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neilepquote from here http://www.fourmilab.ch/earthview/moon_ap_per.htmlseeA Different Point of ViewYou may have noticed while examining the pictures above that the two images of the Moon differ not only in size, but in the position of features on the disc of the Moon. This might seem puzzling in light of the frequently-stated assertion "the Moon always keeps the same face toward the Earth". But this generalisation is not strictly true; in fact, the combination of the eccentricity and inclination of the Moon's orbit causes the Moon, as seen from the Earth, to nod up and down and left and right. These apparent motions, the lunar librations, allow us to observe, over a period of time, more than 59% of the Moon's surface from the Earth, albeit with the terrain in the libration zones near the edge of the visible disc, only very obliquely.