Happy birthday to #physicist James Clerk Maxwell (1831-1879)! 🧪🐡🎢🧮 #histsci He dreamt up his demon to deal with the very odd 2nd Law of Thermodynamics (which is not a law like others, & can not be derived from first priciples). It states that 2 bodies of different temperature 🧵1/n
brought together in a closed system will reach thermal equilibrium; or, you cannot use a cold thing to heat a hot thing; or, entropy or disorder can remain constant or grow; or disorder of a closed system cannot decrease.
"... if we conceive of a being whose faculties are so sharpened that 🧵2/n
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, 🧵3/n
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 🧵4/n
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."
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Thus entered into history one of the most colourful and storied of the demons of physics. Though he has served to show that no matter how clever, the 2nd law always survives the Demon, somehow, Maxwell's Demon also survives to test the 2nd Law again in new 🧵6/7
