Apologies for the blogging drought. More soon. I couldn’t help but comment on something in the news recently.
Doing the rounds this week is a Wall Street Journal article by Eric Metaxas titled “Science Increasingly Makes the Case for God“. A few thoughts.
“Today there are more than 200 known parameters necessary for a planet to support life—every single one of which must be perfectly met, or the whole thing falls apart.”
I’m really hoping that his reference for the “200” parameters isn’t Hugh Ross, whom I’ve commented on before. The fine-tuning of the universe for intelligent life is about the fundamental parameters of the laws of nature as we know them, and there are only about 30 of those. Also, exactly zero fine-tuning cases require a parameter to be “perfectly” anything. There is always a non-zero (if sometimes very small) life-permitting window.
The fine-tuning for planets is a bit of a non-starter. How many planets are there in the universe? We don’t know, because we don’t know how large the universe is. There is no reason to believe that the size of the observable universe is any indication of the size of the whole universe.
Without a massive planet like Jupiter nearby, whose gravity will draw away asteroids, a thousand times as many would hit Earth’s surface.
This turns out to be a bit of a myth, however widely reported. Jonathan Horner and Barrie Jones used a set of simulations to test this idea, but their results tended to show that the opposite might be true.
The fine-tuning necessary for life to exist on a planet is nothing compared with the fine-tuning required for the universe to exist at all.
Nothing in science explains why the universe exists at all, let alone fine-tuned values of constants. I’ve explained this before here and here. Fine-tuning for life to exist at all is, however, and interesting kind of fine-tuning. I think that’s what Metaxas is referring to.
Astrophysicists now know that the values of the four fundamental forces—gravity, the electromagnetic force, and the “strong” and “weak” nuclear forces—were determined less than one millionth of a second after the big bang.
Not really. This would be a prediction of a combination of inflationary theory and a grand unified theory. So … maybe, but not exactly the most settled physics. In any case, this is of little relevance to fine-tuning, unless you’ve got multiverse scenario in mind.
If the ratio between the nuclear strong force and the electromagnetic force had been off by the tiniest fraction of the tiniest fraction—by even one part in 100,000,000,000,000,000—then no stars could have ever formed at all.
OK. I have no idea where that number comes from. And I’ve written a review article on this field. A parameter cannot be fine-tuned to a greater degree than it has been measured – otherwise, the fine-tuning would constitute a more accurate measurement. The strength of the strong force is only known to about 2% (technically, strong coupling constant at mass scale of Z boson.)
In one of his books (“Other Universes”, I think), Paul Davies states that the weak force is fine-tuned to one part in 10^40 (or 10^100 in another of his books). This is a statement about the vacuum state of the Higgs field (electroweak). This is essentially the cosmological constant problem, put rather oddly.
Alternatively, Metaxas could be thinking of charge neutrality. If the universe were very slightly charged, electromagnetic forces would always win over gravity, so not stars, planets etc.
In any case, give a reference!
The annoying thing is that there are plenty of scientifically correct cases on which Metaxas could have based his claims. Whether it proves God is another question, but he could at least get the science right.
Enter Lawrence Krauss
In response to this article, Cosmologist Lawrence Krauss wrote a letter to the editor. He didn’t do much better than Metaxas.
We currently DO NOT know the factors that allow the evolution of life in the Universe. … The mistake made by the author is akin to saying that if one looks at all the factors in my life that led directly to my sitting at my computer to write this, one would obtain a probability so small as to conclude that it is impossible that anyone else could ever sit down to compose a letter to the WSJ.
Conflates “we don’t know everything” with “we don’t know anything”. There are clear fine-tuning cases. With a relatively small tweak to the cosmological constant or the quark masses, we can make universes with no atoms, or one hydrogen atom per observable universe, or that last only a fraction of a second before recollapsing. In these cases, the details of which chemical reactions first formed life on Earth aren’t particularly relevant. We know enough, even if there is a lot more we’d like to know about life.
The “sitting at my computer” analogy is anything but apt. When does a small likelihood punish a theory sufficiently that an alternative theory should be preferred? Go use Bayes’s Theorem! This part of Metaxas argument is actually valid – if the premises are true, an interesting conclusion follows. (Make sure you understand the difference between valid and true before commenting on that sentence.)
We have discovered many more planets around stars in our galaxy than we previously imagined.
Relevant to fine-tuning for planets, but not for life at all. This is why Metaxas discussion of planets is a non-starter.
The Universe would certainly continue to exist even if the strength of the four known forces was different. It is true that if the forces had vastly different strengths (nowhere near as tiny as the fine-scale variation asserted by the writer) then life as we know it would probably not evolved.
Again, the force strengths have nothing to do with the existence of the universe. But Krauss’s statement that the force strengths could be “vastly different” contradicts most of the literature and is completely indefensible. See Figure 6 of my paper.
This is more likely an example of life being fine-tuned for the universe in which it evolved, rather than the other way around.
Again, a statement without justification in the scientific literature, unless Krauss is referring to a multiverse.
It’s annoying that both “sides” get the science wrong. Someone should set them straight. Perhaps someone should write a popular-level book on fine-tuning. With an astronomy professor. Perhaps a draft is nearly done …