SCIOD 5: Supply Creates Its Own Demon

In August of 1807 several of Manchester's most prominent citizens petitioned the British government to grant an award to Edmund Cartwright for his valuable contribution to industry and commerce made by the invention of the power loom and other mechanical devices. Among the petition's signatories was Peter Ewart, an engineer and manufacturer who the following year was to read at the Literary and Philosophical Society of Manchester the historically significant paper, "On the Measure of Moving Force."

Ewart's precocious mechanical aptitude as a young boy is reminiscent of the character, August Eschenburg, in the Millhauser story mentioned earlier. From the age of nine, Ewart haunted the workshops of a watchmaker and a millwright and by the age of twelve had built himself a makeshift clock out of wooden parts. In memoirs of his childhood, he recalled lying awake at night, wondering if his clock was still operating and getting up from time to time to check on it.

In his 1808 paper, Ewart addressed an old controversy about how to estimate the force exerted by bodies in motion. Ewart supported the argument that force equaled the mass of the body multiplied by the square of its velocity; the other side argued that it was mass multiplied simply by velocity. At the time, British mathematicians and natural philosophers adopted the latter position, while engineers, like James Watt, subscribed to the former. Ewart's analysis directly influenced James Joule's concepts of work and vis viva and consequently played an formative role in the scientific debates that established the laws of thermodynamics.

Together with Edmund Cartwright and James Joule, Peter Ewart thus acted as a sort of collective conduit, transmitting an essence of Baron von Kempelen's ersatz chess-playing automaton from one end to James Clerk Maxwell's molecule-sorting demon at the other. Thomas Pynchon would be intrigued. Maxwell conceived of his demon (1867) just around the time Jevons was expounding on his paradox (1865) and Mill was recanting the wages-fund doctrine (1869). It was William Thomson (later Lord Kelvin) who called it a demon, Maxwell simply referred to it as a "being" To illustrate the strictly statistical nature of the second law of thermodynamics, he envisioned a vessel containing air at a uniform temperature, although the individual molecules are not moving at uniform velocities:

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.

It's not as if Maxwell was trying to throw cold water on the second law, though. On the contrary, he described the second law of thermodynamics as having "the same degree of truth as the statement that if you throw a tumblerful of water into the sea, you cannot get the same tumblerful of water out again." Yet a great deal of free energy has been expended in the effort to exorcise Maxwell's demon. Each tumblerful of critique tossed into the ocean of demon exorcism becomes similarly dissipated.

Another embodied link between Maxwell's demon and von Kempelen's automaton surfaces in the form of information theory in the mid-twentieth century. In 1950 Claude Shannon of Bell Laboratories wrote the seminal paper on "Programming a Computer to Play Chess." In it he discussed the previous literature on the subject of chess-playing machines, including a reference to Poe's essay on "Maelzel's Chess Player." The following year, Leon Brillouin of I.B.M. published an article in which he used Shannon's discussion of information theory to show that "Maxwell's Demon Cannot Operate." It has more recently been argued that the impetus for Brillouin's argument – relating information and thermodynamic entropy– arises from a misconception of what Maxwell's intention was in positing the demon thought experiment.