Size and Distance: The Moon is the fifth-largest satellite in the solar system. It is approximately 1/6th the size of Earth and has a diameter of about 3,474 kilometers (2,159 miles). The average distance between the Moon and Earth is around 384,400 kilometers (238,855 miles).
Phases: The Moon goes through different phases due to its changing position relative to the Sun and Earth. These phases include the New Moon, Crescent, First Quarter, Gibbous, Full Moon, and back again. It takes about 29.5 Earth days to complete one full cycle of phases.
Synchronous Rotation: The Moon is in synchronous rotation with Earth, meaning it takes almost the same amount of time (about 27.3 Earth days) to complete one rotation on its axis as it takes to orbit the Earth.
Surface Features: The Moon’s surface is covered with craters, mountains, valleys, and “seas” called maria, which are actually large, flat plains formed by ancient volcanic activity. The most well-known feature on the Moon’s surface is the giant impact crater called the “Mare Imbrium.”
Lack of Atmosphere: Unlike Earth, the Moon has no atmosphere to retain heat or protect it from cosmic rays and meteoroids. This results in extreme temperature variations, ranging from about -173°C (-279°F) during the lunar night to about 127°C (260°F) during the lunar day.
Apollo Missions: The Moon has been the target of human exploration. The Apollo program by NASA successfully landed astronauts on the Moon between 1969 and 1972. Apollo 11, the first crewed mission, saw Neil Armstrong and Buzz Aldrin become the first humans to set foot on the lunar surface on July 20, 1969.
Tidal Locking: The Moon’s synchronous rotation with Earth is a result of tidal locking. The gravitational forces between Earth and the Moon caused the Moon to slow down its rotation until it became tidally locked to Earth.
Origin: The most widely accepted theory about the Moon’s origin is the Giant Impact Hypothesis. According to this theory, a Mars-sized body collided with the early Earth about 4.5 billion years ago, and the debris from this impact eventually formed the Moon.
Moonquakes: The Moon experiences moonquakes, which are similar to earthquakes on Earth. However, they are generally weaker because the Moon’s tectonic activity is not as active as Earth’s.
Lunar Landings: In addition to the Apollo missions, other countries have sent spacecraft to the Moon, including the Soviet Union’s Luna program, which achieved the first uncrewed Moon landing in 1959.