July 6, 2022

The Moon is the only natural satellite of the Earth. Its proper name is sometimes used, par excellence and with a lowercase initial ("a moon"), as a synonym for satellite also for celestial bodies that orbit other planets. It orbits at an average distance of about 384400 km from the Earth, close enough to be observable with the naked eye, so that on its surface it is possible to distinguish dark spots and light spots. The former, called seas, are almost flat regions covered by basalt rocks and dark-colored debris. The clear lunar regions, called highlands or plateaus, are several kilometers high above the seas and have reliefs that are even 8000-9000 meters high. Being in synchronous rotation it always turns the same face towards the Earth and its hidden side remained unknown until the period of space exploration. During its orbital motion, the different aspect caused by the orientation with respect to the Sun generates clearly visible phases which have influenced man's behavior since ancient times. Impersonated by the Greeks as the goddess Selene, she was long ago regarded as influential on crops, famines and fertility. She conditions the life on Earth of many living species, regulating their reproductive cycle and hunting periods; she acts on the tides and on the stability of the earth's rotation axis. The Moon is thought to have formed 4.5 billion years ago, not long after the birth of the Earth. There are several theories regarding its formation; the most accredited is that it formed from the aggregation of debris left in orbit after the collision between the Earth and an object the size of Mars called Theia. Its astronomical symbol ☾ is a stylized representation of one of its phases (between the last quarter and the new moon seen from the northern hemisphere, or between the new moon and the first quarter seen from the southern hemisphere). The visible face of the Moon is characterized by the presence of about 300,000 impact craters (counting those with a diameter of at least 1 km). The largest lunar crater is the South Pole-Aitken basin, which has a diameter of about 2500 km, is 13 km deep and occupies the southern part of the hidden face.


The Italian term "Moon" (usually lowercase in common usage, not astronomical) comes from the Latin lūna, from an older * louksna, in turn coming from the Indo-European root leuk- meaning "light" or "reflected light" ; from the same root comes also the avestic raoxšna ("the brilliant"), and other forms in the Slavic languages, in Armenian and in Tocharian; semantic parallels can be found in the Sanskrit chandramā ("moon", considered as a deity) and in the ancient Greek σελήνη selḗnē (from σέλας sélas, "brilliance" [of fire], "splendor"), examples that retain the meaning of "shining ", although they are of different etymes. In the Germanic and Baltic languages ​​the name of the Moon derives from the Proto-Germanic * mēnōn, probably assimilated from the ancient Greek μήν and from the Latin mensis which derived from the common Indo-European root * me (n) ses, with the clear modern meaning of month. The Anglo-Saxon mōna probably derived from * mēnōn, later changed to mone around the twelfth century, then into today's moon. The current German term Mond is etymologically closely related to that of Monat (month) and refers to the period of its lunar phases, as well as in the Latvian mēness (moon) and mēnesis (month).

Observation of the Moon

In ancient times

In ancient times, cultures, mainly nomads, were not uncommon, who believed that the Moon died every night, descending into the world of shadows; other cultures thought that the moon chased the sun (or vice versa). In the time of Pythagoras, as the Pythagorean school stated, it was considered a planet. One of the first developments in astronomy was the