In 1722, Johann Sebastian Bach published the Well-Tempered Clavier, a collection of music for the keyboard that featured two pieces, a prelude and a fugue, in every major and minor key. The work was ambitious, because until then, a harpsichord (the keyboard instrument of choice, since the piano was still in the early stages of development) could typically be tuned in such a way that only a few keys, such as C major or D minor, would sound properly in tune, while the more exotic keys would sound dissonant. Bach, who experimented with various schemes of tuning, sought to remedy that by tightening and loosening the strings of the harpsichord in a precise way. In advance of the equal temperament found on modern pianos, Bach showed that one could produce pleasant-sounding music in any key if the keyboard were finely tuned, or as he called it, wohltemperiert, “well-tempered.”

This same principle of fine-tuning extends, with farther-reaching consequences, to the physical properties of our universe. In the centuries since Bach, physicists have discovered several fundamental constants, numbers that describe the relationships between matter and energy, and among the four basic forces of nature: gravity, electromagnetism, and the weak and strong nuclear forces. As physicist (and Jesuit) Fr. Robert Spitzer notes in his book New Proofs for the Existence of God, even a slight variation in one of these numbers would result in a radically different universe from the one we know. The well-tempering of the universe makes possible something even greater than an F-sharp major fugue: human life.  A small change in any of these numbers would prevent life from existing.

For example, if the value of the coupling constant of the strong nuclear force were 2% higher than what it is, all the hydrogen in the universe would disappear, having been consolidated into heavier elements: stars would not be able to produce heat, and there would be no water. If it were 2% lower, then no elements larger than hydrogen would come into existence, such as the carbon, nitrogen, and oxygen necessary for life of any kind.

An even more sensitive value—in the 39th decimal place—accompanies the relative strengths of gravity and electromagnetism, which governs the production of stars. A small change in the ratio between the forces in one direction would make any star the size of our Sun unstable, and the only stars would be red dwarfs; in the other direction, the Sun would be too small to begin nuclear fusion, and the only stars would be blue giants. As astronomers continue to find planets around other stars, one of the main points to consider is whether it can sustain life, which is only possible on a planet in a narrow band around a Sun-like star. Other narrow ranges of values are necessary for supernovae to produce the heavier elements, and to prevent the universe as a whole from collapsing in on itself.

What does all this mean? Can this fine-tuning of cosmic forces come about only by chance? The fact that the existence of human life depends on several precise numbers inherent in the fabric of the universe, called the “weak anthropic principle,” presents a conundrum to anyone who faces the scientific facts: one must either believe in the extremely unlikely scenario in which this all can come together without any guidance; or believe in a Designer who arranged the universe in which our existence is possible.

While many have tried to save the first option by postulating many universes, each with its own set of fundamental numbers, this raises more problems and cannot be tested as a scientific theory—after all, how can you observe something in another universe? The latter case, with a supernatural Creator, is thus the more reasonable and more responsible answer. Judaism and Christianity make an even bolder claim: God created the universe in such a manner that led up to making the human race “in our image and likeness” (Gn 1:26). The fine-tuning of physical constants thus provided the way for God to place His stamp on creation.

While Christian faith affirms the God who created the universe according a well-tempered plan, the existence of a Creator can be discerned by reason also. The weak anthropic principle entails a probable argument; while not a conclusive metaphysical proof, in the manner of St. Thomas Aquinas’ Five Ways, it does lead the observer to think beyond “studying the works” toward “discerning the artisan” (cf. Ws 13:1). As physicist Paul Davies writes,

The delicate fine-tuning in the values of the constants, necessary so that the various different branches of physics can dovetail so felicitously, might be attributed to God.  It is hard to resist the impression that the present structure of the universe, apparently so sensitive to minor alterations in the numbers, has been carefully thought out . . . In the end it boils down to a question of belief.

Many have observed this precision in the physical constants and have asked themselves this question. Astronomer Fred Hoyle, a lifelong atheist and outspoken critic of the theory of the universe’s origin that he dubbed the “Big Bang,” commented that the anthropic principle was the single greatest challenge to his atheism. Yet, just as Bach inscribed “Soli Deo Gloria” (Glory to God alone) on his musical manuscript, the fine tuning of the forces and laws that hold the universe together shows that “The heavens proclaim the glory of God” (Ps 19:1).

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Image: Jan Steen, Harpsichord Lesson