We Never See This Side of the Moon

Every person who has ever lived has seen the same face of the Moon. More than forty percent of it never turns toward Earth at all. We start with the real sky over La Palma before dawn on 6 November 2026, where a thin crescent Moon rises in the east, placed and lit where JPL Horizons puts it, with its night side glowing faintly in earthshine. Then why we only see one face: the Moon turns once for every trip around Earth. Its wobble (libration) is computed for November 2026 from JPL Horizons, and the part of the Moon that faced Earth on at least one day between 2026 and 2045 is computed from the same data: a little less than sixty percent. Why the "dark side" is not dark: at the new moon of 9 November 2026 the far side stands in full sunlight. Then the first look (Luna 3, 7 October 1959); Apollo 8 behind the Moon on Christmas Eve 1968, the radio silent, and the real Earthrise photograph; the two faces, the thicker far-side crust and the South Pole-Aitken basin, about 2,500 km wide; GRAIL's 2025 finding that the near side flexes more in Earth's tides and is warmer inside; Chang'e 4 on the floor of Von Kármán crater, seen from orbit by NASA's Lunar Reconnaissance Orbiter; Chang'e 6's far-side samples (lava 2.8 and 4.2 billion years old, volcanoes active for at least 1.4 billion years, a cooler mantle); and a sky with no Earth in it. Sources: NASA Science, Moon facts and tidal locking pages (one side always faces Earth; all the large moons in the solar system are tidally locked; crust about 40 km thick on the near side and up to about 60 km on the far side; maria filled with lava); NASA Moon phases page (libration in longitude and latitude); NSSDC, Luna 3 image page (first far-side image 7 October 1959, 29 photographs covering 70% of the far side, a striking lack of maria); NASA, Apollo 8 mission details and "50 Years Ago: Apollo 8 in Lunar Orbit" (loss of signal behind the Moon, the first humans to see the far side, signal expected back after 32 minutes 37 seconds if the burn worked; Earthrise, 24 December 1968); NASA Photojournal, "The Moon's Largest Impact Basin" (South Pole-Aitken, about 2,500 km, nearly a quarter of the Moon's circumference); Garrick-Bethell & Zuber 2009 via Sasaki et al., JpGU 2010 (basin centre 53.2 S, 191.8 E); Park et al. 2025, Nature, "Thermal asymmetry in the Moon's mantle inferred from monthly tidal response" (GRAIL; a nearside thermal anomaly of roughly 100-200 K); LROC (Chang'e 4 landed 3 January 2019 in Von Kármán crater, 186 km, at 45.457 S, 177.589 E; the lander about two pixels in the limb view; data relayed by the Queqiao satellite); Zhang et al. 2024, Nature, "Lunar farside volcanism 2.8 billion years ago from Chang'e-6 basalts" (2,807 and 4,203 million years; at least 1.4 billion years of volcanism); Zhou et al. 2025, Nature (samples returned 25 June 2024; landing site 41.6383 S, 153.9856 W); "A relatively cool lunar farside mantle inferred from Chang'e-6 basalts and remote sensing", Nature Geoscience 2025 (about 100 °C cooler). Libration, the seen fraction, the new moon and the Moon's place over La Palma: JPL Horizons, computed. Images: Moon: NASA/GSFC/Arizona State University (LRO, CGI Moon Kit). Chang'e 4 landing site: NASA/GSFC/Arizona State University (LROC NAC M1303521387LR, arrows removed). Earthrise: NASA (Apollo 8, AS08-14-2383). Earth: NASA Blue Marble. Stars: Hipparcos. Milky Way panorama: ESO/S. Brunier (CC BY 4.0). The orbit, Apollo 8 and relay sketches, the tidal stretch and the far-side ground are illustrations. #moon #space #astronomy