The Moon is Earth's only natural satellite, orbiting our planet at an average distance of 384,400 km (238,900 mi). It measures about a quarter of the diameter of the Earth and lacks any significant atmosphere, hydrosphere, or magnetic field. Its surface gravity is only about one-sixth of Earth's, however its gravitational influence on our planet is the main driver of Earth's tides. During the moon's orbital period, the amount of visible surface illuminated by the Sun varies from none up to 100%, resulting in a set of predictable lunar phases.
Both the Moon's prominence in the earthly sky and its regular cycle of phases have been a great influence for human societies throughout history.
Since prehistoric times, people have taken note of the Moon's phases, its waxing and waning, and used it to keep track of the passing years and to set schedules for hunting, planting, and harvesting. Below you can see Galileo's sketches of the phases of the moon, painted in 1609.
Tally sticks, notched bones dating as far back as 20–30,000 years ago, are believed by some to mark the phases of the Moon. The counting of the days between the Moon's phases gave rise to generalized time periods of the full lunar cycle as months, and possibly of its phases as weeks. The result of this is the word Moon, which is related to the word month and may be related to the verb "measure" (of time).
Other names attributed to our satellite that have had an impact on our current use of language are the latin word lūna, which evolved to be used as the English adjective lunar, as well as Selene, the Greek Moon goddess (pictured below).
The Moon's influences can be found in language, art, and mythology and are varied across those fields. Some such influences are the silvery color and attitude that it imparts on otherwise ordinary beings, or the way it “kneads the ocean and the sea” (Thomas Hardy). Or how it can incite a certain disposition towards spirituality, creativity and ritualistic magic.
Mythologically, the moon is the ruler of the juices of life, including sap, semen, menstrual blood, nectar and the ebb and flow of every body of water. This relationship with moisture as the medium for creation explains why lunar deities have historically been in charge of conception, pregnancy, and birth, as well as the agricultural cycles of reaping and sowing.
Here we see the Venus of Laussel, which was carved between 20,000 and 18,000 years ago holding a crescent shaped horn, the 13 notches on the horn may symbolize the number of days from menstruation to ovulation, or of menstrual cycles or moons per year.
So rich with meaning is the figure of the moon, that we can attribute very different aspects to each of its phases:
For example, the full moon is the Buddhist symbol for tranquility and perfect truth.
Ancient cultures the world over have given these full moons names based on the behavior of the plants, animals, or weather during that month.
The crescent moon is known to symbolize the eternal cycle of potential growth as well as its dangers and it has been used by many cultures to represent the Moon in writing systems.
In ancient Greece and Rome, girls were given crescent-shaped amulets on their birthday to protect them from evil spirits. Women also wore them to improve fertility and for protection during childbirth.
The crescent is usually associated with Islam and regarded as its symbol. The crescent and star symbol has its origins in Sumerian culture and after being used by multiple civilizations it became strongly associated with the Ottoman Empire in the 19th century. By extension from the use in Ottoman lands, It became a symbol also for Islam as a whole.