I'm starting a series of posts on the subject of the supposed “Fine Tuning” of the universe. Co-written with my friend Oystein Elgaroy, this is a broad and hopefully accessible discussion of an exciting and widely mentioned topic.

The Fine-Tuning Argument

Steve Zara and Øystein Elgarøy

1. Introduction

As Carly Simon would say, this song ain’t about you. (Jon Stewart, the Daily Show, 13th March 2009)

Assuming that the constants of Nature - values which determine the structure and nature of the universe - can vary, and assuming that slight variations of them would have disastrous consequences for the existence of complex life, it is tempting to conclude that the universe is fine-tuned for our existence. This is the conclusion of the fine-tuning argument, summarized as follows by the apologist William Lane Craig (“Reasonable Faith (3rd edition)”):

   1. The constants of nature are fine-tuned for the emergence of complex life.
   2. The fine-tuning is due to physical necessity, chance, or design.
   3. It is not due to physical necessity or chance.
   4. Therefore, it is due to design.

If this argument is sound, it follows that there exists a Fine Tuner of some sort. This Fine-Tuner does not, of course, have to be anything like the Trinitarian God of Christianity, but surprisingly often this unwarranted leap is made. We aim to show in this article that the argument is fundamentally unsound. There is not only no need for a designer, but the idea of our universe being designed for life, let alone humans, makes no sense, either scientifically or logically.

Several numerical constants appear in the laws of physics. To take one example, Newton’s law of gravity states that the gravitational force between any two particles is proportional to the product of their masses, and inversely proportional to the square of the distance between them. The constant of proportionality is not determined by the theory, but has to be measured in experiments. Newton’s law of gravity is just an approximation to Einstein’s general theory of relativity, but the same constant appears in his theory and plays the same role in determining the strength of the gravitational force.

Electromagnetism, the weak nuclear force (involved in radioactive decay) and the strong nuclear force (holds the atomic nucleus and its components together) all have strengths determined by constants that have to be measured. The masses of most elementary particles are not predicted by current theories, and some of the fundamental parameters that describe our universe, like the current expansion rate, are also numbers we cannot predict, but have to measure.

If we assume that the constants describing the strength of gravity, electromagnetism, nuclear forces, and the large-scale structure of the universe could have been different, and calculate the properties of hypothetical universes where these numbers are allowed to vary from their values in ours, it has been claimed that we more often than not end up with universes where no life is possible. Stars would burn up their nuclear fuel before life could evolve on an orbiting planet, or the universe would contain so little hydrogen that stars could not form at all. Carbon and water, ingredients believed to be crucial for the origin and evolution of life, would never form.

The fine-tuning argument is a cousin of the argument from design in the biological realm. “Sophisticated” theists may no longer argue that the complexity of organic life points to a designer, but a large number of them appeal to the apparent fine-tuning of the laws of nature as an argument that a supernatural mind created the universe. Nothing in the argument warrants the leap to a “supernatural” mind. Just like the old design argument, the fine-tuning argument is an argument from analogy, so even if it is sound we are only allowed to conclude that a mind created the universe. One might suspect that the immediate introduction of a supernatural mind is made in an attempt to avoid the obvious question of who designed the Designer, or who tuned the Fine Tuner. So, even if it is sound, the fine-tuning argument proves rather less than the theist may want to establish. But the argument as it stands is not sound, and in the following we will exhibit some of its many weak points.

In this article we will look at fine tuning from many perspectives.  We will consider what fine tuning implies in terms of physics (2. What exactly does it mean to be fine-tuned?); what might lead us to believe that the universe is in some sense tuned for life (3. Why think that the parameters are fine-tuned?); even if there may appear to be tuning, is it optimal (4. Not-so-fine-tuning); is any apparent evidence for fine tuning what it seems (5. Has fine-tuning been established?); if the universe is tuned, that tuning is also for events that wipe out life (6. Fine-tuned for disaster?); how rare are apparently fine-tuned worlds like the Earth, and does life even need such worlds (7. The Rare Earth hypothesis); the relationship between fine tuning and probability (8. Fine tuning and probability); how multiverse ideas relate to the fine tuning argument (9. Fine tuning and the multiverse).