Moon

The Moon is an astronomical body seen throughout the Fallout series.

Background
On July 16, 1969, a team of the United States Air Force in a Virgo II lunar lander named Valiant 11 landed on the Moon, the first Human beings to do so. On November 14 of that year, a Virgo III lander named Valiant 12 landed on the Moon, and left the former national flag of the United States on its surface before their departure.

In 2020, the Delta IX series of rockets were commissioned by the United States Space Administration, which underwent missions to the Moon, one of which was the 17-day Zeus 12. In 2052, the final manned mission to the Moon occurred, and during this, the flag left by the Valiant 12 was recovered and brought back to Earth, where it was put on display in Washington, D.C.'s Museum of Technology.

American forces are mentioned as having fought at the Sea of Tranquility, on the surface of the Moon, to secure the nation's freedom. Souvenir Moon rocks were openly sold on Earth.

Lunar phases
The phases of the Moon are the shape of the directly sunlit portion as viewed from Earth. The lunar phases gradually and cyclically change over time. In all first-person games, this is directly observable in the sky. A member of the Enlightened mentions several phases of the Moon, including gibbous, waning crescent, and new moon.

Fallout 4
There is no New Moon phase in Fallout 4, which has a 32 day lunar cycle. The Waning Crescent phase will shift to the Waxing Crescent instead of a New Moon phase. The Lunar Phases are 4 days between each other.

Appearances
The Moon is mentioned in Fallout, Fallout 3, Fallout: New Vegas, Fallout 4, Fallout 76.

Behind the scenes

 * In Fallout 2 developer commentary, the Garden of Eden Creation Kits were even able to fertilize the surface of the Moon, given the land had been appropriately pre-conditioned beforehand.
 * The location was mentioned in the design documents for the canceled Van Buren project.