By Brett van de Sande, member

I was thinking a bit about Hugh Ross’ fine-tuning argument.  Essentially, he is saying that any instance of fine-tuning is a good thing and that it is best explained by a personal creator.  The “personal” adjective comes about since the precise value of these various constants of nature are carefully chosen to make life on earth possible (that is, fine-tuning is an example of Intelligent Design).

He then paints the picture that scientists seek to remove/explain instances of fine-tuning, because of they are uncomfortable with the associated theological implications.  However, I would like to point out that fine-tuning is often discussed in terms of æsthetic considerations.  Sometimes this is called “naturalness,” the property that the dimensionless ratios between free parameters or physical constants appearing in a physical theory should take values “of order 1” and that free parameters are not fine-tuned.

Appeals to æsthetics considerations are rather widespread in physics.  In my view, such appeals only make sense in a theistic context:  why should my conception of beauty correspond to what is going on out there?  Also, why should I expect others to share the same basic sense of beauty?  If a personal God created the universe in a way that reflects his own nature, and we are all created “in the image of God,” then an appeal to æsthetics makes perfect sense.  Otherwise, not.

Imagine that I discover that two different particles—a proton and a neutron—have almost the same mass.  (And let us say that this fact has some important implication for creation of stable atoms, and the like.)  There are two things that could happen:

  1. I could just let it be and say that this is an example of fine-tuning or I could invoke the anthropic principle, “we wouldn’t be here if it weren’t like this.”
  2. Or I might find some symmetry (in this case, isospin) that relates the two particles.

Which explanation is “better?”  Both are logically valid explanations.  Yet, we are much happier with the latter mode of explanation for æsthetic reasons.  

The associated symmetry, isospin, is one of the symmetries of the Standard Model.  One might then counter that we are just moving the target:  “Why, then, does the Standard Model have this particular symmetry?”  I would argue that we find that positing a theory to have a particular symmetry is more æsthetically pleasing than “fine-tuning” two masses to be equal.  In either case, we don’t know the fundamental reason why.  But one is certainly more beautiful than the other.

Another important example of fine-tuning comes from the isotropy of the microwave background radiation.  There are two possible explanations for this:

  1. The initial conditions of the universe were delicately balanced so that the temperature at each location was almost the same, even for points not in causal contact.
  2. Inflation

Either is a logically valid explanation.  Both explanations require very precise fine-tuning.  Both explanations are consistent with experimental observations.  Yet we prefer the latter explanation over the former explanation for purely æsthetic reasons.  It is much prettier to say that two regions in the night sky appear to be in thermal equilibrium because they actually were in thermal equilibrium some time in the past.

Finally, there may be some quantities that must be fine-tuned.  For instance, one could imagine that the overall expansion rate of the universe (which is very fine-tuned) can have no “natural” explanation (in the sense I mentioned earlier).

In conclusion, we see many examples of fine-tuning in the world around us.  However, appeals to fine-tuning must be made with care.  “Naturalness” explanations, when available, are always preferred.

Pithy saying:  “Fine-tuning is great, but should only be used as a last resort.”