The Anthropic Principle

The evolutionary theory of Charles Darwin has shown how the amazingly intricate adaptations to the environment that we observe among living species, could have arisen without divine intervention. Without the so-called "Watchmaker," modern biologists such as Richard Dawkins have been moved to suggest that all of life is a fluke chance that has occurred without help in a "pitilessly indifferent universe." However, physicists and cosmologists are suggesting that the universe is not so "pitilessly indifferent" but in fact is finely tuned in a remarkable number of ways that altogether allow it to give birth to life.

Before continuing, one must be careful not to fall into the trap, which is parodied by Gerald Feinberg and Robert Shapiro in "A Puddlian Fable." There they make the point that we should not be too surprised in finding ourselves in a well-suited environment, as that is the one we have biologically evolved to fill. Hence, of the nine planets in the solar system, we should not be surprised that we live on the planet that has liquid water, an atmosphere, and so on, as we could not exist elsewhere. In fact, if there are millions of planets in the galaxy, and only one (ours) has Earth-like conditions, then of course it is to be expected that if something like us arises, then it will be on Earth - we should not be surprised that Earth is just right for us. In contrast, as we know that most other kinds of planets are unlikely to support any kind of life, it would be very surprising if only one planet existed, and that one was Earth, having conditions just right for life.

Now, it is generally considered by definition that there is only one universe. We have discovered that the universe exhibits laws of physics, which are constant over time and space. The constancy and beauty which physicists find in these laws often speak to them of God, and leave them with a religious awe, but that is not the point of this argument. What has come into prominence in recent years is the idea that if any of these laws were changed just slightly, then no life could come into being. Some responses that I have heard by scientific skeptics to this view, is that we just do not have a wide enough imagination for the possibilities of life. They suggest that if the constants of nature were different, then we would not be around, but there would be some other life form based on a different chemistry, which could also ask questions like "why is the universe just right for me?" If that were so, then the argument, known as the Anthropic Principle would fall into the Puddlian trap mentioned above.

However, it is not so. Although the specifics of carbon chemistry, which enable our life to occur, may not be necessary for life in a theoretical alternate universe, there are some qualities of life that must be ubiquitous. That is, a living being must contain organized complexity, or information. The minimum requirements for information content can be determined by fundamental mathematical theory, and it is clear that it requires a local increase in energy, or to be more precise, a local decrease in entropy. Entropy is a physical term which describes the disorder in a system, and for a closed system (that nothing enters or exits) entropy always increases. That is, disorder always increases - cups fall and shatter, they do not coalesce and jump onto the saucer. More importantly, without sustenance and breath, bodies die and decay, while corpses do not come back to life. A living being with the ability to ask the question "why am I here?" must contain an incredible amount of order to be able to frame such a deep, information-filled thought, whatever kind of chemistry or physics underlies the being. So the question is, "what kinds of universe could allow such order to arise?" If the answer is "just about any" then we should not be so surprised about our universe - the right, well-suited type of order would arise to fit the environment in any universe. However, if the answer is "almost none," then we do need to question why the universe is so special.

It is well known that all life on Earth (barring the strange sulfurous life arising around deep-sea volcanic vents) is ultimately dependent on the in-flowing energy from the sun. The sun is an average star, and, like all stars, can provide the power for life, by providing vast amounts of energy (as heat and light) at very low entropy (from a small region much hotter than the rest of the universe). Hot spots, such as stars, are necessary to allow any form of organized complexity to arise. Living things must all take in low entropy (hot or organized) energy and release it at high entropy (useless waste heat) in order to increase or at least maintain their internal information. The "hot spots" which allow any living being to survive, must also be there for it to evolve, so must remain stable over a large period of time, compared to typical physical processes in the life cycle of the being. Now, in our universe there is a specific resonance in the nuclear reaction process, which enables stars to burn at all, and ensures there typical life is of the order of the billions of years that have been necessary for life to develop. In a universe almost the same as ours, but perhaps with a slightly different electron mass, the resonance would not occur, stars would not shine, and the universe would be dark, dead and dull.

There is a multitude of similarly finely tuned properties of our universe, which have been essential for the formation of human life. The storage of information about us is within molecules, which would be unstable if protons were lighter or inalterable if protons were much heavier. These molecules are based on carbon, which is only formed within a supernova (not in fact a new star as its name suggests due to its sudden appearance in the night sky, but the explosive destruction of a large old star). The delicate balance between the original expansion of the universe and the gravitational attraction, which tends to pull everything back together, ensures that the explosive debris from one star can arrive in the vicinity of another star which forms separately. All life on Earth is made from atoms of debris from the first star, while relying on the heat and light from the second star, namely our sun. In a gravitationally stronger universe, the first star would swallow the second, while in a weaker, more spread out universe, the debris would never reach another star.

These examples of ways in which the universe appears to be designed to enable our existence lead to two forms of the Anthropic Principle. The weak form, which provides no controversy, states the obvious fact that as we are here, conditions must be just right for our existence. The strong anthropic principle goes further, as it suggests that the universe was designed for our existence. Those characteristics of the universe that appear tuned to allow for our specific kind of life might only provide reason to follow the weak form of the argument. Perhaps if those characteristics were different, then they would allow another kind of life. It does seem, though, that alterations of the characteristics that, for example, allow carbon based molecules to exist, would only prevent our form of life from occurring, and not give rise to the possibilities of other forms of life. Even more convincing that our universe is "special" in an objective way, is that almost any other would not give rise to stable "hot spots" such as stars which fuel the journey to life. So it does seem that our universe is extraordinary, and its improbability requires further explanation.

Many cosmologists are attempting to find what explanation they can within science, in preference to invoking a Creator to explain the surprise. Unfortunately, they are working in a realm where there is a dearth of data - only the ripples left on the cosmic background radiation give us any clues to how the universe started. Still, that is enough to provide strong evidence for a period of inflation, the name given to an exponential expansion period of negative pressure in the first 10-33 seconds of the universe's existence. If such an era existed, there is no reason that the universe we observe is all that condensed from the inflationary phase. There could be a plethora of other universes, or I should say sub-universes, that are completely unobservable to us. If this were so, then it is not so surprising that one of a multitude of sub-universes happens to have the right conditions for life. A similarly untestable possibility put forth by scientific skeptics is that the universe is really infinite in time, and just bounces in and out of big crunches and big bangs. There is supposedly a new set of laws of physics each time round (though, this is rather implausible in my view, as the new mashed up fundamental laws must always lead to another bouncing universe, without being specifically tuned!).

Other physicists, in their search for a fundamental theory of everything, hope to show that only one consistent set of laws of physics is possible. Assuming these laws contain no outside parameters, then they suggest that everything would be explained. I think it would be just as great a miracle if the one set of laws that could exist is the one set of laws that gives rise to life! Also, why the laws must be followed, and why they must be mathematically consistent begs further questions about a supernatural overseer. However, most scientists, long before this stage have decided that they are outside the realm of science, and therefore do not need to consider the implications of this paper.

While scientific skeptics deny the strong anthropic principle, many theologians and religious scientists embrace it, as it points to a Creator who stimulates life and enables us to flourish. The uncovering of such a fertile universe, which is so clearly conducive to beauty, encourages process theologians, as it appears that the universe follows a very thin line between rigid order and incoherent chaos. Other religious thinkers remain wary of the whole argument, and following the "contrast" viewpoint, are loathe to incorporate any scientific evidence, which may be later reinterpreted, in their vision of God. As the "many universe" theories are not completely outside the realms of falsifiable evidence, it is perhaps right to be patient before hailing the fine-tuning as proof of God. Nevertheless, I for one do not cease to be amazed by the transcendent beauty inherent within the laws of nature. These will always speak to me of the Nature of God.

Paul Miller
Last modified: Wed Oct 13 18:04:58 EDT 1999