04 September 2010

Modern cosmology and the rediscovery of purpose?

5.20 Some contemporary cosmological enigmas

Modern cosmology offers us mathematical models of the possible large-scale structure of the universe. Like any other mathematical model, the actual features depend on the numbers that we choose to put in the equations. Thus in 5.17 we noted that different values of the total mass of the universe will give rise to very different cosmological models. In general, the overall structure of many physical systems is strongly influenced by the numerical values of a relatively small number of universal constants (e.g. the gravitational constant). Since the 1970s physicists have become increasingly aware that the physical conditions that enable life to exist are very sensitive to the values of a number of these constants. If they had been only slightly different, life as we know it could not have evolved.

5.20.1 The chemical composition of the universe

As we noted in 5.16.1, the overall chemical composition of the universe was determined by physical conditions during the first seconds of the Big Bang. However, the elements on which life depends (such as carbon, nitrogen, oxygen, sulphur and iron) are the product of nuclear reactions within stars. In both situations the processes by which the chemical elements are formed are governed very precisely by the strengths of four fundamental physical interactions: gravitation, electromagnetism, and the weak and strong nuclear interactions.

If the relative strengths of these forces were different, the resultant universe would also be different. For example, increasing the strong nuclear interaction by 3 per cent relative to the electromagnetic interaction gives a cosmological model in which none of the known chemical elements could form. Conversely, decreasing it by 1 per cent gives a model in which carbon atoms would be unstable. Both scenarios would preclude carbon-based life. Other tiny variations in these forces might have given rise to a universe which was 100 per cent helium or one in which supernova explosions could not occur (since these explosions are thought to be the chief way in which the chemicals necessary for life are ejected from stars, this too would preclude the evolution of life).

5.20.2 ‘Anthropic’ features

The actual chemical composition of the universe is just one way in which the universe appears to have been finely tuned to permit the evolution of life. Until their explanation by inflationary cosmology (5.19), the horizon and fine-tuning problems were also seen in this light by many physicists, and there are still elements within inflation which look fine-tuned (Craig, 2003:158-61)  The various unexplained factors that have been perceived as necessary for the emergence of life have come to be known as ‘anthropic’ features (or coincidences).

5.21 Possible responses to the ‘anthropic’ coincidences

There is no obvious physical reason why the parameters mentioned in 5.20.1 should have the observed values. However, very small changes in any of these key parameters would have resulted in a grossly different universe; one in which life as we know it would almost certainly be precluded. The set of life-permitting cosmological models is a vanishingly small subset of the set of all theoretically possible cosmological models. How should the scientist-theologian respond? Murphy and Ellis provide a list of possibilities (1996:49-59).

One response to these enigmas might be to adopt a hard-nosed empiricism and say, ‘So what? It is meaningless to speak of our existence as improbable after the event.’ However, few cosmologists seem prepared to ignore these cosmological coincidences in this fashion.

Another possible response would be to deny the contingency of physical laws and parameters. For example, some physicists speculate about possible developments in physics that would demonstrate that only this precise set of laws and parameters is possible. This is the approach that leads Drees to be cautious about drawing any inferences from the coincidences (1996:269-72).

An important further caution is provided by philosophers who question whether we can really apply the formal measure of probability to a range of possibilities about the universe of which we know so little (see Manson, 2000, McGrew et al., 2003). Nevertheless, however, vaguely defined, the coincidences remain striking and seem to call for some explanation.

A third type of response is to invoke some form of anthropic ‘principle’.

5.22 The Weak Anthropic Principle

The approach which does the least violence to conventional modes of scientific thought is to invoke a Weak Anthropic Principle (WAP). Barrow and Tipler describe it thus:
The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirement that the Universe be old enough for it to have already done so. (Barrow and Tipler, 1986:16)
In other words, our existence as observers functions as a cosmological selection effect. There can be no observations without observers. Our observations must satisfy the conditions necessary for our existence.

However, the WAP does not take us very far towards an explanation of the observed coincidences. In conjunction with a conventional Big Bang cosmology, it still gives the impression that our existence is an accident of vanishingly small probability. Thus, in practice, it usually appears in conjunction with a cosmological model that suggests that there is a sense in which all possible universes actually exist. Three such strategies are to be found in the literature.

The first is to extend the closed Big Bang model to permit an endless series of expansions and contractions: the so-called cyclic Big Bang (see 5.18). Each passage through a singularity is supposed to randomise the physical parameters that give rise to the anthropic features. Advocates of this approach argue that in an infinite series of closed universes there will certainly be a subset whose physical features permit the evolution of life and the function of the WAP is to remind us that only in such an atypical subclass of universes could life evolve. The main difficulty faced by this scenario is justifying the assumption that, while the singularity randomises the laws and constants of nature, it leaves the geometry of spacetime untouched. If, as seems reasonable, passage through a singularity also affects the geometry of the universe, we should expect an open Big Bang after a finite number of cycles, thus putting an end to any hope of an infinite sequence of universes.

A second approach would be to opt for Linde’s version of inflationary cosmology (see 5.19). In an infinite chaotic universe in which an infinite number of ‘bubble’ universes are created by the decay of the false vacuum, we should expect every possible stable state to appear an infinite number of times. Again the WAP is a reminder of the atypical nature of the universe in which we find ourselves.

The third and, currently, most popular strategy for relaxing the uniqueness of our universe is to adopt a many‑worlds interpretation of quantum mechanics [5.13 (iii)]. Again it is sufficient to invoke the WAP to ‘explain’ our atypical cosmos.

5.23 The Strong Anthropic Principle

For some cosmologists the WAP does not go far enough. Their response is to invoke the existence of rational carbon-based life forms as an explanation of the anthropic features of the universe. Barrow and Tipler formulate a general version of the Strong Anthropic Principle (SAP) thus: ‘The Universe must have those properties which allow life to develop within it at some stage in its history’ (Barrow and Tipler, 1986:21).

            One version of the SAP is Wheeler’s Participatory Anthropic Principle (PAP). This asserts that the existence of the cosmos and the detailed course of its evolution are dependent on the existence of rational observers at some epoch. In his own words, ‘Observership is a prerequisite of genesis’ (Wheeler, 1977:7). It is essentially an extension of his own particular interpretation of quantum mechanics (see 5.13(i)). All properties, including the very existence of the universe, are brought about by the inter-subjective agreement of observers. Thus the universe may be likened to a self‑excited circuit. Past and future events are so coupled as to obviate any need for a first cause.

Against the PAP, Barrow and Tipler point out that the capacity of human observers to ‘create’ in this way is very limited indeed (Barrow and Tipler, 1986:470). Thus the PAP seems to entail the present or future existence of a community of beings with a ‘higher degree of consciousness’ than our own. They suggest that the process by which the appropriate kind of inter-subjective agreement is reached is the sequential coordination of separate sequences of observations, ‘until all sequences of observations by all observers of all intelligent species that have ever existed and ever will exist, of all events that have ever occurred and will ever occur are finally joined together by the Final Observation by the Ultimate Observer’ (Barrow & Tipler, 1986:471). The theistic implications of such a statement are obvious.[1] However, Barrow and Tipler avoid such a theistic conclusion by modifying the PAP into their Final Anthropic Principle (FAP). They state the FAP in the following terms: ‘Intelligent information-processing must come into existence in the Universe, and, once it comes into existence, it will never die out’ (Barrow and Tipler, 1986:23). In other words, intelligent life-forms have cosmological significance by virtue of their future capacity to understand and manipulate matter on a cosmic scale.

This belief leads them to develop a non-theistic ‘physical eschatology’. Tipler has amplified this further in his The Physics of Immortality (1995).[2] Humankind may not exist forever but human culture will persist, being preserved and developed by self-replicating intelligent machines. The transfer of our cultural software to alternative forms of hardware is one factor in encouraging the indefinite growth of the capacity to process information and to manipulate matter. They envisage the inevitable expansion of human culture to the point where it engulfs the entire cosmos. But let them have the final word:
if life evolves in all of the many universes in a quantum cosmology, and if life continues to exist in all of these universes, then all of these universes, which include all possible histories among them, will approach the Omega Point. At the instant the Omega Point is reached, life will have gained control of all matter and forces not only in a single universe, but in all universes whose existence is logically possible; life will have spread into all spatial regions in all universes which could logically exist, and will have stored an infinite amount of information, including all bits of knowledge which it is logically possible to know. And this is the end. (Barrow and Tipler, 1986:676f.)
And, in a footnote, they add, ‘A modern-day theologian might wish to say that the totality of life at the Omega Point is omnipotent, omnipresent, and omniscient!’ (Barrow and Tipler, 1986:682 note 123).

In spite of the metaphysical tone of much of their discussion, Barrow and Tipler stress that the FAP makes clear predictions about the kind of universe we can expect to observe. Most importantly, they argue that, in order for life literally to engulf the universe, the universe must be closed. It must eventually begin to collapse under its own gravitation toward a final singularity.

5.23.1 Is it science?

Implicit in Barrow and Tipler’s insistence on the predictive power of the Anthropic Principles is a claim that they be accorded scientific status. Predictive capacity is a keystone of Popper’s well-known Criterion of Falsifiability. But what sort of scientific status is being claimed?

The SAP claims that the statement, ‘Observers exist’, in some sense constitutes a scientific explanation of the anthropic features of the cosmos. Two ways of interpreting this are possible.

It may be a claim that rational observers are the efficient cause of the universe. However, this would imply that time reversal is a reality on a cosmic scale and that in a very strong sense intelligent observers have (will have?) created their own reality.

Alternatively, the SAP may be read as a denial of the sufficiency of efficient causes as scientific explanations of certain physical problems. This implication of the SAP has caused some scientists and philosophers to reject it out of hand. However, it should be recalled that it was only with the rise of the mechanical model of the world that efficient causes were accepted as complete explanations in physics. Furthermore, the biological sciences have proved remarkably resistant to this view of scientific explanation.

By contrast, the WAP does not claim to be explanatory: it is merely a selection effect. However, like the SAP, it has a covert content. It is pointless unless it is used in conjunction with a cosmological model which postulates an ensemble of universes. Thus it functions as a way of commending to the scientific establishment certain speculative cosmologies which have so far failed to convince when restricted to more conventional forms of scientific argumentation.

5.24 Anthropic design arguments

It is hard to resist the impression of something – some influence capable of transcending spacetime and the confinement of relativistic causality – possessing an overview of the entire cosmos at the instant of its creation, and manipulating all the causally disconnected parts to go bang with almost exactly the same vigour at the same time, and yet not so exactly co-ordinated as to preclude the small scale, slight irregularities that eventually formed the galaxies, and us. (Davies, 1982:95)[3]
As this quotation from Paul Davies suggests, the apparent fine-tuning of the cosmos is a rich source of material for new forms of design argument for the existence of God. Several such design arguments appear in recent theological (and scientific) literature.

Anthropic design arguments use aspects of cosmic fine-tuning as evidence that the universe was designed to permit (or, in stronger forms, to necessitate) the evolution of rational carbon-based life forms. There can be little doubt that, from the perspective of Christian faith, such features are suggestive of design. However, design arguments based on these features make certain assumptions that may make one cautious about placing too much reliance on them.

To begin with, they assume that the anthropic features of the cosmos are, in themselves, improbable. However, quite apart from the difficulties of assigning probabilities to these parameters, such an assumption is far from proven. As we noted earlier (5.21), it is conceivable that future developments in physics might render these very features quasi-necessary. In such a situation, this entire class of design argument would collapse. There is a hint of the God of the gaps about such arguments:[4] the universe appears to be a highly improbable structure: we cannot give a rational explanation of these cosmological features: therefore, they constitute evidence of an intelligent designer. And, like the God of the gaps, the role of this deity shrinks with the expansion of scientific understanding. This shrinkage is illustrated neatly by the above quotation from Davies, which refers to the horizon problem now explained by inflationary cosmology.

A second assumption of anthropic design arguments is that the ultimate goal of creation is the existence of rational carbon-based life forms (i.e. humankind). This is in agreement with the dominant view of Western Christian theology. However, it is arguable that the anthropocentricity of western Christianity is derived from sources other than the Christian revelation. For example, instead of presenting humankind as the end of creation, Genesis 1 may be read as insisting that the end of God’s creative activity is his Sabbath rest in the presence of all his creation. A move towards less anthropocentric readings of the Bible (and Christian tradition) is a common feature of contemporary theologies of creation (see Chapter 6). This change of emphasis involves rethinking these arguments and recognising that ‘anthropic’ is an unfortunate term. What is remarkable is that the universe arose in a way fruitful for the formation of carbon-based life. Conditions permitting the simplest colonies of bacteria to arise would still be extremely remarkable.

As we discuss in 10.14-10.15, it is important to distinguish arguments about the initial character of the universe, the ‘settings of the dials’, from arguments about how it happened that, roughly ten billion years later, there arose a ‘Goldilocks planet’ like Earth, a rocky planet at the appropriate sort of distance from the appropriate sort of star to allow life to arise. Anthropic arguments as they are usually understood apply to discussion of the initial ‘settings’ of the universe. The major positions at present are:

a) versions of the many-universes position combined with the WAP (5.22)
b) the fine-tuning of the universe attributed to some sort of designer entity.

The choice between these options will tend to be motivated by metaphysical presuppositions about the coherence of design arguments (see Polkinghorne 1998b:18-22).

[1] Barrow & Tipler see analogies between this Ultimate Observer and the God of Berkeleian idealism. An alternative analogy would be with the self-surpassing deity of process thought.
[2] See also 7.7.
[3] At the same time an inference to the existence of ‘some influence capable of transcending spacetime and the confinement of relativistic causality’ is very far from being an inference to belief in any established religion.
[4] See 10.3 for more on ‘the God of the gaps’.

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