We’re used to seeing the Moon wax and wane when we look up at the sky. But what did Apollo 11 astronauts see from the Moon when they looked back at the Earth? Find out how the lunar phases helped Apollo astronauts to land on the Moon.
Skylight: Apollo Mission Landings and Lunar Phases
[Sun sets, sky darkens. Pan from horizon to crescent Moon.]
[Text: For millennia, people watched in wonder as a bright orb in the sky cycled through its phases. In 1969 we paid it a visit.]
[Zoom into Moon.]
[Text: The same side of the Moon always faces Earth, regardless of its phase.]
[Text: The first people to view the far side of the Moon were the three Apollo 8 astronauts, in December 1968.]
[Flight over lunar landscape with sky in view. Earth appears over the horizon, getting higher in lunar sky.]
[Text: As they passed from the far side to the near side of the Moon, they were treated to the sight of Earth rising over the lunar horizon.]
[Text: Earth is always visible from anywhere on the near side of the Moon. It never sets.]
[Flying into close to lunar surface. Label: Sea of Tranquility, Apollo landing site. Craft on surface, labeled: Lunar module, Eagle.]
[Text: Apollo astronauts were only on the surface for 21 hours and 36 minutes.]
[Pan up, high into the sky, to Moon.]
[Text: Though the astronauts had little time for Earth-gazing, at the Apollo 11 site it is high in the sky.]
[Cut to lunar horizon of hills, with crescent Earth in the sky. As time runs, stars drift past a mostly stationary Earth. Earth phases change as is moves slightly in the sky.]
[Text: If they had stayed for a month, they would have seen the blue and white orb of Earth bobbing in the sky as it waxed and waned.]
[Text: Since Earth passes between Sun and Moon, it goes through phases, as seen from the Moon – just as the Moon goes through phases, as seen from Earth.]
[Earth goes through new phase as Sun passes behind it, then sets. Horizon darkens when Sun sets.]
[Text: The two worlds always have opposite phases, as one is viewed from the other.]
[Earth passes through full phase.]
[Text: For example, when the Moon is new, someone on the Moon would see a full Earth.]
[Horizon is again lit with sunlight.]
[Text: What phase was the Moon at the time of each landing?]
[Fade to view of near side of Moon in space. Time running fast to go from new Moon to crescent.]
[Text: The best visibility for lunar landings occurs soon after lunar sunrise.]
[Text: When the rising Sun is low on the horizon, the terrain casts long, detailed shadows, making navigation easier.]
[Text: The narrow range of requires lighting, with the Sun 5-14 degrees above the horizon, lasts less than 24 hours.]
[Text: Each Apollo landing had to occur soon after local sunrise.]
[Time stops at phase during Apollo 11 landing. Marker indicates location of site, near day-night line. Label: Apollo 11, July 20, 1969, 30% illuminated.]
[Fades to different phase, with site marked. Label: Apollo 12, November 19, 1969, 80% illuminated.]
[Fades to similar phase, with site marked. Label: Apollo 14, February 2, 1971, 79% illuminated.]
[Fades to different phase, with site marked. Label: Apollo 15, July 30, 1971, 51% illuminated.]
[Fades to similar phase, with site marked. Label: Apollo 16, April 20, 1972, 50% illuminated.]
[Fades to different phase, with site marked. Label: Apollo 17, December 11, 1972, 28% illuminated.]
[Text: Each landing site required a specific lunar phase.]
[Full Moon, all Apollo landing and sites marked and labels shown.]
[Fade to large image of crescent moon.]
[Text: The day-night boundary by which the lunar landings were timed is also a target for observers on Earth.]
[Text: Viewed through a telescope, the shadows along this boundary reveal the height and depth of mountains and craters.]
[Images of waxing Moon phases.]
[Text: When it's full, we have no shadows for contrast, but all other phases offer a detailed slice of the Moon’s near side…]
[Text: …enough detail to enjoy from a distance, and an intriguing invitation to visit again.]
[Credits roll]