The Fine Tuning and Design of the Moon's Formation
by Rich Deem

Moon Formation

The giant impactor model for the formation of the Moon was originally thought to have solved the problem of the Moon's formation. However, recent computer models show that the models cannot account for all the characteristics of the Earth and Moon (Earth's rotation and similarity of the composition of the Earth and Moon). The fine tuning required has led some scientists to "philosophical disquiet."

Rich Deem


Atheists like to claim that there is no evidence of fine tuning or design in the universe. Increasingly over time, the evidence has shown that the nature of the universe, our solar system, and our planet demonstrate exquisite levels of fine tuning. The formation of the Moon has been a mystery since early in the 20th century. Following the Apollo missions to the Moon, scientists proposed the theory that a large impactor had collided with the proto-Earth, forming a debris disk that coalesced to form the Moon.1, 2 The large impact model seemed to have solved all the problems about how the Earth had received such a large moon. However, as computers have become faster and measurement techniques more sophisticated, scientists have attempted to refine the model, which have shown that all impactor theories suffer major inconsistencies with the known facts, thus requiring extremely unlikely fine tuning to correct the deficiencies. Scientists have begun to acknowledge these inconsistencies and the implications (fine tuning or the dreaded d-word—Design) which leads them to "philosophical disquiet."

Initial lunar formation theories

Initial theories about how the Moon formed fell into three varieties. The capture theory stated that early in the solar system's history, the Moon was ejected from its original orbit around the Sun (due to gravitational interactions) and was captured by the Earth. Even at the time it was proposed, scientists knew that there was no realistic way for the Earth to gravitationally capture an object as large as the Moon. The accretion model said that the Earth and Moon formed at the same time, together, during the original accretion process that formed the solar system.  However, scientists already knew that two planets could not form in the same location, since any objects located in the same orbit would soon merge together. The fission model said that the initial angular momentum of the Earth's rotation was fast enough to cause a piece of the Earth to bud off, forming the Moon.3 The problem with such a model was that the rotational speed required to cause fission was way too fast to account for the current angular momentum of the Earth-Moon system (which is only 27% of that required for the fission process to have occurred).

After the Apollo missions to the Moon, scientists realized that the composition of the Moon's crust was very similar to that of the Earth's, suggesting that the Moon had, indeed, come from the Earth. However, the angular momentum problem required a different solution than fission. So, in 1975 and 1976, scientists developed the giant impact model,1, 2 in which the Moon was produced as the result of a slow, glancing blow from a Mars-sized body (about 10–15% of Earth's mass) on the proto-Earth. The collision caused the Earth to spin rapidly (about once every five hours), with the Moon orbiting close to Earth (about 8,000 miles). Subsequent gravitational interactions caused the Moon's orbit to expand and Earth's rotation to slow to our current 24-hour day. This giant impact model was consistent with the Moon's mass, its lack of iron, and the angular momentum of the Earth–Moon system. The model fit the known characteristics of the Earth-Moon system so well that it was immediately adopted, almost universally, by the astronomical community.

Cracks in the model

The giant impact model survived unscathed for years, until high precision isotope composition techniques were developed and used on the lunar samples, and scientists began to analyze the composition of Mars and Vesta meteorites. The data showed that the meteorites had vastly different isotopic compositions compared to rocks from the crust of the Earth. However, the lunar rocks returned from the Apollo missions had virtually identical isotopic signatures compared to Earth rocks for isotopes of oxygen,4 chromium,5 titanium,6 potassium,7 and silicon8 and hydrogen (water)9 (see graph for oxygen isotopes, right). The isotopic compositions of the planets and meteorites are important, because they suggest that the impactor and proto-Earth originally probably had vastly different isotope ratios. The problem with the giant impact models is that in order to produce the proper angular momentum of the Earth Moon system, the collision would be expected to produce a Moon that was composed of about 80% collider and only 20% Earth.10 Even if the composition of the proto-Earth and collider were only marginally different, those differences would be expected to be found in the isotopic composition of rocks from the Moon.

"Solutions" to the problem

Most scientists realize there is no way to resurrect the fission or capture theories, so they have attempted to fine tune the collision theories in order to produce the required Earth-Moon dynamics and compositions. One scenario required two extremely unlikely collisions (instead of just one). The first collision got the Earth spinning so fast its day is just 2-2.5 hours long. A second collision ejected a large amount of the Earth's mantle, due to its high rotational speed, forming the Moon.11 However, to slow the Earth's rotational speed to current values, the scientists had to appeal to a special resonance between the lunar precession period that exactly matched the one-year period of Earth's orbit for a significant length of time. The special pleading of unlikely, long-lived resonances makes the model extremely unlikely to have occurred by chance.

Alone in the Universe: Why Our Planet Is UniqueA second new model involves the collision of two impactors that are roughly the same size, forming the Earth and the much smaller Moon.12 Like the previous model, this model requires long-lived resonances between the Earth's orbital period and the lunar precession. In order to account for isotopic abundances of silicon and tungsten, which interact with metals, both models require that the impactor's iron core remained intact as it descended through Earth's mantle. Mixing of the metallic core material of the collider with the Earth's mantle would have altered the composition of the Earth.

Another giant impact theory used a complicated three-stage lunar accretion model in order to claim that the majority of the collider (now Moon) was buried under a thin veneer of Earth-like material.13 However, some of the rocks returned by the Apollo missions consisted of volcanic samples that had originated hundreds of kilometers below the lunar surface,14 making the model at odds with the data.

The main problem with giant impact theories is getting enough proto-Earth material into orbit to account for the similarities between the Earth and Moon. One paper has come up with a unique "solution" to the problem—a giant nuclear explosion.15 The energy needed to accomplish this feat would be the equivalent of 12 billion of the largest hydrogen bombs ever developed. Such an explosion would have required fully 5% of all the fissionable material of the Earth to be concentrated in a small area (a few hundred square kilometers) near the surface of the Earth. According to the theory, a 100 km diameter asteroid landed exactly at the location of this material, setting off the nuclear chain reaction. This model did not account for the extreme fine tuning mechanism required to get such a high concentration of fissionable material in one place or the precise impact location required to set off the chain reaction.

Scientists' quotes

Planetary scientists are struggling with lunar formation models, because they none of them explain how the Earth and Moon came to be without appealing to an extremely unlikely series of events. Robin Canup says:

It remains troubling that all of the current impact models invoke a process after the impact to effectively erase a primary outcome of the event—either by changing the disk's composition through mixing for the canonical impact, or by changing Earth's spin rate for the high-angular-momentum narratives.

Journey Toward Creation DVDThe introduction to Robin Canup's article, Planetary science: Lunar conspiracies, states:

"Current theories on the formation of the Moon owe too much to cosmic coincidences, says Robin Canup"16

In another article, entitled, Planetary science: Shadows cast on Moon's origin, Sarah T. Stewart says:

Ultimately, the current detailed interrogation of lunar origin may demand answers that have an unexpected level of complexity.17

"Coincidences" and "complexity" are just code words in place of "design," which is why these scientists find the data "troubling." Tim Elliot also seems troubled, although he used the catchy phrase "philosophical disquiet":

"The sequence of conditions that currently seems necessary in these revised versions of lunar formation have led to philosophical disquiet."17

Robin Canup sums up the "problem":

But it remains unclear whether the resonance mechanism needed to slow Earth's rotation in these more extreme scenarios is likely or requires an improbably narrow range of conditions. In other words, is the origin of our Moon a rarer event than we believed, or are we missing something?16

If one's philosophy requires purely materialistic explanations, the more fine tuned those explanations, the more unlikely they would have ever occurred by chance. Yes, Robin, you are "missing something," or more correctly, Someone—the Designer of the universe.

Conclusion Top of page

Previous scientific studies had shown that collisions like those that might have formed the Moon are rare in stellar systems.18 Even so, the giant impact theory seem to have solved the "problem" of the Moon's formation for a number of years. However, now that isotopic fractionation technology has been perfected, scientist are discovering that all giant impact theories fail to account for the amazing isotopic similarity of the Earth's and Moon's crust. High impact theories that might account for collider-Earth mixing produce angular momentum that is too high for that observed in the Earth-Moon system. Lower impact theories that match the Earth-Moon angular momentum produce two bodies of vastly different compositions, in conflict with the facts. Hybrid or wildly improbable theories have been developed to try to reconcile the known facts. However, these theories require extraordinary levels of fine tuning or design in order to work. Is it possible God stepped in and specifically designed the Earth and Moon to provide a suitable place for us to live?

Rare EarthRare Earth: Why Complex Life is Uncommon in the Universe by Peter D. Ward and Donald Brownlee

A secular book that recognizes the improbable design of the Earth. Paleontologist Peter D. Ward and astrobiologist Donald Brownlee examine the unusual characteristics of our galaxy, solar system, star, and Earth and conclude that ET may have no home to go to. Surprisingly, the authors conclude that the amazing "coincidences" are the result of good luck and chance.

The Creator and the CosmosThe Creator and the Cosmos by Dr. Hugh Ross

A classic book for modern Christian apologetics and science. Dr. Ross presents the latest scientific evidence for intelligent design of our world and an easy to understand introduction to modern cosmology. This is a great book to give agnostics, who have an interest in cosmology and astronomy.

References Top of page

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