Moon

Moon Moon symbol
FullMoon2010.jpg
Designations
Adjectives
Orbital characteristics
Epoch J2000
Perigee362600 km
(356400370400 km)
Apogee405400 km
(404000406700 km)
384399 km  (0.00257 AU)[1]
Eccentricity0.0549[1]
27.321661 d
(27 d 7 h 43 min 11.5 s[1])
29.530589 d
(29 d 12 h 44 min 2.9 s)
1.022 km/s
Inclination5.145° to the ecliptic[2][a]
Regressing by one revolution in 18.61 years
Progressing by one revolution in 8.85 years
Satellite ofEarth[b][3]
Physical characteristics
Mean radius
1737.1 km  (0.273 of Earth's)[1][4][5]
Equatorial radius
1738.1 km  (0.273 of Earth's)[4]
Polar radius
1736.0 km  (0.273 of Earth's)[4]
Flattening0.0012[4]
Circumference10921 km  (equatorial)
3.793×107 km2  (0.074 of Earth's)
Volume2.1958×1010 km3  (0.020 of Earth's)[4]
Mass7.342×1022 kg  (0.012300 of Earth's)[1][4] [6]
Mean density
3.344 g/cm3[1][4]
0.606 × Earth
1.62 m/s2  (0.1654 g)[4]
0.3929±0.0009[7]
2.38 km/s
27.321661 d  (synchronous)
Equatorial rotation velocity
4.627 m/s
North pole right ascension
  • 17h 47m 26s
  • 266.86°[9]
North pole declination
65.64°[9]
Albedo0.136[10]
Surface temp.minmeanmax
Equator100 K220 K390 K
85°N 150 K230 K[11]
29.3 to 34.1 arcminutes[4][d]
Atmosphere[12]
Surface pressure
  • 10−7 Pa (1 picobar)  (day)
  • 10−10 Pa (1 femtobar)   (night)[e]
Composition by volume

The Moon is an astronomical body that orbits planet Earth and is Earth's only permanent natural satellite. It is the fifth-largest natural satellite in the Solar System, and the largest among planetary satellites relative to the size of the planet that it orbits (its primary). The Moon is after Jupiter's satellite Io the second-densest satellite in the Solar System among those whose densities are known.

The Moon is thought to have formed about 4.51 billion years ago, not long after Earth. The most widely accepted explanation is that the Moon formed from the debris left over after a giant impact between Earth and a Mars-sized body called Theia.

The Moon is in synchronous rotation with Earth, and thus always shows the same side to Earth, the near side. The near side is marked by dark volcanic maria that fill the spaces between the bright ancient crustal highlands and the prominent impact craters. After the Sun, the Moon is the second-brightest regularly visible celestial object in Earth's sky. Its surface is actually dark, although compared to the night sky it appears very bright, with a reflectance just slightly higher than that of worn asphalt. Its gravitational influence produces the ocean tides, body tides, and the slight lengthening of the day.

The Moon's average orbital distance is 384,402 km (238,856 mi),[13][14] or 1.28 light-seconds. This is about thirty times the diameter of Earth. The Moon's apparent size in the sky is almost the same as that of the Sun, since the star is about 400 times the lunar distance and diameter. Therefore, the Moon covers the Sun nearly precisely during a total solar eclipse. This matching of apparent visual size will not continue in the far future because the Moon's distance from Earth is gradually increasing.

The Moon was first reached in September 1959 by the Soviet Union's Luna 2, an unmanned spacecraft. 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.

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 calendar systems, art, and mythology.

Name and etymology

The Moon, tinted reddish, during a lunar eclipse

The usual English proper name for Earth's natural satellite is "the Moon", which in nonscientific texts is usually not capitalized.[15][16][17][18][19] 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.[20][21] 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.[22]

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.[23][24][25] 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.[26][27] Both the Greek goddess Selene and the Roman goddess Diana were alternatively called Cynthia.[28] 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".

Other Languages
Адыгэбзэ: Мазэ
Afrikaans: Maan
Alemannisch: Mond
አማርኛ: ጨረቃ
Ænglisc: Mōna
Аҧсшәа: Амза
العربية: القمر
aragonés: Luna
ܐܪܡܝܐ: ܣܗܪܐ
armãneashti: Lunâ
arpetan: Lena
অসমীয়া: চন্দ্ৰ
asturianu: Lluna
Avañe'ẽ: Jasy
azərbaycanca: Ay
تۆرکجه: آی
বাংলা: চাঁদ
Bân-lâm-gú: Goe̍h-niû
башҡортса: Ай (юлдаш)
беларуская (тарашкевіца)‎: Месяц (спадарожнік)
भोजपुरी: चंद्रमा
български: Луна
Boarisch: Mond
བོད་ཡིག: ཟླ་བ།
brezhoneg: Loar
буряад: Һара
català: Lluna
čeština: Měsíc
corsu: Luna
Cymraeg: Lleuad
dansk: Månen
davvisámegiella: Mánnu
Deutsch: Mond
ދިވެހިބަސް: ހަނދު
Diné bizaad: Ooljééʼ
डोटेली: चन्द्रमा
eesti: Kuu
Ελληνικά: Σελήνη
emiliàn e rumagnòl: Lónna
español: Luna
Esperanto: Luno
estremeñu: Luna
euskara: Ilargia
فارسی: ماه
Fiji Hindi: Chandarma
føroyskt: Mánin
français: Lune
Fulfulde: Lewru
furlan: Lune
Gaeilge: An Ghealach
Gaelg: Yn Eayst
Gàidhlig: Gealach
galego: Lúa
ГӀалгӀай: Бутт (новкъар)
贛語: 月光
ગુજરાતી: ચંદ્ર
客家語/Hak-kâ-ngî: Ngie̍t-khiù
한국어:
Hausa: Wata
Hawaiʻi: Mahina
հայերեն: Լուսին
हिन्दी: चन्द्रमा
hornjoserbsce: Měsačk
hrvatski: Mjesec
Ido: Luno
Ilokano: Bulan
Bahasa Indonesia: Bulan
interlingua: Luna
Interlingue: Lune
ᐃᓄᒃᑎᑐᑦ/inuktitut: ᑕᖅᑭᖅ
isiZulu: Inyanga
íslenska: Tunglið
italiano: Luna
עברית: הירח
Basa Jawa: Rembulan
Kabɩyɛ: Fenaɣ
kalaallisut: Qaammat
ಕನ್ನಡ: ಚಂದ್ರ
Kapampangan: Bulan
ქართული: მთვარე
कॉशुर / کٲشُر: ज़ून
kaszëbsczi: Miesądz
қазақша: Ай (серік)
kernowek: Loor
Kiswahili: Mwezi
коми: Тӧлысь
Kreyòl ayisyen: Lalin
kurdî: Heyv
Кыргызча: Ай
Ladino: Luna
Latina: Luna
latviešu: Mēness
Lëtzebuergesch: Äerdmound
лезги: Варз
lietuvių: Mėnulis
Ligure: Lunn-a
Limburgs: Maon
Lingua Franca Nova: Luna
la .lojban.: lunra
lumbaart: Lüna
magyar: Hold
македонски: Месечина
Malagasy: Volana
മലയാളം: ചന്ദ്രൻ
Malti: Qamar
मराठी: चंद्र
მარგალური: თუთა (ალმაშარე)
مصرى: قمر
Bahasa Melayu: Bulan (satelit)
Mìng-dĕ̤ng-ngṳ̄: Nguŏk-giù
Mirandés: Luna
мокшень: Ков
монгол: Сар
မြန်မာဘာသာ: လ (ကမ္ဘာရံဂြိုဟ်)
Nāhuatl: Metztli
Dorerin Naoero: Maraman
Nederlands: Maan
Nedersaksies: Maone (eerde)
नेपाली: चन्द्रमा
नेपाल भाषा: तिमिला
日本語:
Napulitano: Luna
Nordfriisk: Moune
norsk: Månen
norsk nynorsk: Månen
Nouormand: Leune
Novial: Lune
ꆇꉙ:
occitan: Luna
ଓଡ଼ିଆ: ଜହ୍ନ
oʻzbekcha/ўзбекча: Oy
ਪੰਜਾਬੀ: ਚੰਦਰਮਾ
پنجابی: چن
پښتو: سپوږمۍ
Patois: Muun
Перем Коми: Тӧлісь
ភាសាខ្មែរ: ព្រះច័ន្ទ
Piemontèis: Lun-a
Plattdüütsch: Maand (Eer)
polski: Księżyc
Ποντιακά: Φέγγος
português: Lua
Qaraqalpaqsha: Ay
qırımtatarca: Ay (kök cismi)
Ripoarisch: Moond (Ääd)
română: Luna
rumantsch: Glina
Runa Simi: Killa
русиньскый: Місяць (сателіт)
русский: Луна
саха тыла: Ый
ᱥᱟᱱᱛᱟᱲᱤ: ᱧᱤᱫᱟᱹ ᱪᱟᱸᱫᱚ
संस्कृतम्: चन्द्रः
sardu: Luna
Scots: Muin
Seeltersk: Moune
shqip: Hëna
sicilianu: Luna
Simple English: Moon
سنڌي: چنڊ
slovenčina: Mesiac
slovenščina: Luna
словѣньскъ / ⰔⰎⰑⰂⰡⰐⰠⰔⰍⰟ: Мѣсѧць
ślůnski: Mjeśůnczek
Soomaaliga: Bil
کوردی: مانگ
српски / srpski: Месец
srpskohrvatski / српскохрватски: Mjesec
Basa Sunda: Bulan (satelit)
suomi: Kuu
svenska: Månen
தமிழ்: நிலா
Taqbaylit: Ayyur (itri)
татарча/tatarça: Ай (иярчен)
తెలుగు: చంద్రుడు
тоҷикӣ: Моҳтоб
Tsetsêhestâhese: Taa'é-eše'he
ತುಳು: ಚಂದ್ರೆ
Türkçe: Ay
Türkmençe: Aý (hemra)
тыва дыл: Ай
українська: Місяць (супутник)
اردو: چاند
Vahcuengh: Ronghndwen
vèneto: Łuna
vepsän kel’: Kudmaine
Tiếng Việt: Mặt Trăng
Volapük: Mun
Võro: Kuu
walon: Lune
文言:
West-Vlams: Moane
吴语: 月球
ייִדיש: לבנה
Yorùbá: Òṣùpá
粵語: 月光
Zeêuws: Maen (Aerde)
žemaitėška: Mienolis
中文: 月球