Possible Responses to Coincidences

The modern approach to the issues that used to be the raw material of Design Arguments is characterized by the cosmological approach to anthropic coincidences. We know that there are many aspects of the Universes global and local structure, and of its laws and other defining constants, which appear crucial for the existence of life as we know it. Rather than try to use this state of affairs to produce a modern version of the Design Argument, we ask the anthropic question: what are the necessary conditions for the existence and persistence of complexity (life) in a Universe? The absence of a real definition of life prevents us being more specific, but the relaxation to complexity allows us to avoid being rigidly anthropocentric. We would like to know how special these necessary conditions are in some space of possibilities. If, as is increasingly seen to be the case, there are aspects of the early evolution of the Universe which introduce random variations in the structure of the Universe (for example, to the distribution of matter density, temperature, matter-antimatter balance, cosmological expansion rate, etc) or to the quantities that we call constants of physics through symmetry breakings or quantum gravitational corrections, then we must introduce the anthropic question in order that we evaluate the relevant probabilities when asking how likely it is that the Universe possesses some particular property. At present we believe that Nature is pointing us towards a description of her laws which are far more unified and economical in their schema than we have so far been able to see. At present we are able to contemplate the consequences of altering the values of different fundamental constants of physics or aspects of the Universes large scale structure independently. One suspects that in the future these different defining features of the Universal laws will turn out to be linked together and there will be very few (perhaps only one, or zero??) independent changes that are self-consistently possible.

The chaotic and eternal inflationary universes mean that we must take seriously the possibility that the global structure of the Universe displays significant variations. The different self-reproducing regions of the chaotic and eternal inflationary universe pictures should display different densities and fluctuation levels. In some versions they will display different fundamental physical constants and even different numbers of large dimensions of space. Subsequently, the symmetry breakings that occur at phase transitions during the early history of the universe can introduce further random variation in cosmological quantities like the matter-antimatter asymmetry. With regard to the existence of apparent coincidences between the values of constants of physics and the large scale structure of the Universe which make our existence possible, we have several options. We can shrug our shoulders and say there is one and only one possible universe it is just good luck that we are here. This option includes the traditional teleological interpretations which appeal to theistic design.

A second option is that some (unknown) physical process creates the fine tunings. That is, they are not disconnected. Attempts to provide partial explanations of this sort can be found in the speculations of Edward Harrison and Lee Smolin. Theories of this sort need to harness the possibility of producing sequences of universes, in the way suggested by eternal inflation, in order to create an population of possible universes upon which some selection process can operate. In Harrison’s case that selection process is artificial selection imposed by intelligent beings who are aware of the need for certain structural properties of the universe to be tuned from cycle to cycle in order to optimise the conditions for the subsequent evolution of life. In Smolin’s case the selection is for the maximal production of black holes. Both scenarios have their problems. Harrison’s has to get going in the first place. Smolin’s is undermined by the fact that there appear to be small changes (like those that lead to the binding of the diproton) that will increase the black hole production. Also the values of the constants that maximise black hole production may not allow life to exist. Moreover, such maxima may not exist for all conceivable variations of the constants (especially for the variation of G).

A third option is that all possibilities exist, either in some quantum cosmological ensemble or actually in an infinite space and time of the sort suggested by the chaotic and eternally inflating universes. In this case the anthropic coincidences just tell us something about the size of the region of life-supporting universes in the collection of all possibilities. In this picture life evolves in some (or even all) of the places where it is possible for it to do so no matter how improbable that sequence of events might be. A problem with this perspective is knowing how large to make the ensemble of variations. It could include structural properties of the universe and its constants, but it might also include the underlying mathematical and logical structures upon which our description of it is based.

A fourth possibility is that life is a good deal easier to evolve than we have concluded from the particular situation that is on view to us. It may be that there are many other routes to biological complexity which would also be possible if the constants and laws of physics were markedly different. In this case the fine tunings that we see are illusory, a consequence of our limited understanding of life and the conditions required for its emergence. These four options alone show how difficult it is to draw firm theological or philosophical conclusions about any aspect of the Universe from cosmology. The four options we have listed, like that of teleological Design,are all consistent with the evidence.

Acknowledgements

The author was supported by a PPARC Senior Fellowship.

Contributed by: Dr. John Barrow