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From Steam Engines to Life?

What is the state of thermodynamics on the 100th anniversary of the death of Lord Kelvin?

Mark Haw

Escaping Entropic Doom

Kelvin expressed the Second Law at its cruelest with his prediction that the universe was headed for a grim end called universal heat death. Because perfect efficiency is impossible, wasted energy—another way of describing entropy—always increases. The dissipation of useful energy as heat, taken to its logical conclusion, means that all useful energy in the Universe will eventually be frittered away.

But the Second Law is a law of equilibrium—a law of closed systems. What if the important processes in our Universe were overwhelmingly not at equilibrium, were not the products of isolated, closed systems?

Indeed, this is precisely the case: Equilibrium is extremely rare in the natural world. Take the earth's atmosphere—a system profoundly out of equilibrium. The air we breathe is a potentially unstable mix of oxygen, nitrogen, water vapor and so on, and could quickly disappear in a flash of furious chemistry. Yet it has not done so. This is no chance fluctuation: the presence of life and the continual influx of solar energy maintain this out-of-equilibrium state. By means of non-equilibrium thermodynamics, Earthly matter has formed a complex, yet highly ordered and stable system.

Kelvin's thermodynamics, limited to closed systems at equilibrium, was thus the tip of the iceberg when it comes to energy in the Universe. But scientists and philosophers have spent much time contemplating the rest of the berg in the form of non-equilibrium, open-system thermodynamics. Belgian chemist and Nobel laureate Ilya Prigogine suggested that systems away from equilibrium, and especially those fed with a steady supply of energy, are not bound to the disordered fate implied by the Second Law.

In open systems, entropy is not so much a harbinger of doom as a currency for creativity, because in an open system, local entropy can fall as well as rise. True, any decrease must be paid for by a greater increase somewhere else, but Prigogine and his followers argue that the swap of order here for disorder there reveals the inherent creativity of matter that is far from equilibrium. A continual supply of fresh energy enables order to arise from disorder; the phenomenon of so-called self-organization, which cuts across all scales, ultimately results in a creative universe.

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