Videos

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]