On Feb. 2, Bill O'Reilly said this:
In this clip O'Reilly defends a statement he made previously about there being no explanation for the tides (other than God's influence), after being told that the moon's gravity causes the tides. O'Reilly: "OK, so how'd the moon get there?" He challenges "pinheads" for an explanation.
We took that to mean us, so we decided to help him out.
Bill Hartmann, an astronomer at the Planetary Science Institute in Tuscon, Arizona, proposed "the giant impactor hypothesis" of the moon's formation back in 1975. Computer simulations and lunar samples have since lended a great deal of support for the theory, which is now favored by most planetary astronomers.
The giant impactor theory holds that a Mars-sized asteroid impacted Earth when it was young, making a glancing blow that knocked off mantle debris. That debris eventually coalesced to form the Moon. This theory accounts for the lack of an iron core inside the moon (since it formed from lighter surface material), for its density, and for its chemical composition. The events described by the theory have also been recreated successfully in computer simulations.
O'Reilly is right in the sense that there is not universal consensus on the theory of where the moon came from, since certain aspects of the story of its formation are still not completely understood. However, Life's Little Mysteries doesn't think the details of the physics are quite what O'Reilly was asking about. Nonetheless, we would like to refer him, and anyone else, to "Where Did the Moon Come From?", a 2005 article by Princeton University astrophysicists Edward Belbruno and J Richard Gott III, for a thorough treatment of the question.
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