1. The Planetary Fission Model
One theory, favored
in the pre-Apollo era, was that the Moon and the Earth “fissioned”
or split apart in the early years of the planets’ formation, with
the Moon emerging from what is now the Pacific basin, and settling
into its current orbit. This would entail enormous difficulties of
celestial mechanics that simply pile up too many coincidences. For
example, the Moon exists in a nearly perfect circular orbit around
the Earth, an orbit that, moreover, allows only about 60% of the
Moon’s surface — the same side — to be visible from the Earth, even
though the Moon, like the Earth, rotates around its own axis.
Additionally, the Moon exists at the precise distance from the
Earth that allows it to totally eclipse the Sun. A “fission” model
would, moreover, imply that the Moon’s orbital mechanics around the
Earth would of necessity be rather more elliptical than they
are.
But there is a final
difficulty, one that proved fatal to the “fission” model after the
first Apollo Moon landings returned with rocks from our celestial
neighbor. For the fission model to be true, the age of rocks on the
Moon would have to be of similar antiquity to the Earth itself, yet
rocks and soil were discovered on the Moon that were some
billions of years older. The oldest
rocks found on Earth are some 3.7 billions of years old, while
rocks returned from the Apollo missions dated from 4.3 to 4.6
billions of years old, while one rock even dated to some 5.3
billions of years old. This fact is made the more curious because
the area of the Moon from whence they originated was thought to be
one of the geologically youngest on that planet!