Fine-tuning of the universe for life I

Part I: The case of entropy and the cosmological constant

Since the 1970s, physicists have noted the incredible balance reflected in the laws and constants of physics that allows this universe to support life. Although science has done a great job of explaining how the universe and life operate, it has not yet offered an adequate explanation for the origin of life or the universe. Once you realize that no one really knows why the universe is the way it is, then the question “What if things had been different?” becomes extremely interesting, and leads to some rather surprising conclusions. We apparently live in a kind of “Goldilocks universe”, where the fundamental forces of physics have just the right strength, the properties of the universe have just the right characteristics, and the initial distribution of matter and energy exhibits just the right configuration to make life possible. These facts taken together are so puzzling that physicists have named them “The fine-tuning problem”.

Fine-tuning is a technical term borrowed from physics and refers to the contrast between a wide range of possibilities and a narrow range of a particular outcome or phenomenon. In the case of the fine-tuning for life, it refers to the discovery that many properties of the universe fall within extremely narrow and improbable ranges that turn out to be necessary for any conceivable form of life to exist.

To quantify a bit, the most spectacular example is the level of fine-tuning in the initial entropy of the universe which is 1 part in 10^10^123 estimated by Roger Penrose. To get an idea of this extremely small number, let's remember that there are “only” ~10^80 particles in the universe. As you can see, this number is unimaginably precise, it implies that for every initial mass-energy arrangement that would result in a low-entropy universe like our own, there were 10^10^123 other possible ways of arranging that same matter and energy that would not. Similarly, most cosmologists accept that the cosmological constant Λ was finely tuned in no less than 1 part in 10^90. If Λ had been larger by a factor of 10^30, it would have been the dominant factor in determining the expansion rate of the universe only 6 minutes after the Big Bang. As a result, the universe would have expanded too quickly to produce elements heavier than hydrogen. Clearly, no complex structures such as galaxies could have formed in such a universe. Conversely, if Λ had been smaller by that same factor, the universe would have rapidly collapsed before any form of life could emerge. Therefore, the cosmological constant has a very evident and definitive effect on the necessary conditions for life. 

Acknowledging this, many theoretical physicists have referred to Λ as “the most extreme fine-tuning problem known in physics.” As astrophysicist Paul Davies put it: “This initial state was, therefore, exceedingly special and remarkable, yet an essential element in explaining the universe we perceive.

Do we just leave it at that, and accept that the universe was born in an exceedingly unusual state? Or is there a deeper explanation?”

Thus, the values of Λ and the initial entropy of our universe stand as the most spectacular measurable scientific evidence of the supernatural, super-intelligent design of the universe to make the existence of human beings possible. Theism proposes that God exists necessarily, and the physical world is the result of God’s free choice to create a morally valuable world. For theism, the fine-tuning for life shows how the God hypothesis could have explanatory power. Given the extraordinarily small proportion of possibilities that permit the existence of humans, theism holds that beneath the mathematical and physical structure of our universe there is a reason: 

Our universe is morally valuable, particularly we humans.

Post based on Stephen C. Meyer's Return to the God Hypothesis book, chapter 7, see resources.