Accounting for Fine-Tuning

A physicist at MIT named Alan Lightman, in the course of reviewing a book on science, religion and atheism, discusses the significance of cosmic fine-tuning. He writes:

There is one scientific conundrum that practically screams out the limitations of both science and religion. And that is the “fine tuning” problem. For the past 50 years or so, physicists have become more and more aware that various fundamental parameters of our universe appear to be fine-tuned to allow the emergence of life — not only life as we know it but life of any kind.

For example, if the nuclear force were slightly stronger than it is, then all of the hydrogen atoms in the infant universe would have fused with other hydrogen atoms to make helium, and there would be no hydrogen left. No hydrogen means no water. On the other hand, if the nuclear force were substantially weaker than it is, then the complex atoms needed for biology could not hold together.

In another, even more striking example, if the cosmic “dark energy” discovered 15 years ago were a little denser than it actually is, our universe would have expanded so rapidly that matter could never have pulled itself together to form stars. And if the dark energy were a little smaller, the universe would have collapsed long before stars had time to form. Atoms are made in stars. Without stars there would be no atoms and no life.

So, the question is: Why? Why do these parameters lie in the narrow range that allows life? There are three possibilities: First, there might be some as-yet-unknown physics that requires these parameters to be what they are. But this explanation is highly questionable — why should the laws of physics care about the emergence of life? Second possibility: God created the universe, God wanted life (for whatever reasons), so God designed the universe so that it would allow life. Third possibility, and the one favored by many physicists today: Our universe is one of zillions of different universes with a huge range of parameters, including many different values for the strength of the nuclear force and the density of dark energy.

Some universes have stars and planets, some do not. Some harbor life, some do not. In this scenario, our universe is simply an accident. If our particular universe did not have the right parameters to allow the emergence of life, we wouldn’t be here to talk about it....Unfortunately, it is almost certain that we cannot prove the existence of these other universes. We must accept their existence as a matter of faith.

And here we come to the fascinating irony of the fine-tuning problem. Both the theological explanation and the scientific explanation require faith. To be sure, there are huge differences between science and religion. Religion knows about the transcendent experience. Science knows about the structure of DNA and the orbits of planets. Religion gathers its knowledge largely by personal testament. Science gathers its knowledge by repeated experiments and mathematical calculations, and has been enormously successful in explaining much of the physical universe. But, in the manner I have described, faith enters into both enterprises.

This is true and also ironic because the greater degree of faith must be possessed by the side that claims that it doesn't rely on faith - the naturalist who embraces the multiverse hypothesis (Lightman's third option above). In order to escape the conclusion that the universe is astonishingly calibrated to be life-permitting and thus the product of an intelligent agent, the naturalist latches onto a theory for which there's no empirical evidence. Moreover, it's hard to imagine how evidence of other universes could even be possible.

In science it's always preferable to favor the explanation which is simplest and for which there is the most evidence. The multiverse hypothesis which posits a near infinite ensemble of other universes is neither simpler nor supported by more evidence than the hypothesis that a single intelligent agent designed the universe in which we live.

The skeptic philosopher David Hume taught us that we should always base our beliefs on our experience. We have a uniform experience of fine-tuning being the work of minds. We have no experience of other universes. Thus, reason indicates that belief in a multiverse is irrational given an alternative hypothesis based on experience.

Nor do we have any idea what would be generating these other worlds and where the laws came from that govern their production. In other words, what explains the multiverse?

I doubt very much, though of course I can't prove it, that any scientist or philosopher would promote the idea of a multiverse were it not for the need to avoid the conclusion that a transcendent designer of the cosmos exists. The theory has about it a whiff of ad hocness and the strong scent of desperation.