Moon

Moon decrescent symbol (bold)

Moon crescent symbol (bold)

FullMoon2010

Moon decrescent symbol (bold)

Far side of the Moon

Archean

Moon

The Moon is Earth's only natural satellite and the fifth-largest satellite in the Solar System. It is a prominent feature in the night sky and has significantly influenced human culture and society throughout history. The Moon is thought to have formed about 4.5 billion years ago, not long after the Earth. The prevailing hypothesis is that it was created from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

Formation and characteristics

The Moon's formation is believed to have occurred 4.5 billion years ago, shortly after the formation of the Solar System. The giant-impact hypothesis suggests that the Moon resulted from the collision of a Mars-sized body, Theia, with the early Earth. This impact would have been of sufficient magnitude to melt the impacting body and a significant portion of the Earth's crust, ejecting a large amount of debris into orbit around the Earth, which eventually coalesced to form the Moon.

The Moon's surface is marked by highlands, lowlands, and vast maria, which are large, dark, basaltic plains formed by ancient volcanic eruptions. It has a very thin atmosphere, known as an exosphere, which does not provide any significant protection from meteoroids and radiation.

Orbit and phases

The Moon orbits the Earth at an average distance of 384,400 kilometers (238,855 miles), completing a full orbit approximately every 27.3 days (a sidereal month). However, due to the Earth's movement around the Sun, it takes about 29.5 days (a synodic month) for the Moon to cycle through all its phases, from new Moon to full Moon and back to new Moon.

Influence on Earth

The Moon has a profound effect on Earth, most notably through its gravitational pull, which is the main driver of the Earth's tides. Its presence also helps stabilize the Earth's axial tilt, which contributes to a relatively stable climate over geological timescales.

Exploration

The Moon was the first celestial body to be visited by humans. The Apollo program, conducted by NASA in the late 1960s and early 1970s, successfully landed twelve astronauts on the Moon in a series of six manned missions, beginning with Apollo 11 in July 1969, when astronauts Neil Armstrong and Buzz Aldrin became the first humans to set foot on the Moon.

Since the Apollo missions, several unmanned spacecraft have been sent to the Moon by various space agencies, exploring its surface, seeking water, and conducting scientific experiments.

Cultural significance

The Moon has held a place of significant importance in human culture and religions throughout history. It has been a source of inspiration for art, literature, mythology, and folklore in many societies around the world. The lunar cycle has been used to mark time and is the basis for many of the world's calendars.

Future exploration

Interest in the Moon has been renewed in the 21st century, with several countries and private companies planning missions to explore, and potentially exploit, its resources. These missions aim to establish permanent human bases on the Moon as a stepping stone for future exploration of Mars and beyond.