The Information - James Gleick [132]
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Scientists envied the demon’s powers. It became a familiar character in cartoons enlivening physics journals. To be sure, the creature was a fantasy, but the atom itself had seemed fantastic, and the demon had helped tame it. Implacable as the laws of nature now seemed, the demon defied these laws. It was a burglar, picking the lock one molecule at a time. It had “infinitely subtile senses,” wrote Henri Poincaré, and “could turn back the course of the universe.”♦ Was this not just what humans dreamed of doing?
Through their ever better microscopes, scientists of the early twentieth century examined the active, sorting processes of biological membranes. They discovered that living cells act as pumps, filters, and factories. Purposeful processes seemed to operate at tiny scales. Who or what was in control? Life itself seemed an organizing force. “Now we must not introduce demonology into science,” wrote the British biologist James Johnstone in 1914. In physics, he said, individual molecules must remain beyond our control. “These motions and paths are un-co-ordinated—‘helter-skelter’—if we like so to term them. Physics considers only the statistical mean velocities.” That is why the phenomena of physics are irreversible, “so that for the latter science Maxwell’s demons do not exist.” But what of life? What of physiology? The processes of terrestrial life are reversible, he argued. “We must therefore seek for evidence that the organism can control the, otherwise, un-co-ordinated motions of the individual molecules.”♦
Is it not strange that while we see that most of our human effort is that of directing natural agencies and energies into paths which they would not otherwise take, we should yet have failed to think of primitive organisms, or even of the tissue elements in the bodies of the higher organisms, as possessing also the power of directing physico-chemical processes?
When life remained so mysterious, maybe Maxwell’s demon was not just a cartoon.
Then the demon began to haunt Leó Szilárd, a very young Hungarian physicist with a productive imagination who would later conceive the electron microscope and, not incidentally, the nuclear chain reaction. One of his more famous teachers, Albert Einstein, advised him out of avuncular protectiveness to take a paying job with the patent office, but Szilárd ignored the advice. He was thinking in the 1920s about how thermodynamics should deal with incessant molecular fluctuations. By definition, fluctuations ran counter to averages, like fish swimming momentarily upstream, and people naturally wondered: what if you could harness them? This irresistible idea led to a version of the perpetual motion machine, perpetuum mobile, holy grail of cranks and hucksters. It was another way of saying, “All that heat—why can’t we use it?”
It was also another of the paradoxes engendered by Maxwell’s demon. In a closed system, a demon who could catch the fast molecules and let the slow molecules pass would have a source of useful energy, continually refreshed. Or, if not the chimerical imp, what about some other “intelligent being”? An experimental physicist, perhaps? A perpetual motion machine should be possible, declared Szilárd, “if we view the experimenting man as a sort of deus ex machina, one who is continuously informed of the existing state of nature.”♦ For his version of the thought experiment, Szilárd made clear that he did not wish to invoke a living demon, with, say, a brain—biology brought troubles of its own. “The very existence of a nervous system,” he noted, “is dependent