Theories of the Moon: Looney Tunes?

first_imgThe TV science channels tell it like a matter of fact: our Moon originated from the coalescing debris of a glancing impact with Earth from a Mars-sized object, sometime long ago.  They even have computer animations to show how it all happened.  How reliable is this theory, though?  This month’s Planetary Report from The Planetary Society contains some sobering qualifiers from Dave Stevenson, a professor of planetary science at Caltech. In many respects, our Moon is the best-studied body other than Earth…. If we have already learned so much, what do we expect to gain by going back? …. I argue … that we really don’t understand the Moon very well, and that it is a body the understanding of which features prominently in our attempts to figure out what took place when the planets formed.The Apollo program and subsequent research revealed that our Moon is an oddball.What’s wrong with the standard story of the Moon that we need more explanation to fix the story?  … Part of the answer lies in something that often happens in science: we have a story that is widely accepted, but it is a story that is actually incomplete and poorly tested.  To some extent, the so-called giant impact origin of the Moon has gained acceptance through the failure of alternatives rather than through its evident correctness.Several alternatives to the impact origin have been proposed…. All these alternatives have very major and extensively studied shortcomings.  This is, however, not the same as saying that we know for sure that the giant impact happened—it simply seems more likely than rival hypotheses. Stevenson referred to the recent finding of activity on the surface (see 11/09/2006) as an indication that the moon’s interior must still be hot.  Though he pointed to a few indirect evidences in support of the leading theory, the tone of his article is that the gaps in our knowledge are still large – even after the Apollo missions make the Moon “the only body (other than Earth) for which we have rocks of known provenance.”  And if we can’t get the Moon right, what does that say about our theories for the origin of the rest of the Solar System?  See also the 01/26/2007 entry.Stevenson’s candor was refreshing, even if it contains an ulterior motive for justifying the Planetary Society’s lobbying for new lunar missions.  Just remember these doubts the next time the news media give the impression that we have our tidy theories all locked up.  The best theory is not ipso facto a good theory – see Best-in-Field Fallacy in the Baloney Detector.  Remember also something Dr. Kevin Grazier (JPL) said in the film The Privileged Planet: “if our moon didn’t exist, neither would we.”(Visited 11 times, 1 visits today)FacebookTwitterPinterestSave分享0last_img

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