I’ve elsewhere described my views on the so-called fine-tuning of the universe for intelligent life. In the course of preparing that talk, I read some internet articles that were rather woeful. It’s time to quote John Leslie again: “The ways in which ‘anthropic’ reasoning can be misunderstood form a long and dreary list”.
My first target is Dr Hugh Ross. Ross was a postdoctoral research fellow in astronomy at Caltech before founding Reasons to Believe, a Christian ministry that aims to “show that science and faith are, and always will be, allies, not enemies”.
There are two main components of Ross’ apologetic. The first is the claim that scientific truths are predicted in the Bible. I won’t discuss this point further here, except to note that Sean Carroll’s uncharacteristically dismissive rant over at Cosmic Variance is a bit harsh when he labels Ross a “crazy” “crackpot” for holding such views.
Too many hostages to fortune
Ross too often takes a scattered approach, briefly describing a large number of proposed fine-tunings. An example of this is this article on Ross’ webpage. He apparently used the same approach in his address to the Sceptics Conference. This is fine for a general overview of the subject, but not if you’re going to attempt an argument for the existence of God. Ross has no opportunity to discuss the subtleties of any particular point on the list, which leaves him open to objections. The list is also not individually referenced – all the references are in a heap at the end. This makes it very difficult to follow up on any particular point. The study of the fine-tuning of the universe is plagued by faulty logic and overstated claims, and Ross does little to reassure us that he is able to sort the wheat from the chaff. A better approach is that taken by Robin Collins, who carefully discusses what he perceives to be the six best cases of fine-tuning.
Some of the items on the list are indeed questionable. E.g. point 109 (which is similar to point 6): decay rate of cold dark matter particles. If too low: insufficient production of dwarf spheroidal galaxies, which will limit the maintenance of long-lived large spiral galaxies. If too high: too many dwarf spheroidal galaxies produced, which will cause spiral galaxies to be too unstable. The relevant paper is by Renyue Cen, who considers the problem of star-formation being observed in low-mass galaxies when CDM galaxy formation models predict that photoionisation by the UV background would prevent gas cooling. Cen suggests that the decay of dark matter particles could help: these galaxies accreted their gas in the past when they were larger, but have since lost mass due to the decay of dark matter particles.
While this is an interesting idea, it is currently nothing more than speculation – it isn’t the only possible solution to the problem; there is no unambiguous, direct evidence of dark matter decay (we don’t even know what the dark matter particles are); the paper only presents a general outline of the idea (there are no plots); in the last 9 years, the paper has received just 14 citations; and there are enough uncertainties surrounding galaxy formation that the claim that dwarf spheroidals are crucial for intelligent life is plausible, but far from established. It is thus highly questionable to claim the dark matter decay rate as a candidate for fine-tuning.
If this example of “fine-tuning” makes the list, then Ross can’t have very high standards. This calls into question all the other items on the list, most of which are outside my area of expertise (the layman’s dilemma!). What we want is a carefully considered, critically compiled collection of well-studied, well-understood examples of fine-tuning. Instead, we seem to have a list where any claim to fine-tuning, no matter how speculative or marginal, is included. Some items surely deserve a place on the list, but we have no way of knowing which ones.
The “use your imagination” objection
Ross lists a number of proposed fine tunings that seem to only affect life as we know it, rather than all imaginable forms of intelligent life. For example, point 149: time window between the production of cisterns in the planet’s crust that can effectively collect and store petroleum and natural gas and the appearance of intelligent life. If too short: inadequate time for collecting and storing significant amounts of petroleum and natural gas. If too long: too many leaks form in the cisterns, which leads to the dissipation of petroleum and gas.
It seems that the argument here is that fine-tuning is required for there to be enough petrol to run our cars. Point 150 relates to the availability of metal ores for technology. These aren’t necessary conditions for intelligent life. These are just obstacles that life in other universes would have to overcome. Contrast these points with lowering the strength of the strong force by 50%; then all the atoms used by life fall apart. Once again, Ross is spreading the case too thin, providing too many weak points.
Correlation of probabilities
Sean Carroll’s main objection to Ross is that he assigns probabilities to all the items on his list, and then “cheerfully multipl[ies] them together” to get . That’s not quite right; Ross is aware that these probabilities are not independent and so estimates the “dependency factor”, as well as an upper limit on the number of planets in the known universe. But once again, the probabilities themselves and the dependency factor are just listed. We have no idea how they were calculated, just another pile of references. Once again, we can have no confidence in Ross’ claims.
The challenge for Ross is clear. Don’t just write internet articles and popular level books. Don’t just pull amazing numbers out of a hat. Don’t present all claims to fine-tuning as equally well established (as if citing a paper settles the issue). Get together with some of your contacts who are still in science, write a review article, and have it published in something like Annual Review of Astronomy and Astrophysics. You have clearly done a tremendous amount of research, and are familiar with a great deal of the wide-ranging scientific literature on this subject. So do what Barrow and Tipler did: provide the definitive, carefully argued, comprehensive review of the fine-tuning of the universe for intelligent life. Show us that you are prepared to reject dubious claims, and can bring clarity to the many subtleties of this subject. Then, maybe, we’ll let you speculate on the divine.
More of my posts on fine-tuning are here.