On 17 Jun, 2011 By Anonymous (not verified)
Ralph Baldwin was a native of Michigan and a graduate of the University of Michigan. Due to a position as a part-time planetarium lecturer, he developed an interest in lunar topography. During the 1940s, he formulated the principles of current lunar geology: that lunar craters are the result of impact events, not volcanism; that the lack of active lunar erosion means that the craters are very old; that Earth should have been bombarded in the same way; and that there should be impact structures, large and small, still preserved on Earth.
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