The Origin of Our Moon

Probably in no branch of the sciences is there such misuse of the term theory as in astronomy. This misuse finds its way into science magazines, TV and radio broadcasts, science news web sites, and even encyclopedias. Many of the conjectures about the solar system's formation are bantered as theories when they really are insufficiently scrutinized hypotheses. I think the Big Bang has adequate evidence to be labeled rightly as a theory, and that our solar system having formed out of a condensing cloud of interstellar gas that swirled increasingly faster as it condensed is also an acceptable theory. Why? Partly because of data obtained by direct observation of our universe provided by ground based observatories and space deployed observational devices like the Hubble Space Telescope coupled with mathematically solid theoretical mechanical models. In other words, we seem to have a pretty secure grip on the big picture, but the details are still fuzzy. We do not seem to have a firm grip on the details of our own solar system's formation (a lot can happen in some 5 billion years). If we can get some direct observational evidence of other solar system's planets and their satellites forming (and we will) coupled with what we have gathered from our solar system exploration then we will be in a position to make comprehensive and specific theories instead of shaky hypotheses. In this paper I want to look at various popular hypotheses of the Moon's formation and in particular the newest Collision Theory in an attempt to point out what I think are its possible shortcomings. Prior to the 1970s, there were three main theories regarding the origin of the Moon (Encarta, 2001). The first involved a fission event, in which the Moon broke off from a rapidly spinning Earth. The second theory, a co-formation theory proposed that the Earth and Moon formed contemporaneously as a gravitationally bound pair. The third theory suggested that the Moon formed as an independent planetary body that was later "captured" by the Earth during a close pass. Supposedly each theory had deficiencies; for example, it was proclaimed difficult in both the capture and co-formation models to account for the lack of a large lunar iron core, because both predicted that the Moon formed from the same mix of materials as the terrestrial planets, which typically contain a more substantial abundance of iron. I can't help but …