We live at the exact moment in Earth’s extensive history when perfect solar eclipses, such as the event of August 21, 2017, are possible. These eclipses occur because the apparent disc of the Moon and the apparent disc of the Sun are virtually identical. Much earlier or much later in geologic history the moon would be either too close or too distant from earth because the Moon’s orbit is very slowly spiraling away from Earth. Contemporary eclipse events have enabled humanity to make many important physical discoveries concerning our Solar System, the universe, and the laws of physics. Scientists are reminded of this fact each time a total solar eclipse occurs. Understandably, laypeople bask primarily in the splendor of the event.
Early models of Moon formation failed to explain its existence. Decades ago I proposed models of moon formation to my students without much confidence that any model was true. The models ranged from highly unlikely to impossible. Astrophysicist Hugh Ross has commented, concerning the proposals of early theorists, “In their frustration some researchers went so far as to comment that the Moon must be some kind of illusion—or, perhaps, a miracle.”
Ross’s previously cited volume Improbable Planet uses the effective imagery of a home building project in which the owner and builder both insure that all the conditions for building a new home meet all the “just right” criteria. Home building is not an opportunity to pray for a sequence of “lucky accidents.” We repeat a quote from Ross concerning how “…the Moon’s formation nevertheless represents an intricately layered sequence of coincidences that happened to prepare Earth for life—advanced life, especially.” We quote the nine points made in Ross’s “brief list of what the (Giant Impactor) collision accomplished:”
“1. The collision replaced Earth’s thick atmosphere, providing in its place an atmosphere with optimal (for life) chemical composition, appropriate (for life) heat-trapping capacity, appropriate transparency for efficient photosynthesis, and precise air pressure for making possible the eventual operation of lungs.
“2. Earth’s mass and density were augmented, enabling Earth to retain (via its gravity) a large, but not too large, quantity of water vapor for billions of years.
“3. The amount of iron in Earth’s core increased, bringing it closer to the level needed to provide Earth with a strong, enduring magnetic field (the remainder came later) to shield Earth’s future life from deadly cosmic rays and solar X-rays and to prevent the sputtering away of Earth’s atmosphere.
“4. The collision delivered iron and other critical elements to Earth’s core and mantle in just-right ratios to produce long-lasting, continent-building plate tectonics at levels just right for life.
“5. The quality of iron delivered via the collision to Earth’s crust was just right for supporting an abundance of ocean-dwelling phytoplankton that, in turn, supports the entire oceanic food chain and also provides oxygen for advanced terrestrial life.
“6. Earth’s interior was salted with an abundance of long-lasting radioisotopes, the heat from which drives most of Earth’s tectonic activity and volcanism.
“7. Earth’s crust and upper mantle were peppered with just-right quantities of HSEs (iron loving elements)—not so much as to prove poisonous to (later) life but to sustain myriad plants and animals, as well as to allow for the eventual launch and maintenance of global high-technology civilization.
“8. The collision produced a moon with sufficient mass to stabilize Earth’s rotation axis tilt, protecting the planet from rapid and extreme climatic variations.
“9. The resulting Moon also gradually slowed Earth’s rotation rate to a life-sustaining level.”
The concept that home building projects must manifest near-perfect perfection is analogous to the idea that Planet Earth benefits from a divinely designed sequence of events with respect to the formation of Earth’s lunar companion. The story of the Moon reveals not merely a catalog of its physical characteristics but also how the Moon provides for life on Earth. We are mindful of this provision as we observe the glory of the total solar eclipse on August 21, 2017.