The Anthropic Coincidences: A Natural Explanation
Does the Cosmos Show Evidence of
Published in Skeptical
Inquirer Vol. 23, No. 4, July/August 1999.
Posted September 9, 2002
Poking out of the noise
Interpreting the coincidences
The natural scenario
Claims that scientists have
uncovered supernatural purpose to the universe have been widely reported
recently in the media. The so-called anthropic coincidences, in which the
constants of nature seem to be extraordinarily fine-tuned for the production of
life, are taken as evidence. However, no such interpretation can be found in
scientific literature. All we currently know from fundamental physics and
cosmology remains consistent with a universe that evolved by purely natural
For about a
decade now, an increasing number of scientists and theologians have been
asserting, in popular articles and books, that they can detect a signal of
cosmic purpose poking its head out of the noisy data of physics and cosmology
(see, for example, Swinburne 1990, Ellis 1993, Ross 1995). This claim has been
widely reported in the media (see, for example, Begley 1998, Easterbrook 1998),
perhaps misleading lay people into thinking that some kind of new scientific
consensus is developing in support of supernatural beliefs. In fact, none of
this purported evidence can be found in the pages of scientific journals, which
continue to operate within a framework in which all physical phenomena are
As the argument goes, the data are
said to reveal a universe that is exquisitely fine-tuned for the production of
life. This precise balancing act is claimed to be a highly unlikely result of
mindless chance. An intelligent, purposeful, and indeed personal Creator must
have made things the way they are.
As cosmologist and Quaker George
Ellis explains it: "The symmetries and delicate balances we observe require an
extraordinary coherence of conditions and cooperation of laws and effects,
suggesting that in some sense they have been purposefully designed" (Ellis 1993:
97). Others have been less restrained in insisting that God is now
required by the data and that this God must be the God of the Christian
Bible (see, for example, Ross 1995).
The fine-tuning argument is based on
the fact that earthly life is very sensitive to the values of several
fundamental physical constants. Making the tiniest change in any of these, and
life as we know it would not exist. The delicate connections between physical
constants and life are called the anthropic coincidences (Carter 1974,
Barrow and Tipler 1986). The name is a misnomer. Human life is not singled out
in any special way. At most, the coincidences show that the production of carbon
and the other elements that make earthly life possible required a sensitive
balance of physical parameters.
For example, if the gravitational
attraction between protons in stars had not been many orders of magnitude weaker
than their electrical repulsion, stars would have collapsed long before nuclear
processes could build up the chemical periodic table from the original hydrogen
and deuterium. Furthermore, the element-synthesizing reactions in stars depend
sensitively on the properties and abundances of deuterium and helium produced in
the early universe. Deuterium would not exist if the neutron-proton mass
difference were just slightly displaced from its actual value; neutrons,
unstable in a free state, were stored in deuterium for their later use in
building the elements.
The existing relative abundances of
hydrogen and helium also implies a close balance of the relative strengths of
the gravitational and weak nuclear forces. A slightly stronger weak force and
the universe would be 100 percent hydrogen as all neutrons decayed away before
assembling into deuterium and helium. A slightly weaker weak force and we would
have a universe that is 100 percent helium; in that case neutrons would not have
decayed and left the excess of protons that formed hydrogen. Neither of these
extremes would have allowed for the existence of stars and life, as we know it,
based on carbon chemistry. Barrow and Tipler (1986) list many other such
"coincidences," some remarkable, others somewhat strained.
3. Interpreting the coincidences
interpretation of the anthropic coincidences in terms of purposeful design
should be recognized as yet another variant of the ancient argument from
design that has appeared in many different forms over the ages. The
anthropic design argument asks: how can the universe possibly have obtained the
unique set of physical constants it has, so exquisitely fine-tuned for life as
they are, except by purposeful design--design with life and perhaps humanity in
This argument, however, has at least
one fatal flaw. It makes the wholly unwarranted assumption that only
one type of life is possible --the particular form of carbon-based life
we have here on earth. Even if this is an unlikely result of chance, some
form of life could still be a likely result. It is like arguing that a
particular card hand is so improbable that it must have been
Based on recent studies in the
sciences of complexity and "Artificial Life" computer simulations, sufficient
complexity and long life appear to be primary conditions for a universe to
contain some form of reproducing, evolving structures. This can happen with a
wide range of physical parameters, as has been demonstrated (Stenger 1995). The
fine-tuners have no basis in current knowledge for assuming that life is
impossible except for a very narrow, improbable range of
Amusingly, the new cosmic
creationists contradict the traditional design argument of the biological
creationists, that the universe is so uncongenial to life that life could
not have evolved naturally. The new creationists now tell us that the universe
is so congenial to life that the universe could not have evolved
Since all scientific explanations
until now have been natural, then it would seem that the first step, before
asserting purposeful design, is to seek a natural explanation for the anthropic
coincidences. Such a quest would avoid the invocation of supernatural agency
until it is absolutely required by the data.
almost two decades, the inflationary big bang has been the standard model
of cosmology (Guth 1981, 1997; Linde 1987, 1990, 1994). We keep hearing, again
from the unreliable popular media, that the big bang being is in trouble and the
inflationary model is dead. In fact, no viable substitute has been proposed that
has near the equivalent explanatory power.
The inflationary big bang offers a
plausible, natural scenario for the uncaused origin and evolution of the
universe, including the formation of order and structure--without the violation
of any laws of physics. These laws themselves are now understood far more deeply
than before, and we are beginning to grasp how they too could have come about
naturally. The natural scenario I will describe here has not yet risen to the
exalted status of a scientific theory. However, the fact that it is consistent
will all current knowledge and cannot be ruled out at this time, demonstrates
that no rational basis exists for introducing the added hypothesis of
supernatural creation. Such a hypothesis is simply not required by the
According to the proposed natural
scenario, by means of a random quantum fluctuation the universe "tunneled" from
pure vacuum ("nothing") to what is called a false vacuum, a region of
space that contains no matter or radiation but is not quite nothing. The space
inside a bubble of false vacuum is curved, or warped, and a small amount of
energy is stored in that curvature, like the potential energy of a strung bow.
This ostensible violation of energy conservation is allowed by the Heisenberg
uncertainty principle for sufficiently small time intervals.
The bubble then inflated
exponentially and the universe grew by many orders of magnitude in a tiny
fraction of a second. (For a not-too-technical discussion and original
references, see Stenger 1990). As the bubble expanded, its curvature energy
transformed (naturally) into matter and radiation. Inflation stopped, and the
more linear big bang expansion we now experience commenced. As the universe
cooled, its structure spontaneously froze out--just as formless water vapor
freezes into snowflakes whose unique and complex patterns arise from a
combination of symmetry and randomness.
In our universe, the first galaxies
began to assemble after about a billion years, eventually evolving into stable
systems where stars could live out their lives and populate the interstellar
medium with the complex chemical elements such as carbon needed for the
formation of life.
So how did our universe happen to be
so "fine-tuned" as to produce wonderful, self-important carbon structures? As I
explained above, we have no reason to assume that ours is the only possible form
of life and life of some sort could have happened whatever form the universe
took--however the crystals on the arm of the snowflake happened to get arranged
If we have no reason to assume ours
is the only life form, we also have no reason to assume that ours is the only
universe. Many universes can exist, with all possible combinations of physical
laws and constants. In that case, we just happen to be in the particular one
that was suited for the evolution of our form of life. When cosmologists refer
to the anthropic principle, this is all they usually mean. Since we live
in this universe, we can assume it possesses qualities suitable for our
existence. Humans evolved eyes sensitive to the region of electromagnetic
spectrum from red to violet because the atmosphere is transparent in that range.
Yet some would have us think that the causal action was the opposite, that the
atmosphere of the earth was designed to be transparent from red to violet
because human eyes are sensitive in that range. Stronger versions of the
anthropic principle, which assert that the universe is somehow actually
required to produce intelligent "information-processing systems" (Barrow
and Tipler 1986), are not taken seriously by most scientists or
The existence of many universes is
consistent with all we know about physics and cosmology (Smith 1990, Smolin
1992, 1997, Linde 1994, Tegmark 1997). Some theologians and scientists dismiss
the notion as a gross violation of Occam's razor(see, for example, Swinburne
1990). It is not. No new hypothesis is needed to consider multiple universes. In
fact, it takes an added hypothesis to rule them out-- a super law of nature that
says only one universe can exist. But we know of no such law, so we would
violate Occam's razor to insist on only one universe. Another way to express
this is with lines from T. H. White's The Once and Future King:
"Everything not forbidden is compulsory."
The hundred billion galaxies of our
visible universe, each with a hundred billion stars, is but a grain of sand on
the Sahara that exists beyond our horizon, grown out of that single, original
bubble of false vacuum. An endless number of such bubbles can very well exist,
each itself nothing but a grain of sand on the Sahara of all existence. On such
a Sahara, nothing is too improbable to have happened by chance.
I have greatly benefitted from discussions on this subject with Ricardo
Aler Mur, Samantha Atkins, John Chalmers, Scott Dalton, Keith Douglas, Ron
Ebert, Simon Ewins, Jim Humphreys, Bill Jefferys, Kenneth Porter, Wayne Spencer,
Quentin Smith, and Ed Weinmann.
This is a much abridged version of a
longer essay entitled The Anthropic Coincidences: A Natural Explanation
to appear in the British Skeptical Intelligencer.
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Victor J. Stenger is a Professor of
Physics at the University of Hawaii. He is the author of Not By Design: The
Origin of the Universe (Prometheus Books, 1988), Physics and Psychics:
The Search for a World Beyond the Senses (Prometheus Books, 1990), and
The Unconscious Quantum: Metaphysics in Modern Physics and Cosmology
(Prometheus Books, 1995).
This article first appeared at Victor J. Stenger's web site.