<P> The Moon was first reached in 1959 by an unmanned spacecraft of the Soviet Union's Luna program; the United States' NASA Apollo program achieved the only manned lunar missions to date, beginning with the first manned orbital mission by Apollo 8 in 1968, and six manned landings between 1969 and 1972, with the first being Apollo 11 . These missions returned lunar rocks which have been used to develop a geological understanding of the Moon's origin, internal structure, and the Moon's later history . Since the Apollo 17 mission in 1972, the Moon has been visited only by unmanned spacecraft . </P> <P> Both the Moon's natural prominence in the earthly sky and its regular cycle of phases as seen from Earth have provided cultural references and influences for human societies and cultures since time immemorial . Such cultural influences can be found in language, lunar based calendar systems, art, and mythology . </P> <P> The usual English proper name for Earth's natural satellite is "the Moon", which in nonscientific texts is usually not capitalized . The noun moon is derived from Old English mōna, which (like all Germanic language cognates) stems from Proto - Germanic * mēnô, which comes from Proto - Indo - European * mḗh1n̥s "moon", "month", which comes from the Proto - Indo - European root * meh1 - "to measure", the month being the ancient unit of time measured by the Moon . Occasionally, the name "Luna" is used . In literature, especially science fiction, "Luna" is used to distinguish it from other moons, while in poetry, the name has been used to denote personification of our moon . </P> <P> The modern English adjective pertaining to the Moon is lunar, derived from the Latin word for the Moon, luna . The adjective selenic (usually only used to refer to the chemical element selenium) is so rarely used to refer to the Moon that this meaning is not recorded in most major dictionaries . It is derived from the Ancient Greek word for the Moon, σελήνη (selḗnē), from which is however also derived the prefix "seleno -", as in selenography, the study of the physical features of the Moon, as well as the element name selenium . Both the Greek goddess Selene and the Roman goddess Diana were alternatively called Cynthia . The names Luna, Cynthia, and Selene are reflected in terminology for lunar orbits in words such as apolune, pericynthion, and selenocentric . The name Diana comes from the Proto - Indo - European * diw - yo, "heavenly", which comes from the PIE root * dyeu - "to shine," which in many derivatives means "sky, heaven, and god" and is also the origin of Latin dies, "day". </P>

What is the name for earth's moon