The Moon is the only natural satellite of the Earth and the fifth largest satellite in the Solar System.

 

The Moon is the second densest satellite in the Solar System. 

 

It is the brightest object in the sky after the Sun, although its surface is actually very dark, with a similar resemblance to coal.

 

 

 

 

 

The Moon is the only celestial body on which humans have set foot. While the Soviet Union's Luna program, was the first to reach the Moon with unmanned spacecraft in 1959, the United States' NASA Apollo program achieved the only manned missions to date, beginning with the first manned lunar orbiting mission by Apollo 8 in 1968, and six manned lunar landings between 1969 and 1972, with the first being Apollo 11.

These missions returned over 380 kg of lunar rocks, which have been used to develop a detailed geological understanding of the Moon's origins (it is thought to have formed some 4.5 billion years ago in a giant impact event involving Earth).

The Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days.

 

However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show the same phase to Earth, which is about 29.5 days.undefined

The Moon is in synchronous rotation: it rotates about its axis in about the same time it takes to orbit the Earth. This results in it nearly always keeping the same face turned toward Earth.

 

 

The side of the Moon that faces Earth is called the near side, and the opposite side the far side.

 

The far side is often called the "dark side," but in fact, it is illuminated as often as the near side: once per lunar day, during the new Moon phase we observe on Earth when the near side is dark