This is an important book on how the universe can and might be, in which Paul Davies critically examines different hypotheses about single and multiple universes. His book illuminates the most critical issues of physics and philosophy (and of some biology) underlying our understanding of Science and Religion. He has called himself an agnostic, and he does not argue for religious beliefs. This newest book by Davies is somewhat more technical than his other books but is still well within the general readership level.
Davies updates and expands upon all previous overviews I know of in the ways the universe can begin and remain in existence, enriching previous accounts especially in his discussion of multiple universes. Also particularly fascinating is his discussion of dark mass and dark energy, which constitute 96% of our (potentially) observable universe and which we cannot see and about which we can make only indirect observations.
Throughout the book, Davies flags the free parameters, or "constants of nature", some 20 of them counting force coupling constants and the masses of elementary particles, which, in the standard models of nuclear physics, astrophysics and cosmology, must be exquisitely fine-tuned to yield a single universe capable of supporting life. As an alternative to this fine-tuning, physicists have proposed multiple universes, or a multiverse, wherein infinite universes, a few of them with properties supporting life, could counterbalance the infinitesimal probability of the degree of fine-tuning necessary in a single universe if it occurred only by chance. The difference between these views has obvious and profound metaphysical and religious implications.
Beginning about two-thirds through the book, Davies describes the possibilities afforded, in principle, by string theory/superstring theory/M-theory to bring about a multiverse. Unfortunately, that is the problem with the current state of string/M theory. It is a mathematical construct wherein physical theories might be "accommodated" - it can in principle provide a way to make predictions for those theories - but so far it cannot predict anything real, anything that has been or could be measured. And right now the odds are about even and rapidly getting longer that it ever will.
However, if a multiverse can, in principle, be supported, or dignified, by string/M-theory, we have a science-fiction writer's paradise. Davies spells out some of these wild possibilities - wild because there would be infinite possibilities, including infinite variations of the laws of physics among different universes - and he describes some that might be more likely from probability arguments. (I cannot do justice to that exciting ride without quoting his whole discussion. But, mind you, Davies does not do this in any lighthearted way; he is deadly serious in scientifically examining these possibilities.) One of the inevitable possibilities is that some universes are but computer simulations by some superculture out there in another universe. And the show-stopper in that scenario is that our own universe, including our very selves, is most probably a simulation (imagine an incredibly advanced virtual reality emulation of everything, even our consciousness). In the multiverse picture, the universe we perceive, and any God we worship, are fakes!
Every philosopher's wildest dreams can and will come true with infinite possibilities in infinite universes. This multiverse thing is annoying, isn't it? Even Davies was annoyed, as he indicates in the book, when in 2003 he published an article in the New York Times which pointed out that the threat of fake universes constituted a reductio ad absurdum of the entire multiverse idea.
In a recent note(1) Davies concluded that there were three alternatives, and he explains this more thoroughly in the book. Namely, the argument leading from the laws of physics we know - to multiple universes with fake physics - to anthropic selection - to the elimination of God is a contradictory loop; and the multiverse advocates are thus "hoist by their own petard!". However, Davies admits (p.189) that there is still some wiggle-room; and for the remainder of the book he takes the standard position that The Two Explanations for why our universe is so unexpectedly suited for life must come down to either (1) fine-tuning (which Davies terms a "fluke") or (2) a multiverse. Davies, the agnostic, then devotes the next-to-last chapter to what he terms a "third [option], ...favored by many nonscientists, ...[a universe] that has been designed...by an intelligent creator."
To my disappointment, Davies begins his next-to-last chapter with a biological discussion of "The Intelligent Design Movement in the United States", which is equated with anti-Darwinism. I would strongly suggest that the book "The Language of God" by Francis S. Collins(2) be substituted for Davies' attempts here. But then Davies moves quickly on to his more comfortable ground of physics. While concluding that belief in a God who makes the laws of physics, who is responsible for the universe and for continually holding it into existence without tinkering with its day-to-day operation, is popular with many scientists as well as theologians, Davies is uncomfortable with this as its being, in his view, an hoc explanation that leads us "no further forward" (no further forward to a purely scientific explanation). He then goes on to ask many questions couched within physics, that, for me, are not the dilemmas an agnostic or atheist faces, e.g., "who created the creator?". The agnostic constraints Davies imposes on himself in this chapter seem to go beyond an evenhandedness in treating belief and non-belief in God. Perhaps the alternative and stronger definition of an agnostic applies to Davies (a person who holds the view that any ultimate reality, as is God, is unknown and probably unknowable). In summarizing this chapter, Davies writes: "Unless everything that can exist does exist, something still unexplained must separate what exists and what doesn't" and "We are not finished yet!"
Davies' last chapter titled "How come Existence?" begins with his quoting the somewhat opposing views of several well-known physicists, e.g., of these two atheists: Stephen Hawking said "The human race is just a chemical scum on a moderate-sized planet" and Freeman Dyson said "As we look out into the universe and identify the many accidents of physics and astronomy that have worked together for our benefit, it almost seems as if the universe must in some sense have known we were coming." Davies then discusses the Two Explanations in terms of the Anthropic Principle: (1) a passive selection mechanism in a multiverse (the Weak Anthropic Principle) or (2) the laws of physics and evolution of the universe being fine-tuned to bring forth life and the human mind (the Strong Anthropic Principle). Davies then addresses whether life should, in the first place, be considered a fundamental or accidental phenomenon. After some very elegant discussion, he concludes from both scientific and philosophical considerations that life, and mind in particular, is a unique, extremely important and fundamental phenomenon of nature. Further, he considers that the connection between (1) life and mind and (2) the cosmos must be deeper than that from just "the crude lottery of multiverse cosmology combined with the Weak Anthropic Principle." Then he says much about teleology and Platonism in physics, which is important but not necessary to comment upon here, and then goes on to the "delayed choice" experiments of quantum mechanics and Wheeler's "Participatory Principle". Davies' bottom line is that neither of The Two Explanations, the universe fine-tuned for life (which Davies calls a "fluke") or the multiverse picture, can scientifically answer the ultimate question of existence because they both require a (scientifically) unexplained starting point. Lastly, Davies considers briefly a self-engineered, self-aware universe perhaps brought about through quantum backward-causation, such as causal loops and wormholes, but concludes a missing ingredient would be self-awareness. (I must note that that notions of traveling backwards in time to change the future were, in my view, forever put to rest by simple, non-quantum arguments from spacetime properties.(3) ) Davies ends the chapter by discussing the outstanding questions that prevent us from fully explaining, scientifically, the mystery of existence.
N.B. One short section titled "Afterword: Ultimate Explanations" is included at the end of the book and is extremely useful. Here, Davies gives a brief summary description of seven, as it turns out, classes of universes that embody the various attributes and their interpretations discussed throughout the book, thus collecting in one place each of their achievements in explaining things and their failures to do so. After reading the book, one can then use this splendid synopsis as a quick reference to what all currently envisioned universes can, might, and cannot be like, presented in a mere eight pages. (However, if you cheat and start reading back there first, you won't understand it.) At the end of this Afterword, Davies indicates which two of the seven types of universes he thinks might have the best chance of being true; but I won't spoil the book for you by revealing these. However, I will say that, not surprisingly, these two do not include the simplest, most straightforward one, since that one references a God, which is considered by Davies to be too "ad hoc".
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