Sunday, April 9, 2017

An Introduction to the Anthropic Principle and Fine Tuning

Most of the readers of this blog have probably heard about the anthropic principle and the fine-tuning of the universe.  However, because future posts will discuss the ramifications and speculations about fine-tuning, I thought it would be prudent to give a brief overview of these topics. Although not identical, the anthropic principle and the fine-tuning are definitely related.

The anthropic principle takes different forms, but is basically the idea that the universe has the necessary conditions for the existence of any conscious being that is able to observe the universe.  These conditions could, in principle, be very narrow or very broad in their scope. Many of the observations about the anthropic nature of our universe were developed beginning in the 1960's and continue to this day. Perhaps the most definitive book on the subject was written in 1986 by John Barrow and Frank Tipler, The Anthropic Cosmological Principle. The authors actually develop four anthropic principles with the first one, the Weak Anthropic Principle, being the most well known and uncontroversial principle, "The observed values of all physical and cosmological quantities are not equally probable but they take on values restricted by the requirement that there exist sites where carbon-based life can evolve and by the requirements that the universe be old enough for it to have already done so"1

Although the parameters required for life to exist could, in theory, span a large or small range, it turns out that many of the parameters necessary for life to exist in our universe must fall within a very narrow region, or the universe would either not exist or not be able to support life. The fact that the conditions for life fall into such a narrow range, plus the many incredible mechanisms that give rise to the needed building blocks of life, constitute the fine-tuning of the universe.

I liken the finely-tuned universe to a panel that controls the parameters of the universe with about 100 knobs that can be set to certain values. If you turn any knob just a little to the right or to the left the result is either a universe that is inhospitable to life or no universe at all.

Consider the knob that controls the strength of the strong nuclear force that holds quarks inside the neutrons and protons and binds the nucleus of the atom together. If the strength were increased by 2%, the element hydrogen would be either non-existent or very rare. Without hydrogen there would be no water (H2O) or stars that burn hydrogen as their nuclear fuel like our sun.  Without hydrogen there would be no life. If the strength of the strong nuclear force were decreased by about 5%, then hydrogen would be the only element in the universe. That would simplify the periodic table and make Chemistry class very easy, but it would render life impossible.

All known life in this universe is based on the element carbon, which is formed in the final stages of a star's life. The carbon you and I are made of is the result of the nuclear processes that occurred as previous stars ended their lives. One nice recent study showed that if the mass of the quarks that make up neutrons and protons were changed by just a few percent, then the process that makes carbon as stars die would be altered in such a way that there would not be sufficient carbon in the universe for life. The masses of the lightest sub-atomic quarks are the precise value that is required for carbon to form and for life to exist.

There are many more aspects of the universe that seem finely tuned to allow life to exists, some of which I will discuss in future posts. I find that, in general, there are three major responses among scientists who comment on the unlikelihood of a universe so well tuned. The first is simply an acknowledgement that the universe seems finely-tuned but a lethargic attitude that accepts this as a necessary requirement for existence without any further analysis. To me this attitude is similar to a condemned criminal who is sentenced to die in front of a firing squad, but is not surprised that all 100 sharpshooters missed him when they fired. He simply says, "Well if it was any other way I wouldn't be here to talk about it." The second response is a belief that there are many universes that exist (a multiverse) and that we just happen to be in one that is capable of supporting life. Although there is no evidence for any other universes, this is a commonly held belief that I will talk about more in a future post.  In any case, I don't find the idea of a multiverse threatening to the third alternative.

The third alternative is that the universe looks finely-tuned because it is actually designed.  This seems to be the most straightforward interpretation of the facts.  It seems reasonable that a universe which looks designed and tweaked really is.  As with other topics that have been discussed in this blog we see that the scientific evidence aligns perfectly with the hypothesis that there actually is a God who created the universe. It could have been different. We could be living in a universe in which the "knobs" have a wide range of settings that support life and could be randomly set. But we do not live in such a universe. We live in one with a very narrow range of values for dozens of knobs all set in just the right place. The scientific evidence shows a universe that appears to have an architect and designer behind it all who has tweaked nature's numbers to create a life-friendly universe. This adds to the the abundant evidence from science that, I believe, is best explained by a transcendent, personal God.

1Barrow, John D. Tipler, Frank J. (1988). The Anthropic Cosmological Principle . Oxford University Press.
2Evgeny Epelbaum, Hermann Krebs, Timo A. Lähde, Dean Lee, and Ulf-G. Meißner "Viability of Carbon-Based Life as a Function of the Light Quark Mass, Physical Review Letters 110, 112502, (2013).


  1. How many of these parameters have actually been tested for fine tuning? To illustrate this for my school age son's science project, I had him bake several batches of cookies, each time varying one ingredient up or down by a small amount. He called it a "A Cookie Universe" and successfully demonstrated the fine tuning principle. Now, if we could only do this with as many of the real parameters, wouldn't that give skeptics an empirical problem to explain.

    1. I like your son's project. That is a great way to illustrate the fine-tuning principle. As far as your question is concerned, it is almost impossible to give a definitive answer to the number of fine tuning parameters. I usually say about 100, or dozens, based on the items discussed in Barrow and Tiplers' book The Anthropic Cosmological Principle. In his 1999 book, Just Six Numbers, Martin Rees lists six dimensionless constants that give overall fine-tuning to the universe. On the Reasons To Believe web site, Hugh Ross has compiled a list of 322 parameters necessary for a planet to support higher life forms. So I think it depends on how you try to classify the fine tuning. I'm comfortable with saying about 100 based on Barrow and Tipler's book. Although you could argue there are only six based on Rees's book, I think that is an under-estimation since I'm not sure it would include all important processes necessary for life like the formation of carbon as part of a star's life cycle, or the parameters necessary to create a planet suitable for higher life forms.

  2. The most recent estimate or count states there are roughly 20,000 genes in teh human genome. To say the human genome is fine tuned is an understatement since we know the malformation in gestation most frequently results in deficiency, malformation, disease, death, deformity or a life of diminished function,pain and early death. Originally a perfect genome created by God now diminished and susceptible all its existence to mutation followed in many cases by the most serious diseases onset. The ultimate example of a God designed tuning of 20,000 "parameters" and their sensitivity to perturbation.

  3. I am very grateful for this enlightening article. I am new to this issue, but for me it elucidated several questions. Congratulations on your knowledge on the subject. Thank you very much. QuarkXPress 2017

  4. According to Michel Brooks
    "13 Things that don't make sense" the actual value of the vacuum energy of space is only 1/10**120 different from the theoretical value. So is the big bang refuted? No! It must be that the alternative is too offensive to scientifically beliefs.

    1. I'm not sure what your point is. The big bang is the "alternative" to a naturalistic explanation for the beginning of our universe. I encourage you to read my post titled "Should the Big Bang be disdained?" The 10**120 fine tuning even gives more evidence for a designer as well.