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Emergent Complexity, Teleology, and the Arrow of Time
Paul Davies
1.
the dying universe
In 1854, in one of the bleakest pronouncements in the history of science,
the German physicist Hermann von Helmholtz claimed that the universe
must be dying. He based his prediction on the Second Law of Thermody-
namics, according to which there is a natural tendency for order to give
way to chaos. It is not hard to find examples in the world about us: peo-
ple grow old, snowmen melt, houses fall down, cars rust, and stars burn
out. Although islands of order may appear in restricted regions (e.g., the
birth of a baby, crystals emerging from a solute), the disorder of the envi-
ronment will always increase by an amount sufficient to compensate. This
one-way slide into disorder is measured by a quantity called entropy. A state
of maximum disorder corresponds to thermodynamic equilibrium, from
which no change or escape is possible (except in the sense of rare statisti-
cal fluctuations). Helmholtz reasoned that the quantity of entropy in the
universe as a whole remorselessly rises, presaging an end state in the far
future characterized by universal equilibrium, following which nothing of
interest will happen. This state was soon dubbed the “heat death of the
universe.”
Almost from the outset, the prediction of cosmic heat death after an ex-
tended period of slow decay and degeneration was subjected to theological
interpretation. The most famous commentary was given by the philosopher
Bertrand Russell in his book Why I Am Not a Christian, in the following terms:
1
All the labors of the ages, all the devotion, all the inspiration, all the noonday bright-
ness of human genius are destined to extinction in the vast death of the solar system,

occasioned by this irreversible heat flow, since much life on Earth is sustained
by the temperature gradient produced by sunshine. Microbes that live under
the ground or on the sea bed utilize thermal and chemical gradients from
the Earth’s crust. These too are destined to diminish over time, as thermal
and chemical gradients equilibrate. Other sources of energy might provide
a basis for life, but according to the Second Law, the supply of free energy
continually diminishes until, eventually, it is all exhausted. Thus the death
of the universe implies the death of all life, sentient and otherwise. It is
probably this gloomy prognosis that led Steven Weinberg to pen the famous
phrase, “The more the universe seems comprehensible, the more it also
seems pointless.”
3
The fundamental basis for the Second Law is the inexorable logic of
chance. To illustrate the principle involved, consider the simple example
of a hot body in contact with a cold body. The heat energy of a material
substance is due to the random agitation of its molecules. The molecules
of the hot body move on average faster than those of the cold body. When
the two bodies are in contact, the fast-moving molecules communicate some
of their energy to the adjacent slow-moving molecules, speeding them up.
After a while, the higher energy of agitation of the hot body spreads across
into the cold body, heating it up. In the end, this flow of heat brings the two
bodies to a uniform temperature, and the average energy of agitation is the
same throughout. The flow of heat from hot to cold arises entirely because
chaotic molecular motions cause the energy to diffuse democratically among
all the participating particles. The initial state, with the energy distributed
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in a lopsided way between the two bodies, is relatively more ordered than

Reaction to the theme of the dying universe began to set in the nine-
teenth century. Philosophers such as Henri Bergson
4
and theologians such
as Teilhard de Chardin
5
sought ways to evade or even refute the Second
Law of Thermodynamics. They cited evidence that the universe was in some
sense getting better and better rather than worse and worse. In Teilhard de
Chardin’s rather mystical vision, the cosmic destiny lay not in an inglorious
heat death but in an enigmatic “Omega Point” of perfection. The progressive
school of philosophy saw the universe as unfolding to ever greater richness
and potential. Soon after, the philosopher Alfred North Whitehead
6
(curi-
ously, the coauthor with Bertrand Russell of Principia Mathematica) founded
the school of process theology on the notion that God and the universe are
evolving together in a progressive rather than a degenerative manner.
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Paul Davies
Much of this reaction to the Second Law had an element of wishful think-
ing. Many philosophers quite simply hoped and expected the law to be
wrong. If the universe is apparently running down – like a heat engine run-
ning out of steam, or a clock unwinding – then perhaps, they thought, nature
has some process up its sleeve that can serve to wind the universe up again.
Some sought this countervailing tendency in specific systems. For example,
it was commonly supposed at the turn of the twentieth century that life
somehow circumvents the strictures of thermodynamics and brings about

10
calling
it his “greatest mistake.” Yet the theory refuses to lie down. Only this year, it
was revived yet again by L. S. Schulman.
11
The notion of a cyclic universe is, of course, an appealing one, and
one that is deeply rooted in many ancient cultures; it persists today in
Hinduism, Buddhism, and Aboriginal creation myths. The anthropologist
Mircea Eliade
12
termed it “the myth of the eternal return.” In spite of
detailed scrutiny, however, the Second Law of Thermodynamics remains
on solid scientific ground. So solid, in fact, that the astronomer Arthur
Eddington felt moved to write,
13
“if your theory is found to be against the
second law of thermodynamics I can give you no hope; there is nothing for
it but to collapse in deepest humiliation.” Today, we know that there is noth-
ing anti-thermodynamic about life. As for the cyclic universe theory, there is
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no observational evidence to support it (indeed, there is some rather strong
evidence to refute it).
14
3.
the true nature of cosmic evolution
In this chapter I wish to argue, not that the Second Law is in any way sus-
pect, but that its significance for both theology and human destiny has been

If the piston is now withdrawn again, restoring the gas to its original volume,
the temperature will fall once more. In a reversible cycle of contraction and
expansion, the final state of the gas will be the same as the initial state. What
happens is that the piston must perform some work in order to compress
the gas against its pressure, and this work appears as heat energy in the gas,
raising its temperature. In the second part of the cycle, when the piston is
withdrawn, the pressure of the gas pushes the piston out and returns exactly
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Paul Davies
the same amount of energy as the piston had injected. The temperature
of the gas therefore falls to its starting value when the piston returns to its
starting position.
However, in order for the cycle to be reversible, the piston must move
very slowly relative to the average speed of the gas molecules. If the pis-
ton is moved suddenly, the gas will lag behind in its response, and this will
cause a breakdown of reversibility. This is easy to understand. If the piston
moves fast when it compresses the gas, there will be a tendency for the gas
molecules to crowd up beneath the piston. As a result, the pressure of the gas
beneath the piston will be slightly greater than the pressure within the body
of the gas, and so the piston will have to do rather more work to compress
the gas than would have been the case had it moved more slowly. This will
result in more energy being transferred from the advancing piston to the
gas than would otherwise have been the case. Conversely, when the piston
is suddenly withdrawn, the molecules have trouble keeping pace and lag
back somewhat, thus reducing the density and pressure of the gas adjacent
to the piston. The upshot is that the work done by the gas on the piston
during the outstroke is somewhat less than the work done by the piston on
the gas during the instroke. The overall effect is a net transfer of energy from

is provided by the gravitational energy of the universe. This has some odd
features, because gravitational energy is actually negative. Think, for exam-
ple, of the solar system. One would have to do work to pluck a planet from its
orbit around the sun. The more material concentrates, the lower the gravi-
tational energy becomes. Imagine a star that contracts under gravity; it will
heat up and radiate more strongly, thereby losing heat energy and making its
gravitational energy more negative in order to pay for it. Thus the principle
that a system will seek out its lowest energy state causes gravitating systems
to grow more and more inhomogeneous with time. A smooth distribution
of gas, for example, will grow clumpier with time under the influence of
gravitational forces. Note that this is the opposite trend from the case of a
gas, in which gravitation may be ignored. In that case, the Second Law of
Thermodynamics predicts a transition toward uniformity. This is only one
sense in which gravitation somehow goes “the wrong way.”
It is tempting to think of the growth of clumpiness in gravitating systems
as a special case of the Second Law of Thermodynamics – that is, to regard
the initial smooth state as a low-entropy (or ordered) state, and the final
clumpy state as a high-entropy (or disordered) one. It turns out that there
are some serious theoretical obstacles to this simple characterization. One
such obstacle is that there seems to be no lower bound on the energy of
the gravitational field. Matter can just go on shrinking to a singular state
of infinite density, liberating an infinite amount of energy on the way. This
fundamental instability in the nature of the gravitational field forbids any
straightforward treatment of the thermodynamics of self-gravitating systems.
In practice, an imploding ball of matter would form a black hole, masking
the ultimate fate of the collapsing matter from view. So from the outside,
there is a bound on the growth of clumpiness. We can think of a black hole
as the equilibrium end state of a self-gravitating system. This interpretation
has been confirmed by Stephen Hawking, who proved that black holes are
not strictly black, but glow with thermal radiation.