Another argument used by creationists and theists as proof of celestial design is the so-called "fine tuning of the universe." It turns out that the existence of a universe that permits life as we know it depends heavily on the size of certain constants in the laws of physics. If, for example, the charge of the electron were slightly different, or if the disparity in mass between a proton and a neutron were slightly larger, or if other constants varied by more than a few percent, the universe would differ in important ways. Stars would not live long enough to allow life to emerge and evolve, there would be no solar systems, and the universe would lack the elements and the complex chemistry necessary for building organisms. In other words, we inhabit what is called a "Goldilocks universe," where nature's laws are just right to allow life to evolve and to thrive. This observation is called "the anthropic principle."
At first glance, its explanation appears trivial. As Ken Miller says, "Taking as a starting point the observation that you and I are alive, at least in the immediate present, it's obvious that we must live in a universe where life is possible. If we didn't, we wouldn't be here to talk about it. So, in a certain sense the fact that we live in a life-friendly universe merits little more than a big 'Duh.'" True. But this raises a deeper question: why do the constants of the universe just happen to have those life-promoting values? The answer given by creationists is that this is no accident: a beneficent God (or an intelligent designer) crafted those physical laws precisely so that somewhere in the universe intelligent life would evolve--life so intelligent that it could work out the laws of physics and, more important, apprehend their creator. This answer--known as the strong anthropic principle--is scientifically untestable, but it sounds so reasonable that it has become one of the biggest guns in the creationist arsenal. (It is important to grasp that anthropic principles concern the conditions required for the existence of any life, and say nothing about the inevitability of complex and intelligent life.)
Also, scientists have other explanations, ones based on reason rather than on faith. Perhaps some day, when we have a "theory of everything" that unifies all the forces of physics, we will see that this theory requires our universe to have the physical constants that we observe. Alternatively, there are intriguing "multiverse" theories that invoke the appearance of many universes, each with different physical laws; and we could have evolved only in one whose laws permit life. The physicist Lee Smolin has suggested a fascinating version of multiverse theory. Drawing a parallel with natural selection among organisms, Smolin proposed that physical constants of universes actually evolve by a type of "cosmological selection" among universes. It turns out that each black hole--and there are millions in our universe--might give rise to a new universe, and these new universes could have physical constants different from those of their ancestors. (This is analogous to mutation in biological evolution.) And universes with physical constants close to the ones we see today happen to be better at producing more black holes, which in turn produce more universes. (This resembles natural selection.) Eventually this process yields a population of universes enriched in those having just the right properties to produce stars (the source of black holes), planets, and life. Smolin's theory immensely raises the odds that life could appear.
The idea of multiple universes may seem like a desperate move--a Hail Mary thrown out by physicists who are repelled by religious explanations. But physics is full of ideas that are completely counterintuitive, and multiverse theories fall naturally out of long-standing ideas of physics. They represent physicists' attempts to give a naturalistic explanation for what others see as evidence of design. For many scientists, multiverses seem far more reasonable than the solipsistic assumption that our own universe with its 10,000,000,000, 000,000 planets was created just so a single species of mammal would evolve on one of them fourteen billion years later.
The full article, Seeing and Believing, can be read here.