Behind this principle are two assumptions. One is that the universe began, thus that a big bang took place. The other is that the starting conditions, the basic laws, might have been different. Three of these are gravity, the strong force (holding atomic nuclei together), and the electromagnetic; that last holds electrons in place around atoms and makes molecules possible. Very small changes any in these values would have produced a universe in which life would not have been possible. To take just one, gravity, if gravity were greater stars would have burned out more rapidly—no time for evolution. If weaker, no suns would have formed, no light would have nurtured life on planets; indeed planets wouldn’t have formed either. The principle is much more elaborate, but this much will suffice. The principle is named anthropic, thus related to man, because without finely-tuned laws, no humans would have come about.
The theory is not, of course, accepted in mainstream science; every discussion of it is bristlingly defensive. Modern science doesn’t hold with any kind of “tuning” at all; tuning implies a NoNo, namely that somebody is out there, behind the cosmos. At the same time, the principle at least implicitly views “life” as arising from matter; otherwise no tuning would be necessary. Alongside the big bang theory, which appears also to point at a “scientific” description of creation, the Anthropic principle is a favorite of those who would ground faith on the presumably more respectable foundations of science than on human intuition.
I’ve always found the Anthropic principle dubious for simple reasons. We don’t know what life is. We also haven’t the faintest notion about the basics of matter and have no proven theory of gravity (one of the tuned characteristic); all we have is descriptions of it. In one sense reality is an enormous Rorschach inkblot which permits any kind of projection whatsoever.
This prompted me in the beginning (of this blog, that is) to write a spoof on “the new saints” (link). One of the co-discoverers of the big bang was Georges Lemaître, a Belgian priest and physicist. I’ve always shared his very sensible approach to the subject. When he got word that Pope Pius XII was about to address the subject in a favorable manner, Lemaître hastened to the Vatican to put in a good word with Papal advisers. The big bang is just a scientific theory. And the fate of these is often to be overturned in time. The story of that intervention is told in this article (link). Lemaître’s own words, quoted in that article, are appropriate:
As far as I can see, such a theory remains entirely outside any metaphysical or religious question. It leaves the materialist free to deny any transcendental Being… For the believer, it removes any attempt at familiarity with God… It is consonant with Isaiah speaking of the hidden God, hidden even in the beginning of the universe.