Chapter 8 The Deep Structure of the Universe
Chapter 8
The Deep Structure of the Universe
As we saw earlier, current thinking about the origins of the universe points to a primordial big bang, leading to the gradual emergence of the universe as we now know it.1 Yet the evolution of the universe is shaped by the fundamental constants of nature. Close examination of the cosmic narrative just outlined suggests that its shape and outcome was determined by some critically important factors. It is clear that there exist certain invariant properties of the natural world and its elementary components which make the gross size and structure of almost all its composite objects inevitable. The size of bodies such as stars and planets are neither random nor the result of any progressive selection process, but simply manifestations of the different strengths of the various forces of nature. If these were different, the universe would have taken a very different form. Human beings might not have been here. For the Christian, the universe is a creation that has been endowed by its creator with precisely those laws of nature that are necessary for it to have so fruitful a history, leading to the appearance of humanity.
Since the seventeenth century, it had been widely assumed that no special initial conditions were required for the emergence of a life-bearing universe.2 Yet in the last few decades, it has become clear that this is not the case. There has been a growing realization of the extraordinary degree of contingency of the initial conditions of the universe, if heavy elements, planets, and ultimately complex life were to develop. The life-bearing properties of the universe are highly sensitive to the values of the fundamental forces and con stants of nature. The theoretical physicist Lee Smolin points to the importance of this point in relation to the development of stars:
The existence of stars rests on several delicate balances between the different forces in nature. These require that the parameters that govern how strongly these forces act be tuned just so. In many cases, a small turn of the dial in one direction or another results in a world not only without stars, but [also] with much less structure than our universe.3
A life-bearing universe is far more constrained than had been realized. This has led many to speak of the universe being “fine-tuned” for life. The deep structure of the universe seems to have been designed to allow life to come into existence.4
The term “fine-tuning” is often used to refer to the scientific realization that the values of certain fundamental cosmological constants and the character of certain initial conditions of the universe appear to have played a decisive role in bringing about the emergence of a particular kind of universe, within which intelligent life can develop. Many recent scientific studies have emphasized the significance of certain fundamental cosmological constants which, if varied slightly, would have significant implications for the emergence of human existence.5 Examples of the astrophysical “fine-tuning” of fundamental cosmological constants include the following:
1. If the strong coupling constant were slightly smaller, hydrogen would be the only element in the universe. Since the evolution of life as we know it is fundamentally dependent on the chemical properties of carbon, that life could not have come into being without some hydrogen being converted to carbon by fusion. On the other hand, if the strong coupling constant were slightly larger (even by as much as 2 percent), the hydrogen would have been converted to helium, with the result that no long-lived stars would have been formed. Since such stars are regarded as essential to the emergence of life, such a conversion would have led to life as we know it failing to emerge.
2. If the weak fine constant were slightly smaller, no hydrogen would have formed during the early history of the universe. Consequently, no stars would have been formed. On the other hand, if it were slightly larger, supernovae would have been unable to eject the heavier elements necessary for life. In either case, life as we know it could not have emerged.
3. If the electromagnetic fine structure constant were slightly larger, the stars would not be hot enough to warm planets to a temperature sufficient to maintain life in the form in which we know it. If smaller, the stars would have burned out too quickly to allow life to evolve on these planets.
4. If the gravitational fine structure constant were slightly smaller, stars and planets would not have been able to form because they would have lacked the gravitational constraints necessary for coalescence of their constituent material. If stronger, the stars thus formed would have burned out too quickly to allow the evolution of life.
The important point to appreciate is that each of these four statements is framed counterfactually. We are asked to envisage alternative worlds in which these constants have different values, and then to compare these worlds with that which we actually know. Small variations in any of these constants would have led to very different outcomes. For a theist, the implications of such points are obvious: as the philosopher John Leslie shrewdly observes, “God would need to be careful which physics he chose.”6
We could imagine a mental experiment in which someone designs a machine that allows us to vary the values of some of the fundamental properties of the universe—such as the weak nuclear force—and see what would happen (at least theoretically) if they were significantly different from what is actually observed. The surprisingly restricted range of values that certain fundamental constants must take to bring about the universe with which we are familiar has led the physicist Paul Davies and others to speak of God as the cosmic “fine-tuner.”
Life as we know it depends very sensitively on the form of the laws of physics, and on some seemingly fortuitous accidents in the actual values that nature has chosen for various particle masses, force strengths, and so on. If we could play God, and select values for these natural quantities at whim by twiddling a set of knobs, we would find that almost all knob settings would render the universe uninhabitable. Some knobs would have to be fine-tuned to enormous precision if life is to flourish in the universe.7
Some landmarks in the development of the notion of “fine-tuning” should be noted. In 1973, Barry Collins and Steven Hawking pointed out that, out of all the possible values of the physical constants, only a relatively narrow range of initial conditions could give rise to the observed isotropy of the actual universe.8 A quite extraordinary degree of constraint would have to be imposed on the initial cosmic energy density to give rise to the universe as we know it. They found this result puzzling: accepted theories did not offer any explanation for the fact that the universe turned out this way rather than another. Collins and Hawking argue that a universe beginning with too much gravitational energy would re-collapse before it could form stars, and a universe with too little energy would not permit the gravitational condensation of galaxies and stars. Thus, out of many different possible initial values of Ω (the ratio of the actual average density of the universe to the critical density), human life could only have emerged in a universe where the initial value of Ω was almost precisely 1.
A year later, Brandon Carter published a paper in which he introduced the term “the anthropic principle,” which he stated in two forms. The weak anthropic principle holds that “what we can expect to observe must be restricted by the conditions necessary for our presence as observers.” The strong anthropic principle holds that “the universe (and hence the fundamental parameters on which it depends) must be such as to admit the creation of observers within it at some stage.”9
These speculative explorations culminated in 1986 with the publication of John Barrow and Frank Tipler’s landmark book, The Anthropic Cosmological Principle, which propelled the “anthropic principle” from the pages of obscure journals to popular culture.10 In doing so, it has raised many theological questions, including the apologetic value of the “anthropic principle.” Barrow and Tipler provide a comprehensive yet relatively accessible account of the fundamental role played by the constants of nature, and the astonishing great implications of seemingly small variations in their magnitude. The Anthropic Cosmological Principle set out the extraordinary, seemingly fortuitous coincidences that appear to have made life possible. Barrow and Tipler go on to present three possible ways of making sense of apparent “fine-tuning” of the world for biological life: the “weak,” “strong,” and “final” forms of the principle. Although each of these models was already known within the scientific community, Barrow and Tipler made them intelligible and accessible to a much wider readership. It rapidly became the “Bible of anthropic reasoning” (according to Robert Klee).
Barrow and Tipler challenge the popular secular myth that talk about “design” of the world is a recent innovation. As they rightly point out, it is one of the oldest and most fundamental questions of all, deriving its legitimacy partly from its antiquity and partly from its sheer intellectual importance. “Aristotelian science was based upon presupposition of an intelligent natural world that functions according to some deliberate design.” The English popular religious writer William Paley (1743–1805) developed the “argument from design” in some new directions in the early nineteenth century.11 This approach is now regarded as unsatisfactory. Yet Paley’s intellectual and theological misadventures, which are clearly specific to this age, cannot be allowed to negate the question of why things are the way they are—or indeed, why there is anything at all.
Barrow addresses such issues in subsequent writings, making the fair point that two quite different forms of the design argument are used by theologians and philosophers. The first is that which is encountered in the larger, biological, section of Paley’s Natural Theology, and it is based on “nice outcomes of the laws of nature.” The argument, though easily grasped, is severely vulnerable. God can easily be eliminated from the argument (a development which began long before Darwin published his theory of natural selection). In my view, it amounts to little more than deism, positing a somewhat attenuated notion of God rather than the somewhat richer Trinitarian vision of God associated with Christianity.
Barrow’s second approach is based on “nice laws.” Where do the laws of nature come from? If the universe sprang into existence in an astonishingly short time already possessing the laws that would govern its development, the question of the origin and character of those laws becomes of major apologetic importance. As Barrow rightly points out, this latter version of the design argument is much harder to explain without reference to God. After all, the laws of nature clearly did not come into being by a gradual process of cumulative selection. The universe that emerged out of the big bang, on an anthropic reading of things, was already governed by laws that were fine-tuned to encourage the rise of carbon-based life forms.
The essential point is that if the values of certain fundamental constants which govern the development of the universe had been slightly different, its evolution would have taken a different course, leading to a cosmos in which life would not have been possible.
The apparent fine-tuning of the universe has been considered in a large number of relatively accessible recent works.12 For our purposes, it is enough to note several features that illustrate this phenomenon rather than provide a more extended analysis. The debate in the literature mainly concerns the interpretation of these phenomena, whose existence is generally conceded. The essential point is that if the values of certain fundamental constants which govern the development of the universe had been slightly different, its evolution would have taken a different course, leading to a cosmos in which life would not have been possible. The element of surprise in this analysis relates to the impact on cosmic evolution of even a small variation of some of these constants.
For a recent statement regarding the importance of the fine balancing of the universe’s fundamental constants, we may turn to Sir Martin Rees, currently president of the Royal Society of London, Britain’s leading association of scientists.13 We may summarize his analysis of these constants as follows:
1. The ratio of the electromagnetic force to the force of gravity, which can also be expressed in terms of the electrical (coulomb) force between two protons divided by the gravitational force between them. This measures the strength of the electrical forces that hold atoms together, divided by the force of gravity between them. If this were slightly smaller than its observed value, “only a short-lived miniature universe could exist: no creatures could grow larger than insects, and there would be no time for biological evolution.”
2. The strong nuclear force, which defines how firmly atomic nuclei bind together. This force “controls the power from the Sun and, more sensitively, how stars transmute hydrogen into all the atoms of the periodic table.” Once more, the value of this constant turns out to be of critical importance. Even a small variation in its value would lead to the development of a universe in which we would not exist.
3. The amount of matter in the universe. The cosmic number Ω (omega) is a measure of the amount of material in our universe—such as galaxies, diffuse gas, and so-called dark matter and dark energy. Ω tells us the relative importance of gravity and expansion energy in the universe. “If this ratio were too high relative to a particular ‘critical’ value, the universe would have collapsed long ago; had it been too low, no galaxies or stars would have formed. The initial expansion speed seems to have been finely tuned.”
4. Cosmic repulsion. In 1998, cosmologists became aware of the importance of cosmic antigravity in controlling the expansion of the universe, and in particular its increasing importance as our universe becomes ever darker and emptier. “Fortunately for us (and very surprisingly to theorists), Ω is very small. Otherwise its effect would have stopped galaxies and stars from forming, and cosmic evolution would have been stifled before it could even begin.”
5. The ratio of the gravitational binding force to rest-mass energy, Q, is of fundamental importance in determining the “texture” of the universe. “If Q were smaller, the universe would be inert and structureless; if Q were much larger, it would be a violent place, in which no stars or solar systems could survive, dominated by vast black holes.”
6. The number of spatial dimensions, D, which is three. String theory argues that, of the ten or eleven original dimensions at the origins of the universe, all but three were compactified. Time, of course, is to be treated as a fourth dimension. “Life,” Rees comments, “couldn’t exist if D were two or four.”
These six points can easily be expanded to include a series of observations about the values of fundamental constants, or the initial boundary conditions of the universe. As Freeman Dyson once remarked, “The more I examine the universe and study the details of its architecture, the more evidence I find that the universe in some sense must have known that we were coming.”
So how are we to assess these new developments in cosmology, which are clearly of considerable theological significance? Though there are dissenting voices, it is widely agreed that the “new cosmology” is consonant with theism. Some would go further and argue that the phenomenon of fine-tuning gives new life to more rigorous forms of inductive or deductive argumentation for the existence of God, such as the teleological and cosmological arguments. The realization that the universe as a whole, and not simply life on earth, has a history has major implications for our understanding of the emergence of life, often ignored in biological works. For example, many accounts of biological evolution often seem to assume that it is utterly unproblematic, and perhaps even uninteresting, that the critical chemical materials required for life are present in the universe, with physical properties that facilitate both the emergence and development of living forms.
Thus the issue of fine-tuning is no longer being limited to a discussion of cosmology. Since about 1990, there has been growing awareness that other scientific disciplines are generating material that is open to a similar interpretation. In particular, there has been a growing realization of the interconnections between certain fundamental principles of biology and astrophysics. In the following chapter, we shall consider these developments before moving on to reflect more fully on their significance.