Portal:Moon

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The Moon Portal

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The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known.

The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, and thus always shows the same side to earth, the near side. The near side is marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. After the Sun, the Moon is the second-brightest regularly visible celestial object in Earth's sky. Its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day.

The Moon's average orbital distance is 384,402 km (238,856 mi), or 1.28 light-seconds. This is about thirty times the diameter of Earth. The Moon's apparent size in the sky is almost the same as that of the Sun (because it is 400x farther and larger). Therefore, the Moon covers the Sun nearly precisely during a total solar eclipse. This matching of apparent visual size will not continue in the far future, because the Moon's distance from Earth is slowly increasing.

The Moon was first reached in 1959 by an unmanned spacecraft of the Soviet Union's Luna program; the United States' NASA Apollo program achieved the only manned lunar missions to date, beginning with the first manned orbital mission by Apollo 8 in 1968, and six manned landings between 1969 and 1972, with the first being Apollo 11. These missions returned lunar rocks which have been used to develop a geological understanding of the Moon's origin, internal structure, and the Moon's later history. Since the Apollo 17 mission in 1972, the Moon has been visited only by unmanned spacecraft.

Both the Moon's natural prominence in the earthly sky and its regular cycle of phases as seen from Earth have provided cultural references and influences for human societies and cultures since time immemorial. Such cultural influences can be found in language, lunar based calendar systems, art, and mythology.

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Mission insignia of Apollo 11

The Apollo 11 space flight landed the first humans on Earth's Moon on July 20, 1969. The mission, carried out by the United States, is considered a major accomplishment in the history of exploration and represented a victory by the U.S. in the Cold War Space Race with the Soviet Union. Launched from Florida on July 16, the third lunar mission of NASA's Apollo program (and the only G-type mission) was crewed by Commander Neil Alden Armstrong, Command Module Pilot Michael Collins, and Lunar Module Pilot Edwin Eugene "Buzz" Aldrin, Jr. On July 20, Armstrong and Aldrin landed in the Sea of Tranquility and became the first humans to walk on the Moon. Their landing craft, Eagle, spent 21 hours and 31 minutes on the lunar surface while Collins orbited above in the command ship, Columbia. The three astronauts returned to Earth with 47.5 pounds (21.55 kilograms) of lunar rocks and landed in the Pacific Ocean on July 24. Apollo 11 fulfilled U.S. President John F. Kennedy's goal of reaching the moon before the Soviet Union by the end of the 1960s, which he had expressed during a 1961 mission statement before the United States Congress: "I believe that this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth."

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Labeled aerial photo of the Taurus-Littrow valley

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Wikinews Space portal
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  • July 14: Astronomers discover smallest known star
  • June 8: Astronomers reveal discovery of the hottest gas giant exoplanet known yet

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