How did the moon form? Nobody quite knows with absolute certainty. The creationists think they know – Goddidit – and they think that any other attempt at the answer is baloney. Hence Moday’s article from Brian Thomas, Impact Theory of Moon’s Origin Fails, which opens:
Secular scientists used to regard the planetary collision theory as a triumph in explaining several of the moon’s specific arrangements. But newfound facts severely debilitate this lunar impact origins theory.
According to this new theory, an early Earth collided at a glancing angle with a planet that was one or two times the mass of Mars. Some of the debris launched into orbit around Earth and somehow collected to form the moon. This could explain the moon’s peculiar orbit and some of its other properties. But, as Bob Jones University astronomy professor Ron Samec noted, recent studies refute even this origins scenario.
Primarily we’re talking here about the “[giant] impact hypothesis” – which is not “new,” being first proposed in 1975 – but Thomas quickly veers off into older, more obviously false theories. What he’s got are two sources, citations ¹ and ² in his article. The second, which he spends the most time talking about, is a paper published in August by the aforementioned Ron Samec in Creation Ministries International’s Journal of Creation, called Lunar formation – collision theory fails. The JoC tends to wait for a while before releasing pdfs of its articles into the wild, so I don’t so much as have a link for you. CMI’s website does have a summary, but it doesn’t go into much detail – if there is indeed any at all. Thomas does the same – here’s a sample paragraph:
A replacement moon origins story told how Earth’s gravity somehow “captured” a large object that would become the moon as it was flying nearby. Even the secular community now agrees that this is not the answer. Samec commented, “One major problem with this idea is that capture is an extremely rare event.” Also, such a capture would have produced a highly elliptical lunar orbit, not the nearly circular one it actually has.
You get the idea – shocking new findings from an elite creation scientist these are not, but instead merely a summary of the “reasons why three older naturalistic lunar origins stories had failed.”
Source number one, on the other hand, is to a news article published in Science earlier this month, by Daniel Clery and titled Impact Theory Gets Whacked. I can’t find a pdf of this for you either, I’m sorry, but a podcast including a segment in which “Dan Clery talks to Sarah Crespi about new explanations for the formation of the moon” does exist (it starts at 9 minutes 30 seconds in, running until 19:15 and covers many of the topics of Clery’s article). This article, for it’s part, begins:
Among many other contributions to science, the Apollo space program gave geophysicists a grand unified theory of the origin of the moon. The story goes like this: A few tens of millions of years after the birth of the solar system, a now-vanished planet roughly the size of Mars struck Earth a glancing blow that shattered them both and sprayed nearby space with debris. Earth reformed itself; the debris settled into a disk around Earth, which accreted into the moon. The giant impact scenario, based in large part on careful study of the 382 kilograms of moon rocks astronauts brought back between 1969 and 1972, was a triumph of planetary science.
But the truth may not be that simple.
(If you were wondering when I was going to give a better explanation of what the impact hypothesis is all about than Thomas did, this will have to do.) The “Whacked” title is a slight exaggeration – we’re not actually talking about a specific new finding that challenges the hypothesis, but instead the rising perception that it is unable to explain all of the evidence we have on hand.
The impact hypothesis, in its canonical form, is very good at explaining properties of the moon like its orbit and angular momentum. But it turns out that it is unable to explain why the isotope ratios found in moon rocks brought back by the Apollo missions should be so similar to those found on Earth. In short, from what we know about the solar system, isotope ratios differ depending on where you are: the impactor should have formed with a different signature to the Earth. While a level of admixture would have taken place during the impact itself, this is not as much as was believed before they were able to model the process with computers: the moon comes out being made of about 80% impactor despite the other planetesimal not bringing nearly that large a proportion of the mass to the table.
Daniel Clery was at a conference recently were these issues were discussed, along with potential modifications and/or replacements of the hypothesis. The ideas being tossed around are not yet fully formed, and much discussion was had about their own potential flaws. Thomas, as you might have guessed, mentions none of them, but they are worth looking at.
One option effectively allows the Earth and proto-moon to continue mixing for as long as a thousand years after the impact, potentially allowing them to become indistinguishable:
[David] Stevenson and [Kaveh] Pahlevan suggested one such scenario in their 2007 paper [in which they demonstrated that Earth and the impactor could not have the same isotopic signature, even if they formed in the same part of the solar system – Earth’s much larger size would have meant that it took material from a wider area]. They point out that the heat generated by the giant impact would produce an Earth and a debris disk made of molten and vaporized magma. They calculate that this superheated, churning inferno would take between 100 and 1000 years to cool. During that time, they argue, enough turbulent mixing and diffusion could take place between disk and Earth for them to reach an equilibrium, resulting in a homogeneous Earth and moon.
This is unlikely to be sufficient, however, as it may not have been able to mix the two bodies enough. A second idea posits that the impactor was much smaller than thought, moving much faster and hitting Earth much more quickly. This produces the correct level of admixture, as most of the material now comes from Earth, but we land up with too much angular momentum. The proponents of this idea, Matija Ćuk and Sarah Stewart, have an explanation for this too:
Soon after the moon forms and as the Earth-moon system is evolving toward its current state, the moon’s perigee—the point at which its orbit brings it closest to Earth—moves around Earth in a cyclic motion called precession. The cycles get longer and longer until the rate of precession slows to once per year. Then the precession becomes locked in a fixed position relative to the sun—a rhythm known as evection resonance. As a side effect, the resonance transfers angular momentum from the moon to the sun, in effect spinning up the sun while slowing down the moon. Evection has long been known, but most researchers thought the moon would not stay in the resonance for long. Ćuk and Stewart say that in their particular scenario, it could last long enough for the moon to shed half its angular momentum.
But would it last that long? Some disagree – we may need better computer models to determine who is right. Another idea, instead increasing the size of the impactor to similar to the Earth, has the same problem.
Another potential solution revisits the assumption that got us to question the impact model in the first place: do isotope ratios really vary that much throughout the inner solar system that the impactor would be so different to the Earth? Our present theories here are based largely on the differences between Earth and Mars. If we knew would Venus was like, however, we could test how well they apply to other bodies.
That explains why at the London meeting, when the session chairs jokily asked each speaker what single measurement they would most like to perform, many said they would like to examine a piece of rock from the planet Venus. Venus is Earth’s rogue twin, and together the two planets contain 80% of the mass between the asteroid belt and the sun. If it turns out that Venus has very similar isotope ratios to Earth, then it is much more likely that an impactor might have had them as well. “Venus is the key,” Stevenson said.
The beginnings of all attempts to explain apparent one-off events like the formation of the moon are going to look a little ad-hoc at first – and ripe for misrepresentation by creationists as a desperate attempt to explain the universe without God. What we need is a hypothesis that explains all of the evidence we have on hand, and then test it by gathering more. This latter step looks like it may involve a return to both Venus and the moon, which suggests that they might have quite a while to complete the former.
Having finished his own summary of the salient points of Samec’s paper, Brian Thomas says:
But one theory still accommodates all the data. If God created the moon in a supernatural event, then that would explain its many specifications directly related to life on Earth, including its peculiar size, mass, orbit, angular momentum, composition, and density. This evidence confirms God’s Word, which says, “God made two great lights: the greater light to rule the day, and the lesser light to rule the night.…And God saw that it was good.”
The issue here is that the bible could just as easily “explain” the moon if it was a giant purple doughnut. This is what some people call a “science stopper” – it purports to explain everything, yet tells us nothing save that we should give up and go home. Creationists cannot even point to a Bible verse where it says that God made the Earth and moon out of the same stuff, but Mars out of something different and you wont believe what He did to Venus.
Or rather they could, based on what they’ve said in the past. You may remember a previous moon-related article from Thomas, wherein he claimed that discoveries that the moon was mildly damp being evidence of how God supposedly made everything “out of water” (a probable misinterpretation of the relevant verse) before turning it into what it’s made of now. If the observed isotope ratios were different, in that they were the same between planets, I can easily see them using the same sorry excuse for logic to announce that this too was evidence that God made all the heavens in the same way. But they are not the same, and so they do not. Just a thought.
Thomas concludes his article with references to some other arguments he and others have made about the moon in the past, before saying:
Common-sense inferences, not only from failed hypotheses, but also from straightforward observations, continue to confirm the moon’s supernatural origin.
Because every time a theory that’s not theirs takes a hit, it’s support for young Earth creationism. And their own ideas cannot be harmed, because God can do anything he likes. Such is creationist science reporting.