The Weak Anthropic Principle has been offered as a rebuttal to the astonishing level of fine-tuning we find in the physical forces, constants, and parameters of the universe. These are calibrated to such fine tolerances that had they deviated from their actual value by as little, in some cases, as 1 part in 10^120 the universe never would have formed and/or life would have been impossible. Robin Collins, author of one of the most notable and accessible arguments for theism based on cosmic fine-tuning, lists the following among the dozens of examples he could have mentioned:
1. If the initial explosion of the big bang had differed in strength by as little as 1 part in 1060, the universe would have either quickly collapsed back on itself, or expanded too rapidly for stars to form. In either case, life would be impossible. [See Davies, 1982, pp. 90-91. (As John Jefferson Davis points out (p. 140), an accuracy of one part in 10^60 can be compared to firing a bullet at a one-inch target on the other side of the observable universe, twenty billion light years away, and hitting the target.)
2. Calculations indicate that if the strong nuclear force, the force that binds protons and neutrons together in an atom, had been stronger or weaker by as little as 5%, life would be impossible.
3. Calculations by Brandon Carter show that if gravity had been stronger or weaker by 1 part in 10 to the 40th power, then life-sustaining stars like the sun could not exist. This would most likely make life impossible.
4. If the neutron were not about 1.001 times the mass of the proton, all protons would have decayed into neutrons or all neutrons would have decayed into protons, and thus life would not be possible.
5. If the electromagnetic force were slightly stronger or weaker, life would be impossible, for a variety of different reasons.
Imaginatively, one could think of each instance of fine-tuning as a radio dial: unless all the dials are set exactly right, life would be impossible. Or, one could think of the initial conditions of the universe and the fundamental parameters of physics as a dart board that fills the whole galaxy, and the conditions necessary for life to exist as a small one-foot wide target: unless the dart hits the target, life would be impossible. The fact that the dials are perfectly set, or the dart has hit the target, strongly suggests that someone set the dials or aimed the dart, for it seems enormously improbable that such a coincidence could have happened by chance.
The response made by some has been that we shouldn't be surprised that the universe is as precisely calibrated as it is for if it weren't we wouldn't be around to notice. The universe would never have formed or wouldn't be able to sustain life. It has to be the way it is in order for us to exist at all.
Stephen Hawking offers an example of the response to this cosmic precision that Collins is talking about: "Why," he asks, "is the universe the way we see it? The answer is simple: If it had been different, we would not be here."
What are we to make of such a reply?
Imagine that you have just learned that a complete novice at chess had just won the world championship. As a chess fan you're incredulous and you express your amazement that a rank beginner had beaten all of the world's best players. Suppose you were then admonished that you shouldn't be surprised, really, because, after all, if he hadn't beaten the best players he wouldn't be the world champion.
Wouldn't you think this response somewhat misses the point? The question that screams for an answer is not whether this tyro beat the world's best, we know he must have, but rather how did such a prodigy occur? Was there an illicit design or plot to have these grandmasters lose to the amateur?
Whatever the alternatives wouldn't you be inclined to think that the least plausible explanation was that it was just some sort of freakish coincidence? Yet those who invoke the weak anthropic principle are giving a response to cosmic fine-tuning analogous to those who tell us we shouldn't think there was some sort of thought-out plot behind the beginner's victory at the chess tournament.
We know we're here, and of course we know that the universe, therefore, has to be the way it is. The question is how did such a miracle happen? Was it a result of intention or was it just a happy accident? In terms of plausibility there's no contest between the hypothesis that the universe is intelligently designed and the hypothesis that the universe is the way it is because of serendipity.
Indeed, it's the need to explain this extraordinary fine-tuning that leads many skeptics to embrace the multiverse theory, about which we'll have more to say tomorrow.
RLC