Apollo 8 in the context of Saturn V

The 20th century began on 1 January 1901 (MCMI), and ended on 31 December 2000 (MM). It was the 10th and last century in the 2nd millennium and was marked by new models of scientific understanding, unprecedented scopes of warfare, new modes of communication that would operate at nearly instant speeds, and new forms of art and entertainment. Population growth was also unprecedented, as the century started with around 1.6 billion people, and ended with around 6.2 billion.

The 20th century was dominated by significant geopolitical events that reshaped the political and social structure of the globe: World War I, the Spanish flu pandemic, World War II and the Cold War. Unprecedented advances in science and technology defined the century, including the advent of nuclear weapons and nuclear power, space exploration, the shift from analog to digital computing and the continuing advancement of transportation, including powered flight and the automobile. The Earth's sixth mass extinction event, the Holocene extinction, continued, and human conservation efforts increased.

As part of the Apollo program by NASA, 24 astronauts flew nine missions to the Moon between December 1968 and December 1972. During six successful two-man landing missions, twelve men walked on the lunar surface, six of whom drove Lunar Roving Vehicles as part of the last three missions. Three men have been to the Moon twice, one orbited once and took a circumlunar trajectory the second time, while the other two landed once apiece. Apart from these 24 men, no human being has gone beyond low Earth orbit. As of December 2025, five of the 24 remain alive. A number of non-human animals have circled or orbited it, including two tortoises, several turtles, and five mice.

Apollo missions 8 and 10–17 were the nine crewed missions to the Moon. Apollo 4–6 and AS-201 and AS-202 were uncrewed, while AS-203 is considered a test flight. The Apollo program included three other crewed missions: Apollo 1 (AS-204) did not launch and its crew died in a ground-based capsule fire, while Apollo 7 and Apollo 9 were low Earth orbit missions that tested spacecraft components and docking maneuvers. Apollo missions 18, 19, and 20 were canceled. Twelve astronauts later flew unused Apollo command modules in the Apollo Applications Program's Skylab and Apollo–Soyuz Test Project. Of the 24 astronauts who flew to the Moon, two went on to command a Skylab mission, one commanded Apollo–Soyuz, one flew as commander for Approach and Landing Tests of the Space Shuttle, and two commanded orbital Space Shuttle missions.

The Soviet crewed lunar programs were a series of programs pursued by the Soviet Union to land humans on the Moon, in competition with the United States Apollo program. The Soviet government publicly denied participating in such a competition, but secretly pursued two programs in the 1960s: crewed lunar flyby missions using Soyuz 7K-L1 (Zond) spacecraft launched with the Proton-K rocket, and a crewed lunar landing using Soyuz 7K-LOK and LK spacecraft launched with the N1 rocket. Following the dual American successes of the first crewed lunar orbit on 24–25 December 1968 (Apollo 8) and the first Moon landing on July 20, 1969 (Apollo 11), and a series of catastrophic N1 failures, both Soviet programs were eventually brought to an end. The Proton-based Zond program was canceled in 1970, and the N1-L3 program was de facto terminated in 1974 and officially canceled in 1976. Details of both Soviet programs were kept secret until 1990 when the government allowed them to be published under the policy of glasnost.

Soviet cosmonauts neither orbited nor landed on the Moon.

Common heritage of humanity is a principle of international law that holds the defined territorial areas and elements of humanity's common heritage (cultural and natural) should be held in trust for future generations and be protected from exploitation by individual nation states or corporations. Some possible examples include global communication between individuals over the internet and geostationary orbit over the high seas.

The far side of the Moon, also called the dark side of the Moon, is the hemisphere of the Moon that faces away from Earth; the opposite hemisphere being the near side. Due to tidal locking, the time it takes for the Moon to orbit the Earth once is equal to the time it takes for the Moon to rotate once, thus, the far side of the Moon never fully comes into view from Earth's surface. The far side has sometimes been called the "dark side of the Moon", where "dark" means "unseen" instead of "unilluminated" – despite a common misconception that the dark side of the Moon is so-called because it never receives light, each location on the Moon experiences two weeks of sunlight while the opposite location experiences night. The far side is actually more reflective than the near side, as it lacks the large areas of darker maria surface.

About 18 percent of the far side is occasionally visible from Earth due to oscillation and to libration. The remaining 82 percent remained unobserved until 1959, when it was photographed by the Soviet Luna 3 space probe. The Soviet Academy of Sciences published the first atlas of the far side in 1960. The Apollo 8 astronauts were the first humans to see the far side in person when they orbited the Moon in 1968. Compared to the near side, the far side's terrain is rugged, with a multitude of impact craters and relatively few flat and dark lunar maria ("seas"), giving it an appearance closer to other barren places in the Solar System such as Mercury and Callisto. It has one of the largest craters in the Solar System, the South Pole–Aitken basin.

Spaceship Earth (or Spacecraft Earth or Spaceship Planet Earth) is a worldview encouraging everyone on Earth to act as a harmonious crew working toward the greater good.

Earthrise is a photograph of Earth that was taken from lunar orbit by astronaut William Anders on December 24, 1968, during the Apollo 8 mission. Nature photographer Galen Rowell described it as "the most influential environmental photograph ever taken".

William Alison Anders (17 October 1933 – 7 June 2024) was an American United States Air Force (USAF) major general, electrical engineer, nuclear engineer, NASA astronaut, and businessman. In December 1968, he was a member of the crew of Apollo 8, the first three people to leave low-Earth orbit and travel to the Moon. Along with fellow astronauts Frank Borman and Jim Lovell, he circled the Moon ten times, and broadcast live images and commentary back to Earth, including the Christmas Eve Genesis reading. During one of the mission's lunar orbits, he took the iconic Earthrise photograph.

A 1955 graduate of the United States Naval Academy, Anders was commissioned a second lieutenant in the USAF the same year and became a fighter pilot flying Northrop F-89 Scorpions equipped with AIR-2A nuclear-tipped air-to-air rockets. In 1962, he earned a Master of Science degree in nuclear engineering at the Air Force Institute of Technology (AFIT) of Air University, and was sent to the Air Force Weapons Laboratory to manage the technical aspects of the service's nuclear reactor programs.

James Arthur Lovell Jr. (/ˈlʌvəl/ LUV-əl; March 25, 1928 – August 7, 2025) was an American astronaut, naval aviator, test pilot, and mechanical engineer. In 1968, as command module pilot of Apollo 8, he, along with Frank Borman and William Anders, became one of the first three astronauts to fly to and orbit the Moon. He then commanded the Apollo 13 lunar mission in 1970 which, after a critical failure en route, looped around the Moon and returned safely to Earth.

A 1952 graduate of the United States Naval Academy in Annapolis, Maryland, Lovell flew McDonnell F2H Banshee night fighters. He was deployed in the Western Pacific aboard the aircraft carrier USS Shangri-La. In January 1958, he entered a six-month test pilot training course at the Naval Air Test Center at Naval Air Station Patuxent River, Maryland, with Class 20 and graduated at the top of the class. He was then assigned to Electronics Test, working with radar, and in 1960 he became the Navy's McDonnell Douglas F-4 Phantom II program manager. In 1961, he became a flight instructor and safety engineering officer at Naval Air Station Oceana in Virginia Beach, Virginia, and completed Aviation Safety School at the University of Southern California.

Zond 6 was a formal member of the Soviet Zond program, and an unpiloted version of the Soyuz 7K-L1 crewed Moon-flyby spacecraft. It was launched on a lunar flyby mission on November 10, 1968, from a parent satellite (68-101B) in Earth parking orbit. The spacecraft carried a biological payload of turtles, flies, and bacteria. It also carried scientific probes including cosmic ray, micrometeoroid detectors, and photographic equipment.

The mission was a precursor to a crewed circumlunar flight which the Soviets hoped could occur in December 1968, thus beating the American Apollo 8. However, after rounding the Moon on November 14, Zond 6 crashed on its return to Earth, due to a parachute failure when the parachute was detached from the capsule too early.

Apollo 6 (April 4, 1968), also known as AS-502, was the third and final uncrewed flight in the United States' Apollo Program and the second test of the Saturn V launch vehicle. It qualified the Saturn V for use on crewed missions, and it was used beginning with Apollo 8 in December 1968.

Apollo 6 was intended to demonstrate the ability of the Saturn V's third stage, the S-IVB, to propel itself and the Apollo spacecraft to lunar distances. Its components began arriving at the Kennedy Space Center in early 1967. Testing proceeded slowly, often delayed by testing of the Saturn V intended for Apollo 4—the inaugural launch of the Saturn V. After that uncrewed mission launched in November 1967, there were fewer delays, but enough so that the flight was postponed from March to April 1968.

William Alison Anders (17 October 1933 – 7 June 2024) was a United States Air Force (USAF) major general, electrical engineer, nuclear engineer, NASA astronaut, and businessman. In December 1968, he was a member of the crew of Apollo 8, the first three people to leave low-Earth orbit and travel to the Moon. Along with fellow astronauts Frank Borman and Jim Lovell, he circled the Moon ten times, and broadcast live images and commentary back to Earth, including the Christmas Eve Genesis reading. During one of the mission's lunar orbits, he took the iconic Earthrise photograph.

A 1955 graduate of the United States Naval Academy, Anders was commissioned a second lieutenant in the USAF the same year and became a fighter pilot flying Northrop F-89 Scorpions equipped with AIR-2A nuclear-tipped air-to-air rockets. In 1962, he earned a Master of Science degree in nuclear engineering at the Air Force Institute of Technology (AFIT) of Air University, and was sent to the Air Force Weapons Laboratory to manage the technical aspects of the service's nuclear reactor programs.

Langrenus is an impact crater located near the eastern lunar limb. The feature is circular in shape, but appears oblong due to foreshortening. It lies on the eastern shore of the Mare Fecunditatis. To the south is the overlapping crater pair Vendelinus and the smaller Lamé.

The inner wall of Langrenus is wide and irregularly terraced, with an average width of about 20 kilometers. The outer ramparts are irregular and hilly, and there is a bright, fragmented ray system spread across the mare to the west. The interior of the crater has a higher albedo than the surroundings, so the crater appears bright when the Sun is overhead. The crater floor is covered by many boulders, and is slightly irregular in the northwest half. The central peaks rise about a kilometer above the floor, and a peak on the eastern rim ascends to an altitude of 3 km.