This is a WordPress repost of an excellent introductory article originally posted by Experimental particle physicist Dr Michael G Strauss. It is reproduced here in it’s entirety for your viewing convenience. If you are not familiar with the Anthropic Principle and Fine Tuning, this is definitely the initial article to read. And if you are not familiar with Dr Michael Strauss might I suggest that you bookmark his website for more of his enlightening posts. Enjoy!
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.2
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).