote > For a Maxwell demon to act, it must receive information from approaching particles concerning their velocity and point of impact on the wall Quote > the law of the increase of entropy applies to a completely isolated system but does not apply to a non-isolated part of such a system Quote > Accordingly, the only entropy which concerns us is that of the sys-tem gas-demon, and not that of the gas alone. The gas entropy is merely one term in the total entropy of the larger system Quote > The demon can only act on information received, and this information, as we shall see in the next chapter, represents a negative entropy.18 Quote > The notion of the amount of information attaches itself very naturally to a classical notion in statistical mechanics: that of entropy. Just as the amount of information in a system is a measure of its degree of organization, so the entropy of a system is a measure of its degree of disorganization; and the one is simply the negative of the other Quote > the com-plete collection of data for the present and the past is not sufficient to predict the future more than statistically. Quote > This transition from a Newtonian, reversible time to a Gibbsian, irreversible time has had its philosophical echoes. Bergson emphasized the difference between the reversible time of physics, in which nothing new happens, and the irreversible time of evolution and biology, in which there is always something new. Quote > Heat has been converted into usable energy of rotation and translation, and the physics of Newton has been supplemented by that of Rumford, Carnot, and Joule. Thermodynamics makes its appearance, a science in which time is eminently irreversible Quote > One of the cardinal notions of statistical mechanics, which also receives an application in the classical thermodynamics, is that of entropy. Quote > In the ordinary thermodynamic problems of the heat engine, we are dealing with conditions in which we have a rough thermal equilibrium in large regions like an engine cylinder Quote > We may still talk of local temperatures, with a very fair approximation, even though no temperature is precisely determined except in a state of equilibrium and by methods involving this equilibrium Quote > For a Maxwell demon to act, it must receive information from approaching particles concerning their velocity and point of impact on the wall. Whether these impulses involve a transfer of energy or not, they must involve a coupling of the demon and the gas. Now, the law of the increase of entropy applies to a completely isolated system but does not apply to a non-isolated part of such a system. Accordingly, the only entropy which concerns us is that of the system gas-demon, and not that of the gas Quote > alone. The gas entropy is merely one term in the total entropy of the larger system. Quote > The demon can only act on informa-tion received, and this information, as we shall see in the next chapter, represents a negative entropy. Quote > Thus all coupling is strictly a coupling involving energy, and a system in statistical equilibrium is in equilibrium both in matters concerning entropy and those con-cerning energy. In the long run, the Maxwell demon is itself sub-ject to a random motion corresponding to the temperature of its environment, and, as Leibniz says of some of his monads, it receives a large number of small impressions, until it falls into “a certain vertigo” and is incapable of clear perceptions. In fact, it ceases to act as a Maxwell demon. Quote > It will be seen that the processes which lose information are, as we should expect, closely analogous to the processes which gain entropy. Quote > No operation on a message can gain infor-mation on the average. Here we have a precise application of the second law of thermodynamics in communication engineering. Conversely, the greater specification of an ambiguous situation, on the average, will, as we have seen, generally gain information and never lose it. Quote > The statistical theories we have here developed involve a full knowledge of the pasts of the time series we observe Quote > the Newtonian physics, the sequence of physical phenomena is completely determined by its past and in particular by the deter-mination of all positions and momenta at any one moment. Quote > In the complete Gibbsian theory, it is still true that with a perfect determination of the multiple time series of the whole uni-verse the knowledge of all positions and momenta at any one moment would determine the entire future. Quote > The great contribution of Heisenberg to physics was the replacement of this still quasi-Newtonian world of Gibbs by one in which the time series can in no way be reduced to an assembly of determinate threads of development in time. Quote > In quantum mechanics, the whole past of an individual system does not determine the future of that system in any absolute way but merely the distribution of possible futures of the system Quote > In general, there is no set of observations conceivable which can give us enough information about the past of a system to give us complete information as to its future. Quote > Nevertheless, as in the case of all ensembles of time series, the theory of the amount of information which we have here developed is applicable, and consequently the theory of entropy. Since, however, we now are dealing with time series with the mixing property, even when our data are as complete as they can be, we find that our system has no absolute potential bar-riers, and that in the course of time any state of the system can and will transform itself into any other state. Quote > A very important function of the nervous system, and, as we have said, a function equally in demand for computing machines, is that of memory, the ability to preserve the results of past operations for use in the future. Quote > The first condi-tion tends to rule out delays produced by the transmission of light, or even, in many cases, by electric circuits, while it favors the use of one form or another of elastic vibrations; and such vibrations have actually been employed for this purpose in com-puting machines. If electric circuits are used for delay purposes, the delay produced at every stage is relatively short; or, as in all pieces of linear apparatus, the deformation of the message is cumulative and very soon becomes intolerable. Quote > In the electrical industry, pieces of apparatus for this purpose have long been known and have been used in connection with telegraph circuits. They are known as telegraph-type repeaters. %% end annotations %% %% Import Date: 2026-09-24T10:47:06.831+02:00 %%