Fine Tuning of the Universe

[GildartsTale]

Fine-tuning refers to the surprising precision of nature’s physical constants and the early conditions of the universe. To explain how a habitable planet like Earth could even exist, these fundamental constants have to be set to just the right values (like tuning a dial to find just the right radio station). If the universe had physical constants with even slightly different values, the universe simply could not support life: it would expand too quickly, or never form carbon atoms, or never make complex molecules like DNA.

The multiverse is the idea that our universe is one of possibly infinitely many universes. Out of the many possible universes that may exist, each with different strengths of forces and properties of particles, our universe is one of very few which is capable of hosting life as we know it. How do people respond to fine-tuning and the multiverse? What do they imply for our understanding of God?

Fine-tuning refers to “just right” properties​

Our universe has several properties that are set to precise values, and slight changes to those values would prevent life as we know it. Here are three examples.

The strength of gravity​

When the Big Bang occurred billions of years ago, the matter in the universe was uniformly distributed. There were no stars, planets or galaxies—just particles floating about in the dark void of space. As the universe expanded outwards from the Big Bang, gravity pulled ever-so-gently on the matter, gathering it into clumps that eventually became stars and galaxies. But gravity had to have just the right force—if it was a bit stronger, it would have pulled all the atoms together into one big ball. The Big Bang—and our prospects—would have ended quickly in a Big Crunch. And if gravity was a bit weaker, the expanding universe would have distributed the atoms so widely that they would never have been gathered into stars and galaxies.

The strength of gravity has to be exactly right for stars to form. But what do we mean by “exactly”? Well, it turns out that if we change gravity by even a tiny fraction of a percent—enough so that you would be, say, one billionth of a gram heavier or lighter—the universe becomes so different that there are no stars, galaxies, or planets. And with no planets, there would be no life. Change the value slightly, and the universe moves along a very different path. And remarkably, every one of these different paths leads to a universe without life in it. Our universe is friendly to life, but only because the past 13.8 billion years have unfolded in a particular way that led to a habitable planet with liquid water and rich chemistry.

The formation of carbon​

Carbon is the element upon which all known life is based. Carbon atoms form in the cores of stars by fusion reactions. In these reactions, three helium atoms collide and fuse together to make a carbon atom. However, in order for that fusion reaction to work, the energy levels must match up in just the right way, or the three helium atoms would bounce off of each other before they could fuse.

To create this unusual match-up of energies, two physical forces (the strong and electromagnetic forces) must cooperate in just the right way. The slightest change to either the strong or electromagnetic forces would alter the energy levels, resulting in greatly reduced production of carbon. The values are tuned so that carbon is produced efficiently, leading to abundant amounts of an element we need for life.

The stability of DNA​

Every atom has a nucleus of protons and neutrons and a cloud of electrons swirling around it. When an atom binds with another atom to make a molecule, the charged protons and electrons interact to hold them together. The mass of a proton is nearly 2,000 times the mass of the electron (1,836.15267389 times, to be precise). But if this ratio changed by only a small amount, the stability of many common chemicals would be compromised. In the end, this would prevent the formation of many molecules, including DNA, the building blocks of life. As theologian and scientist Alister McGrath has pointed out,1

[The entire biological] evolutionary process depends upon the unusual chemistry of carbon, which allows it to bond to itself, as well as other elements, creating highly complex molecules that are stable over prevailing terrestrial temperatures, and are capable of conveying genetic information (especially DNA).

These are just a few examples.

Evidence for fine-tuning is recognized by physicists and astronomers of all religions and worldviews, and has been for decades. As agnostic Steven Weinberg, a Nobel Laureate in Physics, wrote,

…how surprising it is that the laws of nature and the initial conditions of the universe should allow for the existence of beings who could observe it. Life as we know it would be impossible if any one of several physical quantities had slightly different values.

Implications of fine-tuning​

Some agnostics and atheists see fine-tuning simply as a lucky accident. For some, this is a nonchalant shrugging of the shoulders; fine-tuning “is what it is” without any further implications. Some make a more specific argument: because humans exist, the laws of nature clearly must be the ones compatible with life, otherwise, we simply wouldn’t be here to notice the fact. (This is called the “anthropic principle;” see this good introduction by leading Christian physicist John Polkinghorne.) To argue against this line of reasoning, philosopher John Leslie makes the analogy of surviving an execution at a firing squad completely unharmed,2 summarized here by astronomer and BioLogos President Deborah Haarsma:



Of course the survivor would look for an explanation for why such an unlikely event occurred! In the same way, most people are curious to figure out why the universe is the way it is, both scientifically and theologically. As astronomer Fred Hoyle wrote, “A commonsense interpretation of the facts suggests that a super-intellect has monkeyed with physics, as well as with chemistry and biology.” Physicist Freeman Dyson wrote, “The more I examine the universe, and the details of its architecture, the more evidence I find that the Universe in some sense must have known we were coming.”3

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1. Alister McGrath, A Finely-Tuned Universe: The Quest for God in Science and Theology (Westminster John Knox Press, 2009), 176. See chapters 10 and 11 for biological fine tuning of the environment.
2. John Leslie, Universes (Routledge, 1996), 13-14.
3. Freeman Dyson, Disturbing the Universe (New York: Harper and Row, 1979).

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