I have recently completed the book The Grand Design, by Stephen Hawking and Leonard Mlodinow. Hawking is one of the greatest minds of our era (called by one colleague the most revered scientific mind since Einstein). Co-author Mlodinow is not only a physicist, he has been a script-writer for Star Trek: The Next Generation. This author combo means the book is not only brilliant, it is very easy to read and even hilarious at times. Although Hawking does not profess to be a believer, toward the end of the book he gave the most brilliant defense of the anthropic principle I have ever encountered. The anthropic principle describes how the universe is uniquely fine-tuned for human existence, and therefore points to a higher power. In spite of his convincing presentation, Hawking insists that our existence is just lucky and explains how he believes that luck occurred at the end of the chapter. I will share the essence of his design argument and then the means by which he dismisses it and let you be the judge which side of Hawking’s argument is more persuasive.

In a chapter entitled "The Apparent Miracle," Hawking builds on the work of his friend Brandon Carter, a theoretical astrophysicist. Hawking begins with what he calls the "weak anthropic principle." First of all, he notes that any solar system with multiple suns would probably never allow for life. Life requires uniform heating over long periods of time. The kinds of orbits necessary in binary or multiple systems would result in extremes of hot and cold unsuitable to sustain life. The more suns in the system, the more extreme the temperature changes. So our single-sun solar system is a necessary pre-requisite for human life.

Second, planetary orbits can be circular or elliptical (like a squashed circle, or oval). The earth’s orbit is only 2 percent off of a perfect circle, so that deviation has little effect on temperature and even helps to stabilize the orbit. The reason for summer and winter is not the slightly elliptical orbit, but the tilting of the earth on its axis. The planet Mercury, with a 20 percent deviation from circular, on the other hand, is 200 degrees (F) hotter at its closest point to the sun than at its most distant point. If the earth’s orbit were as elliptical as Mercury’s, the oceans would boil away in summer and freeze over in winter. Radically oval orbits are not conducive to life, so it is good that earth’s orbit is nearly circular.

The earth is also just the right distance from a sun the size of ours. A star’s mass determines the amount of energy it gives off. Therefore, if our sun were 20% more massive the earth would be hotter than Venus. If it were 20% less massive, we would be colder than Mars. Likewise, if we were located any other distance from our sun than we now are, similar consequences would occur. The habitable zone around any star would be an orbit that allows liquid water to exist. The habitable zone around our sun is very small and the earth falls right in the middle of it! How "lucky" for us, says Hawking. If the solar system had had more than one sun, or earth’s orbit had been a different shape or we had been located differently, or the sun had been larger or smaller, we simply wouldn’t exist.

Not only that, we are where we are at just the right time, according to Hawking. It would take about ten billion years to naturally generate the kind of carbon distribution we find in the universe, a distribution also necessary for life as we know it. On the other hand, in a few billion years the stars will have used up most of their fuel, and we require a hot star for our survival. So we seem to be here at just the right time as well. Since there are an infinite variety of stars, planets and possible orbits, it is remarkable that our planet is so finely tuned for our existence. Are we lucky to be here or the product of an intentional Designer?

At this point Hawking brings up the great Bible-believing scientist, Isaac Newton. According to Newton, our solar system did not arise out of chaos by the mere laws of nature. Instead it was created by God in the first place and carefully sustained by Him until this day. But Hawking notes that Newton made that judgment without all the evidence we have today. Newton’s conclusion was impressive when this was the only solar system we knew about. But now we know that there are multiplied billions of stars orbited by countless planets, so the unique combination of factors that made life on earth possible is far less remarkable, in Hawking’s opinion. Planets of all sorts exist. Some, or at least one, support life. It’s no wonder we might think the Solar System was all there just for us, but with all the options out there, it shouldn’t be surprising that one of them is "just right."

So the weak anthropic principle leaves us with a bit of a stalemate, at least from a purely scientific perspective. But the anthropic principle is way more remarkable than what we have summarized so far. In the next blog we will summarize Hawking’s strong anthropic principle and the mental leap that Hawking has to make in order to avoid a believing conclusion.