When we specify the total number n of atoms, their mass m, their degeneracy factor g, and the total energy E., we do not state the positions and velocities of each individual atom.Since we do not specify the positions and velocities of the atoms, we are unable to distinguish between two different samples of the gas, when the difference consists only in different positions and velocities for the atoms. This picture is clearly illustrated in the case of the ideal gas. Since any one of these different microstructures can actually be realized at any given time, the lack of information corresponds to actual disorder in the hidden degrees of freedom. This lack of information introduces the possibility of a great variety of microscopically distinct structures, which we are, in practice, unable to distinguish from one another. A more precise statement is that entropy measures the lack of information about the actual structure of the system. Our discussion shows how this situation is progressively destroyed by diffusion and collisions that increase the entropy and erase the information.Įntropy is usually described as measuring the amount of disorder in a physical system. The information stored in this system corresponds to a decrease in entropy. The concept and phrase 'negative entropy' was introduced by Erwin Schrdinger in his 1944 popular-science book What is Life 1 Later, Lon Brillouin shortened the phrase to negentropy. Let us consider, for instance, the problems of diffusion and spin distribution. In information theory and statistics, negentropy is used as a measure of distance to normality.
#Brillouin science and information theory how to
The examples discussed in the preceding section are not only interesting from a theoretical point of view, but they also show how to attack a practical problem. These delays are used in all practical applications: it does not take very long for a system of pulses (representing dots and dashes, for instance) to be attenuated and forgotten, when sent along an electric cable, but this short time interval is long enough for transmission even over a long distance, and makes telecommunications possible.Ī system capable of retaining information for some time can be used as a memory device in a computing machine. Science and Information Theory Academy Press: New York, NY, USA, 1962.
![brillouin science and information theory brillouin science and information theory](https://ars.els-cdn.com/content/image/3-s2.0-B9780123838742000035-f03-29-9780123838742.jpg)
But, if classical thermodynamics fails to answer this very important question, we can obtain the answer from a discussion of the molecular or atomic model, with the help of kinetic theory: the rate of attenuation of all sorts of waves, the rate of diffusion, the speed of chemical reactions, etc., can be computed from suitable models, and may vary from small fractions of a second to years or centuries. Keywords: entropy second law thermodynamics Shannon measure of. The second principle does not tell us anything about the time required, and hence we do not know how long the system will remember the information. Low entropy implies an unstable situation that will sooner or later follow its normal evolution toward stability and high entropy. The principal source of negentropy for terrestrial life is the sun, which acquired its low entropy state from the expanding universe followed by the collapse of material particles under the force of gravity.Īcquisition of information about a physical system corresponds to a lower state of entropy for this system. New information can only be obtained at the expense of the negentropy of some other system.
#Brillouin science and information theory free
![brillouin science and information theory brillouin science and information theory](https://royalsocietypublishing.org/cms/asset/6ef4e5fa-ec7a-4af4-8c93-a2ee43a6ae29/rsos181055f01.jpg)
4 octombrie 1969, New York City, New York, SUA) a fost un fizician francez. Ivar Stakgold ] įellow of the American Physical Society ]Ĭours Peccot ] ( 1919)
![brillouin science and information theory brillouin science and information theory](https://cs.ucdavis.edu/sites/g/files/dgvnsk8441/files/styles/sf_title_banner/public/2020-03/image12_0.png)
Universitatea Ludwig Maximilian din MünchenĪcademia Națională de Științe a Statelor Unite ale Americii