Fine-tuning Arguments

So far I have considered only what the reason could be for the existence of any universe at all. Refusing to look for a reason is giving up on the basic principle of all science—always seek a reason for everything. But that means you are looking for a self-explanatory Being that explains why everything, including itself, exists. Some philosophers reject the possibility of such a Being and say that we ultimately just have to accept that we cannot explain absolutely everything.

Some pure mathematicians, however, have suggested that the idea of a self-explanatory Being is coherent and that the set of all possible mathematical truths may be said to constitute such a being. Here we would have an uncausable, eternal, changeless reality, to the existence of which there is simply no alternative. Mathematicians do not usually think of this as God, but that may be because they are thinking of God as a rather arbitrary person who is not very reasonable at all. However, if you think of God—as Anselm and Aquinas, Leibniz and Hegel did—as a rational Mind with the creative power to actualize possible mathematical structures for the sake of consciously appreciable values, the postulate of God, as an ultimate reason for the existence of one or more universes, becomes both rational and plausible. If we turn to consider the nature of our universe in particular, the amazing fact is that this universe does possess a deep structure that seems supremely beautiful and intelligible—just what the hypothesis of God would imply.

In recent years, many cosmologists have pointed out further features of this universe that seem to make it particularly improbable that it should exist by chance. In 1974, Brandon Carter proposed the anthropic principle, stating that "our location in the universe is necessarily privileged to the extent of being compatible with our existence as observers" (291). Given that carbon-based intelligent life exists in this universe, the fundamental physical and cosmological quantities of the universe must be compatible with this fact. That may seem trivially true, but it assumes that we have come into existence in accordance with a set of general laws, and it suggests an incredibly precise set of values those laws need to follow in order to have produced us.

The anthropic principle in this "weak" form produces some surprising results. For instance, it explains why there is so much empty space by showing that an expanding universe with an upper bound on the rate of expansion would have to be just as large as it is, in order to have had the time for stars to form, explode, and seed planets with carbon. The laws of fundamental physics give a time span of about thirteen billion years for that process, and so the universe would have to be about thirteen billion light years in size. There has to be as much intergalactic space as there is in order for us to have come into existence in accordance with the general laws of physics.

The anthropic principle throws up many other curious correspondences that turn out to be necessary conditions of human existence, given that our existence is generated by the operation of basic laws and constants of physics. A very large set of quantities that need to be exactly what they are to produce intelligent life has been identified. They are usually referred to as "fine-tuned" values, since they need to be very precisely coordinated, just as old-fashioned radios used to have to be finely tuned by hand to get just the right wavelength for the desired program. The slightest deviation in the gravitational constant, for example, would result in the universe's being unable to produce the relatively stable atomic structures that are necessary for life to evolve.

Robin Collins presents what he calls "six solid cases of fine-tuning" in his paper "The Evidence for Fine-Tuning" (2003). First, the cosmological constant is a term in Einstein's equation that, if positive, leads the universe to expand and, if negative, leads it to contract. The existence of life requires this constant soon after the big bang to settle on a quantity very near zero and to be so precisely adjusted within a large range of possible values that it has to be fine-tuned to at least one part in 1053.

Second, the strong force that binds neutrons and protons together in the nucleus of atoms also has to be precisely what it is in order to overcome the repulsion between the protons in the nucleus.

Third, the production of elements necessary for life requires an abundance of carbon and oxygen, but that requires a fairly precise adjustment of the strong nuclear force.

Fourth, the mass of protons and neutrons needs to be so adjusted that, if the mass of the neutron were increased by one part in seven hundred, then the formation of helium in stars could not occur.

Fifth, if the weak force were weaker than it is, stars would be composed almost entirely of helium, which is quick burning and would not allow time for life to develop on planets.

Sixth, gravitational forces need to be very close to what they are to enable atomic and planetary systems to form stable complexes. If the force of gravity were even slightly stronger, all stars would be blue giants; if even slightly weaker, all would be red dwarfs; in neither case could life have developed.

These are just six examples selected by Collins from a much larger set that can be found detailed, for example, in Michael Denton's Nature's

Destiny (1998). Modern physics has a quite new understanding of how precisely the various forces of nature need to be adjusted in order for a life-bearing universe to exist.

Stephen Hawking (1996) points out that the existence of life also seems to depend precisely upon the rate at which the universe is expanding. He suggests that a reduction in the rate of expansion by one part in 1,012 at the time when the temperature of the universe was 1010 K would have resulted in the universe's starting to recollapse when its radius was only 1/3,000 of the present value and the temperature was still 10,000 K.

Hawking concludes that life is possible only because the universe is expanding at just the rate required to avoid recollapse. In fact the balance between the force of expansion and of gravitational contraction would have prohibited a deviation in their ratio from unity by one part in 1060.

But what is the significance of these insights? Some physicists, notably Steven Weinberg (1999) and Alan Guth (1997), are unimpressed. Others—Paul Davies (1982), John Barrow and Frank Tipler (1986), and Martin Rees (2001)—seem to be impressed. The unimpressed say that, of course, these forces need to be finely correlated to produce life, but since every possible universe is a priori equally improbable, this one is no more improbable than any other. It is hardly surprising that we find its conditions are just right for life because, after all, we are alive. While it is interesting to discover the complex set of correlations that are needed to produce life, this has no implication that anyone has planned things that way. If the forces had been even slightly different, we would not have been here, and no one would have been any the wiser. Fine-tuning is irrelevant to the existence of a designing God.

Those who are impressed, however, say, as Martin Rees does, "We should surely probe deeper, and ask why a unique recipe for the physical world should permit consequences as interesting as those we see around us" (2001, 163). Interesting consequences—that is the factor that makes all the difference. It is not just that this universe is very improbable. It is not even that human beings as a species are very important. It is that the existence of the kinds of intelligence, beauty, creativity, compassion, and friendship of which we are aware represent great values that could not have existed in the way they do in any other possible universe.

What fine-tuning arguments show is that states of great value have resulted from, and could only have resulted from, a set of laws that are precisely adjusted in a large number of unexpected and exceedingly improbable ways. When he introduced the weak anthropic principle, Brandon Carter also suggested a "strong" anthropic principle, which can be stated as follows: "the universe must have those properties which allow life to develop within it at some stage in its history." It is given this formulation in Barrow and Tipler (1986, 21). For many scientists, that is a step too far, and it suggests something very like a teleological explanation for the universe.

Unfortunately, Carter's formulation of the strong anthropic principle is ambiguous. It could mean merely that, given the existence of life, the universe must have the specific properties it has. But it could also be taken to mean that the fundamental laws of nature are as they are because the universe is and must be fitted for the generation of intelligent life.

The strong principle, unlike the weak principle, is controversial, and there is no compelling scientific reason to accept it. But it shows how natural and plausible it is, in the light of modern science, to see the universe as fine-tuned to generate intelligent life. The fact that the evolution of life generates brains from single-celled organisms and the amazingly intricate ordering of DNA into a complex and reproducible coding for the building of organisms strengthens the case for seeing purpose and direction in the basic structures of nature. It looks as though the whole process has been designed to produce the values that intelligent life make possible. And it looks as though those values could only be what they are because the process as a whole is what it is.

 
< Prev   CONTENTS   Next >