The Moon

The Moon
The Moon is the only natural satellite of the Earth, and the fifth largest satellite in the Solar System. It is the largest natural satellite of a planet in the Solar System relative to thesize of its primary, having 27 percent the diameter and 60 percent the density of Earth.
The Moon is the brightest object in the sky after the Sun, although its surface is actually very dark, witha reflectance similar to that of coal. Its prominence in the sky and its regular cycle of phases have, since ancient times, made the Moon an important cultural influenceon language, calendars, art and mythology. The Moon's gravitational influence produces the ocean tides and the minute lengthening of the day. 
The Moon is the only celestial body other than Earth on which humans have set foot.Etymology
The English proper name for Earth's natural satellite is "the Moon". The noun moon derives from moone (around 1380), which developed from mone (1135), which derives from OldEnglish mōna (dating from before 725), which, like all Germanic language cognates, ultimately stems from Proto-Germanic *mǣnōn.
The principal modern English adjective pertaining to the Moon is lunar, derived from theLatin Luna. Another less common adjective is selenic, derived from the Ancient Greek Selene (Σελήνη), from which the prefix "seleno-" (as in selenography) is derived.

Structure
The Moon is thesecond densest satellite in the Solar System after Io. However, the inner core of the Moon is small, with a radius of about 350 km or less; this is only ~20% percent the size of the Moon, in contrast tothe ~50% percent of most other terrestrial bodies. Its composition is not well constrained, but it is probably metallic iron alloyed with a small amount of sulphur and nickel; analyses of the Moon'stime-variable rotation indicate that it is at least partly molten.

La Luna
La Luna es el único satélite natural de la Tierra y el quinto más grande del Sistema Solar. Es el mayor satélite...