The anthropic principle revisited

This month's issue of Seed alerted me to something that I have mentioned before and think may just destroy the factual basis of the fine-tuning argument for a God's existence. Imagine that instead of arguing that the physical constants are fine-tuned so that they cannot be independently varied, we actually did a mathematical analysis of them to see how the ratios of the constants could be changed but still produce life. In a peer-reviewed article entitled, "Limitations of anthropic predictions for the cosmological constant Λ: cosmic heat death of anthropic observers", Fred C. Adams at Michigan looked at the relationships of gravity and the nuclear forces as fundamental physical constants and found that so long as these are varied together, they produce a number of star-sustaining, and therefore life-sustaining, physical universes.

In this latter case, the bounds on a Λ [the cosmological constant] can be millions of times larger than previous estimates—and the observed value. We thus conclude that anthropic reasoning has limited predictive power.

Theists often use the anthropic principle to argue in favor of an intelligent designer of the universe. Given that the idea of the argument precludes the designer being a part of the universe, this is all but arguing for the existence of God, not just some alien somewhere. The argument usually goes, "If you changed the force of gravity by even one-quadrillionth of a N, then life couldn't exist..."

You can view this sort of argument here and here by Collins. A substantive reply to Collins' argument follows:

Collins is more persuasive, although certainly not original, when trotting out the Anthropic Principle, the argument that the universe is uniquely pre-tuned to bring about life in general and human life in particular. There are a number of physical constants and laws such that if any had been even slightly different, life might well have been impossible. For example, for roughly every billion quarks and antiquarks, there is an excess of one quark – otherwise, no matter. If the rate of expansion immediately after the Big Bang had been a teeny tiny fraction smaller than it was, the universe would have recollapsed long ago. If the strong nuclear forces holding atomic nuclei together had been just a smidgeon weaker, then only hydrogen would exist; if a hair stronger, all hydrogen would promptly have become helium, and the solar furnaces inside stars –which we can thank for the heavier elements – would never have existed.

Both Dawkins and Sagan also examine this argument, which Dawkins caricatures as "god-as-dial-twiddler." It is oddly tautological, in that if the universe were not as it is, we indeed would not be here to wonder about it. In Fred Hoyle's science fiction novel, The Black Cloud, it is explained that the probability of a golf ball landing on any particular spot is exceedingly low – and yet, it has to land somewhere! The Anthropic Principle can also be "solved" by multiple universes, of which ours could simply be the one in which we exist; this might apply not only to horizontally existing multi-verses, but to the same one occurring differently in time if there have been (and will be) unending expansions and contractions. Moreover, it isn't at all clear that the various physical dials are independent, or that the physical constants in the universe could be any different, given the nature of matter and energy.

This is a typical response to the theistic position --

1) pointing out that improbable events happen all the time without being of divine origin: each seven-card hand dealt in stud poker has a probability of (1/52*1/51*1/50*1/49*1/48*1/47*1/46) = 1 in 674,274,182,400. But does that make it a miracle?
2) questioning whether the constants can be changed at all, or if they are primally fixed by the nature of the universe
3) invoking the multiverse to reduce the significance of any one universe's "uniqueness" in a statistical sense (also see here)

But from a scientist's standpoint, it's much more interesting to wonder what ratios and relationships amongst the physical constants would still produce life if they were varied interdependently. And that's the question that has been answered by Fred Adams. There are many configurations of the constants that, when varied together, still produce life-friendly, or "Goldilocks"-zone universes. This makes the anthropic principle much less interesting. Yet another reason to give up on the idea of a God.