How important is the human race in the scheme of things? According to the Epistle
to Diognetus, a Christian work of the early second century, “God loved the race
of men. It was for their sakes that He made the world.” The consensus of later
Christian tradition does not go quite that far, holding that the purpose of
Creation is to manifest God’s glory, not simply to benefit mankind. And yet
Scripture and tradition certainly concur in teaching that the human race has
a central place in the divine plan. In the Book of Genesis, the six days of
creation culminate in the creation of man, and man alone of all the creatures
is said to be made “in the image of God.” If we are not the sole or the chief
end of Creation, it is nevertheless the Jewish and Christian view that in creating
the world God had the human race in mind. Indeed, St. Paul tells the Ephesians
that they were chosen by God and destined to be His sons “before the foundation
of the world.”

On the other hand, we have often been told, science regards man and his place
in the world very differently. In the story of science as it is told by materialists
the human race is not central to the purpose of the universe for the simple
reason that the universe has no purpose. This is the view set forth in a well–known
passage in Steven Weinberg’s best–selling book The First Three Minutes:

It is almost irresistible
for humans to believe that we have some special relation to the universe, that
human life is not just a farcical outcome of a chain of accidents . . . but
that we were somehow built–in from the beginning. . . . It is very hard for
us to realize that [the entire earth] is just a tiny part of an overwhelmingly
hostile universe. . . . The more the universe seems comprehensible, the more
it also seems pointless.

It is the view not only of Weinberg but of many scientists that the progress
of science has more and more made the universe appear “pointless,” and the human
race an accidental by–product of blind material forces. Indeed, this is thought
by many to be the key lesson that science has to teach us. A particularly forthright
champion of this view is the zoologist Richard Dawkins, who writes that “the
universe we observe has precisely the properties we should expect if there is
at bottom no design, no purpose, no evil, no good, nothing but pointless indifference.”

The pointlessness of the cosmos and its indifference to human beings is also
a main theme in the writings of the zoologist Stephen Jay Gould, who claims
that the human race is a freak accident of evolutionary history, merely “a tiny
twig on an ancient tree of life.” We are, said Bertrand Russell, but “a curious
accident in a backwater” of the universe.

Certainly, much in the history of science encourages this “marginalization
of man.” If nothing else, the very size of the cosmos seems to tell of our insignificance.
And yet, discussions about the size and age of the universe do not come to grips
with the real question: Is the human race an accident, or were we meant to be
here? To put it in Weinberg’s terms, were we “somehow built–in from the beginning?”

As it happens, new light has been shed on this question by the discoveries
of modern physics. It has been noticed, especially since the work of the astrophysicist
Brandon Carter in the 1970s, that there are many features of the laws of nature
that seem arranged, even “fine–tuned,” to make possible the existence of life,
including intelligent beings such as ourselves. At least on the face of it,
these so–called “anthropic coincidences” would appear to support the idea that
we were built–in from the beginning. Even some former atheists and agnostics
have seen in them impressive evidence of a divine plan. And yet, many others
maintain that a perfectly naturalistic explanation of these coincidences is
possible. Rather than settling the age–old questions, then, the “anthropic”
arguments seem only to have generated new controversy. Before getting into that
controversy, it will be helpful to look at a few examples of anthropic coincidences.
I will start with a detailed look at two of the most famous examples, both of
which concern the origin of the chemical elements needed for life.

All life is based on chemistry—very complex chemistry, as even a cursory look
at a biochemistry textbook makes clear. The human body, for instance, is made
up of no fewer than twenty–five different chemical elements. Altogether, almost
a hundred chemical elements occur naturally, the smallest being hydrogen, and
the largest uranium. Where did all these elements come from? And why are the
chemical possibilities of our universe so rich?

Hydrogen has been around since very soon after the Big Bang. But almost all
of the other elements were forged later, either in the deep interiors of stars,
or in the violent explosions called supernovas with which some stars end their
lives. These supernova explosions are also important for life because they spew
the elements made within stars out into space where they can form new stars,
or planets, or people. Indeed, most of the elements in our bodies were made
inside stars that exploded before the sun was born. We are quite literally made
of stardust.

For our purposes, it is crucial to note that the elements are formed in a sequential
manner by nuclear reactions in which the nuclei of smaller atoms fuse together
to make the nuclei of larger atoms. These same “nuclear fusion” reactions also
produce the energy radiated by stars (including, of course, the sun), energy
that is essential to support life. The first step in the process of forging
the elements is the fusing together of pairs of hydrogen nuclei to make something
called “deuterium.” Deuterium is the first and vital link in the whole chain.
If deuterium had been prevented from forming, none of the later steps could
have taken place, and the universe would have contained no elements other than
hydrogen. This would have been a disaster, for it is scarcely conceivable that
a living thing could be made of hydrogen alone. Moreover, had the deuterium
link been cut, the nuclear processes by which stars burn would have been prevented.

Everything thus depends on hydrogen being able to fuse to make deuterium. Here
is where the first remarkable anthropic coincidence comes in. The force of nature
that cements nuclei together is called the “strong nuclear force.” Had the strong
nuclear force been weaker by even as little as 10 percent, it would not have
been able to fuse two hydrogens together to make deuterium, and the prospects
of life would have been dim indeed. But this is only the half of it. Had the
strong nuclear force been only a few percent stronger than it is, an
opposite disaster would have occurred. It would have been too easy for
hydrogen nuclei to fuse together. The nuclear burning in stars would have gone
much too fast. Stars would have burned themselves out in millions of years or
less, rather than the several billion years that stars like the sun last. However,
the history of life on earth suggests that billions of years are required for
the evolution of complex life such as ourselves. The upshot of all these considerations
is that the strong nuclear force has just the right strength: a little stronger
or weaker and we would not have been here.

Once deuterium is made, deuterium nuclei can combine by fusion processes to
make helium nuclei. These steps happen very readily. At this point, however,
another critical juncture is reached: somehow, helium nuclei must fuse to make
yet larger elements. But all the obvious ways this could happen are forbidden
by the laws of physics. In particular, two helium nuclei cannot fuse together.
This was quite a puzzle for nuclear theorists and astrophysicists. How did all
the elements larger than helium come to be made?

The answer was found by Fred Hoyle, who suggested that nature in effect did
a large double step to get past the missing rung in the ladder. When two helium
nuclei collide in the interior of a star they cannot fuse permanently, but they
do remain stuck together momentarily—for about a hundredth of a millionth of
a billionth of a second. In that tiny sliver of time a third helium nucleus
comes along and hits the other two in a three–way collision. Three heliums,
as it happens, do have enough sticking power to fuse together permanently.
When they do so they form a nucleus called “carbon–12.” This highly unusual
triple collision process is called the “three–alpha process,” and it is the
way that almost all of the carbon in the universe is made. Without it, the only
elements around would be hydrogen and helium, leading to an almost certainly
lifeless universe.

It was in looking closely at the three–alpha process that Hoyle discovered
one of the most dramatic of the anthropic coincidences. Hoyle’s preliminary
calculations showed him that such a rare event as the three–alpha process would
not make enough carbon unless something greatly enhanced its effectiveness.
That something, he realized, must be what is called in physics a “resonance.”
There are many examples of resonance phenomena in everyday life. A big truck
going by a house can rattle the window panes if the frequency of the sound waves
matches up, or “resonates,” with one of the “natural modes of vibration” of
the window. Similarly, opera singers can shatter wine glasses by hitting just
the right note. In other words, an effect that would ordinarily be very feeble
can be greatly enhanced if it occurs resonantly.

Now, it happens that atomic nuclei too have characteristic “notes” or “modes
of vibration,” called “energy levels,” and nuclear reactions can be enormously
facilitated if they hit upon one of these energy levels. Hoyle pointed out that
the three–alpha process could have produced enough carbon only if the carbon–12
nucleus has an energy level in just the right place. Indeed, experiments done
shortly thereafter confirmed that it does. Had this energy level of carbon–12
been only a few percent higher or lower in frequency, the three–alpha process
would have been out of tune, as it were. Without carbon, and the elements heavier
than carbon, life as we know it would have been unable to exist.

One sees that the making of the chemical elements needed for life was, to borrow
the Duke of Wellington’s comment on his victory at Waterloo, “a damn close run
thing.”

One can see anthropic coincidences not only in the nuclear processes that formed
the elements, but in many quite various aspects of the laws of physics. To give
a better idea of this variety, I will describe a few more examples, though in
less detail.

The “strong nuclear force” is one of four basic forces of nature that is presently
known. The others are the so–called “weak interaction,” gravity, and electromagnetism.
In the phenomena of our everyday lives, electromagnetism plays a dominant, although
perhaps not obvious, role. For example, matter is held together by the electrical
attraction of atoms, and light consists of electromagnetic waves. In contrast,
the strong nuclear force plays no direct role in effects that we can experience.
That is because its influence extends only over subatomic distances. Nevertheless,
the electromagnetic force is intrinsically much weaker than the strong nuclear
force. In fact it is, in a certain well–defined sense, about one hundred times
weaker. This is very fortunate. Had the electromagnetic force not been
intrinsically much weaker than the strong nuclear force, the electrical energy
packed inside a hydrogen nucleus would have been so great as to render it unstable.
The “weak interaction” would then have made all the hydrogen in the world decay
radioactively, with a very short half–life, into other particles. The world
would have been left devoid of hydrogen, and therefore almost certainly of life.
For water, which is indispensable for life, contains hydrogen, as do almost
all organic molecules. We see, then, how life depends on a delicate balance
among the various fundamental forces of nature, and in particular on the relative
feebleness of electromagnetic effects.

Another fortunate fact has to do with the flatness of space. Einstein taught
us that space–time is not flat, but curved. Because of this curvature, bodies
seem to attract each other by the force we call gravity. However, it turns out
that the space of our universe, if looked at on large enough scales of distance,
is on average astonishingly flat. The “spatial curvature,” as it is called,
is very small. In fact, shortly after the Big Bang the spatial curvature of
the universe was, to the accuracy of many decimal places, equal to zero. For
a long time, this was referred to as the “flatness problem,” since no one could
think of a good explanation for it. However, while long a difficult thing for
theorists to explain, this flatness of space is very fortunate. Had the flatness
of space not been fantastically small to begin with, the universe would
either have collapsed and ended a very short time—a tiny fraction of a second—after
it began, or would have undergone such a tremendously rapid expansion that it
would have torn matter and even atoms asunder.

So far I have described various quantities, like the strengths of the strong
nuclear force and the flatness of space, that had to be “fine–tuned” to very
special numerical values to make life as we know it possible. But there are
also certain gross qualitative features of the laws of physics that are “anthropically”
important. One example is the fact that space is three–dimensional. We take
this fact for granted, but we shouldn’t. That space has three dimensions is
an empirical fact, not a metaphysical necessity. Theoretical physicists study
hypothetical universes with other numbers of dimensions all the time. If the
world had not had three space dimensions, but four or more of them, the gravitational
force between two objects would have depended in a different way upon the distance
between them. And that, in turn, would have made it impossible for planets to
orbit stably around stars: they would either have plummeted into stars or flown
off into space. (Interestingly, the first person to point out this consequence
of a different law of gravity was the Anglican clergyman William Paley. Paley
was one of the first people to think about anthropic coincidences in the laws
of nature.) In the same way, the orbits of electrons in atoms would not have
been stable, and life based on chemistry would have been impossible.

On the other hand, had there been fewer than three space dimensions,
complex organisms would doubtless have been impossible for quite a different
reason. Complex neural circuitry, as is needed in a brain, would not be possible
in one or two dimensions. If one tries to draw a complicated circuit diagram
on a two–dimensional surface, one finds that the wires have to intersect each
other many times, leading to short–circuits.

As a final example, the fact that nature obeys the principles of quantum theory
is highly important for the possibility of life. It turns out that matter would
not be stable in a non–quantum world. People generally suppose that the Heisenberg
Uncertainty Principle makes the world, at least at the atomic level, a fuzzier
and more indefinite place. However, paradoxical as it may sound, that principle
is ultimately responsible for the fact that subatomic particles form stable
atoms with well–defined chemical properties. Were it not for the principles
of quantum theory, matter would be amorphous and protean to such a degree that
it is hard to imagine a living organism being possible.

What do physicists make of such anthropic coincidences? There is a wide spectrum
of opinion. Some of the greatest scientists of our time, including Yacov Zel’dovich,
Andrei Sakharov, Lev Okun, Martin Rees, and Steven Weinberg, to name but a few,
have been interested in them and have devoted study to them. Nevertheless, the
subject provokes discomfort and even hostility in much of the physics community,
partly due to the specter of teleology. Physicists have a strong instinctive
professional aversion to teleological thinking, because, at least in the physical
sciences, the scientific revolution was to a large extent made possible by the
rejection of teleology in favor of mechanism. I suspect, though, that there
is more to this nervousness about anthropic coincidences—namely, the specter
of religion.

Yet, scientific skepticism about these ideas is not based entirely on such
prejudices. There are several arguments against the idea of anthropic coincidences
that must be taken seriously.

First, it is argued that we cannot really know what is necessary for life to
arise. Life might take forms that are utterly alien to our experience. While
the life that we know about makes use of a certain kind of physics, who knows
whether, with different physical laws, completely different possibilities for
life might have existed?

This objection has some real force. In some cases, I think, all we can honestly
assert is that it appears highly unlikely that life could have arisen had the
laws of physics been different in this or that respect—unlikely, but perhaps
not utterly impossible. In such questions absolute certainty may not be attainable
due to our limited imaginations. However, absolute certainty may be beside the
point. We might still be left with strong indications that the cosmos
was made with us in mind, even if those indications do not add up to a proof.
After all, the reasons that scientists like Weinberg, Dawkins, and Gould give
for reaching the opposite conclusion are also not subject to proof.

The second objection is that conventional scientific explanations may exist
for some if not all of the facts that now appear to be anthropic coincidences.
In fact, among the examples I gave of anthropic coincidences I included two
where we may already have at least a partial scientific explanation of the facts
involved. The fact that the electromagnetic force is much weaker than the strong
nuclear force, for instance, is probably partly explained by the idea of “grand
unification.” There are reasons to believe that the electromagnetic force, the
weak interaction, and the strong nuclear force are really all aspects of one
underlying “grand unified” force. If that is so, then the strengths of the different
forces are not independent of each other, but are tied together in a definite
way. In fact, in a typical grand unified model—and many such models have been
proposed—the electromagnetic force does indeed come out to be much weaker than
the strong nuclear force. Another of the anthropic coincidences concerns the
flatness of space. This too is a fact for which we now have a probable explanation:
it is thought to be a consequence of an effect called “cosmic inflation.”

Thus, it is more than likely that at least some of the facts about the laws
of physics that appear favorable to our existence do have conventional scientific
explanations. Even if that proved to be true of all of them, however, it would
not explain away the coincidental nature of these facts. The critical point
was well expressed by the noted astrophysicists Bernard Carr and Martin Rees:

One day we may have a more
physical explanation for some of the relationships . . . that now seem genuine
coincidences. For example, [some of them] may eventually be subsumed as a consequence
of some presently unformulated unified theory. However, even if all apparently
anthropic coincidences could be explained in this way, it would still be remarkable
that the relationships dictated by physical theory happened also to be those
propitious for life. [emphasis added]

In other words, suppose that there are twenty numerical relationships that
have to hold in order for life to be possible, and suppose that in some physical
theory every one of those twenty relationships happens to hold as a consequence
of some underlying physical principle. That would itself amount to an
astonishing coincidence.

This brings us to the third objection, which is closely related to the second.
Einstein famously asked whether God had a choice in how He made the world. Many
physicists nowadays suspect not. They suspect that all mathematical relationships
in the laws of physics will turn out to be dictated by some deep underlying
principles that leave no room for things to have been otherwise. One frequently
hears the possibility discussed that the laws of physics are “unique.” The idea
is that everything about the physical world—the kinds of particles that exist,
the kinds of forces and their relative strengths, the number of dimensions of
space and its degree of flatness, the energy levels of the carbon–12 nucleus,
and so on, down to the smallest detail—may have to be as they are on account
of some fundamental physical principles. If so, God could not have the freedom
to arrange the laws of nature to be “propitious for life” or otherwise, since
His hands were completely tied.

However, this is plainly wrong. Physical principles could not have tied God’s
hands, for the simple reason that He could have chosen some other principles
upon which to base the laws of physics. For example, while the relative feebleness
of the electromagnetic force, which we saw to be anthropically fortunate, may
be a necessary outcome of a “grand unified” framework, it was by no means necessary
that the world be built according to such a “grand unified” framework. In fact,
we still do not know whether it is. So, in this particular matter God clearly
did have a choice—indeed, many choices, as there are many mathematically self–consistent
frameworks that involve “grand unification” and many that do not.

As a matter of fact, there are an infinite number of mathematically self–consistent
sets of laws of physics that could have been chosen as the basis for the structure
of a universe. This is incontestable. When those (good) physicists talk about
the laws of physics being possibly “unique,” they are speaking very loosely.
What they really have in mind is the idea that a unique set of laws may be necessary
if it has to satisfy certain assumed preconditions. For example, many theorists
believe that there is only one possible set of laws—“superstring theory”—that
can incorporate simultaneously the principles of quantum theory and the principles
of Einsteinian gravity. However, there is certainly no reason to suppose a priori
that the universe had to incorporate either quantum theory or Einsteinian gravity.
In short, the universe could have been made differently, and if it had been
life might not have been able to arise. These assertions, it seems to me, can
hardly be disputed.

Before one leaps to the conclusion that the anthropic coincidences inevitably
point to God, one should be aware of the fact that many of the scientists who
have written about anthropic coincidences are atheists. (Steven Weinberg is
a notable example.) It is their view that the laws of physics being “propitious”
for life, far from pointing to the importance of life or human beings in some
cosmic “plan,” has a purely naturalistic, scientific explanation. The explanation
that they offer is based on an idea that is called the Anthropic Principle.
There are various anthropic principles that are discussed, but the only one
taken seriously by scientists as being plausible and having any explanatory
power is called the Weak Anthropic Principle, or WAP for short. It should be
noted that careless writers often talk about “the anthropic principle” when
what they really mean is “anthropic coincidences.” The two ideas should not
be confused: the anthropic coincidences are facts, while the anthropic “principle”
is a speculative hypothesis for explaining those facts.

The idea of the Weak Anthropic Principle is easiest to grasp using an analogy.
There are many things about conditions on the planet Earth that are propitious
for life. If the Earth were much smaller, then it would not be able to retain
an atmosphere. If it were much bigger, it would retain a lot of hydrogen in
its atmosphere, which might be bad for life. If it were much closer to the sun
it would be too hot to have liquid water, if much farther away it would be too
cold. Has someone “fine–tuned” conditions here to make life possible? Not necessarily.
There are presumably a vast number of planets in the universe. (In the context
of present–day theory, it is not unlikely that there are an infinite number.)
Some planets are hot, some cold. some big, and some small. They undoubtedly
span a vast range of physical and chemical conditions. It seems inevitable that
some of them would happen to have the right conditions for life.

To put it another way, if one tried one key in an unknown lock, it would be
an astonishing coincidence if it worked. But if one tried a million keys it
would not be greatly surprising if one of them did.

The idea of the Weak Anthropic Principle is that the same kind of argument
can be used not just about planets, but about universes. Suppose that there
are a huge number of universes. Some may have three space dimensions, some two,
some four, and so on. In some, the electromagnetic force may be weaker than
the strong nuclear force, in others it may be stronger, and in others there
may be no such thing as the electromagnetic force at all. That is, all sorts
of possible physical laws might be tried out in different universes. If so,
it might not be surprising, assuming that a great enough number and variety
of universes existed, that some of them would have just the right laws of physics
to permit life. And of course, to the inhabitants of such an exceptional universe,
it might seem that someone had arranged things in their universe with them in
mind. This is an old idea, going back at least to David Hume, who suggested
that “many worlds might have been botched and bungled, throughout an eternity,
ere this system was struck out.”

Before examining this idea critically, one must distinguish two versions of
it. In the version that physicists take seriously, the many “universes” are
not really distinct and separate universes at all, but domains or regions of
one all–encompassing Universe. The domains are far apart in space, or otherwise
prevented from communicating with each other. Conditions are assumed to be so
different from one domain to another that they appear superficially to have
different physical laws. However, at a deeper level all the domains are really
controlled by one and the same set of fundamental laws. These laws also control
what types of domains the universe has, and how many of each type.

The other version of the idea posits the existence of a large number of universes
that really are universes, distinct and unconnected in any way with each other.
Each has its own set of physical laws. There is no overarching physical system
of which each is a part. One can understand why this version is not discussed
among scientists. At least in the many–domains version all the domains are part
of the same universe as we, so that, even if we cannot in practice observe them
directly, we might hope at least to infer their existence theoretically from
a deep understanding of the laws of nature. In the many–universes version, this
is not the case.

Let us first consider the many–domains version of the idea. It is not, as many
suppose, a foolish or extravagant one. In fact, some of the kinds of theories
that fundamental physicists think about nowadays actually imply that the universe
must have domains. In such theories the different domains can differ radically
from each other, with even different kinds of particles and different forces.
Thus it is not unreasonable to suppose that a many–domains version of the Weak
Anthropic Principle might turn out to be the explanation for some of the anthropic
coincidences. Nevertheless, I do not believe that this would subtract much from
the force of the anthropic coincidences as evidence for purpose in the universe.
The reason is simple. The whole point of the anthropic coincidences is that
the laws of physics have to be very special to allow life to exist. But this
requirement is not avoided by the many–domains idea, for the laws of physics
also have to be very special to give rise to a universe with domains, especially
domains of a sufficiently rich variety to do what the Weak Anthropic Principle
demands of them.

One can illustrate the point by means of a rather whimsical analogy. Suppose
you were looking for a specific obscure recipe for, say, goulash. If the first
book you took at random from the cooking shelf of the library happened to have
exactly that recipe, you would regard it as a great coincidence. If you then
discovered that the book contained every recipe for goulash ever invented,
you would cease to regard it as coincidental that it had the one of particular
interest to you. But you would be surprised nonetheless, for one does not expect
a cookbook to treat that particular category of food so comprehensively. The
fact that it happened to be so comprehensive in its selection of goulash, when
it was goulash that you needed, would itself count as a remarkable coincidence.

Likewise, it is not something to be taken for granted that the universe would
have as many domains as needed for the anthropic coincidences to seem unsurprising.
On the contrary, in the kinds of theories physicists have found reason to study,
the universe is not nearly so inclusive. True, some of those theories suggest
that the universe has domains, but they typically realize only a few possibilities,
not the vast smorgasbord of possibilities needed to explain all of the
many anthropic coincidences that have been identified.

The many–universes version of the anthropic principle is in a way simpler.
In the many–domains idea, one has to account for the domains by a physical mechanism.
Consequently the laws of physics have to be “engineered,” as it were, to produce
a universe with a sufficiently rich variety of domains. In the many–universes
idea, on the other hand, it is simply posited that many types of universe exist.
What types of universe exist and what types do not? That is not a question that
the laws of physics can possibly answer, since each universe has ex hypothesi
its own laws of physics. If some kinds of universe exist while others
do not, it would seem to suggest that Someone has made choices. Far from destroying
the case that a cosmic Designer exists, the many–universes idea only strengthens
it.

A last–ditch way out for the opponents of cosmic design would be to say that
all conceivable universes exist, i.e., any universe that is logically
and mathematically self–consistent actually exists. This idea has a breathtaking
simplicity. It would explain existence: to exist is to be self–consistent. It
would remove the need for a Designer or a Creator. Whereas the “unique laws
of physics” idea got rid of a Designer by saying that there are no choices for
a Designer to make as there is only one real possibility, here the Designer
is eliminated by saying that there are infinitely many possibilities, but that
no one has selected among them.

There is, however, a fatal problem with this way of getting rid of the cosmic
Designer. It cannot explain why we live in a universe that is so astonishingly
lawful. Among all the logically possible universes, ones that have the perfection
of order and lawfulness that ours displays are highly exceptional, just as among
all possible rocks, a perfect gem that has absolutely no flaws in it is almost
infinitely unlikely. Why doesn’t our universe exhibit occasional departures
from its regularities—the regularities we call the laws of physics—just as gemstones
have occasional departures from their regularities? No answer to this is possible.
If all possible universes exist, it becomes a tremendous miracle that we live
in a universe of perfect, or nearly perfect, lawfulness. It is a miracle, in
other words, that miracles do not occur around us all the time.

The Weak Anthropic Principle, whether in its many–universes or many–domains
versions, cannot succeed in explaining the anthropic coincidences away or making
them any less coincidental. In the final analysis one cannot escape from two
very basic facts: the laws of nature did not have to be as they are; and the
laws of nature had to be very special in form if life were to be possible. In
my view these facts lend themselves most naturally to a religious interpretation.
Certainly, they tend to undercut the claim so often confidently made by materialists
that the discoveries of science point to a universe without meaning or purpose,
in which man is an accidental by–product.

Having said all this, we remain with a question very troubling to many: Why
is the universe so big? How can we claim to be important in a universe that
dwarfs us in its scales of space and time? There is at least a paradox here.
It is a paradox that was not lost upon the Psalmist, who exclaimed, “When I
consider the heavens, the work of thy fingers, the moon and the stars, which
thou hast ordained; What is man, that thou art mindful of him, and the son of
man, that thou visit­ est him?”

One answer, of course, is the traditional one. The universe was not made only
for our benefit. As the Psalmist also said, “the heavens proclaim the glory
of God.” If it is the glory of God that they proclaim, then there is no particular
reason why they should have to be made to human scale. In fact, in the fifteenth
century Nicolas of Cusa argued that only a universe of infinite extent would
be worthy of the Creator and able to manifest His glory.

The traditional answer is a good one, but there may be another. It turns out
that the very age and vastness of the universe may have an “anthropic” significance.
Life emerged in our universe in a way that required great stretches of time.
As we have seen, most of the elements needed for life were made deep in stars.
Those stars had to explode to disperse those elements and make them available
before life could even begin to evolve. That whole process alone required billions
of years. The evolution of human life from those elements required billions
of years more. Thus, the briefness of human life­ spans and even of human history
compared with the age of the universe may simply be a matter of physical necessity,
given the developmental way that God seems to prefer to work. It takes longer
for a tree to grow to maturity than the fruit of the tree lasts. It took much
longer for the universe to grow to maturity than we last.

Physics can also suggest why the universe has to be so large. The laws of gravity
discovered by Einstein relate the size of the universe directly to its age.
The fact that the universe is many billions of light–years across is related
to the fact that it has lasted several billions of years. Perhaps we would be
less daunted by a cozy little universe the size, say, of a continent. But such
a universe would have lasted only a few milliseconds. Even a universe the size
of the solar system would have lasted only a few hours. A universe constructed
in such a way as to evolve life may well have had to extend widely in space
as well as in time. It may well be that the frightening expanses that are so
often said to be a sign of human insignificance may actually, like so many other
features of our strange universe, point to man, as they also proclaim the glory
of God.

Stephen M. Barr is a theoretical particle physicist at the Bartol Research
Institute of the University of Delaware.