Nimble as they were in their ability to take the bull of time
and change by its horns, the matadors of classical and statistical thermodynamics
had to give way to an even more ambitious bullfighter—a general thermodynamics
studying systems not confined to artificial boundaries. The natural growth
of these systems—feeding on the destruction
of gradients—represents a nascent science of "creative destruction.
Because this open-system science, NET, is still early in the flower
of its development, narrating its history is not so easy. Nonetheless,
in this chapter we propose a rough roadmap for a future history, highlighting
such landmarks as the work of Lotka, Onsager, and Prigogine. Like the
systems it discovered, whose organization depended upon energy flow,
the science that studies these systems—NET, and its subdiscipline,
the thermodynamics of life discussed in this book—are in a state
of flux.
Trained as a physical chemist, Alfred Lotka worked for an insurance
company as a statistical analyst and in his spare time was a student
of biology. Almost a generation ahead of his peers, Lotka suggested that
life was a dissipative metastable process. By this he meant that, although
stable and mistaken for a "thing," life was really a process.
Living matter was in continuous flux, kept from equilibrium by energy
provided by the sun. Lotka stressed that life on Earth was an open system.
It was bioenergetic and biophysical, a thermodynamic phenomenon.
Beyond the near-equilibrium Onsager region are "far-from-equilibrium" systems,
named by Ilya Prigogine and coworkers Gregorie Nicolis and P. Glansdorff
at the Free University of Brussels. These systems capture and deploy
energy and spin out intricate material flows; they undergo unpredictable
and sometimes sudden changes in organization; they are, in a word, wild.
Known mainly for his work on elaborate cyclical chemical reactions, Prigogine
popularized the term dissipative structures. These dissipative
systems, a term first used by Lotka, maintain their stable, low-entropy
state by importing material and energy across their system boundaries.
Dissipative systems are nonequilibrium, open, dynamic systems with gradients
across them. They degrade energy and exhibit material and energy cycling.
Dissipative structures grow more complex by exporting—dissipating—entropy
into their surroundings .
The nontrivial laws of thermodynamics
were hard won. The second law was the first to be understood, by Carnot,
who realized the need for a hot/cold differential to power engines, and
recognized the irremediable one-way-ness, the loss inherent in all real
macroscopic energetic processes in the universe. Heat moves into the
cool, not vice versa. The first law, the second to be formally stated,
was presented by Rudolf Clausius and Lord Kelvin as the conservation
law. The third law of thermodynamics evolved out of Lavoisier's and Joseph-Louis
Gay-Lussac's work on the development of pressure, temperature, and volume
experiments. They showed that a pressure of any gas contained in a given
volume increases or decreases by 1/273 of initial value for each degree
Celsius. If one starts with a gas at 0°C as a reference
point, and cools it to <min>273°C or 0 kelvin, the gas pressure
declines to zero and molecular motion is predicted to cease. Later, in
1906 and 1911, respectively, German physicists Walther Nernst and Max Planck
developed this idea into the relationship between thermodynamic entropy
and 0 kelvin. At absolute zero the entropy of the system is zero. The "zeroth" law
of thermodynamics, put forth formally in 1931, deals with the two seminal
concepts, equilibrium and temperature. When a closed thermodynamic system
within rigid heat-proof walls reaches the point of no more change, the
system has reached a state of thermal equilibrium. The zeroth law informs
all the laws of thermodynamics and provides an important underpinning for
a gradient-based thermodynamics. Another important principle for nonequilibrium
thermodynamics, sometimes thought to rise to the status of a fourth law,
but perhaps better understood as a logical consequence of the first and
second laws, is that matter cycles in regions of energy flow; such cycles,
visible in natural complex structures, including those of life, occur as
limited material resources scramble to provide a vehicle for entropy export.
We have synthesized the general principles of open thermodynamic systems
in the appendix. This appendix, although hidden at the end of the book,
bears close study by the truly interested. Many of these principles apply
to living systems.
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