Fine-Tuning an Argument and a Universe

Note: This weekend a friend asked me to recommend some resources on the fine-tuning of the universe. Since I had those handy, I thought it might be useful to turn it into a post.]

The heavens tell of the glory of God,” claimed the Psalmist, “The skies display his marvelous craftsmanship.” The ancient musician intuited aesthetically what modern cosmology is able to show mathematically. The arrangement of natural laws and other features provides not only stirring examples of the handiwork of our Creator but provides us with a strong argument for His existence.

Teleological arguments are arguments from the order in the universe to the existence of God. One of the most persuasive, yet least proffered, arguments of this type is the argument based on the “fine-tuning” of the universe for the existence of life forms. At least two dozen demandingly exact physical constants must be in place for carbon-based life to exist (see list at end of post), the slightest variation in any of these conditions—even to a minuscule degree—would have rendered the universe unfit for the existence of any kind of life.

“At least on the face of it, these so–called “anthropic coincidences” would appear to support the idea that we were built–in from the beginning,” says physicist Stephen Barr. “Even some former atheists and agnostics have seen in them impressive evidence of a divine plan.”

Indeed, as I hope to show, anthropic coincidences can form the basis of one of the most sound teleological arguments:

The apparent fine-tuning of the universe is due to either physical necessity, chance, or design.
The apparent fine-tuning is not due to physical necessity or chance.
Therefore, it is due to design.

The first option, physical necessity, is the easiest to dismiss. The idea that it was physically impossible for the universe to have been created in any way other than in a manner that would support life is neither logically necessary nor scientifically plausible. As Barr notes, “In the final analysis one cannot escape from two very basic facts: the laws of nature did not have to be as they are; and the laws of nature had to be very special in form if life were to be possible.” Our options, therefore, are between chance (the anthropic coincidences truly are coincidences) or design (the parameters needed for life were purposely arranged). While it cannot be established with absolute certainty, we can, I believe, determine that design is the most probable explanation.

There is little dispute that probability of this series of “coincidences” occurring is infinitesimally small. Still, it is often argued that since we exist then the probability must be 1. In their book, The Anthropic Cosmological Principle , John Barrow and Frank Tipler contend that we ought not be surprised at observing the universe to be as it is and that therefore no explanation of its fine-tuning is needed. In other words, we can only observe the need for fine-tuning in universes that support life.

Surprisingly, this dubious argument is often used as if it were a silver bullet that destroys the fine-tuning argument. But philosopher John Leslie (as told by William Lane Craig ) provides an illustration of why such reasoning is faulty:

Suppose you are dragged before a firing squad of 100 trained marksmen, all of them with rifles aimed at your heart, to be executed. The command is given; you hear the deafening sound of the guns. And you observe that you are still alive, that all of the 100 marksmen missed! Now while it is true that

5. You should not be surprised that you do not observe that you are dead,

nonetheless it is equally true that

6. You should be surprised that you do observe that you are alive.

Since the firing squad’s missing you altogether is extremely improbable, the surprise expressed in (6) is wholly appropriate, though you are not surprised that you do not observe that you are dead, since if you were dead you could not observe it. Similarly, while we should not be surprised that we do not observe features of the universe which are incompatible with our existence, it is nevertheless true that

7. We should be surprised that we do observe features of the universe which are compatible with our existence,

in view of the enormous improbability that the universe should possess such features.

Barr also provide a helpful analogy:

Suppose you were looking for a specific obscure recipe for, say, goulash. If the first book you took at random from the cooking shelf of the library happened to have exactly that recipe, you would regard it as a great coincidence. If you then discovered that the book contained every recipe for goulash ever invented, you would cease to regard it as coincidental that it had the one of particular interest to you. But you would be surprised nonetheless, for one does not expect a cookbook to treat that particular category of food so comprehensively. The fact that it happened to be so comprehensive in its selection of goulash, when it was goulash that you needed, would itself count as a remarkable coincidence.

Another problem I find with this line of thinking is that it implies that the probability of a stochastically independent event is determined by the existence of an observer. For example, imagine a universe that is exactly like ours yet contains no carbon-based life forms. We could determine the factors required for such an existence and calculate the probability of such constants appearing as they do. The result, of course, would be an infinitesimally small probability. The implication made by opponents of fine-tuning, though, is that the probability suddenly becomes 1 by the mere addition of a human observer. Such a conclusion is exceedingly absurd.

Most critics of fine-tuning have begun to recognize that this approach is insufficient. Faced with scientific evidence that undermines their agnostic assumptions, they turn to metaphysical speculation in the form of the “multiple universes” theory. There is a distinction, however, between the mulitple-domains within one universe and the multiple independent universes. As Barr explains:

In the version that physicists take seriously, the many “universes” are not really distinct and separate universes at all, but domains or regions of one all–encompassing Universe. The domains are far apart in space, or otherwise prevented from communicating with each other. Conditions are assumed to be so different from one domain to another that they appear superficially to have different physical laws. However, at a deeper level all the domains are really controlled by one and the same set of fundamental laws. These laws also control what types of domains the universe has, and how many of each type.

The other version of the idea posits the existence of a large number of universes that really are universes, distinct and unconnected in any way with each other. Each has its own set of physical laws. There is no overarching physical system of which each is a part. One can understand why this version is not discussed among scientists. At least in the many–domains version all the domains are part of the same universe as we, so that, even if we cannot in practice observe them directly, we might hope at least to infer their existence theoretically from a deep understanding of the laws of nature. In the many–universes version, this is not the case.

Briefly stated, the multiple universe theory is the hypotheses that if the universe contains an exhaustively infinite number of universes—all of which actually exist—then anything that can occur with non-vanishing probability will occur somewhere. While it might be true that the probability that our universe could develop in a way that supports life is incredibly small, these critics claim that in an infinite series of universes even the improbable is likely to happen quite often.

Such a move, however, commits the inverse gambler’s fallacy , which states that an improbable event can be made less improbable by the hypothesis that many similar events exist, and that the hypothesis is thence confirmed by the improbable event. Even if multiple independent universes do exist, though, it does not change the probability that our universe would turn out as it did. Again, to use an illustration by John Leslie :

There is no need for us to ask whether very great alterations in these affairs would have rendered it fully possible once more, let alone whether physical worlds conforming to very different laws could have been observer-permitting without being in any way fine tuned. Here it can be useful to think of a fly on a wall, surrounded by an empty region. A bullet hits the fly. Two explanations suggest themselves. Perhaps many bullets are hitting the wall or perhaps a marksman fired the bullet. There is no need to ask whether distant areas of the wall, or other quite different walls, are covered with flies so that more or less any bullet striking there would have hit one. The important point is that the local area contains just the one fly.

Having reduced the chance hypothesis to a virtual impossibility we are left with the obvious conclusion that the fine-tuning is not only apparent but actual. While this fine-tuning does not imply that the existence of a tuner is absolutely certain, it certainly makes it more probable than not. Unless one starts with the assumption that the Fine Tuner cannot or must not exist, it seems more probable (at least as a Baynesian inference that such a Being actually does exist.

Of course it must be noted that the the uses of such teleological argument are not likely to persuade the unbelief in the existence of God. As I have said many time before the unbeliever suffers from a form of invincible ignorance. There are no metaphysical and illogical knots the agnostically inclined will not twist themselves into in order to avoid having to admit that the existence of God is more reasonable and probable than its alternative.

Notes: A few people have pointed out that the original list I used by astrophysicist Hugh Ross includes too many anthropic coincidences. I’ve decided to replace it with an explanation by Jay Richards, co-author of The Privileged Planet :

Cosmic Parameters

(1) Gravitational force constant (large scale attractive force, holds people on planets, and holds planets, stars, and galaxies together)—too weak, and planets and stars cannot form; too strong, and stars burn up too quickly.

(2) Electromagnetic force constant (small scale attractive and repulsive force, holds atoms electrons and atomic nuclei together)—If it were much stronger or weaker, we wouldn’t have stable chemical bonds.

(3) Strong nuclear force constant (small-scale attractive force, holds nuclei of atoms together, which otherwise repulse each other because of the electromagnetic force)—if it were weaker, the universe would have far fewer stable chemical elements, eliminating several that are essential to life.

(4) Weak nuclear force constant (governs radioactive decay)—if it were much stronger or weaker, life-essential stars could not form.

(These are the four “fundamental forces.”)

(5) Cosmological constant (which controls the expansion speed of the universe) refers to the balance of the attractive force of gravity with a hypothesized repulsive force of space observable only at very large size scales. It must be very close to zero, that is, these two forces must be nearly perfectly balanced. To get the right balance, the cosmological constant must be fine-tuned to something like 1 part in 10^120. If it were just slightly more positive, the universe would fly apart; slightly negative, and the universe would collapse.

As with the cosmological constant, the ratios of the other constants must be fine-tuned relative to each other. Since the logically-possible range of strengths of some forces is potentially infinite, to get a handle on the precision of fine-tuning, theorists often think in terms of the range of force strengths, with gravity the weakest, and the strong nuclear force the strongest. The strong nuclear force is 10^40 times stronger than gravity, that is, ten thousand, billion, billion, billion, billion times the strength of gravity. Think of that range as represented by a ruler stretching across the entire observable universe, about 15 billion light years. If we increased the strength of gravity by just 1 part in 10^34 of the range of force strengths (the equivalent of moving less than one inch on the universe-long ruler), the universe couldn’t have life sustaining planets.

(6) Initial Conditions. Besides physical constants, there are initial or boundary conditions, which describe the conditions present at the beginning of the universe. Initial conditions are independent of the physical constants. One way of summarizing the initial conditions is to speak of the extremely low entropy (that is, a highly ordered) initial state of the universe. This refers to the initial distribution of mass energy. In The Road to Reality, physicist Roger Penrose estimates that the odds of the initial low entropy state of our universe occurring by chance alone are on the order of 1 in 10^10(123). This ratio is vastly beyond our powers of comprehension. Since we know a life-bearing universe is intrinsically interesting, this ratio should be more than enough to raise the question: Why does such a universe exist? If someone is unmoved by this ratio, then they probably won’t be persuaded by additional examples of fine-tuning.

“Local” Planetary Conditions

But even in a universe fine-tuned at the cosmic level, local conditions can still vary dramatically. As it happens, even in this fine-tuned universe, the vast majority of locations in the universe are unsuited for life. In The Privileged Planet, Guillermo Gonzalez and Jay Richards identify 12 broad, widely recognized fine-tuning factors required to build a single, habitable planet. All 12 factors can be found together in the Earth. There are probably many more such factors. In fact, most of these factors could be split out to make sub-factors, since each of them contributes in multiple ways to a planet’s habitability.

(7) Steady plate tectonics with right kind of geological interior (which allows the carbon cycle and generates a protective magnetic field). If the Earth’s crust were significantly thicker, plate tectonic recycling could not take place.

(8) Right amount of water in crust (which provides the universal solvent for life).

(9) Large moon with right planetary rotation period (which stabilizes a planet’s tilt and contributes to tides). In the case of the Earth, the gravitational pull of its moon stabilizes the angle of its axis at a nearly constant 23.5 degrees. This ensures relatively temperate seasonal changes, and the only climate in the solar system mild enough to sustain complex living organisms.

(10) Proper concentration of sulfur (which is necessary for important biological processes).

(11) Right planetary mass (which allows a planet to retain the right type and right thickness of atmosphere). If the Earth were smaller, its magnetic field would be weaker, allowing the solar wind to strip away our atmosphere, slowly transforming our planet into a dead, barren world much like Mars.

(12) Near inner edge of circumstellar habitable zone (which allows a planet to maintain the right amount of liquid water on the surface). If the Earth were just 5% closer to the Sun, it would be subject to the same fate as Venus, a runaway greenhouse effect, with temperatures rising to nearly 900 degrees Fahrenheit. Conversely, if the Earth were about 20% farther from the Sun, it would experience runaway glaciations of the kind that has left Mars sterile.

(13) Low-eccentricity orbit outside spin-orbit and giant planet resonances (which allows a planet to maintain a safe orbit over a long period of time).

(14) A few, large Jupiter-mass planetary neighbors in large circular orbits (which protects the habitable zone from too many comet bombardments). If the Earth were not protected by the gravitational pulls of Jupiter and Saturn, it would be far more susceptible to collisions with devastating comets that would cause mass extinctions. As it is, the larger planets in our solar system provide significant protection to the Earth from the most dangerous comets.

(15) Outside spiral arm of galaxy (which allows a planet to stay safely away from supernovae).

(16) Near co-rotation circle of galaxy, in circular orbit around galactic center (which enables a planet to avoid traversing dangerous parts of the galaxy).

(17) Within the galactic habitable zone (which allows a planet to have access to heavy elements while being safely away from the dangerous galactic center).

(18) During the cosmic habitable age (when heavy elements and active stars exist without too high a concentration of dangerous radiation events).

This is a very basic list of “ingredients” for building a single, habitable planet. At the moment, we have only rough probabilities for most of these items. For instance, we know that less than ten percent of stars even in the Milky Way Galaxy are within the galactic habitable zone. And the likelihood of getting just the right kind of moon by chance is almost certainly very low, though we have no way of calculating just how low. What we can say is that the vast majority of possible locations in the visible universe, even within otherwise habitable galaxies, are incompatible with life.

[Disclaimer: This is a hastily thrown together blog post and not a philosophical or scientific paper. While I think the overall argument is sound, I may have flubbed a few of the details within. Take those cum grano salis .]