... The Round Earth . ... Some of the names he used for the Moon's crater are of persons discussed in "Stargazers"-- Tycho (distinguished by bright streaks that radiate from it), Ptolemy ("Ptolemaeus"), Copernicus , Kepler , Aristarchus , Hipparchus , Erathosthenes ; Meton and Pythagoras are on the edge, near the northern pole. ... Those moons display " palimpsest" craters which are merely surface markings, because as time passed, the walls which originally existed sagged back onto the flat surface. ...