Testing the Green-Cheese Theory of the Moon

Edward Schreiber and Orson Anderson once tested whether the Moon really could be made of green cheese. Caltech planetary scientist David Stephenson discussed that achievement, in Box 1 of his article in Physics Today in November 2014. In their 1970 article in the journal Science, Schreiber and Anderson compared the speeds of sound waves in rocks that were returned from the Moon with measured sound speeds of various terrestrial materials, including various types of cheese. (Sound speeds correlate highly with density and are thus often used to try to infer the composition of rocks.)

Table from E. Schreiber and O.L. Anderson (Science, 1970) comparing the sound speed of various Moon and terrestrial materials.
Table from E. Schreiber and O.L. Anderson (Science, 1970) comparing the sound speeds of various Moon and terrestrial materials.

According to these data, the sound speed from lunar materials seems to be much closer to those of terrestrial cheeses than of terrestrial rocks. However, one should look at Stephenson’s excellent article to read about more serious hypotheses about the origin of the Moon.

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