Draft of Friday, December 5, 2003, 3:06 PM.For comments only. Do not distribute.Victor J. StengerThe Anthropic PrincipleTHE FOCUS OF EXISTENCEA small child, encircled by adoring parents and grandparents, easily believes herself to bethe center of the universe. So too humanity, in its childhood, saw itself at the focus ofexistence. This comforting view was shattered four centuries ago, when Copernicus andGalileo discovered that Earth does not possess a unique place in the cosmos. Moderncosmology and geology have confirmed that observation with a vengeance, leavinghumankind to face the fact that it exists within an unexceptional, almost negligiblepinpoint of space and time.In recent years, however, new thinking has emerged that aims to return humanbeings to the focus of existence. The claim is being heard that universe appears to behighly fine-tuned for our kind of life. Let us take a look at some of the evidence that iscalled upon to support this assertion.CARBON AND COMPLEXITYLife is, at least in part, matter organized to a very high level of complexity. The onlyform of life in the universe of which we are aware is that found on our home planet. Thatlife is based on the chemical element carbon, whose four-valence structure and otherproperties make it particularly well suited as the framework upon which molecules22containing many atoms in a wide range of complex shapes and with a large variety ofproperties can be assembled. While other elements, such as silicon and germanium, havesimilar structures, and indeed are used in semiconductor technology to manufacturedevices with complex properties of their own, carbon seems best suited for a form of lifeto evolve under the conditions that exist on Earth and perhaps elsewhere in our universe.Whatever elements serve as the building blocks of complex structures, they didnot exist in nature when our universe first formed 14 billion years ago. Cosmologists andphysicists now have a reliable theoretical picture of those early stages. Beginning in atiny region of space far smaller than an atomic nucleus, the universe emerged as anexpanding ball of hot gas and radiation called the big bang. After a few minutes, that gascooled to the point where atoms could hold together without being ionized by theradiation.The radiation has cooled off considerably since, forming the current cosmicmicrowave background, which is just 2.7-degrees Celsius above absolute zero. One outof every billion of the primordial bodies was a hydrogen atom, with even smalleramounts of helium and lithium. These comprise the first three elements of the chemicalPeriodic Table that we see hanging on the wall of many science classrooms. Over aperiod of perhaps 100 million years, these elements were gathered by gravity into the firststars.Another billion years or so was needed for stars to produce the carbon and otheringredients needed for the evolution of life. The main source of energy production instars is the fusion of hydrogen nuclei into helium. The larger a star, the faster it evolves.When its hydrogen is used up, other nuclear processes take over and synthesize carbon33and the other heavier elements. If the star is at least ten times as massive as our sun, itwill produce a gigantic explosion called a supernova, in the process blasting the newlymade elements into interstellar space. Once there, this matter can be assembled, bygravity, into planets like Earth. And so, Earth formed six billion years ago, eight billionyears after the big bang, with a heavy core of iron and a surface containing enoughcarbon, oxygen, and other substances needed for life to form.In 1952, astronomer Fred Hoyle calculated that sufficient carbon would not beproduced in stars unless the nucleus of carbon contained a previously unknown excitedstate of a specific energy. A laboratory experiment, proposed by Hoyle, shortlyconfirmed the existence of this state.The properties of atomic nuclei are determined by fundamental constants ofnature, such as the masses of the proton and neutron and the strength of the nuclear force.The values of these constants were already set billions of years before Earth formed, andindeed long before the formation of the first star. Yet these constants seem speciallyselected to allow for the eventual development of carbon-based life.THE ANTHROPIC COINCIDENCESFor many years, physicists have pondered why the constants of physics have theparticular values they do. Perhaps the biggest puzzle is the huge difference between thestrengths of the gravitational and electromagnetic force. Consider the hydrogen atom,which is composed of a proton and electron of equal and opposite electric charge. Theelectrical attraction between these two particles is thirty-nine orders of magnitude greaterthan the gravitational attraction. Why thirty-nine orders of magnitude? Why not 58 or137?44Everything else being equal, you might expect the two forces to be comparable instrength. But, suppose they were. A star is maintained in equilibrium by a balancebetween the attractive force of gravity and the pressure of the outgoing electromagneticradiation that is produced by the nuclear processes going on at the star’s core. If gravitywere the same strength as electromagnetism, a star would quickly collapse—long beforeany heavy elements could be made. So, once again, we seem to have a tuning of theparameters of physics to allow time for the elements of life to be fabricated and spreadthroughout space. The seeming connections between physics parameters and life arecalled the anthropic coincidences.In their 1986 book, The Anthropic Cosmological Principle, physicists JohnBarrow and Frank Tipler assembled a large number of examples to illustrate how thelaws and constants of physics appear to be fine-tuned for the evolution of life. In manycases, changing a constant by a tiny amount is sufficient to make life, as we know it,impossible.For example, the element-synthesizing processes in stars depend sensitively onthe properties and abundances of deuterium (heavy hydrogen) and helium produced in theearly universe. Deuterium would not exist if the difference between the masses of aneutron and a proton were just slightly displaced from its actual value. The relativeabundances of hydrogen and helium also depend strongly on this parameter. Theseabundances also require a delicate balance of the relative strengths of gravity and theweak nuclear force, which is responsible for energy production in stars. A