In the previous blog we talked about the "environmental coincidences" that make life possible on this earth. Isaac Newton attributed those "coincidences" to the work of God and Stephen Hawking suggests that they were an accident of nature. Ours is only one cosmic habitat out of many that exist in the universe and we obviously must exist in a habitat that just happens to support life as we know it.

But Hawking acknowledges that there is a much stronger form of the anthropic principle. It is not only the location of earth in the universe that is "just right" for human existence, but the very laws of nature themselves happen to be "just right" for human existence as well. (I should note that other cosmologists, such as John Barrow and Frank Tipler, define the weak and strong anthropic principles a little differently than Hawking, but I am following Hawking’s approach) In other words, the entire universe has to be just the way it is for life to exist on our planet. In much of what follows, most readers will need a bit of faith that these things are so, since I am over-simplifying some very complex but exciting concepts. But the concepts are based on Hawking’s work and he is as familiar with these concepts as anyone on earth.

In order to produce life as we know it, the forces of nature had to be such that heavier elements, especially carbon, could be produced from more basic elements and remain stable for billions of years. These heavier elements were formed in the furnaces we call stars, so stars and galaxies had to be there for carbon to form. Stars can only exist if matter is not uniformly spread around the universe, but varies in density. Not only so, the stars that form have to then explode in precisely a manner to disburse the heavier elements throughout space. Then these heavier elements needed to recondense into a new generation of stars surrounded by planets incorporating the newly formed heavy elements. Just as certain events on earth had to occur for life to develop, so every link of this universal chain is necessary for our existence. But for this chain to occur, the fundamental laws of nature had to be "just right."

Hawking goes on to affirm that life as we know it would be extremely doubtful in the absence of carbon. Carbon bonds with other elements in a unique way that is essential for life as we know it. For example, carbon dioxide is very useful for life, but its closest chemical relative, silicon dioxide, is quartz, not particularly breathable. Carbon is formed inside stars from the collisions of three helium nuclei and only because of a special characteristic of the laws of nuclear physics. If the laws by which the elements of the universe interact deviated by just a few percent, it would destroy either all the carbon or all the oxygen in every star and thus the possibility of life. In other words, change the natural laws of our universe just a bit and the conditions for our existence disappear. In the words of Fred Hoyle, "I do not believe that any scientist who examined the evidence would fail to draw the inference that the laws of nuclear physics have been deliberately designed (emphasis mine) with regard to the consequences they produce inside the stars."

The above has now proven to be a general principle. Take almost any law of the universe, alter it by only a modest amount, and the universe would be very different and likely unsuitable for life. If protons were less than one percent heavier, they would decay into neutrons, destabilizing atoms. If the makeup of the quarks in a proton were changed by as little as ten percent, few atomic nuclei would be stable, and stable nuclei are an essential element of life.

For stable, elliptical planetary orbits to exist, the universe has to function in three dimensions. In any but three dimensions the pull of other planets would send a planet off its orbit either into or away from its sun. In more than three dimensions, the sun would either break apart or collapse into a black hole, "either of which would ruin your day." (The book is really hilarious at times) Similar problems would occur in the case of atoms, causing them to self-destruct. To quote Hawking, "The laws of nature form a system that is extremely fine-tuned, and very little in physical law can be altered without destroying the possibility of the development of life as we know it."

But there is an "environmental coincidence" even more impressive than this, which leaves Hawking "almost persuaded" to believe in a Designer. It relates to Einstein’s "cosmological constant" of general relativity. Since all matter attracts other matter, Einstein proposed an anti-gravity force to combat the tendency of the universe to collapse onto itself. The cosmological constant describes the strength of that force. Scientists now believe the universe is expanding from an original "Big Bang," so for a time the cosmological constant was discarded. However, it was recently discovered that the universe is expanding at an accelerating rate, which means Einstein’s repulsive force does exist after all. Here’s the point. If the cosmological constant were much larger than it is, the universe would have blown itself apart long before galaxies could form, and life as we know it would be impossible.

This "strong anthropic principle" seems more than coincidental, even to Hawking. It is a "different kind of luck" than the environmental factors of the weak anthropic principle described in the previous blog. It cannot be easily explained and has deep philosophical implications. To use Hawking’s own words, "Our universe and its laws appear to have a design that both is tailor-made to support us and, if we are to exist, leaves little room for alteration. That is not easily explained, and raises the natural question of why it is that way." To put it another way, the chance that life as we know it would come to exist in the universe by pure chance is about one in 10⁵⁰⁰ For all practical purposes, that is impossible.

Why is it, then, that Hawking still does not believe in a Designer? Why does he still believe that our universe is the product of luck or chance? I will deal with that in the final blog of this series and also share my own reaction.