Maxwellscher Dämon
Gedankenexperiment
Basiswissen
Ein kleines Wesen kann gleichförmig warmes Gas ohne Arbeitsaufwand in heiß und kalt entmischen. Das sollte aus theoretischen Gründen unmöglich sein. Der Dämon wirft die Frage auf, was an ihm falsch sein kann.
Wie lautet das englische Originalzitat?
"... if we conceive of a being whose faculties are so sharpened that he can follow every molecule in its course, such a being, whose attributes are as essentially finite as our own, would be able to do what is impossible to us. For we have seen that molecules in a vessel full of air at uniform temperature are moving with velocities by no means uniform, though the mean velocity of any great number of them, arbitrarily selected, is almost exactly uniform. Now let us suppose that such a vessel is divided into two portions, A and B, by a division in which there is a small hole, and that a being, who can see the individual molecules, opens and closes this hole, so as to allow only the swifter molecules to pass from A to B, and only the slower molecules to pass from B to A. He will thus, without expenditure of work, raise the temperature of B and lower that of A, in contradiction to the second law of thermodynamics."
Wo findet man Maxwells ursprüngliche Formulierungen?
The thought experiment first appeared in a letter Maxwell wrote to Peter Guthrie Tait on 11 December 1867. It appeared again in a letter to John William Strutt in 1871, before it was presented to the public in Maxwell's 1872 book on thermodynamics titled Theory of Heat.
Fußnoten
- [1] Balfour Stewart and Peter Tait: The Unseen Universe. Or Physical Speculations on a Future State. Macmillan and Company. London. 1875. Seite 89 ff.
