Lunar Libration
No two full Moons are exactly alike. To prove it, Laurent Laveder spent the last two years taking pictures of every full Moon over his home in France, and here is the result:
  The Moon rocks and rolls, shrinks and swells, never presenting precisely the same face twice. "In the full-sized animation, you'll see 2 years condensed in only 2 seconds!" says Laveder. "Sorry for the mal de mer."
Wait a minute. Didn't they teach us in school that the same side of the Moon always faces Earth? Yes, but that's only approximately true. Because the Moon's orbit is slightly elliptical (5%) and slightly tilted (5°), we view each month's full Moon from a slightly different distance and angle. The rocking motions are called libration; because of libration we can observe not just 50% but rather 59% of the Moon's surface.