The physical world is governed by forces. They control the behavior of everything: the motion of an apple falling, the flow of charges in a wire and the decay of nuclei. Gravitation propels our Earth around the Sun and causes the Universe to expand. In ancient times, Greeks imagined that the whims of gods determined the fates of humans. In modern times, scientists tell us that forces do the same.

Science -- for the most part -- is a description of how nature works. Physicists can compute the trajectory of a missile using Newton's laws of motion or the rate at which a nucleus disintegrates. Paleontologists have mapped out a sketchy, but impressive, three-billion-year-long picture of how the human has arisen, starting from a microbe, evolving to a worm, growing into a fish, emerging as a tetrapod on land, and changing into a mammal, then a monkey, then a man. But science in its present form fails to explain why things are the way they are -- at least at a fundamental level. Why is matter made up of only quarks (the constituents of the protons and neutrons that compose the nuclei of atoms) and leptons (electrons and neutrinos)? Why are there only four fundamental forces and why do they act the way they do? Newton's law of gravitation, F=GMm/r², is a formula, an equation, a mathematical description -- not a reason why gravity exists. Why does the Universe have stars and galaxies? Why does it have planets and life? Should Nature present the laws of physics to mankind like God presented the Ten Commandments to Moses? While some theorists are hoping to obtain a more fundamental explanation of the world, the question "Why?" will always remain. For example, string theory is a speculative, ambitious idea that attempts to unify all matter and all forces into a single structure. If true, it represents a great simplification in our understanding of the world and a great triumph of theoretical physics. But the question still will be "Why strings?"

One way to answer the "why?" question is to evoke God, something that Dr. Lee Smolin in his book The Life of the Cosmos is quick to dismiss. Indeed, many scientists are reluctant to bring a supreme being into the picture for several reasons basic to the scientific methodology: the difficulty of verification through experiment, the potential loss of predictability and the use of an "outside" explanation. Someone might even dare to say "Why God?"

In The Life of the Cosmos, Dr. Smolin attempts to answer why our Universe is the way it is through a new idea called the cosmological natural selection principle. He uses processes and NOT equations to try to accomplish this. Our existence is explained in terms of history rather than by general principles. Cosmological natural selection is an extremely ambitious proposal, comparable to the one of Copernicus at his time that the Earth was not the center of the Universe. Copernicus, of course, was right. However, for every "Copernicus," there are a hundred scientists who have made bold proposals that have turned out to be wrong. The reader may not realize this because the names of scientists who fail are soon forgotten. So if Lee Smolin is correct, his name will be added to the short list of scientific greats. If not correct, he joins a longer list of unknowns who had imaginative ideas that failed.

In fact, many scientists think that Smolin's theory has only a low probably of being correct. In the days of Copernicus, the Earth was the center of the Universe or it was not. Setting human biases aside, Copernicus had a 50-50 chance of being right. In the case of Smolin, the chances of being correct might be 1 in 2⁴⁰, or about 1 in a trillion (see the discussion below).

Dr. Smolin's proposal, a product arising from philosophy, is speculation. In his book, he explicit states this to the reader and he should be commended for doing so. Some scientists write books claiming their "pet theory" to be the accepted truth. Such a practice is misleading and does a disservice to the pursuit of increasing public understanding of science.

Early in his book, Dr. Smolin awakens us to the fact that we live in an improbable universe. There are dozens of parameters pertinent to our world. These parameters are numbers, such as the masses of particles and the strengths of forces, that can in principle be varied. Thus the world could be different: gravity could be ten times stronger than it is; the electron might be twice as light; the proton could be twice as heavy; the electric force might be five times weaker, and so on. Have these parameters been set to special values that make our Universe rich, complex and interesting? In a different universe with a different set of physical laws, structures such as planets, stars and galaxies might not form, and the same might be true for life. Dr. Smolin estimates that the chances that the parameters assume the values of our Universe are 1 in 10²²⁹ -- this probability is a number that begins with a decimal point, is followed by 228 zeros and ends with a 1, an extraordinarily small chance. It is thus surprising that our Universe is so interesting.

What could be the explanation of this miracle? Dr. Lee Smolin offers three answers: (1) a supreme being who can twiddle the dials that control our Universe (2) a unique theory and (3) a natural process similar to organic evolution.

Some scientists -- particularly string theorists - - would vote for explanation (2). Many scieentists would simply "throw their hands up" saying the world is simply the way it is. This, of course, is not an explanation, but some might say that perhaps there is no explanation. Dr. Smolin dismisses these responses as well as (1) because (3) can be so simple. He also rejects explanation (2) for the following reasons. First, finding a unique theory does not explain anything at a fundamental level -- it is almost like God presenting the world with a slab of natural commandments. Second, a unique theory is unlikely to yield the parameters of our Universe so the chances that it exists is 1 in 10²²⁹ . Third, even if string theory is correct, there are countless ways for it to manifest itself (in scientific jargon these manifestations are called vacuum configurations). String theory offers no explanation of why our Universe "has picked" one manifestation over another.

One may try to question whether our Universe really is improbable. Maybe one day, physicists will achieve an understanding that does explain the values of Nature's parameters in a simple way. Or maybe with other values of the masses of particles, the strengths of forces and so on, a universe arises that is very different from ours but still possesses rich and complex structures. In such a hypothetical world, there might be complex self-organizing units that mimic what we call life. It may be that, although our Universe is special in its particular realization of the consequences of its physical laws, that complexity and self-organization are a property of many systems. But all this is speculation and, until otherwise shown, one probably should accept the conclusion that we live in a highly improbable universe. Thus the "why" question becomes more intriguing: "Why is the Universe the way it is, if it is so unlikely?"

Earth has sophisticated life. The chances of randomly throwing organic molecules together to produce a mammal is virtually zero. One might then conclude that the mammal is a miracle. We know that this is not the case. Sophisticated creatures exist because of evolution. Given the right environment and enough time, randomly combining organic molecules can produce primitive microscopic life. That is how life on Earth began. Evolution and billions of years allowed organisms to develop into complicated, macroscopic forms.

Dr. Smolin speculates that an analogous process must have taken place for our Universe. The proposal for cosmological natural selection rests on two general assumptions: (I) There are many universes that can give rise to new universes and (II) the laws of Nature are mutable. These ideas may seem astonishing to the reader, but theorists have often contemplated them.

Before the twentieth century, it was thought that all the stars in the night sky formed one entity. It was not until the 1920's that Edwin Hubble, using a newly constructed powerful telescope, viewed a hazy object in the constellation Andromeda and resolved it into countless points of light -- they were stars. Hubble had discovered a galaxy. Suddenly there were two worlds: the first, consisting of the 200 billion stars in our region of the Universe, and the second, the Andromeda Galaxy. Soon other "worlds" were observed. Nowadays, astronomers estimate that there are roughly 50 billion galaxies in the visible Universe, that is, that part of the Universe for which light has had enough time to reach us on Earth. The revelation of the existence of other galaxies naturally leads to the question "Are there also other universes?"

One popular, as-of-yet-unconfirmed theory of cosmology -- known as inflation -- says that the Universe underwent a tremendous expansion when it was a fraction of a second old. What does it mean for the Universe to expand? According to Einstein's general theory of gravity, space is dynamical -- it can stretch, bend and twist. Astronomers have discovered that distant galaxies are all moving away from one another. The reason: the very fabric of space is stretching in all directions.

Most versions of inflation predict the existence of other universes. These are other worlds, completely disconnected from ours. Many scientists do not like this idea because one would never be able to observe these other universes.

Near the very beginning of time, gravity was in its quantum phase. Although the consistent quantum theory of gravity is not yet known, some cosmologists believe that a multi-universe picture of the world will emerge as part of quantum gravity.

All this is speculation, of course. But the situation is probably similar to the one of Copernicus discussed above. Given our ignorance, there is probably a 50-50 chance that other universes exist.

Theorists have also considered part of assumption (II) that Nature's parameters might be subject to change. Indeed, formulations of string theory predict the existence of extra spatial dimensions. Our world might be nine-dimensional and not three-dimensional. Why don't we see the extra six directions? A possible answer is that they are too small; they are microscopic and beyond our present means of observation. Perhaps during the early stages of the Universe, these extra spatial dimensions started out relatively large and then shrunk in size. It turns out that changes in the volume of the extra dimensions causes parameters such as Newton's constant (which controls the strength of gravity) to vary. Although recent experiments see no variation in Newton's constant, human observations are somewhat restricted to the limited time that humans have been on Earth.

So it is possible that many universes exist and that Nature's parameters change, although both ideas are conjecture. Assumption (I) also requires one universe "giving birth" to others. Dr. Lee Smolin suggests that this happens when a black hole arises. A black hole forms when a tremendous amount of mass becomes concentrated in a relatively tiny region of space. The gravity of such an object so strong that nothing including light can escape. If a light beam were to be aimed upward, it would rise, arc over, and fall back like a jet of water from a hose. Since black holes produce no light, they are dark -- hence their name.

Dr. Smolin imagines that, when matter falls in upon itself to form a black hole, a rebound occurs that spawns one or more new universes. At the same time, the laws of Nature and the values of mass quantities in the new "daughter universes" differ slightly from those of the "mother universe." This is Dr. Smolin's specific proposal for realizing (I) and (II). There is so much speculation involved here that probably few theorists believe that it can be correct. But the issue is not what people think but what is realized in the world. Still, many "why" questions arise. Why should black holes rebound to produce new universes? Why should parameters change slightly and not greatly? Why should they change at all?

Putting these questions aside, what are the consequences of the proposal. First of all, cosmology becomes an evolutionary process, one however that is different from Earth's organic evolution in that universes are not alive and there is no competition among them; there is no "survival of the fittest" principle. Instead, those universes that reproduce the quickest and the most dominate in number. We, humans, are more likely to find ourselves in a universe that is able to spawn countless copies of itself.

Why should a universe with prolific black hole production lead to life? The answer is that we are made of stardust. During the first three minutes of the Big Bang, the lightest elements of hydrogen, helium and lithium were forged. For millions of years, these were the only types of atoms in the Universe. Since life is comprised of hydrogen, carbon, oxygen and nitrogen as well as smaller amounts of other atoms, how did the heavier elements arise? The answer is at the center of stars through the nuclear processes that generate the energy that eventually produces starlight. But how did the carbon and oxygen inside a star get out? How did they arrive on planets? The answer is through the explosions of stars, or supernovas. In a supernova, a star spills its contents throughout its region of the Universe. If the contents then join a sufficiently dense gas cloud, then a collapse of material forms a star with planets. In effect, we are made of stardust.

But what do supernovas have in common with black holes? Why should a universe with prolific black hole production be more likely to produce life? The answer is that supernovas and black holes both arise from the collapse of stellar matter. In fact, many black holes emerge as remnants of supernova explosions of heavy stars. The explosions produce the carbon, oxygen and nitrogen necessary for life.

Cosmological natural selection would eliminate the need to evoke the anthropic principle, an idea that some scientists use to justify human existence. The strong form of the anthropic principle says that since life exists on Earth, the world had to be created in such a way as to allow this possibility. Few scientists like this idea; they view it as being as egocentric as Ptolemy's claim that the Earth was the center of the Universe -- why are we so special? The weak form assumes that there are many universes, a few of which have physical laws that allow life while the rest do not. We humans must live in one of these special universes. Dr. Lee Smolin would say that only one out of 10²¹⁹ universes have conditions conducive to life. Most scientists find the anthropic principle unsatisfying.

Is cosmological natural selection a theory? Yes, because it is testable. The theory predicts that Nature's parameters should be optimized for black hole production. Hence if one changes a coupling constant or a particle mass, the number of black holes should decrease. Theorists can analyze the effects of such a variation through calculations and computer simulations. Unfortunately, it is currently quite difficult to perform such an analysis because a change in a parameter affects the Universe in many disparate ways. Consider varying Newton's gravitational constant, for example. The rate of expansion of the Universe, the collapsing processes that build stars, stellar evolutions and supernova production would all change.

There are about 20 parameters that can be varied. Since each may be increased or decreased, there are about 40 tests of the cosmological natural selection principle. The chances that Smolin's theory can accidentally survive all 40 tests is 1 in 2⁴⁰ or about 1 in a trillion.

The Life of the Cosmos is well written in a highly intellectual style. For example, here are some sentences from a typical paragraph: ". . . If we were interested only in feeling better about ourselves, we might be happy to jump from vitalism to a kind of pantheism according to which life exists because the universe is itself alive. But our goal should be more than inventing a story that explains what we are doing in the universe. . . . What is needed is a deeper understanding of what both life and the universe are that allows us to comprehend why it is natural to find one inhabited by the other."

The worse thing about the book is the small font size that Oxford University Press has used. Another criticism is that The Life of the Cosmos probably should spend more time explaining physics and astrophysics. The book sometimes debates philosophical questions without providing the reader with a complete understanding of the science issues.

Who should read this book? Those with a strong interest in philosophy and some interest in science or cosmology. The reader must have a high IQ -- deep philosophical reasoning and non-trivial logical analyses are involved. The reader should not be a strong believer in God, as the book continually downplays the role of any supreme being.

In summary, it is refreshing to have a work that provokes such deep thinking on the behalf of the reader. Dr. Smolin strives to construct a self- contained theory that explains how our Universe with its very special properties arises. He moves us away from the absolute and toward the relative; away from the static and toward the dynamic; and away from reductionism and toward a global viewpoint. He aims to find a framework that can explain all: the laws of Nature, the presence of stars and planets and the existence of life. When the stakes are this big, it is easy to be wrong. Some physicists would settle for a lesser goal: discover the physical laws and simply accept them. In this form, science is a description of Nature but not an explanation of why things are. Dr. Smolin wants to take science to a new level.

The most important lesson of The Life of the Cosmos is that evolution might apply to the Universe. Although Dr. Smolin's specific proposal might not be correct, there could be other ways to realize cosmological natural selection. The general idea is thought-provoking.

Humans have an innate desire to seek out reasons for everything. They want to have the answer to any question that can be posed. However, the understanding of certain things might be beyond human intellectual capability. Some questions have no answers because the questions themselves make no sense. Why is there a Universe? Why is there an Earth? Why do we exist? Perhaps there is no answer to the question "Why?"

The Life of the Cosmos is available through the internet at Amazon.com. Click here to order. Jupiter Scientific participates in Amazon.com's Associates Program.