02 January 2004

Many Worlds Apart

contributed by Stephen D. Unwin
author of The Probability of God

Be kind to people. Don't steal from them. Be honest. The world was created six thousand years ago.

To keep me on track in pursuit of the moral life, I often sketch out the tenets of my religious beliefs. These elements seem coherent, although I admit to being a little leery about one of them. It is, of course, the one about being honest. I feel intuitively that God would want me to tell old friends they still look good after all these years. I really need to explore further the theology of honesty.

I didn't always believe all these things. Take the matter of the world's genesis, for example. In darker days, I thought of myself as a weak anthropicist. The adjective 'weak' doesn't apply to the degree of my commitment, but reflects someone's notion that the principle in which I believed - the weak anthropic principle - is a weaker variant of another form. Paradoxically, it was for me the weak version of the principle that was by far the more powerful and compelling. Attaching to it the epithet "weak", I suspect, is in the same spirit of banks and insurance companies issuing "nondisclosure statements"; that is, they are titled antithetically to content in order to allay any fuss. The strong anthropic principle has it that the universe must possess properties that ensure the emergence of observers. This idea always struck me as having unnecessarily strong teleological overtones. The weak, yet, in my opinion, more powerful version of the principle is that any observed universe must have those properties necessary to produce observers. The reason that this principle is so powerful is that it lacks any of those attributes that expose it to the possibility of being wrong. It has the incontrovertible and awesome power of tautology. Anyhow, strong or weak, the anthropic principle is often proffered as the reason that the universe is seemingly fine-tuned - that is, all the physical laws and constants of nature are calibrated just-so - to produce galaxies, stars, atomic matter, and, ultimately, life.

For the weak anthropic principle to make sense as an explanation of fine-tuning, we must accept the notion that there exist many universes, most of them untuned and lifeless, but in which the fine-tuning issue would never be raised. Yet - and here's the point - some tiny fraction of these universes; that is, those in which the laws and physical constants are just right, would be life-bearing. We could then conclude, with compelling obviousness, that we must live in one of the few that are just right for us. So, if someone marvels, somewhat parochially, that had the fundamental constants of nature been just a few percentage points different, it would have resulted in chaos and black holes instead of structure and life, then we can inform them with confidence that there are indeed plenty of universes just like that, but it isn’t our problem.

Now, some might ask if there is really any economy of belief in accepting this multitude of universes in preference to, say, the idea of a single cosmic designer who went out of his way to do all that fine-tuning? Perhaps it's just my frugal, north-of-England upbringing, but, as a general principle, I've always considered vast numbers of universes to be a rather extravagant solution to any problem. Now to be fair, one can go some way toward putting these universes on a reasonably sound physical footing. There is the so-called Everett 'many-worlds' interpretation of quantum mechanics that has the universe splitting continually as quantum mechanical wave functions collapse - where each outcome to a quantum uncertainty represents a branch in the split. On the other hand, all these branching universes are governed by the same physical laws, and so this model is of limited help with the fine-tuning question. Then again, the Everett model doesn't have the monopoly on multi-universe concepts. There's always the idea that there are multiple parallel universes with different sets of physical laws - perhaps even some without much in the way of laws at all, where a physicist would be hard-pressed to get one lousy paper out of the whole thing. Or, if arguing for the notion of 'parallel universes' makes you feel a little nerdish and Trekkie-esque, what about the idea of an ongoing cycle of big-bangs and big-crunches giving rise to serial universes? This, of course, raises the issue of geese, as I will explain.

Say I inform you of the existence of an invisible and generally undetectable goose in the middle of my desk. What’s the risk of having you falsify my assertion? I think I'm pretty safe on the science front because science is quite ill-equipped to take on this sort of pronouncement. After all, science's starting point generally involves detection and measurement, and my goose is quite immune to that type of thing. Perhaps a philosopher - one of those who deals in metaphysics - could challenge my proposition. Yet again, he or she, by profession, might be considered less credible than the goose.

Indeed, science's preoccupation with observation renders it quite impotent when it comes to denying or confirming the existence of the undetectable. So, returning to the universes: if they are in principle unobservable - which they are generally considered to be (with the possible exception of the Everett model, which wasn't of much use, anyway) - then this many-universe outlook could not really be considered a scientific one. Yet, it seems in some intuitive way to have a meta-scientific flavor to it, doesn’t it? I must confess that I'm not entirely sure why I think this. Perhaps it's that science has come to gain some foothold on the physical universe, and on geese too, for that matter. So, to posit the existence of the undetectable goose or the unobservable universes has a sciencey feel to it. This would be in contrast to, say, positing the existence of God, who could by no means be considered some variant on a scientifically concrete idea. This is the best rationale I can muster for my meta-science claim.

I admit that any one of these beliefs - in undetectable universes, invisible geese, or God - would require somewhat of a leap of faith. I suppose we must each take our own path - and the option to which I have come to attach my own faith is God. If I were pressed for some justification (notwithstanding the whole issue of explanatory economics, which might simply be a case of cheapness on my part), I think I might play the logical positivism card to argue that at least the God in which I believe is, in a way I won’t expound here, detectable.

Now, it would crush me to think that my beliefs could be construed as an affront to the faith of others. I would not wish to offend those whose faith attaches to the notion of multiple universes, nor to offend the goose cultists for that matter. I will not be accused of attacking the religions of others. I am, after all, fully aware that my belief is simply one of faith, and that the physics of the natural world provides no argument for this preference.

Be kind to people. Don't steal from them. Be honest. The world was created six thousand years ago. As I think about it more, that last thing about the world being six thousand years old could be another problem. I suspect it's probably true — raising the tougher and more pertinent question of this: true in which universe?